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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Operando NMR and XRD study of chemically synthesized LiCx oxidation in a dry room environment

We test the stability of pre-lithiated graphite anodes for Li-ion batteries in a dry room battery processing room. The reaction between LiCx and laboratory air was followed using operando NMR and x-ray diffraction as these methods are sensitive to change in Li stoichiometry in graphite. There is minimal reactivity between LiC 6 and N 2 , CO 2 or O 2 ; however, LiC 6 reacts with moisture to form lithium (hydr)oxide. The reaction rate follows zero-order kinetics with respects to intercalated lithium suggesting that lithium transport through the graphite is fast. The reaction mechanism occurs by sequential formation of higher stages LiC 12 , then LiC 18 , and then LiC 24 as the hydrolysis proceeds to the formation of Li x OH y and graphite end products. Slowing down the formation rate of the Li x OH y passivation layer stabilizes of the higher stages.

25 ENERGY STORAGE↗
NASA NTRS1982

Surface Seal for Carbon Parts

Surface pores in parts made of graphite or reinforced-carbon/ carbon materials are sealed by a silicon carbide-based coating. Coating inhibits subsurface oxidation and lengthens part life. Starting material for coating is graphite felt, which is converted to silicon carbide felt by processing it according to a prescribed time/temperature schedule. Converted felt is pulverized in a ball mill and resulting powder is mixed with an equal weight of black silicon carbide powder. Powder mixture is combined with an equal weight of adhesive to form a paste.

Shuford, D. M.↗
DOE OSTI2018

Facile preparation of porous nickel oxide membrane for flexible supercapacitors electrode via phase-separation method of polymer

Highlights: • Polymer/metal oxide hybrid membrane is fabricated for supercapacitors electrode. • Effects of membrane components on structure and performance are investigated. • The prepared electrode membrane shows high flexible property. • A capacitance of 794 F/g is obtained at a current density of 1.0 A/g. • Symmetric supercapacitor device exhibits an energy density of 39.6 Wh/kg. - Abstract: In this article, a porous flexible membrane electrode of nickel oxide is developed by a facile method based on liquid-liquid phase-separation. The effects of the membrane components on structures and electrochemical behaviors of membrane electrode are investigated. The results reveal that nano NiO and conducting graphite are imbedded into the polymer membrane of polyethersulfone to form a flexible hybrid membrane (M-NiO-G), which shows the highest specific capacitance of 794.0 F/g at a current density of 1.0 A/g. The asymmetrical supercapacitor device based on the as-synthesized of M-NiO-G (positive electrode) and activated carbon membrane (negative electrode) exhibits a high specific capacitance of 154.0 F/g at a current density of 0.2 A/g. The coulombic efficiency remains about 95.0%, and the capacitance retention is 84.8% after 5000 charging-discharging cycles at 1.0 A/g. The energy density of the asymmetrical supercapacitor device reaches 39.6 Wh/kg at a power density of 516.9 W/kg, still remains 20.0 Wh/kg at a high power density of 2567.4 W/kg in the potential window from 0 to 1.36 V in 6 M KOH aqueous solution.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Characterization of submonolayer film composed of soft-landed copper nanoclusters on HOPG

Preformed Copper nanoclusters are deposited on highly oriented pyrolytic graphite (HOPG) at very low energy. For the study of chemical composition X-ray Photoelectron Spectroscopy (XPS) is performed for a wide range of binding energy without exposing the sample in the ambient. Morphological aspects of the supported clusters are characterized employing high resolution scanning electron microscope (SEM). Different types of morphology are observed depending on the nature of the substrate surface. Big fractal islands are formed on terraces while at the step edges small islands are found to form. Ex-situ cathodoluminescence (CL) measurement shows peak at 558 nm wavelength which corresponds to the band gap of 2.22 eV which is due to Cu{sub 2}O nanocrystals formed due to oxidation of the deposited film in ambient.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1982

Processing of fused silicide coatings for carbon-based materials

The processing and oxidation resistance of fused Al-Si and Ni-Si slurry coatings on ATJ graphite was studied. Ni-Si coatings in the 70 to 90 percent Si range were successfully processed to melt, wet, and bond to the graphite. The molten coatings also infiltrated the porosity in graphite and reacted with it to form SiC in the coating. Cyclic oxidation at 1200 C showed that these coatings were not totally protective because of local attack of the substrate, due to the extreme thinness of the coatings in combination with coating cracks.

Smialek, J. L.↗
NASA NTRS1983

Processing of fused silicide coatings for carbon-based materials

The processing and oxidation resistance of fused Al-Si and Ni-Si slurry coatings on ATJ graphite was studied. Ni-Si coatings in the 70 to 90 percent Si range were successfully processed to melt, wet, and bond to the graphite. The molten coatings also infiltrated the porosity in graphite and reacted with it to form SiC in the coating. Cyclic oxidation at 1200 C showed that these coatings were not totally protective because of local attack of the substrate, due to the extreme thinness of the coatings in combination with coating cracks. Previously announced in STAR as N83-27019

Smialek, J. L.↗
DOE OSTI2024

Lithium ion cells with high performance electrolyte and silicon oxide active materials achieving very long cycle life performance

Improved negative electrodes can comprise a silicon based active material blended with graphite to provide more stable cycling at high energy densities. In some embodiments, the negative electrodes comprise a blend of polyimide binder mixed with a more elastic polymer binder with a nanoscale carbon conductive additive. Electrolytes have been formulated that provide for extended cycling of cells incorporating a mixture of a silicon-oxide based active material with graphite active material in negative electrodes that can be matched with positive electrodes comprising nickel rich lithium nickel manganese cobalt oxides to cells with unprecedented cycling properties for large capacity cell based on a silicon negative electrode active material.

Dong, Yingnan↗
DOE OSTI2020

Advanced electrolytes for fast-charging high-voltage lithium-ion batteries in wide-temperature range

LiNixMnyCo1-x-yO2 (NMC) cathode materials with Ni=0.8 have attracted great interest for application in high energy-density lithium (Li)-ion batteries (LIBs) because of their high specific capacities at high voltages. However, the practical application of Ni-rich NMC in LIBs under high charge voltages (e.g. 4.4 V and above) still faces big challenges due to the severe capacity fading, which is directly related to the instability of the cathode/electrolyte interface. In this work, we develop new localized high-concentration electrolytes (LHCEs) based on carbonate solvents, which are compatible with graphite (Gr) anode and have a high oxidation potential over 4.9 V vs. Li/Li+. The optimal LHCE enables the Gr||NMC811 cells with 2.8 mAh cm-2 cathode areal capacity loading to achieve an excellent cycling stability over 600 cycles with a capacity retention of 94.2 % under a charge cut-off voltage of 4.4 V at 25 ?C, good rate capabilities under fast charging or discharging up to 3C rate, and superior low-temperature discharge performance down to -30 ?C with a capacity retention of 85.6% at C/5 rate. The findings in this work shed light a very promising strategy to develop new electrolytes for practical high-energy LIBs with Ni-rich NMC cathodes.

Zhang, Xianhui↗
DOE OSTI2017

Transition metal dissolution, ion migration, electrocatalytic reduction and capacity loss in Lithium-ion full cells

Continuous operation of full cells with layered transition metal (TM) oxide positive electrodes (NCM523) leads to dissolution of TM ions and their migration and incorporation into the solid electrolyte interphase (SEI) of the graphite-based negative electrode. These processes correlate with cell capacity fade and accelerate markedly as the upper cutoff voltage (UCV) exceeds 4.30 V. At voltages ≥ 4.4 V there is enhanced fracture of the oxide during cycling that creates new surfaces and causes increased solvent oxidation and TM dissolution. Despite this deterioration, cell capacity fade still mainly results from lithium loss in the negative electrode SEI. Among TMs, Mn content in the SEI shows a better correlation with cell capacity loss than Co and Ni contents. As Mn ions become incorporated into the SEI, the kinetics of lithium trapping change from power to linear at the higher UCVs, indicating a large effect of these ions on SEI growth and implicating (electro)catalytic reactions. Lastly, we estimate that each Mn II ion deposited in the SEI causes trapping of ~10 2 additional Li + ions thereby hastening the depletion of cyclable lithium ions. Using these results, we sketch a mechanism for cell capacity fade, emphasizing the conceptual picture over the chemical detail.

25 ENERGY STORAGE↗
NASA NTRS1986

Effect of hard particle impacts on the atomic oxygen survivability of reflector surfaces with transparent protective overcoats

Silver mirror samples with protective coatings were subjected to a stream of 27 microns alumina particles to induce pinhole defects. The protective coating consisted of a layer of aluminum dioxide over silver followed by a layer of silicon dioxide over the alumina. Samples were prepared on both graphite-epoxy composite and fused quartz substrates. After exposure to the hard particle stream, the samples were exposed to an oxygen plasma environment in a laboratory plasma asher. The effects of both the hard particles and the oxygen plasma were documented by both reflectance measurements and scanning electron microscopy. The results indicated that oxidative damage to the silver reflecting layer continues beyond that of the erosively exposed silver. Oxidative undercutting of the silver layer and graphite-epoxy substrate continues in undamaged areas through adjacent, particle damaged defect sites. This may have implications for the use of such mirrors in a space station solar dynamic power system.

Gulino, D. A.↗
NASA NTRS1987

Effect of hard particle impacts on the atomic oxygen survivability of reflector surfaces with transparent protective overcoats

Silver mirror samples with protective coatings were subjected to a stream of 27 microns alumina particles to induce pinhole defects. The protective coating consisted of a layer of aluminum dioxide over silver followed by a layer of silicon dioxide over the alumina. Samples were prepared on both graphite-epoxy composite and fused quartz substrates. After exposure to the hard particle stream, the samples were exposed to an oxygen plasma environment in a laboratory plasma asher. The effects of both the hard particles and the oxygen plasma were documented by both reflectance measurements and scanning electron microscopy. The results indicated that oxidative damage to the silver reflecting layer continues beyond that of the erosively exposed silver. Oxidative undercutting of the silver layer and graphite-epoxy substrate continues in undamaged areas through adjacent, particle damaged defect sites. This may have implications for the use of such mirrors in a space station solar dynamic power system.

Gulino, Daniel A.↗
DOE OSTI2018

The Influence of Fabrication Methods on Structure and Microwave Absorption Property of Fe{sub 3}O{sub 4}/rGO Composites

In this study, flake graphite is used as raw material and oxidized to produce graphene oxide (GO), and then two kinds of ferroferric oxide/reduced graphene oxide (Fe{sub 3}O{sub 4}/rGO) composites are fabricated with one-step and two-step methods, respectively. The influence of composite methods on structure and performance is investigated by FT-IR, XRD, SEM, TEM, and testing of electromagnetic parameters. The results show that there are many advantages in the one-step method for fabrication of Fe{sub 3}O{sub 4}/rGO composite, such as the composite process is simplified, the time is shortened, and the Fe{sub 3}O{sub 4}/rGO composite fabricated with the one-step method has the best microwave impedance matching property in the frequency range of 2.5–6 GHz. At the same time, it can be found that there is the Fe–O–C bond in Fe{sub 3}O{sub 4}/rGO composites fabricated with the one-step method, which results in two ways of physical recombination and chemical bonding between Fe{sub 3}O{sub 4} and rGO sheet particulates. In addition, when the mass ratio of GO and FeCl{sub 3} is 1:10, the R{sub L} value of the Fe{sub 3}O{sub 4}/rGO composite fabricated with the one-step method is minimum, and the increase of sample thickness is beneficial to improve the impedance matching property of Fe{sub 3}O{sub 4}/rGO composite in the frequency range of 2.5–6 GHz.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

ENDF/B-VIII.1: Thermal Neutron Scattering Sublibrary

The thermal neutron scattering law (TSL) sublibrary aims to describe the interaction of incident neutrons at thermal or sub-thermal energies with different compound materials such fuels, moderators and special-purpose materials. In ENDF/B-VIII.1 there was a large number of new and updated TSL evaluations, including traditional moderators (light water, Beryllium metal, Beryllium Oxide, Calcium Hydride, plastics (Polystyrene and Lucite), graphite (reactor-grade and crystalline), anhydrous Hydrogen Fluoride, and heavy paraffinic oil); exotic moderators (Beryllium Carbide, Zirconium Hydride, Yttrium Hydride, Lithium-7 Hydride and Deuteride), FLiBe molten salt, structural materials and cladding (Silicon Carbide, Silicon Dioxide, Zirconium Carbide), fuels (Plutonium Dioxide, Uranium Carbide, Uranium metal, Uranium Nitride, Uranium Dioxide, Uranium Hydride), and special purpose materials. In ENDF/B-VIII.1 we also distribute alongside the evaluated files, a comma-separated file (CSV), named TSL_MAT_numbers.csv, which lists all evaluated files in the current release and their corresponding unique MAT number.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗