National Library of Energy BETA

Sample records for hl wyman ce

  1. Michelle Wyman

    Broader source: Energy.gov [DOE]

    As the former Director of Intergovernmental Affairs in the Office of Congressional & Intergovernmental Affairs at the U.S. Department of Energy, Michelle Wyman lead the Department...

  2. 1,"William F Wyman","Petroleum","FPL Energy Wyman LLC",811.3

    U.S. Energy Information Administration (EIA) Indexed Site

    Maine" ,"Plant","Primary energy source","Operating company","Net summer capacity (MW)" 1,"William F Wyman","Petroleum","FPL Energy Wyman LLC",811.3 2,"Westbrook Energy Center Power Plant","Natural gas","Westbrook Energy Center",506 3,"Maine Independence Station","Natural gas","Casco Bay Energy Co LLC",490 4,"Bucksport Generation LLC","Natural

  3. Massachusetts Beryllium Screening Program for Former Workers of Wyman-Gordon, Norton Abrasives, and MIT/Nuclear Metals

    SciTech Connect (OSTI)

    Pepper, L. D.

    2008-05-21

    The overall objective of this project was to provide medical screening to former workers of Wyman-Gordon Company, Norton Abrasives, and MIT/Nuclear Metals (NMI) in order to prevent and minimize the health impact of diseases caused by site related workplace exposures to beryllium. The program was developed in response to a request by the U.S. Department of Energy (DOE) that had been authorized by Congress in Section 3162 of the 1993 Defense Authorization Act, urging the DOE to carry out a program for the identification and ongoing evaluation of current and former DOE employees who are subjected to significant health risks during such employment." This program, funded by the DOE, was an amendment to the medical surveillance program for former DOE workers at the Nevada Test Site (NTS). This program's scope included workers who had worked for organizations that provided beryllium products or materials to the DOE as part of their nuclear weapons program. These organizations have been identified as Beryllium Vendors.

  4. HL Green Power Co | Open Energy Information

    Open Energy Info (EERE)

    Gyeonggi-do, Korea (Republic) Product: Korea(Republic)-based JV aimed at manufacturing Lithium ion car batteries for Hybrid and Electric cars. References: HL Green Power Co1 This...

  5. Experimental programme of HL-1 tokamak

    SciTech Connect (OSTI)

    Qian, S.; and HL-1 Group

    1995-09-01

    The experimental programme of HL-1 was divided into two parts. In the first period, the expansion of the HL-1 operation regime connected with wall conditioning and MHD studies was successfully finished in 1989. The lowest {ital q}({ital a}) of 1.8 has been successfully obtained. The reproducibility of the plasma is quite good for detailed research. The program of the second part was to address the improvement of plasma confinement with the emphasis on boundary plasma studies. The typical improvement factors of confinement are: particle confinement time is increased by a factor of 2 to 3 and plasma energy confinement time is increased by 1.7. The ECRH, LHCD at several kilowatts and Pellet Injection experiments have been carried out on the HL-1 Tokamak. The improvement of confinement has been observed in all investigated cases except during ECRH and the LHCD/plasma biasing combined experiments. In the latter case, the plasma confinement results to be poor for unknown reasons. The results of inert-gas-filled discharged cleaning and molecular injection using the Laval Nozzle are also reported in this paper. {copyright} {ital 1995 American Institute of Physics.}

  6. CE Geothermal | Open Energy Information

    Open Energy Info (EERE)

    Geothermal Jump to: navigation, search Name: CE Geothermal Place: California Sector: Geothermal energy Product: CE Geothermal previously owned the assets of Western States...

  7. Millimeter image of the HL Tau Disk: gaps opened by planets?...

    Office of Scientific and Technical Information (OSTI)

    Citation Details In-Document Search Title: Millimeter image of the HL Tau Disk: gaps opened by planets? Authors: Li, Hui 1 + Show Author Affiliations Los Alamos National ...

  8. The Discharge Design of HL-2M with the Tokamak Simulation Code (TSC)

    SciTech Connect (OSTI)

    Yudong Pan, S.C. Jardin, and C. Kes

    2007-10-10

    We present results on the discharge design of the HL-2M tokamak, which is to be an upgrade to the existing HL-2A tokamak. We present simulation results for complete 5-sec. discharges, both double null and lower single null, for both ohmic and auxiliary heated discharges. We also discuss the vertical stability properties of the device. __________________________________________________

  9. International Refrigeration: Order (2012-CE-1510) | Department...

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

    International Refrigeration: Order (2012-CE-1510) International Refrigeration: Order (2012-CE-1510) July 20, 2012 DOE ordered International Refrigeration Products to pay an 8,000 ...

  10. CE Solar | Open Energy Information

    Open Energy Info (EERE)

    Czech Republic Zip: 686 01 Product: Czech PV system integrator primarily building plants for Energy 21 in the Czech Republic. References: CE Solar1 This article is a stub....

  11. CRAD, NNSA - Conduct of Engineering (CE) | Department of Energy

    Office of Environmental Management (EM)

    Conduct of Engineering (CE) CRAD, NNSA - Conduct of Engineering (CE) CRAD for Conduct of Engineering (CE). Criteria Review and Approach Documents (CRADs) that can be used to...

  12. Almo: Order (2012-CE-1416) | Department of Energy

    Broader source: Energy.gov (indexed) [DOE]

    PDF icon 2012-CE-1416AlmoOrder More Documents & Publications Almo: Proposed Penalty (2012-CE-1416) International Refrigeration: Order (2012-CE-1510) Commercial Display Systems: ...

  13. School Air: Proposed Penalty (2016-CE-43004) | Department of...

    Energy Savers [EERE]

    School Air: Proposed Penalty (2016-CE-43004) (15.74 KB) More Documents & Publications School Air: Order (2016-CE-43004) Temspec: Proposed Penalty (2016-CE-43002) Crane: Proposed ...

  14. Atosa: Proposed Penalty (2015-CE-42037) | Department of Energy

    Broader source: Energy.gov (indexed) [DOE]

    Atosa: Proposed Penalty (2015-CE-42037) (15.43 KB) More Documents & Publications Atosa: Order (2015-CE-42037) Utility: Proposed Penalty (2016-CE-42007) Crane: Proposed Penalty ...

  15. RPI: Proposed Penalty (2015-CE-42065) | Department of Energy

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

    RPI: Proposed Penalty (2015-CE-42065) (16.14 KB) More Documents & Publications RPI: Order (2015-CE-42065) Utility: Proposed Penalty (2016-CE-42007) Crane: Proposed Penalty ...

  16. Minimum Fisher regularization of image reconstruction for infrared imaging bolometer on HL-2A

    SciTech Connect (OSTI)

    Gao, J. M.; Liu, Y.; Li, W.; Lu, J.; Dong, Y. B.; Xia, Z. W.; Yi, P.; Yang, Q. W.

    2013-09-15

    An infrared imaging bolometer diagnostic has been developed recently for the HL-2A tokamak to measure the temporal and spatial distribution of plasma radiation. The three-dimensional tomography, reduced to a two-dimensional problem by the assumption of plasma radiation toroidal symmetry, has been performed. A three-dimensional geometry matrix is calculated with the one-dimensional pencil beam approximation. The solid angles viewed by the detector elements are taken into account in defining the chord brightness. And the local plasma emission is obtained by inverting the measured brightness with the minimum Fisher regularization method. A typical HL-2A plasma radiation model was chosen to optimize a regularization parameter on the criterion of generalized cross validation. Finally, this method was applied to HL-2A experiments, demonstrating the plasma radiated power density distribution in limiter and divertor discharges.

  17. Optics of ion beams for the neutral beam injection system on HL-2A Tokamak

    SciTech Connect (OSTI)

    Zou, G. Q.; Lei, G. J.; Cao, J. Y.; Duan, X. R.

    2012-07-15

    The ion beam optics for the neutral beam injection system on HL-2A Tokomak is studied by two- dimensional numerical simulation program firstly, where the emitting surface is taken at 100 Debye lengths from the plasma electrode. The mathematical formulation, computation techniques are described. Typical ion orbits, equipotential contours, and emittance diagram are shown. For a fixed geometry electrode, the effect of plasma density, plasma potential and plasma electron temperature on ion beam optics is examined, and the calculation reliability is confirmed by experimental results. In order to improve ion beam optics, the application of a small pre-acceleration voltage ({approx}100 V) between the plasma electrode and the arc discharge anode is reasonable, and a lower plasma electron temperature is desired. The results allow optimization of the ion beam optics in the neutral beam injection system on HL-2A Tokomak and provide guidelines for designing future neutral beam injection system on HL-2M Tokomak.

  18. HL-217, a new topical anti-angiogenic agent, inhibits retinal vascular leakage and pathogenic subretinal neovascularization in Vldlr{sup ?/?} mice

    SciTech Connect (OSTI)

    Kim, Junghyun; Kim, Chan-Sik; Jo, Kyuhyung; Cho, Yun-Seok; Kim, Hyun-Gyu; Lee, Geun-Hyeog; Lee, Yun Mi; Sohn, Eunjin; Kim, Jin Sook

    2015-01-02

    Highlights: HL-217 is a new synthetic topical anti-angiogenic agent. HL-217 attenuated subretinal neovascularization in Vldlr{sup ?/?} mice. HL-217 blocked the binding of PDGF-BB to PDGFR?. - Abstract: HL-217 is a new synthetic angiogenesis inhibitor. Platelet derived growth factor (PDGF) is a vasoactive factor and has been implicated in proliferative retinopathies. In this study, we examined the mechanism of action and efficacy of topical application of HL-217 on subretinal neovascularization in very low-density lipoprotein receptor knockout (Vldlr{sup ?/?}) mice. In three-week-old male Vldlr{sup ?/?} mice, HL-217 (1.5 or 3 mg/ml) was administered twice per day for 4 weeks by topical eye drop instillation. Neovascular areas were then measured. We used a protein array to evaluate the expression levels of angiogenic factors. The inhibitory effect of HL-217 on the PDGF-BB/PDGFR? interaction was evaluated in vitro. The neovascular area in the Vldlr{sup ?/?} mice was significantly reduced by HL-217. Additionally, HL-217 decreased the expression levels of PDGF-BB protein and VEGF mRNA. Moreover, HL-217 dose-dependently inhibited the PDGF-BB/PDGFR? interaction (IC{sub 50} = 38.9 0.7 ?M). These results suggest that HL-217 is a potent inhibitor of PDGF-BB. HL-217, when applied topically, is an effective inhibitor of subretinal neovascularization due to its ability to inhibit the pro-angiogenic effects of PDGF-BB.

  19. CE: Proposed Penalty (2013-SE-1429)

    Broader source: Energy.gov [DOE]

    DOE alleged in a Notice of Proposed Civil Penalty that CE North America, LLC, privately labeled and distributed noncompliant freezers in the U.S.

  20. CE: Compromise Agreement (2013-SE-1429)

    Broader source: Energy.gov [DOE]

    DOE and CE North America entered into a Compromise Agreement to resolve a case involving the distribution in commerce of noncompliant freezers.

  1. Photoelectron spectra of CeO{sup −} and Ce(OH){sub 2}{sup −}

    SciTech Connect (OSTI)

    Ray, Manisha; Felton, Jeremy A.; Kafader, Jared O.; Topolski, Josey E.; Jarrold, Caroline Chick

    2015-02-14

    The photoelectron spectrum of CeO{sup −} exhibits what appears to be a single predominant electronic transition over an energy range in which numerous close-lying electronic states of CeO neutral are well known. The photoelectron spectrum of Ce(OH){sub 2}{sup −}, a molecule in which the Ce atom shares the same formal oxidation state as the Ce atom in CeO{sup −}, also exhibits what appears to be a single transition. From the spectra, the adiabatic electron affinities of CeO and Ce(OH){sub 2} are determined to be 0.936 ± 0.007 eV and 0.69 ± 0.03 eV, respectively. From the electron affinity of CeO, the CeO{sup −} bond dissociation energy was determined to be 7.7 eV, 0.5 eV lower than the neutral bond dissociation energy. The ground state orbital occupancies of both CeO{sup −} and Ce(OH){sub 2}{sup −} are calculated to have 4f 6s{sup 2} Ce{sup +} superconfigurations, with open-shell states having 4f5d6s superconfiguration predicted to be over 1 eV higher in energy. Low-intensity transitions observed at higher electron binding energies in the spectrum of CeO{sup −} are tentatively assigned to the {sup 1}Σ{sup +} (Ω = 0) state of CeO with the Ce{sup +2}⍰6s{sup 2} superconfiguration.

  2. A new neutral particle analyzer diagnostic and its first commissioning on HL-2A

    SciTech Connect (OSTI)

    Li, W.; Xia, Z. W.; Lu, J.; Yang, Q. W.; Ding, X. T.

    2012-10-15

    A new neutral particle analyzer diagnostic has been developed for HuanLiuqi-2A (commonly referred to as HL-2A), which can provide the neutral particle flux measurement along 11 separate sightlines, simultaneously, within a wider energy range (1-70 keV). It is an electrostatic type analyzer with a removable pinhole and special-shape condenser. The energy analysis can be flexibly achieved by controlling a preset stepwise high voltage on the condenser. It is compact and its field of view covers HL-2A cross section from -33 cm to 33 cm without 'cross-talk.' The energy spectra and ion temperature profile have been obtained during its commissioning.

  3. Numerical studies of electron cyclotron wave current drive on HL-2A tokamak

    SciTech Connect (OSTI)

    Li, J. C.; Gong, X. Y.; Dong, J. Q.; Song, S. D.; Gao, Q. D.; Zheng, P. W.; Du, D.

    2015-06-15

    The electron cyclotron wave (ECW) current drive (CD) for the HL-2A tokamak is investigated numerically with a new ray-tracing and Fokker-Planck code. The code is benchmarked with other well-tested linear and quasilinear codes and is then used to study the electron cyclotron current drive on the HL-2A tokamak. The wave propagation, power deposition, and driven-current profiles are presented. The effect of electron trapping is also assessed. It is found that quasilinear effects are negligible at the present ECW power levels and that when both waves are injected at an angle of 20° on the plasma equatorial plane, the CD efficiency for the HL-2A saturates at ∼0.029 × 10{sup 20 }A/W/m{sup 2} and ∼0.020 × 10{sup 20 }A/W/m{sup 2} for the 0.5 MW/68 GHz first harmonic ordinary (O1) and 1 MW/140 GHz second harmonic extraordinary (X2) modes, respectively. The effects of the plasma density, temperature, and wave-launching position on the driven current are also investigated analytically and numerically.

  4. California Ethanol Power CE P | Open Energy Information

    Open Energy Info (EERE)

    Power CE P Jump to: navigation, search Name: California Ethanol & Power (CE+P) Place: Florida Product: US ethanol project developer. References: California Ethanol & Power...

  5. Palmetto Clean Energy (PaCE) Program

    Office of Energy Efficiency and Renewable Energy (EERE)

    PaCE funding comes from the customers of participating utilities who voluntarily choose to support the program through an additional charge on their monthly utility bills. Of the $4, $3.50 goes t...

  6. CeCap LLP | Open Energy Information

    Open Energy Info (EERE)

    Name: CeCap LLP Place: London, United Kingdom Zip: W1S 2LQ Product: London-based investment boutique which provides investment advice to, and invests in, small to mediun size...

  7. Hybridized Nature of Pseudogap in Kondo Insulators CeRhSb and CeRhAs

    SciTech Connect (OSTI)

    Kumigashira, H.; Takahashi, T.; Yoshii, S.; Kasaya, M.

    2001-08-06

    We studied the electronic structure of Kondo insulators CeRhSb and CeRhAs using high-resolution photoemission spectroscopy. We found that the 4f -derived density of states shows a depletion (pseudogap) at E{sub F} in contrast to metallic Kondo materials. It was found that the size of the f pseudogap is smaller than that of conduction electrons (c pseudogap) while both scale well with the Kondo temperature. The present results indicate that the hybridization between 4f and conduction electrons near E{sub F} is essential for the Kondo gap in the Ce-based compounds.

  8. Goodman Manufacturing: Order (2012-CE-1509) | Department of Energy

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

    2-CE-1509) Goodman Manufacturing: Order (2012-CE-1509) August 7, 2012 DOE ordered Goodman Manufacturing Company L.P. to pay an 8,000 civil penalty after finding Goodman...

  9. L1 track triggers for ATLAS in the HL-LHC

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

    Lipeles, E.

    2012-01-01

    The HL-LHC, the planned high luminosity upgrade for the LHC, will increase the collision rate in the ATLAS detector approximately a factor of 5 beyond the luminosity for which the detectors were designed, while also increasing the number of pile-up collisions in each event by a similar factor. This means that the level-1 trigger must achieve a higher rejection factor in a more difficult environment. This presentation discusses the challenges that arise in this environment and strategies being considered by ATLAS to include information from the tracking systems in the level-1 decision. The main challenges involve reducing the data volumemore » exported from the tracking system for which two options are under consideration: a region of interest based system and an intelligent sensor method which filters on hits likely to come from higher transverse momentum tracks.« less

  10. Spin reorientation and Ce-Mn coupling in antiferromagnetic oxypnictide CeMnAsO

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

    Zhang, Qiang; Tian, Wei; Peterson, Spencer G.; Dennis, Kevin W.; Vaknin, David

    2015-02-18

    Structure and magnetic properties of high-quality polycrystlline CeMnAsO, a parent compound of the “1111”-type oxypnictides, have been investigated using neutron powder diffraction and magnetization measurements. We find that CeMnAsO undergoes a C-type antiferromagnetic order with Mn2+(S = 5/2) moments pointing along the c axis below a relatively high Néel temperature of TN = 347(1) K. Below TSR = 35 K, two simultaneous transitions occur where the Mn moments reorient from the c axis to the ab plane preserving the C-type magnetic order, and Ce moments undergo long-range AFM ordering with antiparallel moments pointing in the ab plane. Another transition tomore » a noncollinear magnetic structure occurs below 7 K. The ordered moments of Mn and Ce at 2 K are 3.32(4) μB and 0.81(4)μB, respectively. We find that CeMnAsO primarily falls into the category of a local-moment antiferromagnetic insulator in which the nearest-neighbor interaction (J1) is dominant with J2 < J1/2 in the context of J1 – J2 – Jc model. The spin reorientation transition driven by the coupling between Ce and the transition metal seems to be common to Mn, Fe, and Cr ions, but not to Co and Ni ions in the isostructural oxypnictides. As a result, a schematic illustration of magnetic structures in Mn and Ce sublattices in CeMnAsO is presented.« less

  11. Utility: Order (2016-CE-42007) | Department of Energy

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

    CE-42007) Utility: Order (2016-CE-42007) January 5, 2016 DOE ordered Utility Refrigerator to pay a $8,000 civil penalty after finding Utility had failed to certify that certain models of commercial refrigerator equipment comply with the applicable energy conservation standards. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and Utility. Utility: Order (2016-CE-42007) (22.13 KB) More Documents & Publications Utility: Proposed Penalty (2016-CE-42007) Bu

  12. RPI: Order (2015-CE-42065) | Department of Energy

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

    Order (2015-CE-42065) RPI: Order (2015-CE-42065) November 6, 2015 DOE ordered RPI Industries, Inc. to pay a $8,000 civil penalty after finding RPI had failed to certify that certain models of commercial refrigeration equipment comply with the applicable energy conservation standards. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and RPI. RPI: Order (2015-CE-42065) (21.12 KB) More Documents & Publications RPI: Proposed Penalty (2015-CE-42065) Wolverine

  13. Water Dissociation on CeO2(100) and CeO2(111) Thin Films

    SciTech Connect (OSTI)

    Mullins, David R; Albrecht, Peter M; Chen, Tsung-Liang; Calaza, Florencia C; Biegalski, Micahel; Christen, Hans; Overbury, Steven {Steve} H

    2012-01-01

    This study reports and compares the adsorption and dissociation of water on oxidized and reduced CeO{sub 2}(100) and CeO{sub 2}(111) thin films. Water adsorbs dissociatively on both surfaces. On fully oxidized CeO{sub 2}(100) the resulting surface hydroxyls are relatively stable and recombine and desorb as water over a range from 200 to 600 K. The hydroxyls are much less stable on oxidized CeO{sub 2}(111), recombining and desorbing between 200 and 300 K. Water produces 30% more hydroxyls on reduced CeO{sub 1.7}(100) than on oxidized CeO{sub 2}(100). The hydroxyl concentration increases by 160% on reduced CeO{sub 1.7}(111) compared to oxidized CeO{sub 2}(111). On reduced CeO{sub 1.7}(100) most of the hydroxyls still recombine and desorb as water between 200 and 750 K. Most of the hydroxyls on reduced CeO{sub 1.7}(111) react to produce H{sub 2} at 560 K, leaving O on the surface. A relatively small amount of H{sub 2} is produced from reduced CeO{sub 1.7}(100) between 450 and 730 K. The differences in the adsorption and reaction of water on CeO{sub X}(100) and CeO{sub X}(111) are attributed to different adsorption sites on the two surfaces. The adsorption site on CeO{sub 2}(100) is a bridging site between two Ce cations. This adsorption site does not change when the ceria is reduced. The adsorption site on CeO{sub 2}(111) is atop a single Ce cation, and the proton is transferred to a surface O in a site between three Ce cations. When the CeO{sub X}(111) is reduced, vacancy sites are produced which allows the water to adsorb and dissociate on the 3-fold Ce cation sites.

  14. Role of Ce4+ in the scintillation mechanism of codoped Gd3Ga3Al2O12:Ce

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

    Wu, Yuntao; Meng, Fang; Li, Qi; Koschan, Merry; Melcher, Charles L.

    2014-10-17

    To control the time-response performance of widely used cerium-activated scintillators in cutting-edge medical-imaging devices, such as time-of-flight positron-emission tomography, a comprehensive understanding of the role of Ce valence states, especially stable Ce4+, in the scintillation mechanism is essential. However, despite some progress made recently, an understanding of the physical processes involving Ce4+ is still lacking. The aim of this work is to clarify the role of Ce4+ in scintillators by studying Ca2+ codoped Gd3Ga3Al2O12∶Ce (GGAG∶Ce). By using a combination of optical absorption spectra and x-ray absorption near-edge spectroscopies, the correlation between Ca2+codoping content and the Ce4+ fraction is seen. The energy-levelmore »diagrams of Ce3+ and Ce4+ in the Gd3Ga3Al2O12 host are established by using theoretical and experimental methods, which indicate a higher position of the 5d1 state of Ce4+ in the forbidden gap in comparison to that of Ce3+. Underlying reasons for the decay-time acceleration resulting from Ca2+ codoping are revealed, and the physical processes of the Ce4+-emission model are proposed and further demonstrated by temperature-dependent radioluminescence spectra under x-ray excitation.« less

  15. Role of Ce4+ in the scintillation mechanism of codoped Gd3Ga3Al2O12:Ce

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

    Wu, Yuntao; Meng, Fang; Li, Qi; Koschan, Merry; Melcher, Charles L.

    2014-10-17

    To control the time-response performance of widely used cerium-activated scintillators in cutting-edge medical-imaging devices, such as time-of-flight positron-emission tomography, a comprehensive understanding of the role of Ce valence states, especially stable Ce4+, in the scintillation mechanism is essential. However, despite some progress made recently, an understanding of the physical processes involving Ce4+ is still lacking. The aim of this work is to clarify the role of Ce4+ in scintillators by studying Ca2+ codoped Gd3Ga3Al2O12∶Ce (GGAG∶Ce). By using a combination of optical absorption spectra and x-ray absorption near-edge spectroscopies, the correlation between Ca2+codoping content and the Ce4+ fraction is seen. The energy-levelmore » diagrams of Ce3+ and Ce4+ in the Gd3Ga3Al2O12 host are established by using theoretical and experimental methods, which indicate a higher position of the 5d1 state of Ce4+ in the forbidden gap in comparison to that of Ce3+. Underlying reasons for the decay-time acceleration resulting from Ca2+ codoping are revealed, and the physical processes of the Ce4+-emission model are proposed and further demonstrated by temperature-dependent radioluminescence spectra under x-ray excitation.« less

  16. Laboratory and testbeam results for thin and epitaxial planar sensors for HL-LHC

    SciTech Connect (OSTI)

    Bubna, M.; Bolla, G.; Bortoletto, D.; Shipsey, I.; Manfra, M.; Khan, K.; Arndt, K.; Hinton, N.; Godshalk, A.; Kumar, A.; Menasce, D.; Moroni, L.; Chramowicz, J.; Lei, C. M.; Prosser, A.; Rivera, R.; Uplegger, L.; Vetere, Maurizio Lo; Robutti, Enrico; Ferro, Fabrizio; Ravera, Fabio; Costa, Marco

    2015-08-03

    The High-Luminosity LHC (HL-LHC) upgrade of the CMS pixel detector will require the development of novel pixel sensors which can withstand the increase in instantaneous luminosity to L = 5 × 1034 cm–2s–1 and collect ~ 3000fb–1 of data. The innermost layer of the pixel detector will be exposed to doses of about 1016 neq/ cm2. Hence, new pixel sensors with improved radiation hardness need to be investigated. A variety of silicon materials (Float-zone, Magnetic Czochralski and Epitaxially grown silicon), with thicknesses from 50 μm to 320 μm in p-type and n-type substrates have been fabricated using single-sided processing. The effect of reducing the sensor active thickness to improve radiation hardness by using various techniques (deep diffusion, wafer thinning, or growing epitaxial silicon on a handle wafer) has been studied. Furthermore, the results for electrical characterization, charge collection efficiency, and position resolution of various n-on-p pixel sensors with different substrates and different pixel geometries (different bias dot gaps and pixel implant sizes) will be presented.

  17. The motional Stark effect polarimeter in the HL-2A tokamak

    SciTech Connect (OSTI)

    Yu, D. L. Wei, Y. L.; Xia, F.; Cao, J. Y.; Chen, C. Y.; Liu, L.; Chen, W. J.; Ji, X. Q.; Liu, Y.; Yan, L. W.; Yang, Q. W.; Duan, X. R.

    2014-05-15

    A 7-channel motional Stark effect polarimeter based on four polarizers and a spectrometer has been developed in the HL-2A tokamak, which is the first time successful utilizing this kind of polarimeter on a tokamak. The accuracy of the angle can reach ±0.25° in the calibration experiments. Pilot experiments of measuring the magnetic pitch angle have been successfully carried out in the weak motional Stark effect plasma discharge with toroidal magnetic field of ∼1.3 T and beam energy of ∼25 keV/amu. The pitch angles of magnetic field are obtained for 7 spatial points covering 24 cm along major radius with time resolution of 40 ms; the profiles of safety factor are obtained by combining with the Equilibrium and Reconstruction Fitting Code. The core value of safety factor (q) is less than 1 during the sawtooth oscillation and the position of q = 1 surface is well consistent with the results measured by soft X-ray array.

  18. Laboratory and testbeam results for thin and epitaxial planar sensors for HL-LHC

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

    Bubna, M.; Bolla, G.; Bortoletto, D.; Shipsey, I.; Manfra, M.; Khan, K.; Arndt, K.; Hinton, N.; Godshalk, A.; Kumar, A.; et al

    2015-08-03

    The High-Luminosity LHC (HL-LHC) upgrade of the CMS pixel detector will require the development of novel pixel sensors which can withstand the increase in instantaneous luminosity to L = 5 × 1034 cm–2s–1 and collect ~ 3000fb–1 of data. The innermost layer of the pixel detector will be exposed to doses of about 1016 neq/ cm2. Hence, new pixel sensors with improved radiation hardness need to be investigated. A variety of silicon materials (Float-zone, Magnetic Czochralski and Epitaxially grown silicon), with thicknesses from 50 μm to 320 μm in p-type and n-type substrates have been fabricated using single-sided processing. The effect ofmore » reducing the sensor active thickness to improve radiation hardness by using various techniques (deep diffusion, wafer thinning, or growing epitaxial silicon on a handle wafer) has been studied. Furthermore, the results for electrical characterization, charge collection efficiency, and position resolution of various n-on-p pixel sensors with different substrates and different pixel geometries (different bias dot gaps and pixel implant sizes) will be presented.« less

  19. Crane: Order (2016-CE-52001) | Department of Energy

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

    Order (2016-CE-52001) Crane: Order (2016-CE-52001) January 21, 2016 DOE ordered Crane Merchandising Systems, Inc. to pay a $16,000 civil penalty after finding Crane had failed to certify that certain models of refrigerated bottled or canned beverage vending machines comply with the applicable energy conservation standards. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and Crane. Crane: Order (2016-CE-52001) (23.16 KB) More Documents & Publications

  20. Atosa: Order (2015-CE-42037) | Department of Energy

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

    Order (2015-CE-42037) Atosa: Order (2015-CE-42037) August 31, 2015 DOE ordered Atosa Catering Equipment, Inc. to pay a $8,000 civil penalty after finding Atosa had failed to certify that certain models of self-contained commercial refrigeration equipment with doors comply with the applicable energy conservation standards. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and Atosa. Atosa: Order (2015-CE-42037) (26.71 KB) More Documents & Publications

  1. Herbeau: Order (2015-CE-28005) | Department of Energy

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

    Order (2015-CE-28005) Herbeau: Order (2015-CE-28005) March 9, 2016 DOE ordered Herbeau Creations of America, Inc. to pay a $8,000 civil penalty after finding Herbeau had failed to certify that certain models of faucets and showerheads comply with the applicable water conservation standards. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and Herbeau. Herbeau: Order (2015-CE-28005) (16.61 KB) More Documents & Publications Herbeau: Proposed Penalty

  2. Temspec: Order (2016-CE-43002) | Department of Energy

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

    Order (2016-CE-43002) Temspec: Order (2016-CE-43002) March 21, 2016 DOE ordered Temspec Incorporated to pay a $8,000 civil penalty after finding Temspec had failed to certify that certain models of single package vertical air conditioning and heating equipment comply with the applicable energy conservation standards. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and Temspec. Temspec: Order (2016-CE-43002) (92.11 KB) More Documents & Publications

  3. CE2 Capital Partners LLC | Open Energy Information

    Open Energy Info (EERE)

    Capital Partners LLC Jump to: navigation, search Name: CE2 Capital Partners LLC Place: Solana Beach, California Zip: 92075 Sector: Carbon, Renewable Energy Product:...

  4. PQL: Order (2013-CE-27001) | Department of Energy

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

    PQL: Order (2013-CE-27001) PQL: Order (2013-CE-27001) August 7, 2015 DOE ordered P.Q.L, Inc. to pay a $12,500 civil penalty after finding PQL had failed to certify that certain models of medium base compact fluorescent lamps comply with the applicable energy conservation standards. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and PQL. PQL: Order (2013-CE-27001) (17.34 KB) More Documents & Publications PQL: Proposed Penalty (2013-CE-27001) PQL: Order

  5. Thermoelectric Couple Demonstration of (In, Ce)-based Skutterudite...

    Broader source: Energy.gov (indexed) [DOE]

    Presents recent accomplishments and couple test results with these (In, Ce)-based skutterudite TE materials and potential impacts TE power system performance in military and ...

  6. Lattice Disorder And Size-Induced Kondo Behavior in CeAl(2) And CePt(2+X)

    SciTech Connect (OSTI)

    Han, S.-W.; Booth, C.H.; Bauer, E.D.; Huang, P.H.; Chen, Y.Y.; Lawrence, J.M.; /LBL, Berkeley /Chonbuk Natl. U. /Los Alamos /Taiwan, Inst. Phys. /UC, Irvine

    2007-07-19

    When the particle size of CeAl{sub 2} and CePt{sub 2+x} samples is reduced to the nanometer scale, antiferromagnetism is suppressed and Kondo behavior dominates. We find that the Kondo temperature T{sub K} can either decrease (CeAl{sub 2}) or increase (CePt{sub 2+x}) in the nanoparticles relative to the bulk. Extended x-ray absorption fine-structure data show that the Ce-Al and Ce-Pt environments are significantly distorted in the nanoparticles. While such distortions should strongly affect magnetic and electronic properties, we find they cannot explain the observed changes in T{sub K}. Changes in the conduction density of states or other parameters must, therefore, play a significant role.

  7. Lattice disorder and size-induced Kondo behavior in CeAl2 andCePt2+x

    SciTech Connect (OSTI)

    Han, S.-W.; Booth, C.H.; Bauer, E.D.; Huang P.H.; Chen, Y.Y.; Lawrence, J.M.

    2006-03-14

    When the particle size of CeAl{sub 2} and CePt{sub 2+x} samples is reduced to the nanometer scale, antiferromagnetism is suppressed and Kondo behavior dominates. We find that the Kondo temperature T{sub K} can either decrease (CeAl{sub 2}) or increase (CePt{sub 2+x}) in the nanoparticles relative to the bulk. Extended x-ray absorption fine-structure data show that the Ce-Al and Ce-Pt environments are significantly distorted in the nanoparticles. While such distortions should strongly affect magnetic and electronic properties, we find they cannot explain the observed changes in T{sub K}. Changes in the conduction density of states or other parameters must, therefore, play a significant role.

  8. Processing of transparent polycrystalline AlON:Ce3+ scintillators

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

    Chen, Ching -Fong; Yang, Pin; King, Graham; Tegtmeier, Eric L.

    2015-10-23

    A new polycrystalline ceramic scintillator is reported for potential use in radiation detection and medical imaging applications. The goal was to develop cerium-activated aluminum oxynitride (AlON:Ce3+) ceramics, which can be produced using ceramic processes in comparison to the high-cost, low-yield single-crystal growth technique. A phase pure AlON:Ce3+ powder with cubic symmetry was successfully synthesized at high temperature under a reducing atmosphere to convert Ce4+ to Ce3+ in the solid solution. We explored two different activator concentrations (0.5 and 1.0 mol%). Fully dense and transparent AlON:Ce3+ ceramics were produced by a liquid-phase-assisted pressureless sintering. The crystal field splitting around the Ce3+more » activator in the AlON was comparable to the splitting induced by Br₋ and the Cl₋ ligands, which produced an emission spectrum perfectly matching the maximum quantum efficiency range of the photomultiplier tube for radiation detection. Both optical excitation and radiation ionizations in AlON:Ce3+ were demonstrated. Lastly, challenges and mechanisms related to the radioluminescence efficiency are discussed.« less

  9. Evidence of dynamical spin shielding in Ce from spin-resolved...

    Office of Scientific and Technical Information (OSTI)

    Evidence of dynamical spin shielding in Ce from spin-resolved photoelectron spectroscopy Citation Details In-Document Search Title: Evidence of dynamical spin shielding in Ce from ...

  10. Maxlite: Order (2010-CE-2701) | Department of Energy

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

    Maxlite: Order (2010-CE-2701) Maxlite: Order (2010-CE-2701) In the Matter of Maxlite, SK America, Inc. (general service flourescent lamps), DOE Case Number 2010-CE-2701, Adopting Order and Compromise Agreement. Order adopting accompanying Compromise Agreement. DOE found that Maxlite failed to submit compliance certifications for its products under 10 C.F.R. Section 430.62, and here assesses a civil penalty of $5,000 (if paid within 30 days) or of $10,000 (if paid between 31-60 days). Maxlite

  11. Paragon Sales: Order (2012-CE-1417) | Department of Energy

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

    Order (2012-CE-1417) July 30, 2012 DOE ordered Paragon Sales Co., Inc., to pay a 6,000 civil penalty after finding Paragon Sales had failed to certify that certain models of...

  12. Manitowoc Foodservice: Order (2012-CE-5309) | Department of Energy

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

    Order (2012-CE-5309) July 20, 2012 DOE ordered Manitowoc Foodservice to pay an 6,000 civil penalty after finding Manitowoc Foodservice had failed to certify that Manitowoc...

  13. Electrolux: Order (2012-CE-1901) | Department of Energy

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

    Order (2012-CE-1901) July 27, 2012 DOE ordered Electrolux North America to pay a 6,500 civil penalty after finding Electrolux had failed to certify that certain dishwashers comply...

  14. Haier: Order (2011-CE-2104) | Department of Energy

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

    Haier: Order (2011-CE-2104) June 12, 2012 DOE ordered Haier to pay an 20,000 civil penalty after finding Haier had failed to certify that Haier residential clothes...

  15. Danby Products: Order (2012-CE-1415) | Department of Energy

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

    Order (2012-CE-1415) August 9, 2012 DOE ordered Danby Products to pay a 9,900 civil penalty after finding Danby had failed to certify that certain models of refrigerators...

  16. CE2 Carbon Capital LLC | Open Energy Information

    Open Energy Info (EERE)

    Carbon Capital LLC Jump to: navigation, search Name: CE2 Carbon Capital LLC Place: California Sector: Carbon, Renewable Energy Product: US-based carbon trader that looks to take...

  17. Utility: Proposed Penalty (2016-CE-42007) | Department of Energy

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

    Proposed Penalty (2016-CE-42007) Utility: Proposed Penalty (2016-CE-42007) November 30, 2015 DOE alleged in a Notice of Proposed Civil Penalty that Utility Refrigerator failed to certify certain commercial refrigerator equipment as compliant with the applicable energy conservation standards. DOE regulations require a manufacturer (which includes importers) to submit reports certifying that its products have been tested and meet the applicable energy conservation standards. This civil penalty

  18. Fujitsu: Order (2015-CE-16014) | Department of Energy

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

    Fujitsu: Order (2015-CE-16014) Fujitsu: Order (2015-CE-16014) October 27, 2015 DOE ordered Fujitsu General America, Inc. to pay a $8,000 civil penalty after finding Fujitsu had failed to certify that certain models of central air conditioners and heat pumps comply with the applicable energy conservation standards prior to distributing them in commerce. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and Fujitsu. DOE regulations require a manufacturer (which

  19. Lochinvar: Order (2016-CE-24001) | Department of Energy

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

    Lochinvar: Order (2016-CE-24001) Lochinvar: Order (2016-CE-24001) November 2, 2015 DOE ordered Lochinvar, LLC, to pay a $8,000 civil penalty after finding Lochinvar had failed to certify that certain models of pool heaters comply with the applicable energy conservation standard. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and Lochinvar. DOE regulations require a manufacturer (which includes importers) to submit reports certifying that its products have

  20. Systemair: Order (2016-CE-43003) | Department of Energy

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

    Systemair: Order (2016-CE-43003) Systemair: Order (2016-CE-43003) February 23, 2016 DOE ordered Systemair, Inc., to pay a $8,000 civil penalty after finding Systemair had failed to certify that its single package vertical air conditioning and heating equipment comply with the applicable energy conservation standards. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and Systemair. DOE regulations require a manufacturer (which includes importers) to submit

  1. Temspec: Proposed Penalty (2016-CE-43002) | Department of Energy

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

    Proposed Penalty (2016-CE-43002) Temspec: Proposed Penalty (2016-CE-43002) February 5, 2016 DOE alleged in a Notice of Proposed Civil Penalty that Temspec Incorporated failed to certify various basic models of single package vertical air conditioning and heating equipment as compliant with the applicable energy conservation standards. DOE regulations require a manufacturer (which includes importers) to submit reports certifying that its products have been tested and meet the applicable energy

  2. Ca2+-Doped CeBr3 Scintillating Materials

    SciTech Connect (OSTI)

    Guss, Paul; Foster, Michael E.; Wong, Bryan M.; Doty, F. Patrick; Shah, Kanai; Squillante, Michael R.; Shirwadkar, Urmila; Hawrami, Rastgo; Tower, Josh; Yuan, Ding

    2014-01-21

    Despite the outstanding scintillation performance characteristics of cerium tribromide (CeBr3) and cerium-activated lanthanum tribromide, their commercial availability and application are limited due to the difficulties of growing large, crack-free single crystals from these fragile materials. This investigation employed aliovalent doping to increase crystal strength while maintaining the optical properties of the crystal. One divalent dopant (Ca2+) was used as a dopant to strengthen CeBr3 without negatively impacting scintillation performance. Ingots containing nominal concentrations of 1.9% of the Ca2+ dopant were grown. Preliminary scintillation measurements are presented for this aliovalently doped scintillator. Ca2+-doped CeBr3 exhibited little or no change in the peak fluorescence emission for 371 nm optical excitation for CeBr3. The structural, electronic, and optical properties of CeBr3 crystals were studied using the density functional theory within the generalized gradient approximation. The calculated lattice parameters are in good agreement with the experimental data. The energy band structures and density of states were obtained. The optical properties of CeBr3, including the dielectric function, were calculated.

  3. Development of the scintillator-based probe for fast-ion losses in the HL-2A tokamak

    SciTech Connect (OSTI)

    Zhang, Y. P. Liu, Yi; Yuan, G. L.; Song, X. Y.; Yang, J. W.; Li, X.; Chen, W.; Li, Y.; Yan, L. W.; Song, X. M.; Yang, Q. W.; Duan, X. R.; Luo, X. B.; Liu, Y. Q.; Hua, Y.; Isobe, M.

    2014-05-15

    A new scintillator-based lost fast-ion probe (SLIP) has been developed and operated in the HL-2A tokamak [L. W. Yan, X. R. Duan, X. T. Ding, J. Q. Dong, Q. W. Yang, Yi Liu, X. L. Zou, D. Q. Liu, W. M. Xuan, L. Y. Chen, J. Rao, X. M. Song, Y. Huang, W. C. Mao, Q. M. Wang, Q. Li, Z. Cao, B. Li, J. Y. Cao, G. J. Lei, J. H. Zhang, X. D. Li, W. Chen, J. Chen, C. H. Cui, Z. Y. Cui, Z. C. Deng, Y. B. Dong, B. B. Feng, Q. D. Gao, X. Y. Han, W. Y. Hong, M. Huang, X. Q. Ji, Z. H. Kang, D. F. Kong, T. Lan, G. S. Li, H. J. Li, Qing Li, W. Li, Y. G. Li, A. D. Liu, Z. T. Liu, C. W. Luo, X. H. Mao, Y. D. Pan, J. F. Peng, Z. B. Shi, S. D. Song, X. Y. Song, H. J. Sun, A. K. Wang, M. X. Wang, Y. Q. Wang, W. W. Xiao, Y. F. Xie, L. H. Yao, D. L. Yu, B. S. Yuan, K. J. Zhao, G. W. Zhong, J. Zhou, J. C. Yan, C. X. Yu, C. H. Pan, Y. Liu, and the HL-2A Team , Nucl. Fusion 51, 094016 (2011)] to measure the losses of neutral beam ions. The design of the probe is based on the concept of the ?-particle detectors on Tokamak Fusion Test Reactor (TFTR) using scintillator plates. The probe is capable of traveling across an equatorial plane port and sweeping the aperture angle rotationally with respect to the axis of the probe shaft by two step motors, in order to optimize the radial position and the collimator angle. The energy and the pitch angle of the lost fast ions can be simultaneously measured if the two-dimensional image of scintillation light intensity due to the impact of the lost fast ions is detected. Measurements of the fast-ion losses using the probe have been performed during HL-2A neutral beam injection discharges. The clear experimental evidence of enhanced losses of beam ions during disruptions has been obtained by means of the SLIP system. A detailed description of the probe system and the first experimental results are reported.

  4. Comparison of the high-pressure behavior of the cerium oxides Ce2O3 and CeO2

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

    Lipp, M. J.; Jeffries, J. R.; Cynn, H.; Park Klepeis, J. -H.; Evans, W. J.; Mortensen, D. R.; Seidler, G. T.; Xiao, Y.; Chow, P.

    2016-02-09

    We studied the high-pressure behavior of Ce2O3 using angle-dispersive x-ray diffraction to 70 GPa and compared with that of CeO2. Up to the highest pressure Ce2O3 remains in the hexagonal phase (space group 164, P ¯32/m1) typical for the lanthanide sesquioxides. We did not observe a theoretically predicted phase instability for 30 GPa. The isothermal bulk modulus and its pressure derivative for the quasihydrostatic case are B0 = 111 ± 2 GPa, B'0 = 4.7 ± 0.3, and for the case without pressure-transmitting medium B0 = 104 ±4 GPa, B'0 = 6.5 ± 0.4. Starting from ambient-pressure magnetic susceptibility measurementsmore » for both oxides in highly purified form,we find that the Ce atom in Ce2O3 behaves like a trivalent Ce3+ ion (2.57μB per Ce atom) in contrast to previously published data. Since x-ray emission spectroscopy of the Lγ (4d3/2 → 2p1/2) transition is sensitive to the 4f -electron occupancy, we also followed the high-pressure dependence of this line for both oxides up to 50 GPa. We observed no change of the respective line shape, indicating that the 4f -electron configuration is stable for both materials. We posit from this data that the 4f electrons do not drive the volume collapse of CeO2 from the high-symmetry, low-pressure fluorite structure to the lower-symmetry orthorhombic phase.« less

  5. Effects of CeO2 Support Facets on VOx/CeO2 Catalysts in Oxidative Dehydrogenation of Methanol

    SciTech Connect (OSTI)

    Li, Yan; Wei, Zhehao; Gao, Feng; Kovarik, Libor; Peden, Charles HF; Wang, Yong

    2014-05-13

    CeO2 supports with dominating facets, i.e., low index (100), (110) and (111) facets, are prepared. The facet effects on the structure and catalytic performance of supported vanadium oxide catalysts are investigated using oxidative dehydrogenation of methanol as a model reaction. In the presence of mixed facets, Infrared and Raman characterizations demonstrate that surface vanadia species preferentially deposit on CeO2 (100) facets, presumably because of its higher surface energy. At the same surface vanadium densities, VOx species on (100) facets show better dispersion, followed by (110) and (111) facets. The VOx species on CeO2 nanorods with (110) and (100) facets display higher activity and lower apparent activation energies compared to that on CeO2 nanopolyhedras with dominating (111) facets and CeO2 nanocubes with dominating (100) facets. The higher activity for VOx/CeO2(110) might be related to the more abundant oxygen vacancies present on the (110) facets, evidenced from Raman spectroscopic measurements.

  6. An Update on NiCE Support for BISON

    SciTech Connect (OSTI)

    McCaskey, Alex; Billings, Jay Jay; Deyton, Jordan H.; Wojtowicz, Anna

    2015-09-01

    The Nuclear Energy Advanced Modeling and Simulation program (NEAMS) from the Department of Energy s Office of Nuclear Energy has funded the development of a modeling and simulation workflow environment to support the various codes in its nuclear energy scientific computing toolkit. This NEAMS Integrated Computational Environment (NiCE) provides extensible tools and services that enable efficient code execution, input generation, pre-processing visualizations, and post-simulation data analysis and visualization for a large portion of the NEAMS Toolkit. A strong focus for the NiCE development team throughout FY 2015 has been support for the Multiphysics Object Oriented Simulation Environment (MOOSE) and the NEAMS nuclear fuel performance modeling application built on that environment, BISON. There is a strong desire in the program to enable and facilitate the use of BISON throughout nuclear energy research and industry. A primary result of this desire is the need for strong support for BISON in NiCE. This report will detail improvements to NiCE support for BISON. We will present a new and improved interface for interacting with BISON simulations in a variety of ways: (1) improved input model generation, (2) embedded mesh and solution data visualizations, and (3) local and remote BISON simulation launch. We will also show how NiCE has been extended to provide support for BISON code development.

  7. Homoleptic Ce(III) and Ce(IV) Nitroxide Complexes: Significant Stabilization of the 4+ Oxidation State

    SciTech Connect (OSTI)

    Bogart, Justin A.; Lewis, Andrew J.; Medling, Scott A.; Piro, Nicholas A.; Carroll, Patrick J.; Booth, Corwin H.; Schelter, Eric J.

    2014-06-25

    Electrochemical experiments performed on the complex Ce-IV[2-((BuNO)-Bu-t)py](4), where [2-((BuNO)-Bu-t)py](-) = N-tert-butyl-N-2-pyridylnitroxide, indicate a 2.51 V stabilization of the 4+ oxidation state of Ce compared to [(Bu4N)-Bu-n](2)[Ce(NO3)(6)] in acetonitrile and a 2.95 V stabilization compared to the standard potential for the ion under aqueous conditions. Density functional theory calculations suggest that this preference for the higher oxidation state is a result of the tetrakis(nitroxide) ligand framework at the Ce cation, which allows for effective electron donation into, and partial covalent overlap with, vacant 4f orbitals with delta symmetry. The results speak to the behavior of CeO2 and related solid solutions in oxygen uptake and transport applications, in particular an inherent local character of bonding that stabilizes the 4+ oxidation state. The results indicate a cerium(IV) complex that has been stabilized to an unprecedented degree through tuning of its ligand-field environment.

  8. 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 ...

  9. Effect of Sodium on the Catalytic Properties of VOx/CeO2 Catalysts...

    Office of Scientific and Technical Information (OSTI)

    addition greatly alters the nature of the active sites by V-O-Ce bond cleavage and V-O-Na bond formation, leading to significantly reduced activity of the VOxCeO2 catalysts. ...

  10. SEMI-ANNUAL REPORTS FOR CE FLNG, LLC (CAMBRIDGE) - DK. NO. 12...

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

    CE FLNG, LLC (CAMBRIDGE) - DK. NO. 12-123-LNG - ORDER 3193 SEMI-ANNUAL REPORTS FOR CE FLNG, LLC (CAMBRIDGE) - DK. NO. 12-123-LNG - ORDER 3193 PDF icon April 2013 PDF icon October...

  11. DOI-BLM-ID-110-2009-3825-CE | Open Energy Information

    Open Energy Info (EERE)

    110-2009-3825-CE Jump to: navigation, search NEPA Document Collection for: DOI-BLM-ID-110-2009-3825-CE CX at Crane Creek Geothermal Area for GeothermalExploration Crane Creek...

  12. NMR studies of field induced magnetism in CeCoIn5 (Journal Article...

    Office of Scientific and Technical Information (OSTI)

    Journal Article: NMR studies of field induced magnetism in CeCoIn5 Citation Details In-Document Search Title: NMR studies of field induced magnetism in CeCoIn5 You are accessing ...

  13. Investigation of the physical properties of the tetragonal CeMAl4Si2...

    Office of Scientific and Technical Information (OSTI)

    the tetragonal CeMAl4Si2 (M Rh, Ir, Pt) compounds Prev Next Title: Investigation of the physical properties of the tetragonal CeMAl4Si2 (M Rh, Ir, Pt) compounds The ...

  14. Evaluation of production samples of the scintillators LaBr3:Ce andLaCl3:Ce

    SciTech Connect (OSTI)

    Choong, Woon-Seng; Derenzo, Stephen E.; Moses, William W.

    2005-09-15

    We report on the evaluation of the performance of two recently developed scintillator materials, LaCl{sub 3}:Ce and LaBr{sub 3}:Ce, at the task of gamma ray spectroscopy. Their performance is compared to a standard scintillator used for gamma ray spectroscopy--a 25 mm diameter 25 mm tall cylinder of NaI:Tl. We measure the pulse height, energy resolution, and full-energy efficiency of production LaBr{sub 3}:Ce and LaCl{sub 3}:Ce scintillation crystals of different sizes and geometries for a variety of gamma-ray energies. Using production rather than specially selected crystals will establish whether immediate large-scale use is feasible. The crystal is excited by gamma rays from one of six isotopic sources ({sup 125}I, {sup 241}Am, {sup 57}Co, {sup 22}Na, {sup 137}Cs, and {sup 60}Co) placed 15 cm away from the scintillator. Our measurements show that both LaCl{sub 3} and LaBr{sub 3} outperform NaI:Tl in almost all cases. They outperform NaI:Tl at all energies for the photopeak fraction and counting rate measurements, and for energy resolution at higher energies (above 200 keV for LaCl{sub 3} and 75 keV for LaBr{sub 3}). The performance of production crystals is excellent and these scintillators should be considered for immediate use in systems where stopping power and energy resolution are crucial.

  15. CO Oxidation mechanism on CeO2-supported Au nanoclusters

    SciTech Connect (OSTI)

    Kim H. Y.; Henkelman, G.

    2013-09-08

    To reveal the richer chemistry of CO oxidation by CeO2 supported Au Nanoclusters(NCs)/Nanoparticles, we design Au13 and Au12 supported on a flat and a stepped-CeO2 model (Au/CeO2) and study various kinds of CO oxidation mechanisms at the Au-CeO2 interface and the Au NC as well.

  16. Neutron scattering of CeNi at the SNS-ORNL: A preliminary report

    SciTech Connect (OSTI)

    Mirmelstein, A. [Russian Federal Nuclear Center VNIITF, Snezhinsk, Russia; Podlesnyak, Andrey A [ORNL; Kolesnikov, Alexander I [ORNL; Saporov, B. [Oak Ridge National Laboratory (ORNL); Sefat, A.S. [Oak Ridge National Laboratory (ORNL); Tobin, J. G. [Lawrence Livermore National Laboratory (LLNL)

    2014-01-01

    This is a preliminary report of a neutron scattering experiment used to investigate 4f electron behavior in Ce.

  17. Lattice Disorder and Size-Induced Kondo Behavior in CeAl{sub 2} and CePt{sub 2+x}

    SciTech Connect (OSTI)

    Han, S.-W.; Booth, C. H.; Bauer, E. D.; Huang, P. H.; Chen, Y. Y.; Lawrence, J. M.

    2006-09-01

    When the size of CeAl{sub 2} and CePt{sub 2+x} particles is reduced to the nanometer scale, antiferromagnetism is suppressed and Kondo behavior predominates, with the Kondo temperature T{sub K} either decreasing (CeAl{sub 2}) or increasing (CePt{sub 2+x}) relative to the bulk. Local structure measurements show that these nanoparticles are significantly distorted. While such distortions should strongly affect magnetic and electronic properties, we find they cannot explain the observed changes in T{sub K}. Other size-induced changes to the electronic structure must, therefore, play a significant role.

  18. Thermoelectric Couple Demonstration of (In, Ce)-based Skutterudite

    Broader source: Energy.gov (indexed) [DOE]

    Powered Vehicle | Department of Energy Presentation given at the 16th Directions in Engine-Efficiency and Emissions Research (DEER) Conference in Detroit, MI, September 27-30, 2010. deer10_schock.pdf (2.44 MB) More Documents & Publications Thermoelectric Conversion of Waste Materials for Automotive Energy Recovery | Department of Energy

    Presents recent accomplishments and couple test results with these (In, Ce)-based skutterudite TE materials and potential impacts TE power system

  19. Preparation and thermochromic properties of Ce-doped VO{sub 2} films

    SciTech Connect (OSTI)

    Song, Linwei; Zhang, Yubo; Huang, Wanxia; Shi, Qiwu; Li, Danxia; Zhang, Yang; Xu, Yuanjie

    2013-06-01

    Graphical abstract: This effect of doping concentration on the phase transition temperature of VO{sub 2} films demonstrates that the phase transition temperature is decreasing along with the increase of the Ce dopant concentrations. After doping Ce, the transition temperature of VO{sub 2} film changes appreciably. Highlights: ► Ce-doped VO{sub 2} films were prepared on muscovite substrate by inorganic sol–gel method for the first time. ► The cerium existing in the VO{sub 2} films in the form of Ce{sup 4+} and Ce{sup 3+} was substituted for part of V atoms in the lattice. ► Ce doping could remarkably reduce the particle size of the Ce-doped films compared with undoped films. ► The phase transition temperature of Ce-doped VO{sub 2} films decreased appreciably with maintaining high-quality phase transition. - Abstract: Mixture of cerium (III) nitrate hexahydrate and vanadium pentaoxide powder were used as precursor to prepare Ce-doped VO{sub 2} films on the muscovite substrate by inorganic sol–gel method. SEM, XRD and XPS were used to investigate the morphologies and structures of VO{sub 2} films. The results show that the VO{sub 2} films grow on the muscovite substrate with preferred orientated (0 1 1) plane and the Ce exists in the form of Ce{sup 4+} and Ce{sup 3+} replacing part of V atoms in the lattice. The infrared transmittance change was measured from room temperature to the temperature above the metal–insulator transition. The films have excellent thermochromic performance. The metal–insulator transition temperature of VO{sub 2} films changes appreciably with Ce doped, which decreases by 4.5 °C per 1 at.% doping. Furthermore, Ce doping could remarkably reduce the particle size of VO{sub 2} films.

  20. On the heat capacity of Ce{sub 3}Al

    SciTech Connect (OSTI)

    Singh, Durgesh Samatham, S. Shanmukharao Venkateshwarlu, D. Gangrade, Mohan Ganesan, V.

    2014-04-24

    Electrical resistivity and heat capacity measurements on Cerium based dense Kondo compound Ce{sub 3}Al have been reported. Clear signatures of first order structural transition at 108K, followed by a Kondo minimum and coherence are clearly seen in resistivity. The structural transition is robust and is not affected by magnetic fields. Heat capacity measurements reveal an anomalous enhancement in the heavy fermion character upon magnetic fields. Vollhardt invariance in specific heat C(T.H) curves have been observed at T=3.7K and at H ≈ 6T.

  1. Magnetic properties and photoabsorption of the Mn-doped CeO{sub 2} nanorods

    SciTech Connect (OSTI)

    Xia, Chuanhui; Science College of Chongqing Jiaotong University, Chongqing 400074 ; Hu, Chenguo; Chen, Peng; Wan, Buyong; He, Xiaoshan; Tian, Yongshu; Chongqing Communication College, Chongqing 400035

    2010-07-15

    Mn-doped CeO{sub 2} nanorods have been prepared from CeO{sub 2} particles through a facile composite-hydroxide-mediated (CHM) approach. The analysis from X-ray photoelectron spectroscopy indicates that the manganese doped in CeO{sub 2} exists as Mn{sup 2+}. The magnetic measurement of the Mn-doped CeO{sub 2} nanorods exhibits an enhanced ferromagnetic property at room temperature with a remanence magnetization (Mr) of 1.36 x 10{sup -3} emu/g and coercivity (Hc) of 22 Oe. Comparative UV-visible spectra reveal the shift of the absorption peak of the CeO{sub 2} from ultraviolet region to visible light region after being doped with Mn. The room temperature ferromagnetic properties and light absorption of the Mn-doped CeO{sub 2} nanorods would have potential applications in photocatalysis and building of photovoltaic devices.

  2. The influence of nano-architectured CeOx supports in RhPd/CeO₂ for the catalytic ethanol steam reforming reaction

    SciTech Connect (OSTI)

    Divins, N. J.; Senanayake, S. D.; Casanovas, A.; Xu, W.; Trovarelli, A.; Llorca, J.

    2015-01-19

    The ethanol steam reforming (ESR) reaction has been tested over RhPd supported on polycrystalline ceria in comparison to structured supports composed of nanoshaped CeO₂ cubes and CeO₂ rods tailored towards the production of hydrogen. At 650-700 K the hydrogen yield follows the trend RhPd/CeO₂-cubes > RhPd/CeO₂ -rods > RhPd/CeO₂- polycrystalline, whereas at temperatures higher than 800 K the catalytic performance of all samples is similar and close to the thermodynamic equilibrium. The improved performance of RhPd/CeO₂-cubes and RhPd/CeO₂ -rods for ESR at low temperature is mainly ascribed to higher water-gas shift activity and a strong interaction between the bimetallic - oxide support interaction. STEM analysis shows the existence of RhPd alloyed nanoparticles in all samples, with no apparent relationship between ESR performance and RhPd particle size. X-ray diffraction under operating conditions shows metal reorganization on {100} and {110} ceria crystallographic planes during catalyst activation and ESR, but not on {111} ceria crystallographic planes. The RhPd reconstructing and tuned activation over ceria nanocubes and nanorods is considered the main reason for better catalytic activity with respect to conventional catalysts based on polycrystalline ceria

  3. The influence of nano-architectured CeOx supports in RhPd/CeO₂ for the catalytic ethanol steam reforming reaction

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

    Divins, N. J.; Senanayake, S. D.; Casanovas, A.; Xu, W.; Trovarelli, A.; Llorca, J.

    2015-01-19

    The ethanol steam reforming (ESR) reaction has been tested over RhPd supported on polycrystalline ceria in comparison to structured supports composed of nanoshaped CeO₂ cubes and CeO₂ rods tailored towards the production of hydrogen. At 650-700 K the hydrogen yield follows the trend RhPd/CeO₂-cubes > RhPd/CeO₂ -rods > RhPd/CeO₂- polycrystalline, whereas at temperatures higher than 800 K the catalytic performance of all samples is similar and close to the thermodynamic equilibrium. The improved performance of RhPd/CeO₂-cubes and RhPd/CeO₂ -rods for ESR at low temperature is mainly ascribed to higher water-gas shift activity and a strong interaction between the bimetallic -more » oxide support interaction. STEM analysis shows the existence of RhPd alloyed nanoparticles in all samples, with no apparent relationship between ESR performance and RhPd particle size. X-ray diffraction under operating conditions shows metal reorganization on {100} and {110} ceria crystallographic planes during catalyst activation and ESR, but not on {111} ceria crystallographic planes. The RhPd reconstructing and tuned activation over ceria nanocubes and nanorods is considered the main reason for better catalytic activity with respect to conventional catalysts based on polycrystalline ceria« less

  4. Center for Excitonics (CE) | U.S. DOE Office of Science (SC)

    Office of Science (SC) Website

    Center for Excitonics (CE) Energy Frontier Research Centers (EFRCs) EFRCs Home Centers EFRC External Websites Research Science Highlights News & Events Publications History Contact BES Home Centers Center for Excitonics (CE) Print Text Size: A A A FeedbackShare Page CE Header Director Marc Baldo Lead Institution Massachusetts Institute of Technology Year Established 2009 Mission To supersede traditional electronics with devices that use excitonics to mediate the flow of energy. Research

  5. Capillary electrophoresis-fluorescence line narrowing system (CE-FLNS) for on-line structural characterization

    DOE Patents [OSTI]

    Jankowiak, R.J.; Small, G.J.; Shields, P.A.

    1999-04-27

    Capillary electrophoresis (CE) is interfaced with low temperature fluorescence line-narrowing (FLN) spectroscopy for on-line structural characterization of separated molecular analytes. 21 figs.

  6. Capillary electrophoresis-fluorescence line narrowing system (CE-FLNS) for on-line structural characterization

    DOE Patents [OSTI]

    Jankowiak, Ryszard J.; Small, Gerald J.; Shields, Peter A.

    1999-04-27

    Capillary electrophoresis (CE) is interfaced with low temperature fluorescence line-narrowing (FLN) spectroscopy for on-line structural characterization of separated molecular analytes.

  7. Proactive Design of n-Type (In, Ce) Filled Skutterudites Enabling...

    Broader source: Energy.gov (indexed) [DOE]

    More Documents & Publications Proactive Design of n-Type (In, Ce) Filled Skutterudites Enabling High-Temperature Waste Heat Recovery Thermoelectric Couple Demonstration of (In, ...

  8. Ethanol Steam Reforming on Co/CeO2: The Effect of ZnO Promoter

    SciTech Connect (OSTI)

    Davidson, Stephen; Sun, Junming; Wang, Yong

    2013-12-02

    A series of ZnO promoted Co/CeO2 catalysts were synthesized and characterized using XRD, TEM, H2-TPR, CO chemisorption, O2-TPO, IR-Py, and CO2-TPD. The effects of ZnO on the catalytic performances of Co/CeO2 were studied in ethanol steam reforming. It was found that the addition of ZnO facilitated the oxidation of Co0 via enhanced oxygen mobility of the CeO2 support which decreased the activity of Co/CeO2 in C–C bond cleavage of ethanol. 3 wt% ZnO promoted Co/CeO2 exhibited minimum CO and CH4 selectivity and maximum CO2 selectivity. This resulted from the combined effects of the following factors with increasing ZnO loading: (1) enhanced oxygen mobility of CeO2 facilitated the oxidation of CHx and CO to form CO2; (2) increased ZnO coverage on CeO2 surface reduced the interaction between CHx/CO and Co/CeO2; and (3) suppressed CO adsorption on Co0 reduced CO oxidation rate to form CO2. In addition, the addition of ZnO also modified the surface acidity and basicity of CeO2, which consequently affected the C2–C4 product distributions.

  9. Luminescence properties of LaF{sub 3}:Ce nanoparticles encapsulated by oleic acid

    SciTech Connect (OSTI)

    Kim, Jaewoo; Lee, Jun-Hyung; An, Hyejin; Lee, Jungkuk; Park, Seong-Hee; Seo, Young-Soo; Miller, William H.

    2014-09-15

    Highlights: In-situ hydrophobization of water dispersible LaF{sub 3}:Ce nanoparticles was achieved. Oleic acid surface modification of the nanoparticles was verified by IR spectra. Quantum yields of LaF{sub 3}:Ce and OA-LaF{sub 3}:Ce nanoparticles were evaluated. Quantum yields of LaF{sub 3}:Ce are strongly dependent on OA surface modification. - Abstract: Cerium ions doped lanthanum fluoride (LaF{sub 3}:Ce) nanopowder as well as LaF{sub 3}:Ce nanopowder whose surfaces was modified by oleic acid (OA) were synthesized by using an in-situ hydrothermal process under the various doping concentrations. Based on the XRD spectra and TEM images, it was confirmed that the crystalline structured hexagonal LaF{sub 3}:Ce nanopowder was synthesized. Oleic acid was efficient for conversion of the water dispersible LaF{sub 3}:Ce nanoparticles to hydrophobic ones. Surface modification was verified by FTIR absorption spectrum as well as TEM images, showing no agglomeration between 5 and 10 nm scaled particles. Photoluminescence based on 5d ? 4f electronic transition of cerium ions excited at ?{sub ex} ?256 nm for both neat and OA encapsulated LaF{sub 3}:Ce nanoparticles decreases as the cerium concentration increases, while the quantum yields of OA encapsulated nanoparticles were much lower than the neat particles due to low photon transmittance of OA at the range longer than ?350 nm.

  10. Thermal Variation of Ce Valence in Mixed ValenceKondo Lattice Systems CeT2(Si1-xGex)2 with T= Mn and Ni

    SciTech Connect (OSTI)

    Liang,G.; Croft, M.

    2008-01-01

    The results on the thermal variation of Ce L3-valence in CeT2(Si1-xGex)2 series with 0{le}x{le}1 and T=Mn and Ni are reported. It is observed that for both series, the Ce valence increases with decreasing temperature and has little thermal variation for samples in the nearly trivalent regime. The magnitude of this thermal variation in the T=Mn series is much greater than in the T=Ni series. The results are explained by the degenerate Anderson model and correlated with the specific heat data.

  11. Magnetic structure of the antiferromagnetic Kondo lattice compounds CeRhAl4Si2 and CeIrAl4Si2

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

    Ghimire, N. J.; Calder, S.; Janoschek, M.; Bauer, E. D.

    2015-06-01

    In this article, we have investigated the magnetic ground state of the antiferromagnetic Kondo-lattice compounds CeMAl4Si2(M = Rh, Ir) using neutron powder diffraction. Although both of these compounds show two magnetic transitions TN1 and TN2 in the bulk properties measurements, evidence for magnetic long-range order was only found below the lower transition TN2. Analysis of the diffraction profiles reveals a commensurate antiferromagnetic structure with a propagation vector k = (0, 0, 1/2). The magnetic moment in the ordered state of CeRhAl4Si2 and CeIrAl4Si2 were determined to be 1.14(2) and 1.41(3) μB/Ce, respectively, and are parallel to the crystallographic c-axis inmore » agreement with magnetic susceptibility measurements.« less

  12. Ternary ceramic alloys of Zr-Ce-Hf oxides

    DOE Patents [OSTI]

    Becher, P.F.; Funkenbusch, E.F.

    1990-11-20

    A ternary ceramic alloy is described which produces toughening of zirconia and zirconia composites through the stress transformation from tetragonal phase to monoclinic phase. This alloy, having the general formula Ce[sub x]Hf[sub y]Zr[sub 1[minus]x[minus]y]O[sub 2], is produced through the addition of appropriate amounts of ceria and hafnia to the zirconia. Typically, improved toughness is achieved with about 5 to about 15 mol % ceria and up to about 40 mol % hafnia. The preparation of alloys of these compositions are given together with data as to the densities, tetragonal phase content, hardness and fracture toughness. The alloys are useful in preparing zirconia bodies as well as reinforcing ceramic composites. 1 fig.

  13. Ternary ceramic alloys of ZR-CE-HF oxides

    DOE Patents [OSTI]

    Becher, Paul F.; Funkenbusch, Eric F.

    1990-01-01

    A ternary ceramic alloy which produces toughening of zirconia and zirconia composites through the stress transformation from tetragonal phase to monoclinic phase. This alloy, having the general formula Ce.sub.x Hf.sub.y Zn.sub.1-x-y O.sub.2, is produced through the addition of appropriate amounts of ceria and hafnia to the zirconia. Typically, improved toughness is achieved with about 5 to about 15 mol % ceria and up to about 40 mol % hafnia. The preparation of alloys of these compositions are given together with data as to the densities, tetragonal phase content, hardness and fracture toughness. The alloys are useful in preparing zirconia bodies as well as reinforcing ceramic composites.

  14. Inelastic magnetic neutron scattering in CePd{sub 3}.

    SciTech Connect (OSTI)

    Lawrence, J. M.; Fanelli, V. R.; Goremychkin, E. A.; Osborn, R.; Bauer, E. D.; McClellan, K. J.; Christianson, A. D.; Univ. of California at Irvine; LANL; ORNL

    2008-01-01

    We have performed time-of-flight neutron scattering measurements on a single crystal of the intermediate valence compound CePd{sub 3}. At 10 K, a Kondo-esque inelastic magnetic scattering peak occurs near {Delta}E = 60 meV with maximum intensity for momentum transfer Q near the (1/2, 1/2, 0) zone boundary. Spectral weight is transferred to lower energy as Q varies until at zone center the intensity at 60 meV is considerably weaker. These results are in qualitative accord with predictions of the Anderson lattice. The Q-dependence may resolve an older controversy concerning the low-temperature scattering. We discuss the relationship of these results to our recent results in YbAl{sub 3}.

  15. Preparation and properties of ce-doped TiO{sub 2} photocatalyst

    SciTech Connect (OSTI)

    Yan, Ningning; Zhu, Zhongqi; Zhang, Jin; Zhao, Zongyan; Liu, Qingju

    2012-08-15

    Highlights: ? The cerium ion doped TiO{sub 2} (Ce-TiO{sub 2}) powders were prepared and characterized. ? The spectrum absorption region of Ce-TiO{sub 2} is red-shifted to visible light. ? The recombination of photo-generated electron-hole pairs of Ce-TiO{sub 2} is inhibited. ? The photocatalytic activity was effected by Ce ion content and greatly improved. -- Abstract: TiO{sub 2} nanoparticles doped with different content of Ce ion were prepared by solgel method. The samples were characterized by XRD, XPS, TEM, UVVis, and PL, the photocatalytic activity was evaluated by photocatalytic degradation of methylene blue (MB) under the irradiation of fluorescent lamp. The results indicate that Ce ion is incorporated into the lattice of TiO{sub 2}, which can restrain the increase of grain size, broaden the absorption region to visible light, and inhibit the recombination of the photo-generated electron and hole pairs. Moreover, the photocatalytic activity of Ce-TiO{sub 2} in MB degradation is evidently enhanced. The MB degradation rate of the sample with Ce:Ti = 0.33% (molar ratio) in 8 h is 90.03%, which is much higher than that of P25 (68.19%).

  16. Ethanol Steam Reforming on Co/CeO2: The Effect of ZnO Promoter...

    Office of Scientific and Technical Information (OSTI)

    Ethanol Steam Reforming on CoCeO2: The Effect of ZnO Promoter Citation Details In-Document Search Title: Ethanol Steam Reforming on CoCeO2: The Effect of ZnO Promoter A series of ...

  17. CO Oxidation at the Interface of Au Nanoclusters and the Stepped-CeO2(111) Surface

    SciTech Connect (OSTI)

    Kim H. Y.; Henkelman, G.

    2013-01-14

    To reveal the richer chemistry of CO oxidation by CeO2 supported Au Nanoclusters NCs)/Nanoparticles, we design a Au12 supported on a stepped-CeO2 model (Au/CeO2-step) and study various kinds of CO oxidation mechanisms at the interface of the Au/CeO2-step: oxygen spillover from the CeO2 to the Au NCs;2 CO oxidation by the O2 bound to the Au-Ce3+ interface;3 and CO oxidation by the Mars-van Krevelen (M-vK) mechanism.4 DFT+U calculations show that lattice oxygen at the CeO2 step edge oxidizes CO bound to Au NCs by the M-vK mechanism. CO2 desorption determines the rate of CO oxidation and the vacancy formation energy (Evac) is a reactivity descriptor for CO oxidation. The maximum Evac that insures spontaneous CO2 production is higher for the Au/CeO2-step than the Au/CeO2-surface suggesting that the CeO2-step is a better supporting material than the CeO2-surface for CO oxidation by the Au/CeO2. Our results also suggest that for CO oxidation by Au NCs supported on nano- or meso-structured CeO2, which is the case of industrial catalysts, the M-vK mechanism accounts for a large portion of the total activity.

  18. High Curie temperature of Ce-Fe-Si compounds with ThMn12 structure

    SciTech Connect (OSTI)

    Zhou, C; Pinkerton, FE; Herbst, JF

    2015-01-15

    We report the discovery of ternary CeFe(12-x)Si(x)compounds possessing the ThMn12 structure. The samples were prepared by melt spinning followed by annealing. In contrast to other known Ce Fe-based binary and ternary compounds, CeFe12-xSix compounds exhibit exceptionally high Curie temperatures whose values increase with added Si substitution. The highest T. = 583 K in CeFe10Si2 rivals that of the well-established Nd2Fe14B compound. We ascribe the T-c behavior to a combination of Si-induced 3d band structure changes and partial Ce3+ stabilization. (C) 2014 Published by Elsevier Ltd.

  19. Studies on Ca2+-Doped CeBr3 Scintillating Materials

    SciTech Connect (OSTI)

    Guss, P. [NSTec; Foster, M. E. [SNL; Wong, B. M. [SNL; Doty, F. P. [SNL; Shah, K. [RMD; Squillante, M. [RMD; Glodo, J. [RMD; Yuan, D. [NSTec

    2013-07-03

    Despite the outstanding scintillation performance characteristics of cerium tribromide (CeBr3) and cerium-activated lanthanum tribromide (LaBr3:Ce), their commercial availability and application is limited due to the difficulties of growing large, crack-free single crystals from these fragile materials. The objective of this investigation was to employ aliovalent doping to increase crystal strength while maintaining the optical properties of the crystal. One divalent dopant (Ca2+) was investigated as a dopant to strengthen CeBr3 without negatively impacting scintillation performance. Ingots containing nominal concentrations of 1.9% of the Ca2+ dopant were grown. Preliminary scintillation measurements are presented for this aliovalently doped scintillator. Ca2+-doped CeBr3 exhibited little or no change in the peak fluorescence emission for 371 nm optical excitation for CeBr3. The structural, electronic, and optical properties of CeBr3 crystals were investigated using the density functional theory within generalized gradient approximation. The calculated lattice parameters are in good agreement with the experimental data. The energy band structures and density of states were obtained. The optical properties of CeBr3, including the dielectric function, were calculated.

  20. Processing of transparent polycrystalline AlON:Ce3+ scintillators

    SciTech Connect (OSTI)

    Chen, Ching -Fong; Yang, Pin; King, Graham; Tegtmeier, Eric L.

    2015-10-23

    A new polycrystalline ceramic scintillator is reported for potential use in radiation detection and medical imaging applications. The goal was to develop cerium-activated aluminum oxynitride (AlON:Ce3+) ceramics, which can be produced using ceramic processes in comparison to the high-cost, low-yield single-crystal growth technique. A phase pure AlON:Ce3+ powder with cubic symmetry was successfully synthesized at high temperature under a reducing atmosphere to convert Ce4+ to Ce3+ in the solid solution. We explored two different activator concentrations (0.5 and 1.0 mol%). Fully dense and transparent AlON:Ce3+ ceramics were produced by a liquid-phase-assisted pressureless sintering. The crystal field splitting around the Ce3+ activator in the AlON was comparable to the splitting induced by Br₋ and the Cl₋ ligands, which produced an emission spectrum perfectly matching the maximum quantum efficiency range of the photomultiplier tube for radiation detection. Both optical excitation and radiation ionizations in AlON:Ce3+ were demonstrated. Lastly, challenges and mechanisms related to the radioluminescence efficiency are discussed.

  1. SEMI-ANNUAL REPORTS FOR CE FLNG, LLC (CAMBRIDGE) - DK. NO. 12-123-LNG -

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

    ORDER 3193 | Department of Energy CE FLNG, LLC (CAMBRIDGE) - DK. NO. 12-123-LNG - ORDER 3193 SEMI-ANNUAL REPORTS FOR CE FLNG, LLC (CAMBRIDGE) - DK. NO. 12-123-LNG - ORDER 3193 April 2013 (330.47 KB) October 2013 (475.93 KB) April 2014 (137.83 KB) October 2014 (455.98 KB) April 2015 (566.96 KB) October 2015 (125.7 KB) April 2016 (98.14 KB) More Documents & Publications CE FLNG, LLC - FE DKT. NO. 12-123-LNG - ORDER 3193 EIS-0497: Notice of Intent to Prepare an Environmental Impact

  2. Antiferromagnetic Kondo lattice in the layered compound CePd1-xBi₂ and

    Office of Scientific and Technical Information (OSTI)

    comparison to the superconductor LaPd1-xBi₂ (Journal Article) | SciTech Connect Antiferromagnetic Kondo lattice in the layered compound CePd1-xBi₂ and comparison to the superconductor LaPd1-xBi₂ Citation Details In-Document Search Title: Antiferromagnetic Kondo lattice in the layered compound CePd1-xBi₂ and comparison to the superconductor LaPd1-xBi₂ The layered compound CePd1-xBi₂ with the tetragonal ZrCuSi₂-type structure was obtained from excess Bi flux. Magnetic

  3. Magnitude of the magnetic exchange interaction in the heavy-fermion antiferromagnet CeRhIn?

    SciTech Connect (OSTI)

    Das, Pinaki [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Lin, S. -Z. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Ghimire, N.? J. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Huang, K. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Univ. of California, San Diego, La Jolla, CA (United States); Ronning, F. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Bauer, E.? D. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Thompson, J.? D. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Batista, C.? D. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Ehlers, G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Janoschek, M. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

    2014-12-01

    We have used high-resolution neutron spectroscopy experiments to determine the complete spin wave spectrum of the heavy-fermion antiferromagnet CeRhIn?. The spin wave dispersion can be quantitatively reproduced with a simple frustrated J??J? model that also naturally explains the magnetic spin-spiral ground state of CeRhIn? and yields a dominant in-plane nearest-neighbor magnetic exchange constant J?=0.74(3)??meV. Our results pave the way to a quantitative understanding of the rich low-temperature phase diagram of the prominent CeTIn? (T = Co, Rh, Ir) class of heavy-fermion materials.

  4. Lattice instabilities in heavy fermion superconductors. [CeCu/sub 2/Si/sub 2/; CeAl/sub 3/; CeCu/sub 6/; UBe/sub 13/; UPt/sub 3/

    SciTech Connect (OSTI)

    Wohlleben, D.

    1987-01-01

    This paper shows that while in nonsuperconducting HF systems such as CeCu/sub 6/, CeAl/sub 3/ and stoichiometric CeCu/sub 2/Si/sub 2/, the large electronic ..gamma.. is due to a very narrow f band, in the three HF superconductors UBe/sub 13/, UPt/sub 3/ and nonstochiometric CeCu/sub 2/Si/sub 2/, it is not. The f band of these systems, as measured by their response to magnetic fields in three different ways, is much wider than suggested by the large ..gamma... According to their actual f band width, the HF superconductors belong into the Bantam Fermion class. It is argued that most of the large ..gamma.. of the HF superconductors is not of electronic origin and that it is instead caused by the precursor of a martensitic phase transition of the lattice or by a crystallographic phase mixture, i.e., that it is due to the displacive degrees of freedom. This suggests that the superconductivity of all three HF superconductors is caused by some special, low energy phonons rather than by a narrow f band. 52 refs., 4 figs., 3 tabs.

  5. A comparison of the structure and localized magnetism in Ce{sub 2}PdGa{sub 12} with the heavy fermion CePdGa{sub 6}

    SciTech Connect (OSTI)

    Macaluso, Robin T. [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); Millican, Jasmine N. [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); Nakatsuji, Satoru [Department of Physics, Kyoto University, Kyoto, Japan 606-8502 (Japan); Lee, Han-Oh [Department of Physics, University of California, Davis, CA 95616 (United States); Carter, B. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Moreno, Nelson O. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Fisk, Zachary [Department of Physics, University of California, Davis, CA 95616 (United States); Chan, Julia Y. [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States)]. E-mail: jchan@lsu.edu

    2005-11-15

    Single crystals of Ce{sub 2}PdGa{sub 12} have been synthesized in Ga flux and characterized by X-ray diffraction. This compound crystallizes in the tetragonal P4/nbm space group, Z=2 with lattice parameters of a=6.1040(2)A and c=15.5490(6)A. It shows strongly anisotropic magnetism and orders antiferromagnetically at T{sub N}{approx}11K. A field-induced metamagnetic transition to the ferromagnetic state is observed below T{sub N}. Structure-property relationships with the related heavy-fermion antiferromagnet CePdGa{sub 6} are discussed.

  6. Determination of the Surface Structure of CeO2(111) by Low-Energy...

    Office of Scientific and Technical Information (OSTI)

    Title: Determination of the Surface Structure of CeO2(111) by Low-Energy Electron Diffraction. Abstract not provided. Authors: McCarty, Kevin F. ; Siegel, David A ; El Gabaly ...

  7. ASKO Appliances: Order (2012-CE-19/2004) | Department of Energy

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

    (2012-CE-192004) July 20, 2012 DOE ordered ASKO Appliances, Inc. to pay a 36,500 civil penalty after finding ASKO had failed to certify that certain models of residential...

  8. Acetaldehyde Adsorption and Reaction onCeO2(100) Thin Films

    SciTech Connect (OSTI)

    Mullins, David R; Albrecht, Peter M

    2013-01-01

    This study reports and compares the adsorption and dissociation of acetaldehyde on oxidized and reduced CeOX(100) thin films. Acetaldehyde reacts and decomposes on fully oxidized CeO2(100) whereas it desorbs molecularly at low temperature on CeO2(111). The primary products are CO, CO2 and water along with trace amounts of crotonaldehyde and acetylene. The acetaldehyde adsorbs as the 2-acetaldehyde species, dioxyethylene. Decomposition proceeds by dehydrogenation through acetate and enolate intermediates. The reaction pathway is similar on the reduced CeO2-X(100) surface however the inability to react with surface O on the reduced surface results in H2 rather than H2O desorption and C is left on the surface rather than producing CO and CO2. C-O bond cleavage in the enolate intermediate followed by reaction with surface H results in ethylene desorption.

  9. Chemical stability and Ce doping of LiMgAlF6 neutron scintillator

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

    Du, M. H.

    2014-11-13

    We perform density functional calculations to investigate LiMgAlF6 as a potential neutron scintillator material. The calculations of enthalpy of formation and phase diagram show that single-phase LiMgAlF6 can be grown but it should be more difficult than growing LiCaAlF6 and LiSrAlF6. Moreover, the formation energy calculations for substitutional Ce show that the concentration of Ce on the Al site is negligible but a high concentration (>1 at.%) of Ce on the Mg site is attainable provided that the Fermi level is more than 5 eV lower than the conduction band minimum. Acceptor doping should promote Ce incorporation in LiMgAlF6.

  10. Switching of the Spin-Density-Wave in CeCoIn5 probed by Thermal...

    Office of Scientific and Technical Information (OSTI)

    Switching of the Spin-Density-Wave in CeCoIn5 probed by Thermal Conductivity Citation ... Visit OSTI to utilize additional information resources in energy science and technology. A ...

  11. Switching of the Spin-Density-Wave in CeCoIn5 probed by Thermal...

    Office of Scientific and Technical Information (OSTI)

    Title: Switching of the Spin-Density-Wave in CeCoIn5 probed by Thermal Conductivity Authors: Kim, Duk Young 1 ; Lin, Shizeng 1 ; Weickert, Franziska 2 ; Bauer, Eric Dietzgen ...

  12. Pressure-Induced Structural Phase Transition in CeNi: X-ray and...

    Office of Scientific and Technical Information (OSTI)

    Pressure-Induced Structural Phase Transition in CeNi: X-ray and Neutron Scattering Studies and First-Principles Calculations Citation Details In-Document Search Title: ...

  13. Pressure tuning of competing magnetic interactions in intermetallic CeFe2

    SciTech Connect (OSTI)

    Wang, Jiyang; Feng, Yejun; Jaramillo, R.; van Wezel, Jasper; Canfield, Paul C.; Rosenbaum, T.F.

    2012-07-20

    We use high-pressure magnetic x-ray diffraction and numerical simulation to determine the low-temperature magnetic phase diagram of stoichiometric CeFe2. Near 1.5 GPa we find a transition from ferromagnetism to antiferromagnetism, accompanied by a rhombohedral distortion of the cubic Laves crystal lattice. By comparing pressure and chemical substitution we find that the phase transition is controlled by a shift of magnetic frustration from the Ce-Ce to the Fe-Fe sublattice. Notably the dominant Ce-Fe magnetic interaction, which sets the temperature scale for the onset of long-range order, remains satisfied throughout the phase diagram but does not determine the magnetic ground state. Our results illustrate the complexity of a system with multiple competing magnetic energy scales and lead to a general model for magnetism in cubic Laves phase intermetallic compounds.

  14. NMR studies of field induced magnetism in CeCoIn5 (Journal Article...

    Office of Scientific and Technical Information (OSTI)

    Journal Article: NMR studies of field induced magnetism in CeCoIn5 Citation Details In-Document Search Title: ... Publication Date: 2009-01-01 OSTI Identifier: 972060 Report ...

  15. Magnetic Hardening of CeFe11Ti and the Effect of TiC Addition...

    Office of Scientific and Technical Information (OSTI)

    Magnetic Hardening of CeFe11Ti and the Effect of TiC Addition Citation ... Publication Date: 2015-04-01 OSTI Identifier: 1221660 Report Number(s): IS-J 8423 Journal ID: ISSN ...

  16. Hyperfine field and magnetic structure in the B phase of CeCoIn5...

    Office of Scientific and Technical Information (OSTI)

    We re-analyze Nuclear Magnetic Resonance (NMR) spectra observed at low temperatures and high magnetic fields in the field-induced B-phase of CeCoInsub 5. The NMR spectra are ...

  17. f-electron correlations in nonmagnetic Ce studied by means of...

    Office of Scientific and Technical Information (OSTI)

    f-electron correlations in nonmagnetic Ce studied by means of spin-resolved resonant photoemission Citation Details In-Document Search Title: f-electron correlations in nonmagnetic ...

  18. Ex Parte Communications in Connection with Docket No EERE-2014-BT-CE-0019

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

    Energy Conservation Program: Certification, Compliance, Labeling, and Enforcement for Electric Motors and Small Electric Motors; Proposed Rule | Department of Energy No EERE-2014-BT-CE-0019 Energy Conservation Program: Certification, Compliance, Labeling, and Enforcement for Electric Motors and Small Electric Motors; Proposed Rule Ex Parte Communications in Connection with Docket No EERE-2014-BT-CE-0019 Energy Conservation Program: Certification, Compliance, Labeling, and Enforcement for

  19. Structure and magnetic properties of LnMnSbO ( Ln=La and Ce)

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

    Zhang, Qiang; Kumar, C. M. N.; Tian, Wei; Dennis, Kevin W.; Goldman, Alan I.; Vaknin, David

    2016-03-11

    Here, a neutron powder diffraction (NPD) study of LnMnSbO (Ln = La or Ce) reveals differences between the magnetic ground state of the two compounds due to the strong Ce-Mn coupling compared to La-Mn. The two compounds adopt the P4/nmm space group down to 2 K, and whereas magnetization measurements do not show obvious anomaly at high temperatures, NPD reveals a C-type antiferromagnetic (AFM) order below TN = 255K for LaMnSbO and 240 K for CeMnSbO. While the magnetic structure of LaMnSbO is preserved to base temperature, a sharp transition at TSR = 4.5K is observed in CeMnSbO due tomore » a spin-reorientation (SR) transition of the Mn2+ magnetic moments from pointing along the c axis to the ab plane. The SR transition in CeMnSbO is accompanied by a simultaneous long-range AFM ordering of the Ce moments, which indicates that the Mn SR transition is driven by the Ce-Mn coupling. The ordered moments are found to be somewhat smaller than those expected for Mn2+ (S = 5/2) in insulators, but large enough to suggest that these compounds belong to the class of local-moment antiferromagnets. The lower TN found in these two compounds compared to the As-based counterparts (TN = 317 for LaMnAsO, TN = 347K for CeMnAsO) indicates that the Mn-Pn (Pn=As or Sb) hybridization that mediates the superexchange Mn-Pn-Mn coupling is weaker for the Sb-based compounds.« less

  20. Mitsubishi Electric: Consent Decree (2011-CE-01/0202) | Department of

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

    Energy Mitsubishi Electric: Consent Decree (2011-CE-01/0202) Mitsubishi Electric: Consent Decree (2011-CE-01/0202) May 7, 2010 In this consent degree, the Air-Conditioning, Heating and Refrigeration Institute (AHRI) agrees to pay $5,000 on behalf of Mitsubishi Electric & Electronics, USA, Inc. Mitsubishi Electric agreed that the required certification reports were not filed with DOE; however, Mitsubishi had an agreement with AHRI for AHRI to submit those reports on Mitsubishi's behalf.

  1. Results for aliovalent doping of CeBr{sub 3} with Ca{sup 2+}

    SciTech Connect (OSTI)

    Guss, Paul; Foster, Michael E.; Wong, Bryan M.; Patrick Doty, F.; Shah, Kanai; Squillante, Michael R.; Shirwadkar, Urmila; Hawrami, Rastgo; Tower, Joshua; Yuan, Ding

    2014-01-21

    Despite the outstanding scintillation performance characteristics of cerium tribromide (CeBr{sub 3}) and cerium-activated lanthanum tribromide, their commercial availability and application are limited due to the difficulties of growing large, crack-free single crystals from these fragile materials. This investigation employed aliovalent doping to increase crystal strength while maintaining the optical properties of the crystal. One divalent dopant (Ca{sup 2+}) was used as a dopant to strengthen CeBr{sub 3} without negatively impacting scintillation performance. Ingots containing nominal concentrations of 1.9% of the Ca{sup 2+} dopant were grown, i.e., 1.9% of the CeBr{sub 3} molecules were replaced by CaBr{sub 2} molecules, to match our target replacement of 1 out of 54 cerium atoms be replaced by a calcium atom. Precisely the mixture was composed of 2.26 g of CaBr{sub 2} added to 222.14 g of CeBr{sub 3}. Preliminary scintillation measurements are presented for this aliovalently doped scintillator. Ca{sup 2+}-doped CeBr{sub 3} exhibited little or no change in the peak fluorescence emission for 371?nm optical excitation for CeBr{sub 3}. The structural, electronic, and optical properties of CeBr{sub 3} crystals were studied using the density functional theory within the generalized gradient approximation. Calculated lattice parameters are in agreement with the experimental data. The energy band structures and density of states were obtained. The optical properties of CeBr{sub 3}, including the dielectric function, were calculated.

  2. An Update on Improvements to NiCE Support for RELAP-7

    SciTech Connect (OSTI)

    McCaskey, Alex; Wojtowicz, Anna; Deyton, Jordan H.; Patterson, Taylor C.; Billings, Jay Jay

    2015-01-01

    The Multiphysics Object-Oriented Simulation Environment (MOOSE) is a framework that facilitates the development of applications that rely on finite-element analysis to solve a coupled, nonlinear system of partial differential equations. RELAP-7 represents an update to the venerable RELAP-5 simulator that is built upon this framework and attempts to model the balance-of-plant concerns in a full nuclear plant. This report details the continued support and integration of RELAP-7 and the NEAMS Integrated Computational Environment (NiCE). RELAP-7 is fully supported by the NiCE due to on-going work to tightly integrate NiCE with the MOOSE framework, and subsequently the applications built upon it. NiCE development throughout the first quarter of FY15 has focused on improvements, bug fixes, and feature additions to existing MOOSE-based application support. Specifically, this report will focus on improvements to the NiCE MOOSE Model Builder, the MOOSE application job launcher, and the 3D Nuclear Plant Viewer. This report also includes a comprehensive tutorial that guides RELAP-7 users through the basic NiCE workflow: from input generation and 3D Plant modeling, to massively parallel job launch and post-simulation data visualization.

  3. Antiferromagnetic ordering in the doped Kondo insulator CeRhSb

    SciTech Connect (OSTI)

    Menon, L.; Malik, S.K.

    1997-06-01

    CeRhSb, the so-called {open_quotes}Kondo insulator,{close_quotes} is a mixed-valent compound showing a gap formation in the electronic density of states. On the other hand, CePdSb is ferromagnetically ordered with a Curie temperature of {approximately}17 K. We have carried out magnetic susceptibility and electrical resistivity measurements on CeRh{sub 1{minus}x}Pd{sub x}Sb (0{le}x{le}1.0), to study the ground-state properties of this system. For small Pd doping in CeRhSb, up to 20{percent}, the gap continually diminishes and no magnetic ordering is observed down to 2 K. In the region 0.3{le}x{le}0.4, as soon as the gap is suppressed, an antiferromagnetic ground state is observed. In the region 0.5{le}x{lt}0.7, the compounds are not single phase. At the CePdSb end, in the region 0.7{le}x{le}1, the ground state is ferromagnetic. The observation of an antiferromagnetic phase in the phase diagram of CeRh{sub 1{minus}x}Pd{sub x}Sb, where neither end is antiferromagnetic, is interesting and is discussed in the light of some recent theoretical models. {copyright} {ital 1997} {ital The American Physical Society}

  4. Structure and scintillation yield of Ce-doped AlGa substituted yttrium garnet

    SciTech Connect (OSTI)

    Sidletskiy, Oleg; Kononets, Valerii; Lebbou, Kheirreddine; Neicheva, Svetlana; Voloshina, Olesya; Bondar, Valerii; Baumer, Vyacheslav; Belikov, Konstantin; Gektin, Alexander; Grinyov, Boris; Joubert, Marie-France

    2012-11-15

    Highlights: ? Range of Y{sub 3}(Al{sub 1?x}Ga{sub x}){sub 5}O{sub 12}:Ce solid solution crystals are grown from melt by the Czochralski method. ? Light yield of mixed crystals reaches 130% of the YAG:Ce value at x ? 0.4. ? ?1% of antisite defects is formed in YGG:Ce, but no evidence of this is obtained for the rest of crystals. -- Abstract: Structure and scintillation yield of Y{sub 3}(Al{sub 1?x}Ga{sub x}){sub 5}O{sub 12}:Ce solid solution crystals are studied. Crystals are grown from melt by the Czochralski method. Distribution of host cations in crystal lattice is determined. Quantity of antisite defects in crystals is evaluated using XRD and atomic emission spectroscopy data. Trend of light output at Al/Ga substitution in Y{sub 3}(Al{sub 1?x}Ga{sub x}){sub 5}O{sub 12}:Ce is determined for the first time. Light output in mixed crystals reaches 130% comparative to Ce-doped yttriumaluminum garnet. Luminescence properties at Al/Ga substitution are evaluated.

  5. Luminescence properties and electronic structure of Ce{sup 3+}-doped gadolinium aluminum garnet

    SciTech Connect (OSTI)

    Dotsenko, V.P.; Berezovskaya, I.V.; Voloshinovskii, A.S.; Zadneprovski, B.I.; Efryushina, N.P.

    2015-04-15

    Highlights: • The luminescence properties of Ce{sup 3+} ions in (Y, Gd){sub 3}Al{sub 5}O{sub 12} are analyzed. • The Gd{sup 3+} → Y{sup 3+} substitution leads to increasing of Ce{sup 3+} noncubic crystal field splitting parameter. • The excitation spectra for the Ce{sup 3+} emission in GdAG contain bands at 6.67, 7.75, and 9.76 eV. • These features are due to the Ce{sup 3+}-bound exciton formation and O 2p → Al 3s, 3p transitions. • Contributions from Al atoms to the conduction-band density of states are quite essential. - Abstract: Yttrium-gadolinium aluminum garnets (YGdAG) doped with Ce{sup 3+} ions have been prepared by co-precipitation method. The luminescent properties of Ce{sup 3+} ions in Gd{sub 3(1−x)}Ce{sub 3x}Al{sub 5}O{sub 12} (x = 0.01) have been studied upon excitation in the 2–20 eV region. The substitution of Gd{sup 3+} for Y{sup 3+} in the garnet structure results in broadening the emission band and shifting its maximum towards the longer wavelengths. It was found that in addition to the 4f → 5d excitation bands of Ce{sup 3+} ions, the excitation spectra for the Ce{sup 3+} emission contain bands at 6.67, 7.75, and 9.76 eV. These bands are attributed to the Ce{sup 3+}-bound exciton formation and O 2p → Al 3s, 3p transitions, respectively. Although gadolinium states dominate near the bottom of the conduction band of Gd{sub 3}Al{sub 5}O{sub 12}, contributions from Al{sub tetr} and Al{sub oct} atoms to the conduction-band density of states are evaluated as quite essential.

  6. Cytotoxic and DNA-damaging effects of methyl tert-butyl ether and its metabolites on HL-60 cells in vitro

    SciTech Connect (OSTI)

    Tang, G.H.; Shen, Y.; Shen, H.M.

    1996-12-31

    Methyl tert-butyl ether (MTBE) is a widely used oxygenate in unleaded gasoline; however, few studies have been conducted on the toxicity of this compound. This study evaluates the cytotoxic and DNA-damaging effects of MTBE and its metabolites in a human haemopoietic cell line, HL-60. The metabolites of MTBE studied include tertiary butyl alcohol (TBA), {alpha}-hydroxyisobutyric acid (HIBA), and formaldehyde. Comet assay is used to assess DNA damage, and the cytotoxicity is investigated by lactate dehydrogenease (LDH) release. The results show no significant cytotoxic effects of MTBE, TBA, and HIBA over a concentration ranging from 1 to 30 mM. Formaldehyde, in contrast, causes a substantial LDH release at a concentration of 5 {mu}M. Hydrogen peroxide, a known oxidative agent, at concentrations ranging from 10 to 100 {mu}M, produces a significant dose-related increase in DNA damage, whereas a much higher concentration of MTBE (1 to 30 mM) is required to produce a similar observation. The genotoxic effects of TBA and HIBA appear to be identical to that of MTBE. Conversely, DNA damage is observed for formaldehyde at a relatively low concentration range (5 to 100 {mu}M). These findings suggest that MTBE and its metabolites, except formaldehyde, have relatively low cytotoxic and genotoxic effects. 16 refs., 4 figs.

  7. Structure and Reactivity of Alkyl Ethers Adsorbed on CeO2(111) Model Catalysts

    SciTech Connect (OSTI)

    F Calaza; T Chen; D Mullins; S Overbury

    2011-12-31

    The effect of surface hydroxyls on the adsorption of ether on ceria was explored. Adsorption of dimethyl ether (DME) and diethyl ether (DEE) on oxidized and reduced CeO{sub 2}(111) films was studied and compared with Ru(0001) using RAIRS and sXPS within a UHV environment. On Ru(0001) the ethers adsorb weakly with the molecular plane close to parallel to the surface plane. On the ceria films, the adsorption of the ethers was stronger than on the metal surface, presumably due to stronger interaction of the ether oxygen lone pair electrons with a cerium cation. This interaction causes the ethers to tilt away from the surface plane compared to the Ru(0001) surface. No pronounced differences were found between oxidized (CeO{sub 2}) and reduced (CeOx) films. The adsorption of the ethers was found to be perturbed by the presence of OH groups on hydroxylated CeOx. In the case of DEE, the geometry of adsorption resembles that found on Ru, and in the case of dimethyl ether DME is in between that one found on clean CeOx and the metal surface. Decomposition of the DEE was observed on the OH/CeOx surface following high DEE exposure at 300 K and higher temperatures. Ethoxides and acetates were identified as adsorbed species on the surface by means of RAIRS and ethoxides and formates by s-XPS. No decomposition of dimethyl ether was observed on the OH/CeOx at these higher temperatures, implying that the dissociation of the C-O bond from ethers requires the presence of {beta}-hydrogen.

  8. Structure and Reactivity of Alkyl Ethers Adsorbed on CeO(2)(111) Model Catalysts

    SciTech Connect (OSTI)

    Calaza, Florencia C; Chen, Tsung-Liang; Mullins, David R; Overbury, Steven {Steve} H

    2011-01-01

    The effect of surface hydroxyls on the adsorption of ether on ceria was explored. Adsorption of dimethyl ether (DME) and diethyl ether (DEE) on oxidized and reduced CeO{sub 2}(111) films was studied and compared with Ru(0001) using RAIRS and sXPS within a UHV environment. On Ru(0001) the ethers adsorb weakly with the molecular plane close to parallel to the surface plane. On the ceria films, the adsorption of the ethers was stronger than on the metal surface, presumably due to stronger interaction of the ether oxygen lone pair electrons with a cerium cation. This interaction causes the ethers to tilt away from the surface plane compared to the Ru(0001) surface. No pronounced differences were found between oxidized (CeO{sub 2}) and reduced (CeOx) films. The adsorption of the ethers was found to be perturbed by the presence of OH groups on hydroxylated CeOx. In the case of DEE, the geometry of adsorption resembles that found on Ru, and in the case of dimethyl ether DME is in between that one found on clean CeOx and the metal surface. Decomposition of the DEE was observed on the OH/CeOx surface following high DEE exposure at 300 K and higher temperatures. Ethoxides and acetates were identified as adsorbed species on the surface by means of RAIRS and ethoxides and formates by s-XPS. No decomposition of dimethyl ether was observed on the OH/CeOx at these higher temperatures, implying that the dissociation of the C-O bond from ethers requires the presence of {beta}-hydrogen.

  9. Reduced graphene oxide/CeO{sub 2} nanocomposite with enhanced photocatalytic performance

    SciTech Connect (OSTI)

    Kaur, Jasmeet Anand, Kanika; Singh, Gurpreet; Hastir, Anita; Virpal,; Singh, Ravi Chand; Anand, Kanica

    2015-05-15

    In this work, reduced graphene oxide /cerium oxide (RGO/CeO{sub 2}) nanocomposite was synthesized by in situ reduction of cerium nitrate Ce(NO{sub 3}){sub 3}6H{sub 2}O in the presence of graphene oxide by hydrazine hydrate (N{sub 2}H{sub 4}.H{sub 2}O). The intrinsic characteristics of as-prepared nanocomposite were studied using powder x-ray diffraction (XRD), Raman spectroscopy and field-emission scanning electron microscopy (FESEM). The photocatalytic degradation of methylene blue (MB) was employed as a model reaction to evaluate the photocatalytic activity of the RGO/CeO{sub 2} nanocomposite. The as-obtained RGO/CeO{sub 2} nanocomposite displays a significantly enhanced photocatalytic degradation of MB dye in comparison with bare CeO{sub 2} nanoparticles under sunlight irradiation, which can be attributed to the improved separation of electron-hole pairs and enhanced adsorption performance due to presence of RGO.

  10. Ionic liquid-assisted sonochemical preparation of CeO2 nanoparticles for CO oxidation

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

    Alammar, Tarek; Noei, Heshmat; Wang, Yuemin; Grünert, Wolfgang; Mudring, Anja -Verena

    2014-10-10

    CeO2 nanoparticles were synthesized via a one-step ultrasound synthesis in different kinds of ionic liquids based on bis(trifluoromethanesulfonylamide, [Tf2N]–, in combination with various cations including 1-butyl-3-methylimidazolium ([C4mim]+), 1-ethyl-2,3-dimethylimidazolium ([Edimim]+), butyl-pyridinium([Py4]+), 1-butyl-1-methyl-pyrrolidinium ([Pyrr14]+), and 2-hydroxyethyl-trimethylammonium ([N1112OH]+). Depending on synthetic parameters, such as ionic liquid, Ce(IV) precursor, heating method, and precipitator, formed ceria exhibits different morphologies, varying from nanospheres, nanorods, nanoribbons, and nanoflowers. The morphology, crystallinity, and chemical composition of the obtained materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and N2 adsorption. The structural and electronic propertiesmore » of the as-prepared CeO2 samples were probed by CO adsorption using IR spectroscopy under ultrahigh vacuum conditions. The catalytic activities of CeO2 nanoparticles were investigated in the oxidation of CO. CeO2 nanospheres obtained sonochemically in [C4mim][Tf2N] exhibit the best performance for low-temperature CO oxidation. As a result, the superior catalytic performance of this material can be related to its mesoporous structure, small particle size, large surface area, and high number of surface oxygen vacancy sites.« less

  11. Structural and magnetic phase transitions in CeCu6-xTx (T = Ag,Pd)

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

    Poudel, Lekhanath N.; De la cruz, Clarina; Payzant, E. Andrew; Koehler, Michael R.; May, Andrew F.; Garlea, Vasile O.; Taylor, Alice E.; Parker, David S.; Cao, Huibo B.; McGuire, Michael A.; et al

    2015-12-15

    The structural and the magnetic properties of CeCu6-xAgx (0 ≤ x ≤ 0.85) and CeCu6-xPdx (0 ≤ x ≤ 0.4) have been studied using neutron diffraction, resonant ultrasound spectroscopy (RUS), x-ray diffraction measurements, and first principles calculations. The structural and magnetic phase diagrams of CeCu6-xAgx and CeCu6-xPdx as a function of Ag/Pd composition are reported. The end member, CeCu6, undergoes a structural phase transition from an orthorhombic (Pnma) to a monoclinic (P21/c) phase at 240 K. In CeCu6-xAgx, the structural phase transition temperature (Ts) decreases linearly with Ag concentration and extrapolates to zero at xS ≈ 0.1. The structural transitionmore » in CeCu6-xPdx remains unperturbed with Pd substitution within the range of our study. The lattice constant b slightly decreases with Ag/Pd doping, whereas a and c increase with an overall increase in the unit cell volume. Both systems, CeCu6-xAgx and CeCu6-xPdx, exhibit a magnetic quantum critical point (QCP), at x ≈ 0.2 and x ≈ 0.05, respectively. Near the QCP, long range antiferromagnetic ordering takes place at an incommensurate wave vector (δ1 0 δ2), where δ1 ~ 0.62, δ2 ~ 0.25, x = 0.125 for CeCu6-xPdx and δ1 ~ 0.64, δ2 ~ 0.3, x = 0.3 for CeCu6-xAgx. As a result, the magnetic structure consists of an amplitude modulation of the Ce moments which are aligned along the c axis of the orthorhombic unit cell.« less

  12. Proactive Design of n-Type (In, Ce) Filled Skutterudites Enabling High-Temperature Waste Heat Recovery

    Broader source: Energy.gov [DOE]

    Thermoelectric and structural properties of n-type (In, Ce) filled skutterudites including power factors and ZT as a function of temperature are presented

  13. La-Ce and Sm-Nd systematics of siliceous sedimentary rocks: A clue to marine environment in their deposition

    SciTech Connect (OSTI)

    Hiroshi Shimizu; Masayo Amano; Akimasa Masuda )

    1991-04-01

    La-Ce isotopic data, together with Sm-Nd isotopic data, were determined on siliceous sedimentary rocks (cherts) in order to elucidate the rare earth element (REE) character of their sources and the nature of their depositional environments. The cherts studied are a late Archean chert from the Gorge Creek Group in the Pilbara block of Western Australia, Triassic cherts from central Japan, and Cretaceous and Paleogene deep-sea cherts from the central Pacific and the Caribbean Sea. The Archean chert from the Gorge Creek Group shows chondritic Ce and Nd isotope ratios at its sedimentation age which indicate that its sources had a time-integrated chondritic REE pattern. Triassic cherts from Japan have initial Ce and Nd isotope ratios that show a direct derivation from their continental source. On the other hand, for Cretaceous and Paleogene deep-sea cherts having negative Ce anomalies in their REE patterns, two different sources for Ce and Nd are revealed from their initial Ce and Nd isotope data: Ce from long-term light-REE-depleted oceanic volcanic rocks and Nd from light-REE-enriched continental rocks. The reverse nature observed for deep-sea cherts is considered to be a reflection of their depositional environment far from a continent. These results confirm that the La-Ce isotope system is highly useful in determining the nature and cause of Ce anomalies observed in marine sedimentary rocks such as chert.

  14. Structural and photoluminescence properties of Ce, Dy, Er-doped ZnO nanoparticles

    SciTech Connect (OSTI)

    Jayachandraiah, C.; Kumar, K. Siva; Krishnaiah, G.

    2015-06-24

    Undoped ZnO and rare earth elements (Ce, Dy and Er with 2 at. %) doped nanoparticles were synthesized by wet chemical co-precipitation method at 90°C with Polyvinylpyrrolidone (PVP) as capping agent. The structural, morphological, compositional and photoluminescence studies were performed with X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energy dispersive spectroscopy (EDS), FTIR spectroscopy and Photoluminescence (PL) respectively. XRD results revealed hexagonal wurtzite structure with average particle size around 18 nm - 14 nm and are compatible with TEM results. EDS confirm the incorporation of Ce, Dy and Er elements into the host ZnO matrix and is validated by FTIR analysis. PL studies showed a broad intensive emission peak at 558 nm in all the samples. The intensity for Er- doped ZnO found maximum with additional Er shoulder peaks at 516nm and 538 nm. No Ce, Dy emission centers were found in spectra.

  15. Vortexlike excitations in the heavy-fermion superconductor CeIrIn5

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

    Luo, Yongkang; Rosa, P. F. S.; Bauer, E. D.; Thompson, J. D.

    2016-05-05

    Here, we report a systematic study of temperature- and field-dependent charge (ρ) and entropy (S) transport in the heavy-fermion superconductor CeIrIn5. Its large positive thermopower Sxx is typical of Ce-based Kondo lattice systems, and strong electronic correlations play an important role in enhancing the Nernst signal Sxy. By separating the off-diagonal Peltier coefficient αxy from Sxy, we find that αxy becomes positive and greatly enhanced at temperatures well above the bulk Tc. Compared with the nonmagnetic analog LaIrIn5, these results suggest vortexlike excitations in a precursor state to unconventional superconductivity in CeIrIn5. This study sheds light on the similarity ofmore » heavy-fermion and cuprate superconductors and on the possibility of states not characterized by the amplitude of an order parameter.« less

  16. A Comparative Study of the Water Gas Shift Reaction Over Platinum Catalysts Supported on CeO2, TiO2 and Ce-Modified TiO2

    SciTech Connect (OSTI)

    Gonzalez, I.; Navarro, R; Wen, W; Marinkovic, N; Rodriguez, J; Rosa, F; Fierro, J

    2010-01-01

    WGS reaction has been investigated on catalysts based on platinum supported over CeO{sub 2}, TiO{sub 2} and Ce-modified TiO{sub 2}. XPS and XANES analyses performed on calcined catalysts revealed a close contact between Pt precursors and cerium species on CeO{sub 2} and Ce-modified TiO{sub 2} supports. TPR results corroborate the intimate contact between Pt and cerium entities in the Pt/Ce-TiO{sub 2} catalyst that facilitates the reducibility of the support at low temperatures while the Ce-O-Ti surface interactions established in the Ce-modified TiO{sub 2} support decreases the reduction of TiO{sub 2} at high temperature. The changes in the support reducibility leads to significant differences in the WGS activity of the studied catalysts. Pt supported on Ce-modified TiO{sub 2} support exhibits better activity than those corresponding to individual CeO{sub 2} and TiO{sub 2}-supported catalysts. Additionally, the Ce-TiO{sub 2}-supported catalyst displays better stability at reaction temperatures higher than 573 K that observed on pure TiO{sub 2}-supported counterpart. Activity measurements, when coupled with the physicochemical characterization of catalysts suggest that the modifications in the surface reducibility of the support play an essential role in the enhancement of activity and stability observed when Pt is supported on the Ce-modified TiO{sub 2} substrate.

  17. Structural and spectroscopic properties of pure and doped LiCe(PO{sub 3}){sub 4}

    SciTech Connect (OSTI)

    Abdelhedi, M.; Horchani-Naifer, K.; Dammak, M.; Ferid, M.

    2015-10-15

    Graphical abstract: Emission and excitation and spectra of Eu{sup 3+} doped LiCe(PO{sub 3}){sub 4} host lattice with 1, 2, 3 and 4 mol%. - Highlights: • Europium–doped LiCe(PO{sub 3}){sub 4} were prepared by flux method. • It was analyzed by infrared and Raman spectroscopy, and luminescence spectroscopy. • LiCe(PO{sub 3}){sub 4} doped with Eu{sup 3+} ions as luminophore host materials to produce an intense red. - Abstract: Single crystals of LiCe(PO{sub 3}){sub 4} polyphosphate have been synthesized by the flux method and its structural and luminescence properties have been investigated. This compound crystallizes in the space group C2/c with unit cell dimensions a = 16.52(7) Å, b = 7.09(4) Å, c = 9.83 (4)Å, β = 126.29(4)°, Z = 8 and V = 927.84(3) Å{sup 3}. The obtained polytetraphosphate exhibits very small crystals and the dopant Eu{sup 3+} ions were successfully incorporated into the sites of Ce{sup 3+} ions of the host lattice. The spectroscopy properties confirm the potentiality of present LiCe(PO{sub 3}){sub 4} doped with Eu{sup 3+} ions as luminophore host materials to produce an intense red luminescence at 628 nm corresponding to {sup 5}D{sub 0} → {sup 7}F{sub 2} emission level and have significant importance in the development of emission optical systems.

  18. Magnetic properties of Ce{sup 3+} in Pb{sub 1{minus}x}Ce{sub x}Se: Kondo and crystal-field effect

    SciTech Connect (OSTI)

    Gratens, X.; Charar, S.; Averous, M.; Isber, S.; Deportes, J.; Golacki, Z.

    1997-10-01

    Electron paramagnetic resonance (EPR) experiments were performed on a Pb{sub 1{minus}x}Ce{sub x}Se crystal at liquid-helium temperatures and show very clearly that the doublet {Gamma}{sub 7} is the ground state for cerium ions. The cubic symmetry is shown and the effective Land{acute e} factor for the Ce{sup 3+} is determined to be 1.354{plus_minus}0.003. An orbital reduction factor is introduced to explain the g experimental value. High-field magnetization results are in good agreement with the EPR results. The nominal Ce composition in PbSe deduced from saturation of the magnetization, x=0.0405{plus_minus}0.0003, is very closed to the value determined by microprobe analysis (x=0.04). At 1.5 K, an antiferromagnetic interaction between the nearest-neighbor cerium atoms is found, J{sub ex}/k{sub B}={minus}0.715thinspK. The low-field magnetic-susceptibility results show that the magnetic moment of cerium impurities is strongly temperature dependent, explained by the presence of the crystal-field effect and the Kondo effect. {copyright} {ital 1997} {ital The American Physical Society}

  19. Comparative Study on Redox Properties of Nanosized CeO2 and CuO/Ce2 Under CO/O2

    SciTech Connect (OSTI)

    Martinez-Arias,A.; Gamarra, D.; Fernandez-Garcia, M.; Wang, X.; Hanson, J.; Rodriguez, J.

    2006-01-01

    Nanosized CeO{sub 2} and CuO/CeO{sub 2} samples, active for CO-PROX or related processes were comparatively examined by O{sub 2} probe electron paramagnetic resonance and in situ Raman and X-ray diffraction techniques. Their behavior toward CO reduction, as well as the oxygen-handling properties of the CO-reduced samples, was explored. An appreciable reduction of the ceria bulk was detected on treatment under CO at 473 K. On the basis of the analysis of the evolution of different oxygen-derived species (superoxide, peroxide, O-) on low-temperature (77-300 K) oxygen chemisorption on the CO-reduced samples, a general picture of the redox properties of the samples is presented. Results demonstrate that the presence of copper promotes completion of the redox cycle under CO/O{sub 2} by favoring both ceria reduction and oxidation. This can be relevant to explaining the remarkable oxidation activity and synergetic effects observed for catalysts combining CuO and CeO{sub 2}.

  20. Mechanism of Methane Chemical Looping Combustion with Hematite Promoted with CeO2

    SciTech Connect (OSTI)

    Miller, Duane D.; Siriwardane, Ranjani

    2013-08-01

    Chemical looping combustion (CLC) is a promising technology for fossil fuel combustion that produces sequestration-ready CO{sub 2} stream, reducing the energy penalty of CO{sub 2} separation from flue gases. An effective oxygen carrier for CLC will readily react with the fuel gas and will be reoxidized upon contact with oxygen. This study investigated the development of a CeO{sub 2}-promoted Fe{sub 2}O{sub 3}?hematite oxygen carrier suitable for the methane CLC process. Composition of CeO{sub 2} is between 5 and 25 wt % and is lower than what is generally used for supports in Fe{sub 2}O{sub 3} carrier preparations. The incorporation of CeO{sub 2} to the natural ore hematite strongly modifies the reduction behavior in comparison to that of CeO{sub 2} and hematite alone. Temperature-programmed reaction studies revealed that the addition of even 5 wt % CeO{sub 2} enhances the reaction capacity of the Fe{sub 2}O{sub 3} oxygen carrier by promoting the decomposition and partial oxidation of methane. Fixed-bed reactor data showed that the 5 wt % cerium oxides with 95 wt % iron oxide produce 2 times as much carbon dioxide in comparison to the sum of carbon dioxide produced when the oxides were tested separately. This effect is likely due to the reaction of CeO{sub 2} with methane forming intermediates, which are reactive for extracting oxygen from Fe{sub 2}O{sub 3} at a considerably faster rate than the rate of the direct reaction of Fe{sub 2}O{sub 3} with methane. These studies reveal that 5 wt % CeO{sub 2}/Fe{sub 2}O{sub 3} gives stable conversions over 15 reduction/oxidation cycles. Lab-scale reactor studies (pulsed mode) suggest the methane reacts initially with CeO{sub 2} lattice oxygen to form partial oxidation products (CO + H{sub 2}), which continue to react with oxygen from neighboring Fe{sub 2}O{sub 3}, leading to its complete oxidation to form CO{sub 2}. The reduced cerium oxide promotes the methane decomposition reaction to form C + H{sub 2}, which continue to

  1. Ferromagnetic Kondo lattice CeRuSi{sub 2} with non-Fermi-liquid behavior

    SciTech Connect (OSTI)

    Nikiforov, V. N.; Baran, M.; Irkhin, V. Yu.

    2013-05-15

    The structure, electronic, thermodynamic, and magnetic properties of the CeRuSi{sub 2} Kondo lattice with ferromagnetic ordering characterized by a small moment of the ground state are investigated. Anomalies in the temperature dependences of heat capacity and resistivity (unusual power or logarithmic behavior) observed in the low-temperature range indicate a non-Fermi-liquid behavior. The results are compared with those for other Ce{sub l}Ru{sub n}X{sub m} compounds and anomalous systems based on rare-earth elements and actinides that had been studied earlier.

  2. {ital Ab Initio} Calculation of Crystalline Electric Fields and Kondo Temperatures in Ce Compounds

    SciTech Connect (OSTI)

    Han, J.; Alouani, M.; Cox, D.; Han, J.; Cox, D.; Alouani, M.

    1997-02-01

    We have calculated the band-f hybridizations for Ce{sub x}La{sub 1-x}M{sub 3} compounds (x=1 and x{r_arrow}0; M=Pb,In,Sn,Pd) within the local density approximation and fed this into a noncrossing approximation for the Anderson impurity model applied to both dilute and concentrated limits. Our calculations produce crystalline electric field splittings and Kondo temperatures with trends in good agreement with experiment and demonstrate the need for detailed electronic structure information on hybridization to describe the diverse behaviors of these Ce compounds. {copyright} {ital 1997} {ital The American Physical Society}

  3. (U) Analysis of shock-initiated PBX-9501 through porous CeO2

    SciTech Connect (OSTI)

    Fredenburg, David A.; Dattelbaum, Dana Mcgraw; Dennis-Koller, Darcie

    2015-07-24

    The attenuation properties of an impact initiated PBX-9501 explosive through several thicknesses of CeO2 powder is investigated. The CeO2 is at an initial porous density of 4.0 g/cm3 , roughly 55 % of theoretical maximum density. Measurements of the input (into the powder) and propagated (through the powder) wave profiles are measured using optical velocimetry. Results show a reduction of the average wave speed, CX, and peak steady-state material velocity, uP , with increasing powder thickness from 1.5 - 5.0 mm.

  4. Thermodynamic and Transport Properties of YTe3, LaTe3 and CeTe3

    SciTech Connect (OSTI)

    Ru, N.

    2011-08-19

    Measurements of heat capacity, susceptibility, and electrical resistivity are presented for single crystals of the charge density wave compounds YTe{sub 3}, LaTe{sub 3}, and CeTe{sub 3}. The materials are metallic to low temperatures, but have a small density of states due to the charge density wave gapping large portions of the Fermi surface. CeTe{sub 3} is found to be a weak Kondo lattice, with an antiferromagnetic ground state and T{sub N} = 2.8 K. The electrical resistivity of all three compounds is highly anisotropic, confirming the weak dispersion perpendicular to Te planes predicted by band structure calculations.

  5. Optical properties of the Ce and La ditelluride charge density wave compounds

    SciTech Connect (OSTI)

    Lavagnini, M.; Sacchetti, A.; Degiorgi, L.; Shin, K.Y.; Fisher, I.R.; /Stanford U., Geballe Lab. /Stanford U., Appl. Phys. Dept.

    2010-02-15

    The La and Ce di-tellurides LaTe{sub 2} and CeTe{sub 2} are deep in the charge-density-wave (CDW) ground state even at 300 K. We have collected their electrodynamic response over a broad spectral range from the far infrared up to the ultraviolet. We establish the energy scale of the single particle excitation across the CDW gap. Moreover, we find that the CDW collective state gaps a very large portion of the Fermi surface. Similarly to the related rare earth tri-tellurides, we envisage that interactions and Umklapp processes play a role in the onset of the CDW broken symmetry ground state.

  6. Interplay of structural, optical and magnetic properties in Gd doped CeO{sub 2}

    SciTech Connect (OSTI)

    Soni, S.; Dalela, S.; Kumar, Sudish; Meena, R. S.; Vats, V. S.

    2015-06-24

    In this research wok systematic investigation on the synthesis, characterization, optical and magnetic properties of Ce{sub 1-x}Gd{sub x}O{sub 2} (where x=0.02, 0.04, 0.06, and 0.10) synthesized using the Solid-state method. Structural, Optical and Magnetic properties of the samples were investigated by X-ray diffraction (XRD), UV-VIS-NIR spectroscopy and VSM. Fluorite structure is confirmed from the XRD measurement on Gd doped CeO{sub 2} samples. Magnetic studies showed that the Gd doped polycrystalline samples display room temperature ferromagnetism and the ferromagnetic ordering strengthens with the Gd concentration.

  7. The synthesis and optical property of solid-state-prepared YAG:Ce phosphor by a spray-drying method

    SciTech Connect (OSTI)

    Lee, H.-M.; Cheng, C.-C.; Huang, C.-Y.

    2009-05-06

    Ce{sup 3+}-activated yttrium aluminum garnet (Y{sub 3}Al{sub 5}O{sub 12}:Ce, YAG:Ce) powder as luminescent phosphor was synthesized by the solid-state reaction method. The phase identification, microstructure and photoluminescent properties of the products were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), absorption spectrum and photoluminescence (PL) analysis. Spherical phosphor particle is considered better than irregular-shaped particle to improve PL property and application, so this phosphor was granulated into a sphere-like shape by a spray-drying device. After calcinating at 1500 deg. C for 0, 4, and 8 h, the product was identified as YAG and CeO{sub 2} phases. The CeO{sub 2} phase content is decreased by increasing the calcination time or decreasing the Ce{sup 3+} doping content. The product showed higher emission intensity resulted from more Ce{sup 3+} content and larger grain size. The product with CeO{sub 2} was found to have lower emission intensity. This paper presents the crystal structures of Rietveld refinement results of powder XRD data.

  8. Phase transition and possible metallization in CeVO{sub 4} under pressure

    SciTech Connect (OSTI)

    Garg, Alka B.; Shanavas, K.V.; Wani, B.N.; Sharma, Surinder M.

    2013-07-15

    Phase stability of CeVO{sub 4} under pressure has been investigated using synchrotron based angle dispersive x-ray diffraction (ADXRD), electrical resistance and first principles calculations. The results indicate that the ambient zircon structure of the compound transforms to a low symmetry monoclinic monazite phase beyond 3.8 GPa with nearly 8.6% volume discontinuity. Beyond 11 GPa, the pattern could be fitted to a similar monazite structure which is about 12.7% denser and has a much larger monoclinic beta angle. On pressure release the first monoclinic phase is recovered. The electrical resistance data show a large drop in resistance with pressure indicating substantial narrowing down of the band gap. Electronic structure calculations support these observations and suggest possible pressure induced metallization in this material. - Pressure induced structural phase transition in CeVO{sub 4} as observed by x- ray diffraction (pressure vs. volume) and possible metallization in CeVO{sub 4} through electrical resistance and first principles electronic structure calculations. - Highlights: Structural and electrical behavior of CeVO{sub 4} under pressure studied using x-ray diffraction and electrical resistance measurements and first principles calculations. Two successive structural transitions confirmed by experiment and theory: zirconmonazite Imonazite II. Band gap collapse and possible metallization is indicated by electrical resistance measurements and electronic structure calculations under pressure. Novel observation of lower bulk modulus in the high pressure phase (both by experiment and calculations) explained through structural analysis.

  9. Influence of Electron Doping on Magnetic Order in CeRu2Al10

    SciTech Connect (OSTI)

    Kobayashi, Riki; Kaneko, Koji; Saito, Kotaro; Mignot, Jean-Michel; Andre, Gilles; Robert, Julien; Wakimoto, Shuichi; Matsuda, Masaaki; Chi, Songxue; Haga, Yoshinori; Matsuda, Tatsuma; Yamamoto, Etsuji; Nishioka, Takashi; Tanida, Hiroshi; Sera, Masafumi

    2014-01-01

    The effect of electron doping by the substitution of Rh for Ru on unconventional magnetic order in CeRu2Al10 was investigated via neutron powder diffraction. In Ce(Ru1 xRhx)2Al10 with x = 0.05, 0.12, and 0.2, reorientation of the ordered moment from the c-axis as in pure CeRu2Al10 to the a-axis takes place in all samples, while the ordering vector q 0; 1; 0 remains unchanged within this concentration range. The moment reorientation is accompanied by an increase in its size by a factor of 2.4, from = 0.43 B at x = 0 to = 1.06, 1.04, and 1.02 B for x = 0.05, 0.12, and 0.2, respectively. The continuous decrease in the N el temperature T0(TN), despite an abrupt increase in , underlines the strong anisotropy in the exchange interaction in CeRu2Al10 and the fact that this anisotropy is easily suppressed by electron doping. 1.

  10. CE IGCC Repowering plant sulfuric acid plant. Topical report, June 1993

    SciTech Connect (OSTI)

    Chester, A.M.

    1993-12-01

    A goal of the CE IGCC Repowering project is to demonstrate a hot gas clean-up system (HGCU), for the removal of sulfur from the product gas stream exiting the gasifier island. Combustion Engineering, Inc. (ABB CE) intends to use a HGCU developed by General Electric Environmental Services (GEESI). The original design of this system called for the installation of the HGCU, with a conventional cold gas clean-up system included as a full-load operational back-up. Each of these systems removes sulfur compounds and converts them into an acid off-gas. This report deals with the investigation of equipment to treat this off-gas, recovering these sulfur compounds as elemental sulfur, sulfuric acid or some other form. ABB CE contracted ABB Lummus Crest Inc. (ABB LCI) to perform an engineering evaluation to compare several such process options. This study concluded that the installation of a sulfuric acid plant represented the best option from both a technical and economic point of view. Based on this evaluation, ABB CE specified that a sulfuric acid plant be installed to remove sulfur from off-gas exiling the gas clean-up system. ABB LCI prepared a request for quotation (RFQ) for the construction of a sulfuric acid production plant. Monsanto Enviro-Chem Inc. presented the only proposal, and was eventually selected as the EPC contractor for this system.

  11. Photocatalytic degradation mechanisms of self-assembled rose-flower-like CeO{sub 2} hierarchical nanostructures

    SciTech Connect (OSTI)

    Sabari Arul, N.; Department of Nanoscience and Technology, Bharathiar University, Coimbatore-641 046 ; Mangalaraj, D.; Whan Kim, Tae

    2013-06-03

    Hierarchical rose-flower-like CeO{sub 2} nanostructures were formed by using solvothermal and thermal annealing processes. The CeCO{sub 3}OH thin film was transformed into CeO{sub 2} roses due to thermal annealing. CeO{sub 2} nanostructured roses exhibited excellent photocatalytic activity with a degradation rate of 65% for the azo dye acid orange 7 (AO7) under ultraviolet illumination. The fitting of the absorbance maximum versus time showed that the degradation of AO7 obeyed pseudo-first-order reaction kinetics. The enhancement of the photocatalytic activity for the CeO{sub 2} roses was attributed to the high adsorptivity resulting from the surface active sites and special 4f electron configuration.

  12. Charge dynamics of Ce-based compounds: Connection between the mixed valent and Kondo-insulator states

    SciTech Connect (OSTI)

    Bucher, B. [Laboratorium fuer Festkoerperphysik, Eidgenoessische Technische Hochschule Zuerich, 8093 Zuerich (Switzerland)] [Laboratorium fuer Festkoerperphysik, Eidgenoessische Technische Hochschule Zuerich, 8093 Zuerich (Switzerland); Schlesinger, Z. [IBM, Thomas J. Watson Research Center, Yorktown Heights, New York 10958 (United States)] [IBM, Thomas J. Watson Research Center, Yorktown Heights, New York 10958 (United States); Mandrus, D.; Fisk, Z.; Sarrao, J. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); DiTusa, J.F.; Oglesby, C.; Aeppli, G.; Bucher, E. [AT& T Bell Laboratories, Murray Hill, New Jersey 07974 (United States)] [AT& T Bell Laboratories, Murray Hill, New Jersey 07974 (United States)

    1996-02-01

    The reflectivities of the mixed-valent compounds CeSn{sub 3} and CePd{sub 3} have been measured to obtain the optical conductivity as a function of temperature. Both compounds show a renormalization of the low-energy Drude conductivity at low temperatures. In addition, for the low-carrier-density compound CePd{sub 3}, but not for high-carrier-density CeSn{sub 3}, substantial spectral weight lost from the conductivity below 1000 cm{sup {minus}1} reappears in the frequency range 2000{endash}10000 cm{sup {minus}1}, indicating that CePd{sub 3} can be considered a lightly doped Kondo insulator. {copyright} {ital 1996 The American Physical Society.}

  13. Fundamental Understanding of the Interaction of Acid Gases with CeO2 : From Surface Science to Practical Catalysis

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

    Tumuluri, Uma; Rother, Gernot; Wu, Zili

    2016-03-21

    Acid gases including CO2, SO2, and NOx are ubiquitous in large-scale energy applications including heterogeneous catalysis. The adverse environmental and health effects of these acid gases have resulted in high interest in the research and development of technologies to remove or convert these acid gases. The main challenge for the development of these technologies is to develop catalysts that are highly efficient, stable, and cost-effective, and many catalysts have been reported in this regard. CeO2 and CeO2-based catalysts have gained prominence in the removal and conversion of CO2, SO2, and NOx because of their structural robustness and redox and acid–basemore » properties. In this article, we provide a brief overview of the application of CeO2 and CeO2-based catalysts for the removal of CO2, SO2, and NOx gases with an emphasis on the fundamental understanding of the interactions of these acid gases with CeO2. The studies summarized in this review range from surface science using single crystals and thin films with precise crystallographic planes to practical catalysis applications of nanocrystalline and polycrystalline CeO2 materials with defects and dopants. After an introduction to the properties of CeO2 surfaces, their catalytic properties for conversions of different acid gases are reviewed and discussed. Lastly, we find that the surface atomic structure, oxygen vacancies, and surface acid–base properties of CeO2 play vital roles in the surface chemistry and structure evolution during the interactions of acid gases with CeO2 and CeO2-based catalysts.« less

  14. (U) Equation of State and Compaction Modeling for CeO2

    SciTech Connect (OSTI)

    Fredenburg, David A.; Chisolm, Eric D.

    2014-10-20

    Recent efforts have focused on developing a solid-liquid and three-phase equation of state (EOS) for CeO2, while parallel experimental efforts have focused on obtaining high-fidelity Hugoniot measurements on CeO2 in the porous state. The current work examines the robustness of two CeO2 SESAME equations of state, a solid-liquid EOS, 96170, and a three-phase EOS, 96171, by validating the EOS against a suite of high-pressure shock compression experiments on initially porous CeO2. At lower pressures compaction is considered by incorporating a two-term exponential form of the P-compaction model, using three separate definitions for ?(P). Simulations are executed spanning the partially compacted and fully compacted EOS regimes over the pressure range 0.5 - 109 GPa. Comparison of calculated Hugoniot results with those obtained experimentally indicate good agreement for all definitions of ?(P) with both the solid-liquid and three-phase EOS in the low-pressure compaction regime. At higher pressures the three-phase EOS does a better job at predicting the measured Hugoniot response, though at the highest pressures EOS 96171 predicts a less compliant response than is observed experimentally. Measured material velocity profiles of the shock-wave after it has transmitted through the powder are also compared with those simulated using with solid-liquid and three-phase EOS. Profiles lend insight into limits of the current experimental design, as well as the threshold conditions for the shock-induced phase transition in CeO2.

  15. Synthesis and crystal structure of two new cerium rhodium oxides: Ce{sub 2/3-x}Rh{sup 3+}{sub 2}O{sub 4} (x{approx}0.12) with Ce mixed valency and Ce{sup 4+}Rh{sup 3+}{sub 2}O{sub 5}

    SciTech Connect (OSTI)

    Mizoguchi, Hiroshi; Zakharov, L.N.; Bhuvanesh, N.S.P.; Sleight, A.W.; Subramanian, M.A.

    2011-06-15

    The new compounds Ce{sub 2/3-x}Rh{sub 2}O{sub 4} (x{approx}0.11-0.14) and CeRh{sub 2}O{sub 5} have been prepared. Their structures were determined from single crystal X-ray diffraction data. Electrical and magnetic properties were also evaluated. Based on the structural analysis and physical properties, oxidation states for CeRh{sub 2}O{sub 5} can be assigned as Ce{sup 4+}Rh{sup 3+}{sub 2}O{sub 5}. A small variation in x was detected for Ce{sub 2/3-x}Rh{sub 2}O{sub 4} indicating a formula ranging from Ce{sup 3.64+}{sub 0.55}Rh{sup 3+}{sub 2}O{sub 4} to Ce{sup 3.81+}{sub 0.525}Rh{sup 3+}{sub 2}O{sub 4}. - Graphical abstract: The new compounds Ce{sub 2/3-x}Rh{sub 2}O{sub 4} (x{approx}0.11-0.14) and CeRh{sub 2}O{sub 5} have been prepared and their structures were determined from single crystal X-ray diffraction data. Electrical and magnetic properties were also evaluated. Highlights: > The new compounds CeRh{sub 2}O{sub 5} and Ce{sub 2/3-x}Rh{sub 2}O{sub 4} (x{approx}0.11-0.14) have been prepared. > Their structures were determined from single crystal X-ray diffraction data. > Valence picture is Ce{sup 4+}Rh{sup 3+}{sub 2}O{sub 5} and Ce{sup 3.64+}{sub 0.55}Rh{sup 3+}{sub 2}O{sub 4} to Ce{sup 3.81+}{sub 0.525}Rh{sup 3+}{sub 2}O{sub 4}.

  16. Magnitude of the magnetic exchange interaction in the heavy-fermion antiferromagnet CeRhIn5

    SciTech Connect (OSTI)

    Das, Pinaki; Lin, S. -Z.; Ghimire, N. J.; Huang, K.; Ronning, F.; Bauer, E. D.; Thompson, J. D.; Batista, C. D.; Ehlers, G.; Janoschek, M.

    2014-12-08

    We have used high-resolution neutron spectroscopy experiments to determine the complete spin wave spectrum of the heavy-fermion antiferromagnet CeRhIn?. The spin wave dispersion can be quantitatively reproduced with a simple frustrated J?-J? model that also naturally explains the magnetic spin-spiral ground state of CeRhIn? and yields a dominant in-plane nearest-neighbor magnetic exchange constant J?=0.74(3) meV. Our results lead the way to a quantitative understanding of the rich low-temperature phase diagram of the prominent CeTIn? (T = Co, Rh, Ir) class of heavy-fermion materials.

  17. Magnitude of the magnetic exchange interaction in the heavy-fermion antiferromagnet CeRhIn5

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

    Das, Pinaki; Lin, S. -Z.; Ghimire, N. J.; Huang, K.; Ronning, F.; Bauer, E. D.; Thompson, J. D.; Batista, C. D.; Ehlers, G.; Janoschek, M.

    2014-12-08

    We have used high-resolution neutron spectroscopy experiments to determine the complete spin wave spectrum of the heavy-fermion antiferromagnet CeRhIn₅. The spin wave dispersion can be quantitatively reproduced with a simple frustrated J₁-J₂ model that also naturally explains the magnetic spin-spiral ground state of CeRhIn₅ and yields a dominant in-plane nearest-neighbor magnetic exchange constant J₀=0.74(3) meV. Our results lead the way to a quantitative understanding of the rich low-temperature phase diagram of the prominent CeTIn₅ (T = Co, Rh, Ir) class of heavy-fermion materials.

  18. Reactivity and reaction intermediates for acetic acid adsorbed on CeO2(111)

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

    Calaza, Florencia C.; Chen, Tsung -Liang; Mullins, David R.; Xu, Ye; Steven H. Overbury

    2015-05-02

    Adsorption and reaction of acetic acid on a CeO2(1 1 1) surface was studied by a combination of ultra-highvacuum based methods including temperature desorption spectroscopy (TPD), soft X-ray photoelectronspectroscopy (sXPS), near edge X-ray absorption spectroscopy (NEXAFS) and reflection absorption IRspectroscopy (RAIRS), together with density functional theory (DFT) calculations. TPD shows that thedesorption products are strongly dependent upon the initial oxidation state of the CeO2 surface, includingselectivity between acetone and acetaldehyde products. The combination of sXPS and NEXAFS demon-strate that acetate forms upon adsorption at low temperature and is stable to above 500 K, above whichpoint ketene, acetone and acetic acidmore » desorb. Furthermore, DFT and RAIRS show that below 500 K, bridge bondedacetate coexists with a moiety formed by adsorption of an acetate at an oxygen vacancy, formed bywater desorption.« less

  19. Momentum-resolved photoemission of the Kondo peak in an ordered Ce-containing alloy

    SciTech Connect (OSTI)

    Garnier, M.; Purdie, D.; Breuer, K.; Hengsberger, M.; Baer, Y.

    1997-11-01

    A comparison of uv-photoemission spectra recorded from the surface alloys Pt(111)({radical}(3){times}{radical}(3))R30{degree}Ce and Pt(111)(2{times}2)La allows the contribution from the 4f electrons to be seen easily. The valence-band structure of these two surfaces is very similar, and the most obvious 4f contribution in high-resolution photoemission spectra of the Ce-containing alloy is the tail of the Kondo peak cut at E{sub F}. Within the limits of our measurement, no dispersion of this feature in the occupied regime is detected. The Kondo peak displays a marked intensity dependence on the emission angle, suggesting that hybridization is present in only a limited part of reciprocal space. The temperature dependence of this near-E{sub F} feature supports this interpretation. {copyright} {ital 1997} {ital The American Physical Society}

  20. Single to Multiquasiparticle Excitations in the Itinerant Helical Magnet CeRhIn5

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

    Stock, C.; Rodriguez-Rivera, J. A.; Schmalzl, K.; Rodriguez, E. E.; Stunault, A.; Petrovic, C.

    2015-06-19

    Neutron scattering is used to measure the quantum spin fluctuations in CeRhIn5 - the parent material of the eXIn5 superconducting series. Out-of-plane spin fluctuations are gapped and localized in momentum, similar to the spin excitons in CeCoIn5. The in-plane fluctuations consist of sharp spin-wave excitations parameterized by a nearest neighbor exchange JRKKY =0.88 ± 0.05 meV that crossover to a temporally and spatially broad multiparticle spectrum with energies of ~ 2 × JRKKY . This continuum represents composite fluctuations that illustrate the breakdown of single magnons originating from the delicate energy balance between localized 4f and itinerant behavior in amore » heavy metal. The experiment therefore shows how quasiparticle behavior is changed by the close proximity of quantum criticality.« less

  1. Preparation of new morphological ZnO and Ce-doped ZnO

    SciTech Connect (OSTI)

    Chelouche, A.; Djouadi, D.; Aksas, A.

    2013-12-16

    ZnO micro-tori and cerium doped hexangulars ZnO have been prepared by the sol-gel method under methanol hypercritical conditions of temperature and pressure. X-ray diffraction (XRD) measurement has revealed the high crystalline quality and the nanometric size of the samples. Scanning electron microscopy (SEM) has shown that the ZnO powder has a torus-like shape while that of ZnO:Ce has a hexangular-like shape, either standing free or inserted into the cores of ZnO tori. Transmission electron microscopy (TEM) has revealed that the ZnO particles have sizes between 25 and 30 nm while Ce-doped ZnO grains have diameters ranging from 75 nm to 100 nm. Photoluminescence spectra at room temperature of the samples have revealed that the introduction of cerium in ZnO reduces the emission intensity lines, particularly the ZnO red and green ones.

  2. Single to Multiquasiparticle Excitations in the Itinerant Helical Magnet CeRhIn5

    SciTech Connect (OSTI)

    Stock, C.; Rodriguez-Rivera, J. A.; Schmalzl, K.; Rodriguez, E. E.; Stunault, A.; Petrovic, C.

    2015-06-19

    Neutron scattering is used to measure the quantum spin fluctuations in CeRhIn5 - the parent material of the eXIn5 superconducting series. Out-of-plane spin fluctuations are gapped and localized in momentum, similar to the spin excitons in CeCoIn5. The in-plane fluctuations consist of sharp spin-wave excitations parameterized by a nearest neighbor exchange JRKKY =0.88 ± 0.05 meV that crossover to a temporally and spatially broad multiparticle spectrum with energies of ~ 2 × JRKKY . This continuum represents composite fluctuations that illustrate the breakdown of single magnons originating from the delicate energy balance between localized 4f and itinerant behavior in a heavy metal. The experiment therefore shows how quasiparticle behavior is changed by the close proximity of quantum criticality.

  3. Reactivity and reaction intermediates for acetic acid adsorbed on CeO2(111)

    SciTech Connect (OSTI)

    Calaza, Florencia; Chen, Tsung-Liang; Mullins, David R; Xu, Ye; Overbury, Steven {Steve} H

    2015-01-01

    Adsorption and reaction of acetic acid on a CeO2(1 1 1) surface was studied by a combination of ultra-highvacuum based methods including temperature desorption spectroscopy (TPD), soft X-ray photoelectronspectroscopy (sXPS), near edge X-ray absorption spectroscopy (NEXAFS) and reflection absorption IRspectroscopy (RAIRS), together with density functional theory (DFT) calculations. TPD shows that thedesorption products are strongly dependent upon the initial oxidation state of the CeO2surface, includingselectivity between acetone and acetaldehyde products. The combination of sXPS and NEXAFS demon-strate that acetate forms upon adsorption at low temperature and is stable to above 500 K, above whichpoint ketene, acetone and acetic acid desorb. DFT and RAIRS show that below 500 K, bridge bondedacetate coexists with a moiety formed by adsorption of an acetate at an oxygen vacancy, formed bywater desorption.

  4. DOE 10 CFR Part 429, Docket Number: EERE-2010-BT-CE-0014, RIN

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

    1904-AC23, Federal Register Vol. 76, No. 75, 21813-15 (Tuesday, April 19, 2011), Notice of Proposed Rule for Energy Conservation Program: Certification, Compliance, and Enforcement fo | Department of Energy Part 429, Docket Number: EERE-2010-BT-CE-0014, RIN 1904-AC23, Federal Register Vol. 76, No. 75, 21813-15 (Tuesday, April 19, 2011), Notice of Proposed Rule for Energy Conservation Program: Certification, Compliance, and Enforcement fo DOE 10 CFR Part 429, Docket Number:

  5. Investigation into Nanostructured Lanthanum Halides and CeBr{sub 3} for Nuclear Radiation Detection

    SciTech Connect (OSTI)

    Guss, P., Guise, R., Mukhopadhyay, S., Yuan, D.

    2011-06-22

    This slide-show presents work on radiation detection with nanostructured lanthanum halides and CeBr{sub 3}. The goal is to extend the gamma energy response on both low and high-energy regimes by demonstrating the ability to detect low-energy x-rays and relatively high-energy activation prompt gamma rays simultaneously using the nano-structured lanthanum bromide, lanthanum fluoride, cerium bromide, or other nanocrystal material. Homogeneous and nano structure cases are compared.

  6. Synthesis of Transient Climate Evolution of the last 21-kyr (SynTraCE-21)

    SciTech Connect (OSTI)

    Zhengyu Liu

    2011-05-06

    Climate evolution in the last 21,000 years provides critical observations for testing state-of-the-art climate models on the simulation of climate evolution and abrupt climate changes. Proxy evidences and new modeling activities have led to rapid advances in our understanding of climate change for this past time period. This funding helps to support the first international SynTraCE-21k workshop at Mount Hood, Oregon from 10-13 October, 2010.

  7. Momentum-space structure of quasielastic spin fluctuations in Ce3Pd20Si6

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

    Portnichenko, P. Y.; Cameron, A. S.; Surmach, M. A.; Deen, Pascale P.; Paschen, S.; Prokofiev, A.; Mignot, Jean-Michel; Strydom, A. M.; Telling, Mark T. F.; Podlesnyak, Andrey A.; et al

    2015-01-01

    Surrounded by heavy-fermion metals, Ce3Pd20Si6 is one of the heaviest-electron systems known to date. Here we used high-resolution neutron spectroscopy to observe low-energy magnetic scattering from a single crystal of this compound in the paramagnetic state. We investigated its temperature dependence and distribution in momentum space, which was not accessible in earlier measurements on polycrystalline samples. At low temperatures, a quasielastic magnetic response with a half-width Γ ≈ 0.1 meV persists with varying intensity all over the Brillouin zone. It forms a broad hump centered at the (111) scattering vector, surrounded by minima of intensity at (002), (220), and equivalentmore » wave vectors. The momentum-space structure distinguishes this signal from a simple crystal-field excitation at 0.31 meV, suggested previously, and rather lets us ascribe it to short-range dynamical correlations between the neighboring Ce ions, mediated by the itinerant heavy f electrons via the Ruderman-Kittel-Kasuya-Yosida mechanism. With increasing temperature, the energy width of the signal follows the conventional T1/2 law, Γ(T)=Γ0+A√T. Lastly, the momentum-space symmetry of the quasielastic response suggests that it stems from the simple-cubic Ce sublattice occupying the 8c Wyckoff site, whereas the crystallographically inequivalent 4a site remains magnetically silent in this material.« less

  8. Complex magnetism and strong electronic correlations in Ce2PdGe3

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

    Baumbach, R. E.; Gallagher, A.; Besara, T.; Sun, J.; Siegrist, T.; Singh, D. J.; Thompson, J. D.; Ronning, F.; Bauer, E. D.

    2015-01-05

    Single-crystal x-ray diffraction, magnetic susceptibility, magnetization, heat capacity, and electrical resistivity measurements are reported for the new tetragonal compound Ce2PdGe3, which forms in the space group P42/mmc (No. 131)—a relative of the α₋ThSi2-type structure. Measurements reveal a two-part antiferromagnetic phase transition at TN,1=10.7 K and TN,2=9.6 K and subsequent ferromagnetlike ordering near TC≈2.25 K. The ordered ground state emerges from a lattice of Ce ions that are hybridized with the conduction electrons, as revealed by the enhanced electronic coefficient of the specific heat γ≈50 mJ/mol-Ce-K2 (extrapolated to T=0 for T < TC). Lastly, electronic structure calculations reveal a Fermi surfacemore » that includes sheets with distinct nesting vectors. We find chemical/structural disorder also plays an important role, as evidenced by results from single-crystal x-ray diffraction, the width of the peaks in the heat capacity at TN and TC, and the small residual resistivity ratio RRR=ρ300K/ρ0=1.8.« less

  9. Adsorption and Reaction of C1-C3 Alcohols over CeOx(111) Thin Films

    SciTech Connect (OSTI)

    D Mullins; S Senanayake; T Chen

    2011-12-31

    This study reports the interaction of methanol, ethanol, 1-propanol, and 2-propanol with well-ordered CeO{sub 2}(111) thin film surfaces. All of the alcohols adsorb at low temperature by forming alkoxy and hydroxyl species on the surface. On fully oxidized CeO{sub 2}(111), recombination occurs between some of the alkoxys and hydroxyls, resulting in alcohol desorption near 220 K. At the same temperature, some of the surface hydroxyls disproportionate to produce water and the loss of lattice O. The remaining alkoxys react above 550 K. The primary alcohols favor dehydrogenation products (aldehydes). There is a net loss of O from the system, resulting in a reduction of the ceria. The secondary alcohol, 2-propanol, undergoes primarily dehydration, producing propene with no net change in the cerium oxidation state. Reduced CeO{sub x}(111) competes with the gaseous products for available O. Little or no water is produced. The reaction selectivity for the C{sub 2} and C{sub 3} alcohols shifts toward favoring dehydration products. The loss of O from the alcohols leads to oxidation of the reduced ceria. Compared with the oxidized surface, the alkene desorption shifts to lower temperature, whereas the aldehyde desorption shifts to higher temperature. This indicates that, on the reduced surface, it is easier to break the C-O bond but more difficult to break the O-substrate bond.

  10. Remarkably robust and correlated coherence and antiferromagnetism in (Ce1-x Lax)Cu?Ge?

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

    Hodovanets, H.; Budko, S.? L.; Straszheim, W.? E.; Taufour, V.; Mun, E.? D.; Kim, H.; Flint, R.; Canfield, P.? C.

    2015-06-08

    We present magnetic susceptibility, resistivity, specific heat, and thermoelectric power measurements on (Ce1-x Lax)Cu?Ge? single crystals (0 ? x ? 1). With La substitution, the antiferromagnetic temperature TN is suppressed in an almost linear fashion and moves below 0.36 K, the base temperature of our measurements for x > 0.8. Surprisingly, in addition to robust antiferromagnetism, the system also shows low temperature coherent scattering below Tcoh up to ~ 0.9 of La, indicating a small percolation limit ~ 9% of Ce. Tcoh as a function of magnetic field was found to have different behavior for x more> 0.9. Remarkably, (Tcoh) at H = 0 was found to be linearly proportional to TN. The jump in the magnetic specific heat ?Cm at TN as a function of TK/TN for (Ce1-x Lax)Cu?Ge? follows the theoretical prediction based on the molecular field calculation for the S = 1/2 resonant level model.less

  11. Influence of Electron Doping on Magnetic Order in CeRu2Al10

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

    Kobayashi, Riki; Kaneko, Koji; Saito, Kotaro; Mignot, Jean-Michel; André, Gilles; Robert, Julien; Wakimoto, Shuichi; Matsuda, Masaaki; Chi, Songxue; Haga, Yoshinori; et al

    2014-09-17

    The effect of electron doping by the substitution of Rh for Ru on unconventional magnetic order in CeRu2Al10 was investigated via neutron powder diffraction. In Ce(Ru1-xRhx)2Al10 with x = 0.05, 0.12, and 0.2, reorientation of the ordered moment from the c- to the a-axis takes place in all samples, while the ordering vector q=(0 1 0) remains unchanged within this concentration range. The moment reorientation is accompanied by an enhancement in its size by a factor of ~2.4, from μ=0.43 μB at x=0 to μ =1.06, 1.04, and 1.02 μB for x=0.05, 0.12 and 0.2, respectively. The continuous decrease inmore » N´eel temperature T0(TN), despite an abrupt increase in μ , underlines the strong anisotropy in the exchange interaction in CeRu2Al10, and the fact that this anisotropy is easily suppressed by electron doping.« less

  12. Mesoporous MnCeOx solid solutions for low temperature and selective oxidation of hydrocarbons

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

    Zhang, Pengfei; Lu, Hanfeng; Zhou, Ying; Zhang, Li; Wu, Zili; Yang, Shize; Shi, Hongliang; Zhu, Qiulian; Chen, Yinfei; Dai, Sheng

    2015-10-15

    The development of noble-metal-free heterogeneous catalysts that can realize the aerobic oxidation of C–H bonds at low temperature is a profound challenge in the catalysis community. Here we report the synthesis of a mesoporous Mn0.5Ce0.5Ox solid solution that is highly active for the selective oxidation of hydrocarbons under mild conditions (100–120 °C). Notably, the catalytic performance achieved in the oxidation of cyclohexane to cyclohexanone/cyclohexanol (100 °C, conversion: 17.7%) is superior to those by the state-of-art commercial catalysts (140–160 °C, conversion: 3-5%). Finally, the high activity can be attributed to the formation of a Mn0.5Ce0.5Ox solid solution with an ultrahigh manganesemore » doping concentration in the CeO2 cubic fluorite lattice, leading to maximum active surface oxygens for the activation of C–H bonds and highly reducible Mn4+ ions for the rapid migration of oxygen vacancies from the bulk to the surface.« less

  13. Emission properties and back-bombardment for CeB{sub 6} compared to LaB{sub 6}

    SciTech Connect (OSTI)

    Bakr, Mahmoud; Kawai, M.; Kii, T.; Zen, H.; Masuda, K.; Ohgaki, H.

    2015-02-14

    The emission properties of CeB{sub 6} compared to LaB{sub 6} thermionic cathodes have been measured using an electrostatic DC gun. Obtaining knowledge of the emission properties is the first step in understanding the back-bombardment effect that limits wide usage of thermionic radio-frequency electron guns. The effect of back-bombardment electrons on CeB{sub 6} compared to LaB{sub 6} was studied using a numerical simulation model. The results show that for 6 μs pulse duration with input radio-frequency power of 8 MW, CeB{sub 6} should experience 14% lower temperature increase and 21% lower current density rise compared to LaB{sub 6}. We conclude that CeB{sub 6} has the potential to become the future replacement for LaB{sub 6} thermionic cathodes in radio-frequency electron guns.

  14. Investigation of chemical composition and crystal structure in sintered Ce{sub 15}Nd{sub 15}Fe{sub bal}B{sub 1} magnet

    SciTech Connect (OSTI)

    Huang, Shu-lin; Feng, Hai-bo; Zhu, Ming-gang; Li, An-hua; Li, Wei; Zhang, Yue

    2014-10-15

    The substitution of cerium, a more abundant rare-earth element, for sintered Nd-Fe-B magnets has drawn intense interest. In the present work, nominal composition of Ce{sub 15}Nd{sub 15}Fe{sub bal}B{sub 1} (wt. %), with cerium constitutes increased to 50% of the total rare-earth content, was used. And Ce-free Nd{sub 30}Fe{sub bal}B{sub 1} (wt. %) was prepared by the same preparation process as comparison. The microstructure of the sintered magnets has been investigated by means of X-ray diffraction and transmission electron microscope. The results show that there are three kinds of RE-rich phases in the same magnet, i.e., fcc-(Ce,Nd)O{sub x} (a=0.547nm), hcp-(Ce,Nd){sub 2}O{sub 3} (a=0.386nm, c=0.604nm) and bcc-(Ce,Nd){sub 2}O{sub 3} (a=1.113nm). Ors of (140)(Ce,Nd){sub 2}Fe{sub 14}B// (1-21)bcc-(Ce,Nd){sub 2}O{sub 3}(∼3°), [001](Ce,Nd){sub 2}Fe{sub 14}B// [-214]bcc-(Ce,Nd){sub 2}O{sub 3}; (01-1)(Ce,Nd){sub 2}Fe{sub 14}B// (101)fcc- (Ce,Nd)O{sub x}(∼2°), [101](Ce,Nd){sub 2}Fe14B// [12-1]fcc-(Ce,Nd)O{sub x} were found through selected area electron diffraction (SAED) analysis. According to the analysis, it can be concluded that cerium has partly substituted for neodymium by occupying the corresponding atom sites in the Ce{sub 15}Nd{sub 15}Fe{sub bal}B{sub 1} magnet, without changing the crystal configuration.

  15. Effect of oxygen vacancy on half metallicity in Ni-doped CeO{sub 2} diluted magnetic semiconductor

    SciTech Connect (OSTI)

    Saini, Hardev S. Saini, G. S. S.; Singh, Mukhtiyar; Kashyap, Manish K.

    2015-05-15

    The electronic and magnetic properties of Ni-doped CeO{sub 2} diluted amgentic semiconductor (DMS) including the effect of oxygen vacancy (V{sub o}) with doping concentration, x = 0.125 have been calculated using FPLAPW method based on Density Functional Theory (DFT) as implemented in WIEN2k. In the present supercell approach, the XC potential was constructed using GGA+U formalism in which Coulomb correction is applied to standard GGA functional within the parameterization of Perdew-Burke-Ernzerhof (PBE). We have found that the ground state properties of bulk CeO{sub 2} compound have been modified significantly due to the substitution of Ni-dopant at the cation (Ce) site with/without V{sub O} and realized that the ferromagnetism in CeO{sub 2} remarkably depends on the V{sub o} concentrations. The presence of V{sub o}, in Ni-doped CeO{sub 2}, can leads to strong ferromagnetic coupling between the nearest neighboring Ni-ions and induces a HMF in this compound. Such ferromagnetic exchange coupling is mainly attributed to spin splitting of Ni-d states, via electrons trapped in V{sub o}. The HMF characteristics of Ni-doped CeO{sub 2} including V{sub o} makes it an ideal material for spintronic devices.

  16. Kondo behavior, ferromagnetic correlations, and crystal fields in the heavy Fermion compounds Ce3X (X=In, Sn)

    SciTech Connect (OSTI)

    Wang, C. H.; Lawrence, J. M.; Christianson, Andrew D; Goremychkin, E. A.; Fanelli, V. R.; Gofryk, K.; Bauer, E. D.; Ronning, F.; Thompson, J. D.; De Souza, N. R.; Kolesnikov, Alexander I

    2010-01-01

    We report measuerments of the inelastic neutron scattering, the magnetic susceptibility, the magnetization, and the magnetic field dependence of the specific heat for the heavy Fermion compounds Ce3In and Ce3Sn. The neutron scattering results show that the excited crystal field levels have energies E1=13.2 meV, E2-44.8 meV for Ce3In and E1=18.5 meV, E2=36.1 meV for Ce3Sn. The Kondo temperature deduced from the quasielastic linewidth is 17 K for Ce3In and 40 K for Ce3Sn. The low temperature behavior of teh specific heat, magnetization, and susceptibility can not be well-described by J=1.2 Kondo physics alone, but require calculations that include contributions from the Kondo effect, broadened crystal fields, and ferromagnetic correlations, all of which are known to be important in these compounds. We find that the ferromagnetic fluctuation makes a 10-15% contribution to the ground state entropy and magnetization. The large in this heavy Fermion system thus arises more from the ferromagnetic correlations than from the Kondo behavior.

  17. Soft chemistry synthesis of high-crystalline orthogermanate CeGeO{sub 4}: A new photocatalyst

    SciTech Connect (OSTI)

    Xing Jun; Yang Chen; Li Weikun; Gong Xueqing; Yang Huagui

    2013-01-15

    A new orthogermanate phase of CeGeO{sub 4} was studied and the corresponding nanocrystals have been successfully synthesized via a facile hydrothermal method without adding any capping agent. The pH value of the solution and the reaction time were also further investigated, respectively. The as-prepared CeGeO{sub 4} nanocrystals with a uniform size of 15 nm have been characterized by using XRD/TEM/TGA/UV-vis techniques, and their electronic structures and band gap were calculated based on a plane wave density function theory (DFT). The promising photocatalytic properties of CeGeO{sub 4} have been confirmed through monitoring reactive oxidative species generated in photocatalytic reactions of terephthalic acid as a fluorescence probe. - Graphical Abstract: A novel photocatalyst CeGeO{sub 4} was prepared. Highlights: Black-Right-Pointing-Pointer CeGeO{sub 4} as a novel photocatalyst was successfully synthesized by a hydrothermal method. Black-Right-Pointing-Pointer Electronic structure and band gap were calculated based on DFT. Black-Right-Pointing-Pointer CeGeO{sub 4} exhibited a promising photocatalytic performance.

  18. High thermoelectric performance of In, Yb, Ce multiple filled CoSb{sub 3} based skutterudite compounds

    SciTech Connect (OSTI)

    Ballikaya, Sedat; Department of Physics, University of Michigan, Ann Arbor, MI, 48109 ; Uzar, Neslihan; Yildirim, Saffettin; Salvador, James R.; Uher, Ctirad

    2012-09-15

    Filling voids with rare earth atoms is an effective way to lowering thermal conductivity which necessarily enhances thermoelectric properties of skutterudite compounds. Yb atom is one of the most effective species among the rare earth atoms for filling the voids in the skutterudite structure due to a large atomic mass, radius and it is intermediate valence state. In this work, we aim to find the best filling partners for Yb using different combinations of Ce and In as well as to optimize actual filling fraction in order to achieve high values of ZT. The traditional method of synthesis relying on melting-annealing and followed by spark plasma sintering was used to prepare all samples. The thermoelectric properties of four samples of Yb{sub 0.2}In{sub 0.2}Co{sub 4}Sb{sub 12}, Yb{sub 0.2}Ce{sub 0.15}Co{sub 4}Sb{sub 12}, Yb{sub 0.2}Ce{sub 0.15}In{sub 0.2}Co{sub 4}Sb{sub 12}, and Yb{sub 0.3}Ce{sub 0.15}In{sub 0.2}Co{sub 4}Sb{sub 12} (nominal) were examined based on the Seebeck coefficient, electrical conductivity, thermal conductivity, and Hall coefficient. Hall coefficient and Seebeck coefficient signs confirm that all samples are n-type skutterudite compounds. Carrier density increases with the increasing Yb+Ce content. A high power factor value of 57.7 {mu}W/K{sup 2}/cm for Yb{sub 0.2}Ce{sub 0.15}Co{sub 4}Sb{sub 12} and a lower thermal conductivity value of 2.82 W/m/K for Yb{sub 0.2}Ce{sub 0.15}In{sub 0.2}Co{sub 4}Sb{sub 12} indicate that small quantities of Ce with In may be a good partner to Yb to reduce the thermal conductivity further and thus enhance the thermoelectric performance of skutterudites. The highest ZT value of 1.43 was achieved for Yb{sub 0.2}Ce{sub 0.15}In{sub 0.2}Co{sub 4}Sb{sub 12} triple-filled skutterudite at 800 K. - Graphical abstract: Thermoelectric figure of merit of Yb{sub x}In{sub y}Ce{sub z}Co{sub 4}Sb{sub 12} (0{<=}x,y,z{<=}0.18 actual) compounds versus temperature. Highlights: Black-Right-Pointing-Pointer TE properties of Yb,In,Ce

  19. Lattice, Ce-L{sub 3}valence, transport, and magnetic results on mixed-valent/Kondo system Ce{sub 1{minus}x}La{sub x}Mn{sub 2}Si{sub 2}

    SciTech Connect (OSTI)

    Liang, G.; Xi, H.; Roberts, E.; Binford, T.; Mochizuki, K.; Markert, J.T.; Croft, M.

    1997-04-01

    Lattice, Ce-L{sub 3} edge, resistivity, and magnetic susceptibility measurements have been carried out on the polycrystalline Ce{sub 1{minus}x}La{sub x}Mn{sub 2}Si{sub 2} system (0{le}x{le}1) to study the interplay between Mn 3d-host magnetism and Kondo-type Ce-spin fluctuations. As x increases, the system varies gradually from a Ce mixed-valent system with 3d-host antiferromagnetism (at x=0) to a nearly trivalent system with strong 3d-host ferromagnetism (near x=1). In the antiferromagnetic (AF) phase region (0{le}x{le}0.5), the Neel temperature T{sub N} decreases with the increase of x, manifesting the weakening of the host AF field. Impurity Kondo behavior is observed at x=0.05, indicating that the low-temperature coherence state in CeMn{sub 2}Si{sub 2} can be destroyed by {open_quotes}Kondo holes{close_quotes} which are created by very small substitution of La for Ce. The susceptibility and resistivity results suggest that the impurity Kondo effect in the 0.1{le}x{le}0.5 samples is partially suppressed by a nonvanishing ferromagnetic (FM) field component; whereas the phononlike behavior of the resistivity curves in the Mn-host FM-phase region (0.5{lt}x{le}1.0) supports our previous proposal that the Kondo-type Ce-spin fluctuations can be effectively quenched by a strong 3d-host FM field. {copyright} {ital 1997 American Institute of Physics.}

  20. Optical properties of {gamma}- and {alpha}-Ce by spectroscopic ellipsometry

    SciTech Connect (OSTI)

    Joo Yull, Rhee

    1992-07-20

    A rotating analyzer type ellipsometer with an ultra high vacuum sample chamber was built. The dielectric functions of {gamma}- and {alpha}-Ce were measured in the energy range from 1.5 to 5.4 eV to investigate the role of the 4f electron in the isostructural phase transition. {gamma}- and {alpha}-Ce were made by evaporation of Ce on sapphire substrates at room temperature and 25 K. All measurements were performed inside a UHV chamber at pressures lower than l {times} 10{sup {minus}10}Torr. The measured dielectric functions showed a thickness dependence. The thicker sample has the smaller optical conductivities. Both overlayer thickness and void fraction increase as sample thickness increases. Repeating cooling-heating-cooling or heating-cooling-heating cycles causes the sample surface to become rougher but the relative volume fractions of both phases and the void fraction in the bulk remain unchanged. The optical conductivity increases upon entering the a-phase but the number of electrons per atom, N{sub eff}/N{sub A}, contributing to the optical conductivity does not change. The valence electrons lose oscillator strength in the above energy range due to volume collapse. This reduces N{sub eff}/NA but the increased 4f-sd valence band hybridization exactly compensates the reduced oscillator strength. Therefore the net effects of the {gamma}{yields}{alpha} isostructural phase transition are an increase of optical conductivity and constancy of N{sub eff}/N{sub A}.

  1. Kondo-lattice behavior and multiple characteristic temperatures in CeIr{sub 2}Ge{sub 2}

    SciTech Connect (OSTI)

    Mallik, R.; Sampathkumaran, E.V.; Paulose, P.L.; Dumschat, J.; Wortmann, G.

    1997-02-01

    The results of electrical-resistivity {rho} measurements (1.4{endash}300 K) on the alloys, Ce{sub 1{minus}x}La{sub x}Ir{sub 2}Ge{sub 2} (0{le}x{le}1), CeIr{sub 2{minus}x}(Rh,Pt){sub x}Ge{sub 2} (x=0.2 and 0.4), and CeIr{sub 2}Ge{sub 2{minus}x}(Si,Sn){sub x} (x=0.2 and 0.4), are reported in order to understand the Kondo effect in CeIr{sub 2}Ge{sub 2}. There is a significant decrease in {rho} as the temperature is lowered from 100 to 4.2 K for x = 0.0. This feature disappears for a small replacement of Ce by La (x = 0.3), thereby resulting in a single-ion Kondo effect for higher values of x. This finding establishes that the temperature T{sub coh}, characterizing the coherent scattering among the Kondo centers for x=0 is as large as about 100 K. The coherent scattering is not destroyed by small substitutions at the Ir or Ge site. The observed sensitivity of this coherence effect to a small disruption of Ce sublattice periodicity alone by La substitution is uncommon among trivalent Ce alloys. Such a large T{sub coh} value enables us to emphasize the need to invoke three characteristic temperatures for nonmagnetic Kondo lattices. {copyright} {ital 1997} {ital The American Physical Society}

  2. Surface-structure sensitivity of CeO2 nanocrystals in photocatalysis and enhancing the reactivity with nanogold

    SciTech Connect (OSTI)

    Lei, Wanying; Zhang, Tingting; Gu, Lin; Liu, Ping; Rodriguez, José A.; Liu, Gang; Liu, Minghua

    2015-06-19

    Structure–function correlations are a central theme in heterogeneous (photo)catalysis. In this research, using aberration-corrected scanning transmission electron microscopy (STEM), the atomic surface structures of well-defined one-dimensional (1D) CeO2 nanorods (NRs) and 3D nanocubes (NCs) are directly visualized at subangstrom resolution. CeO2 NCs predominantly expose the {100} facet, with {110} and {111} as minor cutoff facets at the respective edges and corners. Notably, the outermost surface layer of the {100} facet is nearly O-terminated. Neither surface relaxations nor reconstructions on {100} are observed, indicating unusual polarity compensation, which is primarily mediated by near-surface oxygen vacancies. The surface of CeO2 NRs is highly stepped, with the enclosed {110} facet exposing Ce cations and O anions on terraces. On the basis of STEM profile-view imaging and electronic structure analysis, the photoreactivity of CeO2 nanocrystals toward aqueous methyl orange degradation under UV is revealed to be surface-structure-sensitive, following the order: {110} >> {100}. The underlying surface-structure sensitivity can be attributed to the variation in low-coordinate surface cerium cations between {110} and {100} facets. To further enhance light absorption, Au nanoparticles (NPs) are deposited on CeO2 NRs to form Au/CeO2 plasmonic nanocomposites, which dramatically promotes the photoreactivity that is Au particle size- and excitation light wavelength-dependent. The mechanisms responsible for the enhancement of photocatalytic activity are discussed, highlighting the crucial role of photoexcited charge carrier transfer.

  3. Surface-structure sensitivity of CeO2 nanocrystals in photocatalysis and enhancing the reactivity with nanogold

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

    Lei, Wanying; Zhang, Tingting; Gu, Lin; Liu, Ping; Rodriguez, José A.; Liu, Gang; Liu, Minghua

    2015-06-19

    Structure–function correlations are a central theme in heterogeneous (photo)catalysis. In this research, using aberration-corrected scanning transmission electron microscopy (STEM), the atomic surface structures of well-defined one-dimensional (1D) CeO2 nanorods (NRs) and 3D nanocubes (NCs) are directly visualized at subangstrom resolution. CeO2 NCs predominantly expose the {100} facet, with {110} and {111} as minor cutoff facets at the respective edges and corners. Notably, the outermost surface layer of the {100} facet is nearly O-terminated. Neither surface relaxations nor reconstructions on {100} are observed, indicating unusual polarity compensation, which is primarily mediated by near-surface oxygen vacancies. The surface of CeO2 NRs ismore » highly stepped, with the enclosed {110} facet exposing Ce cations and O anions on terraces. On the basis of STEM profile-view imaging and electronic structure analysis, the photoreactivity of CeO2 nanocrystals toward aqueous methyl orange degradation under UV is revealed to be surface-structure-sensitive, following the order: {110} >> {100}. The underlying surface-structure sensitivity can be attributed to the variation in low-coordinate surface cerium cations between {110} and {100} facets. To further enhance light absorption, Au nanoparticles (NPs) are deposited on CeO2 NRs to form Au/CeO2 plasmonic nanocomposites, which dramatically promotes the photoreactivity that is Au particle size- and excitation light wavelength-dependent. The mechanisms responsible for the enhancement of photocatalytic activity are discussed, highlighting the crucial role of photoexcited charge carrier transfer.« less

  4. Structure and magnetic properties of Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15}, a new 10H-polytype in the Ba-Ce-Mn-O system

    SciTech Connect (OSTI)

    Macias, Mario A.; Mentre, Olivier; Cuello, Gabriel J.; Gauthier, Gilles H.

    2013-02-15

    Based on the peculiar magnetic properties that are observed in pseudo one-dimensional manganites, we decided to synthesize the new Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15} compound. The preparation was performed by solid state reaction in air at about 1350 Degree-Sign C, for which we found that the compound crystallizes in a hexagonal symmetry with space group P6{sub 3}/mmc (No-194) and cell parameters a=b=5.7861(2) A and c=23.902(1) A. The structural description was correlated with neutron diffraction and bond valence calculations, confirming the presence of Ce{sup 4+} and Mn{sup 4+} segregated in the different crystallographic positions. Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15} displays evidence for strong AFM couplings already set at room temperature. The main arrangement of Mn{sup 4+} in magnetically isolated tetramers of face-sharing octahedra is responsible for a metamagnetic-like transition around 50 K. - Graphical abstract: The new Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15} polytype shows strong AFM couplings in magnetically isolated [Ce{sub 0.25}Mn{sub 3.75}O{sub 15}] tetramers of face-sharing octahedral, resulting in a metamagnetic-like transition around 50 K. Highlights: Black-Right-Pointing-Pointer Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15}, a new 10H polytype, has been prepared in the Ba-Ce-Mn-O system. Black-Right-Pointing-Pointer The compound crystallizes in the P6{sub 3}/mmc space group with (cchhh){sub 2} stacking sequence. Black-Right-Pointing-Pointer [Ce{sub 0.25}Mn{sub 3.75}O{sub 15}] tetramers are separated by [CeO{sub 6}] octahedra in the structure. Black-Right-Pointing-Pointer Instead of robust AFM ordering, a metamagnetic-like transition is found around 50 K.

  5. Analysis of FEL-based CeC amplification at high gain limit

    SciTech Connect (OSTI)

    Wang, G.; Litvinenko, V.; Jing, Y.

    2015-05-03

    An analysis of Coherent electron Cooling (CeC) amplifier based on 1D Free Electron Laser (FEL) theory was previously performed with exact solution of the dispersion relation, assuming electrons having Lorentzian energy distribution. At high gain limit, the asymptotic behavior of the FEL amplifier can be better understood by Taylor expanding the exact solution of the dispersion relation with respect to the detuning parameter. In this work, we make quadratic expansion of the dispersion relation for Lorentzian energy distribution and investigate how longitudinal space charge and electrons’ energy spread affect the FEL amplification process.

  6. Disorder and size effects on Kondo interactions and magneticcorrelations in CePt2 nanoscrystals

    SciTech Connect (OSTI)

    Chen, Y.Y.; Huang, P.H.; Ou, M.N.; Wang, C.R.; Yao, Y.D.; Lee,T.K.; Ho, M.Y.; Lawrence, J.M.; Booth, C.H.

    2006-12-12

    The evolution of the Kondo effect and magnetic correlations with size reduction in CePt{sub 2} nanoparticles (3.1-26 nm) is studied by analysis of the temperature-dependent specific heat and magnetic susceptibility. The antiferromagnetic correlations diminish with size reduction. The Kondo effect predominates at small particle size with trivalent, small Kondo temperature (T{sub K}) magnetic regions coexisting with strongly mixed valent, large T{sub K} nonmagnetic regions. We discuss the role of structural disorder, background density of states and the electronic quantum size effect on the results.

  7. Nanostructured LaF{sub 3}:Ce Quantum Dot Nuclear Radiation Detector

    SciTech Connect (OSTI)

    Guss, P., Guise, R., Reed, M., Mukhopadhyay, S., Yuan, D.

    2010-11-01

    Many radioactive isotopes have low energy X-rays and high energy gamma rays of interest for detection. The goal of the work presented was to demonstrate the possibility of measuring both low-energy X-rays and relatively high-energy gamma rays simultaneously using the nano-structured lanthanum bromide, lanthanum fluoride, or cerium bromide. The key accomplishments of the project was the building and acquisition of the LaF3:Ce nanocomposite detectors. Nanocomposite detectors are sensitive to {gamma}s as well as ns and X-rays.

  8. High-pressure, transport, and thermodynamic properties of CeTe3

    SciTech Connect (OSTI)

    Zocco, D.A.

    2010-02-24

    We have performed high-pressure, electrical resistivity, and specific heat measurements on CeTe3 single crystals. Two magnetic phases with nonparallel magnetic easy axes were detected in electrical resistivity and specific heat at low temperatures. We also observed the emergence of an additional phase at high pressures and low temperatures and a possible structural phase transition detected at room temperature and at 45 kbar, which can possibly be related with the lowering of the charge-density wave transition temperature known for this compound.

  9. DOE 10 CFR Parts 430 and 431, Docket No. EERE-2010-BT-CE-0014 RIN

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

    1904-AC23, Federal Register Vol. 75, No. 88, 25121-24 (Friday, May 7, 2010), Revisions to Energy Efficiency Enforcement Regulations, Request for Information (RFI);request for comm | Department of Energy Parts 430 and 431, Docket No. EERE-2010-BT-CE-0014 RIN 1904-AC23, Federal Register Vol. 75, No. 88, 25121-24 (Friday, May 7, 2010), Revisions to Energy Efficiency Enforcement Regulations, Request for Information (RFI);request for comm DOE 10 CFR Parts 430 and 431, Docket No.

  10. Pulse studies to decipher the role of surface morphology in CuO/CeO₂ nanocatalysts for the water gas shift reaction

    SciTech Connect (OSTI)

    Rodriguez, Jose A.; Zhao, Fuzhen; Liu, Zongyuan; Xu, Wenqian; Yao, Siyu; Si, Rui; Johnston-Peck, Aaron C.; Martinez-Arias, Arturo; Hanson, Jonathan C.; Senanayake, Sanjaya D.

    2015-01-23

    The water-gas shift reaction (WGS, CO + H₂O → CO₂) was studied over CuO/CeO₂ catalysts with two different ceria particle morphohologies, in the form of nanospheres (ns) and nanocubes (nc). To understand the strong dependence of the WGS reaction activity on the ceria nanoshapes, pulses of CO (without and with water vapor) were employed during in situ X-ray diffraction (XRD) and X-ray absoprtion near edge structure (XANES) measurements done to characterize the catalysts. The results showed that CuO/CeO₂ (ns) exhibited a substantially better activity than CuO/CeO₂ (nc). The higher activity was associated with the unique properties of CuO/CeO₂ (ns), such as the easier reduction of highly dispersed CuO to metallic Cu, the stability of metallic Cu and a larger concentration Ce³⁺ in CeO₂ (ns).

  11. Pulse studies to decipher the role of surface morphology in CuO/CeO₂ nanocatalysts for the water gas shift reaction

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

    Rodriguez, Jose A.; Zhao, Fuzhen; Liu, Zongyuan; Xu, Wenqian; Yao, Siyu; Si, Rui; Johnston-Peck, Aaron C.; Martinez-Arias, Arturo; Hanson, Jonathan C.; Senanayake, Sanjaya D.

    2015-01-23

    The water-gas shift reaction (WGS, CO + H₂O → CO₂) was studied over CuO/CeO₂ catalysts with two different ceria particle morphohologies, in the form of nanospheres (ns) and nanocubes (nc). To understand the strong dependence of the WGS reaction activity on the ceria nanoshapes, pulses of CO (without and with water vapor) were employed during in situ X-ray diffraction (XRD) and X-ray absoprtion near edge structure (XANES) measurements done to characterize the catalysts. The results showed that CuO/CeO₂ (ns) exhibited a substantially better activity than CuO/CeO₂ (nc). The higher activity was associated with the unique properties of CuO/CeO₂ (ns), suchmore » as the easier reduction of highly dispersed CuO to metallic Cu, the stability of metallic Cu and a larger concentration Ce³⁺ in CeO₂ (ns).« less

  12. Weak hybridization and isolated localized magnetic moments in the compounds CeT2Cd20 (T = Ni, Pd)

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

    White, B. D.; Yazici, D.; Ho, P. -C.; Kanchanavatee, N.; Pouse, N.; Fang, Y.; Breindel, A. J.; Friedman, A. J.; Maple, M. B.

    2015-07-20

    Here, we report the physical properties of single crystals of the compounds CeT2Cd20 (T = Ni, Pd) that were grown in a molten Cd flux. Large separations of ~6.7- 6.8 Å between Ce ions favor the localized magnetic moments that are observed in measurements of the magnetization. The strength of the Ruderman-Kittel-Kasuya- Yosida magnetic exchange interaction between the localized moments is severely limited by the large Ce-Ce separations and by weak hybridization between localized Ce 4f and itinerant electron states. Measurements of electrical resistivity performed down to 0.138 K were unable to observe evidence for the emergence of magnetic order;more » however, magnetically-ordered ground states with very low transition temperatures are still expected in these compounds despite the isolated nature of the localized magnetic moments. Such a fragile magnetic order could be highly susceptible to tuning via applied pressure, but evidence for the emergence of magnetic order has not been observed so far in our measurements up to 2.5 GPa.« less

  13. Nickel deficiency in RENi2-xP2 (RE=La, Ce, Pr). Combined crystallographic and physical property studies

    SciTech Connect (OSTI)

    Bauer, Eric D; Ronning, Filip; Thompson, Joe D; Sarrao, John L; Bobev, S; Xia, S

    2008-01-01

    Large single crystals from RENi{sub 2-x}P{sub 2} (RE = La, Ce, Pr) were synthesized from the pure elements using Sn as a metal flux, and their structures were established by X-ray crystallography. The title compounds were confirmed to crystallize in the body-centered tetragonal ThCr{sub 2}Si{sub 2} structure type (space group I4/mmm (No. 139); Pearson's symbol tI10), but with a significant stoichiometry breadth with respect to the transition metal. Systematic synthetic work, coupled with accurate structure refinements indicated strong correlation between the degree of Ni-deficiency and the reaction conditions. For four different PrNi{sub 2-x}P{sub 2} (x {le} 0.5) samples, temperature dependent dc magnetization measurements indicated typical local moment 4f-magnetism and a stable Pr{sup 3+} ground state. Field-dependent heat capacity data confirmed a ferromagnetic order at low temperature, and the variations of T{sub c} with the concentration of Ni defects are discussed. LaNi{sub 2-x}P{sub 2}, as expected was found to be Pauli-like paramagnetic in the studied temperature regime, while the Ce-analog CeNi{sub 2-x}P{sub 2} (x = 0.28(1)) showed the characteristics of a mixed valent Ce{sup 3+}/Ce{sup 4+} system with a possible Kondo temperature on the order of 230 K.

  14. High thermal stability of La2O3 and CeO2-stabilized tetragonal ZrO2

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

    Wang, Shichao; Xie, Hong; Lin, Yuyuan; Poeppelmeier, Kenneth R.; Li, Tao; Winans, Randall E.; Cui, Yanran; Ribeiro, Fabio H.; Canlas, Christian P.; Elam, Jeffrey W.; et al

    2016-02-15

    Catalyst support materials of tetragonal ZrO2, stabilized by either La2O3 (La2O3-ZrO2) or CeO2 (CeO2-ZrO2), were synthesized under hydrothermal conditions at 200 °C with NH4OH or tetramethylammonium hydroxide as the mineralizer. From In Situ synchrotron powder X-ray diffraction and small-angle X-ray scattering measurements, the calcined La2O3-ZrO2 and CeO2-ZrO2 supports were nonporous nanocrystallites that exhibited rectangular shapes with thermal stability up to 1000 °C in air. These supports had an average size of ~10 nm and a surface area of 59-97 m2/g. The catalysts Pt/La2O3-ZrO2 and Pt/CeO2-ZrO2 were prepared by using atomic layer deposition with varying Pt loadings from 6.3-12.4 wt %.more » Mono-dispersed Pt nanoparticles of ~3 nm were obtained for these catalysts. As a result, the incorporation of La2O3 and CeO2 into the t-ZrO2 structure did not affect the nature of the active sites for the Pt/ZrO2 catalysts for the water-gas-shift (WGS) reaction.« less

  15. Theoretical Study of Trimethylacetic Acid Adsorption on CeO 2 (111) Surface

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

    Wang, Weina; Thevuthasan, S.; Wang, Wenliang; Yang, Ping

    2016-01-11

    We investigated trimethylacetic acid (TMAA) adsorption on stoichiometric and oxygen-deficient CeO2(111) surfaces using density functional theory that accounts for the on-site Coulomb interaction via a Hubbard term (DFT+U) and long-range dispersion correction. Both the molecular state and dissociative state (TMAA → TMA– + H+) were identified on stoichiometric and oxygen-deficient CeO2(111) surfaces. For the stoichiometric surface, two thermodynamically favorable configurations with adsorption energies of the order of -30 kcal/mol are identified; one is a molecule adsorption state, and the other one is a dissociative state. For the oxygen-deficient surface, dissociative states are more favorable than molecular states. Moreover, the mostmore » favorable configuration is the dissociative adsorption of TMAA with the adsorption energy of the order of -77 kcal/mol. The dissociated TMA moiety takes the position of oxygen vacancy, forming three Ce–O bonds. The signature vibrational frequencies for these thermodynamically stable structures are reported as well as their electronic structures. The effects of long-range dispersion interactions are found to be negligible for geometries but important for adsorption energies.« less

  16. Hydrogenation of CO2 to methanol on CeOx/Cu(111) and ZnO/Cu(111) catalysts: Role of the metal-oxide interface and importance of Ce3+ sites

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

    Sanjaya D. Senanayake; Ramirez, Pedro J.; Waluyo, Iradwikanari; Kundu, Shankhamala; Mudiyanselage, Kumudu; Liu, Zongyuan; Liu, Zhi; Axnanda, Stephanus; Stacchiola, Dario J.; Evans, Jaime; et al

    2016-01-06

    The role of the interface between a metal and oxide (CeOx–Cu and ZnO–Cu) is critical to the production of methanol through the hydrogenation of CO2 (CO2 + 3H2 → CH3OH + H2O). The deposition of nanoparticles of CeOx or ZnO on Cu(111), θoxi < 0.3 monolayer, produces highly active catalysts for methanol synthesis. The catalytic activity of these systems increases in the sequence: Cu(111) < ZnO/Cu(111) < CeOx/Cu(111). The apparent activation energy for the CO2 → CH3OH conversion decreases from 25 kcal/mol on Cu(111) to 16 kcal/mol on ZnO/Cu(111) and 13 kcal/mol on CeOx/Cu(111). The surface chemistry of the highlymore » active CeOx–Cu(111) interface was investigated using ambient pressure X-ray photoemission spectroscopy (AP-XPS) and infrared reflection absorption spectroscopy (AP-IRRAS). Both techniques point to the formation of formates (HCOO–) and carboxylates (CO2δ–) during the reaction. Our results show an active state of the catalyst rich in Ce3+ sites which stabilize a CO2δ– species that is an essential intermediate for the production of methanol. Furthermore, the inverse oxide/metal configuration favors strong metal–oxide interactions and makes possible reaction channels not seen in conventional metal/oxide catalysts.« less

  17. Electronic structure of the heavy-fermion caged compound Ce?Pd??X? (X = Si, Ge) studied by density functional theory and photoelectron spectroscopy

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

    Yamaoka, Hitoshi; Jarrige, Ignace; Schwier, Eike F.; Arita, Masashi; Shimada, Kenya; Tsujii, Naohito; Jiang, Jian; Hayashi, Hirokazu; Iwasawa, Hideaki; Namatame, Hirofumi; et al

    2015-03-30

    The electronic structure of Ce?Pd??X? (X = Si, Ge) has been studied using detailed density functional theory (DFT) calculations and high-resolution photoelectron spectroscopy (PES) measurements. The orbital decomposition of the electronic structure by DFT calculations indicates that Ce atoms at the (8c) site surrounded by 16 Pd atoms have a more localized nature and a tendency to be magnetic. Ce atoms in the (4a) site surrounded by 12 Pd and 6 X atoms, on the other, show only a negligible magnetic moment. In the photoemission valence-band spectra we observe a strong f? (Ce??) component with a small fraction of fmore(Ce?) component. The spectral weight of f component near the Fermi level Ce?Pd??Si? is stronger than that for Ce?Pd??Ge? at the 4d-4f resonance, suggesting stronger c-f hybridization in the former. This may hint to the origin of the large electronic specific coefficient of Ce?Pd??Si? compared to Ce?Pd??Ge?.less

  18. Temperature Dependence of the Kondo Resonance and Its Satellites in CeCu{sub 2}Si{sub 2}

    SciTech Connect (OSTI)

    Reinert, F.; Ehm, D.; Schmidt, S.; Nicolay, G.; Huefner, S.; Kroha, J.; Trovarelli, O.; Geibel, C.

    2001-09-03

    We present high-resolution photoemission spectroscopy studies on the Kondo resonance of the strongly correlated Ce system CeCu{sub 2}Si {sub 2} . By exploiting the thermal broadening of the Fermi edge we analyze position, spectral weight, and temperature dependence of the low-energy 4f spectral features, whose major weight lies above the Fermi level E{sub F} . We also present theoretical predictions based on the single-impurity Anderson model using an extended noncrossing approximation, including all spin-orbit and crystal field splittings of the 4f states. The excellent agreement between theory and experiment provides strong evidence that the spectral properties of CeCu{sub 2}Si {sub 2} can be described by single-impurity Kondo physics down to T{approx}5 K .

  19. Influence of solvent on the morphology and photocatalytic properties of ZnS decorated CeO{sub 2} nanoparticles

    SciTech Connect (OSTI)

    Raubach, Cristiane W. Polastro, Lisnias; Ferrer, Mateus M.; Perrin, Andre; Perrin, Christiane; Albuquerque, Anderson R.; Buzolin, Prescila G. C.; Sambrano, Julio R.; Santana, Yuri B. V. de; Varela, Jos A.; Longo, Elson

    2014-06-07

    Herein, we report a theoretical and experimental study on the photocatalytic activity of CeO{sub 2} ZnS, and ZnS decorated CeO{sub 2} nanoparticles prepared by a microwave-assisted solvothermal method. Theoretical models were established to analyze electron transitions primarily at the interface between CeO{sub 2} and ZnS. As observed, the particle morphology strongly influenced the photocatalytic degradation of organic dye Rhodamine B. A model was proposed to rationalize the photocatalytic behavior of the prepared decorated systems taking into account different extrinsic and intrinsic defect distributions, including order-disorder effects at interfacial and intra-facial regions, and vacancy concentration.

  20. Update on the CeC PoP 704 MHz 5-cell cavity cryomodule design and fabrication

    SciTech Connect (OSTI)

    Brutus, J. C.; Belomestnykh, S.; Ben-Zvi, I.; Grimm, T.; Huang, Y.; Jecks, R.; Kelly, M.; Litvinenko, V.; Pinayev, I.; Reid, T.; Skaritka, J.; Snydstrup, L.; Than, R.; Tuozzolo, J.; Xu, W.; Yancey, J.; Gerbick, S.

    2015-05-03

    A 5-cell SRF cavity operating at 704 MHz will be used for the Coherent Electron Cooling Proof of Principle (CeC PoP) system under development for the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The CeC PoP experiment will demonstrate the new technique of cooling proton and ion beams that may increase the beam luminosity in certain cases, by as much as tenfold. The 704 MHz cavity will accelerate 2 MeV electrons from a 112 MHz SRF gun up to 22MeV. This paper provides an overview of the design, the project status and schedule of the 704 MHz 5-cell SRF for CeC PoP experiment.

  1. Selectivity loss of Pt/CeO{sub 2} PROX catalysts at low CO concentrations: mechanism and active site study.

    SciTech Connect (OSTI)

    Polster, C. S.; Zhang, R.; Cyb, M. T.; Miller, J. T.; Baertsch, C. D.

    2010-07-01

    CO and H{sub 2} oxidation were studied over a series of Pt/CeO{sub 2} catalysts with differing Pt loadings and dispersions. Kinetic rate analysis confirms the presence of dual Langmuir-Hinshelwood (L-H) and Mars and van Krevelen (M-vK) pathways and is used to explain the loss in CO oxidation selectivity at low CO concentrations. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) shows the strong CO coverage dependence on both CO and O{sub 2} concentrations and explains the transition from L-H to M-vK reaction character. Redox site measurements are performed on Pt/CeO{sub 2} catalysts by anaerobic titrations under conditions where the M-vK pathway dominates the reaction rate. Similar redox site densities per interfacial Pt atom suggest that interfacial Pt-O-Ce sites are responsible for M-vK redox activity.

  2. Unusual Kondo-hole effect and crystal-field frustration in Nd-doped CeRhIn

    Office of Scientific and Technical Information (OSTI)

    5 (Journal Article) | SciTech Connect Unusual Kondo-hole effect and crystal-field frustration in Nd-doped CeRhIn 5 Citation Details In-Document Search This content will become publicly available on July 5, 2017 Title: Unusual Kondo-hole effect and crystal-field frustration in Nd-doped CeRhIn 5 Authors: Rosa, P. F. S. ; Oostra, A. ; Thompson, J. D. ; Pagliuso, P. G. ; Fisk, Z. Publication Date: 2016-07-05 OSTI Identifier: 1260297 Type: Publisher's Accepted Manuscript Journal Name: Physical

  3. 6450-01-P, DOE 10 CFR Parts 430 and 431, Docket No. EERE-2010-BT-CE-0014

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

    RIN 1904-AC23, Draft Submission to Federal Register, Notice of Revisions to Energy Efficiency Enforcement Regulations, Request for Information/comment. | Department of Energy 6450-01-P, DOE 10 CFR Parts 430 and 431, Docket No. EERE-2010-BT-CE-0014 RIN 1904-AC23, Draft Submission to Federal Register, Notice of Revisions to Energy Efficiency Enforcement Regulations, Request for Information/comment. 6450-01-P, DOE 10 CFR Parts 430 and 431, Docket No. EERE-2010-BT-CE-0014 RIN 1904-AC23, Draft

  4. Magnetic structure of the antiferromagnetic Kondo lattice compounds CeRhAl4Si2 and CeIrAl4Si2

    SciTech Connect (OSTI)

    Ghimire, N. J.; Calder, S.; Janoschek, M.; Bauer, E. D.

    2015-06-01

    In this article, we have investigated the magnetic ground state of the antiferromagnetic Kondo-lattice compounds CeMAl4Si2(M = Rh, Ir) using neutron powder diffraction. Although both of these compounds show two magnetic transitions TN1 and TN2 in the bulk properties measurements, evidence for magnetic long-range order was only found below the lower transition TN2. Analysis of the diffraction profiles reveals a commensurate antiferromagnetic structure with a propagation vector k = (0, 0, 1/2). The magnetic moment in the ordered state of CeRhAl4Si2 and CeIrAl4Si2 were determined to be 1.14(2) and 1.41(3) ?B/Ce, respectively, and are parallel to the crystallographic c-axis in agreement with magnetic susceptibility measurements.

  5. Magnetic structure of the antiferromagnetic Kondo lattice compounds CeRhAl4Si2 and CeIrAl4Si2

    SciTech Connect (OSTI)

    Ghimire, N. J.; Calder, S.; Janoschek, M.; Bauer, E. D.

    2015-06-01

    In this article, we have investigated the magnetic ground state of the antiferromagnetic Kondo-lattice compounds CeMAl4Si2(M = Rh, Ir) using neutron powder diffraction. Although both of these compounds show two magnetic transitions TN1 and TN2 in the bulk properties measurements, evidence for magnetic long-range order was only found below the lower transition TN2. Analysis of the diffraction profiles reveals a commensurate antiferromagnetic structure with a propagation vector k = (0, 0, 1/2). The magnetic moment in the ordered state of CeRhAl4Si2 and CeIrAl4Si2 were determined to be 1.14(2) and 1.41(3) μB/Ce, respectively, and are parallel to the crystallographic c-axis in agreement with magnetic susceptibility measurements.

  6. Differential conductance and defect states in the heavy-fermion superconductor CeCoIn5

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

    John S. Van Dyke; Davis, James C.; Morr, Dirk K.

    2016-01-22

    We demonstrate that the electronic band structure extracted from quasiparticle interference spectroscopy [Nat. Phys. 9, 468 (2013)] and the theoretically computed form of the superconducting gaps [Proc. Natl. Acad. Sci. USA 111, 11663 (2014)] can be used to understand the dI/dV line shape measured in the normal and superconducting state of CeCoIn5 [Nat. Phys. 9, 474 (2013)]. In particular, the dI/dV line shape, and the spatial structure of defect-induced impurity states, reflects the existence of multiple superconducting gaps of dx2–y2 symmetry. As a result, these results strongly support a recently proposed microscopic origin of the unconventional superconducting state.

  7. Nanostructured Lanthanum Halides and CeBr3 for Nuclear Radiation and Detection

    SciTech Connect (OSTI)

    Paul Guss, Sanjoy Mukhopadhyay, Ron Guise, Ding Yuan

    2010-06-09

    Scintillator materials are used to detect, and in some cases identify, gamma rays. Higher performance scintillators are expensive, hard to manufacture, fragile, and sometimes require liquid nitrogen or cooling engines. But whereas lower-quality scintillators are cheap, easy to manufacture, and more rugged, their performance is lower. At issue: can the desirable qualities of high-and low-performance scintillators be combined to achieve better performance at lower cost? Preliminary experiments show that a LaF{sub 3}:Ce oleic acid-based nanocomposite exhibits a photopeak when exposed to {sup 137}Cs source gamma-radiation. The chemical synthesis of the cerium-doped lanthanum halide nanoparticles are scalable and large quantities of material can be produced at a time, unlike typical crystal growth processes such as the Bridgeman process. Using a polymer composite (Figure 1), produced by LANL, initial measurements of the unloaded and 8% LaF{sub 3}:Ce-loaded sample have been made using {sup 137}Cs sources. Figure 2 shows an energy spectrum acquired for CeF{sub 3}. The lighter plot is the measured polymer-only spectrum and the black plot is the spectrum from the nanocomposite scintillator. As the development of this material continues, the energy resolution is expected to improve and the photopeak-to-Compton ratio will become greater at higher loadings. These measurements show the expected Compton edge in the polymer-only sample, and the Compton edge and photo-peak expected in the nanophosphor composites that LANL has produced. Using a porous VYCORR with CdSe/ZnS core shell quantum dots, Letant has demonstrated that he has obtained signatures of the 241Am photopeak with energy resolution as good at NaI (Figure 3). We begin with the fact that CeBr{sub 3} crystals do not have a self-activity component as strong as the lanthanum halides. The radioactive 0.090% {sup 138}La component of lanthanum leads to significant self-activity, which will be a problem for very large

  8. Vortex Lattice Studies in CeCoIn₅ with H⊥c

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

    Das, P.; White, J. S.; Holmes, A. T.; Gerber, S.; Forgan, E. M.; Bianchi, A. D.; Kenzelmann, M.; Zolliker, M.; Gavilano, J. L.; Bauer, E. D.; et al

    2012-02-23

    We present small angle neutron scattering studies of the vortex lattice (VL) in CeCoIn₅ with magnetic fields applied parallel (H) to the antinodal [100] and nodal [110] directions. For H II 100], a single VL orientation is observed, while a 90° reorientation transition is found for H II [110]. For both field orientations and VL configurations we find a distorted hexagonal VL with an anisotropy, Γ=2.0±0.05. The VL form factor shows strong Pauli paramagnetic effects similar to what have previously been reported for H II [001]. At high fields, above which the upper critical field (Hc2) becomes a first-order transition,more » an increased disordering of the VL is observed.« less

  9. Theoretical studies of Ir5Th and Ir5Ce nanoscale precipitates in Ir

    SciTech Connect (OSTI)

    Morris, James R; Averill, Frank; Cooper, Valentino R

    2014-01-01

    Experimentally, it is known that very small amounts of thorium and/or cerium added to iridium metal form a precipitate, Ir5Th / Ir5Ce, which improves the high temperature mechanical properties of the resulting alloys. We demonstrate that there are low-energy configurations for nano-scale precipitates of these phases in Ir, and that these coherent arrangements may assist in producing improved mechanical properties. One precipitate/matrix orientation gives a particularly low interfacial energy, and a low lattice misfit. Nanolayer precipitates with this orientation are found to be likely to form, with little driving force to coarsen. The predicted morphology of the precipitates and their orientation with the matrix phase provide a potential experiment that could be used to test these predictions.

  10. Improved thermoelectric performance of n-type Ca and Ca-Ce filled skutterudites

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

    Thompson, Daniel R.; Liu, Chang; Ellison, Nicole D.; Salvador, James R.; Meyer, Martin S.; Haddad, Daad B.; Wang, Hsin; Cai, W.

    2014-12-28

    Thermoelectric (TE) technology for use in automotive waste heat recovery is being advanced by General Motors with support from the US Department of Energy. Skutterudites are a very promising material for this application of TE technology due to their superior mechanical properties and good TE performance. Double-filled YbxBayCo4Sb12 with ZT values around 1.1 at 750K are the best performing n-type skutterudites produced on a large scale using an economically viable approach of melt spinning (MS) in conjunction with spark plasma sintering (SPS). Another economical production method on the tons scale, the melt quench annealing (MQA) technique, has been recently claimedmore » by Treibacher Industrie AG, further information is available [G. Rogl et al., Acta Mater. 76, 434-448 (2014)]. A possible hurdle to commercial implementation of these materials is the use of rare earths as the fillers to reduce thermal conductivity and improve the electrical transport properties. It will be shown herein that skutterudites double-filled with Ca and Ce, both of which are lower-cost fillers, display markedly different TE properties depending on whether they are produced by MQA or MS + SPS synthesis techniques. Finally, Ca and Ce double-filled skutterudites prepared by MS + SPS have TE properties that are superior to the same compositions prepared by MQA and that are comparable to the best performing Yb and Ba filled materials. Furthermore, the results of this study suggest that the unusually poor transport properties of MQA Ca-filled skutterudites can be ascribed to deleterious secondary phases, which is contrary to reports in the literature attempting to explain these irregularities via band structure features.« less

  11. Improved thermoelectric performance of n-type Ca and Ca-Ce filled skutterudites

    SciTech Connect (OSTI)

    Thompson, Daniel R.; Liu, Chang; Ellison, Nicole D.; Salvador, James R.; Meyer, Martin S.; Haddad, Daad B.; Wang, Hsin; Cai, W.

    2014-12-28

    Thermoelectric (TE) technology for use in automotive waste heat recovery is being advanced by General Motors with support from the US Department of Energy. Skutterudites are a very promising material for this application of TE technology due to their superior mechanical properties and good TE performance. Double-filled Yb{sub x}Ba{sub y}Co{sub 4}Sb{sub 12} with ZT values around 1.1 at 750?K are the best performing n-type skutterudites produced on a large scale using an economically viable approach of melt spinning (MS) in conjunction with spark plasma sintering (SPS). Another economical production method on the tons scale, the melt quench annealing (MQA) technique, has been recently claimed by Treibacher Industrie AG, further information is available [G. Rogl et al., Acta Mater. 76, 434448 (2014)]. A possible hurdle to commercial implementation of these materials is the use of rare earths as the fillers to reduce thermal conductivity and improve the electrical transport properties. It will be shown herein that skutterudites double-filled with Ca and Ce, both of which are lower-cost fillers, display markedly different TE properties depending on whether they are produced by MQA or MS + SPS synthesis techniques. Ca and Ce double-filled skutterudites prepared by MS + SPS have TE properties that are superior to the same compositions prepared by MQA and that are comparable to the best performing Yb and Ba filled materials. Furthermore, the results of this study suggest that the unusually poor transport properties of MQA Ca-filled skutterudites can be ascribed to deleterious secondary phases, which is contrary to reports in the literature attempting to explain these irregularities via band structure features.

  12. Improved thermoelectric performance of n-type Ca and Ca-Ce filled skutterudites

    SciTech Connect (OSTI)

    Thompson, Daniel R.; Liu, Chang; Ellison, Nicole D.; Salvador, James R.; Meyer, Martin S.; Haddad, Daad B.; Wang, Hsin; Cai, W.

    2014-12-28

    Thermoelectric (TE) technology for use in automotive waste heat recovery is being advanced by General Motors with support from the US Department of Energy. Skutterudites are a very promising material for this application of TE technology due to their superior mechanical properties and good TE performance. Double-filled YbxBayCo4Sb12 with ZT values around 1.1 at 750K are the best performing n-type skutterudites produced on a large scale using an economically viable approach of melt spinning (MS) in conjunction with spark plasma sintering (SPS). Another economical production method on the tons scale, the melt quench annealing (MQA) technique, has been recently claimed by Treibacher Industrie AG, further information is available [G. Rogl et al., Acta Mater. 76, 434-448 (2014)]. A possible hurdle to commercial implementation of these materials is the use of rare earths as the fillers to reduce thermal conductivity and improve the electrical transport properties. It will be shown herein that skutterudites double-filled with Ca and Ce, both of which are lower-cost fillers, display markedly different TE properties depending on whether they are produced by MQA or MS + SPS synthesis techniques. Finally, Ca and Ce double-filled skutterudites prepared by MS + SPS have TE properties that are superior to the same compositions prepared by MQA and that are comparable to the best performing Yb and Ba filled materials. Furthermore, the results of this study suggest that the unusually poor transport properties of MQA Ca-filled skutterudites can be ascribed to deleterious secondary phases, which is contrary to reports in the literature attempting to explain these irregularities via band structure features.

  13. Transport properties of Ce{sub 2}Ni{sub 2}Sn and Ce{sub 2}Pd{sub 2.05}Sn{sub 0.95} Kondo lattice systems

    SciTech Connect (OSTI)

    Pinto, R.P.; Amado, M.M.; Braga, M.E.; de Azevedo, M.M.; Sousa, J.B.; Chevalier, B.; Etourneau, J.

    1997-04-01

    We report experimental data on thermoelectric power S, electrical resistivity {rho}, and the magnetoresistivity of the antiferromagnet Kondo stannides Ce{sub 2}Ni{sub 2}Sn (T{sub N}=4.7 K) and Ce{sub 2}Pd{sub 2.05}Sn{sub 0.95} (T{sub N}=4.7 K). The essential features of the S(T) curves resemble those of heavy fermion systems such as CeCu{sub 2}Si{sub 2}: a broad and positive maximum at intermediate temperatures, followed by a sharper negative minimum at lower temperatures. S values are is considerably smaller in Ce{sub 2}Pd{sub 2.05}Sn{sub 0.95} than in Ce{sub 2}Ni{sub 2}Sn. The positive peak originates from the incoherent Kondo scattering by the excited crystal field levels of the Ce ion ground state. The negative peak might be related to the shape of the density of states associated with the Abrikosov{endash}Suhl resonance. The change of sign in S(T) between its minimum and maximum at T{sup {asterisk}} can be assigned to the fact that the Fermi level sinks below the upper band at T{gt}T{sup {asterisk}}. This behavior and the maximum observed in the {rho}(T) curve at this temperature can be discussed in terms of the electron polaron model, although one must also take into account the crystal field effect. The role played by the crystal field effect, which is more important in Ce{sub 2}Pd{sub 2.05}Sn{sub 0.95}, is analyzed for this compound, providing the magnitude of the crystal field splitting. Magnetoresistivity was also measured in both compounds. The results are consistent with the important role of the Kondo effect at low temperatures and suggest the splitting of the double degenerate bands at T{gt}T{sup {asterisk}}. {copyright} {ital 1997 American Institute of Physics.}

  14. The effect of Au and Ni doping on the heavy fermion state of the Kondo lattice antiferromagnet CePtZn

    SciTech Connect (OSTI)

    Dhar, S. K.; Aoki, Y.; Suemitsu, B.; Miyazaki, R.; Provino, A.; Manfrinetti, P.

    2014-05-07

    We have probed the effect of doping CePtZn with Au and Ni and also investigated in detail the magnetic behavior of the iso-structural CeAuZn. A magnetic ground state is observed in both CePt{sub 0.9}Au{sub 0.1}Zn and CePt{sub 0.9}Ni{sub 0.1}Zn with T{sub N}?=?2.1 and 1.1?K and the coefficient of the linear term of electronic heat capacity ??=?0.34 and 0.9?J/mol K{sup 2}, respectively. The corresponding values for CePtZn are 1.7?K and 0.6?J/mol K{sup 2}. The altered values of T{sub N} and ? show that the electronic correlations in CePtZn are affected by doping with Au and Ni. CeAuZn orders magnetically near 1.7?K and its electrical resistivity shows a normal metallic behavior. Together with a ? of 0.022?J/mol K{sup 2} the data indicate a weak 4f-conduction electron hybridization in CeAuZn characteristic of normal trivalent cerium based systems.

  15. The effect of Ce{sup 4+} incorporation on structural, morphological and photocatalytic characters of ZnO nanoparticles

    SciTech Connect (OSTI)

    Kannadasan, N.; Shanmugam, N. Cholan, S.; Sathishkumar, K.; Viruthagiri, G.; Poonguzhali, R.

    2014-11-15

    We report a simple chemical precipitation method for the preparation of undoped and cerium doped ZnO nanocrystals. The concentration of cerium in the products can be controlled in the range of 0.0250.125 mol. The structure and chemical compositions of the products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy; energy dispersive spectrum and Fourier transform infrared spectroscopy. The results demonstrate that Ce{sup 4+} ions were successfully incorporated into the lattice position of Zn{sup 2+} ions in ZnO. The morphology of the products was analyzed by field emission scanning electron microscopy and confirmed by high resolution transmission electron microscope analysis. The optical properties of the products were studied by ultravioletvisible and room temperature photoluminescence measurements. The photoluminescence emission spectra of Ce-doped ZnO showed enhanced visible emissions as a result of 5d ? 4f transition of cerium. In particular, a novel photocatalytic activity of the products was assessed using methylene blue. The obtained result reveals that Ce-doped products show higher reduction efficiency for methylene blue than the undoped ZnO. - Highlights: Nanocrystals of ZnO and ZnO:Ce{sup 4+} were grown. XPS results confirmed the incorporated cerium in tetravalence. PL emission exhibited 5d ? 4f transition on cerium doping. Doped ZnO decolorizes MB faster than undoped ZnO.

  16. Kondo lattice and antiferromagnetic behavior in quaternary CeTAl4Si2 (T = Rh, Ir) single crystals

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

    Maurya, Arvind; Kulkarni, Ruta; Thamizhavel, Arumugam; Paudyal, Durga; Dhar, Sudesh Kumar

    2016-02-26

    Here, we have explored in detail the anisotropic magnetic properties of CeRhAl4Si2 and CeIrAl4Si2, which undergo two antiferromagnetic transitions, at TN1 = 12.6 and 15.5 K, followed by a second transition at TN2 = 9.4 and 13.8 K, respectively, with the [001]-axis as the relatively easy axis of magnetization. The electrical resistivity at ambient and applied pressure provides evidence of Kondo interaction in both compounds, further supported by a reduced value of the entropy associated with the magnetic ordering. The Sommerfeld coefficient γ is inferred to be 195.6 and 49.4 mJ/(mol K2) for CeRhAl4Si2 and CeIrAl4Si2, respectively, classifying these materialsmore » as moderate heavy-fermion compounds. The crystal electric field energy levels are derived from the peak seen in the Schottky heat capacity. Furthermore, we have also performed electronic structure calculations by using the local spin density approximation + U [LSDA+U] approach, which provide physical insights on the observed magnetic behavior of these two compounds.« less

  17. Investigation of the physical properties of the tetragonal CeMAl4Si2 (M = Rh, Ir, Pt) compounds

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

    Ghimire, N. J.; Ronning, F.; Williams, D. J.; Scott, B. L.; Luo, Yongkang; Thompson, J. D.; Bauer, E. D.

    2014-12-15

    The synthesis, crystal structure and physical properties studied by means of x-ray diffraction, magnetic, thermal and transport measurements of CeMAl4Si2 (M = Rh, Ir, Pt) are reported, along with the electronic structure calculations for LaMAl4Si2 (M = Rh, Ir, Pt). These materials adopt a tetragonal crystal structure (space group P4/mmm) comprised of BaAl4 blocks, separated by MAl2 units, stacked along the c-axis. Both CeRhAl4Si2 and CeIrAl4Si2 order antiferromagnetically below TN1 = 14 and 16 K, respectively, and undergo a second antiferromagnetic transitition at lower temperature (TN2 = 9 and 14 K, respectively). CePtAl4Si2 orders ferromagnetically below TC = 3 Kmore » with an ordered moment of μsat = 0.8 μB for a magnetic field applied perpendicular to the c-axis. Electronic structure calculations reveal quasi-2D character of the Fermi surface.« less

  18. Superior performance of Ni-W-Ce mixed-metal oxide catalysts for ethanol steam reforming: Synergistic effects of W- and Ni-dopants

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

    Rodriguez, Jose A.; Liu, Zongyuan; Xu, Wenqian; Yao, Siyu; Johnson-Peck, Aaron C.; Zhao, Fuzhen; Michorczyk, Piotr; Kubacka, Anna; Stach, Eric A.; Fernandez-Garica, Marcos; et al

    2014-11-26

    The ethanol steam reforming (ESR) reaction was studied over a series of Ni-W-Ce oxide catalysts. The structures of the catalysts were characterized using in-situ techniques including X-ray diffraction, Pair Distribution Function, X-ray absorption fine structure and transmission electron microscopy; while possible surface intermediates for the ESR reaction were investigated by Diffuse Reflectance Infrared Fourier Transform Spectroscopy. In these materials, all the W and part of the Ni were incorporated into the CeO? lattice, with the remaining Ni forming highly dispersed nano NiO (moreThe Ni-W-Ce systeme exhibited a much larger lattice strain than those seen for Ni-Ce and W-Ce. Synergistic effects between Ni and W inside ceria produced a substantial amount of defects and O vacancies that led to high catalytic activity, selectivity and stability (i.e. resistance to coke formation) during ethanol steam reforming.less

  19. Synthesis, Structures, and Magnetic Properties of Rare-Earth Cobalt Arsenides, RCo2As2 (R = La, Ce, Pr, Nd)

    SciTech Connect (OSTI)

    Thompson, Corey; Tan, Xiaoyan; Kovnir, Kirill; Garlea, Vasile O; Shatruk, Michael

    2014-01-01

    Four rare-earth cobalt arsenides, RCo2As2 (R = La, Ce, Pr, Nd), were obtained by reactions of constituent elements in molten Bi. The use of Bi flux also allowed the growth of representative single crystals. All compounds are isostructural and belong to the ThCr2Si2 structure type (space group I4/mmm). The formation of Co vacancies is observed in all structures, while the structures of La- and Ce-containing compounds also show incorporation of minor Bi defects next to the R crystallographic site. Correspondingly, the general formula of these materials can be written as R1 xBixCo2 As2, with x/ = 0.03/0.1, 0.05/0.15, 0/0.2, and 0/0.3 for R = La, Ce, Pr, and Nd, respectively. All compounds exhibit high-temperature ferromagnetic ordering of Co magnetic moments in the range of 150-200 K. Electronic band structure calculations revealed a high peak in the density of states at the Fermi level, thus supporting the itinerant nature of magnetism in the Co sublattice. The magnetic ordering in the lanthanide sublattice takes place at lower temperatures, with the R moments aligning antiparallel to the Co moments to give a ferrimagnetic ground state. The measurements on oriented single crystals demonstrated significant magnetic anisotropy in the ferrimagnetic state, with the preferred moment alignment along the c axis of the tetragonal lattice. Neutron powder diffraction failed to reveal the structure of magnetically ordered states, but confirmed the presence of Co vacancies. X-ray absorption near-edge structure spectroscopy on Ce1.95Bi0.05Co1.85As2 showed the average oxidation state of Ce to be +3.06. Solid state NMR spectroscopy revealed a substantially reduced hyperfine field on the Co atoms in the vicinity of Bi defects.

  20. Ionic liquid-assisted sonochemical preparation of CeO2 nanoparticles for CO oxidation

    SciTech Connect (OSTI)

    Alammar, Tarek; Noei, Heshmat; Wang, Yuemin; Grünert, Wolfgang; Mudring, Anja -Verena

    2014-10-10

    CeO2 nanoparticles were synthesized via a one-step ultrasound synthesis in different kinds of ionic liquids based on bis(trifluoromethanesulfonylamide, [Tf2N], in combination with various cations including 1-butyl-3-methylimidazolium ([C4mim]+), 1-ethyl-2,3-dimethylimidazolium ([Edimim]+), butyl-pyridinium([Py4]+), 1-butyl-1-methyl-pyrrolidinium ([Pyrr14]+), and 2-hydroxyethyl-trimethylammonium ([N1112OH]+). Depending on synthetic parameters, such as ionic liquid, Ce(IV) precursor, heating method, and precipitator, formed ceria exhibits different morphologies, varying from nanospheres, nanorods, nanoribbons, and nanoflowers. The morphology, crystallinity, and chemical composition of the obtained materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and N2 adsorption. The structural and electronic properties of the as-prepared CeO2 samples were probed by CO adsorption using IR spectroscopy under ultrahigh vacuum conditions. The catalytic activities of CeO2 nanoparticles were investigated in the oxidation of CO. CeO2 nanospheres obtained sonochemically in [C4mim][Tf2N] exhibit the best performance for low-temperature CO oxidation. As a result, the superior catalytic performance of this material can be related to its mesoporous structure, small particle size, large surface area, and high number of surface oxygen vacancy sites.

  1. Reverse micelles directed synthesis of TiO{sub 2}-CeO{sub 2} mixed oxides and investigation of their crystal structure and morphology

    SciTech Connect (OSTI)

    Matejova, Lenka; Vales, Vaclav; Fajgar, Radek; Matej, Zdenek; Holy, Vaclav; Solcova, Olga

    2013-02-15

    The synthesis of TiO{sub 2}-CeO{sub 2} mixed oxides based on the sol-gel process controlled within reverse micelles of non-ionic surfactant Triton X-114 in cyclohexane is reported. The crystallization, phase composition, trends in nanoparticles growth and porous structure properties are studied as a function of Ti:Ce molar composition and annealing temperature by in-situ X-ray diffraction, Raman spectroscopy and physisorption. The brannerite-type CeTi{sub 2}O{sub 6} crystallizes as a single crystalline phase at Ti:Ce molar composition of 70:30 and in the mixture with cubic CeO{sub 2} and anatase TiO{sub 2} for composition 50:50. At Ti:Ce molar ratios 90:10 and 30:70 the mixtures of TiO{sub 2} anatase, rutile and cubic CeO{sub 2} appear. In these mixtures TiO{sub 2} rutile is formed at higher temperatures than conventionally. Additionally, the amount of a present amorphous phase in individual mixtures was estimated from diffraction data. The porous structure morphology depends both on molar composition and annealing temperature. This is correlated with the presence of carbon impurities of different character. - Graphical abstract: The phase composition of Ti90--Ce10 and Ti50--Ce50 oxide mixtures as a function of annealing temperature. The amount of the amorphous phase was estimated and attributed to TiO{sub 2}. Highlights: Black-Right-Pointing-Pointer Ti/Ce oxides were prepared using reverse micelles of Triton X-114. Black-Right-Pointing-Pointer Crystallization of TiO{sub 2}, CeO{sub 2} or CeTi{sub 2}O{sub 6} depends on Ti:Ce molar ratio. Black-Right-Pointing-Pointer Amorphous phase attributed to TiO{sub 2} was identified. Black-Right-Pointing-Pointer Metal oxides surface area is influenced by the character of present carbon impurities.

  2. Structural and magnetic phase transitions in CeCu6-xTx (T = Ag,Pd)

    SciTech Connect (OSTI)

    Poudel, Lekhanath N.; De la cruz, Clarina; Payzant, E. Andrew; Koehler, Michael R.; May, Andrew F.; Garlea, Vasile O.; Taylor, Alice E.; Parker, David S.; Cao, Huibo B.; McGuire, Michael A.; Tian, Wei; Matsuda, Masaaki; Jeen, Hyoung Jeen; Lee, Ho Nyung; Hong, Tao; Calder, Stuart A.; Lumsden, Mark D.; Zhou, Haidong; Keppens, Veerle; Mandrus, D.; Christianson, Andrew D.

    2015-12-15

    The structural and the magnetic properties of CeCu6-xAgx (0 ≤ x ≤ 0.85) and CeCu6-xPdx (0 ≤ x ≤ 0.4) have been studied using neutron diffraction, resonant ultrasound spectroscopy (RUS), x-ray diffraction measurements, and first principles calculations. The structural and magnetic phase diagrams of CeCu6-xAgx and CeCu6-xPdx as a function of Ag/Pd composition are reported. The end member, CeCu6, undergoes a structural phase transition from an orthorhombic (Pnma) to a monoclinic (P21/c) phase at 240 K. In CeCu6-xAgx, the structural phase transition temperature (Ts) decreases linearly with Ag concentration and extrapolates to zero at xS ≈ 0.1. The structural transition in CeCu6-xPdx remains unperturbed with Pd substitution within the range of our study. The lattice constant b slightly decreases with Ag/Pd doping, whereas a and c increase with an overall increase in the unit cell volume. Both systems, CeCu6-xAgx and CeCu6-xPdx, exhibit a magnetic quantum critical point (QCP), at x ≈ 0.2 and x ≈ 0.05, respectively. Near the QCP, long range antiferromagnetic ordering takes place at an incommensurate wave vector (δ1 0 δ2), where δ1 ~ 0.62, δ2 ~ 0.25, x = 0.125 for CeCu6-xPdx and δ1 ~ 0.64, δ2 ~ 0.3, x = 0.3 for CeCu6-xAgx. As a result, the magnetic structure consists of an amplitude modulation of the Ce moments which are aligned along the c axis of the orthorhombic unit cell.

  3. Kondo hole behavior in Ce{sub 0.97} La{sub 0.03}Pd{sub 3}

    SciTech Connect (OSTI)

    Lawrence, J.M.; Graf, T.; Hundley, M.F.; Mandrus, D.; Thompson, J.D. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Lacerda, A.; Torikachvili, M.S. [National High Magnetic Field Laboratory, Pulse Facility, Los Alamos, New Mexico 87545 (United States)] [National High Magnetic Field Laboratory, Pulse Facility, Los Alamos, New Mexico 87545 (United States); Sarrao, J.L.; Fisk, Z. [National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306 (United States)] [National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306 (United States)

    1996-05-01

    We present results for the resistivity, the magnetoresistance, and the specific heat of Ce{sub 0.97}La{sub 0.03}Pd{sub 3} and CePd{sub 3}. The impurity contributions to these measurements follow the predictions of the single-impurity Kondo model for a Kondo temperature {ital T}{sub {ital L}}{approx_equal}65 K, assuming that the impurity behaves as a crystal-field split ({Gamma}{sub 7}) doublet. Assuming a {ital J}=5/2 impurity, the value of {ital T}{sub {ital L}} needed to fit these experiments varies from 65 to 125 K. The contribution to the susceptibility may be too small to be explained by the model. These results address whether the nonmagnetic impurity behaves as a Kondo hole. {copyright} {ital 1996 The American Physical Society.}

  4. Combined local-density and dynamical mean field theory calculations for the compressed lanthanides Ce, Pr, and Nd

    SciTech Connect (OSTI)

    McMahan, A K

    2005-03-30

    This paper reports calculations for compressed Ce (4f{sup 1}), Pr (4f{sup 2}), and Nd (4f{sup 3}) using a combination of the local-density approximation (LDA) and dynamical mean field theory (DMFT), or LDA+DMFT. The 4f moment, spectra, and the total energy among other properties are examined as functions of volume and atomic number for an assumed face-centered cubic (fcc) structure. These materials are seen to be strongly localized at ambient pressure and for compressions up through the experimentally observed fcc phases ({gamma} phase for Ce), in the sense of having fully formed Hund's rules moments and little 4f spectral weight at the Fermi level. Subsequent compression for all three lanthanides brings about significant deviation of the moments from their Hund's rules values, a growing Kondo resonance at the fermi level, an associated softening in the total energy, and quenching of the spin orbit since the Kondo resonance is of mixed spin-orbit character while the lower Hubbard band is predominantly j = 5/2. while the most dramatic changes for Ce occur within the two-phase region of the {gamma}-{alpha} volume collapse transition, as found in earlier work, those for Pr and Nd occur within the volume range of the experimentally observed distorted fcc (dfcc) phase, which is therefore seen here as transitional and not part of the localized trivalent lanthanide sequence. The experimentally observed collapse to the {alpha}-U structure in Pr occurs only on further compression, and no such collapse is found in Nd. These lanthanides start closer to the localized limit for increasing atomic number, and so the theoretical signatures noted above are also offset to smaller volume as well, which is possibly related to the measured systematics of the size of the volume collapse being 15%, 9%, and none for Ce, Pr, and Nd, respectively.

  5. One-, two-, and three-channel Kondo effects for a model Ce{sup 3+} impurity in a metal

    SciTech Connect (OSTI)

    Kim, T.; Cox, D.L.

    1997-05-01

    We present studies of a simple Anderson model Hamiltonian for Ce{sup 3+} ions in cubic symmetry with three configurations (f{sup 0},f{sup 1},f{sup 2}). In different parameter regimes, our model Hamiltonian maps to the one-, two-, and three-channel spin-1/2 Kondo models. Using third-order scaling (perturbative renormalization group) analysis, we study the stability of the non-Fermi-liquid fixed point of the two-channel Kondo model for Ce{sup 3+} ions in cubic symmetry against the one-channel Kondo interaction. Using the noncrossing approximation (NCA), we also report detailed studies for our simplified model of the competition between the Fermi-liquid fixed point of the one-channel Kondo model and the non-Fermi fixed points of the two- and three-channel Kondo models. We provide the phase diagram in the model parameter space and study the thermodynamics and the transport properties of our simplified model Hamiltonian. Thermodynamics and transport coefficients show distinct behaviors for different numbers of channels. We confirm in detail that the NCA is a valid numerical method for the overcompensated multichannel S{sub I}=1/2 Anderson models. Our model study might be relevant to the non-Fermi-liquid alloy Ce{sub 1{minus}x}La{sub x}Cu{sub 2.2}Si{sub 2}. {copyright} {ital 1997} {ital The American Physical Society}

  6. Strongly enhanced oxygen ion transport through samarium-doped CeO2 nanopillars in nanocomposite films

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

    Yang, Sang Mo; Lee, Shinbuhm; Jian, Jie; Zhang, Wenrui; Lu, Ping; Jia, Quanxi; Wang, Haiyan; Won Noh, Tae; Kalinin, Sergei V.; MacManus‐Driscoll, Judith L.

    2015-10-08

    Enhancement of oxygen ion conductivity in oxides is important for low-temperature (<500 °C) operation of solid oxide fuel cells, sensors and other ionotronic devices. While huge ion conductivity has been demonstrated in planar heterostructure films, there has been considerable debate over the origin of the conductivity enhancement, in part because of the difficulties of probing buried ion transport channels. Here we create a practical geometry for device miniaturization, consisting of highly crystalline micrometre-thick vertical nanocolumns of Sm-doped CeO2 embedded in supporting matrices of SrTiO3. The ionic conductivity is higher by one order of magnitude than plain Sm-doped CeO2films. Then bymore » using scanning probe microscopy, we show that the fast ion-conducting channels are not exclusively restricted to the interface but also are localized at the Sm-doped CeO2 nanopillars. Furthermore, this work offers a pathway to realize spatially localized fast ion transport in oxides of micrometre thickness.« less

  7. Influence of Electron Doping on Magnetic Order in CeRu2Al10

    SciTech Connect (OSTI)

    Kobayashi, Riki; Kaneko, Koji; Saito, Kotaro; Mignot, Jean-Michel; André, Gilles; Robert, Julien; Wakimoto, Shuichi; Matsuda, Masaaki; Chi, Songxue; Haga, Yoshinori; Matsuda, Tatsuma D.; Yamamoto, Etsuji; Nishioka, Takashi; Matsumura, Masahiro; Tanida, Hiroshi; Sera, Masafumi

    2014-09-17

    The effect of electron doping by the substitution of Rh for Ru on unconventional magnetic order in CeRu2Al10 was investigated via neutron powder diffraction. In Ce(Ru1-xRhx)2Al10 with x = 0.05, 0.12, and 0.2, reorientation of the ordered moment from the c- to the a-axis takes place in all samples, while the ordering vector q=(0 1 0) remains unchanged within this concentration range. The moment reorientation is accompanied by an enhancement in its size by a factor of ~2.4, from μ=0.43 μB at x=0 to μ =1.06, 1.04, and 1.02 μB for x=0.05, 0.12 and 0.2, respectively. The continuous decrease in N´eel temperature T0(TN), despite an abrupt increase in μ , underlines the strong anisotropy in the exchange interaction in CeRu2Al10, and the fact that this anisotropy is easily suppressed by electron doping.

  8. Crystal structure and thermal expansion of a CsCe2Cl7 scintillator

    SciTech Connect (OSTI)

    Zhuravleva, M.; Lindsey, A.; Chakoumakos, B. C.; Custelcean, R.; Meilleur, F.; Hughes, R. W.; Kriven, W. M.; Melcher, C. L.

    2015-04-06

    Here we used single-crystal X-ray diffraction data to determine crystal structure of CsCe2Cl7. It crystallizes in a P1121/b space group with a = 19.352(1) Å, b = 19.352(1) Å, c = 14.838(1) Å, γ = 119.87(2) ° , and V = 4818.6(5) Å3. Differential scanning calorimetry measurements combined with the structural evolution of CsCe2Cl7 via X-ray diffractometry over a temperature range from room temperature to the melting point indicates no obvious intermediate solid-solid phase transitions. The anisotropy in the average linear coefficient of thermal expansion of the a axis (21.3 10-6/ °C) with respect to the b and c axes (27.0 10-6/ °C) was determined through lattice parameter refinement of the temperature dependent diffraction patterns. Lastly, these findings suggest that the reported cracking behavior during melt growth of CsCe2Cl7 bulk crystals using conventional Bridgman and Czochralski techniques may be largely attributed to the anisotropy in thermal expansion.

  9. Effect of Oxygen Defects on the Catalytic Performance of VOx/CeO2 Catalysts for Oxidative Dehydrogenation of Methanol

    SciTech Connect (OSTI)

    Li, Yan; Wei, Zhehao; Gao, Feng; Kovarik, Libor; Baylon, Rebecca A.; Peden, Charles HF; Wang, Yong

    2015-05-01

    In this work, CeO2 nanocubes with controlled particle size and dominating (100) facets are synthesized as supports for VOx catalysts. Combined TEM, SEM, XRD, and Raman study reveals that the oxygen vacancy density of CeO2 supports can be tuned by tailoring the particle sizes without altering the dominating facets, where smaller particle sizes result in larger oxygen vacancy densities. At the same vanadium coverage, the VOx catalysts supported on small-sized CeO2 supports with higher oxygen defect densities exhibit promoted redox property and lower activation energy for methoxyl group decomposition, as evidenced by H2-TPR and methanol TPD study. These results further confirm that the presence of oxygen vacancies plays an important role in promoting the activity of VOx species in methanol oxidation. We gratefully acknowledge financial support from the U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. Part of this work was conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is a multiprogram national laboratory operated for the DOE by Battelle.

  10. Remarkably robust and correlated coherence and antiferromagnetism in (Ce1-xLax)Cu2Ge2

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

    Hodovanets, H.; Bud’ko, S. L.; Straszheim, W. E.; Taufour, V.; Mun, E. D.; Kim, H.; Flint, R.; Canfield, P. C.

    2015-06-08

    We present magnetic susceptibility, resistivity, specific heat, and thermoelectric power measurements on (Ce1-xLax)Cu2Ge2 single crystals (0 ≤ x ≤ 1). With La-substitution, the antiferromagnetic temperature TN is suppressed in an almost linear fashion and moves below 0.36 K, the base temperature of our measurements for x > 0.8. Surprisingly, in addition to robust antiferromagnetism, the system also shows low temperature coherent scattering below Tcoh up to ~0.9 of La, indicating a small percolation limit ~9% of Ce. Tcoh as a function of magnetic field was found to have different behavior for x < 0.9 and x > 0.9. Remarkably, (Tcoh)2more » at H = 0 was found to be linearly proportional to TN. In conclusion, the jump in the magnetic specific heat δCm at TN as a function of TK/TN for (Ce1-xLax)Cu2Ge2 follows the theoretical prediction based on the molecular field calculation for the S = 1/2 resonant level model.« less

  11. Strongly enhanced oxygen ion transport through samarium-doped CeO2 nanopillars in nanocomposite films

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

    Yang, Sangmo; Lee, Shinbuhm; Jian, Jie; Zhang, Wenrui; Lu, Ping; Jia, Quanxi; Wang, Haiyan; Noh, Tae Won; Kalinin, Sergei V.; MacManus-Driscoll, Judith L.

    2015-10-08

    Enhancement of oxygen ion conductivity in oxides is important for low-temperature (<500 °C) operation of solid oxide fuel cells, sensors and other ionotronic devices. While huge ion conductivity has been demonstrated in planar heterostructure films, there has been considerable debate over the origin of the conductivity enhancement, in part because of the difficulties of probing buried ion transport channels. Here we create a practical geometry for device miniaturization, consisting of highly crystalline micrometre-thick vertical nanocolumns of Sm-doped CeO2 embedded in supporting matrices of SrTiO3. The ionic conductivity is higher by one order of magnitude than plain Sm-doped CeO2 films. Bymore » using scanning probe microscopy, we show that the fast ion-conducting channels are not exclusively restricted to the interface but also are localized at the Sm-doped CeO2 nanopillars. This work offers a pathway to realize spatially localized fast ion transport in oxides of micrometre thickness.« less

  12. Strongly enhanced oxygen ion transport through samarium-doped CeO2 nanopillars in nanocomposite films

    SciTech Connect (OSTI)

    Yang, Sang Mo; Lee, Shinbuhm; Jian, Jie; Zhang, Wenrui; Lu, Ping; Jia, Quanxi; Wang, Haiyan; Won Noh, Tae; Kalinin, Sergei V.; MacManus?Driscoll, Judith L.

    2015-10-08

    Enhancement of oxygen ion conductivity in oxides is important for low-temperature (<500 C) operation of solid oxide fuel cells, sensors and other ionotronic devices. While huge ion conductivity has been demonstrated in planar heterostructure films, there has been considerable debate over the origin of the conductivity enhancement, in part because of the difficulties of probing buried ion transport channels. Here we create a practical geometry for device miniaturization, consisting of highly crystalline micrometre-thick vertical nanocolumns of Sm-doped CeO2 embedded in supporting matrices of SrTiO3. The ionic conductivity is higher by one order of magnitude than plain Sm-doped CeO2films. Then by using scanning probe microscopy, we show that the fast ion-conducting channels are not exclusively restricted to the interface but also are localized at the Sm-doped CeO2 nanopillars. Furthermore, this work offers a pathway to realize spatially localized fast ion transport in oxides of micrometre thickness.

  13. SESAME 96170, a solid-liquid equation of state for CeO2

    SciTech Connect (OSTI)

    Chisolm, Eric D.

    2014-05-02

    I describe an equation of state (EOS) for the low-pressure solid phase and liquid phase of cerium (IV) oxide, CeO2. The models and parameters used to calculate the EOS are presented in detail, and I compare with data for the full-density crystal. Hugoniot data are available only for high-porosity powders, and I discuss difficulties in comparing with such data. I have constructed SESAME 96170, an EOS for cerium (IV) oxide that includes the ambient solid and liquid phases. The EOS extends over the full standard SESAME range, but should not be used at low temperatures and high densities because of the lack of a high-pressure solid phase. I have described the models used to compute the three terms of the EOS (cold curve, nuclear, and thermal electronic), and I have given the parameters used in the models. They were determined by comparison with experimental data at P = 1 atm, including the constant-pressure specific heat, coefficient of thermal expansion, and melting and boiling points. The EOS compares well with data in its intended range of validity, but the presence of high-frequency optical modes in its phonon spectrum limits the agreement of our models with thermal data. The next step is to construct a multiphase EOS that includes the low- and high-pressure solid phases and the liquid. The DAC data from Duclos will most strongly constrain the parameters of the high-pressure solid. A remaining issue is the comparison of the crystal-density EOS with experimental Hugoniot data, which are taken at much lower initial data because the samples are porous powders. A satisfactory means of modeling porosity, allowing comparison of theory and experiment, has not yet been produced.

  14. Methanol conversion to light olefins over nanostructured CeAPSO-34 catalyst: Thermodynamic analysis of overall reactions and effect of template type on catalytic properties and performance

    SciTech Connect (OSTI)

    Aghamohammadi, Sogand; Haghighi, Mohammad; Charghand, Mojtaba

    2014-02-01

    Graphical abstract: In this research nanostructured CeAPSO-34 was synthesized to explore the effect of TEAOH and morpholine on its physiochemical properties and MTO performance. Prepared catalysts were characterized with XRD, FESEM, BET, FTIR and NH3-TPD techniques. The results indicated that the nature of the template determines the physiochemical properties of CeAPSO-34 due to different rate of crystal growth. The catalyst obtained by using morpholine showed longer life time as well as sustaining light olefins selectivity at higher values. Furthermore, a comprehensive thermodynamic analysis of overall reactions network was carried out to address the major channels of methanol to olefins conversion. - Highlights: • Introduction of Ce into SAPO-34 framework. • Comparison of CeAPSO-34 synthesized using morpholine and TEAOH. • The nature of the template determines the physiochemical properties of CeAPSO-34. • Morpholine enhances catalyst lifetime in MTO process. • Presenting a complete reaction network for MTO process. - Abstract: TEAOH and morpholine were employed in synthesis of nanostructured CeAPSO-34 molecular sieve and used in methanol to olefins conversion. Prepared samples were characterized by XRD, FESEM, EDX, BET, FTIR and NH{sub 3}-TPD techniques. XRD patterns reflected the higher crystallinity of the catalyst synthesized with morpholine. The FESEM results indicated that the nature of the template determines the morphology of nanostructured CeAPSO-34 due to different rate of crystal growth. There was a meaningful difference in the strength of both strong and weak acid sites for CeAPSO-34 catalysts synthesized with TEAOH and morpholine templates. The catalyst synthesized with morpholine showed higher desorption temperature of both weak and strong acid sites evidenced by NH{sub 3}-TPD characterization. The catalyst obtained using morpholine template had the longer lifetime and sustained desired light olefins at higher values. A comprehensive

  15. Structural characterization of the CeO{sub 2}/Gd{sub 2}O{sub 3} mixed system by synchrotron X-ray diffraction

    SciTech Connect (OSTI)

    Artini, Cristina; Costa, Giorgio A.; Pani, Marcella; Lausi, Andrea; Plaisier, Jasper

    2012-06-15

    The structural determination of the CeO{sub 2}/Gd{sub 2}O{sub 3} mixed system is a non-trivial problem because of the close resemblance between the ionic sizes of Ce{sup 4+} and Gd{sup 3+} and between the crystal structures of CeO{sub 2} and Gd{sub 2}O{sub 3}. (Ce{sub 1-x}Gd{sub x})O{sub 2-x/2} powder samples with x ranging between 0 and 1 have been synthesized by coprecipitation of mixed oxalates and subsequent thermal decomposition in air at 1200 Degree-Sign C followed by slow cooling. Synchrotron powder X-ray diffraction data were collected and refined by the Rietveld method. Lattice parameters do not follow Vegard's law and no peak splitting has been observed for any composition, meaning that no biphasic regions exist over the whole compositional range. The same hybrid structural model - a proper mixture of the structures of the two pure oxides - was used for the refinements, allowing to account for the data observed. - graphical abstract: Substituting Ce{sup 4+} by Gd{sup 3+}, a gradual transition from the F structure (typical of CeO{sub 2}) to the C structure (typical of Gd{sub 2}O{sub 3}) takes place. The lattice parameters do not follow Vegard's law. Highlights: Black-Right-Pointing-Pointer A structural study of Ce-Gd mixed oxides has been performed. Black-Right-Pointing-Pointer In (Ce{sub 1-x}Gd{sub x})O{sub 2-x/2} a solid solution forms for 0{<=}x{<=}0.3. Black-Right-Pointing-Pointer For x>0.3 a gradual transition from the C to the F structure is observed. Black-Right-Pointing-Pointer Lattice parameters do not follow Vegard's law.

  16. Crystalline Electric Field as a Probe for Long-Range Antiferromagnetic Order and Superconducting State of CeFeAsO1-xFx

    SciTech Connect (OSTI)

    Chi, Songxue; Adroja, D. T.; GUIDI, T.; Bewley, Robert I.; Li, Shiliang; Zhao, Jun; Lynn, J. W.; Brown, C. M.; Qiu, Y.; Chen, G. F,; Luo, J. L.; Wang, N. L.; Dai, Pengcheng

    2008-01-01

    We use inelastic neutron scattering to study the crystalline electric field (CEF) excitations of Ce{sup 3+} in CeFeAsO{sub 1-x}F{sub x} (x=0, 0.16). For nonsuperconducting CeFeAsO, the Ce CEF levels have three magnetic doublets in the paramagnetic state, but these doublets split into six singlets when the Fe ions order antiferromagnetically. For superconducting CeFeAsO{sub 0.84}F{sub 0.16} (T{sub c} = 41 K), where the static antiferromagnetic order is suppressed, the Ce CEF levels have three magnetic doublets at {h_bar}{sub {omega}} = 0, 18.7, 58.4 meV at all temperatures. Careful measurements of the intrinsic linewidth {Lambda} and the peak position of the 18.7 meV mode reveal a clear anomaly at T{sub c}, consistent with a strong enhancement of local magnetic susceptibility {chi}{double_prime}({h_bar}{sub {omega}}) below T{sub c}. These results suggest that CEF excitations in the rare-earth oxypnictides can be used as a probe of spin dynamics in the nearby FeAs planes.

  17. A ferromagnetic quantum critical point in heavy-fermion iron oxypnictide CeFe{sub 1?x}Cr{sub x}PO

    SciTech Connect (OSTI)

    Okano, T.; Matoba, M.; Kamihara, Y.; Kitao, S.; Seto, M.; Atou, T.; Itoh, M.

    2015-05-07

    We report crystallographic and magnetic properties of layered iron oxypnictide CeFe{sub 1?x}Cr{sub x}PO (x?=?0.0000.692). Interlayer distances between Ce{sub 2}O{sub 2} and (Fe{sub 1?x}Cr{sub x}){sub 2}P{sub 2} layers increase as a function of x, suggesting suppression of Kondo coupling among hybridized conducting orbitals and localized Ce 4f orbitals. CeFe{sub 1?x}Cr{sub x}PO (x?=?0.1000.384) exhibits finite ferromagnetic transition temperatures (T{sub curie}) obtained by Arrott plots, although {sup 57}Fe Mssbauer spectra reveal paramagnetic Fe sublattice at T???4.2?K. These results indicate that the ferromagnetic phase transitions of samples are mainly due to Ce sublattice. For the samples with x???0.500, no ferromagnetic order is observed down to 2?K. These results verify that ferromagnetic quantum critical points of CeFe{sub 1?x}Cr{sub x}PO appear at 0.045???x???0.100 and 0.384???x???0.500.

  18. Superior performance of Ni-W-Ce mixed-metal oxide catalysts for ethanol steam reforming: Synergistic effects of W- and Ni-dopants

    SciTech Connect (OSTI)

    Rodriguez, Jose A.; Liu, Zongyuan; Xu, Wenqian; Yao, Siyu; Johnson-Peck, Aaron C.; Zhao, Fuzhen; Michorczyk, Piotr; Kubacka, Anna; Stach, Eric A.; Fernandez-Garica, Marcos; Senanayake, Sanjaya D.

    2014-11-26

    The ethanol steam reforming (ESR) reaction was studied over a series of Ni-W-Ce oxide catalysts. The structures of the catalysts were characterized using in-situ techniques including X-ray diffraction, Pair Distribution Function, X-ray absorption fine structure and transmission electron microscopy; while possible surface intermediates for the ESR reaction were investigated by Diffuse Reflectance Infrared Fourier Transform Spectroscopy. In these materials, all the W and part of the Ni were incorporated into the CeO? lattice, with the remaining Ni forming highly dispersed nano NiO (< 2 nm) outside the Ni-W-Ce oxide structure. The nano NiO was reduced to Ni under ESR conditions. The Ni-W-Ce systeme exhibited a much larger lattice strain than those seen for Ni-Ce and W-Ce. Synergistic effects between Ni and W inside ceria produced a substantial amount of defects and O vacancies that led to high catalytic activity, selectivity and stability (i.e. resistance to coke formation) during ethanol steam reforming.

  19. Superior performance of Ni–W–Ce mixed-metal oxide catalysts for ethanol steam reforming: Synergistic effects of W- and Ni-dopants

    SciTech Connect (OSTI)

    Liu, Zongyuan; Xu, Wenqian; Yao, Siyu; Johnson-Peck, Aaron C.; Zhao, Fuzhen; Michorczyk, Piotr; Kubacka, Anna; Stach, Eric A.; Fernández-García, Marcos; Senanayake, Sanjaya D.; Rodriguez, José A.

    2014-11-26

    In this study, the ethanol steam reforming (ESR) reaction was examined over a series of Ni-W-Ce oxide catalysts. The structures of the catalysts were characterized using in-situ techniques including X-ray diffraction, Pair Distribution Function, X-ray absorption fine structure and transmission electron microscopy; while possible surface intermediates for the ESR reaction were investigated by Diffuse Reflectance Infrared Fourier Transform Spectroscopy. In these materials, all the W and part of the Ni were incorporated into the CeO₂ lattice, with the remaining Ni forming highly dispersed nano NiO (< 2 nm) outside the Ni-W-Ce oxide structure. The nano NiO was reduced to Ni under ESR conditions. The Ni-W-Ce systeme exhibited a much larger lattice strain than those seen for Ni-Ce and W-Ce. Synergistic effects between Ni and W inside ceria produced a substantial amount of defects and O vacancies that led to high catalytic activity, selectivity and stability (i.e. resistance to coke formation) during ethanol steam reforming.

  20. Superior performance of Ni–W–Ce mixed-metal oxide catalysts for ethanol steam reforming: Synergistic effects of W- and Ni-dopants

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

    Liu, Zongyuan; Xu, Wenqian; Yao, Siyu; Johnson-Peck, Aaron C.; Zhao, Fuzhen; Michorczyk, Piotr; Kubacka, Anna; Stach, Eric A.; Fernández-García, Marcos; Senanayake, Sanjaya D.; et al

    2014-11-26

    In this study, the ethanol steam reforming (ESR) reaction was examined over a series of Ni-W-Ce oxide catalysts. The structures of the catalysts were characterized using in-situ techniques including X-ray diffraction, Pair Distribution Function, X-ray absorption fine structure and transmission electron microscopy; while possible surface intermediates for the ESR reaction were investigated by Diffuse Reflectance Infrared Fourier Transform Spectroscopy. In these materials, all the W and part of the Ni were incorporated into the CeO₂ lattice, with the remaining Ni forming highly dispersed nano NiO (< 2 nm) outside the Ni-W-Ce oxide structure. The nano NiO was reduced to Nimore » under ESR conditions. The Ni-W-Ce systeme exhibited a much larger lattice strain than those seen for Ni-Ce and W-Ce. Synergistic effects between Ni and W inside ceria produced a substantial amount of defects and O vacancies that led to high catalytic activity, selectivity and stability (i.e. resistance to coke formation) during ethanol steam reforming.« less

  1. Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+}: A novel blue emitting phosphor for white LEDs

    SciTech Connect (OSTI)

    Li, Panlai Wang, Zhijun Yang, Zhiping; Guo, Qinglin

    2014-12-15

    Graphical abstract: Under the 350 nm radiation excitation, Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} has a broad blue emission band. When the temperature turned up to 150 C, the emission intensity of Ba{sub 1.97}B{sub 2}O{sub 5}:0.03Ce{sup 3+} is 63.4% of the initial value at room temperature. The activation energy ?E is calculated to be 0.25 eV, which prove the good thermal stability of Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+}. All the properties indicate that Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} may have potential application in white LEDs. - Highlights: Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} has a broad blue emission band under the 350 nm radiation excitation. Emission intensity of Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} is 63.4% (150 C) of the initial value (30 C). The activation energy ?E for thermal quenching is 0.25 eV. - Abstract: A novel blue emitting phosphor Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} is synthesized by a high temperature solid state method. The luminescent property and the thermal stability of Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} are investigated. Under the 350 nm radiation excitation, Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} has a broad blue emission band, and the peak locates at 417 nm which is assigned to the 5d{sup 1}4f{sup 1} transition of Ce{sup 3+}. It is further proved that the dipoledipole interaction results in the concentration quenching of Ce{sup 3+} in Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+}. When the temperature turned up to 150 C, the emission intensity of Ba{sub 1.97}B{sub 2}O{sub 5}:0.03Ce{sup 3+} is 63.4% of the initial value at room temperature. The activation energy ?E is calculated to be 0.25 eV, which prove the good thermal stability of Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+}. All the properties indicate that Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} may have potential application in white LEDs.

  2. Hierarchical Heterogeneity at the CeO x –TiO 2 Interface: Electronic and Geometric Structural Influence on the Photocatalytic Activity of Oxide on Oxide Nanostructures

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

    Luo, Si; Nguyen-Phan, Thuy-Duong; Johnston-Peck, Aaron C.; Barrio, Laura; Sallis, Shawn; Arena, Dario A.; Kundu, Shankhamala; Xu, Wenqian; Piper, Louis F. J.; Stach, Eric A.; et al

    2015-01-13

    Mixed oxide interfaces are critical for delivering active components of demanding catalytic processes such as the photo-catalytic splitting of water. We have studied CeOxTiO₂ catalysts with low ceria loadings of 1 wt%, 3 wt% and 6 wt% that were prepared with wet impregnation methods to favor a strong interaction between CeOx and TiO₂. In these materials the interfaces between CeOx-TiO₂ have been sequentially loaded (1%, 3% and 6%), with and without Pt (0.5 wt%). The structure and properties of the catalysts were characterized using several X-ray and electron based techniques including XRD, XPS, UPS, NEXAFS, UV-Vis and HR-STEM/STEM-EELS, to unravelmore » the local morphology, bulk structure, surface states and electronic structure. The combination of all these techniques allow us to analyze in a systematic way the complete structural and electronic properties that prevail at the CeOx-TiO₂ interface. Fluorite structured nano crystallites of ceria on anatase-structured titania were identified by both XRD and NEXAFS. A sequential increasing of the CeOx loading led to the formation of clusters, then plates and finally nano particles in a hierarchical manner on the TiO₂ support. The electronic structures of these catalysts indicate that the interaction between TiO₂ and CeO₂ is closely related to the local morphology of nanostructured CeO₂. Ce³⁺ cations were detected at the surface of CeO₂ and at the interface of the two oxides. In addition, the titania is perturbed by the interaction with ceria and also with Pt. The photocatalytic activity for the splitting of H₂O using UV light was measured for these materials and correlated with our understanding of the electronic and structural properties. Optimal catalytic performance and photo response results were found for the 1 wt% CeOx-TiO₂ catalyst where low dimensional geometry of the ceria provided ideal electronic and geometrical properties. The structural and electronic properties of the interface

  3. Hierarchical heterogeneity at the CeOx-TiO? interface: Electronic and geometric structural influence on the photocatalytic activity of oxide on oxide nanostructures

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

    None

    2015-01-13

    Mixed oxide interfaces are critical for delivering active components of demanding catalytic processes such as the photo-catalytic splitting of water. We have studied CeOxTiO? catalysts with low ceria loadings of 1 wt%, 3 wt% and 6 wt% that were prepared with wet impregnation methods to favor a strong interaction between CeOx and TiO?. In these materials the interfaces between CeOx-TiO? have been sequentially loaded (1%, 3% and 6%), with and without Pt (0.5 wt%). The structure and properties of the catalysts were characterized using several X-ray and electron based techniques including XRD, XPS, UPS, NEXAFS, UV-Vis and HR-STEM/STEM-EELS, to unravelmorethe local morphology, bulk structure, surface states and electronic structure. The combination of all these techniques allow us to analyze in a systematic way the complete structural and electronic properties that prevail at the CeOx-TiO? interface. Fluorite structured nano crystallites of ceria on anatase-structured titania were identified by both XRD and NEXAFS. A sequential increasing of the CeOx loading led to the formation of clusters, then plates and finally nano particles in a hierarchical manner on the TiO? support. The electronic structures of these catalysts indicate that the interaction between TiO? and CeO? is closely related to the local morphology of nanostructured CeO?. Ce? cations were detected at the surface of CeO? and at the interface of the two oxides. In addition, the titania is perturbed by the interaction with ceria and also with Pt. The photocatalytic activity for the splitting of H?O using UV light was measured for these materials and correlated with our understanding of the electronic and structural properties. Optimal catalytic performance and photo response results were found for the 1 wt% CeOx-TiO? catalyst where low dimensional geometry of the ceria provided ideal electronic and geometrical properties. The structural and electronic properties of the interface were critical for the

  4. HL Power Geothermal Facility | Open Energy Information

    Open Energy Info (EERE)

    processes (afday) Daily Operation Water Use (afday) Well Field Water Use (afday) Cooling Tower Water use (annual average) (afday) Cooling Tower Water use (summer average) (af...

  5. HL Power Company | Open Energy Information

    Open Energy Info (EERE)

    Sector: Biomass Product: A power company located in California, the company main focus of energy is directed to biomass production. Coordinates: 40.293339, -79.687036...

  6. Heavy fermion Ce{sub 3}Co{sub 4}Sn{sub 13} compound under pressure

    SciTech Connect (OSTI)

    Collave, J. R.; Borges, H. A.; Ramos, S. M.; Hering, E. N.; Mendona-Ferreira, L.; Pagliuso, P. G.

    2015-05-07

    The non-magnetic heavy fermion compound Ce{sub 3}Co{sub 4}Sn{sub 13} was studied under pressure. We report single crystalline measurements of electrical resistivity as a function of temperature ?(T) under pressure. Some characteristic features related to a structural transition (T{sub S}), crystalline field effects (T{sub CEF}), and a low temperature maximum (T{sub max}), possibly connected simultaneously to the onset of Kondo lattice coherence and short range magnetic correlations, were identified in the ?(T) data. A pressure-temperature phase diagram with T{sub S} and T{sub max} was constructed by mapping these features. Like for most Ce-based heavy fermion compounds, T{sub max} moves to higher temperatures with pressure, indicating that it is related to the Kondo energy scale, due to the increase of hybridization induced by pressure. On the other hand, T{sub S}, associated to a superlattice distortion and probably combined with a charge density wave transition, decreases as a function of pressure. However, differently from the Sr{sub 3?x}Ca{sub x}Ir{sub 4}Sn{sub 13} system, where a superlattice quantum phase transition is observed [L. E. Klintberg et al., Phys. Rev. Lett. 109, 237?008 (2012)], in Ce{sub 3}Co{sub 4}Sn{sub 13} T{sub S}???154?K, at ambient pressure (P?=?0), seems to stabilize at around 143?K for P???19 kilobars. We also investigated ?(T) in external magnetic fields, at P?=?0. Negative magnetoresistance and increase of T{sub max} are observed, suggesting suppression of low temperature short range magnetic correlations.

  7. Comparative Gamma Spectroscopy with SrI2(Eu), GYGAG(Ce) and Bi-loaded Plastic Scintillators

    SciTech Connect (OSTI)

    Cherepy, N J

    2010-11-19

    We are developing new scintillator materials that offer potential for high resolution gamma ray spectroscopy at low cost. Single crystal SrI{sub 2}(Eu) offers {approx}3% resolution at 662 keV, in sizes of {approx}1 in{sup 3}. We have developed ceramics processing technology allowing us to achieve cubic inch scale transparent ceramic scintillators offering gamma spectroscopy performance superior to NaI(Tl). We fabricated a bismuth-loaded plastic scintillator that demonstrates energy resolution of {approx}8% at 662 keV in small sizes. Gamma ray spectroscopy can be used to identify the presence of weak radioactive sources within natural background. The ability to discriminate close-lying spectral lines is strongly dependent upon the energy resolution of the detector. In addition to excellent energy resolution, large volume detectors are needed to acquire sufficient events, for example, to identify a radioactive anomaly moving past a detector. We have employed a 'directed search' methodology for identifying potential scintillator materials candidates, resulting in the discovery of Europium-doped Strontium Iodide, SrI{sub 2}(Eu), Cerium-doped Gadolinium Garnet, GYGAG(Ce), and Bismuth-loaded Polymers. These scintillators possess very low self-radioactivity, offer energy resolution of 3-8% at 662 keV, and have potential to be grown cost-effectively to sizes similar to the most widely deployed gamma spectroscopy scintillator, Thallium-doped Sodium Iodide, NaI(Tl). In this study, gamma ray spectra of a variety of sources, were obtained employing SrI{sub 2}(Eu), GYGAG(Ce), Bi-loaded polymers, LaBr{sub 3}(Ce), and NaI(Tl). The effects of detector size, energy resolution, and background radioactivity (including self-radioactivity) on the ability to distinguish weak sources is quantified, based on a simple model, and qualitatively compared to laboratory data.

  8. Synthesis of mesoporous Bi{sub 2}O{sub 3}/CeO{sub 2} microsphere for photocatalytic degradation of Orange II dye

    SciTech Connect (OSTI)

    Hsieh, Shu-Han; Manivel, Arumugam; Lee, Gang-Juan; Wu, Jerry J.

    2013-10-15

    Graphical abstract: - Highlights: • Bi{sub 2}O{sub 3}/CeO{sub 2} microspheres were successfully synthesized by a hydrothermal procedure. • Bi{sub 2}O{sub 3}/CeO{sub 2} microspheres were used to remove wastewater pollutant containing azo dye. • The activity of Bi{sub 2}O{sub 3}/CeO{sub 2} is synergically enhanced compared to its pristine forms. - Abstract: We report on the visible-light responsive porous assembly of Bi{sub 2}O{sub 3}/CeO{sub 2} microspheres, which were synthesized via a simple hydrothermal reaction between Bi(NO{sub 3}){sub 3}·5H{sub 2}O and Ce(NO{sub 3}){sub 3}·6H{sub 2}O in the presence of ethylene glycol and ethanol. Systematic structural (X-ray diffraction (XRD)), morphological (field emission scanning electron microscopy (FE-SEM) and transmission electron microscopic (TEM)), BET surface area and diffuse reflectance spectral (DRS) analyses were carried out to characterize the formed product. The effects of experimental parameters on the microstructural and morphological behavior of Bi{sub 2}O{sub 3}/CeO{sub 2} composites were discussed. The semiconductor material as obtained was evaluated as a heterogeneous photocatalyst for the photolytic degradation of an azo dye in water and the degradation was found to follow pseudo-first-order rate kinetics. The study compares the rate constants of the new hybrid catalyst to a pristine Bi{sub 2}O{sub 3} and CeO{sub 2}, which has excellent catalytic properties under visible light irradiation for the degradation of Orange II dye.

  9. Fabrication and microstructure of cerium doped lutetium aluminum garnet (Ce:LuAG) transparent ceramics by solid-state reaction method

    SciTech Connect (OSTI)

    Li, Junlang; Xu, Jian; Shi, Ying; Qi, Hongfang; Xie, Jianjun; Lei, Fang

    2014-07-01

    Highlights: We fabricate Ce doped lutetium aluminum garnet ceramics by solid-state method. The raw materials include Lu{sub 2}O{sub 3} nanopowders synthesized by co-precipitation method. The density of the transparent ceramics reach 99.7% of the theoretical value. The optical transmittance of the bulk ceramic at 550 nm was 57.48%. Some scattering centers decrease the optical characteristic of the ceramic. - Abstract: Polycrystalline Ce{sup 3+} doped lutetium aluminum garnet (Ce:LuAG) transparent ceramics fabricated by one step solid-state reaction method using synthetic nano-sized Lu{sub 2}O{sub 3}, commercial ?-Al{sub 2}O{sub 3} and CeO{sub 2} powders were investigated in this paper. The green compacts shaped by the mixed powders were successfully densified into Ce:LuAG transparent ceramics after vacuum sintering at 1750 C for 10 h. The in-line optical transmittance of the Ce:LuAG ceramic made by home-made Lu{sub 2}O{sub 3} powders could reach 57.48% at 550 nm, which was higher than that of the ceramic made by commercial Lu{sub 2}O{sub 3} powders (22.96%). The microstructure observation showed that light scattering centers caused by micro-pores, aluminum segregation and refraction index inhomogeneities induced the decrease of optical transparency of the Ce:LuAG ceramics, which should be removed and optimized in the future work.

  10. Effect of magnetic fields on the Kondo insulator CeRhSb: Magnetoresistance and high-field heat capacity measurements

    SciTech Connect (OSTI)

    Malik, S.K.; Menon, L.; Pecharsky, V.K.; Gschneidner, K.A. Jr.

    1997-05-01

    The compound CeRhSb is a mixed valent Ce-based compound which shows a gap in the electronic density of states at low temperatures. The gap manifests by a rise in electrical resistivity{emdash}below about 8 K from which the gap energy is estimated to be about 4 K. We have carried out heat capacity measurements on this compound in various applied fields up to 9.85 T. The magnetic contribution to the heat capacity, {Delta}C, is found to have a maximum in {Delta}C/T vs T at 10 K, below which {Delta}C/T is linear with T. This is attributed to the fact that below this temperature, in the gapped state, the electronic density of states decreases linearly with decreasing temperature. On application of a magnetic field, the electronic specific heat coefficient {gamma} in the gapped state increases by {approximately}4mJ/molK{sup 2}. The maximum in {Delta}C/T vs T is observed in all fields, which shifts to lower temperatures {approximately}1K at 5.32 T and raises again at 9.85 T to about the same values as at H=0T. This suggests that the gap exists for all fields up to 9.85 T. Above 10 K, in the mixed-valent state, {Delta}C/T vs T decreases with increasing temperature in zero field. There is hardly any effect of application of field in the mixed-valent state. We have also carried out magnetoresistance measurements on CeRhSb up to fields of 5.5 T at 2, 4.5, 10, 20, and 30 K. The magnetoresistance in CeRhSb is positive at temperatures of 4.5 K and above, in applied fields up to 5.5 T. At 5.5 T, the magnetoresistance is maximum at 4.5 K (6{percent}) and decreases with increasing temperature. The observation of the maximum is consistent with the observation of a maximum in {Delta}C/T vs T and is due to a change in the density of states. At a temperature of 2 K, a negative magnetoresistance is observed for magnetic fields greater than {approximately}3.5T which suggests reduction in the gap. {copyright} {ital 1997} {ital The American Physical Society}