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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Effect of ball milling conditions on microstructure and lithium storage properties of LiNi0.5Mn1.5O4 as cathode for lithium-ion batteries

Highlights: • Precursors of LNM respectively synthesized by dry and wet ball-milling. • Under wet ball-milling raw materials form slurry and mix well in microscale. • LNM-w12 sample presents proper stoichiometric composition and the highest D{sub Li}{sup +}. • At 0.1 C rate LNM-w12 delivers 133 mAh g{sup −1} at 100 cycle close to theoretical value. • LNM-w12 delivers 97 mAh g{sup −1} at 10 C rate and remains 78% after 1000 cycles. - Abstract: In this work, the precursors of LiMn{sub 1.5}Ni{sub 0.5}O{sub 4} (LNM) are respectively synthesized by dry and wet ball-milling. Under wet ball-milling, the problem of sticky residue in dry ball-milling is effectively resolved, the three raw materials form homogeneous slurry and mix well in micrometers level. LNM-w12 sample synthesized by using precursor added 12 mL milling medium gains the atomic composition closed to the theoretical value, ordered crystal structure and the highest lithium diffusion coefficient. At 0.1 C rate, LNM-w12 delivers the capacity of 136 mAh g{sup −1} at the first cycle, and 133 mAh g{sup −1} at the 100th cycle. Moreover, LNM-w12 delivers the initial capacity of 97 mAh g{sup −1} at 10 C rate, and remains 78% after 1000 cycles. The great rate capability of LNM-w12 can be attributed to the well-formed crystal structure, ordered and stable surface structure, which is conducive to the diffusion of lithium ions and prevents the dissolution of the material at high voltage.

25 ENERGY STORAGE↗
DOE OSTI2020

Raman Spectroscopy Analysis of the Structure and Surface Chemistry of Ti3C2Tx MXene

Raman spectroscopy is one of the most useful tools for the analysis of two-dimensional (2D) materials. While MXenes are a very large family of 2D transition metal carbides and nitrides, there have been just a few Raman studies of materials from this family. Here, we report on a systematic study of the most widely used and most important MXene to date: Ti 3 C 2 T x . By synthesizing material using different methods, we show that Raman spectra of Ti 3 C 2 T x are affected not only by the composition and surface groups but also by intercalated species and stacking. Due to a plasmonic peak of Ti 3 C 2 T x around 785 nm, resonant conditions are achieved, enabling us to observe an extra peak at ~120 cm –1 , when excited with a red diode laser. We report differences in Raman spectra collected from single flakes of Ti 3 C 2 T x , colloidal solutions, and multilayer films. Lastly, we show how an undesirable photoluminescent background could serve as evidence of material degradation, which leads to the formation of defective titania and amorphous carbon. Overall, this study shows how Raman spectroscopy can be used for the characterization of important emerging 2D materials: MXenes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Insights into the Surface Electronic Structure and Catalytic Activity of InO x /Au(111) Inverse Catalysts for CO 2 Hydrogenation to Methanol

In this article, the direct conversion of carbon dioxide (CO 2 ) into methanol (CH 3 OH) via low-temperature hydrogenation is crucial for recycling anthropogenic CO 2 emissions and producing fuels or high value chemicals. Nevertheless, it continues to be a great challenge due to the trade-off between selectivity and catalytic activity. For CO 2 hydrogenation, In 2 O 3 catalysts are known for their high CH 3 OH selectivity. Subsequent studies explored depositing metals on In 2 O 3 to enhance CO 2 conversion. Despite extensive research on metal (M) supported In 2 O 3 catalysts, the role of In-M alloys and M/In 2 O 3 interfaces in CO 2 activation and CH 3 OH selectivity remains unclear. In this work, we have examined the behavior of In/Au(111) alloys and InO x /Au(111) inverse systems during CO 2 hydrogenation using synchrotron-based ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and catalytic tests in a batch reactor. Indium forms alloys with Au(111) after deposition. The In-Au(111) alloys display high reactivity towards CO 2 and can dissociate the molecule at room temperature to generate InO x nanostructures. At very low coverages of In (≤ 0.05 ML), the InO x nanostructures are not stable under CO 2 hydrogenation conditions and the active In-Au(111) alloys produces mainly CO and little methanol. An increase in indium coverage to 0.3 ML led to stable InOx nanostructures under CO 2 hydrogenation conditions. These InO x /Au(111) catalysts displayed a high selectivity (~ 80 %) towards CH 3 OH production and an activity for CO 2 conversion that was at least 10 times larger than that of plain In 2 O 3 or Cu(111) and Cu/ZnO(000$\overline{1)}$ benchmark catalysts. The results of AP-XPS show that InO x /Au(111) produces methanol via methoxy intermediates. Inverse oxide/metal catalysts containing InOx open up a possibility for improving CO 2 → CH 3 OH conversion in processes associated with the control of environmental pollution and the production of high value chemicals.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Magnetoelectric properties of (Pb{sub 0.60}Sr{sub 0.40})TiO{sub 3}-CFO composite thin film synthesized by metallo-organic decomposition

(Pb{sub 0.60}Sr{sub 0.40}) TiO{sub 3}-CFO composite thin films were grown on Pt/TiO{sub 2}/Si substrate by novel metallo-Organic process using spin coating technique. The structural, surface morphology and micro structural properties were confirmed by X-Ray diffraction (XRD), Raman spectroscopy, atomic force microscope (AFM) and TEM respectively. The lattice constant of the composite thin film crystallized in the pervoskite and spinel phase was 3.9531 and 8.571 Ǻ. Excellent ferroelectric behavior at 10V was observed, a room temperature magnetic hysteresis shows good results. The saturation magnetization value of the bilayer thin film is lower than that of the pure CFO film which is may be attributed to presence of non ferromagnetic PST layer A high initial behavior of dynamic ME response coefficient for the film was observed. The ME effect of the film strongly depends on the magnetic bias.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Gapless surface electronic structure of $1T–$$\mathrm{TiSe_2}$ in the distorted phase

Here, low temperature, high resolution angle resolved photoemission experiments performed on bulk $1T–$$\mathrm{TiSe_2}$ samples display conspicuous band folding as the only prominent signature of the periodic lattice distortion. The presence of a bulk electronic gap supporting a charge density wave phase is not confirmed in light of the new data. These observations cast serious doubts on the common belief of an electronic instability as the likely origin for the observed structural transition in $\mathrm{TiSe_2}$.

36 MATERIALS SCIENCE↗
DOE OSTI2015

NESM TAG Meeting Notes

March 2015 NESM TAG Notes related to 1) Structure surface representation, 2) Structure-fluid coupling algorithm, 3) Coupled time integration scheme, 4) Coupling data exchange API, 5) Portability across platforms and builds, and 6) Testing and verification.

96 KNOWLEDGE MANAGEMENT AND PRESERVATION↗
NASA NTRS1978

Stress analysis for structures with surface cracks

Two basic forms of analysis, one treating stresses around arbitrarily loaded circular cracks, the other treating stresses due to loads arbitrarily distributed on the surface of a half space, are united by a boundary-point least squares method to obtain analyses for stresses from surface cracks in places or bars. Calculations were for enough cases to show how effects from the crack vary with the depth-to-length ratio, the fractional penetration ratio, the obliquity of the load, and to some extent the fractional span ratio. The results include plots showing stress intensity factors, stress component distributions near the crack, and crack opening displacement patterns. Favorable comparisons are shown with two kinds of independent experiments, but the main method for confirming the results is by wide checking of overall satisfaction of boundary conditions, so that external confirmation is not essential. Principles involved in designing analyses which promote dependability of the results are proposed and illustrated.

Bell, J. C.↗