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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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

On the Pressure Generated by Thermite Reactions Using Stress-Altered Aluminum Particles

Here we examine pressure build-up and decay in thermites upon impact ignition and interprets reactivity based on the holistic pressure history. The thermite is a mixture of aluminum (Al) combined with bismuth trioxide (Bi 2 O 3 ) powder. Four different Al particles sizes were examined that ranged from 100 nm to 18.5 μm mean diameter and for each size, two different Al powder treatments were examined: stress-altered compared to untreated, as-received Al powder. Stress-altered Al powders have been shown to be more reactive, such that the stress-altered Al powder thermites offer a metric for analyzing thermite reactivity in terms of pressure development compared to untreated Al powder. In a binary thermite system, multiple phase changes and interface chemistry influence the transient pressure response during reaction. Results reveal three key pressure metrics that need consideration specifically for thermite combustion: (1) delay time to peak pressure, (2) peak pressure, and (3) decay after peak pressure. Our experiments show that a lower peak pressure corresponds with higher thermite reactivity because aluminum consumption of oxygen generated by decomposing solid oxidizer reduces the peak pressure. Faster rates of reaction consume oxygen at higher rates such that pressure development becomes more limited than less reactive thermites and the result is a lower peak pressure. This conclusion is opposite of traditional studies using metal fuels with a gaseous environment that typically show higher peak pressures correspond with greater reactivity.

42 ENGINEERING↗
DOE OSTI2022

The Wormholes Within: A Study of 1, 3, 5–Triamino–2, 4, 6–Trinitrobenzene Crystal Morphology by Micro and Nano–Scale X–Ray Computed Tomography and its Effects Upon the Shock Sensitivity of Detonation

We report that we understand heterogeneous-explosive detonation only to the extent that we can first measure the salient chemical and microstructural features. Barring an inordinate amount of trial and error, we can tailor the detonation properties of our HE formulations only to the extent that we understand (at least qualitatively) the same effects. As an insensitive high explosive, 1, 3, 5-triamino-2, 4, 6-trinitrobenzene (TATB) burns more heterogeneously than conventional high explosives, making its detonation properties sensitive to microstructure. The Benziger route can produce various grain morphologies depending on the amount of water used in the amination step. So-called dry-aminated (DA) TATB crystals are riddled with a void structure called wormholes, which are washed out ammonium chloride (NH4Cl) inclusions that form during synthesis. So-called wet-aminated (WA) TATB crystals do not contain NH 4 Cl inclusions but possess a very convoluted external structure. Using both micro and nano-scale CT, we explore three DA-TATB lots that reflect evolutionary processing changes, plus one WA-TATB material. Micro CT imaged crystal collections show the exterior grain structure, revealing its roughness and providing a crude particle size measurement. The DA-TATB lots that test most sensitively in the LANL ECOT corner-turning test are roughest, having the appearance of being “corroded”. Nano-scale CT reveals both internal NH 4 Cl inclusions and void structures. The DA-TATB lots that tested intermediate and high sensitivity in ECOT exhibited similar wormhole structures, which were more extensive than that of the low-sensitivity lot. The least sensitive DA-TATB lot also retained more NH 4 Cl, consistent with reduced connectivity of voids to the surface.

1, 3, 5-triamino-2,4↗
DOE OSTI2021

Biosorption of copper from aqueous solutions utilizing agricultural wastes

Abstract The purpose of this study was to determine the copper (Cu) biosorption capacities of several agricultural wastes from aqueous solutions. Samples of agricultural wastes were tested unaltered and after hydrochloric acid (HCl) treatment. Additional parameters tested include sample dose, contact time, particle size, mixing temperature, and the concentrations and pH of the Cu solutions. Desorption studies were performed to determine if the removed Cu could be recovered. In addition, tests were conducted to determine if the agricultural waste samples (AWS) could be reused for additional Cu biosorption cycles. The results of this study demonstrate a wide range of Cu biosorption proficiencies ranging from 0% to 100% removal. The parameters that resulted in higher Cu removal include higher pH and lower Cu solution concentration. Desorption results showed a 58% to 86% Cu recovery rate. Three of the five reused AWS were effective at removing Cu during subsequent trials. Therefore, these AWS types can be reused for additional Cu biosorption cycles. Hence, it is possible that using those AWS for metal treatment could reduce hazardous waste disposal inefficiencies and costs by avoiding disposing of spent AWS following each Cu biosorption cycle.

Rizzuti, Anthony M.↗
DOE OSTI2020

Soil properties and biochemical composition of ground-dwelling bee nests in agricultural settings

Soils deliver underrecognized ecosystem services by supplying habitat for ground-dwelling pollinators, such as wild bees and other organisms, that pollinate 80% of insect-pollinated plants and play a critical role in securing resilient pollination provisions. Our objective is to identify soil properties of ground nesting bee nests in agricultural settings of western Oregon, USA. We confirmed ground nesting bee and sand wasp activity in 7 agricultural sites and 1 recreational park. Soils from 17 bee and sand wasp nests were analyzed for pH, particle size distribution, and carbon and nitrogen content. We visually confirmed that 8 of the nesting bees were sweat bees from the Halictidae family and identified a captured bee specimen as Lasioglossum (Dialictus) (Hymenoptera: Halictidae). We located 2 sites with sand wasps where specimens were identified as Cerceris and Bembix (Hymenoptera: Crabronidae). The organic matter composition of three soil samples scraped from the linings of active nests were assessed using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The FTICR-MS results identified unknown lipid compounds in the nest soil samples, which we hypothesize are waterproofing lipids secreted to line cell walls. Bee nests occurred in slightly acidic, bare-ground soils with low rock/vegetation coverage, low organic carbon content (<1%), and exhibited significantly higher silt-plus-clay fractions (>75%) versus data published for bee nests in prior work. Our findings present important implications for textural controls on nest site selection in wet, cool environments and demonstrate the importance of integrating soil properties to improve our understanding of ground-dwelling organisms and associated soil habitats.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Understanding Superatomic Ag Nanohydrides

Abstract Bulk Ag hydrides are extremely challenging to make even at very high pressures, but they may become stable as the particle size shrinks to the nanometer regime. Here, the formation and electronic structure of Ag nanohydrides are investigated from a superatomic perspective by density functional theory. It is found that as the coverage increases, adsorption energy of hydrogen atoms on Ag 38 cluster to form Ag 38 H 2 n nanohydride ( n is from 1 to 15) can be energetically favorable with respect to bare Ag 38 and H 2 . Furthermore, the adsorbed hydrogen atoms contribute their 1s electrons to the superatom electron count and behave as a metal instead of a ligand. The electronic structure of the silver nanohydrides follows the superatomic complex model, leading to magic or relatively more stable compositions such as Ag 38 H 2 , Ag 38 H 20 , and Ag 38 H 30 , which correspond to 40‐electron, 58‐electron, and 68‐electron shell closings, respectively. Angular momentum analyses of the superatomic orbitals suggest a convoluted interaction of geometry, symmetry, and orbital splitting.

He, Xiang↗
DOE OSTI2022

Molten-Salt Synthesis of O 3 -Type Layered Oxide Single Crystal Cathodes with Controlled Morphology towards Long-Life Sodium-Ion Batteries

Sodium layered oxides show great promise as affordable alternatives to lithium layered oxides, but their poor cycle life and air stability limit their practical potential. Micron-scale single crystals with greater packing density and lower surface area can overcome these challenges and improve performance compared to the traditional polycrystalline morphology. Herein, the authors present the synthesis of layered O 3 -type Na(Ni 0.3 Fe 0.4 Mn 0.3 )O 2 single-crystals with greatly improved cycle life and air stability. A molten-salt synthesis technique is adopted with excess sodium hydroxide to obtain platelet-like single crystals. Because the main mechanisms of both capacity fade and air degradation occur as a result of surface reactions at the opening of the sodium diffusion channels, particle morphology is found to be a critical metric for materials performance. More important than particle size or total surface area, the smaller proportion of exposed edge planes in the platelet morphology greatly reduces the amount of harmful surface reactions. Furthermore, the molten-salt method is found to eliminate the need for coprecipitated precursors and even form better morphology, starting from metal oxides instead of coprecipitated hydroxides.

25 ENERGY STORAGE↗
DOE OSTI2022

Non‐Linear Optical Properties of the ( RE ) 3 CuGeS 7 Family of Compounds

Abstract Non‐linear optical materials must possess a balanced combination of laser‐induced damage threshold (LDT) and second‐harmonic generation (SHG) and be phase matchable. In our previous work, chiral and polar La 3 CuGeS 7 was identified as a promising non‐linear optical material. Herein, we report the optimization of non‐linear optical properties through replacement of La with smaller lanthanides. It is determined that Gd 3 CuGeS 7 exhibits the best combination of SHG (1.6× AgGaS 2 at 88–105 μm particle size) and LDT (3× AgGaS 2 , 89 MW/cm 2 ) and is phase matchable. Based on changes in metal‐sulfur bond lengths and angles, we further propose structural optimization through solid‐solution formation and doping.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

NanoSIP: NanoSIMS Applications for Microbial Biology

High-resolution imaging with secondary ion mass spectrometry (nanoSIMS) has become a standard method in systems biology and environmental biogeochemistry and is broadly used to decipher ecophysiological traits of environmental microorganisms, metabolic processes in plant and animal tissues, and cross-kingdom symbioses. When combined with stable isotope-labeling—an approach we refer to as nanoSIP—nanoSIMS imaging offers a distinctive means to quantify net assimilation rates and stoichiometry of individual cell-sized particles in both low- and high-complexity environments. While the majority of nanoSIP studies in environmental and microbial biology have focused on nitrogen and carbon metabolism (using 15 N and 13 C tracers), multiple advances have pushed the capabilities of this approach in the past decade. The development of a high-brightness oxygen ion source has enabled high-resolution metal analyses that are easier to perform, allowing quantification of metal distribution in cells and environmental particles. New preparation methods, tools for automated data extraction from large data sets, and analytical approaches that push the limits of sensitivity and spatial resolution have allowed for more robust characterization of populations ranging from marine archaea to fungi and viruses. Further, NanoSIMS studies continue to be enhanced by correlation with orthogonal imaging and ‘omics approaches; when linked to molecular visualization methods, such as in situ hybridization and antibody labeling, these techniques enable in situ function to be linked to microbial identity and gene expression. Here we present an updated description of the primary materials, methods, and calculations used for nanoSIP, with an emphasis on recent advances in nanoSIMS applications, key methodological steps, and potential pitfalls.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2023

Experimental approach for development of a powder spreading metric in additive manufacturing

The powder spreading is a vital step of powder-based additive manufacturing (AM) processes. The quality of spread powder can considerably influence the properties of fabricated parts. Poorly packed powder beds with high surface roughness result in printed part layers with large porosity and low dimensional accuracy, leading to poor mechanical properties. Therefore, the powder spreadability and its dependence on process parameters and powder characteristics should be quantified to improve the efficiency of powder-based AM methods. This study proposes a novel dimensionless powder spreadability metric that can be commonly used in different powder-based AM processes. The quality of spread powder in terms of powder bed density and surface roughness was evaluated by adjusting the process parameters including recoating velocity and layer thickness, and powder characteristics including particle size distribution. In addition, the dynamic repose angle was proposed and examined as another powder spreadability metric. Furthermore, the results showed that these two proposed metrics were strongly correlated and lower recoating velocity and larger layer thickness led to higher spreadability and lower dynamic repose angle.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Fatigue behavior of low-cost, non-spherical Ti-6Al-4V powder processed via laser powder bed fusion

Hydride-dehydride Ti-6Al-4V powder with particle size distribution of 75–175 μm were used to manufacture fatigue samples. Optimized processing parameters were used to maintain a relative density of >99.5% in the samples. Fatigue tests were carried out in R = σ min /σ max = -1 condition under stresses ranging from 150 to 500 MPa and the results were compared to samples that were additively manufactured using spherical powders. The fatigue lives were similar between the two types of powder; i.e., powder morphology has no effect on fatigue performance. However, the high surface roughness and martensitic microstructure resulting from the laser powder bed fusion process result in poor performance compared to samples machined from conventionally produced materials. In conclusion, crack initiation occurred consistently from surface defects because of high surface roughness of the additively manufactured parts.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Mechanisms of mechanochemical synthesis of cesium lead halides: pathways toward stabilization of α-CsPbI 3

Cesium lead iodide with cubic perovskite structure (α-CsPbI 3 ) is gaining significant interest in photovoltaic applications due to its excellent absorbance of the visible solar light and other attractive optoelectronic properties. However, the synthesis of stable α-CsPbI 3 poses a significant challenge. Mechanochemical synthesis is emerging as a suitable method for the preparation of cesium lead halides. This work investigates the ball milling-induced synthesis of cesium lead halides perovskite phase using halide mixing or doping approaches. The synthesis in the CsI + PbI 2 , CsBr + PbBr 2 , CsBr + PbI 2 , and CsI + PbI 2 + NdI 3 mixtures and halide exchange reactions in the CsPbBr 3 + 3KI and CsBr + PbBr 2 + 3KI systems are investigated to elucidate the mechanism of this process. Then, CsPb(I 1–x Br x ) 3 and CsPb( 1–y )Nd y I 3 materials with different x and y ratios are prepared, and their stability is probed in the air using light absorption spectroscopy. These results suggest that Nd doping is more efficient in the stabilization of the perovskite structure than partial replacement of iodine with bromine. Microstructure observations reveal the existence of two different product formation mechanisms depending on the mechanical properties of reactants. The results reveal that the milling temperature has a significant impact on the reaction kinetics. Here, the produced particles nucleate and grow at the reactant interface and retard the synthesis reaction by creating a diffusion barrier. Extended milling reduces the product particle size and creates fresh contact between reactants, thus facilitating reaction completion.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A Solubility Comparison of Cyclotetramethylenetetranitramine (HMX) and Potential Mock-HMX Candidates in Solvents Relevant to Slurry Formulating Polymer-Bonded Materials

Understanding solubility behavior of organic crystalline materials is critical in the development of slurry-formulated plastic bonded composites. In the field of high explosives (HE), a common method for obtaining high density, greater than 95 % theoretical maximum density, is to encapsulate HE in a polymer matrix resulting in the formation of plastic bonded explosive (PBX) prills. Prill formation is highly nuanced and requires understanding of particle size distributions, solvent, antisolvent, and binder system as well as interactions thereof. In this paper, in an effort to create mock-HE that mimics HE in density and mechanical strength, solubility of candidate molecules was compared to cyclotetramethylenetetranitramine (HMX) in binder solvents relevant to prill formation. The results indicate that the mock candidates chosen for this study have different solubilities compared to HMX in water and both organic solvents, 2-butanone and ethyl acetate, investigated. With these solubility differences known, prills to match PBXs based on HMX can be formulated, pressed and tested.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Measurements of the emanation of 37Ar and 39Ar from irradiated rocks and powders

The emanation fraction of radionuclides has been highlighted as a known source of uncertainty in the estimation of radionuclide source signatures from underground nuclear tests and other nuclear activities, particularly in the case of activation products. A system was developed at Pacific Northwest National Laboratory to quantify the emanation fraction of argon from samples ranging in particle size from powder to small rocks. Seven materials, two powders and five rock types, were neutron irradiated and the emanation fraction of 37Ar was measured. Additional measurements were made of the 39Ar emanation for four of these materials.

Johnson, Christine M.↗
DOE OSTI2020

Metal Powder Recyclability in Binder Jet Additive Manufacturing

The recyclability of 316L stainless steel powder in the binder jetting process has been determined. The powder characterization results demonstrated a 22% increase in the number of coarse particles (> 30 µm) and an 18.2% reduction in the number of small particles (< 10 µm) after recycling up to 16 times. A few elongated and irregular-shaped particles were found after recycling, possibly due to particle agglomeration during handling and sieving. Here, a negligible increase in the oxygen content by 0.036% was detected in the recycled powder. The density of sintered parts produced using recycled powder was approximately 1.5% lower than when using fresh powder due to the changes in the particle size distribution and the flowability of the powder caused by the changes in morphology. Final parts built using fresh and recycled powder showed similar hardness (155 ± 3 HV and 165 ± 9 HV) and yield strength (206 ± 16 MPa and 192 ± 10 MPa), respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Microstructure Generation via Generative Adversarial Network for Heterogeneous, Topologically Complex 3D Materials

Using a large-scale, experimentally captured 3D microstructure dataset, we implement the generative adversarial network (GAN) framework to learn and generate 3D microstructures of solid oxide fuel cell electrodes. The generated microstructures are visually, statistically, and topologically realistic, with distributions of microstructural parameters, including volume fraction, particle size, surface area, tortuosity, and triple phase boundary density, being highly similar to those of the original microstructure. These results are compared and contrasted with those from an established, grain-based generation algorithm (DREAM.3D). Importantly, simulations of electrochemical performance, using a locally resolved finite element model, demonstrate that the GAN generated microstructures closely match the performance distribution of the original, while DREAM.3D leads to significant differences. Finally, the ability of the generative machine learning model to recreate microstructures with high fidelity suggests that the essence of complex microstructures may be captured and represented in a compact and manipulatable form.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Investigation of Mechanical Properties of Parts Fabricated with Gas- and Water-Atomized 304L Stainless Steel Powder in the Laser Powder Bed Fusion Process

In this report the use of gas-atomized powder as the feedstock material for the Laser Powder Bed Fusion (L-PBF) process is common in the Additive Manufacturing (AM) community. Although gas-atomization produces powder with high sphericity, its relatively expensive production cost is a downside for application in AM processes. Water atomization of powder may overcome this limitation due to its low cost relative to the gas-atomization process. In this work, gas- and water-atomized 304L stainless steel powders were morphologically characterized through Scanning Electron Microscopy (SEM). The water-atomized powder had a wider particle size distribution and exhibited less sphericity. Measuring powder flowability using the Revolution Powder Analyzer (RPA) indicated that the water-atomized powder had less flowablility than the gas-atomized powder. Through examining the mechanical properties of L-PBF fabricated parts using tensile tests, the gas-atomized powder had significantly higher yield tensile strength and elongation than the water-atomized powder, however, their ultimate tensile strengths were not significantly different.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Structure-based mechanism and inhibition of cholesteryl ester transfer protein

Purpose of Review: Cholesteryl ester transfer proteins (CETP) regulate plasma cholesterol levels by transferring cholesteryl esters (CEs) among lipoproteins. Lipoprotein cholesterol levels correlate with the risk factors for atherosclerotic cardiovascular disease (ASCVD). This article reviews recent research on CETP structure, lipid transfer mechanism, and its inhibition. Recent Findings: Genetic deficiency in CETP is associated with a low plasma level of low-density lipoprotein cholesterol (LDL-C) and a profoundly elevated plasma level of high-density lipoprotein cholesterol (HDL-C), which correlates with a lower risk of atherosclerotic cardiovascular disease (ASCVD). However, a very high concentration of HDL-C also correlates with increased ASCVD mortality. Considering that the elevated CETP activity is a major determinant of the atherogenic dyslipidemia, i.e., pro-atherogenic reductions in HDL and LDL particle size, inhibition of CETP emerged as a promising pharmacological target during the past two decades. CETP inhibitors, including torcetrapib, dalcetrapib, evacetrapib, anacetrapib and obicetrapib, were designed and evaluated in phase III clinical trials for the treatment of ASCVD or dyslipidemia. Although these inhibitors increase in plasma HDL-C levels and/or reduce LDL-C levels, the poor efficacy against ASCVD ended interest in CETP as an anti-ASCVD target. Nevertheless, interest in CETP and the molecular mechanism by which it inhibits CE transfer among lipoproteins persisted. Insights into the structural-based CETP-lipoprotein interactions can unravel CETP inhibition machinery, which can hopefully guide the design of more effective CETP inhibitors that combat ASCVD. Summary: Individual-molecule 3D structures of CETP bound to lipoproteins provide a model for understanding the mechanism by which CETP mediates lipid transfer and which in turn, guide the rational design of new anti-ASCVD therapeutics.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Reductive catalytic fractionation of cotton stalks: catalytic strategy for tuning the selectivity of phenolic monomers

Pretreatment of lignocellulosic biomass is a primary step to delink lignin from the lignin-carbohydrate complex for bioethanol production and other value-added products. Presently, these processes yield lignin (technical) with significant structural changes compared to native lignin and make it difficult to valorize. Reductive catalytic fractionation (RCF) is an advanced pretreatment process to valorize native lignin to selective phenolic monomers before capitalizing on carbohydrates. Herein, cotton stalks (CS) were pretreated with ethanol: water mixture catalyzed by bimetallic, Ru-Ni/HY (RNY) and Ru-Fe/HY (RFY), and trimetallic, Ru-Fe-Ni/HY (RFNY), catalysts using the endogenously produced H 2 . The favorable catalytic properties of the RFNY catalyst, including high reducibility, acidity, metal dispersion, the synergistic effect of all the metals, and appropriate pore and particle size resulted in the highest catalytic activity. Maximum 92% delignification efficiency was achieved with 91% holocellulose retention. The extracted lignin after depolymerization in the same step produced a 19 wt.% yield of phenolic monomers. Increasing the duration of the reaction from 2 to 6 h increased the selectivity to saturated alkyl chain phenolics (1 to 16 wt.%) at the expense of hemicellulose (50 to 9%). The fate of carbohydrates left behind after the RCF (CS-RCF) process was analyzed through enzymatic saccharification and compared with raw CS and acid-pretreated CS. In conclusion, CS-RCF yielded maximum glucose yield (45 g/L) within an incubation period of 72 h.

09 BIOMASS FUELS↗