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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Energizing Robust Sulfur/Lithium Electrochemistry via Nanoscale-Asymmetric-Size Synergism

Sluggish redox kinetics and dendrite growth perplex the fulfillment of efficient electrochemistry in lithium–sulfur (Li–S) batteries. The complicated sulfur phase transformation and sulfur/lithium diversity kinetics necessitate an all-inclusive approach in catalyst design. Herein, a compatible mediator with nanoscale-asymmetric-size configuration by integrating Co single atoms and defective CoTe 2–x (Co SA -CoTe 2–x @NHCF) is elaborately developed for regulating sulfur/lithium electrochemistry synchronously. Substantial electrochemistry and theoretical analyses reveal that CoTe 2–x exhibits higher catalytic activity in long-chain polysulfide transformation and Li 2 S decomposition, while monodispersed Co sites are more effective in boosting sulfur reduction kinetics to regulate Li 2 S deposition. Such cascade catalysis endows Co SA -CoTe 2–x @NHCF with the all-around service of “trapping-conversion-recuperation” for sulfur species during the whole redox reaction. Furthermore, it is demonstrated by in situ transmission electron microscopy that initially formed electronic-conductive Co and ionic-conductive Li 2 Te provide sufficient lithiophilic sites to regulate homogeneous Li plating and stripping with markedly suppressed dendrite growth. Consequently, by coupling the Co SA -CoTe 2–x @NHCF interlayer and Li@Co SA -CoTe 2–x @NHCF anode, the constructed Li–S full batteries deliver superior cycling stability and rate performance, and the flexible pouch cell exhibits stable cycling performance at 0.3 C. In conclusion, the gained insights into the synergistic effect of asymmetric-size structures pave the way for the integrated catalyst design in advanced Li–S systems.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Artificial neural network prediction of self-diffusion in pure compounds over multiple phase regimes

Artificial neural networks (ANNs) were developed to accurately predict the self-diffusion constants for pure components in liquid, gas and super critical phases. The ANNs were tested on an experimental database of 6625 self-diffusion constants for 118 different chemical compounds. The presence of multiple phases results in a heavy skew in the distribution of diffusion constants and multiple approaches were used to address this challenge. First, an ANN was developed with the raw diffusion values to assess what the main drawbacks of this direct method were. The first approach for improving the predictions involved taking the log 10 of diffusion to provide a more uniform distribution and reduce the range of target output values used to develop the ANN. The second approach involved developing individual ANNs for each phase using the raw diffusion values. Results show that the log transformation leads to a model with the best self-diffusion constant predictions and an overall average absolute deviation (AAD) of 6.56%. The resultant ANN is a generalized model that can be used to predict diffusion across all three phases and over a diverse group of compounds. The importance of each input feature was ranked using a feature addition method revealing that the density of the compound has the largest impact on the ANN prediction of self-diffusion constants in pure compounds.

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

Nano-compositional imaging of the lanthanum silicide system at THz wavelengths

Terahertz scattering-type scanning near-field optical microscopy (THz-sSNOM) provides a noninvasive way to probe the low frequency conductivity of materials and to characterize material compositions at the nanoscale. However, the potential capability of atomic compositional analysis with THz nanoscopy remains largely unexplored. Here, we perform THz near-field imaging and spectroscopy on a model rare-earth alloy of lanthanum silicide (La–Si) which is known to exhibit diverse compositional and structural phases. We identify subwavelength spatial variations in conductivity that is manifested as alloy microstructures down to much less than 1 μ m in size and is remarkably distinct from the surface topography of the material. Signal contrasts from the near-field scattering responses enable mapping the local silicon/lanthanum content differences. These observations demonstrate that THz-sSNOM offers a new avenue to investigate the compositional heterogeneity of material phases and their related nanoscale electrical as well as optical properties.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Gamete expression of TALE class HD genes activates the diploid sporophyte program in Marchantia polymorpha

Eukaryotic life cycles alternate between haploid and diploid phases and in phylogenetically diverse unicellular eukaryotes, expression of paralogous homeodomain genes in gametes primes the haploid-to-diploid transition. In the unicellular chlorophyte alga Chlamydomonas, KNOX and BELL TALE-homeodomain genes mediate this transition. We demonstrate that in the liverwort Marchantia polymorpha, paternal (sperm) expression of three of five phylogenetically diverse BELL genes, MpBELL234, and maternal (egg) expression of both MpKNOX1 and MpBELL34 mediate the haploid-to-diploid transition. Loss-of-function alleles of MpKNOX1 result in zygotic arrest, whereas a loss of either maternal or paternal MpBELL234 results in variable zygotic and early embryonic arrest. Expression of MpKNOX1 and MpBELL34 during diploid sporophyte development is consistent with a later role for these genes in patterning the sporophyte. These results indicate that the ancestral mechanism to activate diploid gene expression was retained in early diverging land plants and subsequently co-opted during evolution of the diploid sporophyte body.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1984

Satellites of Saturn - Optical properties

Spacecraft and ground-based optical, radio and spectrophotometric data on the Saturn satellites are reviewed for clues as to the composition and microstructures of the objects. Minas, Enceladus, Tethys, Dione and Rhea have similar photometric phase integrals, with some diversion exhibited by Rhea. Hyperion is nearly the same color as Iapetus, which displays an overall hemispherical optical asymmetry. Water ice has been observed on many of the satellites and on small, cratered objects within the rings. The frost layers are more extensive than those detected on Jovian satellites. Titan has a methane atmosphere. Finally, Phoebe is suspected of being a captured, asteroidal body.

Cruikshank, D. P.↗
NASA NTRS1993

Cathodoluminescence properties of components in enstatite chondrites

As a group, the enstatite chondrites are notable by the extremely low FeO content of most of their silicates. This property predisposes many of these materials to emit Cathodoluminescence (CL). Since examination of the CL properties of meteoritic components in ordinary and carbonaceous chondrites have proven to be a useful technique, we have initiated a survey of the enstatite chondrites in order to better characterize the chemical and physical properties of their luminescing phases. Because of the diversity encountered in this study, it is first necessary to describe the number and types of materials observed to emit CL in these meteorites. Two CL techniques were used. First, the initial survey work was conducted at low magnification using a Nuclide (now MAAS) Luminoscope mounted to a Wild MP binocular microscope equipped for photomicroscopy. The beam conditions used were 14 +/- KeV and 7 +/- 1 milliamps, with the beam focussed to the diameter of the field of view of the microscope at 20x (appox. 1.25 cm). Photomosaics were produced for each section using Ecktar 1000 film and an exposure time of 15 to 30 seconds. Second, high magnification (400x) photos were obtained of individual components of interest by mounting a 35mm camera to the optical system of the Cameca Camebax microprobe located at the Johnson Space Center. Beam conditions used were 15 KeV and 600 nA. Ecktar 1000 film was also used, but exposure times of 6 minutes were necessary to produce a useful image. The components in E chondrites that produce CL can be divided into four broad categories. These are clasts and aggregates, chondrules, matrix components, and refractory objects. Components in each category are discussed.

Dehart, John M.↗
NASA NTRS2013

Initial Estimates of Optical Constants of Mars Candidate Materials

Data obtained at visible and near-infrared wavelengths by OMEGA on Mars Express and CRISM on MRO provide definitive evidence for the presence of phyllosilicates and other hydrated phases on Mars. A diverse range of both Fe/Mg-OH and Al- OH-bearing phyllosilicates were identified including the smectites, nontronite, saponite, and montmorillonite. To constrain the abundances of these phyllosilicates, spectral analyses of mixtures are needed. We report on our effort to enable the quantitative evaluation of the abundance of hydrated-hydroxylated silicates when they are contained in mixtures. We include two component mixtures of hydrated/ hydroxylated silicates with each other and with two analogs for other Martian materials; pyroxene (enstatite) and palagonitic soil (an alteration product of basaltic glass, hereafter referred to as palagonite). For the hydrated-hydroxylated silicates we include saponite and montmorillonite (Mg- and Al-rich smectites). We prepared three size separates of each end-member for study: 20-45, 63-90, and 125-150 micron.

Rousch, Ted L.↗
NASA NTRS2013

Implementation of a Wavefront-Sensing Algorithm

A computer program has been written as a unique implementation of an image-based wavefront-sensing algorithm reported in "Iterative-Transform Phase Retrieval Using Adaptive Diversity" (GSC-14879-1), NASA Tech Briefs, Vol. 31, No. 4 (April 2007), page 32. This software was originally intended for application to the James Webb Space Telescope, but is also applicable to other segmented-mirror telescopes. The software is capable of determining optical-wavefront information using, as input, a variable number of irradiance measurements collected in defocus planes about the best focal position. The software also uses input of the geometrical definition of the telescope exit pupil (otherwise denoted the pupil mask) to identify the locations of the segments of the primary telescope mirror. From the irradiance data and mask information, the software calculates an estimate of the optical wavefront (a measure of performance) of the telescope generally and across each primary mirror segment specifically. The software is capable of generating irradiance data, wavefront estimates, and basis functions for the full telescope and for each primary-mirror segment. Optionally, each of these pieces of information can be measured or computed outside of the software and incorporated during execution of the software.

Smith, Jeffrey S.↗
NASA NTRS1987

A new radar technique for satellite rainfall algorithm development

A potential new radar parameter was investigated for measuring rainfall, namely the summation of the phase shifts at horizontal and vertical polarizations due to propagation through precipitation. The proposed radar technique has several potential advantages over other approaches because it is insensitive to the drop size distribution and to the shapes of the raindrops. Such a parameter could greatly assist the development of satellite rainfall estimation algorithms by providing comparative measurements near the ground. It could also provide hydrologically useful information for such practical applications as urban hydrology. Results of the investigation showed that the parameters can not be measured by radar. However, a closely related radar parameter, propagation differential phase shift, can be readily measured using a polarization diversity radar. It is recommended that propagation differential phase shift be further investigated and developed for radar monitoring of rainfall using a polarization agile radar. It is also recommended that a prototype multiple frequency microwave link be constructed for attenuation measurements not possible by existing radar systems.

Jameson, Arthur R.↗
NASA NTRS2010

Characteristics of Precipitation, Cloud, and Latent Heating Associated with the Madden-Julian Oscillation

This study investigates the evolution of cloud and rainfall structures associated with Madden Julian oscillation (MJO) using Tropical Rainfall Measuring Mission (TRMM) data. Two complementary indices are used to define MJO phases. Joint probability distribution functions (PDFs) of cloud-top temperature and radar echo-top height are constructed for each of the eight MJO phases. The genesis stage of MJO convection over the western Pacific (phases 1 and 2) features a bottom-heavy PDF, characterized by abundant warm rain, low clouds, suppressed deep convection, and higher sea surface temperature (SST). As MJO convection develops (phases 3 and 4), a transition from the bottom-heavy to top-heavy PDF occurs. The latter is associated with the development of mixed-phase rain and middle-to-high clouds, coupled with rapid SST cooling. At the MJO convection peak (phase 5), a top-heavy PDF contributed by deep convection with mixed-phase and ice-phase rain and high echo-top heights (greater than 5 km) dominates. The decaying stage (phases 6 and 7) is characterized by suppressed SST, reduced total rain, increased contribution from stratiform rain, and increased nonraining high clouds. Phase 7, in particular, signals the beginning of a return to higher SST and increased warm rain. Phase 8 completes the MJO cycle, returning to a bottom-heavy PDF and SST conditions similar to phase 1. The structural changes in rain and clouds at different phases of MJO are consistent with corresponding changes in derived latent heating profiles, suggesting the importance of a diverse mix of warm, mixed-phase, and ice-phase rain associated with low-level, congestus, and high clouds in constituting the life cycle and the time scales of MJO.

Lau, K-M.↗
NASA NTRS2006

Mineralogy at Gusev Crater and Meridiani Planum from the Moessbauer Spectrometers on the Mars Exploration Rovers

The Moessbauer spectrometers on the twin MER rovers Spirit and Opportunity have provided significant new information on the distribution of iron among its oxidation states, the identification of the mineralogical composition of iron-bearing phases, and the distribution of iron among those phases for rock and soil at Gusev Crater and Meridiani Planum. The plains of Gusev Crater are dominated by olivine-bearing basalt (approximately Fo(60)) and Fe(3+)/Fe(total)=0.1 - 0.5. The oxide mineral generally present is magnetite. In contrast, initial results for the Columbia Hills are consistent with the presence of hematite and a ferrous iron phase, possibly pyroxene. Gusev spectra also have a ferric doublet (not jarosite) that is tentatively associated with nano-phase ferric oxide. A wider diversity of material is present at Meridiani Planum. Significantly, jarosite-bearing outcrop is present throughout the region, with good exposures in impact craters such as Eagle and Endurance (Fe(3+)/Fe (total) approx. 0.9). The Moessbauer identification of jarosite (a hydroxyl-bearing sulfate mineral) is evidence for aqueous, acid-sulfate processes on Mars. Hematite is observed within the outcrop matrix and in the spheroidal particles (Blueberries) found within the outcrop and as a surface lag. An isolated rock (Bounce Rock) was the only sample at either landing site whose iron-bearing phase was dominated by pyroxene. The basaltic sand in the central portion of Eagle crater, in the intercrater plains, and between slabs of outcrop at both Eagle and Endurance craters is olivine-bearing basalt. The widespread occurrence of olivine-bearing basalt at both MER landing sites implies that physical, rather than chemical, weathering processes dominate at the surface of contemporary Mars.

Morris, Richard V.↗
DOE OSTI2023

Investigation of grain size and geometrically necessary dislocation density dependence of flow stress in Mg-4Al by using nanoindentation

Models for grain size dependence of flow stress typically ignore contributions from geometrically necessary dislocations (GNDs) in the grain boundary regions. Ashby had proposed the following equation for flow stress (τ) as a function of grain size (d) and effective plastic strain ($\bar{ε}$): $τ = τ_{0} + C'G\sqrt{^{b\bar{ε}}_{d}}$ using an unknown empirical coefficient, C’, In this study, the coefficient, C’, and equation for the grain size dependence of flow stress were investigated in Mg-4Al using nanoindentation. C’ ranges from 1.4 to 7.11 that is related to the hardness difference (∆H0) between the adjacent grains as $C' + 0.62\sqrt{ΔH_{0}}$. Ashby equation was used to predict uniaxial stress-strain curves in grain sizes of 55 µm, 187 µm, and 333 µm. The results showed lower flow stress and lower hardening rate compared to experimentally measured tensile stress-strain response. The discrepancy seems to be a result of hardening effect of SSDs. Here, we propose a modified Ashby equation that takes into account the hardening effect of SSDs and GNDs separately, resulting in a better agreement between calculated and experimentally measured values. This analysis demonstrates estimation of uniaxial stress-strain response using nanoindentation measurements that captures effects of grain size, and strain hardening from SSDs and GNDs. The combination of the revised equation and nanoindentation method will enable rapid exploration of stress-strain response of a diverse range of single-phase polycrystalline alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Sampling lattices in semi-grand canonical ensemble with autoregressive machine learning

Calculating thermodynamic potentials and observables efficiently and accurately is key for the application of statistical mechanics simulations to materials science. However, naive Monte Carlo approaches, on which such calculations are often dependent, struggle to scale to complex materials in many state-of-the-art disciplines such as the design of high entropy alloys or multi-component catalysts. To address this issue, we adapt sampling tools built upon machine learning-based generative modeling to the materials space by transforming them into the semi-grand canonical ensemble. Furthermore, we show that the resulting models are transferable across wide ranges of thermodynamic conditions and can be implemented with any internal energy model U, allowing integration into many existing materials workflows. We demonstrate the applicability of this approach to the simulation of benchmark systems (AgPd, CuAu) that exhibit diverse thermodynamic behavior in their phase diagrams. Finally, we discuss remaining challenges in model development and promising research directions for future improvements.

36 MATERIALS SCIENCE↗
DOE OSTI2024

The integration of heterogeneous resources in the CMS Submission Infrastructure for the LHC Run 3 and beyond

While the computing landscape supporting LHC experiments is currently dominated by x86 processors at WLCG sites, this configuration will evolve in the coming years. LHC collaborations will be increasingly employing HPC and Cloud facilities to process the vast amounts of data expected during the LHC Run 3 and the future HL-LHC phase. These facilities often feature diverse compute resources, including alternative CPU architectures like ARM and IBM Power, as well as a variety of GPU specifications. Using these heterogeneous resources efficiently is thus essential for the LHC collaborations reaching their future scientific goals. The Submission Infrastructure (SI) is a central element in CMS Computing, enabling resource acquisition and exploitation by CMS data processing, simulation and analysis tasks. The SI must therefore be adapted to ensure access and optimal utilization of this heterogeneous compute capacity. Some steps in this evolution have been already taken, as CMS is currently using opportunistically a small pool of GPU slots provided mainly at the CMS WLCG sites. Additionally, Power9 processors have been validated for CMS production at the Marconi-100 cluster at CINECA. This note will describe the updated capabilities of the SI to continue ensuring the efficient allocation and use of computing resources by CMS, despite their increasing diversity. The next steps towards a full integration and support of heterogeneous resources according to CMS needs will also be reported.

Pérez-Calero Yzquierdo, Antonio↗
DOE OSTI2024

Topological and magnetic phase transitions in the bilayer Kitaev-Ising model

We investigate the phase diagram of a bilayer Kitaev honeycomb model with Ising interlayer interactions, deriving effective models via perturbation theory and performing Majorana mean-field theory calculations. We show that a diverse array of magnetic and topological phase transitions occur, depending on the direction of the interlayer Ising interaction and the relative sign of Kitaev interactions. When two layers have the same sign of the Kitaev interaction, a first-order transition from a Kitaev spin liquid to a magnetically ordered state takes place. The magnetic order points along the Ising axis and it is (anti)ferromagnetic for (anti)ferromagnetic Kitaev interactions. However, when two layers have opposite signs of the Kitaev interaction, we observe a notable weakening of magnetic ordering tendencies and the Kitaev spin liquid survives up to a remarkably larger interlayer exchange. Our mean-field analysis suggests the emergence of an intermediate gapped ℤ 2 spin-liquid state, which eventually becomes unstable upon vison condensation. The confined phase is described by a highly frustrated 120° compass model. We furthermore use perturbation theory to study the model with the Ising axis pointing along the $\hat{z}$ axis or lying in the 𝑥⁢𝑦 plane. In both cases, our analysis reveals the formation of one-dimensional Ising chains, which remain decoupled in perturbation theory, resulting in a subextensive ground-state degeneracy. Our results highlight the interplay between topological order and magnetic ordering tendencies in bilayer quantum spin liquids.

Kitaev model↗
DOE OSTI2024

Identifying Critical Mineral Binding Mechanisms and Distribution in Acid Mine Drainage Treatment Solids to Inform Targeted Recovery Methods

In this study, micro-X-ray Fluorescence and micro/bulk X-ray Adsorption Near Edge Spectroscopy were collected at Stanford Synchrotron Radiation Lightsource and the Advanced Photon Source to: (1) gain a detailed characterization of critical minerals in Fe/Mn (hydr)oxide host phases; and (2) investigate the Co/Ni coordination and redox speciation associated with Fe/Mn (hydr)oxides phases in AMD solids with diverse composition (e.g., Al-rich, Mn-rich, Al/Mn/Fe-rich). Preliminary results show co-location of Co/Ni within Mn-rich hotspots, while Fe-rich hotspots were associated with heavy REEs. In Al-rich solids, Mn speciation was mostly comprised of Mn+3/+4 oxides, while the Mn-rich solids contain predominately Mn+4. These results suggest the AMD matrix plays an important role in how Co/Ni are coordinated, which aids in evaluating the efficacy to utilize AMD solids as a resource, and informs other novel sorbent and recovery technologies.

Hoffman, Colleen↗
NASA NTRS2003

Atomistic Modeling of Nanostructures via the BFS Quantum Approximate Method

Ideally, computational modeling techniques for nanoscopic physics would be able to perform free of limitations on the type and number of elements, while providing comparable accuracy when dealing with bulk or surface problems. Computational efficiency is also desirable, if not mandatory, for properly dealing with the complexity of typical nano-strucured systems. A quantum approximate technique, the BFS method for alloys, which attempts to meet these demands, is introduced for the calculation of the energetics of nanostructures. The versatility of the technique is demonstrated through analysis of diverse systems, including multi-phase precipitation in a five element Ni-Al-Ti-Cr-Cu alloy and the formation of mixed composition Co-Cu islands on a metallic Cu(III) substrate.

Bozzolo, Guillermo↗
NASA NTRS2021

An Evolutionary System of Mineralogy. Part III: Primary Chondrule Mineralogy (4566 to 4561 Ma)

Information-rich attributes of minerals reveal their physical, chemical, and biological modes of origin in the context of planetary evolution, and thus they provide the basis for an evolutionary system of mineralogy. Part III of this system considers the formation of 43 different primary crystalline and amorphous phases in chondrules, which are diverse igneous droplets that formed in environments with high dust/gas ratios during an interval of planetesimal accretion and differentiation between 4566 and 4561 Ma. Chondrule mineralogy is complex, with several generations of initial droplet formation via various proposed heating mechanisms, followed in many instances by multiple episodes of reheating and partial melting. Primary chondrule mineralogy thus reflects a dynamic stage of mineral evolution, when the diversity and distribution of natural condensed solids expanded significantly.

Classification↗