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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Auroral heating and the composition of the neutral atmosphere.

Heating of the neutral atmosphere by auroral particle fluxes and by orthogonal electric fields is responsible for large changes in the thermospheric composition that have been observed by satellite mass spectrometers. Vertical winds of a few meters per second are produced in the region subject to auroral heating; this vertical upwelling drives circulation cells that extend the effects of heating in the auroral region on a global scale. Our analysis focuses on the initial phase of a magnetic storm within the auroral region.

Hays, P. B.↗
NASA NTRS2011

Olivine and Pyroxene Compositions in Fine-Grained Chondritic Materials

Our analyses of the Wild-2 samples returned by the Stardust Mission have illuminated critical gaps in our understanding of related astromaterials. There is a very large database of olivine and low-calcium pyroxene compositions for coarse-grained components of chondrites, but a sparse database for anhydrous silicate matrix phases. In an accompanying figure, we present comparisons of Wild-2 olivine with the available chondrite matrix olivine major element data. We thus have begun a long-term project measuring minor as well as major element compositions for chondrite matrix and chondritic IDPs, and Wild 2 grains. Finally, we wish to re-investigate the changes to fine-grained olivine and low-Ca pyroxene composition with progressive thermal metamorphism. We have examined the LL3-4 chondrites which because of the Hayabusa Mission have become very interesting.

Zolensky, Michael E.↗
NASA NTRS2017

El Nino-Induced Tropical Ocean/Land Energy Exchange in MERRA-2 and M2AMIP

Studies have shown the correlation and connection of surface temperatures across the globe, ocean and land, related to Tropical SSTs especially El Nino. This climate variability greatly influences regional weather and hydroclimate extremes (e.g. drought and flood). In this paper, we evaluate the relationship of temperatures across the tropical oceans and continents in MERRA-2, and also in a newly developed MERRA-2 AMIP ensemble simulation (M2AMIP). M2AMIP uses the same model and spatial resolution as MERRA-2, producing the same output diagnostics over 10 ensemble members. Composite El Nino temperature data are compared with observations to evaluate the land/sea contrast, variations and phase relationship. The temperature variations are related to surface heat fluxes and the atmospheric temperatures and transport, to identify the processes that lead to the lagged redistribution of heat in the tropics and beyond. Discernable cloud, radiation and data assimilation changes accompany the onset of El Nino affecting continental regions through the progression to and following the peak values. While the model represents these variations in general, regional strengths and weaknesses can be identified.

Bosilovich, Michael G.↗
NASA NTRS2011

Saturn Ring Data Analysis and Thermal Modeling

CIRS, VIMS, UVIS, and ISS (Cassini's Composite Infrared Specrtometer, Visual and Infrared Mapping Spectrometer, Ultra Violet Imaging Spectrometer and Imaging Science Subsystem, respectively), have each operated in a multidimensional observation space and have acquired scans of the lit and unlit rings at multiple phase angles. To better understand physical and dynamical ring particle parametric dependence, we co-registered profiles from these three instruments, taken at a wide range of wavelengths, from ultraviolet through the thermal infrared, to associate changes in ring particle temperature with changes in observed brightness, specifically with albedos inferred by ISS, UVIS and VIMS. We work in a parameter space where the solar elevation range is constrained to 12 deg - 14 deg and the chosen radial region is the B3 region of the B ring; this region is the most optically thick region in Saturn's rings. From this compilation of multiple wavelength data, we construct and fit phase curves and color ratios using independent dynamical thermal models for ring structure and overplot Saturn, Saturn ring, and Solar spectra. Analysis of phase curve construction and color ratios reveals thermal emission to fall within the extrema of the ISS bandwidth and a geometrical dependence of reddening on phase angle, respectively. Analysis of spectra reveals Cassini CIRS Saturn spectra dominate Cassini CIRS B3 Ring Spectra from 19 to 1000 microns, while Earth-based B Ring Spectrum dominates Earth-based Saturn Spectrum from 0.4 to 4 microns. From our fits we test out dynamical thermal models; from the phase curves we derive ring albedos and non-lambertian properties of the ring particle surfaces; and from the color ratios we examine multiple scattering within the regolith of ring particles.

Saturn's rings↗
DOE OSTI2023

The effect of secondary phases on microstructure and irradiation damage in an as-built additively manufactured 316 L stainless steel with a hafnium compositional gradient

Additive manufacturing (AM) or rapid prototyping has become a crucial tool for reducing both cost and time while increasing efficiency in qualifying structural materials for reactor use. In this study, directed energy deposition (DED) was used to develop an as-built 316 L stainless steel sample with three regions of increasing Hf-dopant to study the effects of Hf on the irradiation response of the material. Morphological and microstructural changes were analyzed before and after 2 MeV proton irradiation at 360 °C to a damage of 2.5 dpa at ~ 10 µm below the surface. The addition of Hf effectively suppressed radiation-induced damage (dislocation loops, radiation-induced segregation) due to enhanced point defect recombination. The radiation damage seen in the as-built sample was further compared to a thermo-mechanically treated counterpart of the same fabrication and irradiation parameters which was found to behave superiorly. In conclusion, the increased radiation resistance of this material may be attributed to the as-built microstructure, which includes undissolved Hf particles, delta ferrite grains and cellular sub-grain boundaries that can hinder defect motion.

316L Stainless Steel↗
DOE OSTI2025

Origin of enhanced performance when Mn-rich rocksalt cathodes transform to δ -DRX

Most Mn-rich cathodes are known to undergo phase transformation into structures resembling spinel-like ordering upon electrochemical cycling. Recently, the irreversible transformation of Ti-containing Mn-rich disordered rock-salt cathodes into a phase — named δ — with nanoscale spinel-like domains has been shown to increase energy density, capacity retention, and rate capability. However, the nature of the boundaries between domains and their relationship with composition and electrochemistry are not well understood. In this work, we discuss how the transformation into the multi-domain structure results in eight variants of Spinel domains, which is crucial for explaining the nanoscale domain formation in the δ -phase. We study the energetics of crystallographically unique boundaries and the possibility of Li-percolation across them with a fine-tuned CHGNet machine learning interatomic potential. Energetics of 16 d vacancies reveal a strong affinity to segregate to the boundaries, thereby opening Li-pathways at the boundary to enhance long-range Li-percolation in the δ structure. Defect calculations of the relatively low-mobility Ti show how it can influence the extent of Spinel ordering, domain morphology and size significantly; leading to guidelines for engineering electrochemical performance through changes in composition.

Anand, Shashwat↗
DOE OSTI2024

Electrical property enhancement of non-heat-treatable wrought aluminum alloys using graphene additives

With growing efforts of electrification, aluminum’s role as a light-weight conductor material has become increasingly prominent. There is a critical need to improve the electrical performance of aluminum at room temperature and high operating temperatures. In this study, the effect of graphene nanoparticle additives on the electrical performance of a non-heat treatable alloy were (AA3003) explored. Graphene’s unusual structure and electronic properties were used to improve AA3003 properties. Here, in this work, the effects of graphene on the evolution of electrical properties and microstructural features have been explored on lab scale hot extruded AA3003-graphene composites. Hot pressing schedules and extrusion temperatures were varied to investigate changes in intermetallic dispersion characteristics in the presence of dispersed graphene. We measured a reduction of 10.3 % in the temperature coefficient of resistance in the AA3003 sample with 0.05 wt% graphene extruded at 400 °C, along with a maximum increase of 1.1 % in electrical conductivity at 20 °C. Increasing the hot-pressing times up to 8 hours was also found to consistently increase the electrical conductivity, due to increased precipitation of intermetallic phases. Despite being a non-heat treatable alloy, AA3003 displays interesting precipitation dynamics and grain recrystallization trends that can be modulated with varying levels of heat treatment, graphene concentrations, and hot extrusion process parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Processing and properties of PSZT 95/5 ceramics with varying Ti and Nb substitution

Niobium doped lead-tin-zirconate-titanate ceramics near the PZT 95/5 orthorhombic AFE – rhombohedral FE morphotropic phase boundary Pb 1-0.5y (Zr 0.865-x Ti x Sn 0.135 ) 1-y Nb y O 3 were prepared according to a 2 2+1 factorial design with x = 0.05, 0.07 and y = 0.0155, 0.0195. The ceramics were prepared by a traditional solid-state synthesis route and sintered to near full density at 1250°C for 6 hours. All compositions were ~98% dense with no detectable secondary phases by XRD. The ceramics exhibited equiaxed grains with intergranular porosity and grain size was ~5 μm, decreasing with niobium substitution. Compositions exhibited remnant polarization values of ~32 μC/cm 2 , increasing with Ti substitution. Depolarization by the hydrostatic pressure induced FE-AFE phase transition was drastically affected by variation of the Ti and Nb substitution, increasing at a rate of 113 MPa / 1% Ti and 21 MPa / 1% Nb. Total depolarization output was insensitive to the change in Ti and Nb substitution, ~32.8 μC/cm 2 for the PSZT ceramics. The R3c-R3m and R3m-Pm3m phase transition temperatures on heating ranged from 90 to 105°C and 183 to 191°C, respectively. Ti substitution stabilized the R3c and R3m phases to higher temperatures, while Nb substitution stabilized the Pm3m phase to lower temperatures. Thermal hysteresis of the phase transitions was also observed in the ceramics, with transition temperature on cooling being as much as 10°C lower.

36 MATERIALS SCIENCE↗
NASA NTRS1982

Development of Fe-Mn-Al-X-C alloys

Development of a low cost Cr-free, iron-base alloy for aerospace applications involves both element substitution and enhancement of microstructural strengthening. When Mn is substituted for Ni and Al or Si is substituted for Cr, large changes occur in the mechanical and thermal stability of austenite in FeMnAlC alloys. The in situ strength of MC or M2C (M = Ti, V, Hf, Ta, or Mo) in FeMnAlC alloys was determined. The high temperature tensile strength depends more on the distribution of carbides than the carbide composition. Precipitation of a high volume percent-ordered phase was achieved in Fe2OMnlONi6Al6Ti (lC) alloys. As case, these alloys have a homogeneous austenitic structure. After solutioning at 1100 C for 5 hr followed by aging at 600 C for 16 hr, gamma prime or a perovskite carbide is precipitated. Overaging occurs at 900 C where eta is precipitated.

Schuon, S. R.↗
NASA NTRS1985

Real-time SEM studies in controlled reactive atmospheres

A unique scanning electron accessory has been developed that allows the observation of specimens under partial pressures of any gas. The sample is placed in a metal support boat inside a special sample holder. The sample in the boat is imaged on a CRT and is simultaneously recorded on a videotape, allowing the reaction between the sample and the gas to be observed in real time. Sample changes can be seen continuously as the sample is being heated or cooled. This process allows the observation of material transformations such as phase changes as they happen. Temperatures as high as 1000 C have been used and are continuously monitored using a thermocouple with a digital display on the CRT and videotape. X-ray analyses can also be run before and after any reactions. In the study described here, thick-film screen-printing inks using molybdenum/tin compositions as a replacement for silver were developed to be used on terrestrial photovoltaic cells. Pieces were placed on the sample stage and heated in both O2 and H2 atmospheres. The results were used to determine the most effective frits to be used in the thick-film inks.

Gallagher, B. D.↗
NASA NTRS1986

Concentrated mass effects on the flutter of a composite advanced turboprop model

The effects on bending-torsion flutter due to the addition of a concentrated mass to an advanced turboprop model blade with rigid hub are studied. Specifically the effects of the magnitude and location of added mass on the natural frequencies, mode shapes, critical interblade phase angle, and flutter Mach number are analytically investigated. The flutter of a propfan model is shown to be sensitive to the change in mass distribution. Static unbalance effects, like those for fixed wings, were shown to occur as the concentrated mass was moved from the leading edge to the trailing edge with the exception of one mass location. Mass balancing is also inferred to be a feasible method for increasing the flutter speed.

Ramsey, J. K.↗
NASA NTRS1989

Theoretical predictions of volatile bearing phases and volatile resources in some carbonaceous chondrites

Carbonaceous chondrites are usually believed to be the primary constituents of near-Earth asteroids and Phobos and Diemos, and are potential resources of fuels which may be exploited for future planetary missions. The nature and abundances are calculated of the major volatile bearing and other phases, including the vapor phase that should form in C1 and C2 type carbonaceous chondrites as functions of pressure and temperature. The results suggest that talc, antigorite plus or minus magnesite are the major volatile bearing phases and are stable below 400 C at 1 bar in these chondritic compositions. Simulated heating of a kilogram of C2 chondrite at fixed bulk composition between 400 and 800 C at 1 bar yields about 135 gm of volatile, which is made primarily of H2O, H2, CH4, CO2 and CO. The relative abundances of these volatile species change as functions of temperature, and on a molar basis, H2 becomes the most dominant species above 500 C. In contrast, Cl chondrites yield about 306 gm of volatile under the same condition, which consist almost completely of 60 wt percent H2O and 40 wt percent CO2. Preliminary kinetic considerations suggest that equilibrium dehydration of hydrous phyllosilicates should be attainable within a few hours at 600 C. These results provide the framework for further analyses of the volatile and economic resource potentials of carbonaceous chondrites.

Ganguly, Jibamitra↗
NASA NTRS2003

Experimental Simulation of Shock Reequilibration of Fluid Inclusions During Meteorite Impact

Fluid inclusions are microscopic volumes of fluid trapped within minerals as they precipitate. Fluid inclusions are common in terrestrial minerals formed under a wide array of geological settings from surface evaporite deposits to kimberlite pipes. While fluid inclusions in terrestrial rocks are the rule rather than the exception, only few fluid inclusion-bearing meteorites have been documented. The rarity of fluid inclusions in meteoritic material may be explained in two ways. First, it may reflect the absence of fluids (water?) on meteorite parent bodies. Alternatively, fluids may have been present when the rock formed, but any fluid inclusions originally trapped on the parent body were destroyed by the extreme P-T conditions meteorites often experience during impact events. Distinguishing between these two possibilities can provide significant constraints on the likelihood of life on the parent body. Just as textures, structures, and compositions of mineral phases can be significantly altered by shock metamorphism upon hypervelocity impact, fluid inclusions contained within component minerals may be altered or destroyed due to the high pressures, temperatures, and strain rates associated with impact events. Reequilibration may occur when external pressure-temperature conditions differ significantly from internal fluid isochoric conditions, and result in changes in fluid inclusion properties and/or textures. Shock metamorphism and fluid inclusion reequilibration can affect both the impacted target material and the meteoritic projectile. By examining the effects of shock deformation on fluid inclusion properties and textures we may be able to better constrain the pressure-temperature path experienced by shocked materials and also gain a clearer understanding of why fluid inclusions are rarely found in meteoritic samples.

Madden, M. E. Elwood↗
NASA NTRS2004

Joint Development of a Fourth Generation Single Crystal Superalloy

A new, fourth generation, single crystal superalloy has been jointly developed by GE Aircraft Engines, Pratt & Whitney, and NASA. The focus of the effort was to develop a turbine airfoil alloy with long-term durability for use in the High Speed Civil Transport. In order to achieve adequate long-time strength improvements at moderate temperatures and retain good microstructural stability, it was necessary to make significant composition changes from 2nd and 3rd generation single crystal superalloys. These included lower chromium levels, higher cobalt and rhenium levels and the inclusion of a new alloying element, ruthenium. It was found that higher Co levels were beneficial to reducing both TCP precipitation and SRZ formation. Ruthenium caused the refractory elements to partition more strongly to the ' phase, which resulted in better overall alloy stability. The final alloy, EPM 102, had significant creep rupture and fatigue improvements over the baseline production alloys and had acceptable microstructural stability. The alloy is currently being engine tested and evaluated for advanced engine applications.

Walston, S.↗
NASA NTRS2005

Thermal Conductivity of Alumina-reinforced Zirconia Composites

10-mol% yttria-stabilized zirconia (10SZ) - alumina composites containing 0-30 mol% alumina were fabricated by hot pressing at 1500 C in vacuum. Thermal conductivity was determined at various temperatures using a steady-state laser heat flux technique. Thermal conductivity of the composites increased with increase in alumina content. Composites containing 0, 5, and 10-mol% alumina did not show any change in thermal conductivity with temperature. However, those containing 20 and 30-mol% alumina showed a decrease in thermal conductivity with increase in temperature. The measured values of thermal conductivity were in good agreement with those calculated from the Maxwell-Eucken model where one phase is uniformly dispersed within a second major continuous phase.

Bansal, Narottam P.↗
DOE OSTI2026

Increases in Cell-Wall Homogalacturonan but Decreases in Xylogalacturonan Accompany Transition from Dormant to Vegetative Stages in Chrysolaena Obovata Rhizophores

The rhizophores of Chrysolaena obovata, a perennial herb native to the Brazilian Cerrado, are underground storage organs that accumulate fructans and support vegetative propagation. Here, we investigated how the content of fructans and the composition of rhizophore cell wall polysaccharides change across developmental stages and contribute to seasonal adaptation. In addition to the accumulation of fructans in vacuoles (~26-55% of the dry mass according to the developmental stage), cell-wall polysaccharide composition changed throughout the growth cycle, reflecting structural adjustments linked to developmental and environmental cues. These cell walls have a type I architecture, typical of eudicots. Although total pectin content remained stable, homogalacturonans increased in proportion during the transition from dormant to vegetative stages, whereas amounts of xylogalacturonans decreased. Xylogalacturonans accumulate within the middle lamella during the dormant phase and are potentially associated with flexibility and water retention. Hemicelluloses consisted mainly of low-substituted arabinoxylans and xyloglucan, consistent with a secondary cell wall profile. Xylans decreased slightly in the transition from the dormant to vegetative stage, while xyloglucan proportions increased. Overall, our findings show that seasonal metabolic changes in C. obovata involve dynamic modifications of rhizophore cell wall polysaccharides, which contribute to organ development and drought adaptation throughout the seasonal cycle.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Computationally Predicted High-Throughput Free-Energy Phase Diagrams for the Discovery of Solid-State Hydrogen Storage Reactions

The design of multinary solid-state material systems that undergo reversible phase changes via changes in temperature and pressure provides a potential means of safely storing hydrogen. However, fully mapping the stabilities of known or newly targeted compounds relative to competing phases at reaction conditions has previously required many stringent experiments or computationally demanding calculations of each compound’s change in Gibbs energy with respect to temperature, G(T). Here, we have extended the approach of constructing chemical potential phase diagrams based on ΔG f (T) to enable the analysis of phase stability at non-zero temperatures. We first performed density functional theory calculations to compute the formation enthalpies of binary, ternary, and quaternary compounds within several compositional spaces of current interest for solid-state hydrogen storage. Temperature effects on solid compound stability were then accounted for using our recently introduced machine learned descriptor for the temperature-dependent contribution G δ (T) to the Gibbs energy G(T). From these Gibbs energies, we evaluated each compound’s stability relative to competing compounds over a wide range of conditions and show using chemical potential and composition phase diagrams that the predicted stable phases and H2 release reactions are consistent with experimental observations. This demonstrates that our approach rapidly computes the thermochemistry of hydrogen release reactions for compounds at sufficiently high accuracy relative to experiment to provide a powerful framework for analyzing hydrogen storage materials. This framework based on G(T) enables the accelerated discovery of active materials for a variety of technologies that rely on solid-state reactions involving these materials.

08 HYDROGEN↗
DOE OSTI2025

Nanoscopic strain evolution in single-crystal battery positive electrodes

Single-crystal Ni-rich layered oxides (SC-NMC) with a grain-boundary-free configuration have effectively addressed the long-standing cracking issue of conventional polycrystalline Ni-rich materials (PC-NMC) in lithium-ion batteries, prompting a shift in optimization strategies. However, continued reliance on anisotropic lattice volume change—a well-established failure indicator in PC-NMC—as a metric for understanding strain and guiding compositional design for SC-NMC becomes controversial. Here, in this study, by leveraging multiscale diagnostic techniques, we unravelled the distinct nanoscopic strain evolution in SC-NMC during battery operation, challenging the conventional composition-driven strategies and mechanical degradation indicators used for PC-NMC. Through particle-level chemomechanical analysis, we reveal a decoupling between mechanical stability and lattice volume change in SC-NMC, identifying that structural instability in SC materials is primarily driven by multidimensional lattice distortions induced by kinetics-driven reaction heterogeneity and progressively deactivating chemical phases. Using this mechanical failure mode, we redefine the roles of cobalt and manganese in maintaining mechanical stability. Unlike cobalt’s detrimental role in PC-NMC, we find cobalt to be critical in enhancing the longevity of SC-NMC by mitigating localized strain along the extended diffusion pathway, whereas manganese exacerbates mechanical degradation.

36 MATERIALS SCIENCE↗