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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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Additive manufacturing of complexly shaped SiC with high density via extrusion-based technique – Effects of slurry thixotropic behavior and 3D printing parameters

Here, additive manufacturing of dense SiC parts was achieved via an extrusion-based process followed by electrical-field assisted pressure-less sintering. The aim of this research was to study the effect of the rheological behavior of SiC slurry on the printing process and quality, as well as the influence of 3D printing parameters on the dimensions of the extruded filament, which are directly related to the printing precision and quality. Different solid contents and dispersant- Darvan 821A concentrations were studied to optimize the viscosity, thixotropy and sedimentation rate of the slurry. The optimal slurry was composed of 77.5 wt% SiC, Y 2 O 3 and Al 2 O 3 powders, 0.25 wt% dispersant and 0.01 wt% defoamer. The printing parameters studied included extrusion pressure, nozzle size, layer height and printing speed; the one that had the most prominent effect on filament width and height was indicated as layer height. The nozzle inner diameter of 1.04 mm, speed of 350 mm/min, layer height of 0.7 mm and extrusion air pressure of 0.31 MPa were the optimal printing parameters. Furthermore, the relationship between the printing parameters and the filament dimensions was successfully predicted by using machine learning and grey system theory. Finally, the relative density of the printed SiC parts sintered at 1900 oC reached 94.7±1.5%.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Cyclic oxidation behavior of selected commercial NiCr-alloys for engine exhaust valves in wet air environment between 800 and 950 °C

In this work, the impact of water vapor on the cyclic oxidation behavior of four commercial Ni-based superalloys (N80A, N90, R41 and H282) was investigated between 800 and 950°C. Oxidation- and volatilization-induced Cr loss accelerated the transition from protective and adherent oxide formation (Cr 2 O 3 ) to mixed oxides that significantly spalled at 950°C for H282 and R41. The accelerated oxidation, Cr depletion, and spallation susceptibility for R41 and to a lesser extent for H282 compared to N80A and N90 was related to the higher fraction of γ’, which led to increased Ti incorporation into the Cr 2 O 3 scale in the presence of water vapor.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Effect of exposure temperature on the corrosion behavior of a FeNiCrCuAl high entropy alloy in supercritical water

The corrosion behavior of a FeNiCrCuAl high entropy alloy exposed to supercritical water at 380–650 °C and 25 MPa was investigated. The weight gain exhibited a nearly parabolic kinetics. At 380 °C, Al 2 O 3 precipitated on Fe 3 O 4 particles in FeCr-rich regions and intensified as the temperature increased to 650 °C, eventually resulting in an Al 2 O 3 particle. A mixed Fe 3 O 4 and NiAl 2 O 4 outer layer developed on NiAl-rich regions at 380 °C, whereas an Al 2 O 3 layer formed at 650 °C. Cu 2 O formed along the boundaries of NiAl-rich regions, regardless of exposure temperatures. In conclusion, the corrosion mechanism at different temperatures was elucidated.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Chickpea protein hydrolysate as a novel plant-based cryoprotectant in frozen surimi: Insights into protein structure integrity and gelling behaviors

Chickpea protein (CP) and its enzymatic hydrolysates are one of the most widely consumed pulse ingredients manifesting versatile applications in food industry, such as binders, emulsifiers, and meat protein substitutes. Other than those well-known functionalities, however, the use of CP as a cryoprotectant remained unexplored. Here, in this study, we prepared the chickpea protein hydrolysate (CPH) and investigated its cryoprotective effects to frozen surimi in terms of the protein structure integrity and gelling behaviors. Results indicated that CPH could inhibit myofibrillar protein (MP) denaturation and oxidation during the freeze–thaw cycling, as evidenced by their increased solubility, Ca 2+ -ATPase activity, sulfhydryl concentration, and declined content of disulfide bonds, carbonyl concentration and surface hydrophobicity. Freezing-induced changes on MP secondary structures were also retarded. Moreover, gels prepared from CPH-protected frozen surimi demonstrated more stabilized microstructure, uniform water distribution, enhanced elasticity, gel strength and water holding capacity. The CPH alone, at a reducing addition content of 4% (w/w), exhibited comparable cryoprotective performance to that of the commercial formulation (4% sucrose and 4% sorbitol). Therefore, this study provides scientific insights for development of pulse proteins as novel and high-performance food cryoprotectants.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Electrical, thermal, and H 2 O and CO 2 poisoning behaviors of PrNi 0.5 Co 0.5 O 3-δ electrode for intermediate temperature protonic ceramic electrochemical cells

PrNi 0.5 Co 0.5 O 3-δ (PNC) exhibits adequate total electrical conductivity (~300 S/cm at 400–600 °C) and moisture has no significant effect on it. The thermal expansion coefficient of PNC is 17.6 × 10 –6 /K by dilatometry and 18.43 × 10 –6 /K by in situ XRD. PNC also demonstrates chemical stability against H 2 O and CO 2 . However, PNC symmetrical cell over proton-conducting BaZr 0.4 Ce 0.4 Y 0.1 Yb 0.1 O 3-δ (BZCYYb4411) electrolyte shows significant H 2 O and CO 2 poisoning when those are introduced into O 2 –N 2 mixture. In comparison, symmetrical cells with PNC electrode over the oxygen ion conducting Ce 0.9 Gd 0.1 O 2-δ (GDC) electrolyte show no H 2 O and CO 2 poisoning under similar conditions. Here, it is hypothesized that poisoning from H 2 O and CO 2 of the PNC proton conducting symmetrical cell is caused by their adsorption on the BZCYYb4411 electrolyte instead of PNC electrode. Such a hypothesis is supported by the H 2 O and CO 2 adsorption behaviors on PNC and BZCYYb4411 powder surfaces, as measured by temperature programmed desorption (TPD).

08 HYDROGEN↗
DOE OSTI2024

An in-situ view cell system for investigating swelling behavior of elastomers upon high-pressure hydrogen exposure

The transition to hydrogen as a clean and efficient energy carrier is impeded by challenges in the compatibility of hydrogen with materials used within hydrogen infrastructure. Elastomers, crucial in sealing components, often exhibit premature failures in high-pressure hydrogen environments due to excessive swelling. This study employs an innovative in-situ view cell system to assess the swelling behavior of hydrogenated nitrile butadiene rubber (HNBR) under various hydrogen conditions. The system, designed to withstand pressures up to 96.5 MPa, incorporates Digital Image Correlation (DIC) for strain measurements and volume estimation. Results reveal non-linear volume increases during depressurization, challenging conventional assumptions. Furthermore, investigations into peak hydrogen pressures and pressure-holding scenarios during decompression highlight complex swelling trends. The introduction of a novel computer vision (CV) method enhances precision in volume estimation, overcoming DIC limitations. The study provides insights into mitigating elastomer swelling, crucial for developing robust materials to support future hydrogen-driven energy systems.

Elastomer↗
DOE OSTI2023

Role of surface wetting on tribological behavior for laser nanotextured steel using ionic liquid lubricants

Here, this research evaluates the effect of surface wettability on the tribological performance through ball-on-flat tribology testing. The substrate material, M2 tool steel, is laser processed and then functionalized with fluorocarbon and nitrile chemistry to achieve distinct oleophobicity and oleophilicity, respectively, but with a similar nanoscale surface texture. The baseline lubricant is poly-alpha-olefin (PAO) oil, and ionic liquids (ILs) are used as additives for this study. The interaction between the nanoscale textured steel surface and ionic liquid-based oils is investigated. A set of reciprocating wear tests are performed to investigate the tribological behavior of the tribo-system consisting of the surface-engineered, flat M2 tool steel specimen and a standard, surface-polished steel ball. Results show that the oleophobic flat surface results in a lower friction, while the oleophilic surface modification leads to a better wear protection to the flat surface. Ammonium-based IL provides the highest friction reduction, while the phosphonium-based ILs provide an improved wear protection.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effects of crystallization on mechanical behavior and corrosion performance of a ductile Zr 68 Al 8 Ni8Cu 16 bulk metallic glass

Here, we studied the effects of heat treatment on the microstructures, crystallization kinetics, mechanical performance, and anti-corrosion behavior of a hypoeutectic Zr 68 Al 8 Ni 8 Cu 16 bulk metallic glass (BMG). Through annealing, the precipitated phases were crystalline Zr 2 Cu and Zr 2 Ni. The total crystallinity was determined to be 10% and 77% for the samples annealed at 673 K and 713 K, respectively. The partial crystallization of the alloy leads to a dramatic deterioration in the ductility as compared to the as-cast BMG. Furthermore, the decrease in the ductility was accompanied by an increase in the crystallinity. The as-cast Zr-based BMG exhibited a greater corrosion resistance in the HCl solution than that of the annealed alloy. The depletion in the Zr and Al cation fractions of the surface oxidation film, which resulted from the precipitation of reactive nanocrystalline phases from the glassy matrix, is responsible for the reduced corrosion resistance.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Determining the oxidation behavior of matrix graphite

This work presents the oxidation behavior of matrix graphite in air. Matrix graphite, graphite powder/flakes bonded by a small amount of non-graphitic carbon, surrounds coated fuel particles in order to form cylindrical fuel compacts (in prismatic core designs) or spheres (in pebble-bed reactor designs). This work focuses on oxidation tests conducted on two matrix graphite materials, one provided by Kairos Power and the other A3 matrix graphite. Some of the tests followed American Society for Testing and Materials (ASTM) oxidation testing standards using a vertical furnace system and others were performed in a thermogravimetric analyzer (TGA). It was determined that, at temperatures of 450 °C–700 °C, the oxidation rate of the Kairos matrix graphite follows the Arrhenius equation. In comparison with A3 matrix graphite, the Kairos matrix graphite shows better oxidation resistance at high temperatures (≥550 °C), but also a higher oxidation rate at low temperatures. Both the A3 matrix graphite and the Kairos matrix graphite materials may experience preferential oxidation of the partially graphitized binder. An oxygen penetration gradient was also observed when using the three characterization methods (i.e., optical microscope, x-ray tomography [XCT], and density profile by the lathe) enlisted in this research. In conclusion, the oxygen penetration depth increases with decreasing isothermal oxidation temperature, while the center of the oxidized samples (10% weight loss) remains almost untouched even at 500 °C.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Lifelike behavior of chemically oscillating mobile capsules

Inspired by the self-organization of unicellular species into multicellular organisms, we use theory and simulation to design a system of mobile, active microcapsules that produce chemicals according to a catalytic reaction network (CRN). In solution, the catalytic reactions generate a force that drives the flow of the surrounding fluid. The convective flow, in turn, transports the capsules to new chemical surroundings with each successive translation. Consequently, the chemical signal produced by a cluster of capsules is critically dependent on the proximity and spatial configuration of the neighboring capsules. If all of the capsules and chemical products involved in the CRN lie within sufficient proximity, then the system develops oscillatory behavior that drives the dynamic self-assembly of capsules into larger clusters that are capable of collective action. Finally, these simulations indicate potential chemo-mechanic mechanisms that enable single cellular units, such as ameba, to organize into multicellular life forms.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Precipitation behavior near shrinkage porosity in a large sand casting of Haynes 282 alloy

The precipitation behavior of L1 2 structure Ni 3 (Al,Ti)-type γ' precipitates near shrinkage porosity in a large sand casting of Haynes 282 alloy has been investigated by scanning/transmission electron microscopy in conjunction with energy dispersive x-ray spectroscopy. The experimental results revealed that in the carbonitride-rich region close to the shrinkage porosity, γ' precipitates could still form with comparable sizes though at lower volume density than those in the general cast Ni matrix. The resulting γ' precipitates had a very high Al/Ti ratio. Close to oxide-rich pore surfaces, an absence of γ' precipitates was observed due to Al and Ti depletion by forming Al oxides and Ti carbonitrides, respectively. This work suggests that Al rather than Ti plays a dominant role in the formation of γ' precipitates in porous regions in cast Haynes 282 alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Effects of fabric architectures on mechanical and damage behaviors in carbon/epoxy woven composites under multiaxial stress states

The mechanical properties and damage evolutions of carbon/epoxy woven fabric composites with three different fabric architectures, including one plain weave and two twill weave patterns, are experimentally investigated under multiaxial stress states. In particular, the effects of weave patterns are investigated by monotonic and cyclic off-axis tension tests. Both elastic modulus and strength degrade remarkably with increasing off-axis loading angle, while Poisson's ratio is much higher than that measured from on-axis tests and increases with loading strain gradually. Different fabric architectures show limited effects on the modulus and strength under multiaxial stress states, and they are well predicted by transformation equation and Tsai-Wu failure criteria, respectively. However, significantly different failure behaviors are observed in three fabric composites, and microstructure observation shows that fabric architecture affects the stress concentration and the damage development. Smaller crimp ratio and compacted structure postpone the damage development but result in more abrupt failure under multiaxial stress states.

36 MATERIALS SCIENCE↗
DOE OSTI2022

The mechanical behavior of metal-halide perovskites: Elasticity, plasticity, fracture, and creep

Wide ranging mechanical properties — elasticity, plasticity, fracture, and creep — most relevant to the mechanical reliability of perovskite solar cells (PSCs) are systematically investigated. High quality bulk single-crystals of the commonly studied metal-halide perovskites (MHPs) relevant to PSCs are fabricated and studied: CH 3 NH 3 PbBr 3 (MAPbBr 3 ) and CH 3 NH 3 PbI 3 (MAPbI 3 ). The first direct measurement of MHP Young's modulus (E) using uniaxial compression reveals E <100> of 13.1 ± 1.3 and 10.6 ± 1.0 GPa for MAPbBr 3 and MAPbI 3 , respectively. Further, the Vickers micro-hardness H (100) of MAPbBr 3 and MAPbI 3 is 0.54±0.02 GPa and 0.76±0.05 GPa, respectively. The Vickers micro-indentation fracture toughness K IC of MAPbBr 3 and MAPbI 3 is estimated at 0.20±0.03 MPa∙m 0.5 and 0.18±0.03 MPa∙m 0.5 , respectively. The stress-exponent, n, extracted from nanoindentation creep data is ~8 and ~10 for MAPbBr 3 and MAPbI 3 , respectively. The trends in these properties are discussed. These properties are best estimates and are recommended for use in future mechanical behavior and reliability analyses of MHPs and PSCs.

36 MATERIALS SCIENCE↗
DOE OSTI2022

In-situ synchrotron X-ray diffraction investigation on deformation behavior of Nb/NiTi composite during pre-straining process

The mechanisms responsible for deformation behavior in Nb/NiTi composite during pre-straining were investigated systematically using in-situ synchrotron X-ray diffraction, transmission electron microscopy and tensile test. It is shown that upon loading, the composite experiences elastic elongation and slight plastic deformation of B19', B2 and β-Nb phases, together with the forward stress-induced martensitic (SIM) transformation from B2 to B19'. Upon unloading, the deformation mechanisms of the composite mainly involve elastic recovery of B19', B2 and β-Nb phases, compression deformation of β-Nb phase and incomplete B19'→B2 reverse SIM transformation. In the tensile loading-unloading procedure, besides the inherent elastic deformation and SIM transformation, the (001) compound twins in B19' martensite can also be conducive to the elastic deformation occurring in B19'-phase of the composite. Therefore, this composite can exhibit a large recoverable strain after unloading owing to the elastic deformation, and the partially reversible and consecutive SIM transformation together with the (001) compound twins.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Effect of Gold Catalyst Surface Morphology on Wetting Behavior and Electrochemical CO 2 Reduction Performance in a Large-Area Zero-Gap Gas Diffusion Electrolyzer

We report catalyst surface area and wetting behavior are key factors in determining the performance of gas diffusion electrode (GDE) electrolyzers for electrochemical CO 2 reduction. In this work, we report the integration of sub-1 μm thick nanoporous gold (npAu) catalyst coatings into a large-area (25 cm 2 ) zero-gap electrolyzer. The npAu coatings were prepared by magnetron sputtering (MS) of thin AgAu alloy films on the microporous carbon layer of a gas diffusion layer (GDL) followed by Ag leaching. Compared to MS Au films of the same thickness, npAu catalyst coatings enable higher Faradaic efficiencies and improved catalyst stability for CO 2 -to-CO reduction with Faradaic efficiencies of up to 88% at 100 mA/cm 2 . For a 800 nm npAu coating, the device level energy efficiency for CO 2 to CO conversion reaches 45% (52% for CO + H 2 ) at 100 mA/cm 2 with a single pass CO 2 conversion efficiency of ~12%. Contact angle measurements reveal that npAu coatings provide a more hydrophobic electrode interface compared to MS Au coatings, suggesting that the more hydrophobic interfacial environment of npAu coatings helps mitigating electrode flooding which is associated with performance deterioration over time.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2022

Electrochemical Sodiation Mechanism in Magnetite Nanoparticle-Based Anodes: Understanding of Nanoionics-Based Sodium Ion Storage Behavior of Fe 3 O 4

We report electrochemical ion storage behaviors of Fe 3 O 4 nanoparticles, as a representative transition metal oxide for an environmentally benign and low-cost anode for a sodium-ion battery, are thoroughly investigated through a combination of electrochemical analysis and diagnostics of Fe 3 O 4 electrode cells, X-ray-based and spectroscopic analysis of material structure evolution as functions of depth of discharge (DoD) and state of charge (SoC), and first principle modeling. The gravimetric capacity is found to be 50 mA h/g for bulk Fe 3 O 4 (50 nm average crystallite size) and 100 mA h/g--about a tenth of the theoretical prediction for complete conversion--for Fe 3 O 4 nanoparticles (8.7 nm average particle size), respectively. A fundamental and mechanistic study of material evolution as functions of DoD and SoC shows that Fe 3 O 4 does not allow electrochemical incorporation of Na + ions into the empty cation positions of the inverse spinel structure, leading to our assertion that electrochemical intercalation of Na + ions to conversion of the Fe 3 O 4 anode in sodium-ion batteries is nonviable. A density functional theory investigation points to the impracticality of the intercalation of Na + ions into Fe 3 O 4 and further validates our experimental findings. We propose several possible mechanisms corresponding to the observed low capacity, including formation of solid electrolyte interphases with unfavorable properties and adsorption of Na + ions onto surfaces of nanoparticles and/or at heterointerfaces in Fe 3 O 4 composite electrodes in a NaPF 6 -based electrolyte system.

25 ENERGY STORAGE↗
DOE OSTI2023

Molecular-Dynamics Analysis of the Mechanical Behavior of Plasma-Facing Tungsten

We report a systematic computational analysis of the mechanical behavior of plasma-facing component (PFC) tungsten focusing on the impact of void and helium (He) bubble defects on the mechanical response beyond the elastic regime. Specifically, we explore the effects of porosity and He atomic fraction on the mechanical properties and structural response of PFC tungsten, at varying temperature and bubble size. We find that the Young modulus of defective tungsten undergoes substantial softening that follows an exponential scaling relation as a function of matrix porosity and He atomic content. Beyond the elastic regime, our high strain rate simulations reveal that the presence of nanoscale spherical defects (empty voids and He bubbles) reduces the yield strength of tungsten in a monotonically decreasing fashion, obeying an exponential scaling relation as a function of tungsten matrix porosity and He concentration. Our detailed analysis of the structural response of PFC tungsten near the yield point reveals that yielding is initiated by emission of dislocation loops from bubble/matrix interfaces, mainly 1/2<111> shear loops, followed by gliding and growth of these loops and reactions to form <100> dislocations. Furthermore, dislocation gliding on the <111>{211} twin systems nucleates 1/6<111> twin regions in the tungsten matrix. These dynamical processes reduce the stress in the matrix substantially. Subsequent dislocation interactions and depletion of the twin phases via nucleation and propagation of detwinning partials lead the tungsten matrix to a next deformation stage characterized by stress increase during applied straining. Furthermore, our structural analysis reveals that the depletion of twin boundaries (areal defects) is strongly impacted by the density of He bubbles at higher porosities. After the initial stress relief upon yielding, increase in the dislocation density in conjunction with decrease in the areal defect density facilitates the initiation of dislocation-driven deformation mechanisms in the PFC crystal.

36 MATERIALS SCIENCE↗
DOE OSTI2026

A Robotic High-Throughput Grid-Search Platform for Mapping Phase Behavior in Triblock Copolymer–Homopolymer Blends

We present a high-throughput experimental investigation of the phase behavior in triblock copolymers (PS-b-PB-b-PS and PS-b-PI-b-PS) and polystyrene (PS) homopolymer blends as a function of homopolymer molecular weight (MW) and blend ratio. Using a robotic thin-film processing platform (NOVA) integrated with Grazing Incidence Small-Angle X-ray Scattering (GISAXS) and Atomic Force Microscopy (AFM), we systematically mapped the order–disorder transition (ODT) boundaries and domain spacing evolution across a broad MW range (4.0–101.3 kDa) with varying homopolymer loadings (10% to 90%). The results reveal three distinct regimes: low-MW homopolymers, corresponding to the wet-brush regime produced only gradual domain swelling before disordering at high blend ratios (weight fraction); medium-MW homopolymers, corresponding to thedry-brush regime induced significant domain spacing increase up to 80% followed by earlier disordering, while high-MW homopolymers led to macrophase separation with minimal changes in domain spacing. Additionally, coarse-grained molecular dynamics simulations confirmed our experimental finding that in the low-MW region, the PS homopolymer uniformly distributed in the PS domain. These findings demonstrate that homopolymer molecular weight critically governs both the extent of domain swelling and the onset of disorder in triblock copolymer systems. This high-throughput platform enables the rapid mapping of composition–morphology relationships and can be integrated with AI/ML tools for designing next-generation nanostructured polymers.

36 MATERIALS SCIENCE↗