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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 1,585 records · Page 88
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Facile synthesis of interconnected mesoporous ZnMn2O4 nano-peanuts for Li-storage via distinct structure design

Highlights: • Interconnected mesoporous ZnMn{sub 2}O{sub 4} nano-peanuts were successfully synthesized. SS • Novel ZnMn{sub 2}O{sub 4} have three structural features: special mesoporous structure, high specific surface and interconnected walls. • The interconnected mesoporous structure can buffer volume change and avoid particle aggregation. • The ZnMn{sub 2}O{sub 4} nano-peanuts delivered high stable reversible lithium storage properties. - Abstract: The ZnMn{sub 2}O{sub 4} nano-peanuts with diameters of 16–25 nm have been successfully prepared through a simple one-step surfactant-assisted solvothermal process. The as-synthesized ZnMn{sub 2}O{sub 4} exhibits novel interconnected mesoporous hierarchical architecture, which possesses three advantages: special mesoporous structure, high specific surface and interconnected walls. On one hand, the interconnected structure can provide sufficient surface reaction sites to fully contact Li{sup +} with the electrolyte and improve Li{sup +} diffusion and electron transfer; On the other hand, the mesoporous hierarchical networks can buffer the volume change, accommodate or alleviate the strain during charge-discharge process, thus enhancing the conductivity and stability of the electrodes. Benefiting from the mesoporous design, the interconnected ZnMn{sub 2}O{sub 4} delivers a stable capacity (812 mA h g{sup −1} at 100 mA g{sup −1} after 200 cycles), and maintains a high capacity of 516 mA h g{sup −1} even at 2 A g{sup −1} after 200 cycles, which shows that the nanostructured ZnMn{sub 2}O{sub 4} has excellent cycling stability.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

A review of in situ/operando studies of heterogeneous catalytic hydrogenation of CO 2 to methanol

Repurposing CO 2 into chemicals, one of the Carbon Dioxide Removal (CDR) strategies, still faces significant challenges in conversion and energy efficiency due to the lack of effective catalysts and processes. Fundamental understanding through in situ/operando investigations of the reaction mechanisms and catalyst structures is pivotal for developing the efficient catalysts. This paper reviews the past and recent in situ/operando studies of methanol synthesis from heterogeneous CO 2 hydrogenation over a few typical catalysts including Cu-based, oxide-based, and noble-metal-based catalysts. With the development of high-pressure reactors, in situ/operando IR, X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), neutron diffraction and imaging have been used to reveal the surface intermediates and structures of working catalysts under CO 2 hydrogenation conditions. On the one hand, the combined operando techniques shed light on working mechanisms for some catalytic systems. On the other hand, due to the complexity of selective CO 2 hydrogenation reaction and limited sensitivity of current accessible operando techniques to the surface structure of catalysts, it is still murky about the exact nature of the active sites at the surface/interface and how different sites promote different reaction paths. Furthermore, it is concluded that new methodologies for differentiating signals from different sites, and the development of surface-sensitive techniques for high pressure reactions are needed for providing structural descriptors of highly active and selective CO 2 conversion catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1982

Influence of fabrication tolerances on the surface accuracy of large antenna structures

One of the sources of error in radio frequency antennas is the lack of dimensional precision of the surface. This paper presents an approach for estimating the amount of error caused by random dimensional imperfections of the many structural elements which make up a truss-type antenna. A principle of equivalence between the analyses of statistical errors and of the natural vibration frequencies of the structure is developed. Examples are presented to show the application of this equivalence principle to the determination of average surface errors of several types and proportions of antenna structures.

Hedgepeth, J. M.↗
DOE OSTI2025

Thermal processing to modulate surface chemistry and bulk charge distribution in nickel-rich layered lithium positive electrodes

The broader application of nickel-rich layered oxides as positive electrode materials for lithium-ion batteries has been hindered by their high manufacturing cost and inferior cycling stability. Thermal processing, which is integral to electrode materials manufacturing and fundamental in materials science, has not been fully utilized to design advanced positive electrode materials. Herein, we demonstrate the capability of using quenching heat treatment to regulate Li distribution and modulate electronic structure near particle surface. The resulting materials exhibit less parasitic reactions with the electrolyte and an improved charge distribution homogeneity in secondary particles, leading to more stable cycling performance at high voltages (4.5 V vs Li/Li + ). Our synchrotron X-ray analyses reveal the underlying interplay between surface structure and bulk charge distribution in positive electrode materials particles. While strategies used to stabilize positive electrode materials through compositional control, surface modification, and electrolyte engineering have become mature, thermal processing can be advantageous to further improve positive electrode materials manufacturing.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Ordered Mesoporous Metal Carbides with Enhanced Anisole Hydrodeoxygenation Selectivity

Mesoporous metal carbides are of particular interest as catalysts for a variety of reactions because of their high surface areas, porous networks, nanosized walls, and unique electronic structures. In this work, two ordered mesoporous metal carbides, Mo 2 C and W 2 C, were synthesized using a nanocasting approach coupled with a simultaneous decomposition/carburization process under a continuous methane flow. The as-synthesized mesoporous Mo 2 C and W 2 C have three dimensionally ordered porous structures, large surface areas (70–90 m 2 g –1 ), and crystalline walls. In vapor-phase anisole hydrodeoxygenation (HDO) reactions, they exhibited turnover frequencies of approximately 9 and 2 × 10 –4 mol molCO –1 s –1 , respectively, at relatively low reaction temperatures (423–443 K) and ambient hydrogen pressures. Notably, the ordered mesoporous W 2 C catalyst showed a greater than 96% benzene selectivity in anisole HDO, the highest benzene selectivity reported to date.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Low-nickel cathode chemistry for sustainable and high-energy lithium-ion batteries

The transition to sustainable energy storage demands lithium-ion batteries with high energy density and reduced reliance on critical metals such as nickel (Ni), yet current strategies to increase capacity have largely depended on raising Ni content, leading to escalating supply risks, rising costs and sustainability concerns. More critically, Ni-rich cathodes suffer from rapid electrochemical degradation driven by structural instability, creating an insurmountable trade-off between capacity and cycle life. Here, in this study, we introduce a low-Ni chemistry cathode, Li(Li 0.05 Ni 0.57 Mn 0.31 Co 0.07 )O 2 , with a radial phase integration design that overcomes these limitations, enabling a remarkable Ni usage reduction (Ni < 0.6) while demonstrating high capacity (215 mAh g −1 ) and markedly improved cyclability (~97% retention over 400 cycles) compared to conventional high-Ni cathodes (Ni = 0.8). Advanced X-ray and electron microscopy analyses reveal that the designed cathode exhibits a highly reversible oxygen anionic redox, benefiting from a structurally stable surface and minimizing irreversible phase transitions. Moreover, the integrated structure substantially mitigates lattice strain and improves mechanical stability even under harsh conditions. In conclusion, this advance offers a general design principle for developing next-generation cathodes that combine resource efficiency with long-term electrochemical reliability.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Control of Surface Chemical Reactions through Solid Stiffness

Control of surface reactions is commonly achieved by modification of surface electronic structures. Here, we discover an alternative pathway for controlling surface reactions by tuning the mechanical stiffness of the underlying material. We find that in addition to the typically assumed surface electronic contribution right at the reactive site, the contribution from the deformation of the bulk region plays a vital role in controlling surface reactions. The underlying mechanism is an elastic relaxation of the solid, which depends on the material’s stiffness and can be modified by tuning bulk stoichiometry. The effect of bulk stiffness on surface reactions has been demonstrated by considering hydrogen scission reaction and oxygen incorporation reaction during corrosion of amorphous SiC in water and air, respectively. Finally, our results imply that tuning of bulk stiffness by modifying stoichiometry can provide an effective method for controlling surface reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1992

Workshop on the Martian Surface and Atmosphere Through Time

The purpose of the workshop was to bring together the Mars Surface and Atmosphere Through Time (MSATT) Community and interested researchers to begin to explore the interdisciplinary nature of, and to determine the relationships between, various aspects of Mars science that involve the geological and chemical evolution of its surface, the structure and dynamics of its atmosphere, interactions between the surface and atmosphere, and the present and past states of its volatile endowment and climate system.

Haberle, Robert M.↗
DOE OSTI2023

Surface Energy Dynamics and Canopy Structural Properties in Intact and Disturbed Forests in the Southern Amazon

The Brazilian Amazon has been a focus of land development with large swaths of forests converted to agriculture. Forest degradation by selective logging and fires has accompanied the agricultural frontier and has resulted in significant impacts on Amazonian ecosystems. Changes in forest structure resulting from forest disturbances have large impacts on the surface energy balance, including on land surface temperature (LST) and evapotranspiration (ET). This study's objective is to assess the effects of forest disturbances on water fluxes and forest structure in a transitional forest site in the Southern Amazon. We used ET and LST products from MODIS and Landsat 8 and GEDI-derived forest structure data to address our research questions. We found that disturbances induced seasonal water stress, more pronounced in croplands/pastures than in forests (differences up to 20% in the dry season), and more pronounced in second-growth and recently burned areas than in logged and intact forests (differences up to 12% in the dry season). Moreover, ET and LST were negatively related, with more consistent relationships across disturbance classes in the dry season (R 2 : 0.41–0.87) than in the wet season (R 2 : 0.18–0.49). Forest and cropland or pasture classes showed contrasting relationships in the dry season. Finally, we found that forest structure exhibited stronger relationships with ET and LST in the most disturbed forests (R 2 : 0.01–0.43) than in the least disturbed forests (R 2 < 0.05). Our findings help to elucidate degraded forests functioning under a changing climate and to improve estimates of water and energy fluxes in Amazonian degraded forests.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Low-Level Liquid-Bearing Clouds Contribute to Seasonal Lower Atmosphere Stability and Surface Energy Forcing over a High-Mountain Watershed Environment

Measurements of atmospheric structure and surface energy budgets distributed along a high-altitude moun tain watershed environment near Crested Butte, Colorado, from two separate, but coordinated, field campaigns, Surface Atmosphere Integrated field Laboratory (SAIL) and Study of Precipitation, the Lower Atmosphere, and Surface for Hydrometeorology (SPLASH), are analyzed. This study identifies similarities and differences in how clouds influence the radiative budget over one snow-free summer season (2022) and two snow-covered seasons (2021/22; 2022/23) for this alpine location. A relationship between lower-tropospheric stability stratification and longwave radiative flux from the presence or absence of clouds is identified. When low clouds persisted, often with signatures of supercooled liquid in win ter, the lower troposphere experienced weaker stability, while radiatively clear skies that are less likely to be influenced by liquid droplets were associated with appreciably stronger lower-tropospheric stratification. Corresponding surface turbu lent heat fluxes partitioned differently based upon the cloud–stability stratification regime derived from early morning radiosounding profiles. Combined with the differences in the radiative budget largely resulting from dramatic seasonal dif ferences in surface albedo, the lower atmosphere stratification, surface energy budget, and near-surface thermodynamics are shown to be modified by the effective longwave radiative forcing of clouds. The diurnal evolution of thermodynamics and surface energy components varied depending on the early morning stratification state. Thus, the importance of quies cent versus synoptically active large-scale meteorology is hypothesized as a critical forcing for cloud properties and associ ated surface energy budget variations. The physical relationships between clouds, radiation, and stratification can provide a useful suite of metrics for process understanding and to evaluate numerical models in such an undersampled, highly com plex terrain environment.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Modulating Hole Transfer from CdSe Quantum Dots by Manipulating the Surface Ligand Density

The structure and density of surface capping ligands in cadmium chalcogenide quantum dots (QDs) are important considerations for controlling the efficiency of charge separation via the transfer of electrons or holes to molecular acceptors. Here we show how the manipulation of the surface ligand density of oleic acid-capped cadmium selenide (CdSe) QDs impacts the efficiency of hole transfer (HT) to polyoxovanadate alkoxides. Meerwein’s salt is used as a ligand-stripping agent, providing opportunities to quantitatively manipulate the ligand density at the surface of the nanocrystal, as evidenced by 1 H NMR spectroscopy. Time-resolved photoluminescence and transient absorption spectroscopies reveal that the extent of HT is quantitatively related to increased surface accessibility. Collectively, these results show that the reduction of surface ligand density can be used to tune the extent of interactions of molecular acceptors with QDs, providing a route to control charge-transfer processes relevant to improving the efficiency of QDs as photosensitizers.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Structure-phase state and mechanical properties of surface layers in titanium nikelide single crystals after shock mechanical treatment

The influence of ultrasonic shock surface treatment (USST) on refine structure and mechanical characteristics of surface layers and deformation behaviour of volume samples of TiNi(Fe, Mo) shape memory effect alloy single crystals is studied using optical and transmission electron microscope, X-ray diffraction, nanoindentation, mechanical attrition testing and experiments on uniaxial tension.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Prediction of Substrate Distortion in Powder DED Using Finite Element Model

Abstract Leveraging the capabilities of both additive and subtractive manufacturing to repair tooling and other high value items can result in significant cost and time saving opportunities. However, when dimensional accuracy of the repaired component must be held within a specified tolerance, distortion of the component induced during repair can lead to an out of specification final component. This work presents simulation of a novel method to mitigate part distortion using sacrificial support structures. A blown powder directed energy deposition system was utilized for deposition of sacrificial support structures and clad surface depositions. Sacrificial support structures were deposited on the underside of the substrate with varying geometries prior to clad surface depositions. A finite element model was developed and verified using experimental results. The simulation and experimental control results were found to match within 6%. It has been shown that simulation can be used to predict effects of sacrificial support structures on substrate distortion in a blown powder directed energy deposition process.

Burl, Alan G.↗
NASA NTRS2013

Method for Estimating Operational Loads on Aerospace Structures Using Span-Wisely Distributed Surface Strains

This report presents a new method for estimating operational loads (bending moments, shear loads, and torques) acting on slender aerospace structures using distributed surface strains (unidirectional strains). The surface strain-sensing stations are to be evenly distributed along each span-wise strain-sensing line. A depth-wise cross section of the structure along each strain-sensing line can then be considered as an imaginary embedded beam. The embedded beam was first evenly divided into multiple small domains with domain junctures matching the strain-sensing stations. The new method is comprised of two steps. The first step is to determine the structure stiffness (bending or torsion) using surface strains obtained from a simple bending (or torsion) loading case, for which the applied bending moment (or torque) is known. The second step is to use the strain-determined structural stiffness (bending or torsion), and a new set of surface strains induced by any other loading case to calculate the associated operational loads (bending moments, shear loads, or torques). Performance of the new method for estimating operational loads was studied in light of finite-element analyses of several example structures subjected to different loading conditions. The new method for estimating operational loads was found to be fairly accurate, and is very promising for applications to the flight load monitoring of flying vehicles with slender wings.

Ko, William L.↗
DOE OSTI2023

High-resolution lithospheric structure of continental China from joint inversion of surface wave and gravity data

The lithospheric structure of continental China has been previously determined by seismic travel time tomography, surface wave tomography, and joint inversion of body wave and surface wave data. However, due to the inherent limitations of seismic data, the lithospheric structure of continental China is still not well resolved in the shallow part and in some regions where the station coverage is relatively sparse. In this study, we aim at improving the lithospheric structure by joint inversion of seismic surface wave data and satellite gravity data to take advantage of the uniform distribution and complementary strength of the gravity data. Here, the empirical relationship between velocity and density is used as a bridge for joint inversion of surface wave and gravity data. The joint inversion shear-wave velocity Vs (density) model, named as USTClitho1.0g, can fit both surface wave and gravity data well. This high-resolution Vs model can better fit the active airgun source seismic arrival times and better delineate some features in continental China, such as the velocity contrast across the north–south gravity lineament (NSGL), the lithosphere thinning in eastern China, the crustal footprint of the Hainan mantle plume, the likely magma chamber beneath volcanos in northeast China, the middle-lower crust low velocity layer beneath the Tibetan plateau, and the tearing of subducted Indian mantle lithosphere. Our joint inversion Vs model can provide a reference model for geosciences in continental China and surrounding areas.

58 GEOSCIENCES↗
DOE OSTI2014

Surface oxidation of GaN(0001): Nitrogen plasma-assisted cleaning for ultrahigh vacuum applications

The cleaning of metal-organic vapor-phase epitaxial GaN(0001) template layers grown on sapphire has been investigated. Different procedures, performed under ultrahigh vacuum conditions, including degassing and exposure to active nitrogen from a radio frequency nitrogen plasma source have been compared. For this purpose, x-ray photoelectron spectroscopy, reflection high-energy electron diffraction, and scanning tunneling microscopy have been employed in order to assess chemical as well as structural and morphological surface properties. Initial degassing at 600 °C under ultrahigh vacuum conditions only partially eliminates the surface contaminants. In contrast to plasma assisted nitrogen cleaning at temperatures as low as 300 °C, active-nitrogen exposure at temperatures as high as 700 °C removes the majority of oxide species from the surface. However, extended high-temperature active-nitrogen cleaning leads to severe surface roughening. Optimum results regarding both the removal of surface oxides as well as the surface structural and morphological quality have been achieved for a combination of initial low-temperature plasma-assisted cleaning, followed by a rapid nitrogen plasma-assisted cleaning at high temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Surface Defect Chemistry and Electronic Structure of Pr 0.1 Ce 0.9 O 2-δ Revealed in Operando

Understanding the surface defect chemistry of oxides under functional operating conditions is important for providing guidelines for improving the kinetics of electrochemical reactions. Ceria-based oxides have applications in solid oxide fuel/electrolysis cells, thermo-chemical water splitting, catalytic convertors, and red-ox active memristive devices. The surface defect chemistry of doped ceria in the regime of high oxygen pressure, pO 2 , approximating the operating conditions of fuel cell cathodes at elevated temperatures, has not yet been revealed. In this paper, we investigated the Pr 0.1 Ce 0.9 O 2-δ (PCO) surface by in operando X-ray photoelectron and absorption spectroscopic methods. We quantified the concentration of reduced Pr 3+ , at the near-surface region of PCO as a function of electrochemical potential, corresponding to a wide range of effective pO 2 . We found that the Pr 3+ concentration at the surface was significantly higher than the values predicted from bulk defect chemistry. This finding indicates a lower effective defect formation energy at the surface region compared with that in the bulk. Finally, in addition, the Pr 3+ concentration has a weaker dependence on pO 2 compared to that in the bulk.

36 MATERIALS SCIENCE↗