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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Boron Nitride Solid-State Neutron Detectors

The goal of this project is to build upon the work performed under the Texas Tech IDEAS project (DE-AR0000964 monitored by Dr. Isik Kizilyalli) to bring the developed B-10 enriched hexagonal boron nitride (h- 10 BN or 10 BN or BN) semiconductor neutron detector technology to the next level of maturity. In comparison to He-3 ( 3 He) gas detectors, BN neutron detectors possess all the intrinsic advantages of semiconductor devices: light weight, compact size, fast response speed, high spatial resolution, high temperature and low voltage operation capability, ease of mass production via existing semiconductor infrastructures, low cost of operation and maintenance, flexible form factors, and durability. The project will develop a prototype h- 10 BN neutron detector as a potential replacement for the 3 He gas neutron detectors (LND 25185 or equivalent) used in various neutron survey meters currently produced and commercialized by Ludlum Measurements, Inc. (LMI). To increase the overall detection efficiency, it is essential to maximize the collection efficiency of charge carriers (electrons and holes) generated by the nuclear reaction, which demands a further push to achieve 10 BN epilayers with improved material quality. The material growth processes will be guided by characterization of structural, optical, and electrical properties of h-BN. Selective devices will be calibrated at LMI. During ARPA-E supporting period, the key material parameters of h-BN produced by metal organic chemical vapor deposition (MOCVD), including the layer thickness, mobility-lifetime product, surface recombination field and detector size for maintaining a high charge collection efficiency all have been improved by several orders of magnitude. These improvements have enabled the realization of high-performance h 10BN semiconductor thermal neutron detectors. Presently, h- 10 BN thermal neutron detectors developed under ARPA-E’s support hold the record high detection efficiency among all solid-state detectors at 59%. With further development in manufacturing, there is no question that h-BN detectors will replace the traditional He-3 gas detectors in certain application areas by offering obvious advantages of semiconductor technologies over gas detectors and opportunities for users to dedicate the scarce and expensive supply of He-3 gas to other application areas where substitutes of He-3 gas are not possible.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Design and Characterization of ALD-Based Overcoats for Supported Metal Nanoparticle Catalysts

Supported metal nanoparticle (SMN) catalysts are enormously crucial for many catalytic applications. However, catalyst deactivation, caused by sintering and coke formation, is a ubiquitous problem that significantly undermines catalytic processing economics. The application of material overcoating onto supported metal nanoparticles by atomic layer deposition (ALD) offers the solution to inhibit catalyst deactivation. Herein, we discuss examples in which ALD has been used to stabilize SMN catalysts in gaseous and aqueous-phase reactions. We highlight the ALD tools and methods in coating high-surface-area catalysts. Besides, various techniques are introduced to understand better how to characterize the overcoating layer and the catalyst itself. Finally, the outlook for new techniques to characterize the ALD overcoated catalytic materials is discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

A Case Study of the Weather Research and Forecasting Model Applied to the Joint Urban 2003 Tracer Field Experiment. Part III: Boundary-Layer Parametrizations

Numerical weather prediction is often used to supply the mean wind and turbulence fields for atmospheric transport and dispersion plume models as they provide dense geographic coverage in comparison to typically sparse monitoring networks. Here, the Weather Research and Forecasting (WRF) model 4.0 was run over the month-long period of the Joint Urban 2003 field campaign conducted in Oklahoma City. We compare three different simulations in their ability to reproduce the observations, each using a different boundary-layer parametrization. Specifically, we examine the Mellor–Yamada–Janjic (MYJ), Yonsei University (YSU), and Mellor–Yamada–Nakanishi–Niino (MYNN) boundary-layer parametrizations. All three predict the wind speed well during the day but overpredict it at night. The MYNN parametrization is better than MYJ at predicting the daytime turbulence in the surface layer, but both underpredict the nocturnal turbulence. Additionally, the MYJ parametrization is best at predicting the reciprocal Obukhov length, while MYNN and YSU both significantly overpredict thermal stability. Reconstructing the reciprocal Obukhov length from other simulated parameters produces more accurate values for both parametrizations. All three models overpredict the boundary-layer height, particularly under convective conditions. The MYJ parametrization overestimates boundary-layer height the most, while YSU and MYNN have comparable performance with MYNN having an advantage in predicting the stable boundary-layer height. Several days were found where the WRF simulations predict significant deviations from the prevailing diurnal pattern in wind direction, which are not found in the observations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Detection of Extreme Phenomena in the Stable Boundary Layer over the Amazonian Forest

We apply different methods for detection of extreme phenomena (EP) in air-turbulent time series measured in the nocturnal boundary layer above the Amazon forest. The methods used were: (a) a Morlet complex wavelet transform, which is often used in analysis of non-linear application processes. Through the use of the wavelet, it is possible to observe a phase singularity that involves a strong interaction between an extensive range of scales; (b) recurrence plot tests, which were used to identify a sudden change between different stable atmospheric states. (c) statistical analysis of early-warning signals, which verify simultaneous increases in the autocorrelation function and in the variance in the state variable; and (d) analysis of wind speed versus turbulent kinetic energy to identify different turbulent regimes in the stable boundary layer. We found it is adequate to use a threshold to classify the cases of strong turbulence regime, as a result of the occurrence of EP in the tropical atmosphere. All methods used corroborate and indicate synergy between events that culminate in what we classify as EP of the stable boundary layer above the tropical forest.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Quasi-Two-Dimensional Heterostructures (K M 1 – x Te)(LaTe 3 ) ( M = Mn and Zn) with Charge Density Waves

Layered heterostructure materials with two different functional building blocks can teach us about emergent physical properties and phenomena arising from interactions between the layers. Here, we report intergrowth compounds KLaM 1 - x Te 4 (M = Mn and Zn; $x \approx$ 0.35) featuring two chemically distinct alternating layers [LaTe 3 ] and [KM 1 - x Te]. Their crystal structures are incommensurate, determined by single X-ray diffraction for the Mn compound and a transmission electron microscope study for the Zn compound. KLaMn 1 – x Te 4 crystallizes in the orthorhombic superspace group Pmnm(01/2 gamma)s00 with lattice parameters a = 4.4815(3) Å, b = 21.6649(16) Å, and c = 4.5220(3) Å. It exhibits charge density wave order at room temperature with a modulation wave vector q = 1/2b* + 0.3478c* originating from electronic instability of Te-square nets in [LaTe 3 ] layers. The Mn analog exhibits a cluster spin glass behavior with spin freezing temperature $T_f \approx$ 5 K attributed to disordered Mn vacancies and competing magnetic interactions in the [Mn 1 - x Te] layers. The Zn analog also has charge density wave order at room temperature with a similar q-vector having the c* component similar to 0.346 confirmed by selected-area electron diffraction. Electron transfer from [KM 1 - x Te] to [LaTe 3 ] layers exists in KLaM 1 – x Te 4 , leading to an enhanced electronic specific heat coefficient. The resistivities of KLaM 1 - x Te 4 (M = Mn and Zn) exhibit metallic behavior at high temperatures and an upturn at low temperatures, suggesting partial localization of carriers in the [LaTe 3 ] layers with some degree of disorder associated with the M atom vacancies in the [M 1 - x Te] layers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Absolute mass calibration of fission product distributions measured with the E-$v$ method

The mass calibration of fission product distributions measured with the energy–velocity (E-v) method constitutes a technical challenge. The energy loss of the fission fragments in the various dead layers of the spectrometer and other sources of pulse-height defects of the energy detectors are a significant source of systematic uncertainty in the mass calculations used to determine the measured fission product yields. Here, in this study, the absolute calibration of the fission mass distributions is accomplished by measuring prompt γ-rays in coincidence with the fission fragments. This allows for the direct calibration of the mass spectra and eliminates any dependence on potentially complicated energy corrections. The first test measurement was performed at the Los Alamos Neutron Science Center employing the SPectrometer for Ion DEtermination in fission Research (SPIDER). SPIDER is a 2E-2v spectrometer designed for measuring independent fission product yields from neutron-induced fission. In this test, the single-arm SPIDER (E-v) system and an array of 252 Cf sources were used. The single-arm system consisted of two time pick-off detectors for measuring the time-of-flight of the fission fragments and a double-sided silicon strip detector (DSSD) for measuring the kinetic energy. Characteristic γ-rays from fission fragments were detected using three high-purity germanium (HPGe) detectors. For the mass calibration, γ–mass coincidence events from twelve product isotopes were used. The measured FPYs from 252 Cf spontaneous fission were found to be in excellent agreement with the evaluated data after applying the absolute mass calibration. From the γ–mass coincidence events, the mass resolution of the system was also extracted. An average mass resolution of ~1.4 AMU (FWHM) for the light fragments and ~2.4 AMU (FWHM) for the heavy fragments were found. This was the first in-situ calibration and characterization of the SPIDER spectrometer, which paves the way for high-quality FPY measurements with this instrument.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Staircase formation by resonant and non-resonant transport of potential vorticity

The E × B staircase is a quasi-periodic pattern of pressure profile corrugations. In this work, we present a new mechanism for E × B staircase formation that involves resonant transport versus non-resonant transport. We start from a potential vorticity evolution system and use quasi-linear theory, a model dispersion relation, and a bi-Lorentzian spectrum approximation, to construct the relation between the fluxes and the profiles. With these fluxes, we close the profile evolution equations and the extended turbulence intensity evolution equation, which together constitute a turbulence-profile evolution system. In this system, the Doppler effect from the E × B mean flow can cause resonance between trapped ion precession motion and the trapped ion mode, which drives a resonant transport contribution to the fluxes. The profiles will be flattened where the resonant transport is switched on. In contrast, for the regions of non-resonant transport, profiles are steeper. A quasi-periodic pattern of profile corrugation (the E × B staircase) spontaneously emerges in this system, which is the two states mentioned above, arranged as alternating layers in space. The feedback processes during the staircase pattern formation are identified. An estimate of the critical value of the boundary heat flux is obtained, above which the staircase formation will be triggered. An estimate scaling of the step size in the staircase pattern is obtained. The resonant turbulent transport is also a mechanism for collisionless saturation of zonal flow. Furthermore, this work is related to internal transport barrier formation and suggests some new scenarios, such as an enhanced confined L mode.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Fluorinated High-Voltage Electrolytes To Stabilize Nickel-Rich Lithium Batteries

As state-of-the-art (SOA) lithium-ion (Li-ion) batteries approach their specific energy limit (~250 Wh kg -1 ), layer-structured, nickel-rich (Ni-rich) lithium transition metal oxide-based cathode materials, e. g., LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811), have attracted great interest owing to their practical high specific capacities (>200 mAhg -1 ). Coupled with their high average discharge voltages (~4 V vs Li/Li + ), Ni-rich cathode-based lithium batteries possess a great potential to achieve much higher specific energies (>350 Wh kg -1 at the cell level) than the SOA Li-ion counterparts. In addition, Ni-rich oxides are low-cost battery cathode materials due to their low cobalt contents. However, Ni-rich cathode-based lithium batteries suffer quick capacity degradations upon cycling, particularly at high upper cutoff voltages (e.g., ≥= 4.5 V vs Li/Li + ), due to crystal structure changes of the active cathode materials and parasitic side reactions at the electrolyte/electrode interfaces. In this study, a fluorinated-solvent-based, high-voltage stable electrolyte (HVE), i.e., 1 M Li bis(trifluoromethanesulfonyl)imide (LiTFSI) in fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl) carbonate (FDEC), and methyl (2,2,2-trifluoroethyl) carbonate (FEMC) with Li difluoro(oxalate)borate (LiDFOB) additive, was formulated and evaluated in Li/NMC811 battery cells. Further, to the best of our knowledge, this class of electrolyte has not been investigated for Ni-rich cathode-based lithium batteries. Li/NMC811 cells with HVE exhibited a superior long-term cycle performance stability, maintaining ~80% capacity after ~500 cycles at a high cutoff voltage of 4.5 V (vs Li/Li + ) than a baseline carbonate-solvent-based electrolyte (BE). The superior cycle stability of the Li/NMC811 cells is attributed to the inherently high-voltage stability of HVE, supported by the physical and electrochemical analyses. This conclusion is supported by our density functional theory (DFT) modeling where HVE shows a less tendency of deprotonation/oxidation than BE, leading to the observed cycle stability. The findings in this study are important to help tackle the technical challenges facing Ni-rich cathode-based lithium batteries to realize their high energy density potentials with a long cycle life.

25 ENERGY STORAGE↗
DOE OSTI2024

Understanding the L-H isotope effect at the DIII-D tokamak and advancements in synthetic turbulence diagnostics

Abstract It is determined that while heat flux differences between hydrogen and deuterium isotope experiments result from natural differences in carbon impurity content at DIII-D, it is not the origin of the low to high confinement mode (L-H) transition isotope effect. More specifically, a two times larger edge radial electric field in hydrogen compared to deuterium is uncovered and believed to play an important role. The origin of this radial electric field difference is determined to have two possible origins: differences in poloidal rotation and turbulent Reynolds stress in the closed field line region, and increased outer strike point temperatures and space potentials on open field lines. Experimental observations from both profile and turbulence diagnostics are supported by nonlinear gyrokinetic simulations using the code CGYRO. Simulations illustrated heat transport isotope effects in the plasma edge and shear layer resulting from differences in impurity content, electron non-adiabaticity, and main ion mass dependent E × B shear stabilization. Turbulence prediction comparisons from flux-matched CGYRO simulations to experimental measurements including electron temperature, density and velocity fluctuations are found to be in good agreement with available data. A dedicated DIII-D experiment in hydrogen was performed to seed more carbon than naturally occurring, to match deuterium experiments, and possibly reduce the L-H power threshold based on gyro-kinetic predictions. To our surprise, while ion temperature gradient (ITG) turbulence was stabilized, nodiscernible change in L-H power threshold were observed in these special hydrogen experiments. In particular, it is noticed that the edge radial electric field and Reynolds stress were observed as nearly unchanging in the presence of ITG stabilization. These experimental data have enabled a more comprehensive picture of the multitude of isotope effects at play in fusion experiments, and the important potential connection between the confined and unconfined plasma regions in regulating L-H transition dynamics.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Standard operating procedure for post-operation component disassembly and observation of benchtop water electrolyzer testing

Post-operation component disassembly and observation of electrolyzer parts is useful in understanding the interactions of the components and the electrochemical environment beyond the systems electrochemical output. We report a standard protocol for post-operation component disassembly and observation, including directions for cell-component preservation, preliminary visual inspection of cell components, and a guide for the advanced inspection of specific components with suggestions for further analysis if necessary. The procedures outlined here allow for a standardized method that can be used and compared between different laboratories and for literature comparison to experimental results.

03 NATURAL GAS↗
DOE OSTI2020

High Layer Uniformity of Two-Dimensional Materials Demonstrated Surprisingly from Broad Features in Surface Electron Diffraction

Paradoxically, a very broad diffraction background, named the bell-shaped-component (BSC), has been established as a feature of graphene growth. Recent diffraction studies as a function of electron energy have shown that the BSC is not related to scattering interference. Here, additional experiments are carried out as a function of temperature over the range in which single-layer graphene (SLG) grows. Quantitative fitting of the profiles shows that the BSC follows the increase of the Gr(10) spot, proving directly that the BSC indicates high-quality graphene. Additional metal deposition experiments provide more information about the BSC. The BSC is insensitive to metal deposition, and it increases with metal intercalation, because a more uniform interface forms between graphene and SiC. These experiments support the conclusion that the BSC originates from electron confinement within SLG, and surprisingly, it is an excellent measure of graphene uniformity.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Hole-Trapping-Induced Stabilization of Ni 4+ in SrNiO 3 /LaFeO 3 Superlattices

Creating new functionality in materials containing transition metals is predicated on our ability to control the associated charge states. For a given metal, forming lower oxidation states is typically easier than generating higher values, and there is an upper limit on valence that is not exceeded under normal conditions. Here we demonstrate that we can exceed the normal upper limit of 3+ for Ni and Fe via synthesis of (SrNiO 3 )m/(LaFeO 3 )n superlattices by tuning n and m. The Goldschmidt tolerance constraints are lifted and SrNi 4+ O 3 with holes on adjacent O anions can be stabilized as a perovskite at the single unit cell level (m = 1). Spectroscopy reveals that the n = 1 superlattice contains Ni 3+ and Fe 4+ , whereas Ni 4+ and Fe 3+ are observed in the n = 5 superlattice. Here, our results show that the B-site cation valences can be tuned by controlling the magnitude of the FeO6 octahedral rotations which in turn drive the energy balance between Ni 3+ /Fe 4+ and Ni 4+ /Fe 3+ , thus controlling emergent electrical properties such as the band alignment and resulting hole confinement. We suggest that this approach may be generally useful for synthesizing novel, metastable layered structures with new functionalities.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Growth of PdCoO 2 by ozone-assisted molecular-beam epitaxy

We report the in situ , direct epitaxial synthesis of (0001)-oriented PdCoO 2 thin films on c-plane sapphire using ozone-assisted molecular-beam epitaxy. The resulting films have smoothness, structural perfection, and electrical characteristics that rival the best in situ grown PdCoO 2 thin films in the literature. Metallic conductivity is observed in PdCoO 2 films as thin as ~2.0 nm. The PdCoO 2 films contain 180° in-plane rotation twins. Scanning transmission electron microscopy reveals that the growth of PdCoO 2 on the (0001) surface of Al 2 O 3 begins with the CoO 2 layer.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Lower-hybrid drift waves and their interaction with plasmas in a 3D symmetric reconnection simulation with zero guide field

We investigate lower-hybrid drift waves (LHDW) in symmetric magnetic reconnection with zero guide field using three-dimensional particle-in-cell simulations. The long-wavelength mode with kρiρe∼1 develops in the bifurcated electron current layer around the X-line within the width of the electron meandering motion from the mid-plane, where ρi(e) is the ion (electron) gyroradius. The short-wavelength mode with kρe∼1 develops in the separatrix region downstream of the electron outflow jet, producing electron vortices in the background flow frame. Electrons follow the E × B drift with corrections from the diamagnetic drift and are heated inside the vortices with diverging electric fields. In the vortices, ions have comparable E × B and inertia drifts, which together mostly cancel the diamagnetic drift. Toward the center of diverging field vortices, ions are decelerated, leading to a decrease in the perpendicular temperature, while the loss of low-energy ions results in an increase in the parallel temperature. Parallel electric fields exist as a combination of the LHDW wave field projected to the magnetic field direction and the penetration of whistler waves that are mainly outside of the LHDW layer. The magnetic flux tube is twisted in the vortices. The twist may potentially lead to slippage reconnection, as indicated by the non-uniform parallel potential variation across field lines, while the periodic variations of the twisting directions are a limiting factor.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Encapsulation Materials Tailored to Perovskite Photovoltaics

The work combines NREL as the world leader in perovskite and polymeric materials, and teams them up with The Dow Chemical Company, the world leader in commercial production of PV encapsulation materials. The team will design and evaluate encapsulation materials that are tailored to perovskite photovoltaics. Demonstration of polyolefin-based encapsulants for perovskite PV will be impactful for a number of reasons: 1) There is no clear-cut choice for encapsulation for perovskite PV to date. 2) There is high synthetic control of the material properties for future perovskite module designs. 3) Among the candidate materials, they have the highest barrier properties, 4) Polyolefins are the most prevalent (>20 million metric tons consumed in the US alone) and inexpensive (<1.5 $USD/kg) polymers used worldwide. 5) They are recyclable and may play a role in future of circular PV materials. 6) They are manufactured domestically. The work also highlights careful design of perovskite transport layer materials for surviving vacuum encapsulation.

14 SOLAR ENERGY↗
DOE OSTI2021

Actinic and electron beam radiation curable water based electrode binders and electrodes incorporating same

A process for manufacturing an electrode utilizing electron beam (EB) or actinic radiation to cure the electrode binder is provided. A process is also disclosed for mixing specific actinic or EB radiation curable polymer precursors with electrode solid particles to form an aqueous mixture, application of the mixture to an electrode current collector, followed by the application of actinic or EB radiation to the current collector for curing the polymer, thereby binding the electrode binder to the current collector. Lithium ion batteries, electric double layer capacitors, and components produced therefrom are also provided.

Voelker, Gary E.↗