National Library of Energy BETA

Sample records for thermal conductivity measurements

  1. Thermal conductivity measurements of Summit polycrystalline silicon.

    SciTech Connect (OSTI)

    Clemens, Rebecca; Kuppers, Jaron D.; Phinney, Leslie Mary

    2006-11-01

    A capability for measuring the thermal conductivity of microelectromechanical systems (MEMS) materials using a steady state resistance technique was developed and used to measure the thermal conductivities of SUMMiT{trademark} V layers. Thermal conductivities were measured over two temperature ranges: 100K to 350K and 293K to 575K in order to generate two data sets. The steady state resistance technique uses surface micromachined bridge structures fabricated using the standard SUMMiT fabrication process. Electrical resistance and resistivity data are reported for poly1-poly2 laminate, poly2, poly3, and poly4 polysilicon structural layers in the SUMMiT process from 83K to 575K. Thermal conductivity measurements for these polysilicon layers demonstrate for the first time that the thermal conductivity is a function of the particular SUMMiT layer. Also, the poly2 layer has a different variation in thermal conductivity as the temperature is decreased than the poly1-poly2 laminate, poly3, and poly4 layers. As the temperature increases above room temperature, the difference in thermal conductivity between the layers decreases.

  2. Local measurement of thermal conductivity and diffusivity

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Hurley, David H.; Schley, Robert S.; Khafizov, Marat; Wendt, Brycen L.

    2015-12-01

    Simultaneous measurement of local thermal diffusivity and conductivity is demonstrated on a range of ceramic samples. This was accomplished by measuring the temperature field spatial profile of samples excited by an amplitude modulated continuous wave laser beam. A thin gold film is applied to the samples to ensure strong optical absorption and to establish a second boundary condition that introduces an expression containing the substrate thermal conductivity. The diffusivity and conductivity are obtained by comparing the measured phase profile of the temperature field to a continuum based model. A sensitivity analysis is used to identify the optimal film thickness formore » extracting the both substrate conductivity and diffusivity. Proof of principle studies were conducted on a range of samples having thermal properties that are representative of current and advanced accident tolerant nuclear fuels. It is shown that by including the Kapitza resistance as an additional fitting parameter, the measured conductivity and diffusivity of all the samples considered agree closely with literature values. Lastly, a distinguishing feature of this technique is that it does not require a priori knowledge of the optical spot size which greatly increases measurement reliability and reproducibility.« less

  3. Local measurement of thermal conductivity and diffusivity

    SciTech Connect (OSTI)

    Hurley, David H.; Schley, Robert S.; Khafizov, Marat; Wendt, Brycen L.

    2015-12-01

    Simultaneous measurement of local thermal diffusivity and conductivity is demonstrated on a range of ceramic samples. This was accomplished by measuring the temperature field spatial profile of samples excited by an amplitude modulated continuous wave laser beam. A thin gold film is applied to the samples to ensure strong optical absorption and to establish a second boundary condition that introduces an expression containing the substrate thermal conductivity. The diffusivity and conductivity are obtained by comparing the measured phase profile of the temperature field to a continuum based model. A sensitivity analysis is used to identify the optimal film thickness for extracting the both substrate conductivity and diffusivity. Proof of principle studies were conducted on a range of samples having thermal properties that are representative of current and advanced accident tolerant nuclear fuels. It is shown that by including the Kapitza resistance as an additional fitting parameter, the measured conductivity and diffusivity of all the samples considered agree closely with literature values. Lastly, a distinguishing feature of this technique is that it does not require a priori knowledge of the optical spot size which greatly increases measurement reliability and reproducibility.

  4. Local measurement of thermal conductivity and diffusivity

    SciTech Connect (OSTI)

    Hurley, David H.; Schley, Robert S.; Khafizov, Marat; Wendt, Brycen L.

    2015-12-15

    Simultaneous measurement of local thermal diffusivity and conductivity is demonstrated on a range of ceramic samples. This was accomplished by measuring the temperature field spatial profile of samples excited by an amplitude modulated continuous wave laser beam. A thin gold film is applied to the samples to ensure strong optical absorption and to establish a second boundary condition that introduces an expression containing the substrate thermal conductivity. The diffusivity and conductivity are obtained by comparing the measured phase profile of the temperature field to a continuum based model. A sensitivity analysis is used to identify the optimal film thickness for extracting the both substrate conductivity and diffusivity. Proof of principle studies were conducted on a range of samples having thermal properties that are representatives of current and advanced accident tolerant nuclear fuels. It is shown that by including the Kapitza resistance as an additional fitting parameter, the measured conductivity and diffusivity of all the samples considered agreed closely with the literature values. A distinguishing feature of this technique is that it does not require a priori knowledge of the optical spot size which greatly increases measurement reliability and reproducibility.

  5. Measurement of thermal conductivity in proton irradiated silicon

    SciTech Connect (OSTI)

    Marat Khafizov; Clarissa Yablinsky; Todd Allen; David Hurley

    2014-04-01

    We investigate the influence of proton irradiation on thermal conductivity in single crystal silicon. We apply laser based modulated thermoreflectance technique to extract the change in conductivity of the thin layer damaged by proton irradiation. Unlike time domain thermoreflectance techniques that require application of a metal film, we perform our measurement on uncoated samples. This provides greater sensitivity to the change in conductivity of the thin damaged layer. Using sample temperature as a parameter provides a means to deduce the primary defect structures that limit thermal transport. We find that under high temperature irradiation the degradation of thermal conductivity is caused primarily by extended defects.

  6. Hot wire thermal conductivity measurements in high temperature refractories

    SciTech Connect (OSTI)

    Dils, R.R.; Allen, J.D.; Richmond, J.C.; McNeil, M.B.

    1982-01-01

    In the hot wire thermal conductivity test, a wire embedded in the material to be tested is heated with constant power input, and the temperature is measured at short time intervals. The thermal conductivity is computed from the known power input to the wire and the measured rate of increase in the wire temperature after about 700 s of heating. A finite-difference computer simulation of the hot wire test was developed to evaluate the effects of several variables in the properties of the materials tested and in the test procedures on the measured thermal conductivity. Equations relating the radiant heat transfer in a material to its optical properties were developed and a radiant heat transfer component was developed for the finite-difference simulation. Equations were derived to compute the spectral optical properties of a test material from the measured spectral normal-hemispherical transmittance of a sample of the material of known thickness that is thin enough to have a measurable transmittance over the wavelength range of about 500 to 20,000 nm, and the spectral near-normal hemispherical reflectance of a sample of the material thick enough to be completely opaque, over the same wavelength range. The optical extinction coefficient, and the ratio of the scattering coefficient, to the absorption coefficient, of MinK 2000 and K3000 brick were evaluated from their measured spectral transmittances and reflectances, and used to compute the radiant heat transfer component in these materials. The hot wire test measures an average thermal conductivity for all directions away from the wire in a plane normal to the wire. Extensive tests were made of MinK 2000 and K3000, and the measured values are compared to the guarded hot plate thermal conductivity, which is unidirectional normal to the face of a brick. 67 references, 31 figures, 23 tables.

  7. Error and uncertainty in Raman thermal conductivity measurements

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Thomas Edwin Beechem; Yates, Luke; Graham, Samuel

    2015-04-22

    We investigated error and uncertainty in Raman thermal conductivity measurements via finite element based numerical simulation of two geometries often employed -- Joule-heating of a wire and laser-heating of a suspended wafer. Using this methodology, the accuracy and precision of the Raman-derived thermal conductivity are shown to depend on (1) assumptions within the analytical model used in the deduction of thermal conductivity, (2) uncertainty in the quantification of heat flux and temperature, and (3) the evolution of thermomechanical stress during testing. Apart from the influence of stress, errors of 5% coupled with uncertainties of ±15% are achievable for most materialsmore » under conditions typical of Raman thermometry experiments. Error can increase to >20%, however, for materials having highly temperature dependent thermal conductivities or, in some materials, when thermomechanical stress develops concurrent with the heating. A dimensionless parameter -- termed the Raman stress factor -- is derived to identify when stress effects will induce large levels of error. Together, the results compare the utility of Raman based conductivity measurements relative to more established techniques while at the same time identifying situations where its use is most efficacious.« less

  8. Error and uncertainty in Raman thermal conductivity measurements

    SciTech Connect (OSTI)

    Thomas Edwin Beechem; Yates, Luke; Graham, Samuel

    2015-04-22

    We investigated error and uncertainty in Raman thermal conductivity measurements via finite element based numerical simulation of two geometries often employed -- Joule-heating of a wire and laser-heating of a suspended wafer. Using this methodology, the accuracy and precision of the Raman-derived thermal conductivity are shown to depend on (1) assumptions within the analytical model used in the deduction of thermal conductivity, (2) uncertainty in the quantification of heat flux and temperature, and (3) the evolution of thermomechanical stress during testing. Apart from the influence of stress, errors of 5% coupled with uncertainties of ±15% are achievable for most materials under conditions typical of Raman thermometry experiments. Error can increase to >20%, however, for materials having highly temperature dependent thermal conductivities or, in some materials, when thermomechanical stress develops concurrent with the heating. A dimensionless parameter -- termed the Raman stress factor -- is derived to identify when stress effects will induce large levels of error. Together, the results compare the utility of Raman based conductivity measurements relative to more established techniques while at the same time identifying situations where its use is most efficacious.

  9. Comparative thermal conductivity measurements at Sandia National Laboratories. [Pyroceram

    SciTech Connect (OSTI)

    Sweet, J.N.; Roth, E.P.; Moss, M.; Haseman, G.M.; Anaya, J.A.

    1986-06-01

    A detailed examination has been made on the use of the comparative method for measuring the thermal conductivity of solid materials. Existing data analysis methods are discussed and new techniques, based on generalized linear least squares methods, are presented. An error analysis is made to determine the potential accuracy, reproducibility, and repeatability of the technique. For the case in which the reference conductivity is known to a relative accuracy of +-5%, the overall relative accuracy of the measurement is shown to be about +-6%. Experimental data are presented for the conductivities of commonly used reference materials; Pyrex 7740, Pyroceram 9606, Inconel 718, and Armco iron. Data are also given for two potential reference materials: fused silica and 304 stainless steel.

  10. Apparent thermal conductivity measurements by an unguarded technique

    SciTech Connect (OSTI)

    Graves, R.S.; Yarbrough, D.W.; McElroy, D.L.

    1983-01-01

    An unguarded longitudinal heat-flow apparatus for measuring the apparent thermal conductivity (lambda/sub a) of insulations was tested with mean specimen temperatures from 300 to 330/sup 0/K on samples up to 0.91 m wide, 1.52 m long, and 0.15 m thick. Heat flow is provided by a horizontal electrically heated Nichrome screen sandwiched between test samples that are bounded by temperature controlled copper plates and 9 cm of mineral fiber insulation. A determinate error analysis shows lambda/sub a/ measurement uncertainty to be less than +- 1.7% for insulating materials as thin as 3 cm. Three-dimensional thermal modeling indicates negligible error in lambda/sub a/ due to edge loss for insulations up to 7.62 cm thick when the temperature difference across the sample is measured at the sceen center. System repeatability and reproducibility were determined to be +- 0.2%. Differences of lambda/sub a/ results from the screen tester and results from the National Bureau of Standards were 0.1% for a 10-kg/m/sup 3/ Calibration Transfer Standard and 0.9% for 127-kg/m/sup 3/ fibrous glass board (SRM 1450b). Measurements on fiberglass and rock wool batt insulations showed the dependence of lambda/sub a/ on density, temperature, temperature difference, plate emittance, and heat flow direction. Results obtained for lambda/sub a/ as a function of density at 24/sup 0/C differed by less than 2% from values obtained with a guarded hot plate. These results demonstrate that this simple technique has the accuracy and sensitivity needed for useful lambda/sub a/ measurements on thermal insulating materials.

  11. Reexamination of Basal Plane Thermal Conductivity of Suspended Graphene Samples Measured by Electro-Thermal Micro-Bridge Methods

    SciTech Connect (OSTI)

    Jo, Insun; Pettes, Michael; Lindsay, Lucas R; Ou, Eric; Weathers, Annie; Moore, Arden; Yao, Zhen; Shi, Li

    2015-01-01

    Thermal transport in suspended graphene samples has been measured in prior works and this work with the use of a suspended electro-thermal micro-bridge method. These measurement results are analyzed here to evaluate and eliminate the errors caused by the extrinsic thermal contact resistance. It is noted that the thermal resistance measured in a recent work increases linearly with the suspended length of the single-layer graphene samples synthesized by chemical vapor deposition (CVD), and that such a feature does not reveal the failure of Fourier s law despite the increase in the apparent thermal conductivity with length. The re-analyzed thermal conductivity of a single-layer CVD graphene sample reaches about ( 1680 180 )Wm-1K-1 at room temperature, which is close to the highest value reported for highly oriented pyrolytic graphite. In comparison, the thermal conductivity values measured for two suspended exfoliated bi-layer graphene samples are about ( 880 60 ) and ( 730 60 ) Wm-1K-1 at room temperature, and approach that of the natural graphite source above room temperature. However, the low-temperature thermal conductivities of these suspended graphene samples are still considerably lower than the graphite values, with the peak thermal conductivities shifted to much higher temperatures. Analysis of the thermal conductivity data reveals that the low temperature behavior is dominated by phonon scattering by polymer residue instead of by the lateral boundary.

  12. Hot wire needle probe for in-reactor thermal conductivity measurement

    SciTech Connect (OSTI)

    JE Daw; JL Rempe; DL Knudson

    2012-08-01

    Thermal conductivity is a key property that must be known for proper design, test, and application of new fuels and structural materials in nuclear reactors. Thermal conductivity is highly dependent on the physical structure, chemical composition, and the state of the material. Typically, thermal conductivity changes that occur during irradiation are measured out-of-pile by Post Irradiated Examination (PIE) using a “cook and look” approach in hot-cells. Repeatedly removing samples from a test reactor to make out-of-pile measurements is expensive, has the potential to disturb phenomena of interest, and only provides understanding of the sample's end state at the time each measurement is made. There are also limited thermophysical property data for advanced fuels. Such data are needed for simulation design codes, the development of next generation reactors, and advanced fuels for existing nuclear plants. Being able to quickly characterize fuel thermal conductivity during irradiation can improve the fidelity of data, reduce costs of post-irradiation examinations, increase understanding of how fuels behave under irradiation, and confirm or improve existing thermal conductivity measurement techniques. This paper discusses recent efforts to develop and evaluate an in-pile thermal conductivity sensor based on a hot wire needle probe. Testing has been performed on samples with thermal conductivities ranging from 0.2 W/m-K to 22 W-m-K in temperatures ranging from 20 °C to 600 °C. Thermal conductivity values measured using the needle probe match data found in the literature to within 5% for samples tested at room temperature, 5.67% for low thermal conductivity samples tested at high temperatures, and 10% for high thermal conductivity samples tested at high temperatures. Experimental results also show that this sensor is capable of operating in various test conditions and of surviving long duration irradiations.

  13. Reexamination of Basal Plane Thermal Conductivity of Suspended Graphene Samples Measured by Electro-Thermal Micro-Bridge Methods

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Jo, Insun; Pettes, Michael; Lindsay, Lucas R.; Ou, Eric; Weathers, Annie; Moore, Arden; Yao, Zhen; Shi, Li

    2015-05-18

    Thermal transport in suspended graphene samples has been measured in prior works and this work with the use of a suspended electro-thermal micro-bridge method. These measurement results are analyzed here to evaluate and eliminate the errors caused by the extrinsic thermal contact resistance. It is noted that the thermal resistance measured in a recent work increases linearly with the suspended length of the single-layer graphene samples synthesized by chemical vapor deposition (CVD), and that such a feature does not reveal the failure of Fourier s law despite the increase in the apparent thermal conductivity with length. The re-analyzed thermal conductivitymore » of a single-layer CVD graphene sample reaches about ( 1680 180 )Wm-1K-1 at room temperature, which is close to the highest value reported for highly oriented pyrolytic graphite. In comparison, the thermal conductivity values measured for two suspended exfoliated bi-layer graphene samples are about ( 880 60 ) and ( 730 60 ) Wm-1K-1 at room temperature, and approach that of the natural graphite source above room temperature. However, the low-temperature thermal conductivities of these suspended graphene samples are still considerably lower than the graphite values, with the peak thermal conductivities shifted to much higher temperatures. Analysis of the thermal conductivity data reveals that the low temperature behavior is dominated by phonon scattering by polymer residue instead of by the lateral boundary.« less

  14. The thermal conductivity of rock under hydrothermal conditions: measurements and applications

    SciTech Connect (OSTI)

    Williams, Colin F.; Sass, John H.

    1996-01-24

    The thermal conductivities of most major rock-forming minerals vary with both temperature and confining pressure, leading to substantial changes in the thermal properties of some rocks at the high temperatures characteristic of geothermal systems. In areas with large geothermal gradients, the successful use of near-surface heat flow measurements to predict temperatures at depth depends upon accurate corrections for varying thermal conductivity. Previous measurements of the thermal conductivity of dry rock samples as a function of temperature were inadequate for porous rocks and susceptible to thermal cracking effects in nonporous rocks. We have developed an instrument for measuring the thermal conductivity of water-saturated rocks at temperatures from 20 to 350 °C and confining pressures up to 100 MPa. A transient line-source of heat is applied through a needle probe centered within the rock sample, which in turn is enclosed within a heated pressure vessel with independent controls on pore and confining pressure. Application of this technique to samples of Franciscan graywacke from The Geysers reveals a significant change in thermal conductivity with temperature. At reservoir-equivalent temperatures of 250 °C, the conductivity of the graywacke decreases by approximately 25% relative to the room temperature value. Where heat flow is constant with depth within the caprock overlying the reservoir, this reduction in conductivity with temperature leads to a corresponding increase in the geothermal gradient. Consequently, reservoir temperature are encountered at depths significantly shallower than those predicted by assuming a constant temperature gradient with depth. We have derived general equations for estimating the thermal conductivity of most metamorphic and igneous rocks and some sedimentary rocks at elevated temperature from knowledge of the room temperature thermal conductivity. Application of these equations to geothermal exploration should improve estimates

  15. Thermal Conductivity Measurements of Bulk Thermoelectric Materials (Prop. 2004-067)

    SciTech Connect (OSTI)

    Wang, Hsin; Porter, Wallace D; Sharp, J

    2006-01-01

    Thermal conductivity is an important material property of the bulk thermoelectrics. To improve ZT a reduced thermal conductivity is always desired. However, there is no standard material for thermoelectrics and the test results, even on the same material, often show significant scatter. The scatter in thermal conductivity made reported ZT values uncertain and sometime unrepeatable. One of the reasons for the uncertainty is due to the microstructure differences resulting from sintering, heat treatment and other processing parameters. They selected commonly used bulk thermoelectric materials and conducted thermal conductivity measurements using the laser flash diffusivity and differential scanning calorimeter (DSC) systems. Thermal conductivity was measured as a function of temperature of temperature from room temperature to 500 K and back to room temperature. The effect of thermal cycling on the bulk thermoelectric was studied. Comnbined with measurements on electrical resistivity and Seebeck coefficient, they show the use of a ZT map in selecting thermoelectrics. The commercial bulk material showed very good consistency and reliability compared to other bulk materials. The goal is to develop a thermal transport properties database for the bulk thermoelectrics and make the information available to the research community and industry.

  16. Differential heating: A versatile method for thermal conductivity measurements in high-energy-density matter

    SciTech Connect (OSTI)

    Ping, Y.; Fernandez-Panella, A.; Sio, H.; Correa, A.; Shepherd, R.; Landen, O.; London, R. A.; Sterne, P. A.; Whitley, H. D.; Fratanduono, D.; Boehly, T. R.; Collins, G. W.

    2015-09-04

    We propose a method for thermal conductivity measurements of high energy density matter based on differential heating. A temperature gradient is created either by surface heating of one material or at an interface between two materials by different energy deposition. The subsequent heat conduction across the temperature gradient is observed by various time-resolved probing techniques. Conceptual designs of such measurements using laser heating, proton heating, and x-ray heating are presented. As a result, the sensitivity of the measurements to thermal conductivity is confirmed by simulations.

  17. A robust and well shielded thermal conductivity device for low temperature measurements

    SciTech Connect (OSTI)

    Toews, W. H.; Hill, R. W.

    2014-04-15

    We present a compact mechanically robust thermal conductivity measurement apparatus for measurements at low temperatures (<1 K) and high magnetic fields on small high-purity single crystal samples. A high-conductivity copper box is used to enclose the sample and all the components. The box provides protection for the thermometers, heater, and most importantly the sample increasing the portability of the mount. In addition to physical protection, the copper box is also effective at shielding radio frequency electromagnetic interference and thermal radiation, which is essential for low temperature measurements. A printed circuit board in conjunction with a braided ribbon cable is used to organize the delicate wiring and provide mechanical robustness.

  18. Thermal conductivity measurements via time-domain thermoreflectance for the characterization of radiation induced damage

    SciTech Connect (OSTI)

    Cheaito, Ramez; Gorham, Caroline S.; Misra, Amit; Hattar, Khalid; Hopkins, Patrick E.

    2015-05-01

    The progressive build up of displacement damage and fission products inside different systems and components of a nuclear reactor can lead to significant defect formation, degradation, and damage of the constituent materials. This structural modification can highly influence the thermal transport mechanisms and various mechanical properties of solids. In this paper we demonstrate the use of time-domain thermoreflectance (TDTR), a non-destructive method capable of measuring the thermal transport in material systems from nano to bulk scales, to study the effect of radiation damage and the subsequent changes in the thermal properties of materials. We use TDTR to show that displacement damage from ion irradiation can significantly reduce the thermal conductivity of Optimized ZIRLO, a material used as fuel cladding in several current nuclear reactors. We find that the thermal conductivity of copper-niobium nanostructured multilayers does not change with helium ion irradiation doses of up to 1015 cm-2 and ion energy of 200 keV suggesting that these structures can be used and radiation tolerant materials in nuclear reactors. We compare the effect of ion doses and ion beam energies on the measured thermal conductivity of bulk silicon. Results demonstrate that TDTR thermal measurements can be used to quantify depth dependent damage.

  19. Thermal conductivity measurements via time-domain thermoreflectance for the characterization of radiation induced damage

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Cheaito, Ramez; Gorham, Caroline S.; Carnegie Mellon Univ., Pittsburgh, PA; Misra, Amit; Hattar, Khalid; Hopkins, Patrick E.

    2015-05-01

    The progressive build up of displacement damage and fission products inside different systems and components of a nuclear reactor can lead to significant defect formation, degradation, and damage of the constituent materials. This structural modification can highly influence the thermal transport mechanisms and various mechanical properties of solids. In this paper we demonstrate the use of time-domain thermoreflectance (TDTR), a non-destructive method capable of measuring the thermal transport in material systems from nano to bulk scales, to study the effect of radiation damage and the subsequent changes in the thermal properties of materials. We use TDTR to show that displacementmore » damage from ion irradiation can significantly reduce the thermal conductivity of Optimized ZIRLO, a material used as fuel cladding in several current nuclear reactors. We find that the thermal conductivity of copper-niobium nanostructured multilayers does not change with helium ion irradiation doses of up to 1015 cm-2 and ion energy of 200 keV suggesting that these structures can be used and radiation tolerant materials in nuclear reactors. We compare the effect of ion doses and ion beam energies on the measured thermal conductivity of bulk silicon. Results demonstrate that TDTR thermal measurements can be used to quantify depth dependent damage.« less

  20. Pump-probe measurements of the thermal conductivity tensor for materials lacking in-plane symmetry

    SciTech Connect (OSTI)

    Feser, Joseph P. [Department of Mechanical Engineering, University of Delaware, Newark, Delaware 19716 (United States); Liu, Jun; Cahill, David G. [Department of Materials Science and Engineering, and Frederick-Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801 (United States)

    2014-10-15

    We previously demonstrated an extension of time-domain thermoreflectance (TDTR) which utilizes offset pump and probe laser locations to measure in-plane thermal transport properties of multilayers. However, the technique was limited to systems of transversely isotropic materials studied using axisymmetric laser intensities. Here, we extend the mathematics so that data reduction can be performed on non-transversely isotropic systems. An analytic solution of the diffusion equation for an N-layer system is given, where each layer has a homogenous but otherwise arbitrary thermal conductivity tensor and the illuminating spots have arbitrary intensity profiles. As a demonstration, we use both TDTR and time-resolved magneto-optic Kerr effect measurements to obtain thermal conductivity tensor elements of <110> ?-SiO{sub 2}. We show that the out-of-phase beam offset sweep has full-width half-maxima that contains nearly independent sensitivity to the in-plane thermal conductivity corresponding to the scanning direction. Also, we demonstrate a Nb-V alloy as a low thermal conductivity TDTR transducer layer that helps improve the accuracy of in-plane measurements.

  1. Thermal conductivity of thermal-battery insulations

    SciTech Connect (OSTI)

    Guidotti, R.A.; Moss, M.

    1995-08-01

    The thermal conductivities of a variety of insulating materials used in thermal batteries were measured in atmospheres of argon and helium using several techniques. (Helium was used to simulate the hydrogen atmosphere that results when a Li(Si)/FeS{sub 2} thermal battery ages.) The guarded-hot-plate method was used with the Min-K insulation because of its extremely low thermal conductivity. For comparison purposes, the thermal conductivity of the Min-K insulating board was also measured using the hot-probe method. The thermal-comparator method was used for the rigid Fiberfrax board and Fiberfrax paper. The thermal conductivity of the paper was measured under several levels of compression to simulate the conditions of the insulating wrap used on the stack in a thermal battery. The results of preliminary thermal-characterization tests with several silica aerogel materials are also presented.

  2. Generalized Procedure for Improved Accuracy of Thermal Contact Resistance Measurements for Materials With Arbitrary Temperature-Dependent Thermal Conductivity

    SciTech Connect (OSTI)

    Sayer, Robert A.

    2014-06-26

    Thermal contact resistance (TCR) is most commonly measured using one-dimensional steady-state calorimetric techniques. In the experimental methods we utilized, a temperature gradient is applied across two contacting beams and the temperature drop at the interface is inferred from the temperature profiles of the rods that are measured at discrete points. During data analysis, thermal conductivity of the beams is typically taken to be an average value over the temperature range imposed during the experiment. Our generalized theory is presented and accounts for temperature-dependent changes in thermal conductivity. The procedure presented enables accurate measurement of TCR for contacting materials whose thermal conductivity is any arbitrary function of temperature. For example, it is shown that the standard technique yields TCR values that are about 15% below the actual value for two specific examples of copper and silicon contacts. Conversely, the generalized technique predicts TCR values that are within 1% of the actual value. The method is exact when thermal conductivity is known exactly and no other errors are introduced to the system.

  3. Generalized Procedure for Improved Accuracy of Thermal Contact Resistance Measurements for Materials With Arbitrary Temperature-Dependent Thermal Conductivity

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Sayer, Robert A.

    2014-06-26

    Thermal contact resistance (TCR) is most commonly measured using one-dimensional steady-state calorimetric techniques. In the experimental methods we utilized, a temperature gradient is applied across two contacting beams and the temperature drop at the interface is inferred from the temperature profiles of the rods that are measured at discrete points. During data analysis, thermal conductivity of the beams is typically taken to be an average value over the temperature range imposed during the experiment. Our generalized theory is presented and accounts for temperature-dependent changes in thermal conductivity. The procedure presented enables accurate measurement of TCR for contacting materials whose thermalmore » conductivity is any arbitrary function of temperature. For example, it is shown that the standard technique yields TCR values that are about 15% below the actual value for two specific examples of copper and silicon contacts. Conversely, the generalized technique predicts TCR values that are within 1% of the actual value. The method is exact when thermal conductivity is known exactly and no other errors are introduced to the system.« less

  4. Thermal Properties Capability Development Workshop Summary to Support the Implementation Plan for PIE Thermal Conductivity Measurements

    SciTech Connect (OSTI)

    Braase, Lori; Papesch, Cynthia; Hurley, David

    2015-04-01

    The Department of Energy (DOE)-Office of Nuclear Energy (NE), Idaho National Laboratory (INL), and associated nuclear fuels programs have invested heavily over the years in infrastructure and capability development. With the current domestic and international need to develop Accident Tolerant Fuels (ATF), increasing importance is being placed on understanding fuel performance in irradiated conditions and on the need to model and validate that performance to reduce uncertainty and licensing timeframes. INL’s Thermal Properties Capability Development Workshop was organized to identify the capability needed by the various nuclear programs and list the opportunities to meet those needs. In addition, by the end of fiscal year 2015, the decision will be made on the initial thermal properties instruments to populate the shielded cell in the Irradiated Materials Characterization Laboratory (IMCL).

  5. Measurement of the anisotropic thermal conductivity of molybdenum disulfide by the time-resolved magneto-optic Kerr effect

    SciTech Connect (OSTI)

    Liu, Jun Choi, Gyung-Min; Cahill, David G.

    2014-12-21

    We use pump-probe metrology based on the magneto-optic Kerr effect to measure the anisotropic thermal conductivity of (001)-oriented MoS{sub 2} crystals. A ?20?nm thick CoPt multilayer with perpendicular magnetization serves as the heater and thermometer in the experiment. The low thermal conductivity and small thickness of the CoPt transducer improve the sensitivity of the measurement to lateral heat flow in the MoS{sub 2} crystal. The thermal conductivity of MoS{sub 2} is highly anisotropic with basal-plane thermal conductivity varying between 85110 W?m{sup -1}?K{sup -1} as a function of laser spot size. The basal-plane thermal conductivity is a factor of ?50 larger than the c-axis thermal conductivity, 2.00.3?W?m{sup -1}?K{sup -1}.

  6. Hot filament technique for measuring the thermal conductivity of molten lithium fluoride

    SciTech Connect (OSTI)

    Jaworske, D.A.; Perry, W.D.

    1990-01-01

    Molten salts, such as lithium fluoride, are attractive candidates for thermal energy storage in solar dynamic space power systems because of their high latent heat of fusion. However, these same salts have poor thermal conductivities which inhibit the transfer of heat into the solid phase and out of the liquid phase. One concept for improving the thermal conductivity of the thermal energy storage system is to add a conductive filler material to the molten salt. High thermal conductivity pitch-based graphite fibers are being considered for this application. Although there is some information available on the thermal conductivity of lithium fluoride solid, there is very little information on lithium fluoride liquid, and no information on molten salt graphite fiber composites. This paper describes a hot filament technique for determining the thermal conductivity of molten salts. The hot filament technique was used to find the thermal conductivity of molten lithium fluoride at 930 C, and the thermal conductivity values ranged from 1.2 to 1.6 W/mK. These values are comparable to the slightly larger value of 5.0 W/mK for lithium fluoride solid. In addition, two molten salt graphite fiber composites were characterized with the hot filament technique and these results are also presented.

  7. Measurement of temperature-dependent thermal conductivity and viscosity of TiO{sub 2}-water nanofluids

    SciTech Connect (OSTI)

    Duangthongsuk, Weerapun; Wongwises, Somchai

    2009-04-15

    Nanofluid is an innovative heat transfer fluid with superior potential for enhancing the heat transfer performance of conventional fluids. Many attempts have been made to investigate its thermal conductivity and viscosity, which are important thermophysical properties. No definitive agreements have emerged, however, about these properties. This article reports the thermal conductivity and dynamic viscosity of nanofluids experimentally. TiO{sub 2} nanoparticles dispersed in water with volume concentration of 0.2-2 vol.% are used in the present study. A transient hot-wire apparatus is used for measuring the thermal conductivity of nanofluids whereas the Bohlin rotational rheometer (Malvern Instrument) is used to measure the viscosity of nanofluids. The data are collected for temperatures ranging from 15 C to 35 C. The results show that the measured viscosity and thermal conductivity of nanofluids increased as the particle concentrations increased and are higher than the values of the base liquids. Furthermore, thermal conductivity of nanofluids increased with increasing nanofluid temperatures and, conversely, the viscosity of nanofluids decreased with increasing temperature of nanofluids. Moreover, the measured thermal conductivity and viscosity of nanofluids are quite different from the predicted values from the existing correlations and the data reported by other researchers. Finally, new thermophysical correlations are proposed for predicting the thermal conductivity and viscosity of nanofluids. (author)

  8. Thermal conductance measurements of bolted copper joints for SuperCDMS

    SciTech Connect (OSTI)

    Schmitt, R.; Tatkowski, Greg; Ruschman, M.; Golwala, S. R.; Kellaris, N.; Daal, M.; Hall, Jeter C.; Hoppe, Eric W.

    2015-09-01

    Joint thermal conductance testing has been undertaken for bolted copper to copper connections from 60 mK to 26 K. This testing was performed to validate an initial design basis for the SuperCDMS experiment, where a dilution refrigerator will be coupled to a cryostat via multiple bolted connections. Copper used during testing was either gold plated or passivated with citric acid to prevent surface oxidation. Results obtained are well fit by a power law regression of joint thermal conductance to temperature and match well with data collected during a literature review.

  9. Thermal conductance measurements of bolted copper joints for SuperCDMS

    SciTech Connect (OSTI)

    Schmitt, R. L.; Tatkowski, G; Ruschman, M.; Golwala, S.; Kellaris, N.; Daal, M.; Hall, J.; Hoppe, E. W.

    2015-05-22

    Joint thermal conductance testing has been undertaken for bolted copper to copper connections from 60 mK to 26 K. This testing was performed to validate an initial design basis for the SuperCDMS experiment, where a dilution refrigerator will be coupled to a cryostat via multiple bolted connections. Copper used during testing was either gold plated or passivated with citric acid to prevent surface oxidation. Results obtained are well fit by a power law regression of joint thermal conductance to temperature and match well with data collected during a literature review.

  10. Thermal conductivity of semitransparent materials

    SciTech Connect (OSTI)

    Fine, H.A.; Jury, S.H.; McElroy, D.L.; Yarbrough, D.W.

    1981-01-01

    The three-region approximate solution for coupled conductive and radiative heat transfer and an exact solution for uncoupled conductive and radiative heat transfer in a grey semitransparent medium bounded by infinite parallel isothermal plates are employed to establish the dependence of the apparent thermal conductivity of semitransparent materials on other material properties and boundary conditions. An application of the analyses which uses apparent thermal conductivity versus density data to predict the dependence of apparent thermal conductivity on temperature is demonstrated. The predictions for seven sets of R-11 fiberglass and rock wool insulations agree with published measured values to within the limits of experimental error (+- 3%). Agreement for three sets of R-19 fiberglass insulations was, however, not good.

  11. Measurements of the apparent thermal conductivity of multi-layer insulation between 20 K and 90 K

    SciTech Connect (OSTI)

    Hurd, Joseph A.; Van Sciver, Steven W.

    2014-01-29

    NASA has the need to efficiently store cryogenic propellants in space for long periods of time. One method to improve storage efficiency is to use multi-layer insulation (MLI), a technique that minimizes the boiling rate due to radiation heat transfer. Typically, the thermal performance of MLI is determined by measuring the rate of evaporation of liquid nitrogen from a calibrated cryostat. The main limitation with this method is that testing conditions are restricted by the boiling temperature of the LN{sub 2}, which may not match the requirements of the application. The Multi-Layer Insulation Thermal Conductivity Experiment (MIKE) at the National High Magnetic Field Laboratory is capable of measuring the effective thermal conductivity of MLI at variable boundary temperatures. MIKE uses cryo-refrigerators to control boundary temperatures in the calorimeter and a calibrated thermal link to measure the heat load. To make the measurements requested by NASA, MIKE needed to be recalibrated for the 20 K to 90 K range. Also, due to the expectation of a lower heat transfer rate, the heat load support rod material was changed to one with a lower thermal conductivity to ensure the temperature difference seen on the cold rod could be measurable at the estimated heat load. Presented are the alterations to MIKE including calibration data and heat load measurements on new load-bearing MLI supplied by NASA.

  12. Thermal Conductivity Measurement of Xe-Implanted Uranium Dioxide Thick Films using Multilayer Laser Flash Analysis

    SciTech Connect (OSTI)

    Nelson, Andrew T.

    2012-08-30

    The Fuel Cycle Research and Development program's Advanced Fuels campaign is currently pursuing use of ion beam assisted deposition to produce uranium dioxide thick films containing xenon in various morphologies. To date, this technique has provided materials of interest for validation of predictive fuel performance codes and to provide insight into the behavior of xenon and other fission gasses under extreme conditions. In addition to the structural data provided by such thick films, it may be possible to couple these materials with multilayer laser flash analysis in order to measure the impact of xenon on thermal transport in uranium dioxide. A number of substrate materials (single crystal silicon carbide, molybdenum, and quartz) containing uranium dioxide films ranging from one to eight microns in thickness were evaluated using multilayer laser flash analysis in order to provide recommendations on the most promising substrates and geometries for further investigation. In general, the uranium dioxide films grown to date using ion beam assisted deposition were all found too thin for accurate measurement. Of the substrates tested, molybdenum performed the best and looks to be the best candidate for further development. Results obtained within this study suggest that the technique does possess the necessary resolution for measurement of uranium dioxide thick films, provided the films are grown in excess of fifty microns. This requirement is congruent with the material needs when viewed from a fundamental standpoint, as this length scale of material is required to adequately sample grain boundaries and possible second phases present in ceramic nuclear fuel.

  13. THERMAL CONDUCTIVITY ANALYSIS OF GASES

    DOE Patents [OSTI]

    Clark, W.J.

    1949-06-01

    This patent describes apparatus for the quantitative analysis of a gaseous mixture at subatmospheric pressure by measurement of its thermal conductivity. A heated wire forms one leg of a bridge circuit, while the gas under test is passed about the wire at a constant rate. The bridge unbalance will be a measure of the change in composition of the gas, if compensation is made for the effect due to gas pressure change. The apparatus provides a voltage varying with fluctuations of pressure in series with the indicating device placed across the bridge, to counterbalance the voltage change caused by fluctuations in the pressure of the gaseous mixture.

  14. Quick estimating for thermal conductivity

    SciTech Connect (OSTI)

    Sastri, S.R.S.; Rao, K.K. )

    1993-08-01

    Accurate values for thermal conductivity--an important engineering property used in heat transfer calculations of liquids--are not as readily available as those for other physical properties. Therefore, it often becomes necessary to use estimated data. A new estimating method combines ease of use with an accuracy that is generally better than existing procedures. The paper discusses how to select terms and testing correlations, then gives two examples of the use of the method for calculation of the thermal conductivity of propionic acid and chlorobenzene.

  15. Thermal conductivity of tubrostratic carbon nanofiber networks

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Bauer, Matthew L.; Saltonstall, Chris B.; Leseman, Zayd C.; Beechem, Thomas E.; Hopkins, Patrick E.; Norris, Pamela M.

    2016-01-01

    Composite material systems composed of a matrix of nano materials can achieve combinations of mechanical and thermophysical properties outside the range of traditional systems. While many reports have studied the intrinsic thermal properties of individual carbon fibers, to be useful in applications in which thermal stability is critical, an understanding of heat transport in composite materials is required. In this work, air/ carbon nano fiber networks are studied to elucidate the system parameters influencing thermal transport. Sample thermal properties are measured with varying initial carbon fiber fill fraction, environment pressure, loading pressure, and heat treatment temperature through a bidirectional modificationmore » of the 3ω technique. The nanostructures of the individual fibers are characterized with small angle x-ray scattering and Raman spectroscopy providing insight to individual fiber thermal conductivity. Measured thermal conductivity varied from 0.010 W/(m K) to 0.070 W/(m K). An understanding of the intrinsic properties of the individual fibers and the interactions of the two phase composite is used to reconcile low measured thermal conductivities with predictive modeling. This methodology can be more generally applied to a wide range of fiber composite materials and their applications.« less

  16. Thermal conductivity of tubrostratic carbon nanofiber networks

    SciTech Connect (OSTI)

    Bauer, Matthew L.; Saltonstall, Chris B.; Leseman, Zayd C.; Beechem, Thomas E.; Hopkins, Patrick E.; Norris, Pamela M.

    2016-01-01

    Composite material systems composed of a matrix of nano materials can achieve combinations of mechanical and thermophysical properties outside the range of traditional systems. While many reports have studied the intrinsic thermal properties of individual carbon fibers, to be useful in applications in which thermal stability is critical, an understanding of heat transport in composite materials is required. In this work, air/ carbon nano fiber networks are studied to elucidate the system parameters influencing thermal transport. Sample thermal properties are measured with varying initial carbon fiber fill fraction, environment pressure, loading pressure, and heat treatment temperature through a bidirectional modification of the 3ω technique. The nanostructures of the individual fibers are characterized with small angle x-ray scattering and Raman spectroscopy providing insight to individual fiber thermal conductivity. Measured thermal conductivity varied from 0.010 W/(m K) to 0.070 W/(m K). An understanding of the intrinsic properties of the individual fibers and the interactions of the two phase composite is used to reconcile low measured thermal conductivities with predictive modeling. This methodology can be more generally applied to a wide range of fiber composite materials and their applications.

  17. Thermal Properties Measurement Report

    SciTech Connect (OSTI)

    Carmack, Jon; Braase, Lori; Papesch, Cynthia; Hurley, David; Tonks, Michael; Zhang, Yongfeng; Gofryk, Krzysztof; Harp, Jason; Fielding, Randy; Knight, Collin; Meyer, Mitch

    2015-08-01

    The Thermal Properties Measurement Report summarizes the research, development, installation, and initial use of significant experimental thermal property characterization capabilities at the INL in FY 2015. These new capabilities were used to characterize a U3Si2 (candidate Accident Tolerant) fuel sample fabricated at the INL. The ability to perform measurements at various length scales is important and provides additional data that is not currently in the literature. However, the real value of the data will be in accomplishing a phenomenological understanding of the thermal conductivity in fuels and the ties to predictive modeling. Thus, the MARMOT advanced modeling and simulation capability was utilized to illustrate how the microstructural data can be modeled and compared with bulk characterization data. A scientific method was established for thermal property measurement capability on irradiated nuclear fuel samples, which will be installed in the Irradiated Material Characterization Laboratory (IMCL).

  18. A nanostructure thermal property measurement platform. (Conference...

    Office of Scientific and Technical Information (OSTI)

    side of the central heater), and this feature permits identification of possible changes in thermal conductance along the wire and measurement of the thermal contact resistance. ...

  19. Continuous Processing of High Thermal Conductivity Polyethylene...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Continuous Processing of High Thermal Conductivity Polyethylene Fibers and Sheets Massachusetts Institute of Technology (MIT) - Cambridge, MA A new, continuous manufacturing ...

  20. Controlling thermal conductance through quantum dot roughening...

    Office of Scientific and Technical Information (OSTI)

    Journal Article: Controlling thermal conductance through quantum dot roughening at interfaces. Citation Details ... Publication Date: 2011-01-01 OSTI Identifier: 1110382 Report ...

  1. Thermal conductance of metallic interface in vacuum

    SciTech Connect (OSTI)

    Mortazavi, P.; Shu, D.

    1985-01-01

    In most heat transfer applications, the deposited heat is transferred by any of the following classical methods: conduction, convection, radiation, or any combinations of these three. Depending on how critical the nature is of the designed equipment, the response time must be short enough in order to safeguard the proper performance of the devices. For instance, currently at the National Synchrotron Light Source (NSLS), various hardware equipment are being designed to intercept or to stop intense radiation beams induced by insertion devices such as wiggler and undulators. Due to the nature of some of these designs, the deposited high flux thermal load must be transferred across unbonded contact surfaces. Since any miscalculation would result in the disintegration of exposed material and therefore cause substantial problems, a true actual conductance measurement of the material in question is highly desirable. In the following three sections, background summary, the method of measurement, and the obtained results are discussed.

  2. Anisotropic thermal conductivity of thin polycrystalline oxide samples

    SciTech Connect (OSTI)

    Tiwari, A.; Boussois, K.; Nait-Ali, B.; Smith, D. S.; Blanchart, P.

    2013-11-15

    This paper reports about the development of a modified laser-flash technique and relation to measure the in-plane thermal diffusivity of thin polycrystalline oxide samples. Thermal conductivity is then calculated with the product of diffusivity, specific heat and density. Design and operating features for evaluating in-plane thermal conductivities are described. The technique is advantageous as thin samples are not glued together to measure in-plane thermal conductivities like earlier methods reported in literature. The approach was employed to study anisotropic thermal conductivity in alumina sheet, textured kaolin ceramics and montmorillonite. Since it is rare to find in-plane thermal conductivity values for such anisotropic thin samples in literature, this technique offers a useful variant to existing techniques.

  3. Electrical and thermal conductivities in dense plasmas

    SciTech Connect (OSTI)

    Faussurier, G. Blancard, C.; Combis, P.; Videau, L.

    2014-09-15

    Expressions for the electrical and thermal conductivities in dense plasmas are derived combining the Chester-Thellung-Kubo-Greenwood approach and the Kramers approximation. The infrared divergence is removed assuming a Drude-like behaviour. An analytical expression is obtained for the Lorenz number that interpolates between the cold solid-state and the hot plasma phases. An expression for the electrical resistivity is proposed using the Ziman-Evans formula, from which the thermal conductivity can be deduced using the analytical expression for the Lorenz number. The present method can be used to estimate electrical and thermal conductivities of mixtures. Comparisons with experiment and quantum molecular dynamics simulations are done.

  4. Increased thermal conductivity monolithic zeolite structures

    DOE Patents [OSTI]

    Klett, James; Klett, Lynn; Kaufman, Jonathan

    2008-11-25

    A monolith comprises a zeolite, a thermally conductive carbon, and a binder. The zeolite is included in the form of beads, pellets, powders and mixtures thereof. The thermally conductive carbon can be carbon nano-fibers, diamond or graphite which provide thermal conductivities in excess of about 100 W/mK to more than 1,000 W/mK. A method of preparing a zeolite monolith includes the steps of mixing a zeolite dispersion in an aqueous colloidal silica binder with a dispersion of carbon nano-fibers in water followed by dehydration and curing of the binder is given.

  5. THERMAL CONDUCTIVITY AND OTHER PROPERTIES OF CEMENTITIOUS GROUTS

    SciTech Connect (OSTI)

    ALLAN,M.

    1998-05-01

    The thermal conductivity and other properties cementitious grouts have been investigated in order to determine suitability of these materials for grouting vertical boreholes used with geothermal heat pumps. The roles of mix variables such as water/cement ratio, sand/cement ratio and superplasticizer dosage were measured. In addition to thermal conductivity, the cementitious grouts were also tested for bleeding, permeability, bond to HDPE pipe, shrinkage, coefficient of thermal expansion, exotherm, durability and environmental impact. This paper summarizes the results for selected grout mixes. Relatively high thermal conductivities were obtained and this leads to reduction in predicted bore length and installation costs. Improvements in shrinkage resistance and bonding were achieved.

  6. Gas storage carbon with enhanced thermal conductivity

    DOE Patents [OSTI]

    Burchell, Timothy D.; Rogers, Michael Ray; Judkins, Roddie R.

    2000-01-01

    A carbon fiber carbon matrix hybrid adsorbent monolith with enhanced thermal conductivity for storing and releasing gas through adsorption and desorption is disclosed. The heat of adsorption of the gas species being adsorbed is sufficiently large to cause hybrid monolith heating during adsorption and hybrid monolith cooling during desorption which significantly reduces the storage capacity of the hybrid monolith, or efficiency and economics of a gas separation process. The extent of this phenomenon depends, to a large extent, on the thermal conductivity of the adsorbent hybrid monolith. This invention is a hybrid version of a carbon fiber monolith, which offers significant enhancements to thermal conductivity and potential for improved gas separation and storage systems.

  7. Glass-like thermal conductivity in high efficiency thermoelectric...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    thermal conductivity in high efficiency thermoelectric materials Glass-like thermal conductivity in high efficiency thermoelectric materials Discusses strategies to design ...

  8. Thermal conductivity and diffusion-mediated localization in Fe1...

    Office of Scientific and Technical Information (OSTI)

    Journal Article: Thermal conductivity and diffusion-mediated localization in Fe1-xCrx alloys from first principles Citation Details In-Document Search Title: Thermal conductivity ...

  9. Los Alamos probes mysteries of uranium dioxide's thermal conductivity

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Mysteries of uranium dioxide's thermal conductivity Los Alamos probes mysteries of uranium dioxide's thermal conductivity New research is showing that the thermal conductivity of cubic uranium dioxide is strongly affected by interactions between phonons carrying heat and magnetic spins. August 4, 2014 Illustration of anisotropic thermal conductivity in uranium dioxide (UO2). Scientists are studying the thermal conductivity related to the material's different crystallographic directions, hoping

  10. Effective thermal conductivity in thermoelectric materials

    SciTech Connect (OSTI)

    Baranowski, LL; Snyder, GJ; Toberer, ES

    2013-05-28

    Thermoelectric generators (TEGs) are solid state heat engines that generate electricity from a temperature gradient. Optimizing these devices for maximum power production can be difficult due to the many heat transport mechanisms occurring simultaneously within the TEG. In this paper, we develop a model for heat transport in thermoelectric materials in which an "effective thermal conductivity" (kappa(eff)) encompasses both the one dimensional steady-state Fourier conduction and the heat generation/consumption due to secondary thermoelectric effects. This model is especially powerful in that the value of kappa(eff) does not depend upon the operating conditions of the TEG but rather on the transport properties of the TE materials themselves. We analyze a variety of thermoelectric materials and generator designs using this concept and demonstrate that kappa(eff) predicts the heat fluxes within these devices to 5% of the exact value. (C) 2013 AIP Publishing LLC.

  11. Hydraulic Conductivity Measurements Barrow 2014

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    Katie McKnight; Tim Kneafsey; Craig Ulrich; Jil Geller

    2015-02-22

    Six individual ice cores were collected from Barrow Environmental Observatory in Barrow, Alaska, in May of 2013 as part of the Next Generation Ecosystem Experiment (NGEE). Each core was drilled from a different location at varying depths. A few days after drilling, the cores were stored in coolers packed with dry ice and flown to Lawrence Berkeley National Laboratory (LBNL) in Berkeley, CA. 3-dimensional images of the cores were constructed using a medical X-ray computed tomography (CT) scanner at 120kV. Hydraulic conductivity samples were extracted from these cores at LBNL Richmond Field Station in Richmond, CA, in February 2014 by cutting 5 to 8 inch segments using a chop saw. Samples were packed individually and stored at freezing temperatures to minimize any changes in structure or loss of ice content prior to analysis. Hydraulic conductivity was determined through falling head tests using a permeameter [ELE International, Model #: K-770B]. After approximately 12 hours of thaw, initial falling head tests were performed. Two to four measurements were collected on each sample and collection stopped when the applied head load exceeded 25% change from the original load. Analyses were performed between 2 to 3 times for each sample. The final hydraulic conductivity calculations were computed using methodology of Das et al., 1985.

  12. Hydraulic Conductivity Measurements Barrow 2014

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    Katie McKnight; Tim Kneafsey; Craig Ulrich; Jil Geller

    Six individual ice cores were collected from Barrow Environmental Observatory in Barrow, Alaska, in May of 2013 as part of the Next Generation Ecosystem Experiment (NGEE). Each core was drilled from a different location at varying depths. A few days after drilling, the cores were stored in coolers packed with dry ice and flown to Lawrence Berkeley National Laboratory (LBNL) in Berkeley, CA. 3-dimensional images of the cores were constructed using a medical X-ray computed tomography (CT) scanner at 120kV. Hydraulic conductivity samples were extracted from these cores at LBNL Richmond Field Station in Richmond, CA, in February 2014 by cutting 5 to 8 inch segments using a chop saw. Samples were packed individually and stored at freezing temperatures to minimize any changes in structure or loss of ice content prior to analysis. Hydraulic conductivity was determined through falling head tests using a permeameter [ELE International, Model #: K-770B]. After approximately 12 hours of thaw, initial falling head tests were performed. Two to four measurements were collected on each sample and collection stopped when the applied head load exceeded 25% change from the original load. Analyses were performed between 2 to 3 times for each sample. The final hydraulic conductivity calculations were computed using methodology of Das et al., 1985.

  13. T I ENHANCING THERMAL CONDUCTIVITY OF FLUIDS WITH NANOPARTICLES...

    Office of Scientific and Technical Information (OSTI)

    JAM 1 1 1935 b T I ENHANCING THERMAL CONDUCTIVITY OF FLUIDS WITH NANOPARTICLES* Stephen U. ... THERMAL CONDUCTIVITY OF FLUIDS WITH NANOPARTICLES Stephen U. S. Choi 1 and Jeffrey A. ...

  14. T I ENHANCING THERMAL CONDUCTIVITY OF FLUIDS WITH NANOPARTICLES...

    Office of Scientific and Technical Information (OSTI)

    ... particles have been conducted since Maxwell's theoretical work was published more than ... Maxwell's model shows that the effective thermal conductivity of suspensions that contain ...

  15. Experimental and numerical study of the effective thermal conductivity...

    Office of Scientific and Technical Information (OSTI)

    to describe interface resistance of particles in modern TIMs, aka particulate composites. ... Country of Publication: United States Language: English Subject: Thermal Conductivity; ...

  16. Abnormal thermal conductivity in tetragonal tungsten bronze Ba...

    Office of Scientific and Technical Information (OSTI)

    temperature interval. Substitution of Sr for Ba brings about a significant decrease in thermal conductivity at x???3 accompanied by development of a low-temperature...

  17. Continuous Processing of High Thermal Conductivity Polyethylene Fibers and Sheets

    Broader source: Energy.gov [DOE]

    Project to develop and validate a continuous manufacturing process for polyethylene fibers and sheets yielding a thermal conductivity value greater than 60 W/m.K.

  18. First-principles prediction of phononic thermal conductivity...

    Office of Scientific and Technical Information (OSTI)

    There has been great interest in two-dimensional materials, beyond graphene, for both ... SILICENE; THERMAL CONDUCTIVITY; TRANSPORT THEORY; TWO-DIMENSIONAL SYSTEMS; VISIBLE ...

  19. Glass-like thermal conductivity in high efficiency thermoelectric materials

    Broader source: Energy.gov [DOE]

    Discusses strategies to design thermoelectric materials with extremely low lattice thermal conductivity through modifications of the phonon band structure and phonon relaxation time.

  20. Electrical and thermal conductivity of low temperature CVD graphene...

    Office of Scientific and Technical Information (OSTI)

    temperature CVD graphene: the effect of disorder Citation Details In-Document Search Title: Electrical and thermal conductivity of low temperature CVD graphene: the effect of ...

  1. High thermal conductivity lossy dielectric using co-densified...

    Office of Scientific and Technical Information (OSTI)

    Title: High thermal conductivity lossy dielectric using co-densified multilayer configuration Systems and methods are described for loss dielectrics. A method of manufacturing a ...

  2. Specific heat and thermal conductivity of explosives, mixtures...

    Office of Scientific and Technical Information (OSTI)

    Specific heat and thermal conductivity of explosives, mixtures, and plastic-bonded explosives determined experimentally Baytos, J.F. 45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL...

  3. Continuous Processing of High Thermal Conductivity Polyethylene...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    conductivity polyethylene fibers and sheets will be developed to replace metals and ceramics in heat-transfer devices. Project innovations include using massively parallel...

  4. Hot wire needle probe for thermal conductivity detection

    SciTech Connect (OSTI)

    Condie, Keith Glenn; Rempe, Joy Lynn; Knudson, Darrell lee; Daw, Joshua Earl; Wilkins, Steven Curtis; Fox, Brandon S.; Heng, Ban

    2015-11-10

    An apparatus comprising a needle probe comprising a sheath, a heating element, a temperature sensor, and electrical insulation that allows thermal conductivity to be measured in extreme environments, such as in high-temperature irradiation testing. The heating element is contained within the sheath and is electrically conductive. In an embodiment, the heating element is a wire capable of being joule heated when an electrical current is applied. The temperature sensor is contained within the sheath, electrically insulated from the heating element and the sheath. The electrical insulation electrically insulates the sheath, heating element and temperature sensor. The electrical insulation fills the sheath having electrical resistance capable of preventing electrical conduction between the sheath, heating element, and temperature sensor. The control system is connected to the heating element and the temperature sensor.

  5. Calibration-free electrical conductivity measurements for highly conductive slags

    SciTech Connect (OSTI)

    MACDONALD,CHRISTOPHER J.; GAO,HUANG; PAL,UDAY B.; VAN DEN AVYLE,JAMES A.; MELGAARD,DAVID K.

    2000-05-01

    This research involves the measurement of the electrical conductivity (K) for the ESR (electroslag remelting) slag (60 wt.% CaF{sub 2} - 20 wt.% CaO - 20 wt.% Al{sub 2}O{sub 3}) used in the decontamination of radioactive stainless steel. The electrical conductivity is measured with an improved high-accuracy-height-differential technique that requires no calibration. This method consists of making continuous AC impedance measurements over several successive depth increments of the coaxial cylindrical electrodes in the ESR slag. The electrical conductivity is then calculated from the slope of the plot of inverse impedance versus the depth of the electrodes in the slag. The improvements on the existing technique include an increased electrochemical cell geometry and the capability of measuring high precision depth increments and the associated impedances. These improvements allow this technique to be used for measuring the electrical conductivity of highly conductive slags such as the ESR slag. The volatilization rate and the volatile species of the ESR slag measured through thermogravimetric (TG) and mass spectroscopy analysis, respectively, reveal that the ESR slag composition essentially remains the same throughout the electrical conductivity experiments.

  6. Contributions of anharmonic phonon interactions to thermal boundary conductance.

    SciTech Connect (OSTI)

    Hopkins, Patrick E.; Norris, Pamela M.; Duda, John C.

    2010-05-01

    Continued reduction of characteristic dimensions in nanosystems has given rise to increasing importance of material interfaces on the overall system performance. With regard to thermal transport, this increases the need for a better fundamental understanding of the processes affecting interfacial thermal transport, as characterized by the thermal boundary conductance. When thermal boundary conductance is driven by phononic scattering events, accurate predictions of interfacial transport must account for anharmonic phononic coupling as this affects the thermal transmission. In this paper, a new model for phononic thermal boundary conductance is developed that takes into account anharonic coupling, or inelastic scattering events, at the interface between two materials. Previous models for thermal boundary conductance are first reviewed, including the Diffuse Mismatch Model, which only consdiers elastic phonon scattering events, and earlier attempts to account for inelastic phonon scattering, namely, the Maximum Transmission Model and the Higher Harmonic Inelastic model. A new model is derived, the Anharmonic Inelastic Model, which provides a more physical consideration of the effects of inelastic scattering on thermal boundary conductance. This is accomplished by considering specific ranges of phonon frequency interactions and phonon number density conservation. Thus, this model considers the contributions of anharmonic, inelastically scattered phonons to thermal boundary conductance. This new Anharmonic Inelastic Model shows excellent agreement between model predictions and experimental data at the Pb/diamond interface due to its ability to account for the temperature dependent changing phonon population in diamond, which can couple anharmonically with multiple phonons in Pb.

  7. Thermomechanical measurements on thermal microactuators. (Technical...

    Office of Scientific and Technical Information (OSTI)

    Thermal and mechanical measurements for the bent-beam polycrystalline silicon thermal ... SANDIA NATIONAL LABORATORIES; SILICON; VALIDATION Microactuators.; Ceramic ...

  8. Method for determining thermal conductivity and thermal capacity per unit volume of earth in situ

    DOE Patents [OSTI]

    Poppendiek, Heinz F.

    1982-01-01

    A method for determining the thermal conductivity of the earth in situ is based upon a cylindrical probe (10) having a thermopile (16) for measuring the temperature gradient between sets of thermocouple junctions (18 and 20) of the probe after it has been positioned in a borehole and has reached thermal equilibrium with its surroundings, and having means (14) for heating one set of thermocouple junctions (20) of the probe at a constant rate while the temperature gradient of the probe is recorded as a rise in temperature over several hours (more than about 3 hours). A fluid annulus thermally couples the probe to the surrounding earth. The recorded temperature curves are related to the earth's thermal conductivity, k.sub..infin., and to the thermal capacity per unit volume, (.gamma.c.sub.p).sub..infin., by comparison with calculated curves using estimates of k.sub..infin. and (.gamma.c.sub.p).sub..infin. in an equation which relates these parameters to a rise in the earth's temperature for a known and constant heating rate.

  9. High Thermal Conductivity of a Hydrogenated Amorphous Silicon Film

    SciTech Connect (OSTI)

    Liu, X.; Feldman, J. L.; Cahill, D. G.; Crandall, R. S.; Bernstein, N.; Photiadis, D. M.; Mehl, M. J.; Papaconstantopoulos, D. A.

    2009-01-23

    We measured the thermal conductivity {kappa} of an 80 {micro}m thick hydrogenated amorphous silicon film prepared by hot-wire chemical-vapor deposition with the 3{omega} (80-300 K) and the time-domain thermoreflectance (300 K) methods. The {kappa} is higher than any of the previous temperature dependent measurements and shows a strong phonon mean free path dependence. We also applied a Kubo based theory using a tight-binding method on three 1000 atom continuous random network models. The theory gives higher {kappa} for more ordered models, but not high enough to explain our results, even after extrapolating to lower frequencies with a Boltzmann approach. Our results show that this material is more ordered than any amorphous silicon previously studied.

  10. Voltage tunability of thermal conductivity in ferroelectric materials

    DOE Patents [OSTI]

    Ihlefeld, Jon; Hopkins, Patrick Edward

    2016-02-09

    A method to control thermal energy transport uses mobile coherent interfaces in nanoscale ferroelectric films to scatter phonons. The thermal conductivity can be actively tuned, simply by applying an electrical potential across the ferroelectric material and thereby altering the density of these coherent boundaries to directly impact thermal transport at room temperature and above. The invention eliminates the necessity of using moving components or poor efficiency methods to control heat transfer, enabling a means of thermal energy control at the micro- and nano-scales.

  11. Process for fabricating composite material having high thermal conductivity

    DOE Patents [OSTI]

    Colella, Nicholas J.; Davidson, Howard L.; Kerns, John A.; Makowiecki, Daniel M.

    2001-01-01

    A process for fabricating a composite material such as that having high thermal conductivity and having specific application as a heat sink or heat spreader for high density integrated circuits. The composite material produced by this process has a thermal conductivity between that of diamond and copper, and basically consists of coated diamond particles dispersed in a high conductivity metal, such as copper. The composite material can be fabricated in small or relatively large sizes using inexpensive materials. The process basically consists, for example, of sputter coating diamond powder with several elements, including a carbide forming element and a brazeable material, compacting them into a porous body, and infiltrating the porous body with a suitable braze material, such as copper-silver alloy, thereby producing a dense diamond-copper composite material with a thermal conductivity comparable to synthetic diamond films at a fraction of the cost.

  12. Thermal conductivity of vertically aligned carbon nanotube arrays: Growth conditions and tube inhomogeneity

    SciTech Connect (OSTI)

    Bauer, Matthew L.; Pham, Quang N.; Saltonstall, Christopher B.; Norris, Pamela M.

    2014-10-13

    The thermal conductivity of vertically aligned carbon nanotube arrays (VACNTAs) grown on silicon dioxide substrates via chemical vapor deposition is measured using a 3ω technique. For each sample, the VACNTA layer and substrate are pressed to a heating line at varying pressures to extract the sample's thermophysical properties. The nanotubes' structure is observed via transmission electron microscopy and Raman spectroscopy. The presence of hydrogen and water vapor in the fabrication process is tuned to observe the effect on measured thermal properties. The presence of iron catalyst particles within the individual nanotubes prevents the array from achieving the overall thermal conductivity anticipated based on reported measurements of individual nanotubes and the packing density.

  13. Thermal conductivity of III-V semiconductor superlattices

    SciTech Connect (OSTI)

    Mei, S. Knezevic, I.

    2015-11-07

    This paper presents a semiclassical model for the anisotropic thermal transport in III-V semiconductor superlattices (SLs). An effective interface rms roughness is the only adjustable parameter. Thermal transport inside a layer is described by the Boltzmann transport equation in the relaxation time approximation and is affected by the relevant scattering mechanisms (three-phonon, mass-difference, and dopant and electron scattering of phonons), as well as by diffuse scattering from the interfaces captured via an effective interface scattering rate. The in-plane thermal conductivity is obtained from the layer conductivities connected in parallel. The cross-plane thermal conductivity is calculated from the layer thermal conductivities in series with one another and with thermal boundary resistances (TBRs) associated with each interface; the TBRs dominate cross-plane transport. The TBR of each interface is calculated from the transmission coefficient obtained by interpolating between the acoustic mismatch model (AMM) and the diffuse mismatch model (DMM), where the weight of the AMM transmission coefficient is the same wavelength-dependent specularity parameter related to the effective interface rms roughness that is commonly used to describe diffuse interface scattering. The model is applied to multiple III-arsenide superlattices, and the results are in very good agreement with experimental findings. The method is both simple and accurate, easy to implement, and applicable to complicated SL systems, such as the active regions of quantum cascade lasers. It is also valid for other SL material systems with high-quality interfaces and predominantly incoherent phonon transport.

  14. Thermally conductive cementitious grout for geothermal heat pump systems

    DOE Patents [OSTI]

    Allan, Marita

    2001-01-01

    A thermally conductive cement-sand grout for use with a geothermal heat pump system. The cement sand grout contains cement, silica sand, a superplasticizer, water and optionally bentonite. The present invention also includes a method of filling boreholes used for geothermal heat pump systems with the thermally conductive cement-sand grout. The cement-sand grout has improved thermal conductivity over neat cement and bentonite grouts, which allows shallower bore holes to be used to provide an equivalent heat transfer capacity. In addition, the cement-sand grouts of the present invention also provide improved bond strengths and decreased permeabilities. The cement-sand grouts can also contain blast furnace slag, fly ash, a thermoplastic air entraining agent, latex, a shrinkage reducing admixture, calcium oxide and combinations thereof.

  15. Thermal flux limited electron Kapitza conductance in copper-niobium multilayers

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Cheaito, Ramez; Hattar, Khalid Mikhiel; Gaskins, John T.; Yadav, Ajay K.; Duda, John C.; Beechem, III, Thomas Edwin; Ihlefeld, Jon; Piekos, Edward S.; Baldwin, Jon K.; Misra, Amit; et al

    2015-03-05

    The interplay between the contributions of electron thermal flux and interface scattering to the Kapitza conductance across metal-metal interfaces through measurements of thermal conductivity of copper-niobium multilayers was studied. Thermal conductivities of copper-niobium multilayer films of period thicknesses ranging from 5.4 to 96.2 nm and sample thicknesses ranging from 962 to 2677 nm are measured by time-domain thermoreflectance over a range of temperatures from 78 to 500 K. The Kapitza conductances between the Cu and Nb interfaces in multilayer films are determined from the thermal conductivities using a series resistor model and are in good agreement with the electron diffusemore » mismatch model. The results for the thermal boundary conductance between Cu and Nb are compared to literature values for the thermal boundary conductance across Al-Cu and Pd-Ir interfaces, and demonstrate that the interface conductance in metallic systems is dictated by the temperature derivative of the electron energy flux in the metallic layers, rather than electron mean free path or scattering processes at the interface.« less

  16. Thermal flux limited electron Kapitza conductance in copper-niobium multilayers

    SciTech Connect (OSTI)

    Cheaito, Ramez; Hattar, Khalid Mikhiel; Gaskins, John T.; Yadav, Ajay K.; Duda, John C.; Beechem, III, Thomas Edwin; Ihlefeld, Jon; Piekos, Edward S.; Baldwin, Jon K.; Misra, Amit; Hopkins, Patrick E.

    2015-03-05

    The interplay between the contributions of electron thermal flux and interface scattering to the Kapitza conductance across metal-metal interfaces through measurements of thermal conductivity of copper-niobium multilayers was studied. Thermal conductivities of copper-niobium multilayer films of period thicknesses ranging from 5.4 to 96.2 nm and sample thicknesses ranging from 962 to 2677 nm are measured by time-domain thermoreflectance over a range of temperatures from 78 to 500 K. The Kapitza conductances between the Cu and Nb interfaces in multilayer films are determined from the thermal conductivities using a series resistor model and are in good agreement with the electron diffuse mismatch model. The results for the thermal boundary conductance between Cu and Nb are compared to literature values for the thermal boundary conductance across Al-Cu and Pd-Ir interfaces, and demonstrate that the interface conductance in metallic systems is dictated by the temperature derivative of the electron energy flux in the metallic layers, rather than electron mean free path or scattering processes at the interface.

  17. High thermal conductivity lossy dielectric using a multi layer configuration

    DOE Patents [OSTI]

    Tiegs, Terry N.; Kiggans, Jr., James O.

    2003-01-01

    Systems and methods are described for loss dielectrics. A loss dielectric includes at least one high dielectric loss layer and at least one high thermal conductivity-electrically insulating layer adjacent the at least one high dielectric loss layer. A method of manufacturing a loss dielectric includes providing at least one high dielectric loss layer and providing at least one high thermal conductivity-electrically insulating layer adjacent the at least one high dielectric loss layer. The systems and methods provide advantages because the loss dielectrics are less costly and more environmentally friendly than the available alternatives.

  18. Developing a High Thermal Conductivity Fuel with Silicon Carbide Additives

    SciTech Connect (OSTI)

    baney, Ronald; Tulenko, James

    2012-11-20

    The objective of this research is to increase the thermal conductivity of uranium oxide (UO{sub 2}) without significantly impacting its neutronic properties. The concept is to incorporate another high thermal conductivity material, silicon carbide (SiC), in the form of whiskers or from nanoparticles of SiC and a SiC polymeric precursor into UO{sub 2}. This is expected to form a percolation pathway lattice for conductive heat transfer out of the fuel pellet. The thermal conductivity of SiC would control the overall fuel pellet thermal conductivity. The challenge is to show the effectiveness of a low temperature sintering process, because of a UO{sub 2}-SiC reaction at 1,377°C, a temperature far below the normal sintering temperature. Researchers will study three strategies to overcome the processing difficulties associated with pore clogging and the chemical reaction of SiC and UO{sub 2} at temperatures above 1,300°C:

  19. Duality of the Interfacial Thermal Conductance in Graphene-based Nanocomposites

    SciTech Connect (OSTI)

    Liu, Ying; Huang, Jingsong; Yang, Bao; Sumpter, Bobby G; Qiao, Rui

    2014-01-01

    The thermal conductance of graphene-matrix interfaces plays a key role in controlling the thermal transport properties of graphene-based nanocomposites. Using classical molecular dynamics simulations, we found that the interfacial thermal conductance depends strongly on the mode of heat transfer at the graphene-matrix interfaces: if heat enters graphene from one side of its basal plane and immediately leaves the graphene through the other side, the corresponding interfacial thermal conductance, G(across), is large; if heat enters graphene from both sides of its basal plane and leaves the graphene at a position far away on its basal plane, the corresponding interfacial thermal conductance, G(non-across), is small. For a single-layer graphene immersed in liquid octane, G(across) is ~150 MW/m2K while Gnon-across is ~5 MW/m2K. G(across) decreases with increasing multi-layer graphene thickness (i.e., number of layers in graphene) and approaches an asymptotic value of 100 MW/m2K for 7-layer graphenes. G(non-across) increases only marginally as the graphene sheet thickness increases. Such a duality of the interface thermal conductance for different probing methods and its dependence on graphene sheet thickness can be traced ultimately to the unique physical and chemical structure of graphene materials. The ramifications of these results in areas such as experimental measurement of thermal conductivity of graphene and the design of graphene-based thermal nanocomposites are discussed.

  20. Low Thermal Conductivity, High Durability Thermal Barrier Coatings for IGCC Environments

    SciTech Connect (OSTI)

    Jordan, Eric; Gell, Maurice

    2015-01-15

    Advanced thermal barrier coatings (TBC) are crucial to improved energy efficiency in next generation gas turbine engines. The use of traditional topcoat materials, e.g. yttria-stabilized zirconia (YSZ), is limited at elevated temperatures due to (1) the accelerated undesirable phase transformations and (2) corrosive attacks by calcium-magnesium-aluminum-silicate (CMAS) deposits and moisture. The first goal of this project is to use the Solution Precursor Plasma Spray (SPPS) process to further reduce the thermal conductivity of YSZ TBCs by introducing a unique microstructural feature of layered porosity, called inter-pass boundaries (IPBs). Extensive process optimization accompanied with hundreds of spray trials as well as associated SEM cross-section and laser-flash measurements, yielded a thermal conductivity as low as 0.62 Wm⁻¹K⁻¹ in SPPS YSZ TBCs, approximately 50% reduction of APS TBCs; while other engine critical properties, such as cyclic durability, erosion resistance and sintering resistance, were characterized to be equivalent or better than APS baselines. In addition, modifications were introduced to SPPS TBCs so as to enhance their resistance to CMAS under harsh IGCC environments. Several mitigation approaches were explored, including doping the coatings with Al₂O₃ and TiO₂, applying a CMAS infiltration-inhibiting surface layer, and filling topcoat cracks with blocking substances. The efficacy of all these modifications was assessed with a set of novel CMAS-TBC interaction tests, and the moisture resistance was tested in a custom-built high-temperature moisture rig. In the end, the optimal low thermal conductivity TBC system was selected based on all evaluation tests and its processing conditions were documented. The optimal coating consisted on a thick inner layer of YSZ coating made by the SPPS process having a thermal conductivity 50% lower than standard YSZ coatings topped with a high temperature tolerant CMAS resistant gadolinium

  1. Pretest Caluculations of Temperature Changes for Field Thermal Conductivity Tests

    SciTech Connect (OSTI)

    N.S. Brodsky

    2002-07-17

    A large volume fraction of the potential monitored geologic repository at Yucca Mountain may reside in the Tptpll (Tertiary, Paintbrush Group, Topopah Spring Tuff, crystal poor, lower lithophysal) lithostratigraphic unit. This unit is characterized by voids, or lithophysae, which range in size from centimeters to meters. A series of thermal conductivity field tests are planned in the Enhanced Characterization of the Repository Block (ECRB) Cross Drift. The objective of the pretest calculation described in this document is to predict changes in temperatures in the surrounding rock for these tests for a given heater power and a set of thermal transport properties. The calculation can be extended, as described in this document, to obtain thermal conductivity, thermal capacitance (density x heat capacity, J {center_dot} m{sup -3} {center_dot} K{sup -1}), and thermal diffusivity from the field data. The work has been conducted under the ''Technical Work Plan For: Testing and Monitoring'' (BSC 2001). One of the outcomes of this analysis is to determine the initial output of the heater. This heater output must be sufficiently high that it will provide results in a reasonably short period of time (within several weeks or a month) and be sufficiently high that the heat increase is detectable by the instruments employed in the test. The test will be conducted in stages and heater output will be step increased as the test progresses. If the initial temperature is set too high, the experiment will not have as many steps and thus fewer thermal conductivity data points will result.

  2. The effect of thermal aging on the thermal conductivity of plasma sprayed and EB-PVD thermal barrier coatings

    SciTech Connect (OSTI)

    Dinwiddie, R.B.; Beecher, S.C.; Porter, W.D.; Nagaraj, B.A.

    1996-05-01

    Thermal barrier coatings (TBCs) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBCs is of primary importance. Electron beam-physical vapor deposition (EV-PVD) and air plasma spraying (APS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The density of the APS coatings was controlled by varying the spray parameters. The low density APS yttria-partially stabilized zirconia (yttria-PSZ) coatings yielded a thermal conductivity that is lower than both the high density APS coatings and the EB-PVD coatings. The thermal aging of both fully and partially stabilized zirconia are compared. The thermal conductivity of the coatings permanently increases upon exposure to high temperatures. These increases are attributed to microstructural changes within the coatings. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the EB-PVD coatings are less susceptible to thermal aging effects, results suggest that they typically have a higher thermal conductivity than APS coatings before thermal aging. The increases in thermal conductivity due to thermal aging for plasma sprayed partially stabilized zirconia have been found to be less than for plasma sprayed fully stabilized zirconia coatings.

  3. Mode dependent lattice thermal conductivity of single layer graphene

    SciTech Connect (OSTI)

    Wei, Zhiyong; Yang, Juekuan; Bi, Kedong; Chen, Yunfei

    2014-10-21

    Molecular dynamics simulation is performed to extract the phonon dispersion and phonon lifetime of single layer graphene. The mode dependent thermal conductivity is calculated from the phonon kinetic theory. The predicted thermal conductivity at room temperature exhibits important quantum effects due to the high Debye temperature of graphene. But the quantum effects are reduced significantly when the simulated temperature is as high as 1000 K. Our calculations show that out-of-plane modes contribute about 41.1% to the total thermal conductivity at room temperature. The relative contribution of out-of-plane modes has a little decrease with the increase of temperature. Contact with substrate can reduce both the total thermal conductivity of graphene and the relative contribution of out-of-plane modes, in agreement with previous experiments and theories. Increasing the coupling strength between graphene and substrate can further reduce the relative contribution of out-of-plane modes. The present investigations also show that the relative contribution of different mode phonons is not sensitive to the grain size of graphene. The obtained phonon relaxation time provides useful insight for understanding the phonon mean free path and the size effects in graphene.

  4. Effect of interfacial interactions on the thermal conductivity and interfacial thermal conductance in tungstengraphene layered structure

    SciTech Connect (OSTI)

    Jagannadham, K.

    2014-09-01

    Graphene film was deposited by microwave plasma assisted deposition on polished oxygen free high conductivity copper foils. Tungstengraphene layered film was formed by deposition of tungsten film by magnetron sputtering on the graphene covered copper foils. Tungsten film was also deposited directly on copper foil without graphene as the intermediate film. The tungstengraphenecopper samples were heated at different temperatures up to 900?C in argon atmosphere to form an interfacial tungsten carbide film. Tungsten film deposited on thicker graphene platelets dispersed on silicon wafer was also heated at 900?C to identify the formation of tungsten carbide film by reaction of tungsten with graphene platelets. The films were characterized by scanning electron microscopy, Raman spectroscopy, and x-ray diffraction. It was found that tungsten carbide film formed at the interface upon heating only above 650?C. Transient thermoreflectance signal from the tungsten film surface on the samples was collected and modeled using one-dimensional heat equation. The experimental and modeled results showed that the presence of graphene at the interface reduced the cross-plane effective thermal conductivity and the interfacial thermal conductance of the layer structure. Heating at 650 and 900?C in argon further reduced the cross-plane thermal conductivity and interface thermal conductance as a result of formation nanocrystalline tungsten carbide at the interface leading to separation and formation of voids. The present results emphasize that interfacial interactions between graphene and carbide forming bcc and hcp elements will reduce the cross-plane effective thermal conductivity in composites.

  5. Basal-plane thermal conductivity of few-layer molybdenum disulfide

    SciTech Connect (OSTI)

    Jo, Insun; Ou, Eric; Shi, Li; Pettes, Michael Thompson; Wu, Wei

    2014-05-19

    We report the in-plane thermal conductivity of suspended exfoliated few-layer molybdenum disulfide (MoS{sub 2}) samples that were measured by suspended micro-devices with integrated resistance thermometers. The obtained room-temperature thermal conductivity values are (4450) and (4852) W m{sup ?1} K{sup ?1} for two samples that are 4 and 7 layers thick, respectively. For both samples, the peak thermal conductivity occurs at a temperature close to 120?K, above which the thermal conductivity is dominated by intrinsic phonon-phonon scattering although phonon scattering by surface disorders can still play an important role in these samples especially at low temperatures.

  6. Composition and Manufacturing Effects on Electrical Conductivity of Li/FeS 2 Thermal Battery Cathodes

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Reinholz, Emilee L.; Roberts, Scott A.; Apblett, Christopher A.; Lechman, Jeremy B.; Schunk, P. Randall

    2016-06-11

    The electrical conductivity is key to the performance of thermal battery cathodes. In this work we present the effects of manufacturing and processing conditions on the electrical conductivity of Li/FeS2 thermal battery cathodes. Finite element simulations were used to compute the conductivity of three-dimensional microcomputed tomography cathode microstructures and compare results to experimental impedance spectroscopy measurements. A regression analysis reveals a predictive relationship between composition, processing conditions, and electrical conductivity; a trend which is largely erased after thermally-induced deformation. Moreover, the trend applies to both experimental and simulation results, although is not as apparent in simulations. This research is amore » step toward a more fundamental understanding of the effects of processing and composition on thermal battery component microstructure, properties, and performance.« less

  7. Thermal conductivity in nanocrystalline-SiC/C superlattices

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Habermehl, S.; Serrano, J. R.

    2015-11-17

    We reported the formation of thin film superlattices consisting of alternating layers of nitrogen-doped SiC (SiC:N) and C. Periodically terminating the SiC:N surface with a graphitic C boundary layer and controlling the SiC:N/C thickness ratio yield nanocrystalline SiC grains ranging in size from 365 to 23 nm. Frequency domain thermo-reflectance is employed to determine the thermal conductivity, which is found to vary from 35.5 W m-1 K-1 for monolithic undoped α-SiC films to 1.6 W m-1 K-1 for a SiC:N/C superlattice with a 47 nm period and a SiC:N/C thickness ratio of 11. A series conductance model is employed tomore » explain the dependence of the thermal conductivity on the superlatticestructure. Our results indicate that the thermal conductivity is more dependent on the SiC:N/C thickness ratio than the SiC:N grain size, indicative of strong boundary layerphonon scattering.« less

  8. Thermal conductivity in nanocrystalline-SiC/C superlattices

    SciTech Connect (OSTI)

    Habermehl, S.; Serrano, J. R.

    2015-11-17

    We reported the formation of thin film superlattices consisting of alternating layers of nitrogen-doped SiC (SiC:N) and C. Periodically terminating the SiC:N surface with a graphitic C boundary layer and controlling the SiC:N/C thickness ratio yield nanocrystalline SiC grains ranging in size from 365 to 23 nm. Frequency domain thermo-reflectance is employed to determine the thermal conductivity, which is found to vary from 35.5 W m-1 K-1 for monolithic undoped α-SiC films to 1.6 W m-1 K-1 for a SiC:N/C superlattice with a 47 nm period and a SiC:N/C thickness ratio of 11. A series conductance model is employed to explain the dependence of the thermal conductivity on the superlatticestructure. Our results indicate that the thermal conductivity is more dependent on the SiC:N/C thickness ratio than the SiC:N grain size, indicative of strong boundary layerphonon scattering.

  9. Thermal conductivity of high performance carbon nanotube yarn-like fibers

    SciTech Connect (OSTI)

    Mayhew, Eric; Prakash, Vikas

    2014-05-07

    In the present paper, we present results of thermal conductivity measurements in free standing carbon nanotube (CNT) yarn-like fibers. The measurements are made using a T-type experimental configuration utilizing a Wollaston-wire hot probe inside a scanning electron microscope. In this technique, a suspended platinum wire is used both as a heater and a thermal sensor. A low frequency alternating current source is used to heat the probe wire while the third harmonic voltage across the wire is measured by a lock-in amplifier. The conductivity is deduced from an analytical model that relates the drop in the spatially averaged temperature of the wire to that of the sample. The average thermal conductivity of the neat CNT fibers and the CNT polymer composite fibers is found to be 448?W/m-K and 225?W/m-K, respectively. These values for conductivity are amongst the highest measured for CNT yarn-like fibers fabricated using a dry spinning process from vertically aligned CNT arrays. The enhancement in thermal conductivity is understood to be due to an increase in the CNT fiber elastic stiffness during the draw and twist operations, lower CNT thermal contact resistance due to increase in CNT contact area, and better alignment of the CNT fibrils along the length of the fiber.

  10. Lattice thermal conductivity of filled skutterudites: An anharmonicity perspective

    SciTech Connect (OSTI)

    Geng, Huiyuan, E-mail: genghuiyuan@hit.edu.cn; Meng, Xianfu; Zhang, Hao; Zhang, Jian [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China)

    2014-10-28

    We report a phenomenological model to calculate the high-temperature lattice thermal conductivity of filled skutterudite antimonides. The model needs no phonon resonant scattering terms. Instead, we assume that umklapp processes dominate the high-temperature phonon scattering. In order to represent the anharmonicity introduced by the filling atom, we introduce a Gaussian term into the relaxation time of the umklapp process. The developed model agrees remarkably well with the experimental results of RE{sub f}Co{sub 4}Sb{sub 12} and RE{sub f}Fe{sub 4}Sb{sub 12} (RE?=?Yb, Ba, and Ca) alloys. To further test the validity of our model, we calculate the lattice thermal conductivity of nanostructured or multi-filled skutterudites. The calculation results are also in good agreement with experiment, increasing our confidence in the developed anharmonicity model.

  11. Reduced thermal conductivity in niobium-doped calcium-manganate compounds for thermoelectric applications

    SciTech Connect (OSTI)

    Graff, Ayelet; Amouyal, Yaron

    2014-11-03

    Reduction of thermal conductivity is essential for obtaining high energy conversion efficiency in thermoelectric materials. We report on significant reduction of thermal conductivity in niobium-doped CaO(CaMnO{sub 3}){sub m} compounds for thermoelectric energy harvesting due to introduction of extra CaO-planes in the CaMnO{sub 3}-base material. We measure the thermal conductivities of the different compounds applying the laser flash analysis at temperatures between 300 and 1000 K, and observe a remarkable reduction in thermal conductivity with increasing CaO-planar density, from a value of 3.7 W·m{sup −1}K{sup −1} for m = ∞ down to 1.5 W·m{sup −1}K{sup −1} for m = 1 at 400 K. This apparent correlation between thermal conductivity and CaO-planar density is elucidated in terms of boundary phonon scattering, providing us with a practical way to manipulate lattice thermal conductivity via microstructural modifications.

  12. Anisotropic in-plane thermal conductivity of black phosphorus nanoribbons at temperatures higher than 100 K

    SciTech Connect (OSTI)

    Lee, Sangwook; Yang, Fan; Suh, Joonki; Yang, Sijie; Lee, Yeonbae; Li, Guo; Sung Choe, Hwan; Suslu, Aslihan; Chen, Yabin; Ko, Changhyun; Park, Joonsuk; Liu, Kai; Li, Jingbo; Hippalgaonkar, Kedar; Urban, Jeffrey J.; Tongay, Sefaattin; Wu, Junqiao

    2015-10-16

    Black phosphorus attracts enormous attention as a promising layered material for electronic, optoelectronic and thermoelectric applications. Here we report large anisotropy in in-plane thermal conductivity of single-crystal black phosphorus nanoribbons along the zigzag and armchair lattice directions at variable temperatures. Thermal conductivity measurements were carried out under the condition of steady-state longitudinal heat flow using suspended-pad micro-devices. We discovered increasing thermal conductivity anisotropy, up to a factor of two, with temperatures above 100 K. A size effect in thermal conductivity was also observed in which thinner nanoribbons show lower thermal conductivity. Analysed with the relaxation time approximation model using phonon dispersions obtained based on density function perturbation theory, the high anisotropy is attributed mainly to direction-dependent phonon dispersion and partially to phonon–phonon scattering. Lastly, our results revealing the intrinsic, orientation-dependent thermal conductivity of black phosphorus are useful for designing devices, as well as understanding fundamental physical properties of layered materials.

  13. Anisotropic in-plane thermal conductivity of black phosphorus nanoribbons at temperatures higher than 100 K

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Lee, Sangwook; Yang, Fan; Suh, Joonki; Yang, Sijie; Lee, Yeonbae; Li, Guo; Sung Choe, Hwan; Suslu, Aslihan; Chen, Yabin; Ko, Changhyun; et al

    2015-10-16

    Black phosphorus attracts enormous attention as a promising layered material for electronic, optoelectronic and thermoelectric applications. Here we report large anisotropy in in-plane thermal conductivity of single-crystal black phosphorus nanoribbons along the zigzag and armchair lattice directions at variable temperatures. Thermal conductivity measurements were carried out under the condition of steady-state longitudinal heat flow using suspended-pad micro-devices. We discovered increasing thermal conductivity anisotropy, up to a factor of two, with temperatures above 100 K. A size effect in thermal conductivity was also observed in which thinner nanoribbons show lower thermal conductivity. Analysed with the relaxation time approximation model using phononmore » dispersions obtained based on density function perturbation theory, the high anisotropy is attributed mainly to direction-dependent phonon dispersion and partially to phonon–phonon scattering. Lastly, our results revealing the intrinsic, orientation-dependent thermal conductivity of black phosphorus are useful for designing devices, as well as understanding fundamental physical properties of layered materials.« less

  14. Thermal conductivities of Wilsonville solvent and Wilsonville solvent/Illinois No. 6 coal slurry. [Wilsonville solvent

    SciTech Connect (OSTI)

    Wilson, J.H.; Mrochek, J.E.; Johnson, J.K.

    1984-01-01

    Thermal conductivities of a Wilsonville solvent and of a slurry prepared from this solvent and Illinois No. 6 coal have been measured at temperatures from 295 up to 500 K. With increasing temperature, the thermal conductivity varied from 1.23 to 1.02 mW cm/sup -1/ K/sup -1/ (296 to 438 K) and from 1.51 to 1.02 mW cm/sup -1/ K/sup -1/ (295 to 505 K) for the solvent and the slurry, respectively. At room temperature, measurements on toluene were accurate to within 3% of literature values. 18 references, 9 figures, 7 tables.

  15. Continuous Processing of High Thermal Conductivity Fibers and Sheets

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Professor Gang Chen, Carl Richard Soderberg Professor of Power Engineering 617-253-0006 (phone), 617-324-5545 (fax) gchen2@mit.edu U.S. DOE Advanced Manufacturing Office Peer Review Meeting Washington, D.C. May 6-7, 2014 This presentation does not contain any proprietary, confidential, or otherwise restricted information. Project Objective  Plastics are less expensive, lighter, and require less energy to process than metals; however, they have low thermal conductivity values (~0.3 W/mK) 

  16. Nanoscale size dependence parameters on lattice thermal conductivity of Wurtzite GaN nanowires

    SciTech Connect (OSTI)

    Mamand, S.M.; Omar, M.S.; Muhammad, A.J.

    2012-05-15

    Graphical abstract: Temperature dependence of calculated lattice thermal conductivity of Wurtzite GaN nanowires. Highlights: Black-Right-Pointing-Pointer A modified Callaway model is used to calculate lattice thermal conductivity of Wurtzite GaN nanowires. Black-Right-Pointing-Pointer A direct method is used to calculate phonon group velocity for these nanowires. Black-Right-Pointing-Pointer 3-Gruneisen parameter, surface roughness, and dislocations are successfully investigated. Black-Right-Pointing-Pointer Dislocation densities are decreases with the decrease of wires diameter. -- Abstract: A detailed calculation of lattice thermal conductivity of freestanding Wurtzite GaN nanowires with diameter ranging from 97 to 160 nm in the temperature range 2-300 K, was performed using a modified Callaway model. Both longitudinal and transverse modes are taken into account explicitly in the model. A method is used to calculate the Debye and phonon group velocities for different nanowire diameters from their related melting points. Effect of Gruneisen parameter, surface roughness, and dislocations as structure dependent parameters are successfully used to correlate the calculated values of lattice thermal conductivity to that of the experimentally measured curves. It was observed that Gruneisen parameter will decrease with decreasing nanowire diameters. Scattering of phonons is assumed to be by nanowire boundaries, imperfections, dislocations, electrons, and other phonons via both normal and Umklapp processes. Phonon confinement and size effects as well as the role of dislocation in limiting thermal conductivity are investigated. At high temperatures and for dislocation densities greater than 10{sup 14} m{sup -2} the lattice thermal conductivity would be limited by dislocation density, but for dislocation densities less than 10{sup 14} m{sup -2}, lattice thermal conductivity would be independent of that.

  17. Calculated transport properties of CdO: thermal conductivity and thermoelectric power factor

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Lindsay, Lucas R.; Parker, David S.

    2015-10-01

    We present first principles calculations of the thermal and electronic transport properties of the oxide semiconductor CdO. In particular, we find from theory that the accepted thermal conductivity κ value of 0.7 Wm-1K-1 is approximately one order of magnitude too small; our calculations of κ of CdO are in good agreement with recent measurements. We also find that alloying of MgO with CdO is an effective means to reduce the lattice contribution to κ, despite MgO having a much larger thermal conductivity. We further consider the electronic structure of CdO in relation to thermoelectric performance, finding that large thermoelectric powermore » factors may occur if the material can be heavily doped p-type. This work develops insight into the nature of thermal and electronic transport in an important oxide semiconductor.« less

  18. Calculated transport properties of CdO: thermal conductivity and thermoelectric power factor

    SciTech Connect (OSTI)

    Lindsay, Lucas R.; Parker, David S.

    2015-10-01

    We present first principles calculations of the thermal and electronic transport properties of the oxide semiconductor CdO. In particular, we find from theory that the accepted thermal conductivity κ value of 0.7 Wm-1K-1 is approximately one order of magnitude too small; our calculations of κ of CdO are in good agreement with recent measurements. We also find that alloying of MgO with CdO is an effective means to reduce the lattice contribution to κ, despite MgO having a much larger thermal conductivity. We further consider the electronic structure of CdO in relation to thermoelectric performance, finding that large thermoelectric power factors may occur if the material can be heavily doped p-type. This work develops insight into the nature of thermal and electronic transport in an important oxide semiconductor.

  19. Through-thickness Membrane Conductivity Measurement for HTM Program...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Through-thickness Membrane Conductivity Measurement for HTM Program: Issues and Approach Through-thickness Membrane Conductivity Measurement for HTM Program: Issues and Approach ...

  20. Esimation of field-scale thermal conductivities of unsaturatedrocks from in-situ temperature data

    SciTech Connect (OSTI)

    Mukhopadhyay, Sumit; Tsang, Yvonne W.; Birkholzer, Jens T.

    2006-06-26

    A general approach is presented here which allows estimationof field-scale thermal properties of unsaturated rock using temperaturedata collected from in situ heater tests. The approach developed here isused to determine the thermal conductivities of the unsaturated host rockof the Drift Scale Test (DST) at Yucca Mountain, Nevada. The DST wasdesigned to obtain thermal, hydrological, mechanical, and chemical (THMC)data in the unsaturated fractured rock of Yucca Mountain. Sophisticatednumerical models have been developed to analyze these THMC data. However,though the objective of those models was to analyze "field-scale" (of theorder of tens-of-meters) THMC data, thermal conductivities measured from"laboratory-scale" core samples have been used as input parameters.While, in the absence of a better alternative, using laboratory-scalethermal conductivity values in field-scale models can be justified, suchapplications introduce uncertainties in the outcome of the models. Thetemperature data collected from the DST provides a unique opportunity toresolve some of these uncertainties. These temperature data can be usedto estimate the thermal conductivity of the DST host rock and, given thelarge volume of rock affected by heating at the DST, such an estimatewill be a more reliable effective thermal conductivity value for fieldscale application. In this paper, thus, temperature data from the DST areused to develop an estimate of the field-scale thermal conductivityvalues of the unsaturated host rock of the DST. An analytical solution isdeveloped for the temperature rise in the host rock of the DST; and usinga nonlinear fitting routine, a best-fit estimate of field-scale thermalconductivity for the DST host rock is obtained. Temperature data from theDST show evidence of two distinct thermal regimes: a zone below boiling(wet) and a zone above boiling (dry). Estimates of thermal conductivityfor both the wet and dry zones are obtained in this paper. Sensitivity ofthese estimates

  1. Thermal conductivity of graphene mediated by strain and size

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Kuang, Youdi; Shi, Sanqiang; Wang, Xinjiang; Huang, Baoling; Lindsay, Lucas

    2016-06-09

    Based on first-principles calculations and full iterative solution of the linearized Boltzmann–Peierls transport equation for phonons, we systematically investigate effects of strain, size and temperature on the thermal conductivity k of suspended graphene. The calculated size-dependent and temperature-dependent k for finite samples agree well with experimental data. The results show that, contrast to the convergent room-temperature k = 5450 W/m-K of unstrained graphene at a sample size ~8 cm, k of strained graphene diverges with increasing the sample size even at high temperature. Out-of-plane acoustic phonons are responsible for the significant size effect in unstrained and strained graphene due tomore » their ultralong mean free path and acoustic phonons with wavelength smaller than 10 nm contribute 80% to the intrinsic room temperature k of unstrained graphene. Tensile strain hardens the flexural modes and increases their lifetimes, causing interesting dependence of k on sample size and strain due to the competition between boundary scattering and intrinsic phonon–phonon scattering. k of graphene can be tuned within a large range by strain for the size larger than 500 μm. These findings shed light on the nature of thermal transport in two-dimensional materials and may guide predicting and engineering k of graphene by varying strain and size.« less

  2. Angle Resolved Thermal Conductivity of CeCoIn5 along the Nodal...

    Office of Scientific and Technical Information (OSTI)

    Angle Resolved Thermal Conductivity of CeCoIn5 along the Nodal Direction Citation Details In-Document Search Title: Angle Resolved Thermal Conductivity of CeCoIn5 along the Nodal ...

  3. Estimation of host rock thermal conductivities using thetemperature data from the drift-scale test at Yucca Mountain,Nevada

    SciTech Connect (OSTI)

    Mukhopadhyay, Sumitra; Tsang, Y.W.

    2003-11-25

    A large volume of temperature data has been collected from a very large, underground heater test, the Drift Scale Test (DST) at Yucca Mountain, Nevada. The DST was designed to obtain thermal, hydrological, mechanical, and chemical (THMC) data in the unsaturated fractured rock of Yucca Mountain. Sophisticated numerical models have been developed to analyze the collected THMC data. In these analyses, thermal conductivities measured from core samples have been used as input parameters to the model. However, it was not known whether these core measurements represented the true field-scale thermal conductivity of the host rock. Realizing these difficulties, elaborate, computationally intensive geostatistical simulations have also been performed to obtain field-scale thermal conductivity of the host rock from the core measurements. In this paper, we use the temperature data from the DST as the input (instead of the measured core-scale thermal conductivity values) to develop an estimate of the field-scale thermal conductivity values. Assuming a conductive thermal regime, we develop an analytical solution for the temperature rise in the host rock of the DST; and using a nonlinear fitting routine, we obtain a best-fit estimate of field-scale thermal conductivity for the DST host rock. The temperature data collected from the DST shows clear evidence of two distinct thermal regimes: a zone below boiling (wet) and a zone above boiling (dry). We obtain estimates of thermal conductivity for both the wet and dry zones. We also analyze the sensitivity of these estimates to the input heating power of the DST.

  4. Density dependence of the room temperature thermal conductivity of atomic layer deposition-grown amorphous alumina (Al{sub 2}O{sub 3})

    SciTech Connect (OSTI)

    Gorham, Caroline S.; Gaskins, John T.; Hopkins, Patrick E.; Parsons, Gregory N.; Losego, Mark D.

    2014-06-23

    We report on the thermal conductivity of atomic layer deposition-grown amorphous alumina thin films as a function of atomic density. Using time domain thermoreflectance, we measure the thermal conductivity of the thin alumina films at room temperature. The thermal conductivities vary ?35% for a nearly 15% change in atomic density and are substrate independent. No density dependence of the longitudinal sound speeds is observed with picosecond acoustics. The density dependence of the thermal conductivity agrees well with a minimum limit to thermal conductivity model that is modified with a differential effective-medium approximation.

  5. Ceramic materials with low thermal conductivity and low coefficients of thermal expansion

    DOE Patents [OSTI]

    Brown, J.; Hirschfeld, D.; Liu, D.M.; Yang, Y.; Li, T.; Swanson, R.E.; Van Aken, S.; Kim, J.M.

    1992-04-07

    Compositions, having the general formula (Ca[sub x]Mg[sub 1[minus]x])Zr[sub 4](PO[sub 4])[sub 6] where x is between 0.5 and 0.99, are produced by solid state and sol-gel processes. In a preferred embodiment, when x is between 0.5 and 0.8, the MgCZP materials have near-zero coefficients of thermal expansion. The MgCZPs of the present invention also show unusually low thermal conductivities, and are stable at high temperatures. Macrostructures formed from MgCZP are useful in a wide variety of high-temperature applications. In a preferred process, calcium, magnesium, and zirconium nitrate solutions have their pH adjusted to between 7 and 9 either before or after the addition of ammonium dihydrogen phosphate. After dehydration to a gel, and calcination at temperatures in excess of 850 C for approximately 16 hours, single phase crystalline MgCZP powders with particle sizes ranging from approximately 20 nm to 50 nm result. The MgCZP powders are then sintered at temperatures ranging from 1200 C to 1350 C to form solid macrostructures with near-zero bulk coefficients of thermal expansion and low thermal conductivities. Porous macrostructures of the MgCZP powders of the present invention are also formed by combination with a polymeric powder and a binding agent, and sintering at high temperatures. The porosity of the resulting macrostructures can be adjusted by varying the particle size of the polymeric powder used. 7 figs.

  6. Ceramic materials with low thermal conductivity and low coefficients of thermal expansion

    DOE Patents [OSTI]

    Brown, Jesse; Hirschfeld, Deidre; Liu, Dean-Mo; Yang, Yaping; Li, Tingkai; Swanson, Robert E.; Van Aken, Steven; Kim, Jin-Min

    1992-01-01

    Compositions having the general formula (Ca.sub.x Mg.sub.1-x)Zr.sub.4 (PO.sub.4).sub.6 where x is between 0.5 and 0.99 are produced by solid state and sol-gel processes. In a preferred embodiment, when x is between 0.5 and 0.8, the MgCZP materials have near-zero coefficients of thermal expansion. The MgCZPs of the present invention also show unusually low thermal conductivities, and are stable at high temperatures. Macrostructures formed from MgCZP are useful in a wide variety of high-temperature applications. In a preferred process, calcium, magnesium, and zirconium nitrate solutions have their pH adjusted to between 7 and 9 either before or after the addition of ammonium dihydrogen phosphate. After dehydration to a gel, and calcination at temperatures in excess of 850.degree. C. for approximately 16 hours, single phase crystalline MgCZP powders with particle sizes ranging from approximately 20 nm to 50 nm result. The MgCZP powders are then sintered at temperatures ranging from 1200.degree. C. to 1350.degree. C. to form solid macrostructures with near-zero bulk coefficients of thermal expansion and low thermal conductivities. Porous macrostructures of the MgCZP powders of the present invention are also formed by combination with a polymeric powder and a binding agent, and sintering at high temperatures. The porosity of the resulting macrostructures can be adjusted by varying the particle size of the polymeric powder used.

  7. Substrate-dependent thermal conductivity of aluminum nitride thin-films processed at low temperature

    SciTech Connect (OSTI)

    Belkerk, B. E.; Bensalem, S.; Soussou, A.; Carette, M.; Djouadi, M. A.; Scudeller, Y.; Al Brithen, H.

    2014-12-01

    In this paper, we report on investigation concerning the substrate-dependent thermal conductivity (k) of Aluminum Nitride (AlN) thin-films processed at low temperature by reactive magnetron sputtering. The thermal conductivity of AlN films grown at low temperature (<200 °C) on single-crystal silicon (Si) and amorphous silicon nitride (SiN) with thicknesses ranging from 100 nm to 4000 nm was measured with the transient hot-strip technique. The k values for AlN films on SiN were found significantly lower than those on Silicon consistently with their microstructures revealed by X-ray diffraction, high resolution scanning electron microscopy, and transmission electron microscopy. The change in k was due to the thermal boundary resistance found to be equal to 10 × 10{sup −9} Km{sup 2}W{sup −1} on SiN against 3.5 × 10{sup −9} Km{sup 2}W{sup −1} on Si. However, the intrinsic thermal conductivity was determined with a value as high as 200 Wm{sup −1}K{sup −1} whatever the substrate.

  8. Resonant bonding leads to low lattice thermal conductivity (Journal...

    Office of Scientific and Technical Information (OSTI)

    Research Org: Energy Frontier Research Centers (EFRC); Solid-State Solar-Thermal Energy ... Country of Publication: United States Language: English Subject: solar (photovoltaic), ...

  9. Thermal interface conductance across a graphene/hexagonal boron nitride heterojunction

    SciTech Connect (OSTI)

    Chen, Chun-Chung; Li, Zhen; Cronin, Stephen B. [Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089 (United States); Shi, Li [Department of Mechanical Engineering and Texas Materials Institute, University of Texas at Austin, Austin, Texas 78712 (United States)

    2014-02-24

    We measure thermal transport across a graphene/hexagonal boron nitride (h-BN) interface by electrically heating the graphene and measuring the temperature difference between the graphene and BN using Raman spectroscopy. Because the temperature of the graphene and BN are measured optically, this approach enables nanometer resolution in the cross-plane direction. A temperature drop of 60?K can be achieved across this junction at high electrical powers (14 mW). Based on the temperature difference and the applied power data, we determine the thermal interface conductance of this junction to be 7.4??10{sup 6}?Wm{sup ?2}K{sup ?1}, which is below the 10{sup 7}10{sup 8}?Wm{sup ?2}K{sup ?1} values previously reported for graphene/SiO{sub 2} interface.

  10. Anomalous pressure dependence of thermal conductivities of large mass ratio compounds

    SciTech Connect (OSTI)

    Lindsay, Lucas R; Broido, David; Carrete, Jesus; Mingo, Natalio; Reinecke, Tom

    2015-01-01

    The lattice thermal conductivities ( ) of binary compound materials are examined as a function of hydrostatic pressure, P, using a first-principles approach. Compound materials with relatively small mass ratios, such as MgO, show an increase in with P, consistent with measurements. Conversely, compounds with large mass ratios (e.g., BSb, BAs, BeTe, BeSe) exhibit decreasing with increasing P, a behavior that cannot be understood using simple theories of . This anomalous P dependence of arises from the fundamentally different nature of the intrinsic scattering processes for heat-carrying acoustic phonons in large mass ratio compounds compared to those with small mass ratios. This work demonstrates the power of first principles methods for thermal properties and advances the understanding of thermal transport in non-metals.

  11. Anomalous pressure dependence of thermal conductivities of large mass ratio compounds

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Lindsay, Lucas R; Broido, David; Carrete, Jesus; Mingo, Natalio; Reinecke, Tom

    2015-01-01

    The lattice thermal conductivities ( ) of binary compound materials are examined as a function of hydrostatic pressure, P, using a first-principles approach. Compound materials with relatively small mass ratios, such as MgO, show an increase in with P, consistent with measurements. Conversely, compounds with large mass ratios (e.g., BSb, BAs, BeTe, BeSe) exhibit decreasing with increasing P, a behavior that cannot be understood using simple theories of . This anomalous P dependence of arises from the fundamentally different nature of the intrinsic scattering processes for heat-carrying acoustic phonons in large mass ratio compounds compared to those with small massmore » ratios. This work demonstrates the power of first principles methods for thermal properties and advances the understanding of thermal transport in non-metals.« less

  12. High thermal conductivity connector having high electrical isolation

    DOE Patents [OSTI]

    Nieman, Ralph C.; Gonczy, John D.; Nicol, Thomas H.

    1995-01-01

    A method and article for providing a low-thermal-resistance, high-electrical-isolation heat intercept connection. The connection method involves clamping, by thermal interference fit, an electrically isolating cylinder between an outer metallic ring and an inner metallic disk. The connection provides durable coupling of a heat sink and a heat source.

  13. Viscosity and thermal conductivity of nanofluids containing multi-walled carbon nanotubes stabilized by chitosan

    SciTech Connect (OSTI)

    Phuoc, Tran X.; Massoudi, Mehrdad; Chen, Ruey-Hung

    2011-01-01

    Thermal conductivity, viscosity, and stability of nanofluids containing multi-walled carbon nanotubes (MWCNTs) stabilized by cationic chitosan were studied. Chitosan with weight fraction of 0.1%, 0.2 wt%, and 0.5 wt% was used to disperse stably MWCNTs in water. The measured thermal conductivity showed an enhancement from 2.3% to 13% for nanofluids that contained from 0.5 wt% to 3 wt% MWCNTs (0.24 to 1.43 vol %). These values are significantly higher than those predicted using the Maxwell's theory. We also observed that the enhancements were independent of the base fluid viscosity. Thus, use of microconvection effect to explain the anomalous thermal conductivity enhancement should be reconsidered. MWCNTs can be used either to enhance or reduce the fluid base viscosity depending on the weight fractions. In the viscosity-reduction case, a reduction up to 20% was measured by this work. In the viscosity-enhancement case, the fluid behaved as a non-Newtonian shear-thinning fluid. By assuming that MWCNT nanofluids behave as a generalized second grade fluid where the viscosity coefficient depends upon the rate of deformation, a theoretical model has been developed. The model was found to describe the fluid behavior very well.

  14. Thermal conductivity of configurable two-dimensional carbon nanotube architecture and strain modulation

    SciTech Connect (OSTI)

    Zhan, H. F.; Bell, J. M.; Gu, Y. T., E-mail: yuantong.gu@qut.edu.au [School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, 2 George St., Brisbane, Queensland 4000 (Australia); Zhang, G. [Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632 (Singapore)

    2014-10-13

    We reported the thermal conductivity of the two-dimensional carbon nanotube (CNT)-based architecture, which can be constructed through welding of single-wall CNTs by electron beam. Using large-scale nonequilibrium molecular dynamics simulations, the thermal conductivity is found to vary with different junction types due to their different phonon scatterings at the junction. The strong length and strain dependence of the thermal conductivity suggests an effective avenue to tune the thermal transport properties of the CNT-based architecture, benefiting the design of nanoscale thermal rectifiers or phonon engineering.

  15. Thermal conductivity studies of novel nanofluids based on metallic silver decorated mesoporous silica nanoparticles

    SciTech Connect (OSTI)

    Tadjarodi, Azadeh; Zabihi, Fatemeh

    2013-10-15

    Graphical abstract: - Highlights: Metallic silver was decorated in mSiO{sub 2} with grafted hemiaminal functional groups. Synthesized nanoparticles were used for preparation of glycerol based nanofluids. The effect of temperature, weight fraction of mSiO{sub 2} and concentration of silver nanoparticles on thermal conductivity of nanofluids was investigated. - Abstract: In the present study, the mesoporous structure of silica (mSiO{sub 2}) nanoparticles as well as hemiaminal grafted mSiO{sub 2} decorated by metallic silver (Ag/mSiO{sub 2}) has been used for the preparation of glycerol based nanofluids. Structural and morphological characterization of the synthesized products have been carried out using Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), UVvis spectroscopy, inductively coupled plasma (ICP) and N{sub 2} adsorptiondesorption isotherms. The thermal conductivity and viscosity of the nanofluids have been measured as a function of temperature for various weight fractions and silver concentrations of mSiO{sub 2} and Ag/mSiO{sub 2} nanoparticles, respectively. The results show that the thermal conductivity of the nanofluids increase up to 9.24% as the weight fraction of mSiO{sub 2} increases up to 4 wt%. Also, increasing the percent of the silver decorated mSiO{sub 2} (Ag/mSiO{sub 2}) up to 2.98% caused an enhancement in the thermal conductivity of the base fluid up to 10.95%. Furthermore, the results show that the nanofluids have Newtonian behavior in the tested temperature range for various concentrations of nanoparticles.

  16. Thermal conductivities of Wilsonville solvent and Wilsonville solvent/Illinois No. 6 coal slurry

    SciTech Connect (OSTI)

    Mrochek, J.E.; Wilson, J.H.; Johnson, J.K.

    1985-12-01

    This report describes instrumentation and techniques that, when used in conjunction with a unique bench-scale flow system for coal liquids, enabled thermal conductivity measurements of fresh, slurried coal-solvent mixtures under more or less dynamic flow conditions. The transient hot-wire technique was selected as the method of choice, and a high-temperature, high-pressure cell, rated for temperatures to 850 K and pressures to 30 MPa (4366 psig), was fabricated from type 347 stainless steel. The cell, constructed of two identical manifolds joined by a length of pipe (34.9-mm OD x 19.7-mm ID), contained a platinum hot wire gauge (40 SWG, 0.076-mm diam) approx.29 cm in length. The measurement system consisted of a commercially available, precision dc current source (programmable and capable of current output to 164 mA) and a custom-built, switching/voltage amplification network with a digital oscilloscope for data acquisition. Measurements of the voltage drop across the hot-wire gauge (4096 data points) were transferred to a minicomputer for analysis and long-term storage. Thermal conductivities were measured on a Wilsonville solvent and a slurry prepared from this solvent and Illinois No. 6 coal over a temperature range of 295 to 505 K. Thermal conductivities for both the solvent and the slurry decreased with increasing temperatures, similar to the trend showed by toluene. The solvent decreased from 1.23 to 1.02 mW cm/sup -1/ K/sup -1/ over the temperature range 296 to 438 K, while the slurry decreased from 1.51 to 1.02 mW cm/sup -1/ K/sup -1/ over the range 295 to 505 K. 20 refs., 9 figs., 7 tabs.

  17. Tuning Interfacial Thermal Conductance of Graphene Embedded in Soft Materials by Vacancy Defects

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Liu, Ying; Hu, Chongze; Huang, Jingsong; Sumpter, Bobby G; Qiao, Rui

    2015-01-01

    Nanocomposites based on graphene dispersed in matrices of soft materials are promising thermal management materials. Their effective thermal conductivity depends on both the thermal conductivity of graphene and the conductance of the thermal transport across graphene-matrix interfaces. Here we report on molecular dynamics simulations of the thermal transport across the interfaces between defected graphene and soft materials in two different modes: in the across mode, heat enters graphene from one side of its basal plane and leaves through the other side; in the non-across mode, heat enters or leaves a graphene simultaneously from both sides of its basal plane. Wemore » show that, as the density of vacancy defects in graphene increases from 0 to 8%, the conductance of the interfacial thermal transport in the across mode increases from 160.4 16 to 207.8 11 MW/m2K, while that in the non-across mode increases from 7.2 0.1 to 17.8 0.6 MW/m2K. The molecular mechanisms for these variations of thermal conductance are clarified by using the phonon density of states and structural characteristics of defected graphenes. On the basis of these results and effective medium theory, we show that it is possible to enhance the effective thermal conductivity of thermal nanocomposites by tuning the density of vacancy defects in graphene despite the fact that graphene s thermal conductivity always decreases as vacancy defects are introduced.« less

  18. Tuning Interfacial Thermal Conductance of Graphene Embedded in Soft Materials by Vacancy Defects

    SciTech Connect (OSTI)

    Liu, Ying; Hu, Chongze; Huang, Jingsong; Sumpter, Bobby G; Qiao, Rui

    2015-01-01

    Nanocomposites based on graphene dispersed in matrices of soft materials are promising thermal management materials. Their effective thermal conductivity depends on both the thermal conductivity of graphene and the conductance of the thermal transport across graphene-matrix interfaces. Here we report on molecular dynamics simulations of the thermal transport across the interfaces between defected graphene and soft materials in two different modes: in the across mode, heat enters graphene from one side of its basal plane and leaves through the other side; in the non-across mode, heat enters or leaves a graphene simultaneously from both sides of its basal plane. We show that, as the density of vacancy defects in graphene increases from 0 to 8%, the conductance of the interfacial thermal transport in the across mode increases from 160.4 16 to 207.8 11 MW/m2K, while that in the non-across mode increases from 7.2 0.1 to 17.8 0.6 MW/m2K. The molecular mechanisms for these variations of thermal conductance are clarified by using the phonon density of states and structural characteristics of defected graphenes. On the basis of these results and effective medium theory, we show that it is possible to enhance the effective thermal conductivity of thermal nanocomposites by tuning the density of vacancy defects in graphene despite the fact that graphene s thermal conductivity always decreases as vacancy defects are introduced.

  19. Through-thickness Membrane Conductivity Measurement for HTM Program: Issues

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    and Approach | Department of Energy Through-thickness Membrane Conductivity Measurement for HTM Program: Issues and Approach Through-thickness Membrane Conductivity Measurement for HTM Program: Issues and Approach DOE HTMWG Meeting, Presented by Kevin Cooper of Scribner Associates, Inc. on September 14, 2006. htmwg_cooper.pdf (566.46 KB) More Documents & Publications Progress and Status on Through-Plane Resistance and Conductivity Measurement of Fuel Cell Membranes High Temperature

  20. Experimental investigation of plastic finned-tube heat exchangers, with emphasis on material thermal conductivity

    SciTech Connect (OSTI)

    Chen, Lin; Li, Zhen; Guo, Zeng-Yuan

    2009-07-15

    In this paper, two modified types of polypropylene (PP) with high thermal conductivity up to 2.3 W/m K and 16.5 W/m K are used to manufacture the finned-tube heat exchangers, which are prospected to be used in liquid desiccant air conditioning, heat recovery, water source heat pump, sea water desalination, etc. A third plastic heat exchanger is also manufactured with ordinary PP for validation and comparison. Experiments are carried out to determine the thermal performance of the plastic heat exchangers. It is found that the plastic finned-tube heat exchanger with thermal conductivity of 16.5 W/m K can achieve overall heat transfer coefficient of 34 W/m{sup 2} K. The experimental results are compared with calculation and they agree well with each other. Finally, the effect of material thermal conductivity on heat exchanger thermal performance is studied in detail. The results show that there is a threshold value of material thermal conductivity. Below this value improving thermal conductivity can considerably improve the heat exchanger performance while over this value improving thermal conductivity contributes very little to performance enhancement. For the finned-tube heat exchanger designed in this paper, when the plastic thermal conductivity can reach over 15 W/m K, it can achieve more than 95% of the titanium heat exchanger performance and 84% of the aluminum or copper heat exchanger performance with the same dimension. (author)

  1. Experimental investigation of the thermal conductivity of porous adsorbents. Master's thesis

    SciTech Connect (OSTI)

    Secary, J.J.

    1989-01-01

    The thermal conductivities of Praseodymium-Cerium-Oxide (PCO) and Saran Carbon have been experimentally investigated using a steady-state heat transfer technique. The investigated substances are used as adsorbents in adsorption compressors being developed for spaceborne refrigeration applications. The objectives of the investigation were to determine the thermal conductivities and establish their temperature dependency. Data were collected for the PCO over a temperature range of 300 C to 600 C, and O (zero) C to 200 C for the Saran Carbon. The thermal conductivities were found to have a strong temperature dependency. In particular, the results for the PCO showed a temperature dependency indicative of some thermal radiation effects.

  2. Magneto thermal conductivity of superconducting Nb with intermediate level of impurity

    SciTech Connect (OSTI)

    L.S. Sharath Chandra, M.K. Chattopadhyay, S.B. Roy, V.C. Sahni, G.R. Myneni

    2012-03-01

    Niobium materials with intermediate purity level are used for fabrication of superconducting radio frequency cavities (SCRF), and thermal conductivity is an important parameter influencing the performance of such SCRF cavities. We report here the temperature and magnetic field dependence of thermal conductivity {kappa} for superconducting niobium (Nb) samples, for which the electron mean free path I{sub e}, the phonon mean free path I{sub g}, and the vortex core diameter 2r{sub C} are of the same order of magnitude. The measured thermal conductivity is analyzed using the effective gap model (developed for I{sub e} >> 2r{sub C} (Dubeck et al 1963 Phys. Rev. Lett. 10 98)) and the normal core model (developed for I{sub e} << 2r{sub C} (Ward and Dew-Hughes 1970 J. Phys. C: Solid St. Phys. 3 2245)). However, it is found that the effective gap model is not suitable for low temperatures when I{sub e} {approx} 2r{sub C}. The normal core model, on the other hand, is able to describe {kappa}(T,H) over the entire temperature range except in the field regime between H{sub C1} and H{sub C2} i.e. in the mixed state. It is shown that to understand the complete behavior of {kappa} in the mixed state, the scattering of quasi-particles from the vortex cores and the intervortex quasi-particle tunneling are to be invoked. The quasi-particle scattering from vortices for the present system is understood in terms of the framework of Sergeenkov and Ausloos (1995 Phys. Rev. B 52 3614) extending their approach to the case of Nb. The intervortex tunneling is understood within the framework of Schmidbauer et al (1970 Z. Phys. 240 30). Analysis of the field dependence of thermal conductivity shows that while the quasi-particle scattering from vortices dominates in the low fields, the intervortex quasi-particle tunneling dominates in high fields. Analysis of the temperature dependence of thermal conductivity shows that while the quasi-particle scattering is dominant at low temperatures, the

  3. Thermal conductivity changes upon neutron transmutation of {sup 10}B doped diamond

    SciTech Connect (OSTI)

    Jagannadham, K., E-mail: jag-kasichainula@ncsu.edu [Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Verghese, K. [Nuclear Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Butler, J. E. [Code 6174, Naval research Laboratory, Washington, District of Columbia 20375 (United States)

    2014-08-28

    {sup 10}B doped p-type diamond samples were subjected to neutron transmutation reaction using thermal neutron flux of 0.9 10{sup 13} cm{sup ?2} s{sup ?1} and fast neutron flux of 0.09 10{sup 13} cm{sup ?2} s{sup ?1}. Another sample of epilayer grown on type IIa (110) single crystal diamond substrate was subjected to equal thermal and fast neutron flux of 10{sup 14}?cm{sup ?2} s{sup ?1}. The defects in the diamond samples were previously characterized by different methods. In the present work, thermal conductivity of these diamond samples was determined at room temperature by transient thermoreflectance method. The thermal conductivity change in the samples as a function of neutron fluence is explained by the phonon scattering from the point defects and disordered regions. The thermal conductivity of the diamond samples decreased more rapidly initially and less rapidly for larger neutron fluence. In addition, the thermal conductivity in type IIb diamond decreased less rapidly with thermal neutron fluence compared to the decrease in type IIa diamond subjected to fast neutron fluence. It is concluded that the rate of production of defects during transmutation reaction is slower when thermal neutrons are used. The thermal conductivity of epilayer of diamond subjected to high thermal and fast neutron fluence is associated with the covalent carbon network in the composite structure consisting of disordered carbon and sp{sup 2} bonded nanocrystalline regions.

  4. Optimizing the transverse thermal conductivity of 2D-SiCf/SiC composites, II. Experimental

    SciTech Connect (OSTI)

    Youngblood, Gerald E; Senor, David J; Jones, Russell H; Kowbel, W

    2002-12-31

    Model predictions of the transverse thermal conductivity (Keff) are compared to experimentally determined values as a function of temperature for a commercial 2D-SiCf/SiC made by DuPont from plain weave Hi-Nicalon fabric and with an ICVI-SiC matrix. Two versions of the DuPont composite were examined: one with a “thin” and one with a “thick” pyrolytic carbon coating of thickness 0.110 m and 1.044 m, respectively. Generally good agreement of the model predictions with measured values of Keff suggest that these models can be used to predict Keff for composites with various “non-ideal” fiber, interphase and matrix structures. Importantly, the models make it possible to separate the relative component contributions to Keff so that individual component degradation mechanisms can be examined in detail. Then, based on specific knowledge of the component degradation, the models can used to predict Keff-values for composites subjected to irradiation, oxidation, thermal cycling, or other thermal or mechanical stress treatments. Finally, model predictions were examined to suggest specific design and/or development efforts directed to optimize the overall thermal transport performance of 2D-SiCf/SiC.

  5. Thermal conduction in lattice–matched superlattices of InGaAs/InAlAs

    SciTech Connect (OSTI)

    Sood, Aditya; Rowlette, Jeremy A.; Caneau, Catherine G.; Bozorg-Grayeli, Elah; Asheghi, Mehdi; Goodson, Kenneth E.

    2014-08-04

    Understanding the relative importance of interface scattering and phonon-phonon interactions on thermal transport in superlattices (SLs) is essential for the simulation of practical devices, such as quantum cascade lasers (QCLs). While several studies have looked at the dependence of the thermal conductivity of SLs on period thickness, few have systematically examined the effect of varying material thickness ratio. Here, we study through-plane thermal conduction in lattice-matched In{sub 0.53}Ga{sub 0.47}As/In{sub 0.52}Al{sub 0.48}As SLs grown by metalorganic chemical vapor deposition as a function of SL period thickness (4.2 to 8.4 nm) and layer thickness ratio (1:3 to 3:1). Conductivities are measured using time-domain thermoreflectance and vary between 1.21 and 2.31 W m{sup −1} K{sup −1}. By studying the trends of the thermal conductivities for large SL periods, we estimate the bulk conductivities of In{sub 0.53}Ga{sub 0.47}As and In{sub 0.52}Al{sub 0.48}As to be approximately 5 W m{sup −1} K{sup −1} and 1 W m{sup −1} K{sup −1}, respectively, the latter being an order of magnitude lower than theoretical estimates. Furthermore, we find that the Kapitza resistance between alloy layers has an upper bound of ≈0.1 m{sup 2} K GW{sup −1}, and is negligible compared to the intrinsic alloy resistances, even for 2 nm thick layers. A phonon Boltzmann transport model yields good agreement with the data when the alloy interfaces are modeled using a specular boundary condition, pointing towards the high-quality of interfaces. We discuss the potential impact of these results on the design and operation of high-power QCLs comprised of In{sub 1−x}Ga{sub x}As/In{sub 1−y}Al{sub y}As SL cores.

  6. Thermal desorption treatability test conducted with VAC*TRAX Unit

    SciTech Connect (OSTI)

    1996-01-01

    In 1992, Congress passed the Federal Facilities Compliance Act, requiring the U.S. Department of Energy (DOE) to treat and dispose of its mixed waste in accordance with Resource Conservation and Recovery Act (RCRA) treatment standards. In response to the need for mixed-waste treatment capacity, where off-site commercial treatment facilities do not exist or cannot be used, the DOE Albuquerque Operations Office (DOE-AL) organized a Treatment Selection Team to match mixed waste with treatment options and develop a strategy for treatment of mixed waste. DOE-AL manages nine sites with mixed-waste inventories. The Treatment Selection Team determined a need to develop mobile treatment units (MTUs) to treat waste at the sites where the wastes are generated. Treatment processes used for mixed wastes must remove the hazardous component (i.e., meet RCRA treatment standards) and contain the radioactive component in a form that will protect the worker, public, and environment. On the basis of the recommendations of the Treatment Selection Team, DOE-AL assigned projects to the sites to bring mixed-waste treatment capacity on-line. The three technologies assigned to the DOE Grand Junction Projects Office (DOE-GJPO) include thermal desorption (TD), evaporative oxidation, and waste water evaporation.

  7. Multiscale modeling of thermal conductivity of high burnup structures in UO2 fuels

    SciTech Connect (OSTI)

    Bai, Xian -Ming; Tonks, Michael R.; Zhang, Yongfeng; Hales, Jason D.

    2015-12-22

    The high burnup structure forming at the rim region in UO2 based nuclear fuel pellets has interesting physical properties such as improved thermal conductivity, even though it contains a high density of grain boundaries and micron-size gas bubbles. To understand this counterintuitive phenomenon, mesoscale heat conduction simulations with inputs from atomistic simulations and experiments were conducted to study the thermal conductivities of a small-grain high burnup microstructure and two large-grain unrestructured microstructures. We concluded that the phonon scattering effects caused by small point defects such as dispersed Xe atoms in the grain interior must be included in order to correctly predict the thermal transport properties of these microstructures. In extreme cases, even a small concentration of dispersed Xe atoms such as 10-5 can result in a lower thermal conductivity in the large-grain unrestructured microstructures than in the small-grain high burnup structure. The high-density grain boundaries in a high burnup structure act as defect sinks and can reduce the concentration of point defects in its grain interior and improve its thermal conductivity in comparison with its large-grain counterparts. Furthermore, an analytical model was developed to describe the thermal conductivity at different concentrations of dispersed Xe, bubble porosities, and grain sizes. Upon calibration, the model is robust and agrees well with independent heat conduction modeling over a wide range of microstructural parameters.

  8. Multiscale modeling of thermal conductivity of high burnup structures in UO2 fuels

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Bai, Xian -Ming; Tonks, Michael R.; Zhang, Yongfeng; Hales, Jason D.

    2015-12-22

    The high burnup structure forming at the rim region in UO2 based nuclear fuel pellets has interesting physical properties such as improved thermal conductivity, even though it contains a high density of grain boundaries and micron-size gas bubbles. To understand this counterintuitive phenomenon, mesoscale heat conduction simulations with inputs from atomistic simulations and experiments were conducted to study the thermal conductivities of a small-grain high burnup microstructure and two large-grain unrestructured microstructures. We concluded that the phonon scattering effects caused by small point defects such as dispersed Xe atoms in the grain interior must be included in order to correctlymore » predict the thermal transport properties of these microstructures. In extreme cases, even a small concentration of dispersed Xe atoms such as 10-5 can result in a lower thermal conductivity in the large-grain unrestructured microstructures than in the small-grain high burnup structure. The high-density grain boundaries in a high burnup structure act as defect sinks and can reduce the concentration of point defects in its grain interior and improve its thermal conductivity in comparison with its large-grain counterparts. Furthermore, an analytical model was developed to describe the thermal conductivity at different concentrations of dispersed Xe, bubble porosities, and grain sizes. Upon calibration, the model is robust and agrees well with independent heat conduction modeling over a wide range of microstructural parameters.« less

  9. First Results of Scanning Thermal Diffusivity Microscope (STDM) Measurements on Irradiated Monolithic and Dispersion Fuel

    SciTech Connect (OSTI)

    T. K. Huber; M. K. Figg; J. R. Kennedy; A. B. Robinson; D. M. Wachs

    2012-07-01

    The thermal conductivity of the fuel material in a reactor before and during irradiation is a sensitive and fundamental parameter for thermal hydraulic calculations that are useds to correctly determine fuel heat fluxes and meat temperatures and to simulate performance of the fuel elements during operation. Several techniques have been developed to measure the thermal properties of fresh fuel to support these calculations, but it is crucial to also investigate the change of thermal properties during irradiation.

  10. THERMAL CONDUCTIVITY OF AQUEOUS NaCl SOLUTIONS

    Office of Scientific and Technical Information (OSTI)

    ... to 25C or 50C for 30 minutes. solution was measured by a differential thermocouple. ... Equations ( 4 ) and ( 5 ) were used i n this work t o reproduce and i n t e r p o l a t e ...

  11. Effect of point defects on the thermal conductivity of UO2: molecular dynamics simulations

    SciTech Connect (OSTI)

    Liu, Xiang-Yang; Stanek, Christopher Richard; Andersson, Anders David Ragnar

    2015-07-21

    The thermal conductivity of uranium dioxide (UO2) fuel is an important materials property that affects fuel performance since it is a key parameter determining the temperature distribution in the fuel, thus governing, e.g., dimensional changes due to thermal expansion, fission gas release rates, etc. [1] The thermal conductivity of UO2 nuclear fuel is also affected by fission gas, fission products, defects, and microstructural features such as grain boundaries. Here, molecular dynamics (MD) simulations are carried out to determine quantitatively, the effect of irradiation induced point defects on the thermal conductivity of UO2, as a function of defect concentrations, for a range of temperatures, 300 – 1500 K. The results will be used to develop enhanced continuum thermal conductivity models for MARMOT and BISON by INL. These models express the thermal conductivity as a function of microstructure state-variables, thus enabling thermal conductivity models with closer connection to the physical state of the fuel [2].

  12. Theoretical investigation of the impact of grain boundaries and fission gases on UO2 thermal conductivity

    SciTech Connect (OSTI)

    Du, Shiyu; Andersson, Anders D.; Germann, Timothy C.; Stanek, Christopher R.

    2012-05-02

    Thermal conductivity is one of the most important metrics of nuclear fuel performance. Therefore, it is crucial to understand the impact of microstructure features on thermal conductivity, especially since the microstructure evolves with burn-up or time in the reactor. For example, UO{sub 2} fuels are polycrystalline and for high-burnup fuels the outer parts of the pellet experience grain sub-division leading to a very fine grain structure. This is known to impact important physical properties such as thermal conductivity as fission gas release. In a previous study, we calculated the effect of different types of {Sigma}5 grain boundaries on UO{sub 2} thermal conductivity and predicted the corresponding Kapitza resistances, i.e. the resistance of the grain boundary in relation to the bulk thermal resistance. There have been reports of pseudoanisotropic effects for the thermal conductivity in cubic polycrystalline materials, as obtained from molecular dynamics simulations, which means that the conductivity appears to be a function of the crystallographic direction of the temperature gradient. However, materials with cubic symmetry should have isotropic thermal conductivity. For this reason it is necessary to determine the cause of this apparent anisotropy and in this report we investigate this effect in context of our earlier simulations of UO{sub 2} Kapitza resistances. Another source of thermal resistance comes from fission products and fission gases. Xe is the main fission gas and when generated in sufficient quantity it dissolves from the lattice and forms gas bubbles inside the crystalline structure. We have performed studies of how Xe atoms dissolved in the UO{sub 2} matrix or precipitated as bubbles impact thermal conductivity, both in bulk UO{sub 2} and in the presence of grain boundaries.

  13. Enhancing through thickness thermal conductivity of ultra-thin composite laminates. Final report

    SciTech Connect (OSTI)

    Ramani, K.; Vaidyanathan, A.

    1994-12-31

    The materials used in electronic applications have specific requirements for stiffness, thermal conductivity, and electromagnetic shielding making the choice of materials used very important. Electronic components are very sensitive to heat, hence the heat dissipation or cooling of the various components is necessary to prevent failure. Thus, any material used in the electronic industry must have a high thermal conductivity in addition to a specified thermal expansion, stiffness and strength properties. The purpose of this project was to design and manufacture composite panels which would conduct heat from an electronic chip attached to the top surface to a cooling liquid flowing at its lower surface. To maximize the heat conducted from the chip to the cooling liquid, the composite must have a high through thickness thermal conductivity. Further, design restrictions on the thickness of the composite panel had to be taken into account. It was found that the presence of excess resin adversely affects the conductivity of a woven fabric composite due to which the through thickness conductivity of the 400 {micro}m thick panel was better than the 500 {micro}m thick panel. The through thickness conductivity of the panel with short fibers alone was better than that of the woven cloth panel. The finite element model developed for a priori prediction of the through thickness thermal conductivity of the composite panels is a very powerful tool that can save enormous prototyping times an associates coats.

  14. Enhancing thermal conductivity of fluids with graphite nanoparticles and carbon nanotube

    DOE Patents [OSTI]

    Zhang, Zhiqiang; Lockwood, Frances E.

    2008-03-25

    A fluid media such as oil or water, and a selected effective amount of carbon nanomaterials necessary to enhance the thermal conductivity of the fluid. One of the preferred carbon nanomaterials is a high thermal conductivity graphite, exceeding that of the neat fluid to be dispersed therein in thermal conductivity, and ground, milled, or naturally prepared with mean particle size less than 500 nm, and preferably less than 200 nm, and most preferably less than 100 nm. The graphite is dispersed in the fluid by one or more of various methods, including ultrasonication, milling, and chemical dispersion. Carbon nanotubes with graphitic structure is another preferred source of carbon nanomaterial, although other carbon nanomaterials are acceptable. To confer long term stability, the use of one or more chemical dispersants is preferred. The thermal conductivity enhancement, compared to the fluid without carbon nanomaterial, is proportional to the amount of carbon nanomaterials (carbon nanotubes and/or graphite) added.

  15. Thermally conductive alumina/organic composites for photovoltaic concentrator cell isolation

    SciTech Connect (OSTI)

    Beavis, L.C.; Panitz, J.K.G.; Sharp, D.J.

    1988-01-01

    Electrophoretically deposited styrene-acrylate films were studied. These yield marginally useful thermal conductivities of 0.1--0.2 watts/meter-Kelvin, but have useful dielectric strengths over 2500 volts for 40 micrometer thick coatings. Thin, 25 micrometer, coatings of anodically grown Al/sub 2/O/sub 3/ films were also investigated. These films have thermal conductivities of approximately 6--8 watts/meter-Kelvin. Although these Al/sub 2/O/sub 3/ films have greater thermal conductivity than the polymer films, they exhibit porosity which typically limits their dielectric strength to less than 1000 volts. In the current study we have determined that styrene-acrylate can be electrophoretically deposited in porous anodic aluminum oxide films to form an alumina-organic composite with improved electrical breakdown strengths as well as higher thermal conductivity than styrene-acrylate films. 7 refs., 2 tabs.

  16. Measurements of prompt radiation induced conductivity of Kapton.

    SciTech Connect (OSTI)

    Preston, Eric F.; Zarick, Thomas Andrew; Sheridan, Timothy J.; Hartman, E. Frederick; Stringer, Thomas Arthur

    2010-10-01

    We performed measurements of the prompt radiation induced conductivity in thin samples of Kapton (polyimide) at the Little Mountain Medusa LINAC facility in Ogden, UT. Three mil samples were irradiated with a 0.5 {mu}s pulse of 20 MeV electrons, yielding dose rates of 1E9 to 1E10 rad/s. We applied variable potentials up to 2 kV across the samples and measured the prompt conduction current. Analysis rendered prompt conductivity coefficients between 6E-17 and 2E-16 mhos/m per rad/s, depending on the dose rate and the pulse width.

  17. Thermal Conductivity in Nanoporous Gold Films during Electron-Phonon Nonequilibrium

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Hopkins, Patrick E.; Norris, Pamela M.; Phinney, Leslie M.; Policastro, Steven A.; Kelly, Robert G.

    2008-01-01

    The reduction of nanodevices has given recent attention to nanoporous materials due to their structure and geometry. However, the thermophysical properties of these materials are relatively unknown. In this article, an expression for thermal conductivity of nanoporous structures is derived based on the assumption that the finite size of the ligaments leads to electron-ligament wall scattering. This expression is then used to analyze the thermal conductivity of nanoporous structures in the event of electron-phonon nonequilibrium.

  18. Record Seebeck coefficient and extremely low thermal conductivity in nanostructured SnSe

    SciTech Connect (OSTI)

    Serrano-Sánchez, F.; Gharsallah, M.; Nemes, N. M.; Mompean, F. J.; Martínez, J. L.; Alonso, J. A.

    2015-02-23

    SnSe has been prepared by arc-melting, as mechanically robust pellets, consisting of highly oriented polycrystals. This material has been characterized by neutron powder diffraction (NPD), scanning electron microscopy, and transport measurements. A microscopic analysis from NPD data demonstrates a quite perfect stoichiometry SnSe{sub 0.98(2)} and a fair amount of anharmonicity of the chemical bonds. The Seebeck coefficient reaches a record maximum value of 668 μV K{sup −1} at 380 K; simultaneously, this highly oriented sample exhibits an extremely low thermal conductivity lower than 0.1 W m{sup −1} K{sup −1} around room temperature, which are two of the main ingredients of good thermoelectric materials. These excellent features exceed the reported values for this semiconducting compound in single crystalline form in the moderate-temperatures region and highlight its possibilities as a potential thermoelectric material.

  19. Size effects on the thermal conductivity of amorphous silicon thin films

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Thomas Edwin Beechem; Braun, Jeffrey L.; Baker, Christopher H.; Elahi, Miraz; Artyushkova, Kateryna; Norris, Pamela M.; Leseman, Zayd Chad; Gaskins, John T.; Hopkins, Patrick E.; Giri, Ashutosh

    2016-04-01

    In this study, we investigate thickness-limited size effects on the thermal conductivity of amorphous silicon thin films ranging from 3 to 1636 nm grown via sputter deposition. While exhibiting a constant value up to ~100 nm, the thermal conductivity increases with film thickness thereafter. The thickness dependence we demonstrate is ascribed to boundary scattering of long wavelength vibrations and an interplay between the energy transfer associated with propagating modes (propagons) and nonpropagating modes (diffusons). A crossover from propagon to diffuson modes is deduced to occur at a frequency of ~1.8 THz via simple analytical arguments. These results provide empirical evidencemore » of size effects on the thermal conductivity of amorphous silicon and systematic experimental insight into the nature of vibrational thermal transport in amorphous solids.« less

  20. Thermal conductivity prediction of magnetic composite sheet for near-field electromagnetic absorption

    SciTech Connect (OSTI)

    Lee, Joonsik; Nam, Baekil; Ko, Frank K.; Kim, Ki Hyeon

    2015-05-07

    The magnetic composite sheets were designed by using core-shell structured magnetic fillers instead of uncoated magnetic fillers to resolve concurrently the electromagnetic interference and thermal radiation problems. To predict the thermal conductivity of composite sheet, we calculated the thermal conductivity of the uncoated magnetic fillers and core-shell structured fillers. And then, the thermal conductivity of the magnetic composites sheet filled with core-shell structured magnetic fillers was calculated and compared with that of the uncoated magnetic fillers filled in composite sheet. The magnetic core and shell material are employed the typical Fe-Al-Si flake (60??m??60??m??1??m) and 250?nm-thick AlN with high thermal conductivity, respectively. The longitudinal thermal conductivity of the core-shell structured magnetic composite sheet (2.45?W/mK) enhanced about 33.4% in comparison with that of uncoated magnetic fillers (1.83?W/mK) for the 50 vol. % magnetic filler in polymer matrix.

  1. Composite material having high thermal conductivity and process for fabricating same

    DOE Patents [OSTI]

    Colella, Nicholas J.; Davidson, Howard L.; Kerns, John A.; Makowiecki, Daniel M.

    1998-01-01

    A process for fabricating a composite material such as that having high thermal conductivity and having specific application as a heat sink or heat spreader for high density integrated circuits. The composite material produced by this process has a thermal conductivity between that of diamond and copper, and basically consists of coated diamond particles dispersed in a high conductivity metal, such as copper. The composite material can be fabricated in small or relatively large sizes using inexpensive materials. The process basically consists, for example, of sputter coating diamond powder with several elements, including a carbide forming element and a brazeable material, compacting them into a porous body, and infiltrating the porous body with a suitable braze material, such as copper-silver alloy, thereby producing a dense diamond-copper composite material with a thermal conductivity comparable to synthetic diamond films at a fraction of the cost.

  2. Composite material having high thermal conductivity and process for fabricating same

    DOE Patents [OSTI]

    Colella, N.J.; Davidson, H.L.; Kerns, J.A.; Makowiecki, D.M.

    1998-07-21

    A process is disclosed for fabricating a composite material such as that having high thermal conductivity and having specific application as a heat sink or heat spreader for high density integrated circuits. The composite material produced by this process has a thermal conductivity between that of diamond and copper, and basically consists of coated diamond particles dispersed in a high conductivity metal, such as copper. The composite material can be fabricated in small or relatively large sizes using inexpensive materials. The process basically consists, for example, of sputter coating diamond powder with several elements, including a carbide forming element and a brazeable material, compacting them into a porous body, and infiltrating the porous body with a suitable braze material, such as copper-silver alloy, thereby producing a dense diamond-copper composite material with a thermal conductivity comparable to synthetic diamond films at a fraction of the cost. 7 figs.

  3. Measurements of prompt radiation induced conductivity in Teflon (PTFE).

    SciTech Connect (OSTI)

    Hartman, E. Frederick; Zarick, Thomas Andrew; Sheridan, Timothy J.; Preston, E.

    2013-05-01

    We performed measurements of the prompt radiation induced conductivity (RIC) in thin samples of Teflon (PTFE) at the Little Mountain Medusa LINAC facility in Ogden, UT. Three mil (76.2 microns) samples were irradiated with a 0.5 %CE%BCs pulse of 20 MeV electrons, yielding dose rates of 1E9 to 1E11 rad/s. We applied variable potentials up to 2 kV across the samples and measured the prompt conduction current. Details of the experimental apparatus and analysis are reported in this report on prompt RIC in Teflon.

  4. Modeling the Influence of Interaction Layer Formation on Thermal Conductivity of UMo Dispersion Fuel

    SciTech Connect (OSTI)

    Burkes, Douglas; Casella, Andrew M.; Huber, Tanja K.

    2015-01-01

    The Global Threat Reduction Initiative Program continues to develop existing and new plate- and rod-type research and test reactor fuels with maximum attainable uranium loadings capable of potentially converting a number of the worlds remaining high-enriched uranium fueled reactors to low-enriched uranium fuel. Currently, the program is focused on assisting with the development and qualification of an even higher density fuel type consisting of a uranium-molybdenum (U-Mo) alloy dispersed in an aluminum matrix. Thermal conductivity is an important consideration in determining the operational temperature of the fuel plate and can be influenced by interaction layer formation between the fuel and matrix, porosity that forms during fabrication of the fuel plates, and upon the concentration of the dispersed phase within the matrix. This paper develops and validates a simple model to study the influence of interaction layer formation and conductivity, fuel particle size, and volume fraction of fuel dispersed in the matrix on the effective conductivity of the composite. The model shows excellent agreement with results previously presented in the literature. In particular, the thermal conductivity of the interaction layer does not appear to be important in determining the overall conductivity of the composite, while formation of the interaction layer and subsequent consumption of the matrix reveals a rather significant effect. The effective thermal conductivity of the composite can be influenced by the fuel particle distribution by minimizing interaction layer formation and preserving the higher thermal conductivity matrix.

  5. Approaching the Minimum Thermal Conductivity in Rhenium-Substituted Higher Manganese Silicides

    SciTech Connect (OSTI)

    Chen, Xi [University of Texas at Austin] [University of Texas at Austin; Girard, S. N. [University of Wisconsin, Madison] [University of Wisconsin, Madison; Meng, F. [University of Wisconsin, Madison] [University of Wisconsin, Madison; Lara-Curzio, Edgar [ORNL] [ORNL; Jin, S [University of Wisconsin, Madison] [University of Wisconsin, Madison; Goodenough, J. B. [University of Texas at Austin] [University of Texas at Austin; Zhou, J. S. [University of Texas at Austin] [University of Texas at Austin; Shi, L [University of Texas at Austin] [University of Texas at Austin

    2014-01-01

    Higher manganese silicides (HMS) made of earth-abundant and non-toxic elements are regarded as promising p-type thermoelectric materials because their complex crystal structure results in low lattice thermal conductivity. It is shown here that the already low thermal conductivity of HMS can be reduced further to approach the minimum thermal conductivity via partial substitu- tion of Mn with heavier rhenium (Re) to increase point defect scattering. The solubility limit of Re in the obtained RexMn1 xSi1.8 is determined to be about x = 0.18. Elemental inhomogeneity and the formation of ReSi1.75 inclusions with 50 200 nm size are found within the HMS matrix. It is found that the power factor does not change markedly at low Re content of x 0.04 before it drops considerably at higher Re contents. Compared to pure HMS, the reduced lattice thermal conductivity in RexMn1 xSi1.8 results in a 25% increase of the peak figure of merit ZT to reach 0.57 0.08 at 800 K for x = 0.04. The suppressed thermal conductivity in the pure RexMn1 xSi1.8 can enable further investigations of the ZT limit of this system by exploring different impurity doping strategies to optimize the carrier concentration and power factor.

  6. Thermal conductivity of cementitious grouts for geothermal heat pumps. Progress report FY 1997

    SciTech Connect (OSTI)

    Allan, M.L.

    1997-11-01

    Grout is used to seal the annulus between the borehole and heat exchanger loops in vertical geothermal (ground coupled, ground source, GeoExchange) heat pump systems. The grout provides a heat transfer medium between the heat exchanger and surrounding formation, controls groundwater movement and prevents contamination of water supply. Enhanced heat pump coefficient of performance (COP) and reduced up-front loop installation costs can be achieved through optimization of the grout thermal conductivity. The objective of the work reported was to characterize thermal conductivity and other pertinent properties of conventional and filled cementitious grouts. Cost analysis and calculations of the reduction in heat exchanger length that could be achieved with such grouts were performed by the University of Alabama. Two strategies to enhance the thermal conductivity of cementitious grouts were used simultaneously. The first of these was to incorporate high thermal conductivity filler in the grout formulations. Based on previous tests (Allan and Kavanaugh, in preparation), silica sand was selected as a suitable filler. The second strategy was to reduce the water content of the grout mix. By lowering the water/cement ratio, the porosity of the hardened grout is decreased. This results in higher thermal conductivity. Lowering the water/cement ratio also improves such properties as permeability, strength, and durability. The addition of a liquid superplasticizer (high range water reducer) to the grout mixes enabled reduction of water/cement ratio while retaining pumpability. Superplasticizers are commonly used in the concrete and grouting industry to improve rheological properties.

  7. Measurements of prompt radiation induced conductivity of alumina and sapphire.

    SciTech Connect (OSTI)

    Hartman, E. Frederick; Zarick, Thomas Andrew; Sheridan, Timothy J.; Preston, Eric F.

    2011-04-01

    We performed measurements of the prompt radiation induced conductivity in thin samples of Alumina and Sapphire at the Little Mountain Medusa LINAC facility in Ogden, UT. Five mil thick samples were irradiated with pulses of 20 MeV electrons, yielding dose rates of 1E7 to 1E9 rad/s. We applied variable potentials up to 1 kV across the samples and measured the prompt conduction current. Analysis rendered prompt conductivity coefficients between 1E10 and 1E9 mho/m/(rad/s), depending on the dose rate and the pulse width for Alumina and 1E7 to 6E7 mho/m/(rad/s) for Sapphire.

  8. Advancing reactive tracer methods for measuring thermal evolution in

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    CO2-and water-based geothermal reservoirs | Department of Energy Advancing reactive tracer methods for measuring thermal evolution in CO2-and water-based geothermal reservoirs Advancing reactive tracer methods for measuring thermal evolution in CO2-and water-based geothermal reservoirs DOE Geothermal Peer Review 2010 - Presentation. This project aims to develop reactive tracer method for monitoring thermal drawdown in enhanced geothermal systems. tracers_hull_thermal_evolution.pdf (852.51

  9. Measuring Thermal Conductivity with Raman:Capability Uncertainty...

    Office of Scientific and Technical Information (OSTI)

    Resource Relation: Conference: IMECE 2012 held November 11-15, 2012 in Houston, TX.; Related Information: Proposed for presentation at the IMECE 2012 held November 11-15, 2012 in ...

  10. Strain Effects in Raman Thermal Conductivity Measurements. (Conference...

    Office of Scientific and Technical Information (OSTI)

    Sciences Conference held October 9-11, 2012 in Atlanta, GA.; Related Information: Proposed for presentation at the Society of Engineering Sciences Conference held October 9-11, ...

  11. Thermal Conductivity Measurements of Silicon Thin Films with...

    Office of Scientific and Technical Information (OSTI)

    Nanoscale Perforations. Abstract not provided. Authors: Harris, Charles Thomas ; Kim, Bongsang ; Reinke, Charles M. ; Hopkins, Patrick Edward ; Olsson, Roy H., ; El-Kady,...

  12. Measurement of thermal conductivity in proton irradiated silicon...

    Office of Scientific and Technical Information (OSTI)

    Resource Type: Journal Article Resource Relation: Journal Name: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and; Journal Volume: ...

  13. Error and Uncertainty in Raman Thermal Conductivity Measurements

    Office of Scientific and Technical Information (OSTI)

    ... This ability not only provides experimental simplification but, more importantly, 26 is imperative for the probing of 2D-solids where any contact with surrounding materials (e.g., ...

  14. Tuning thermal conductivity in homoepitaxial SrTiO{sub 3} films via defects

    SciTech Connect (OSTI)

    Brooks, Charles M.; Wilson, Richard B.; Cahill, David G.; Schäfer, Anna; Schubert, Jürgen; Mundy, Julia A.; Holtz, Megan E.; Muller, David A.; Schlom, Darrell G.

    2015-08-03

    We demonstrate the ability to tune the thermal conductivity of homoepitaxial SrTiO{sub 3} films deposited by reactive molecular-beam epitaxy by varying growth temperature, oxidation environment, and cation stoichiometry. Both point defects and planar defects decrease the longitudinal thermal conductivity (k{sub 33}), with the greatest decrease in films of the same composition observed for films containing planar defects oriented perpendicular to the direction of heat flow. The longitudinal thermal conductivity can be modified by as much as 80%—from 11.5 W m{sup −1}K{sup −1} for stoichiometric homoepitaxial SrTiO{sub 3} to 2 W m{sup −1}K{sup −1} for strontium-rich homoepitaxial Sr{sub 1+δ}TiO{sub x} films—by incorporating (SrO){sub 2} Ruddlesden-Popper planar defects.

  15. Ba-filled Ni–Sb–Sn based skutterudites with anomalously high lattice thermal conductivity

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Paschinger, W.; Rogl, Gerda; Grytsiv, A.; Michor, H.; Heinrich, P. R.; Mueller, H.; Puchegger, S.; Klobes, B.; Hermann, Raphael P.; Reinecker, M.; et al

    2016-06-21

    Here, in this study, novel filled skutterudites BayNi4Sb12-xSnx (ymax = 0.93) have been prepared by arc melting followed by annealing at 250, 350 and 450°C up to 30 days in vacuum-sealed quartz vials. Extension of the homogeneity region, solidus temperatures and structural investigations were performed for the skutterudite phase in the ternary Ni–Sn–Sb and in the quaternary Ba–Ni–Sb–Sn systems. Phase equilibria in the Ni–Sn–Sb system at 450°C were established by means of Electron Probe Microanalysis (EPMA) and X-ray Powder Diffraction (XPD). With rather small cages Ni4(Sb,Sn)12, the Ba–Ni–Sn–Sb skutterudite system is perfectly suited to study the influence of filler atomsmore » on the phonon thermal conductivity. Single-phase samples with the composition Ni4Sb8.2Sn3.8, Ba0.42Ni4Sb8.2Sn3.8 and Ba0.92Ni4Sb6.7Sn5.3 were used to measure their physical properties, i.e. temperature dependent electrical resistivity, Seebeck coefficient and thermal conductivity. The resistivity data demonstrate a crossover from metallic to semiconducting behaviour. The corresponding gap width was extracted from the maxima in the Seebeck coefficient data as a function of temperature. Single crystal X-ray structure analyses at 100, 200 and 300 K revealed the thermal expansion coefficients as well as Einstein and Debye temperatures for Ba0.73Ni4Sb8.1Sn3.9 and Ba0.95Ni4Sb6.1Sn5.9. These data were in accordance with the Debye temperatures obtained from the specific heat (4.4 K < T < 140 K) and Mössbauer spectroscopy (10 K < T < 290 K). Rather small atom displacement parameters for the Ba filler atoms indicate a severe reduction in the “rattling behaviour” consistent with the high levels of lattice thermal conductivity. The elastic moduli, collected from Resonant Ultrasonic Spectroscopy ranged from 100 GPa for Ni4Sb8.2Sn3.8 to 116 GPa for Ba0.92Ni4Sb6.7Sn5.3. The thermal expansion coefficients were 11.8 × 10-6 K-1 for Ni4Sb8.2Sn3.8 and 13.8 × 10-6 K-1 for Ba0.92Ni4

  16. Thermal conductivity of nitride films of Ti, Cr, and W deposited by reactive magnetron sputtering

    SciTech Connect (OSTI)

    Jagannadham, Kasichainula

    2015-05-15

    Nitride films of Ti, Cr, and W were deposited using reactive magnetron sputtering from metal targets in argon and nitrogen plasma. TiN films with (200) orientation were achieved on silicon (100) at the substrate temperature of 500 and 600?C. The films were polycrystalline at lower temperature. An amorphous interface layer was observed between the TiN film and Si wafer deposited at 600?C. TiN film deposited at 600?C showed the nitrogen to Ti ratio to be near unity, but films deposited at lower temperature were nitrogen deficient. CrN film with (200) orientation and good stoichiometry was achieved at 600?C on Si(111) wafer but the film deposited at 500?C showed cubic CrN and hexagonal Cr{sub 2}N phases with smaller grain size and amorphous back ground in the x-ray diffraction pattern. An amorphous interface layer was not observed in the cubic CrN film on Si(111) deposited at 600?C. Nitride film of tungsten deposited at 600?C on Si(100) wafer was nitrogen deficient, contained both cubic W{sub 2}N and hexagonal WN phases with smaller grain size. Nitride films of tungsten deposited at 500?C were nonstoichiometric and contained cubic W{sub 2}N and unreacted W phases. There was no amorphous phase formed along the interface for the tungsten nitride film deposited at 600?C on the Si wafer. Thermal conductivity and interface thermal conductance of all the nitride films of Ti, Cr, and W were determined by transient thermoreflectance technique. The thermal conductivity of the films as function of deposition temperature, microstructure, nitrogen stoichiometry and amorphous interaction layer at the interface was determined. Tungsten nitride film containing both cubic and hexagonal phases was found to exhibit much higher thermal conductivity and interface thermal conductance. The amorphous interface layer was found to reduce effective thermal conductivity of TiN and CrN films.

  17. Assembly for electrical conductivity measurements in the piston cylinder device

    DOE Patents [OSTI]

    Watson, Heather Christine; Roberts, Jeffrey James

    2012-06-05

    An assembly apparatus for measurement of electrical conductivity or other properties of a sample in a piston cylinder device wherein pressure and heat are applied to the sample by the piston cylinder device. The assembly apparatus includes a body, a first electrode in the body, the first electrode operatively connected to the sample, a first electrical conductor connected to the first electrode, a washer constructed of a hard conducting material, the washer surrounding the first electrical conductor in the body, a second electrode in the body, the second electrode operatively connected to the sample, and a second electrical conductor connected to the second electrode.

  18. In situ nanostructure generation and evolution within a bulk thermoelectric material to reduce lattice thermal conductivity.

    SciTech Connect (OSTI)

    Girard, S. N.; He, J.; Li, C.; Moses, S.; Wang, G.; Uher, C.; Dravid, V. P.; Kanatzidis, M. G.

    2010-07-26

    We show experimentally the direct reduction in lattice thermal conductivity as a result of in situ nanostructure generation within a thermoelectric material. Solid solution alloys of the high-performance thermoelectric PbTe-PbS 8% can be synthesized through rapid cooling and subsequent high-temperature activation that induces a spontaneous nucleation and growth of PbS nanocrystals. The emergence of coherent PbS nanostructures reduces the lattice thermal conductivity from {approx}1 to {approx}0.4 W/mK between 400 and 500 K.

  19. Experimental determination of single-crystal halite thermal conductivity, diffusivity and specific heat from -75°C to 300°C

    SciTech Connect (OSTI)

    Urquhart, Alexander; Bauer, Stephen

    2015-05-19

    The thermal properties of halite have broad practical importance, from design and long-term modeling of nuclear waste repositories to analysis and performance assessment of underground natural gas, petroleum and air storage facilities. Using a computer-controlled transient plane source method, single-crystal halite thermal conductivity, thermal diffusivity and specific heat were measured from -75°C to 300°C. These measurements reproduce historical high-temperature experiments and extend the lower temperature extreme into cryogenic conditions. Measurements were taken in 25-degree increments from -75°C to 300°C. Over this temperature range, thermal conductivity decreases by a factor of 3.7, from 9.975 to 2.699 W/mK , and thermal diffusivity decreases by a factor of 3.6, from 5.032 to 1.396 mm²/s. Specific heat does not appear to be temperature dependent, remaining near 2.0 MJ/m³K at all temperatures. This work is intended to develop and expand the existing dataset of halite thermal properties, which are of particular value in defining the parameters of salt storage thermophysical models. The work was motivated by a need for thermal conductivity values in a mixture theory model used to determine bulk thermal conductivity of reconsolidating crushed salt.

  20. Experimental determination of single-crystal halite thermal conductivity, diffusivity and specific heat from -75°C to 300°C

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Urquhart, Alexander; Bauer, Stephen

    2015-05-19

    The thermal properties of halite have broad practical importance, from design and long-term modeling of nuclear waste repositories to analysis and performance assessment of underground natural gas, petroleum and air storage facilities. Using a computer-controlled transient plane source method, single-crystal halite thermal conductivity, thermal diffusivity and specific heat were measured from -75°C to 300°C. These measurements reproduce historical high-temperature experiments and extend the lower temperature extreme into cryogenic conditions. Measurements were taken in 25-degree increments from -75°C to 300°C. Over this temperature range, thermal conductivity decreases by a factor of 3.7, from 9.975 to 2.699 W/mK , and thermal diffusivitymore » decreases by a factor of 3.6, from 5.032 to 1.396 mm²/s. Specific heat does not appear to be temperature dependent, remaining near 2.0 MJ/m³K at all temperatures. This work is intended to develop and expand the existing dataset of halite thermal properties, which are of particular value in defining the parameters of salt storage thermophysical models. The work was motivated by a need for thermal conductivity values in a mixture theory model used to determine bulk thermal conductivity of reconsolidating crushed salt.« less

  1. MESO-SCALE MODELING OF THE INFLUENCE OF INTERGRANULAR GAS BUBBLES ON EFFECTIVE THERMAL CONDUCTIVITY

    SciTech Connect (OSTI)

    Paul C. Millett; Michael Tonks

    2011-06-01

    Using a mesoscale modeling approach, we have investigated how intergranular fission gas bubbles, as observed in high-burnup nuclear fuel, modify the effective thermal conductivity in a polycrystalline material. The calculations reveal that intergranular porosity has a significantly higher resistance to heat transfer compared to randomly-distributed porosity. A model is developed to describe this conductivity reduction that considers an effective grain boundary Kapitza resistance as a function of the fractional coverage of grain boundaries by bubbles.

  2. The role of probe oxide in local surface conductivity measurements

    SciTech Connect (OSTI)

    Barnett, C. J.; Kryvchenkova, O.; Wilson, L. S. J.; Maffeis, T. G. G.; Cobley, R. J.; Kalna, K.

    2015-05-07

    Local probe methods can be used to measure nanoscale surface conductivity, but some techniques including nanoscale four point probe rely on at least two of the probes forming the same low resistivity non-rectifying contact to the sample. Here, the role of probe shank oxide has been examined by carrying out contact and non-contact I V measurements on GaAs when the probe oxide has been controllably reduced, both experimentally and in simulation. In contact, the barrier height is pinned but the barrier shape changes with probe shank oxide dimensions. In non-contact measurements, the oxide modifies the electrostatic interaction inducing a quantum dot that alters the tunneling behavior. For both, the contact resistance change is dependent on polarity, which violates the assumption required for four point probe to remove probe contact resistance from the measured conductivity. This has implications for all nanoscale surface probe measurements and macroscopic four point probe, both in air and vacuum, where the role of probe oxide contamination is not well understood.

  3. Optimizing the transverse thermal conductivity of 2D-SiCf/SiC composites, I. Modeling

    SciTech Connect (OSTI)

    Youngblood, Gerald E.; Senor, David J.; Jones, Russell H.

    2002-12-31

    For potential fusion applications, considerable fabrication efforts have been directed to obtaining transverse thermal conductivity (Keff) values in excess of 30 W/mK (unirradiated) in the 800-1000°C temperature range for 2D-SiCf/SiC composites. To gain insight into the factors affecting Keff, at PNNL we have tested three different analytic models for predicting Keff in terms of constituent (fiber, matrix and interphase) properties. The tested models were: the Hasselman-Johnson (H-J) “2-Cylinder” model, which examines the effects of fiber-matrix (f/m) thermal barriers; the Markworth “3-Cylinder” model, which specifically examines the effects of interphase thickness and thermal conductivity; and a newly-developed Anisotropic “3-Square” model, which examines the potential effect of introducing a fiber coating with anisotropic properties to enhance (or diminish) f/m thermal coupling. The first two models are effective medium models, while the third model is a simple combination of parallel and series conductances. Model predictions suggest specific designs and/or development efforts directed to optimize the overall thermal transport performance of 2D-SiCf/SiC.

  4. Imaging thermal conductivity with nanoscale resolution using a scanning spin probe

    SciTech Connect (OSTI)

    Laraoui, Abdelghani; Aycock-Rizzo, Halley; Gao, Yang; Lu, Xi; Riedo, Elisa; Meriles, Carlos A.

    2015-11-20

    The ability to probe nanoscale heat flow in a material is often limited by lack of spatial resolution. Here, we use a diamond-nanocrystal-hosted nitrogen-vacancy centre attached to the apex of a silicon thermal tip as a local temperature sensor. We apply an electrical current to heat up the tip and rely on the nitrogen vacancy to monitor the thermal changes the tip experiences as it is brought into contact with surfaces of varying thermal conductivity. By combining atomic force and confocal microscopy, we image phantom microstructures with nanoscale resolution, and attain excellent agreement between the thermal conductivity and topographic maps. The small mass and high thermal conductivity of the diamond host make the time response of our technique short, which we demonstrate by monitoring the tip temperature upon application of a heat pulse. Our approach promises multiple applications, from the investigation of phonon dynamics in nanostructures to the characterization of heterogeneous phase transitions and chemical reactions in various solid-state systems.

  5. Imaging thermal conductivity with nanoscale resolution using a scanning spin probe

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Laraoui, Abdelghani; Aycock-Rizzo, Halley; Gao, Yang; Lu, Xi; Riedo, Elisa; Meriles, Carlos A.

    2015-11-20

    The ability to probe nanoscale heat flow in a material is often limited by lack of spatial resolution. Here, we use a diamond-nanocrystal-hosted nitrogen-vacancy centre attached to the apex of a silicon thermal tip as a local temperature sensor. We apply an electrical current to heat up the tip and rely on the nitrogen vacancy to monitor the thermal changes the tip experiences as it is brought into contact with surfaces of varying thermal conductivity. By combining atomic force and confocal microscopy, we image phantom microstructures with nanoscale resolution, and attain excellent agreement between the thermal conductivity and topographic maps.more » The small mass and high thermal conductivity of the diamond host make the time response of our technique short, which we demonstrate by monitoring the tip temperature upon application of a heat pulse. Our approach promises multiple applications, from the investigation of phonon dynamics in nanostructures to the characterization of heterogeneous phase transitions and chemical reactions in various solid-state systems.« less

  6. Thermal battery. [solid metal halide electrolytes with enhanced electrical conductance after a phase transition

    DOE Patents [OSTI]

    Carlsten, R.W.; Nissen, D.A.

    1973-03-06

    The patent describes an improved thermal battery whose novel design eliminates various disadvantages of previous such devices. Its major features include a halide cathode, a solid metal halide electrolyte which has a substantially greater electrical conductance after a phase transition at some temperature, and a means for heating its electrochemical cells to activation temperature.

  7. First-principles investigations on ionization and thermal conductivity of polystyrene for inertial confinement fusion applications

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Hu, S. X.; Collins, L. A.; Goncharov, V. N.; Kress, J. D.; McCrory, R. L.; Skupsky, S.

    2016-04-14

    Using quantum molecular-dynamics (QMD) methods based on the density functional theory, we have performed first-principles investigations on the ionization and thermal conductivity of polystyrene (CH) over a wide range of plasma conditions (ρ = 0.5 to 100 g/cm3 and T = 15,625 to 500,000 K). The ionization data from orbital-free molecular-dynamics calculations have been fitted with a “Saha-type” model as a function of the CH plasma density and temperature, which exhibits the correct behaviors of continuum lowering and pressure ionization. The thermal conductivities (κQMD) of CH, derived directly from the Kohn–Sham molecular-dynamics calculations, are then analytically fitted with a generalizedmore » Coulomb logarithm [(lnΛ)QMD] over a wide range of plasma conditions. When compared with the traditional ionization and thermal conductivity models used in radiation–hydrodynamics codes for inertial confinement fusion simulations, the QMD results show a large difference in the low-temperature regime in which strong coupling and electron degeneracy play an essential role in determining plasma properties. Furthermore, hydrodynamic simulations of cryogenic deuterium–tritium targets with CH ablators on OMEGA and the National Ignition Facility using the QMD-derived ionization and thermal conductivity of CH have predicted –20% variation in target performance in terms of hot-spot pressure and neutron yield (gain) with respect to traditional model simulations.« less

  8. Asymptotic regimes for the electrical and thermal conductivities in dense plasmas

    SciTech Connect (OSTI)

    Faussurier, G. Blancard, C.

    2015-04-15

    We study the asymptotic regimes for the electrical and thermal conductivities in dense plasmas obtained by combining the Chester–Thellung–Kubo–Greenwood approach and the Kramers approximation [Faussurier et al., Phys. Plasmas 21, 092706 (2014)]. Non-degenerate and degenerate situations are considered. The Wiedemann–Franz law is obtained in the degenerate case.

  9. Microstructure changes and thermal conductivity reduction in UO2 following 3.9 MeV He2+ ion irradiation

    SciTech Connect (OSTI)

    Janne Pakrinen; Marat Khafizov; Lingfeng He; Chris Wetland; Jian Gan; Andrew T. Nelson; David H Hurley; Anter El-Azab; Todd R Allen

    2014-11-01

    The microstructural changes and associated effects on thermal conductivity were examined in UO2 after irradiation using 3.9 MeV He2+ ions. Lattice expansion of UO2 was observed in x-ray diffraction after ion irradiation up to 5×1016 He2+/cm2 at low-temperature (< 200 °C). Transmission electron microscopy (TEM) showed homogenous irradiation damage across an 8 µm thick plateau region, which consisted of small dislocation loops accompanied by dislocation segments. Dome-shaped blisters were observed at the peak damage region (depth around 8.5 µm) in the sample subjected to 5×1016 He2+/cm2, the highest fluence reached, while similar features were not detected at 9×1015 He2+/cm2. Laser-based thermo-reflectance measurements showed that the thermal conductivity for the irradiated layer decreased about 55 % for the high fluence sample and 35% for the low fluence sample as compared to an un-irradiated reference sample. Detailed analysis for the thermal conductivity indicated that the conductivity reduction was caused by the irradiation induced point defects.

  10. Estimates of crystalline LiF thermal conductivity at high temperature and pressure by a Green-Kubo method

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Jones, R. E.; Ward, D. K.

    2016-07-18

    Here, given the unique optical properties of LiF, it is often used as an observation window in high-temperature and -pressure experiments; hence, estimates of its transmission properties are necessary to interpret observations. Since direct measurements of the thermal conductivity of LiF at the appropriate conditions are difficult, we resort to molecular simulation methods. Using an empirical potential validated against ab initio phonon density of states, we estimate the thermal conductivity of LiF at high temperatures (1000–4000 K) and pressures (100–400 GPa) with the Green-Kubo method. We also compare these estimates to those derived directly from ab initio data. To ascertainmore » the correct phase of LiF at these extreme conditions, we calculate the (relative) phase stability of the B1 and B2 structures using a quasiharmonic ab initio model of the free energy. We also estimate the thermal conductivity of LiF in an uniaxial loading state that emulates initial stages of compression in high-stress ramp loading experiments and show the degree of anisotropy induced in the conductivity due to deformation.« less

  11. First-principles prediction of phononic thermal conductivity of silicene: A comparison with graphene

    SciTech Connect (OSTI)

    Gu, Xiaokun; Yang, Ronggui

    2015-01-14

    There has been great interest in two-dimensional materials, beyond graphene, for both fundamental sciences and technological applications. Silicene, a silicon counterpart of graphene, has been shown to possess some better electronic properties than graphene. However, its thermal transport properties have not been fully studied. In this paper, we apply the first-principles-based phonon Boltzmann transport equation to investigate the thermal conductivity of silicene as well as the phonon scattering mechanisms. Although both graphene and silicene are two-dimensional crystals with similar crystal structure, we find that phonon transport in silicene is quite different from that in graphene. The thermal conductivity of silicene shows a logarithmic increase with respect to the sample size due to the small scattering rates of acoustic in-plane phonon modes, while that of graphene is finite. Detailed analysis of phonon scattering channels shows that the linear dispersion of the acoustic out-of-plane (ZA) phonon modes, which is induced by the buckled structure, makes the long-wavelength longitudinal acoustic phonon modes in silicene not as efficiently scattered as that in graphene. Compared with graphene, where most of the heat is carried by the acoustic out-of-plane (ZA) phonon modes, the ZA phonon modes in silicene only have ?10% contribution to the total thermal conductivity, which can also be attributed to the buckled structure. This systematic comparison of phonon transport and thermal conductivity of silicene and graphene using the first-principle-based calculations shed some light on other two-dimensional materials, such as two-dimensional transition metal dichalcogenides.

  12. Development of Innovative Accident Tolerant High Thermal Conductivity UO2-Diamond Composite Fuel Pellets

    SciTech Connect (OSTI)

    Tulenko, James; Subhash, Ghatu

    2016-01-01

    The University of Florida (UF) evaluated a composite fuel consisting of UO2 powder mixed with diamond micro particles as a candidate as an accident-tolerant fuel (ATF). The research group had previous extensive experience researching with diamond micro particles as an addition to reactor coolant for improved plant thermal performance. The purpose of this research work was to utilize diamond micro particles to develop UO2-Diamond composite fuel pellets with significantly enhanced thermal properties, beyond that already being measured in the previous UF research projects of UO2 – SiC and UO2 – Carbon Nanotube fuel pins. UF is proving with the current research results that the addition of diamond micro particles to UO2 may greatly enhanced the thermal conductivity of the UO2 pellets producing an accident-tolerant fuel. The Beginning of life benefits have been proven and fuel samples are being irradiated in the ATR reactor to confirm that the thermal conductivity improvements are still present under irradiation.

  13. Analytical evaluation of thermal conductance and heat capacities of one-dimensional material systems

    SciTech Connect (OSTI)

    Saygi, Salih

    2014-02-15

    We theoretically predict some thermal properties versus temperature dependence of one dimensional (1D) material nanowire systems. A known method is used to provide an efficient and reliable analytical procedure for wide temperature range. Predicted formulas are expressed in terms of Bloch-Grneisen functions and Debye functions. Computing results has proved that the expressions are in excellent agreement with the results reported in the literature even if it is in very low dimension limits of nanowire systems. Therefore the calculation method is a fully predictive approach to calculate thermal conductivity and heat capacities of nanowire material systems.

  14. Effects of subconduction band excitations on thermal conductance at metal-metal interfaces

    SciTech Connect (OSTI)

    Hopkins, Patrick E.; Beechem, Thomas E.; Duda, John C.; Smoyer, Justin L.; Norris, Pamela M.

    2010-01-04

    Increased power densities combined with the decreased length scales of nanosystems give rise to large thermal excitations that can drastically affect the electron population near the Fermi surface. In light of such conditions, a model is developed for electron thermal boundary conductance (eTBC) that accounts for significant changes in the electron and hole populations around the Fermi level that occur at heightened temperatures. By including the contribution of subconduction band electrons to transport and evaluating the transmission coefficient based upon the total number of available states, an extension of eTBC predictions to high temperatures is made possible.

  15. Unglazed transpired solar collector having a low thermal-conductance absorber

    DOE Patents [OSTI]

    Christensen, C.B.; Kutscher, C.F.; Gawlik, K.M.

    1997-12-02

    An unglazed transpired solar collector using solar radiation to heat incoming air for distribution, comprises an unglazed absorber formed of low thermal-conductance material having a front surface for receiving the solar radiation and openings in the unglazed absorber for passage of the incoming air such that the incoming air is heated as it passes towards the front surface of the absorber and the heated air passes through the openings in the absorber for distribution. 3 figs.

  16. High thermal conductivity lossy dielectric using co-densified multilayer configuration

    DOE Patents [OSTI]

    Tiegs, Terry N.; Kiggans, Jr., James O.

    2003-06-17

    Systems and methods are described for loss dielectrics. A method of manufacturing a lossy dielectric includes providing at least one high dielectric loss layer and providing at least one high thermal conductivity-electrically insulating layer adjacent the at least one high dielectric loss layer and then densifying together. The systems and methods provide advantages because the lossy dielectrics are less costly and more environmentally friendly than the available alternatives.

  17. Unglazed transpired solar collector having a low thermal-conductance absorber

    DOE Patents [OSTI]

    Christensen, Craig B.; Kutscher, Charles F.; Gawlik, Keith M.

    1997-01-01

    An unglazed transpired solar collector using solar radiation to heat incoming air for distribution, comprising an unglazed absorber formed of low thermal-conductance material having a front surface for receiving the solar radiation and openings in the unglazed absorber for passage of the incoming air such that the incoming air is heated as it passes towards the front surface of the absorber and the heated air passes through the openings in the absorber for distribution.

  18. Atomistic study of porosity impact on phonon driven thermal conductivity: Application to uranium dioxide

    SciTech Connect (OSTI)

    Colbert, Mehdi; Ribeiro, Fabienne; Trglia, Guy

    2014-01-21

    We present here an analytical method, based on the kinetic theory, to determine the impact of defects such as cavities on the thermal conductivity of a solid. This approach, which explicitly takes into account the effects of internal pore surfaces, will be referred to as the Phonon Interface THermal cONductivity (PITHON) model. Once exposed in the general case, this method is then illustrated in the case of uranium dioxide. It appears that taking properly into account these interface effects significantly modifies the temperature and porosity dependence of thermal conductivity with respect to that issued from either micromechanical models or more recent approaches, in particular, for small cavity sizes. More precisely, it is found that if the mean free path appears to have a major effect in this system in the temperature and porosity distribution range of interest, the variation of the specific heat at the surface of the cavity is predicted to be essential at very low temperature and small sizes for sufficiently large porosity.

  19. ELECTRON THERMAL CONDUCTION AS A POSSIBLE PHYSICAL MECHANISM TO MAKE THE INNER HELIOSHEATH THINNER

    SciTech Connect (OSTI)

    Izmodenov, V. V. [Department of Mechanics and Mathematics, Lomonosov Moscow State University, 1 Leninskie gory, Moscow, 119991 (Russian Federation); Alexashov, D. B.; Ruderman, M. S., E-mail: izmod@ipmnet.ru [Space Research Institute (IKI) of Russian Academy of Sciences, 84/32 Profsoyuznaya Street, Moscow, 117997 (Russian Federation)

    2014-11-01

    We show that electron thermal conductivity may strongly affect the heliosheath plasma flow and the global pattern of the solar wind's interaction with the local interstellar medium. In particular, it leads to strong reduction of the inner heliosheath thickness, which makes it possible to explain (qualitatively) why Voyager 1 (V1) has crossed the heliopause at an unexpectedly small heliocentric distance of 122 AU. To estimate the effect of thermal conductivity, we consider a limiting case when thermal conduction is very effective. To do that, we assume the plasma flow in the entire heliosphere is nearly isothermal. Due to this effect, the heliospheric distance of the termination shock has increased by about 15 AU in the V1 direction compared with the adiabatic case with ? = 5/3. The heliospheric distance of the heliopause has decreased by about 27 AU. As a result, the thickness of the inner heliosheath in the model has decreased by about 42 AU and has become equal to 32 AU.

  20. Unusual Enhancement in Intrinsic Thermal Conductivity of Multilayer Graphene by Tensile Strains

    SciTech Connect (OSTI)

    Kuang, Youdi; Lindsay, Lucas R.; Huang, Baoling

    2015-01-01

    High basal plane thermal conductivity k of multi-layer graphene makes it promising for thermal management applications. Here we examine the effects of tensile strain on thermal transport in this system. Using a first principles Boltzmann-Peierls equation for phonon transport approach, we calculate the room-temperature in-plane lattice k of multi-layer graphene (up to four layers) and graphite under different isotropic tensile strains. The calculated in-plane k of graphite, finite mono-layer graphene and 3-layer graphene agree well with previous experiments. The dimensional transitions of the intrinsic k and the extent of the diffusive transport regime from mono-layer graphene to graphite are presented. We find a peak enhancement of intrinsic k for multi-layer graphene and graphite with increasing strain and the largest enhancement amplitude is about 40%. In contrast the calculated intrinsic k with tensile strain decreases for diamond and diverges for graphene, we show that the competition between the decreased mode heat capacities and the increased lifetimes of flexural phonons with increasing strain contribute to this k behavior. Similar k behavior is observed for 2-layer hexagonal boron nitride systems, suggesting that it is an inherent thermal transport property in multi-layer systems assembled of purely two dimensional atomic layers. This study provides insights into engineering k of multi-layer graphene and boron nitride by strain and into the nature of thermal transport in quasi-two-dimensional and highly anisotropic systems.

  1. Effects of Contact Resistance on Electrical Conductivity Measurements of SiC-Based Materials

    SciTech Connect (OSTI)

    Youngblood, Gerald E.; Thomsen, Edwin C.; Henager, Charles H.

    2012-04-17

    A combination 2/4-probe method was used to measure electrical resistances across a pure, monolithic CVD-SiC disc sample with contact resistance at the SiC/metallic electrode interfaces. By comparison of the almost simultaneous 2/4-probe measurements, the specific contact resistance and its temperature dependence were determined for two types (sputtered gold and porous nickel) electrodes from RT to ~700C. The specific contact resistance values (Rc) behaved similarly for each type of metallic electrode: Rc >~1000 ?-cm2 at RT, decreasing continuously to ~1-10 ?-cm2 at 700C. The temperature dependence of the inverse Rc indicated thermally activated electrical conduction across the SiC/metallic interface with an apparent activation energy of ~0.3 eV. For the flow channel insert application in a fusion reactor blanket, contact resistance potentially could reduce the transverse electrical conductivity by ~1/2.

  2. Effects of contact resistance on electrical conductivity measurements of SiC-based materials

    SciTech Connect (OSTI)

    Youngblood, Gerald E.; Thomsen, Edwin C.; Henager, Charles H.

    2013-06-30

    A combination 2/4-probe method was used to measure electrical resistances across a pure, monolithic CVD-SiC disc sample with contact resistance at the SiC/metallic electrode interfaces. By comparison of the almost simultaneous 2/4-probe measurements, the specific contact resistance (Rc) and its temperature dependence were determined for two types (sputtered gold and porous nickel) electrodes from room temperature (RT) to ?973 K. The Rc-values behaved similarly for each type of metallic electrode: Rc > ?1000 ? cm2 at RT, decreasing continuously to ?110 ? cm2 at 973 K. The temperature dependence of the inverse Rc indicated thermally activated electrical conduction across the SiC/metallic interface with an apparent activation energy of ?0.3 eV. For the flow channel insert application in a fusion reactor blanket, contact resistance potentially could reduce the transverse electrical conductivity by about 50%.

  3. Prediction and measurement of thermal transport across interfaces between isotropic solids and graphitic materials.

    SciTech Connect (OSTI)

    Hopkins, Patrick E.; Norris, Pamela M.; Smoyer, Justin L.; Duda, John C.

    2010-06-01

    Due to the high intrinsic thermal conductivity of carbon allotropes, there have been many attempts to incorporate such structures into existing thermal abatement technologies. In particular, carbon nanotubes (CNTs) and graphitic materials (i.e., graphite and graphene flakes or stacks) have garnered much interest due to the combination of both their thermal and mechanical properties. However, the introduction of these carbon-based nanostructures into thermal abatement technologies greatly increases the number of interfaces per unit length within the resulting composite systems. Consequently, thermal transport in these systems is governed as much by the interfaces between the constituent materials as it is by the materials themselves. This paper reports the behavior of phononic thermal transport across interfaces between isotropic thin films and graphite substrates. Elastic and inelastic diffusive transport models are formulated to aid in the prediction of conductance at a metal-graphite interface. The temperature dependence of the thermal conductance at Au-graphite interfaces is measured via transient thermoreflectance from 78 to 400 K. It is found that different substrate surface preparations prior to thin film deposition have a significant effect on the conductance of the interface between film and substrate.

  4. Design and calibration of a test facility for MLI thermal performance measurements below 80K

    SciTech Connect (OSTI)

    Boroski, W.; Kunzelman, R.; Ruschman, M.; Schoo, C.

    1992-04-01

    The design geometry of the SSC dipole cryostat includes active thermal radiation shields operating at 80K and 20K respectively. Extensive measurements conducted in a Heat Leak Test Facility (HLTF) have been used to evaluate the thermal performance of candidate multilayer insulation (MLI) systems for the 80K thermal shield, with the present system design based upon those measurement results. With the 80K MLI geometry established, efforts have focused on measuring the performance of MLI systems near 20K. A redesign of the HLTF has produced a measurement facility capable of conducting measurements with the warm boundary fixed at 80K and the cold boundary variable from 10K to 50K. Removing the 80K shield permits measurements with a warm boundary at 300K. The 80K boundary consists of a copper shield thermally anchored to a liquid nitrogen reservoir. The cold boundary consists of a copper anchor plate whose temperature is varied through boil-off gas from a 500 liter helium supply dewar. A transfer line heat exchanger supplies the boil-off gas to the anchor plate at a constant and controlled rate. The gas, which serves as cooling gas, is routed through a copper cooling tube soldered into the anchor plate. Varying the cooling gas flow rate varies the amount of refrigeration supplied to the anchor plate, thereby determining the plate temperature. A resistance heater installed on the anchor plate is regulated by a cryogenic temperature controller to provide final temperature control. Heat leak values are measured using a heatmeter which senses heat flow as a temperature gradient across a fixed thermal impedance. Since the thermal conductivity of the thermal impedance changes with temperature, the heatmeter is calibrated at key cold boundary temperatures. Thus, the system is capable of obtaining measurement data under a variety of system conditions. 7 refs.

  5. Method for measuring thermal properties using a long-wavelength infrared thermal image

    DOE Patents [OSTI]

    Walker, Charles L.; Costin, Laurence S.; Smith, Jody L.; Moya, Mary M.; Mercier, Jeffrey A.

    2007-01-30

    A method for estimating the thermal properties of surface materials using long-wavelength thermal imagery by exploiting the differential heating histories of ground points in the vicinity of shadows. The use of differential heating histories of different ground points of the same surface material allows the use of a single image acquisition step to provide the necessary variation in measured parameters for calculation of the thermal properties of surface materials.

  6. The Envelope Thermal Test Unit (ETTU): Full Measurement of WallPerform ance

    SciTech Connect (OSTI)

    Sonderegger, R.C.; Sherman, M.H.; Adams, J.W.

    1981-10-01

    There are many ways of calculating the dynamic thermal performance of walls and many ways of measuring the performance of walls in the laboratory, relatively few field measurements have been made of the dynamic performance of wall in situ. Measuring the thermal performance of walls in situ poses two separate problems: measuring the heat fluxes and surface temperatures of the wall, and reducing this data set into usable parameters. We have solved the first problem by developing the Envelope Thermal Test Unit (ETTU). ETTU consists of two specially constructed polystyrene blankets, 1.2m square, placed on either side of the test wall that both control and measure the surface fluxes and surface temperatures of the wall. To solve the second problem we have developed a simplified dynamic model that describes the thermal performance of a wall in terms of its steady-state conductance, a time constant, and some storage terms. We have used ETTU in the field to measure the thermal performance of walls, and have applied our simplified analysis to calculate simplified thermal parameters from this data set. In this report, we present the in-situ measurements made to date using ETTU, and the resulting model predictions. The agreement between measured and predicted surface fluxes demonstrates the ability of our test unit and analytic model to describe the dynamic performance of walls in situ.

  7. A Low Hysteresis NiTiFe Shape Memory Alloy Based Thermal Conduction Switch

    SciTech Connect (OSTI)

    Lemanski, J. L.; Krishnan, V. B.; Manjeri, R. Mahadevan; Vaidyanathan, R.; Notardonato, W. U.

    2006-03-31

    Shape memory alloys possess the ability to return to a preset shape by undergoing a solid state phase transformation at a particular temperature. This work reports on the development and testing of a low temperature thermal conduction switch that incorporates a NiTiFe shape memory element for actuation. The switch was developed to provide a variable conductive pathway between liquid methane and liquid oxygen dewars in order to passively regulate the temperature of methane. The shape memory element in the switch undergoes a rhombohedral or R-phase transformation that is associated with a small hysteresis (typically 1-2 deg. C) and offers the advantage of precision control over a set temperature range. For the NiTiFe alloy used, its thermomechanical processing, subsequent characterization using dilatometry, differential scanning calorimetry and implementation in the conduction switch configuration are addressed.

  8. Crossover behavior of the thermal conductance and Kramers’ transition rate theory

    SciTech Connect (OSTI)

    Velizhanin, Kirill A.; Sahu, Subin; Chien, Chih -Chun; Dubi, Yonatan; Zwolak, Michael

    2015-12-04

    Kramers’ theory frames chemical reaction rates in solution as reactants overcoming a barrier in the presence of friction and noise. For weak coupling to the solution, the reaction rate is limited by the rate at which the solution can restore equilibrium after a subset of reactants have surmounted the barrier to become products. For strong coupling, there are always sufficiently energetic reactants. However, the solution returns many of the intermediate states back to the reactants before the product fully forms. Here, we demonstrate that the thermal conductance displays an analogous physical response to the friction and noise that drive the heat current through a material or structure. A crossover behavior emerges where the thermal reservoirs dominate the conductance at the extremes and only in the intermediate region are the intrinsic properties of the lattice manifest. Finally, not only does this shed new light on Kramers’ classic turnover problem, this result is significant for the design of devices for thermal management and other applications, as well as the proper simulation of transport at the nanoscale.

  9. Crossover behavior of the thermal conductance and Kramers’ transition rate theory

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Velizhanin, Kirill A.; Sahu, Subin; Chien, Chih -Chun; Dubi, Yonatan; Zwolak, Michael

    2015-12-04

    Kramers’ theory frames chemical reaction rates in solution as reactants overcoming a barrier in the presence of friction and noise. For weak coupling to the solution, the reaction rate is limited by the rate at which the solution can restore equilibrium after a subset of reactants have surmounted the barrier to become products. For strong coupling, there are always sufficiently energetic reactants. However, the solution returns many of the intermediate states back to the reactants before the product fully forms. Here, we demonstrate that the thermal conductance displays an analogous physical response to the friction and noise that drive themore » heat current through a material or structure. A crossover behavior emerges where the thermal reservoirs dominate the conductance at the extremes and only in the intermediate region are the intrinsic properties of the lattice manifest. Finally, not only does this shed new light on Kramers’ classic turnover problem, this result is significant for the design of devices for thermal management and other applications, as well as the proper simulation of transport at the nanoscale.« less

  10. Unusual Enhancement in Intrinsic Thermal Conductivity of Multilayer Graphene by Tensile Strains

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Kuang, Youdi; Lindsay, Lucas R.; Huang, Baoling

    2015-01-01

    High basal plane thermal conductivity k of multi-layer graphene makes it promising for thermal management applications. Here we examine the effects of tensile strain on thermal transport in this system. Using a first principles Boltzmann-Peierls equation for phonon transport approach, we calculate the room-temperature in-plane lattice k of multi-layer graphene (up to four layers) and graphite under different isotropic tensile strains. The calculated in-plane k of graphite, finite mono-layer graphene and 3-layer graphene agree well with previous experiments. The dimensional transitions of the intrinsic k and the extent of the diffusive transport regime from mono-layer graphene to graphite are presented.more » We find a peak enhancement of intrinsic k for multi-layer graphene and graphite with increasing strain and the largest enhancement amplitude is about 40%. In contrast the calculated intrinsic k with tensile strain decreases for diamond and diverges for graphene, we show that the competition between the decreased mode heat capacities and the increased lifetimes of flexural phonons with increasing strain contribute to this k behavior. Similar k behavior is observed for 2-layer hexagonal boron nitride systems, suggesting that it is an inherent thermal transport property in multi-layer systems assembled of purely two dimensional atomic layers. This study provides insights into engineering k of multi-layer graphene and boron nitride by strain and into the nature of thermal transport in quasi-two-dimensional and highly anisotropic systems.« less

  11. Simplified models of growth, defect formation, and thermal conductivity in diamond chemical vapor deposition

    SciTech Connect (OSTI)

    Coltrin, M.E.; Dandy, D.S.

    1996-04-01

    A simplified surface reaction mechanism is presented for the CVD of diamond thin films. The mechanism also accounts for formation of point defects in the diamond lattice, an alternate, undesirable reaction pathway. Both methyl radicals and atomic C are considered as growth precursors. While not rigorous in all details, the mechanism is useful in describing the CVD diamond process over a wide range of reaction conditions. It should find utility in reactor modeling studies, for example in optimizing diamond growth rate while minimizing defect formation. This report also presents a simple model relating the diamond point-defect density to the thermal conductivity of the material.

  12. Fabrication of high thermal conductivity arrays of carbon nanotubes and their composites

    DOE Patents [OSTI]

    Geohegan, David B. (Knoxville, TN) [Knoxville, TN; Ivanov, Ilya N. (Knoxville, TN) [Knoxville, TN; Puretzky, Alexander A [Knoxville, TN

    2010-07-27

    Methods and apparatus are described for fabrication of high thermal conductivity arrays of carbon nanotubes and their composites. A composition includes a vertically aligned nanotube array including a plurality of nanotubes characterized by a property across substantially all of the vertically aligned nanotube array. A method includes depositing a vertically aligned nanotube array that includes a plurality of nanotubes; and controlling a deposition rate of the vertically aligned nanotubes array as a function of an in situ monitored property of the plurality of nanotubes.

  13. FUEL PERFORMANCE IMPROVEMENT PROGRAM Thermal Conductivity of Sphere-Pac Fuel

    SciTech Connect (OSTI)

    Ades, M. J.

    1981-07-01

    Progress in understanding the thermal conductivity of sphere-pac fuel beds has been made both at Oregon State University and Exxon Nuclear Company supported by the Fuel Performance Improvement Program (FPIP). FPIP is sponsored by the U. S. Department of Energy and is being performed by Consumers Power Company, Exxon Nuclear Company, and Pacific Northwest Laboratory. The purpose of the program is to test and demonstrate improved li9ht water reactor fuel concepts that are more resistant to failure from pellet-cladding interaction during power increases than standard pellet fuel.

  14. Gold-titania interface toughening and thermal conductance enhancement using an organophosphonate nanolayer

    SciTech Connect (OSTI)

    Chow, Philippe K.; O'Brien, Peter; Ramanath, Ganpati; Cardona Quintero, Y.; Ramprasad, R.; Hubert Mutin, P.; Lane, Michael

    2013-05-20

    We demonstrate that a mercaptan-terminated organophosphonate nanolayer at gold-titania interfaces can give rise to two- to three-fold enhancement in the interfacial fracture toughness and thermal conductance. Electron spectroscopy reveals that interfacial delamination occurs at the metal-molecule interface near the gold-sulfur bonds, consistent with density functional theory calculations of bond energies. Qualitative correlation between interfacial fracture toughness and bond energies suggest that organophosphonate nanolayers are resilient to humidity-induced degradation. These results, and the versatility of organophosphonates as surface functionalization agents for technologically relevant materials, unlock uncharted avenues for molecular engineering of interfaces in materials and devices for a variety of applications.

  15. Subsurface Temperature, Moisture, Thermal Conductivity and Heat Flux, Barrow, Area A, B, C, D

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    Cable, William; Romanovsky, Vladimir

    2014-03-31

    Subsurface temperature data are being collected along a transect from the center of the polygon through the trough (and to the center of the adjacent polygon for Area D). Each transect has five 1.5m vertical array thermistor probes with 16 thermistors each. This dataset also includes soil pits that have been instrumented for temperature, water content, thermal conductivity, and heat flux at the permafrost table. Area C has a shallow borehole of 2.5 meters depth is instrumented in the center of the polygon.

  16. Subsurface Temperature, Moisture, Thermal Conductivity and Heat Flux, Barrow, Area A, B, C, D

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    Cable, William; Romanovsky, Vladimir

    Subsurface temperature data are being collected along a transect from the center of the polygon through the trough (and to the center of the adjacent polygon for Area D). Each transect has five 1.5m vertical array thermistor probes with 16 thermistors each. This dataset also includes soil pits that have been instrumented for temperature, water content, thermal conductivity, and heat flux at the permafrost table. Area C has a shallow borehole of 2.5 meters depth is instrumented in the center of the polygon.

  17. Prediction of Thermal Conductivity for Irradiated SiC/SiC Composites by Informing Continuum Models with Molecular Dynamics Data

    SciTech Connect (OSTI)

    Nguyen, Ba Nghiep; Gao, Fei; Henager, Charles H.; Kurtz, Richard J.

    2014-05-01

    This article proposes a new method to estimate the thermal conductivity of SiC/SiC composites subjected to neutron irradiation. The modeling method bridges different scales from the atomic scale to the scale of a 2D SiC/SiC composite. First, it studies the irradiation-induced point defects in perfect crystalline SiC using molecular dynamics (MD) simulations to compute the defect thermal resistance as a function of vacancy concentration and irradiation dose. The concept of defect thermal resistance is explored explicitly in the MD data using vacancy concentrations and thermal conductivity decrements due to phonon scattering. Point defect-induced swelling for chemical vapor deposited (CVD) SiC as a function of irradiation dose is approximated by scaling the corresponding MD results for perfect crystal ?-SiC to experimental data for CVD-SiC at various temperatures. The computed thermal defect resistance, thermal conductivity as a function of grain size, and definition of defect thermal resistance are used to compute the thermal conductivities of CVD-SiC, isothermal chemical vapor infiltrated (ICVI) SiC and nearly-stoichiometric SiC fibers. The computed fiber and ICVI-SiC matrix thermal conductivities are then used as input for an Eshelby-Mori-Tanaka approach to compute the thermal conductivities of 2D SiC/SiC composites subjected to neutron irradiation within the same irradiation doses. Predicted thermal conductivities for an irradiated Tyranno-SA/ICVI-SiC composite are found to be comparable to available experimental data for a similar composite ICVI-processed with these fibers.

  18. Direct Measurement of EGR Cooler Deposit Thermal Properties for Improved Understanding of Cooler Fouling

    SciTech Connect (OSTI)

    Wang, Hsin; Sluder, Scott; Storey, John Morse

    2009-01-01

    Exhaust gas recirculation (EGR) cooler fouling has become a significant issue for compliance with NOX emissions standards. This paper reports results of a study of fundamental aspects of EGR cooler fouling. An apparatus and procedure were developed to allow surrogate EGR cooler tubes to be exposed to diesel engine exhaust under controlled conditions. The resulting fouled tubes were removed and analyzed. Volatile and non-volatile deposit mass was measured for each tube. Thermal diffusivity of the deposited soot cake was measured by milling a window into the tube and using the Xenon flash lamp method. The heat capacity of the deposit was measured at temperatures up to 430 C and was slightly higher than graphite, presumably due to the presence of hydrocarbons. These measurements were combined to allow calculation of the deposit thermal conductivity, which was determined to be 0.041 W/mK, only ~1.5 times that of air and much lower than the 304 stainless steel tube (14.7 W/mK). The main determinant of the deposit thermal conductivity is density, which was measured to be just 2% that of the density of the primary soot particles (or 98% porous). The deposit layer thermal resistance was calculated and compared with estimates of the thermal resistance calculated from gas temperature data during the experiment. The deposit properties were also used to further analyze the temperature data collected during the experiment.

  19. Optimization of the random multilayer structure to break the random-alloy limit of thermal conductivity

    SciTech Connect (OSTI)

    Wang, Yan; Gu, Chongjie; Ruan, Xiulin

    2015-02-16

    A low lattice thermal conductivity (κ) is desired for thermoelectrics, and a highly anisotropic κ is essential for applications such as magnetic layers for heat-assisted magnetic recording, where a high cross-plane (perpendicular to layer) κ is needed to ensure fast writing while a low in-plane κ is required to avoid interaction between adjacent bits of data. In this work, we conduct molecular dynamics simulations to investigate the κ of superlattice (SL), random multilayer (RML) and alloy, and reveal that RML can have 1–2 orders of magnitude higher anisotropy in κ than SL and alloy. We systematically explore how the κ of SL, RML, and alloy changes relative to each other for different bond strength, interface roughness, atomic mass, and structure size, which provides guidance for choosing materials and structural parameters to build RMLs with optimal performance for specific applications.

  20. Manipulator having thermally conductive rotary joint for transferring heat from a test specimen

    DOE Patents [OSTI]

    Haney, Steven J.; Stulen, Richard H.; Toly, Norman F.

    1985-01-01

    A manipulator for rotatably moving a test specimen in an ultra-high vacuum chamber includes a translational unit movable in three mutually perpendicular directions. A manipulator frame is rigidly secured to the translational unit for rotatably supporting a rotary shaft. A first copper disc is rigidly secured to an end of the rotary shaft for rotary movement within the vacuum chamber. A second copper disc is supported upon the first disc. The second disc receives a cryogenic cold head and does not rotate with the first disc. A sapphire plate is interposed between the first and second discs to prevent galling of the copper material while maintaining high thermal conductivity between the first and second discs. A spring is disposed on the shaft to urge the second disc toward the first disc and compressingly engage the interposed sapphire plate. A specimen mount is secured to the first disc for rotation within the vacuum chamber. The specimen maintains high thermal conductivity with the second disc receiving the cryogenic transfer line.

  1. Manipulator having thermally conductive rotary joint for transferring heat from a test specimen

    DOE Patents [OSTI]

    Haney, S.J.; Stulen, R.H.; Toly, N.F.

    1983-05-03

    A manipulator for rotatably moving a test specimen in an ultra-high vacuum chamber includes a translational unit movable in three mutually perpendicular directions. A manipulator frame is rigidly secured to the translational unit for rotatably supporting a rotary shaft. A first copper disc is rigidly secured to an end of the rotary shaft for rotary movement within the vacuum chamber. A second copper disc is supported upon the first disc. The second disc receives a cryogenic cold head and does not rotate with the first disc. The second disc receives a cryogenic cold head and does not rotate with the first disc. A sapphire plate is interposed between the first and second discs to prevent galling of the copper material while maintaining high thermal conductivity between the first and second discs. A spring is disposed on the shaft to urge the second disc toward the first disc and compressingly engage the interposed sapphire plate. A specimen mount is secured to the first disc for rotation within the vacuum chamber. The specimen maintains high thermal conductivity with the second disc receiving the cryogenic transfer line.

  2. Nonlinear vs. bolometric radiation response and phonon thermal conductance in graphene-superconductor junctions

    SciTech Connect (OSTI)

    Vora, Heli; Nielsen, Bent; Du, Xu [Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York (United States)

    2014-02-21

    Graphene is a promising candidate for building fast and ultra-sensitive bolometric detectors due to its weak electron-phonon coupling and low heat capacity. In order to realize a practical graphene-based bolometer, several important issues, including the nature of radiation response, coupling efficiency to the radiation and the thermal conductance need to be carefully studied. Addressing these issues, we present graphene-superconductor junctions as a viable option to achieve efficient and sensitive bolometers, with the superconductor contacts serving as hot electron barriers. For a graphene-superconductor device with highly transparent interfaces, the resistance readout in the presence of radio frequency radiation is dominated by non-linear response. On the other hand, a graphene-superconductor tunnel device shows dominantly bolometric response to radiation. For graphene devices fabricated on SiO{sub 2} substrates, we confirm recent theoretical predictions of T{sup 2} temperature dependence of phonon thermal conductance in the presence of disorder in the graphene channel at low temperatures.

  3. Tensile strains give rise to strong size effects for thermal conductivities of silicene, germanene and stanene

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Kuang, Youdi D.; Lindsay, Lucas R.; Shi, Sanqiang Q.; Zhen, Guangping P.

    2016-01-11

    Based on first principles calculations and self-consistent solution of linearized Boltzmann-Peierls equation for phonon transport approach within a three-phonon scattering framework, we characterize lattice thermal conductivities k of freestanding silicene, germanene and stanene under different isotropic tensile strains and temperatures. We find a strong size dependence of k for silicene with tensile strain, i.e., divergent k with increasing system size, in contrast, the intrinsic room temperature k for unstrained silicene converges with system size to 19.34 W/m–1 K–1 by 178 nm. The room temperature k of strained silicene becomes as large as that of bulk silicon by 84 m, indicatingmore » the possibility of using strain in silicene to manipulate k for thermal management. The relative contribution to the intrinsic k from out-of-plane acoustic modes is largest for unstrained silicene, –39% at room temperature. The single mode relaxation time approximation, which works reasonably well for bulk silicon, fails to appropriately describe phonon thermal transport in silicene, germanene and stanene within the temperature range considered. For large samples of silicene, k increases with tensile strain, peaks at –7% strain and then decreases with further strain. In germanene and stanene increasing strain hardens and stabilizes long wavelength out-of-plane acoustic phonons, and leads to similar k behaviors to those of silicene. As a result, these findings further our understanding of phonon dynamics in group-IV buckled monolayers and may guide transfer and fabrication techniques of these freestanding samples and engineering k by size and strain for applications of thermal management and thermoelectricity.« less

  4. Method for the thermal characterization, visualization, and integrity evaluation of conducting material samples or complex structures

    DOE Patents [OSTI]

    Ortiz, Marcos G.

    1992-01-01

    A method for modeling a conducting material sample or structure (herein called a system) as at least two regions which comprise an electrical network of resistances, for measuring electric resistance between at least two selected pairs of external leads attached to the surface of the system, wherein at least one external lead is attached to the surface of each of the regions, and, using basic circuit theory, for translating measured resistances into temperatures or thermophysical properties in corresponding regions of the system.

  5. SSC 50 mm dipole magnet cryostat thermal measurement results

    SciTech Connect (OSTI)

    Boroski, W.N.; Nicol, T.H.; Ruschman, M.K.; Schoo, C.J.

    1993-05-01

    A prototype Superconducting Super Collider (SSC) 50 mm dipole magnet cryostat, DCA323, was instrumented at Fermilab and delivered to the SSC Laboratory for installation into the accelerator systems string test facility. In series with other magnets, the instrumented cryostat will be used to quantify and verify cryostat thermal performance with respect to design requirements. Prior to leaving Fermilab, DCA323 was subjected to magnetic testing at the Magnet Test Facility (MTF). This presented an opportunity to obtain preliminary thermal performance data under simulated operating conditions. It should be noted that measurements of overall cryostat thermal performance were not possible during the MTF measurements as the magnet test stands are designed for magnetic rather than thermal testing. They are not designed to limit heat inleak to the ends of the cryostat, which has been shown to have a significant effect on overall measured thermal performance. Nonetheless, these measurements do offer insight into the performance of several of the cryostat components and sub-systems.

  6. Thermally conductive cementitious grouts for geothermal heat pumps. Progress report FY 1998

    SciTech Connect (OSTI)

    Allan, M.L.; Philippacopoulos, A.J.

    1998-11-01

    Research commenced in FY 97 to determine the suitability of superplasticized cement-sand grouts for backfilling vertical boreholes used with geothermal heat pump (GHP) systems. The overall objectives were to develop, evaluate and demonstrate cementitious grouts that could reduce the required bore length and improve the performance of GHPs. This report summarizes the accomplishments in FY 98. The developed thermally conductive grout consists of cement, water, a particular grade of silica sand, superplasticizer and a small amount of bentonite. While the primary function of the grout is to facilitate heat transfer between the U-loop and surrounding formation, it is also essential that the grout act as an effective borehole sealant. Two types of permeability (hydraulic conductivity) tests was conducted to evaluate the sealing performance of the cement-sand grout. Additional properties of the proposed grout that were investigated include bleeding, shrinkage, bond strength, freeze-thaw durability, compressive, flexural and tensile strengths, elastic modulus, Poisson`s ratio and ultrasonic pulse velocity.

  7. Thermal conductivity of Bi{sub 2}Te{sub 3} tilted nanowires, a molecular dynamics study

    SciTech Connect (OSTI)

    Li, Shen Lacroix, David; Termentzidis, Konstantinos; Chaput, Laurent; Stein, Nicolas; Frantz, Cedric

    2015-06-08

    Evidence for an excellent compromise between structural stability and low thermal conductivity has been achieved with tilted Bi{sub 2}Te{sub 3} nanowires. The latter ones were recently fabricated and there is a need in modeling and characterization. The structural stability and the thermal conductivity of Bi{sub 2}Te{sub 3} nanowires along the tilted [015]* direction and along the [010] direction have been explored. For the two configurations of nanowires, the effect of the length and the cross section on the thermal conductivity is discussed. The thermal conductivity of infinite size tilted nanowire is 0.34?W/m K, significantly reduced compared to nanowire along the [010] direction (0.59?W/m K). This reveals that in Bi{sub 2}Te{sub 3} nanowires the structural anisotropy can be as important as size effects to reduce the thermal conductivity. The main reason is the reduction of the phonon mean free path which is found to be 1.7?nm in the tilted nanowires, compared to 5.3?nm for the nanowires along the [010] direction. The fact that tilted Bi{sub 2}Te{sub 3} nanowire is mechanically stable and it has extremely low thermal conductivity suggests these nanowires as a promising material for future thermoelectric generation application.

  8. Lattice Anharmonicity and Thermal Conductivity from Compressive Sensing of First-Principles Calculations

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Zhou, Fei; Nielson, Weston; Xia, Yi; Ozolins, Vidvuds

    2014-10-27

    First-principles prediction of lattice thermal conductivity KL of strongly anharmonic crystals is a long-standing challenge in solid state physics. Using recent advances in information science, we propose a systematic and rigorous approach to this problem, compressive sensing lattice dynamics (CSLD). Compressive sensing is used to select the physically important terms in the lattice dynamics model and determine their values in one shot. Non-intuitively, high accuracy is achieved when the model is trained on first-principles forces in quasi-random atomic configurations. The method is demonstrated for Si, NaCl, and Cu12Sb4S13, an earth-abundant thermoelectric with strong phononphonon interactions that limit the room-temperature KLmore » to values near the amorphous limit.« less

  9. Lattice Anharmonicity and Thermal Conductivity from Compressive Sensing of First-Principles Calculations

    SciTech Connect (OSTI)

    Zhou, Fei; Nielson, Weston; Xia, Yi; Ozoliņš, Vidvuds

    2014-10-01

    First-principles prediction of lattice thermal conductivity κL of strongly anharmonic crystals is a long-standing challenge in solid-state physics. Making use of recent advances in information science, we propose a systematic and rigorous approach to this problem, compressive sensing lattice dynamics. Compressive sensing is used to select the physically important terms in the lattice dynamics model and determine their values in one shot. Nonintuitively, high accuracy is achieved when the model is trained on first-principles forces in quasirandom atomic configurations. The method is demonstrated for Si, NaCl, and Cu12Sb4S13, an earth-abundant thermoelectric with strong phonon-phonon interactions that limit the room-temperature κL to values near the amorphous limit.

  10. Method of making improved gas storage carbon with enhanced thermal conductivity

    DOE Patents [OSTI]

    Burchell, Timothy D [Oak Ridge, TN; Rogers, Michael R [Knoxville, TN

    2002-11-05

    A method of making an adsorbent carbon fiber based monolith having improved methane gas storage capabilities is disclosed. Additionally, the monolithic nature of the storage carbon allows it to exhibit greater thermal conductivity than conventional granular activated carbon or powdered activated carbon storage beds. The storage of methane gas is achieved through the process of physical adsorption in the micropores that are developed in the structure of the adsorbent monolith. The disclosed monolith is capable of storing greater than 150 V/V of methane [i.e., >150 STP (101.325 KPa, 298K) volumes of methane per unit volume of storage vessel internal volume] at a pressure of 3.5 MPa (500 psi).

  11. Deformation mechanisms, defects, heat treatment, and thermal conductivity in large grain niobium

    SciTech Connect (OSTI)

    Bieler, Thomas R. Kang, Di Baars, Derek C.; Chandrasekaran, Saravan; Mapar, Aboozar Wright, Neil T.; Ciovati, Gianluigi Myneni, Ganapati Rao; Pourboghrat, Farhang; Murphy, James E.; Compton, Chris C.

    2015-12-04

    The physical and mechanical metallurgy underlying fabrication of large grain cavities for superconducting radio frequency accelerators is summarized, based on research of 1) grain orientations in ingots, 2) a metallurgical assessment of processing a large grain single cell cavity and a tube, 3) assessment of slip behavior of single crystal tensile samples extracted from a high purity ingot slice before and after annealing at 800 °C / 2 h, 4) development of crystal plasticity models based upon the single crystal experiments, and 5) assessment of how thermal conductivity is affected by strain, heat treatment, and exposure to hydrogen. Because of the large grains, the plastic anisotropy of deformation is exaggerated, and heterogeneous strains and localized defects are present to a much greater degree than expected in polycrystalline material, making it highly desirable to computationally anticipate potential forming problems before manufacturing cavities.

  12. Thermal conductivity in large-J two-dimensional antiferromagnets: Role of phonon scattering

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Chernyshev, A. L.; Brenig, Wolfram

    2015-08-05

    Different types of relaxation processes for magnon heat current are discussed, with a particular focus on coupling to three-dimensional phonons. There is thermal conductivity by these in-plane magnetic excitations using two distinct techniques: Boltzmann formalism within the relaxation-time approximation and memory-function approach. Also considered are the scattering of magnons by both acoustic and optical branches of phonons. We demonstrate an accord between the two methods, regarding the asymptotic behavior of the effective relaxation rates. It is strongly suggested that scattering from optical or zone-boundary phonons is important for magnon heat current relaxation in a high-temperature window of ΘD≲T<< J.

  13. Contactless measurement of alternating current conductance in quantum Hall structures

    SciTech Connect (OSTI)

    Drichko, I. L.; Diakonov, A. M.; Malysh, V. A.; Smirnov, I. Yu.; Ilyinskaya, N. D.; Usikova, A. A.; Galperin, Y. M.; Kummer, M.; Känel, H. von

    2014-10-21

    We report a procedure to determine the frequency-dependent conductance of quantum Hall structures in a broad frequency domain. The procedure is based on the combination of two known probeless methods—acoustic spectroscopy and microwave spectroscopy. By using the acoustic spectroscopy, we study the low-frequency attenuation and phase shift of a surface acoustic wave in a piezoelectric crystal in the vicinity of the electron (hole) layer. The electronic contribution is resolved using its dependence on a transverse magnetic field. At high frequencies, we study the attenuation of an electromagnetic wave in a coplanar waveguide. To quantitatively calibrate these data, we use the fact that in the quantum-Hall-effect regime the conductance at the maxima of its magnetic field dependence is determined by extended states. Therefore, it should be frequency independent in a broad frequency domain. The procedure is verified by studies of a well-characterized p-SiGe/Ge/SiGe heterostructure.

  14. Microstructure and thermal conductivity of surfactant-free NiO nanostructures

    SciTech Connect (OSTI)

    Sahoo, Pranati; Misra, Dinesh K.; Salvador, Jim; Makongo, Julien P.A.; Chaubey, Girija S.; Takas, Nathan J.; Wiley, John B.; Poudeu, Pierre F.P.

    2012-06-15

    High purity, nanometer sized surfactant-free nickel oxide (NiO) particles were produced in gram scale using a solution combustion method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), gas pycnometry and gas adsorption analysis (BET). The average particle size of the as-synthesized NiO increases significantly with the preheating temperature of the furnace, while the specific surface area decreases. A BET specific surface area of {approx}100 m{sup 2}/g was obtained for NiO nanoparticles with size as small as 3 nm synthesized at 300 Degree-Sign C. The thermal conductivity ({kappa}) of pressed pellets of the synthesized NiO nanoparticles obtained using spark plasma sintering (SPS) and uniaxial hot pressing is drastically decreased ({approx}60%) compared to that of NiO single crystal. This strong reduction in {kappa} with particle size suggests the suitability of the synthesized surfactant-free NiO nanoparticles for use as nanoinclusions when designing high performance materials for waste heat recovery. - Graphical abstract: Highly efficient phonon scattering by surfactant-free NiO nanostructures obtained by solution combustion of a mixture of nickel (II) nitrate hexahydrate (oxidizer) and urea (fuel) at various temperatures. Highlights: Black-Right-Pointing-Pointer Fast synthesis of surfactant-free NiO nanoparticles with controllable size. Black-Right-Pointing-Pointer High specific surface area for NiO nanoparticles with size range from 3 to 7 nm. Black-Right-Pointing-Pointer Strong reduction of the thermal conductivity with decreasing particle size. Black-Right-Pointing-Pointer NiO as nanoinclusions in high performance materials for energy conversion.

  15. Method for the thermal characterization, visualization, and integrity evaluation of conducting material samples or complex structures

    DOE Patents [OSTI]

    Ortiz, M.G.

    1992-11-24

    Disclosed is a method for modeling a conducting material sample or structure (herein called a system) as at least two regions which comprise an electrical network of resistances, for measuring electric resistance between at least two selected pairs of external leads attached to the surface of the system, wherein at least one external lead is attached to the surface of each of the regions, and, using basic circuit theory, for translating measured resistances into temperatures or thermophysical properties in corresponding regions of the system. 16 figs.

  16. Electrical network method for the thermal or structural characterization of a conducting material sample or structure

    DOE Patents [OSTI]

    Ortiz, M.G.

    1993-06-08

    A method for modeling a conducting material sample or structure system, as an electrical network of resistances in which each resistance of the network is representative of a specific physical region of the system. The method encompasses measuring a resistance between two external leads and using this measurement in a series of equations describing the network to solve for the network resistances for a specified region and temperature. A calibration system is then developed using the calculated resistances at specified temperatures. This allows for the translation of the calculated resistances to a region temperature. The method can also be used to detect and quantify structural defects in the system.

  17. Electrical network method for the thermal or structural characterization of a conducting material sample or structure

    DOE Patents [OSTI]

    Ortiz, Marco G.

    1993-01-01

    A method for modeling a conducting material sample or structure system, as an electrical network of resistances in which each resistance of the network is representative of a specific physical region of the system. The method encompasses measuring a resistance between two external leads and using this measurement in a series of equations describing the network to solve for the network resistances for a specified region and temperature. A calibration system is then developed using the calculated resistances at specified temperatures. This allows for the translation of the calculated resistances to a region temperature. The method can also be used to detect and quantify structural defects in the system.

  18. Electrostatic analyzer measurements of ionospheric thermal ion populations

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Fernandes, P. A.; Lynch, K. A.

    2016-07-09

    Here, we define the observational parameter regime necessary for observing low-altitude ionospheric origins of high-latitude ion up ow/out ow. We present measurement challenges and identify a new analysis technique which mitigates these impediments. To probe the initiation of auroral ion up ow, it is necessary to examine the thermal ion population at 200{350 km, where typical thermal energies are tenths of eV. Interpretation of the thermal ion distribution function measurement requires removal of payload sheath and ram effects. We use a 3-D Maxwellian model to quantify how observed ionospheric parameters such as density, temperature, and flows affect in situ measurementsmore » of the thermal ion distribution function. We define the viable acceptance window of a typical top-hat electrostatic analyzer in this regime and show that the instrument's energy resolution prohibits it from directly observing the shape of the particle spectra. To extract detailed information about measured particle population, we define two intermediate parameters from the measured distribution function, then use a Maxwellian model to replicate possible measured parameters for comparison to the data. Liouville's theorem and the thin-sheath approximation allow us to couple the measured and modeled intermediate parameters such that measurements inside the sheath provide information about plasma out- side the sheath. We apply this technique to sounding rocket data to show that careful windowing of the data and Maxwellian models allows for extraction of the best choice of geophysical parameters. More widespread use of this analysis technique will help our community expand its observational database of the seed regions of ionospheric outflows.« less

  19. Numerical investigation of CO{sub 2} emission and thermal stability of a convective and radiative stockpile of reactive material in a cylindrical pipe of variable thermal conductivity

    SciTech Connect (OSTI)

    Lebelo, Ramoshweu Solomon

    2014-10-24

    In this paper the CO{sub 2} emission and thermal stability in a long cylindrical pipe of combustible reactive material with variable thermal conductivity are investigated. It is assumed that the cylindrical pipe loses heat by both convection and radiation at the surface. The nonlinear differential equations governing the problem are tackled numerically using Runge-Kutta-Fehlberg method coupled with shooting technique method. The effects of various thermophysical parameters on the temperature and carbon dioxide fields, together with critical conditions for thermal ignition are illustrated and discussed quantitatively.

  20. Graphitic carbon nanospheres: A Raman spectroscopic investigation of thermal conductivity and morphological evolution by pulsed laser irradiation

    SciTech Connect (OSTI)

    Agarwal, Radhe; Sahoo, Satyaprakash E-mail: rkatiyar@hpcf.upr.edu; Chitturi, Venkateswara Rao; Katiyar, Ram S. E-mail: rkatiyar@hpcf.upr.edu

    2015-12-07

    Graphitic carbon nanospheres (GCNSs) were prepared by a unique acidic treatment of multi-walled nanotubes. Spherical morphology with a narrow size distribution was confirmed by transmission electron microscopy studies. The room temperature Raman spectra showed a clear signature of D- and G-peaks at around 1350 and 1591 cm{sup −1}, respectively. Temperature dependent Raman scattering measurements were performed to understand the phonon dynamics and first order temperature coefficients related to the D- and G-peaks. The temperature dependent Raman spectra in a range of 83–473 K were analysed, where the D-peak was observed to show a red-shift with increasing temperature. The relative intensity ratio of D- to G-peaks also showed a significant rise with increasing temperature. Such a temperature dependent behaviour can be attributed to lengthening of the C-C bond due to thermal expansion in material. The estimated value of the thermal conductivity of GCNSs ∼0.97 W m{sup −1} K{sup −1} was calculated using Raman spectroscopy. In addition, the effect of pulsed laser treatment on the GCNSs was demonstrated by analyzing the Raman spectra of post irradiated samples.

  1. MEASUREMENT OF WIND SPEED FROM COOLING LAKE THERMAL IMAGERY

    SciTech Connect (OSTI)

    Garrett, A; Robert Kurzeja, R; Eliel Villa-Aleman, E; Cary Tuckfield, C; Malcolm Pendergast, M

    2009-01-20

    The Savannah River National Laboratory (SRNL) collected thermal imagery and ground truth data at two commercial power plant cooling lakes to investigate the applicability of laboratory empirical correlations between surface heat flux and wind speed, and statistics derived from thermal imagery. SRNL demonstrated in a previous paper [1] that a linear relationship exists between the standard deviation of image temperature and surface heat flux. In this paper, SRNL will show that the skewness of the temperature distribution derived from cooling lake thermal images correlates with instantaneous wind speed measured at the same location. SRNL collected thermal imagery, surface meteorology and water temperatures from helicopters and boats at the Comanche Peak and H. B. Robinson nuclear power plant cooling lakes. SRNL found that decreasing skewness correlated with increasing wind speed, as was the case for the laboratory experiments. Simple linear and orthogonal regression models both explained about 50% of the variance in the skewness - wind speed plots. A nonlinear (logistic) regression model produced a better fit to the data, apparently because the thermal convection and resulting skewness are related to wind speed in a highly nonlinear way in nearly calm and in windy conditions.

  2. DIRECT MEASUREMENT OF HEAT FLUX FROM COOLING LAKE THERMAL IMAGERY

    SciTech Connect (OSTI)

    Garrett, A; Eliel Villa-Aleman, E; Robert Kurzeja, R; Malcolm Pendergast, M; Timothy Brown, T; Saleem Salaymeh, S

    2007-12-19

    Laboratory experiments show a linear relationship between the total heat flux from a water surface to air and the standard deviation of the surface temperature field, {sigma}, derived from thermal images of the water surface over a range of heat fluxes from 400 to 1800 Wm{sup -2}. Thermal imagery and surface data were collected at two power plant cooling lakes to determine if the laboratory relationship between heat flux and {sigma} exists in large heated bodies of water. The heat fluxes computed from the cooling lake data range from 200 to 1400 Wm{sup -2}. The linear relationship between {sigma} and Q is evident in the cooling lake data, but it is necessary to apply band pass filtering to the thermal imagery to remove camera artifacts and non-convective thermal gradients. The correlation between {sigma} and Q is improved if a correction to the measured {sigma} is made that accounts for wind speed effects on the thermal convection. Based on more than a thousand cooling lake images, the correlation coefficients between {sigma} and Q ranged from about 0.8 to 0.9.

  3. The effect of fuel thermal conductivity on the behavior of LWR cores during loss-of-coolant accidents

    SciTech Connect (OSTI)

    Terrani, Kurt A.; Wang, Dean; Ott, Larry J.; Montgomery, Robert O.

    2014-05-01

    The effect of variation in thermal conductivity of light water reactor fuel elements on core response during loss-of-coolant accident scenarios is examined. Initially, a simplified numerical analysis is utilized to determine the time scales associated with dissipation of stored energy from the fuel into the coolant once the fission reaction is stopped. The analysis is then followed by full reactor system thermal-hydraulics analysis of a typical boiling and pressurized water reactor subjected to a large break loss-of-coolant accident scenario using the TRACE code. Accordingly, sensitivity analyses to examine the effect of an increase in fuel thermal conductivity, up to 500%, on fuel temperature evolution during these transients are performed. Given the major differences in thermal-hydraulics design aspects of boiling and pressurized water reactors, different fuel and temperature responses during the simulated loss-of-coolant transients are observed.

  4. Development of an Innovative High-Thermal Conductivity UO2 Ceramic Composites Fuel Pellets with Carbon Nano-Tubes Using Spark Plasma Sintering

    SciTech Connect (OSTI)

    Subhash, Ghatu; Wu, Kuang-Hsi; Tulenko, James

    2014-03-10

    thermally conductive UO2-CNT composite is obtained with a minimal volume fraction of CNTs. The mixtures are sintered in the SPS facility at a range of temperatures, pressures, and time durations so as to identify the optimal processing conditions to obtain the desired microstructure of sintered UO2-CNT pellets. The second objective of the proposed work is to identify the optimal volume fraction of CNTs in the microstructure of the composites that provides the desired high thermal conductivity yet retaining the mechanical strength required for efficient function as a reactor fuel. We will systematically study the resulting microstructure (grain size, porosity, distribution of CNTs, etc.) obtained at various SPS processing conditions using optical microscopy, scanning electron microscopy (SEM), and transmission electron microscope (TEM). We will conduct indentation hardness measurements and uniaxial strength measurements as a function of volume fraction of CNTs to determine the mechanical strength and compare them to the properties of UO2. The fracture surfaces will be studied to determine the fracture characteristics that may relate to the observed cracking during service. Finally, we will perform thermal conductivity measurements on all the composites up to 1000° C. This study will relate the microstructure, mechanical properties, and thermal properties at various volume fractions of CNTs. The overall intent is to identify optimal processing conditions that will provide a well-consolidated compact with optimal microstructure and thermo-mechanical properties. The deliverables include: (1) fully characterized UO2-CNT composite with optimal CNT volume fraction and high thermal conductivity and (2) processing conditions for production of UO2-CNT composite pellets using SPS method.

  5. Ensemble Sampling vs. Time Sampling in Molecular Dynamics Simulations of Thermal Conductivity

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Gordiz, Kiarash; Singh, David J.; Henry, Asegun

    2015-01-29

    In this report we compare time sampling and ensemble averaging as two different methods available for phase space sampling. For the comparison, we calculate thermal conductivities of solid argon and silicon structures, using equilibrium molecular dynamics. We introduce two different schemes for the ensemble averaging approach, and show that both can reduce the total simulation time as compared to time averaging. It is also found that velocity rescaling is an efficient mechanism for phase space exploration. Although our methodology is tested using classical molecular dynamics, the ensemble generation approaches may find their greatest utility in computationally expensive simulations such asmore » first principles molecular dynamics. For such simulations, where each time step is costly, time sampling can require long simulation times because each time step must be evaluated sequentially and therefore phase space averaging is achieved through sequential operations. On the other hand, with ensemble averaging, phase space sampling can be achieved through parallel operations, since each ensemble is independent. For this reason, particularly when using massively parallel architectures, ensemble sampling can result in much shorter simulation times and exhibits similar overall computational effort.« less

  6. ROTATING SOLAR JETS IN SIMULATIONS OF FLUX EMERGENCE WITH THERMAL CONDUCTION

    SciTech Connect (OSTI)

    Fang, Fang; Fan, Yuhong; McIntosh, Scott W.

    2014-07-01

    We study the formation of coronal jets through numerical simulation of the emergence of a twisted magnetic flux rope into a pre-existing open magnetic field. Reconnection inside the emerging flux rope in addition to that between the emerging and pre-existing fields give rise to the violent eruption studied. The simulated event closely resembles the coronal jets ubiquitously observed by the X-Ray Telescope on board Hinode and demonstrates that heated plasma is driven into the extended atmosphere above. Thermal conduction implemented in the model allows us to qualitatively compare simulated and observed emission from such events. We find that untwisting field lines after the reconnection drive spinning outflows of plasma in the jet column. The Poynting flux in the simulated jet is dominated by the untwisting motions of the magnetic fields loaded with high-density plasma. The simulated jet is comprised of ''spires'' of untwisting field that are loaded with a mixture of cold and hot plasma and exhibit rotational motion of order 20 km s{sup –1} and match contemporary observations.

  7. Device and Software to Measure Thermal Impedance of Electrochemical Systems

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    - Energy Innovation Portal Vehicles and Fuels Vehicles and Fuels Energy Storage Energy Storage Energy Analysis Energy Analysis Advanced Materials Advanced Materials Find More Like This Return to Search Device and Software to Measure Thermal Impedance of Electrochemical Systems National Renewable Energy Laboratory Contact NREL About This Technology Technology Marketing Summary Different components within an electrochemical system (e.g., a battery) can generate heat due to inefficiencies in

  8. Evaluation of thermal gradients in longitudinal spin Seebeck effect measurements

    SciTech Connect (OSTI)

    Sola, A. Kuepferling, M.; Basso, V.; Pasquale, M.; Kikkawa, T.; Uchida, K.; Saitoh, E.

    2015-05-07

    In the framework of the longitudinal spin Seebeck effect (LSSE), we developed an experimental setup for the characterization of LSSE devices. This class of device consists in a layered structure formed by a substrate, a ferrimagnetic insulator (YIG) where the spin current is thermally generated, and a paramagnetic metal (Pt) for the detection of the spin current via the inverse spin-Hall effect. In this kind of experiments, the evaluation of a thermal gradient through the thin YIG layer is a crucial point. In this work, we perform an indirect determination of the thermal gradient through the measurement of the heat flux. We developed an experimental setup using Peltier cells that allow us to measure the heat flux through a given sample. In order to test the technique, a standard LSSE device produced at Tohoku University was measured. We find a spin Seebeck S{sub SSE} coefficient of 2.8×10{sup −7} V K{sup −1}.

  9. In-situ nanostructure generation and evolution within a bulk thermoelectric material to reduce lattice thermal conductivity

    SciTech Connect (OSTI)

    Girard, Steven; He, Jiaqing; Li, Chang-Peng; Moses, Steven; Wang, Guoyu Y.; Uher, Ctirad; Dravid, Vinayak; Kanatzidis, Mercouri G.

    2010-07-26

    We show experimentally the direct reduction in lattice thermal conductivity as a result of in situ nanostructure generation within a thermoelectric material. Solid solution alloys of the high-performance thermoelectric PbTe-PbS 8% can be synthesized through rapid cooling and subsequent high-temperature activation that induces a spontaneous nucleation and growth of PbS nanocrystals. The emergence of coherent PbS nanostructures reduces the lattice thermal conductivity from ~1 to ~0.4 W/mK between 400 and 500 K.

  10. Modeling the Transverse Thermal Conductivity of 2-D SiCf/SiC Composites Made with Woven Fabric

    SciTech Connect (OSTI)

    Youngblood, Gerald E.; Senor, David J.; Jones, Russell H.

    2004-06-30

    The hierarchical two-layer (H2L) model was developed to describe the effective transverse thermal conductivity, Keff, of a 2D-SiCf/SiC composite made from stacked and infiltrated woven fabric layers in terms of constituent properties and microstructural and architectural variables. The H2L model includes the expected effects of fiber-matrix interfacial conductance as well as the effects of high fiber packing fractions within individual tows and the non-uniform nature of 2D-fabric layers that usually include a significant amount of interlayer porosity. Previously, H2L model predictions were compared to measured values of Keff for two versions of DuPont 2D-Hi NicalonÔ/PyC/ICVI-SiC composite, one with a “thin” (0.110 μm) and the other with a “thick” (1.040 μm) pyrocarbon (PyC) fiber coating, and for a 2D-TyrannoÔ SA/”thin” PyC/FCVI-SIC composite made by ORNL. In this study, H2L model predictions are compared to measured Keff-values for a 2D-SiCf/SiC composite made by GE Power Systems (formerly DuPont Lanxide) using the ICVI-process with Hi-NicalonÔ type S fabric. The values of Keff determined for the composite made with the Hi-NicalonÔ type S fabric were significantly greater than Keff-values determined for the composites made with either the Hi-NicalonÔor the TyrannoÔ SA fabrics. Differences in Keff-values were expected for using different fiber types, but major differences also were due to observed microstructural variations between the systems, and as predicted by the H2L model.

  11. Superior thermoelectric performance in PbTe-PbS pseudo-binary. Extremely low thermal conductivity and modulated carrier concentration

    SciTech Connect (OSTI)

    Wu, D.; Zhao, L. -D.; Tong, X.; Li, W.; Wu, L.; Tan, Q.; Pei, Y.; Huang, L.; Li, J. -F.; Zhu, Y.; Kanatzidis, M. G.; He, J.

    2015-05-19

    Lead chalcogenides have exhibited their irreplaceable role as thermoelectric materials at the medium temperature range, owing to highly degenerate electronic bands and intrinsically low thermal conductivities. PbTe-PbS pseudo-binary has been paid extensive attentions due to the even lower thermal conductivity which originates largely from the coexistence of both alloying and phase-separated precipitations. To investigate the competition between alloying and phase separation and its pronounced effect on the thermoelectric performance in PbTe-PbS, we systematically studied Spark Plasma Sintered (SPSed), 3 at% Na- doped (PbTe)1-x(PbS)x samples with x=10%, 15%, 20%, 25%, 30% and 35% by means of transmission electron microscopy (TEM) observations and theoretical calculations. Corresponding to the lowest lattice thermal conductivity as a result of the balance between point defect- and precipitates- scattering, the highest figure of merit ZT~2.3 was obtained at 923 K when PbS phase fraction x is at 20%. The consistently lower lattice thermal conductivities in SPSed samples compared with corresponding ingots, resulting from the powdering and follow-up consolidation processes, also contribute to the observed superior ZT. Notably, the onset of carrier concentration modulation ~600 K due to excessive Na’s diffusion and re-dissolution leads to the observed saturations of electrical transport properties, which is believed equally crucial to the outstanding thermoelectric performance of SPSed PbTe-PbS samples.

  12. Superior thermoelectric performance in PbTe-PbS pseudo-binary. Extremely low thermal conductivity and modulated carrier concentration

    SciTech Connect (OSTI)

    Wu, D.; Zhao, L. -D.; Tong, X.; Li, W.; Wu, L.; Tan, Q.; Pei, Y.; Huang, L.; Li, J. -F.; Zhu, Y.; Kanatzidis, M. G.; He, J.

    2015-05-19

    Lead chalcogenides have exhibited their irreplaceable role as thermoelectric materials at the medium temperature range, owing to highly degenerate electronic bands and intrinsically low thermal conductivities. PbTe-PbS pseudo-binary has been paid extensive attentions due to the even lower thermal conductivity which originates largely from the coexistence of both alloying and phase-separated precipitations. To investigate the competition between alloying and phase separation and its pronounced effect on the thermoelectric performance in PbTe-PbS, we systematically studied Spark Plasma Sintered (SPSed), 3 at% Na- doped (PbTe)1-x(PbS)x samples with x=10%, 15%, 20%, 25%, 30% and 35% by means of transmission electron microscopy (TEM) observations and theoretical calculations. Corresponding to the lowest lattice thermal conductivity as a result of the balance between point defect- and precipitates- scattering, the highest figure of merit ZT~2.3 was obtained at 923 K when PbS phase fraction x is at 20%. The consistently lower lattice thermal conductivities in SPSed samples compared with corresponding ingots, resulting from the powdering and follow-up consolidation processes, also contribute to the observed superior ZT. Notably, the onset of carrier concentration modulation ~600 K due to excessive Nas diffusion and re-dissolution leads to the observed saturations of electrical transport properties, which is believed equally crucial to the outstanding thermoelectric performance of SPSed PbTe-PbS samples.

  13. Superior thermoelectric performance in PbTe-PbS pseudo-binary. Extremely low thermal conductivity and modulated carrier concentration

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Wu, D.; Zhao, L. -D.; Tong, X.; Li, W.; Wu, L.; Tan, Q.; Pei, Y.; Huang, L.; Li, J. -F.; Zhu, Y.; et al

    2015-05-19

    Lead chalcogenides have exhibited their irreplaceable role as thermoelectric materials at the medium temperature range, owing to highly degenerate electronic bands and intrinsically low thermal conductivities. PbTe-PbS pseudo-binary has been paid extensive attentions due to the even lower thermal conductivity which originates largely from the coexistence of both alloying and phase-separated precipitations. To investigate the competition between alloying and phase separation and its pronounced effect on the thermoelectric performance in PbTe-PbS, we systematically studied Spark Plasma Sintered (SPSed), 3 at% Na- doped (PbTe)1-x(PbS)x samples with x=10%, 15%, 20%, 25%, 30% and 35% by means of transmission electron microscopy (TEM) observationsmore » and theoretical calculations. Corresponding to the lowest lattice thermal conductivity as a result of the balance between point defect- and precipitates- scattering, the highest figure of merit ZT~2.3 was obtained at 923 K when PbS phase fraction x is at 20%. The consistently lower lattice thermal conductivities in SPSed samples compared with corresponding ingots, resulting from the powdering and follow-up consolidation processes, also contribute to the observed superior ZT. Notably, the onset of carrier concentration modulation ~600 K due to excessive Na’s diffusion and re-dissolution leads to the observed saturations of electrical transport properties, which is believed equally crucial to the outstanding thermoelectric performance of SPSed PbTe-PbS samples.« less

  14. Abnormal thermal conductivity in tetragonal tungsten bronze Ba{sub 6−x}Sr{sub x}Nb{sub 10}O{sub 30}

    SciTech Connect (OSTI)

    Kolodiazhnyi, T. Sakurai, H.; Vasylkiv, O.; Borodianska, H.; Mozharivskyj, Y.

    2014-03-17

    Ba{sub 6−x}Sr{sub x}Nb{sub 10}O{sub 30} solid solution with 0 ≤ x ≤ 6 crystallizes in centrosymmetric tetragonal “tungsten bronze” structure (space group P4/mbm). We report on the x dependence of thermal conductivity of polycrystalline samples measured in the 2–400 K temperature interval. Substitution of Sr for Ba brings about a significant decrease in thermal conductivity at x ≥ 3 accompanied by development of a low-temperature (T ≈ 10–30 K) “plateau” region reminiscent of a glass-like compounds. We explain this behaviour based on a size-driven site occupancy and atomic displacement parameters associated with an alkaline earth atomic positions in the title compounds.

  15. Design and calibration of a test facility for MLI thermal performance measurements below 80K. [Multilayer insulation (MLI)

    SciTech Connect (OSTI)

    Boroski, W.; Kunzelman, R.; Ruschman, M.; Schoo, C.

    1992-04-01

    The design geometry of the SSC dipole cryostat includes active thermal radiation shields operating at 80K and 20K respectively. Extensive measurements conducted in a Heat Leak Test Facility (HLTF) have been used to evaluate the thermal performance of candidate multilayer insulation (MLI) systems for the 80K thermal shield, with the present system design based upon those measurement results. With the 80K MLI geometry established, efforts have focused on measuring the performance of MLI systems near 20K. A redesign of the HLTF has produced a measurement facility capable of conducting measurements with the warm boundary fixed at 80K and the cold boundary variable from 10K to 50K. Removing the 80K shield permits measurements with a warm boundary at 300K. The 80K boundary consists of a copper shield thermally anchored to a liquid nitrogen reservoir. The cold boundary consists of a copper anchor plate whose temperature is varied through boil-off gas from a 500 liter helium supply dewar. A transfer line heat exchanger supplies the boil-off gas to the anchor plate at a constant and controlled rate. The gas, which serves as cooling gas, is routed through a copper cooling tube soldered into the anchor plate. Varying the cooling gas flow rate varies the amount of refrigeration supplied to the anchor plate, thereby determining the plate temperature. A resistance heater installed on the anchor plate is regulated by a cryogenic temperature controller to provide final temperature control. Heat leak values are measured using a heatmeter which senses heat flow as a temperature gradient across a fixed thermal impedance. Since the thermal conductivity of the thermal impedance changes with temperature, the heatmeter is calibrated at key cold boundary temperatures. Thus, the system is capable of obtaining measurement data under a variety of system conditions. 7 refs.

  16. Measurement of directional thermal infrared emissivity of vegetation and soils

    SciTech Connect (OSTI)

    Norman, J.M. [Wisconsin Univ., Madison, WI (United States). Dept. of Soil Science; Balick, L.K. [EG and G Energy Measurements, Inc., Las Vegas, NV (United States)

    1995-10-01

    A new method has been developed for measuring directional thermal emissivity as a function of view angle for plant canopies and soils using two infrared thermometers each sensitive to a different wavelength band. By calibrating the two infrared thermometers to 0.1C consistency, canopy directional emissivity can be estimated with typical errors less than 0.005 in the 8--14 um wavelength band, depending on clarity of the sky and corrections for CO{sub 2} absorption by the atmosphere. A theoretical justification for the method is developed along with an error analysis. Laboratory measurements were used to develop corrections for CO{sub 2}, absorption and a field calibration method is used to obtain the necessary 0.1C consistency for relatively low cost infrared thermometers. The emissivity of alfalfa (LAI=2.5) and corn (LAI=3.2) was near 0.995 and independent of view angle. Individual corn leaves had an emissivity of 0.97. A wheat (LAI=3.0) canopy had an emissivity of 0.985 at nadir and 0.975 at 75 degree view angle. The canopy emissivity values tend to be higher than values in the literature, and are useful for converting infrared thermometer measurements to kinetic temperature and interpreting satellite thermal observations.

  17. Method and apparatus for producing a carbon based foam article having a desired thermal-conductivity gradient

    DOE Patents [OSTI]

    Klett, James W. [Knoxville, TN; Cameron, Christopher Stan [Sanford, NC

    2010-03-02

    A carbon based foam article is made by heating the surface of a carbon foam block to a temperature above its graphitizing temperature, which is the temperature sufficient to graphitize the carbon foam. In one embodiment, the surface is heated with infrared pulses until heat is transferred from the surface into the core of the foam article such that the graphitizing temperature penetrates into the core to a desired depth below the surface. The graphitizing temperature is maintained for a time sufficient to substantially entirely graphitize the portion of the foam article from the surface to the desired depth below the surface. Thus, the foam article is an integral monolithic material that has a desired conductivity gradient with a relatively high thermal conductivity in the portion of the core that was graphitized and a relatively low thermal conductivity in the remaining portion of the foam article.

  18. Apparatus and method for detecting and/or measuring flaws in conductive material

    DOE Patents [OSTI]

    Hockey, Ronald L.; Riechers, Douglas M.

    2000-01-01

    The present invention uses a magnet and sensor coil unilaterial and in relative motion to a conductive material, to measure perturbation or variation in the magnetic field in the presence of a flaw. A liftoff compensator measures a distance between the conductive material and the magnet.

  19. Glass-Like Thermal Conductivity of (010)-Textured Lanthanum-Doped Strontium Niobate Synthesized with Wet Chemical Deposition

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Foley, Brian M.; Brown-Shaklee, Harlan J.; Campion, Michael J.; Medlin, Douglas L.; Clem, Paul G.; Ihlefeld, Jon F.; Hopkins, Patrick E.

    2014-11-08

    We have measured the cross-plane thermal conductivity (κ) of (010)-textured, undoped, and lanthanum-doped strontium niobate (Sr2-xLaxNb2O7-δ) thin films via time-domain thermoreflectance. Then the thin films were deposited on (001)-oriented SrTiO3 substrates via the highly-scalable technique of chemical solution deposition. We find that both film thickness and lanthanum doping have little effect on κ, suggesting that there is a more dominant phonon scattering mechanism present in the system; namely the weak interlayer-bonding along the b-axis in the Sr2Nb2O7 parent structure. We also compare our experimental results with two variations of the minimum-limit model for κ and discuss the nature of transportmore » in material systems with weakly-bonded layers. The low cross-plane κ of these scalably-fabricated films is comparable to that of similarly layered niobate structures grown epitaxially.« less

  20. Glass-Like Thermal Conductivity of (010)-Textured Lanthanum-Doped Strontium Niobate Synthesized with Wet Chemical Deposition

    SciTech Connect (OSTI)

    Foley, Brian M.; Brown-Shaklee, Harlan J.; Campion, Michael J.; Medlin, Douglas L.; Clem, Paul G.; Ihlefeld, Jon F.; Hopkins, Patrick E.

    2014-11-08

    We have measured the cross-plane thermal conductivity (κ) of (010)-textured, undoped, and lanthanum-doped strontium niobate (Sr2-xLaxNb2O7-δ) thin films via time-domain thermoreflectance. Then the thin films were deposited on (001)-oriented SrTiO3 substrates via the highly-scalable technique of chemical solution deposition. We find that both film thickness and lanthanum doping have little effect on κ, suggesting that there is a more dominant phonon scattering mechanism present in the system; namely the weak interlayer-bonding along the b-axis in the Sr2Nb2O7 parent structure. We also compare our experimental results with two variations of the minimum-limit model for κ and discuss the nature of transport in material systems with weakly-bonded layers. The low cross-plane κ of these scalably-fabricated films is comparable to that of similarly layered niobate structures grown epitaxially.

  1. Lenard-Balescu calculations and classical molecular dynamics simulations of electrical and thermal conductivities of hydrogen plasmas

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Whitley, Heather D.; Scullard, Christian R.; Benedict, Lorin X.; Castor, John I.; Randles, Amanda; Glosli, James N.; Richards, David F.; Desjarlais, Michael P.; Graziani, Frank R.

    2015-12-04

    Here, we present a discussion of kinetic theory treatments of linear electrical and thermal transport in hydrogen plasmas, for a regime of interest to inertial confinement fusion applications. In order to assess the accuracy of one of the more involved of these approaches, classical Lenard-Balescu theory, we perform classical molecular dynamics simulations of hydrogen plasmas using 2-body quantum statistical potentials and compute both electrical and thermal conductivity from out particle trajectories using the Kubo approach. Our classical Lenard-Balescu results employing the identical statistical potentials agree well with the simulations.

  2. Thermal conductivity of La/sub 3-x/R/sub x/S/sub 4/ R = Sm, Yb, and Eu

    SciTech Connect (OSTI)

    Kokos, G.B.

    1989-02-01

    The thermal diffusivity values of La/sub 2.7/Eu/sub 0.3/S/sub 4/, La/sub 2.2/Eu/sub 0.8/S/sub 4/, La/sub 2.7/Sm/sub 0.3/S/sub 4/, La/sub 2.3/Sm/sub 0.7/S/sub 4/, La/sub 2.7/Yb/sub 0.2/S/sub 4/, and La/sub 2.2/Yb/sub 0.7/S/sub 4/ were measured by the flash diffusivity method from 400/degree/C to 1000/degree/C. These values ranged from .007 cm/sup 2//s to .018 cm/sup 2//s. The thermal conductivities of the ternary rare earth sulfides were calculated from the thermal diffusivity data and ranged from 10.7 mW/cm/degree/C to 31.6 mW/cm/degree/C. The thermal diffusivity values of three thermal conductivity standards (armco iron, NBS graphite, and NBS austenitic stainless steel) obtained using the flash diffusivity apparatus agreed with the accepted values within a deviation of +-10%. Of the ternary rare earth sulfides measured, La/sub 2.2/Eu/sub 0.8/S/sub 4/ had the highest figure of merit at 1000/degree/C of .525. All these samples had an oxysulfide present at the grain boundaries which degraded their high temperature thermoelectric performance. 56 refs., 12 figs., 7 tabs.

  3. Temperature, thermal-conductivity, and heat-flux data,Raft River...

    Open Energy Info (EERE)

    conductivity; United States; USGS Authors Urban, T.C.; Diment, W.H.; Nathenson, M.; Smith, E.P.; Ziagos, J.P.; Shaeffer and M.H. Published Open-File Report - U. S. Geological...

  4. Mathematical model of a double-coil inductive transducer for measuring electrical conductivity

    SciTech Connect (OSTI)

    Kusmierz, Jozef

    2007-08-15

    A technique for the contactless measurement of the electrical conductivity of conducting materials using a double-coil inductive transducer is presented. A mathematical model of the transducer has been created and it consists of two cylindrical coils and a tested sample in the form of a cylinder coaxial with the coils. A processing function of the transducer is defined as the ratio of voltages between terminals of the measurement coil with and without the test sample. This processing function depends on the conductivity of the test sample, the dimensions of the sample and of both coils of the transducer (the measurement coil and the excitation coil), and the frequency of the current supplied to the excitation coil. An analytical formula for the processing function is derived; analysis of graphs of this function in different formats enables us to evaluate the influence of all the essential parameters of the transducer. This is a necessary step for both transducer optimization and carrying out of the conductivity measurement of the investigated materials. In order to verify the theoretical predictions, experimental investigations have been performed using a computerized data acquisition system. First, an experimental validation of the obtained analytical formula has been completed using an aluminum sample of known conductivity. Then, the conductivity measurements of a sample made of brass have been carried out. The obtained experimental results confirm the high accuracy of the theoretical analysis.

  5. Simulated evolution of fractures and fracture networks subject to thermal cooling: A coupled discrete element and heat conduction model

    SciTech Connect (OSTI)

    Huang, Hai; Plummer, Mitchell; Podgorney, Robert

    2013-02-01

    Advancement of EGS requires improved prediction of fracture development and growth during reservoir stimulation and long-term operation. This, in turn, requires better understanding of the dynamics of the strongly coupled thermo-hydro-mechanical (THM) processes within fractured rocks. We have developed a physically based rock deformation and fracture propagation simulator by using a quasi-static discrete element model (DEM) to model mechanical rock deformation and fracture propagation induced by thermal stress and fluid pressure changes. We also developed a network model to simulate fluid flow and heat transport in both fractures and porous rock. In this paper, we describe results of simulations in which the DEM model and network flow & heat transport model are coupled together to provide realistic simulation of the changes of apertures and permeability of fractures and fracture networks induced by thermal cooling and fluid pressure changes within fractures. Various processes, such as Stokes flow in low velocity pores, convection-dominated heat transport in fractures, heat exchange between fluid-filled fractures and solid rock, heat conduction through low-permeability matrices and associated mechanical deformations are all incorporated into the coupled model. The effects of confining stresses, developing thermal stress and injection pressure on the permeability evolution of fracture and fracture networks are systematically investigated. Results are summarized in terms of implications for the development and evolution of fracture distribution during hydrofracturing and thermal stimulation for EGS.

  6. Advancing reactive tracer methods for measuring thermal evolution...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    ....51 KB) More Documents & Publications Using Thermally-Degrading, Partitioning, and Nonreactive Tracers to Determine Temperature Distribution and FractureHeat Transfer Surface Area ...

  7. Optic phonon bandwidth and lattice thermal conductivity: The case of Li2X ( X=O , S, Se, Te)

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Mukhopadhyay, S.; Lindsay, L.; Parker, D. S.

    2016-06-07

    Here, we examine the lattice thermal conductivities ( l) of Li2X (X=O, S, Se, Te) using a first-principles Peierls-Boltzmann transport methodology. We find low l values ranging between 12 and 30 W/m-K despite light Li atoms, a large mass difference between constituent atoms and tightly bunched acoustic branches, all features that give high l in other materials including BeSe (630 W/m-1K-1), BeTe (370 W/m-1K-1) and cubic BAs (3150 W/m-1K-1). Together these results suggest a missing ingredient in the basic guidelines commonly used to understand and predict l. Unlike typical simple systems (e.g., Si, GaAs, SiC), the dominant resistance to heat-carryingmore » acoustic phonons in Li2Se and Li2Te comes from interactions of these modes with two optic phonons. These interactions require significant bandwidth and dispersion of the optic branches, both present in Li2X materials. Finally, these considerations are important for the discovery and design of new materials for thermal management applications, and give a more comprehensive understanding of thermal transport in crystalline solids.« less

  8. Fully-coupled engineering and mesoscale simulations of thermal conductivity in UO2 fuel using an implicit multiscale approach

    SciTech Connect (OSTI)

    Michael Tonks; Derek Gaston; Cody Permann; Paul Millett; Glen Hansen; Chris Newman

    2009-08-01

    Reactor fuel performance is sensitive to microstructure changes during irradiation (such as fission gas and pore formation). This study proposes an approach to capture microstructural changes in the fuel by a two-way coupling of a mesoscale phase field irradiation model to an engineering scale, finite element calculation. This work solves the multiphysics equation system at the engineering-scale in a parallel, fully-coupled, fully-implicit manner using a preconditioned Jacobian-free Newton Krylov method (JFNK). A sampling of the temperature at the Gauss points of the coarse scale is passed to a parallel sequence of mesoscale calculations within the JFNK function evaluation phase of the calculation. The mesoscale thermal conductivity is calculated in parallel, and the result is passed back to the engineering-scale calculation. As this algorithm is fully contained within the JFNK function evaluation, the mesoscale calculation is nonlinearly consistent with the engineering-scale calculation. Further, the action of the Jacobian is also consistent, so the composite algorithm provides the strong nonlinear convergence properties of Newton's method. The coupled model using INL's \\bison\\ code demonstrates quadratic nonlinear convergence and good parallel scalability. Initial results predict the formation of large pores in the hotter center of the pellet, but few pores on the outer circumference. Thus, the thermal conductivity is is reduced in the center of the pellet, leading to a higher internal temperature than that in an unirradiated pellet.

  9. The thermal conductivity of mixed fuel UxPu1-xO2: molecular dynamics simulations

    SciTech Connect (OSTI)

    Liu, Xiang-Yang; Cooper, Michael William Donald; Stanek, Christopher Richard; Andersson, Anders David Ragnar

    2015-10-16

    Mixed oxides (MOX), in the context of nuclear fuels, are a mixture of the oxides of heavy actinide elements such as uranium, plutonium and thorium. The interest in the UO2-PuO2 system arises from the fact that these oxides are used both in fast breeder reactors (FBRs) as well as in pressurized water reactors (PWRs). The thermal conductivity of UO2 fuel is an important material property that affects fuel performance since it is the key parameter determining the temperature distribution in the fuel, thus governing, e.g., dimensional changes due to thermal expansion, fission gas release rates, etc. For this reason it is important to understand the thermal conductivity of MOX fuel and how it differs from UO2. Here, molecular dynamics (MD) simulations are carried out to determine quantitatively, the effect of mixing on the thermal conductivity of UxPu1-xO2, as a function of PuO2 concentrations, for a range of temperatures, 300 – 1500 K. The results will be used to develop enhanced continuum thermal conductivity models for MARMOT and BISON by INL. These models express the thermal conductivity as a function of microstructure state-variables, thus enabling thermal conductivity models with closer connection to the physical state of the fuel.

  10. Thermal performance measurements of a 100 percent polyester MLI (multilayer insulation) system for the Superconducting Super Collider

    SciTech Connect (OSTI)

    Gonczy, J.D.; Boroski, W.N.; Niemann, R.C.

    1989-09-01

    The plastic materials used in the multilayer insulation (MLI) blankets of the superconducting magnets of the Superconducting Super Collider (SSC) are comprised entirely of polyesters. This paper reports on tests conducted in three separate experimental blanket arrangements. The tests explore the thermal performance of two candidate blanket joint configurations each employing a variation of a stepped-butted joint nested between sewn blanket seams. The results from the joint configurations are compared to measurements made describing the thermal performance of the basic blanket materials as tested in an ideal joint configuration. Twenty foil sensors were incorporated within each test blanket to measure interstitial layer and joint layer temperatures. Heat flux and thermal gradients are reported for high and degraded insulating vacuums, and during transient and steady state conditions. In complement with this paper is an associate paper bearing the same title head but with the title extension Part 1: Instrumentation and experimental preparation (300K-80K)'. 5 refs., 8 figs., 2 tabs.