22 Search Results

Nickel-rich single-crystal (SC) layered oxides are promising cathode candidates for next-generation lithium-ion batteries (LIBs) owing to their high energy density and structural robustness against intergranular cracking. However, their intrinsic surface reactivity with liquid electrolytes accelerates parasitic reactions at the cathode–electrolyte interphase (CEI), leading to transition-metal dissolution, gas generation, and impedance buildup. In this work, we synthesized SC-Li_xNi_0.9Mn_0.05Co_0.05O₂ (NMC9055, 1 ≤ x ≤ 1.2) using a eutectic-assisted method and investigated interface stabilization strategies. A nickel-deficient Li_xNi_0.6Mn_0.2Co_0.2O₂ (NMC622, 1 ≤ x ≤ 1.2) coating was applied via evaporation-based deposition to suppress CEI degradation pathways. Structural and compositional analyses confirmed uniform shell formationmore » and preserved particle integrity. Half-cell electrochemical testing against lithium metal revealed ∼10% higher capacity retention and improved reversibility compared with pristine SC NMC9055, particularly under high-voltage operation. In conclusion, these results highlight the critical role of controlled surface chemistry in mitigating CEI instability in nickel-rich SC cathodes, offering a pathway toward enabling durable high-energy LIBs.« less

Deep eutectic solvents (DESs) are a class of liquids that offer great potential in alleviating some of the challenges present in today's long-term energy storage methods because they have physical properties that are favorable for storable electrolyte solutions. In this work, a series of glycols (ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol) were studied as potential hydrogen bond donors (HBD) with a common choline chloride (ChCl) as the hydrogen bond acceptor (HBA). The solvation dynamics of the prepared systems were studied by measuring the solvent reorganization response using femtosecond transient absorption spectroscopy (fs-TA). Conductivity, viscosity, density, ET(30) polarity, and dynamics ofmore » the prepared DESs were analyzed, with a particular interest in determining the effect of HBD chain length on these parameters. Here, classical molecular dynamics simulations were employed to investigate how the local liquid structure, solvent dynamics, and bulk solvent properties vary with changes in glycol chain length.« less

Ensuring nonproliferation and safeguards of special nuclear materials (SNM) is a critical aspect of advancing the nuclear fuel cycle. Traditional bubbler systems used to estimate liquid levels and densities in nuclear recycling processes have limitations, particularly in harsh environments where dip-tube corrosion and buildup necessitate frequent maintenance and recalibration. This study explores the Dynamic Single Bubbler (DSB) method, which utilizes a single dip-tube attached to a linear actuator to estimate liquid properties dynamically. This approach is extended to estimate liquid-liquid interfaces in immiscible liquids and employs a linear regression method to reduce uncertainties and improve accuracy. The DSB method achievedmore » density estimate uncertainties of less than 0.5% and surface level estimate uncertainties typically under 0.5%, across various fluids including water, acetone, methanol, mineral oil, glycerol, and aqueous salt solutions. Results indicate that the DSB method provides accurate and robust estimates of liquid density and surface levels with minimal maintenance and without the need for calibration. Additionally, the method's applicability to immiscible liquids and various dip-tube geometries was demonstrated, showing promise for widespread use in nuclear and other industrial applications.« less

Ammonia is a promising alternative to hydrogen with high energy density and favorable storage and transport characteristics. However, low flammability and a propensity for high nitrogen oxide (NO_x) emissions make direct utilization challenging. Recently, two-stage rich-quench-lean (RQL) combustion strategies have shown promise in achieving low NO_x emissions with ammonia. In this approach, the rich stage serves to oxidize a portion of the fuel while thermally decomposing as much of the remaining ammonia as possible, generating hydrogen. In the second (lean) stage, air is rapidly introduced, burning out the hydrogen and residual ammonia. Two-stage RQL combustion of ammonia has been investigatedmore » in the open literature both experimentally and numerically. In general, idealized chemical reactor network (CRN) models predict NO_x concentrations below those of 2D/3D computational fluid dynamics models and experiments. The primary drivers of these discrepancies may be largely attributed to finite rate mixing nonadiabatic operation. The typical CRN model is comprised of a perfectly-stirred-reactor (PSR), followed by a plug-flow-reactor (PFR), meant to represent the flame, and postflame zones, respectively. In the two-stage RQL approach two PSR-PFR networks are arranged sequentially, corresponding to the rich and lean stages, with secondary air injection in between. In the authors' past work, this arrangement has demonstrated the significant sensitivity of exit NO_x to the rich stage equivalence ratio, while the amount of secondary air injection was shown to be less critical. In this paper, the CRN model is extended to (1) include the impacts of heat loss and (2) utilize a partially-stirred-reactor (PaSR) approach to study the impacts of mixing on emissions performance. Varying amounts of heat loss are applied to the rich relaxation zone to understand emissions performance and changes to optimization of equivalence ratio and residence time. Premixed and nonpremixed configurations are considered in the rich stage PaSR, with varying degrees of mixing intensity to study the interaction between mixing, transport, and kinetic timescales. Critically, the impact of mixing between hot products and secondary air injection is studied to understand practical injector needs. Results show unburnt ammonia leaving the rich stage as a primary contributor to NO_x emissions – driven both by increased heat loss and reduced mixing rates. Furthermore, heat losses have been shown to create conditions that are conducive to increased N₂O formation in the lean stage. In conclusion, the results of this study will be considered in the context of developing optimized two-stage RQL combustors for ammonia.« less

PBX 9502 is an insensitive high explosive (HE) containing 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) as the HE crystal bonded with the copolymer Kel F-800 in a nominal weight ratio of 95% TATB and 5% Kel F-800. Multiple batches, known as lots, of PBX 9502 have been manufactured since its introduction. The detonation diameter effect, which measures steady detonation speed versus inverse charge radius in a cylindrical rate-stick configuration, varies significantly between the different lots. Here, we show that the diameter effect variation can be explained by differences in the initial pressing density, weight percentage of TATB, and percentage of TATB that is virginmore » or recycled in each lot (recycled lots have a larger weight percentage of fine TATB particles than virgin lots). Incorporating these properties into a detonation shock dynamics model, we show that the diameter effect data for the lots examined collapse onto a single curve at a given reference state. PBX 9502 is an important TATB-based insensitive high explosive, which has been extensively studied due to its unique combination of safety and performance properties. Since its introduction, multiple batches of PBX 9502, known as lots, have been manufactured. PBX 9502 shows significant lot-to-lot variations in detonation speed that have not been satisfactorily explained. In this work, we show that the variations are due to a combination of differences in pressing density, weight percentage of TATB, and weight percentage of fine TATB particles. The work provides a new capability for how detonation propagation in PBX 9502 can be modeled without extensive experimentation.« less

Pressure-density-temperature ($${{p}}$$-$${{\rho}}$$-$${{T}}$$) data for the refrigerant R-1130(E) (trans-1,2-dichloroethene) were measured in the compressed liquid phase using an automated vibrating-tube densimeter. Overall, the measurements covered temperatures from 270 K to 410 K and pressures from 0.5 MPa to 30 MPa. Relative combined, expanded (95% confidence level) uncertainties ranged from approximately 0.05% to 0.06%. Here, we present measurement results, along with comparisons to available literature data and to a generalized extended corresponding states model.

ZrO₂ and CeO₂ films were grown in SBA-15 by Atomic Layer Deposition (ALD) to loadings of 0.92 g oxide/g SBA-15. Scanning Transmission Electron Microscopy (STEM) with Energy Dispersive Spectra (EDS) showed that the oxides grew uniformly inside the mesopores. Film thicknesses were then analyzed as a function of the number of ALD cycles using three methods: 1) mass changes assuming bulk densities for the films; 2) changes in pore size from Barret-Joyner-Halenda (BJH) analysis with N₂ adsorption isotherms; and 3) small-angle X-ray scattering (SAXS). Film thicknesses assuming bulk densities were between 6 and 8 times smaller than those obtained frommore » BJH analysis. SAXS analysis gave film thicknesses that were approximately twice that obtained from bulk densities. Here, possible explanations of the discrepancies between these methods are discussed.« less

The pressure vessels needed to store hydrogen for next-generation hydrogen fuel cell vehicles are expected to be a substantial portion of the total system mass, volume, and cost. Gravimetric capacity, volumetric capacity, and cost per kilogram of usable hydrogen are key performance metrics that the U.S. Department of Energy (DOE) uses to determine the viability of hydrogen fuel cell systems. Research and development related to hydrogen storage systems covers a wide range of potential operating conditions, from cryogenic temperatures to high temperatures (above ambient) and low pressure to high pressure. Researchers at PNNL have developed methods for estimating these keymore » pressure vessel characteristics to support on-board hydrogen storage system design and performance evaluation and to support decision-making about DOE hydrogen storage system research investments. This article describes the pressure tank estimation methodology that has been used as a stand-alone calculation and has been incorporated into larger system evaluation tools. The methodology estimates the geometry, mass, and material cost of type I, type III, and type IV pressure vessels based on operating pressure and material strength at the system's operating temperature, using classical thin-wall and thick-wall pressure vessel stress calculations. The geometry, mass, and material cost requirements of the pressure vessel have significant impacts on the total system performance. For example, hydrogen storage materials that can separately achieve a very high hydrogen density can be deemed impractical for use in fuel cell vehicle hydrogen storage systems because the pressure tank containing them is too large, heavy, or expensive. This article describes the design philosophy and analytical process of the tank characteristic estimation methodology, which has been implemented in spreadsheet calculation tools and system-level analysis tools used by DOE researchers. Each of the three tank types (type I, type III, and type IV) uses a different analysis methodology with some common elements. This article also provides examples of implementing the methodology to perform parametric studies of all three pressure vessel types. The goal of this article is to present the methodology in sufficient detail so it can be implemented in other hydrogen fuel cell vehicle design and analysis tools.« less

A second-harmonic, dispersion interferometer is used to image large-area (≃5 cm²) plasma-jet and gas-jet density profiles. Achromatic telescopes magnify the diameters of the primary-laser beam (1064 nm) and its second-harmonic (532 nm) before probing the sample and de-magnify the beam diameters after the sample, where the primary beam transfers its phase change to a second, second-harmonic beam, allowing the sample’s dispersive-phase change to be measured between two, orthogonally polarized second harmonic beams. The telescopes produce an azimuthally symmetric, dispersive-phase shift in the sample + background phase-change image and in the background phase-change image, which is removed by digital subtraction. Themore » interferometer’s performance was verified using standard-optical components as dispersive elements (BK7 lenses and wedge plates), resolving a minimum, phase-change sensitivity of ΔΦ_min ≳ 15 mrad and spatial resolution of Δx_res ≃ 100 μm. The phase change produced by unknown-density objects (a pulsed-plasma-jet and a pulsed-gas-jet) was measured, and their data were used to recover the original, 2D density profiles using an inverse Abel transform: peak-number density, N_gas ≃ 6 × 10²⁰ cm^–3 and N_e ≃ 5 × 10¹⁶ cm^–3; line-integrated density, ∫N_gasdl ~ 2 × 10¹⁹cm^–2 and ∫N_edl ~ 1 × 10¹⁶cm^–2. The techniques and methods developed here are scalable to even larger probe-beam diameters and frame-capture rates, leading to a diagnostic capability that is well-suited for applications involving the real-time measurement of density.« less

The compound energy formalism (CEF) is a powerful framework to describe the thermodynamics of metal oxides as a function of off-stoichiometry, temperature, and composition. The thermodynamic properties are crucial materials design attributes in metal oxide-based oxygen-exchange chemical processes. Despite the richness of information an accurate CEF model provides, a method to determine a unique and accurate fit for oxygen exchange materials remains elusive. This contribution details a method for fitting the CEF model that overcomes the current fitting challenges through three innovations: 1) the combination of density functional theory calculations with experimental data decorrelates excess terms and delineates the enthalpic/entropicmore » contributions to the Gibbs free energy; 2) a systematic determination of the important CEF model terms, removing thermodynamic predetermining human intervention; 3) a self-consistent solution of the starting oxygen offstoichiometry (δ₀) of thermogravimetric measurements. Thus, our method enables the reliable extraction of off-stoichiometric metal oxide thermodynamic properties and facilitates rapid materials compositional screening, and reliable process design of systems dependent on off-stoichiometric redox-active metal oxides. We apply this method to a Ba_xSr_1-xFeO_3-δ test case. We find by systematically examining the performance of the CEF model fit with and without each innovation that all three innovations are necessary for an accurate fit. We determined that reduction enthalpy is higher and more sensitive to off-stoichiometry when the Sr fraction is large (139.5 and 185.3 kJ/mol O₂ for SrFeO₃ at δ = 0 and δ = 0.5, respectively vs. nearly constant 83 kJ/mol O₂ for BaFeO₃). However, the reduction entropy is mostly insensitive to Sr fraction, but highly dependent on δ suggesting larger contributions in the non-configurational entropy parameters.« less