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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Solid state grain alignment of permanent magnets in near-final shape

Magnet microstructure manipulation in the solid state by controlled application of a sufficient stress in a direction during high temperature annealing in a single-phase region of heat-treatable magnet alloys, e.g., alnico-type magnets is followed by magnetic annealing and draw annealing to improve coercivity and saturation magnetization properties. The solid-state process can be termed highly controlled abnormal grain growth (hereafter AGG) and will make aligned sintered anisotropic magnets that meet or exceed the magnetic properties of cast versions of the same alloy types.

Anderson, Iver E.↗
DOE OSTI2022

Modulation of rice MPG1 activity to increase biomass accumulation, grain yield, and stress tolerance in plants

The invention provides methods for improving plant yield, biomass accumulation and stress tolerance. A novel AP2-like transcription factor MPG1, which when modulated impacts grain yield, biomass and abiotic and biotic stress tolerance when compared to non-modulated plants. The invention further provides methods using recombinant expression cassettes, host cells, transgenic plants and breeding methods using the same.

Bush, Daniel R.↗
DOE OSTI2022

Solid state grain alignment of permanent magnets in near-final shape

Magnet microstructure manipulation in the solid state by controlled application of a sufficient stress in a direction during high temperature annealing in a single-phase region of heat-treatable magnet alloys, e.g., alnico-type magnets is followed by magnetic annealing and draw annealing to improve coercivity and saturation magnetization properties. The solid-state process can be termed highly controlled abnormal grain growth (hereafter AGG) and will make aligned sintered anisotropic magnets that meet or exceed the magnetic properties of cast versions of the same alloy types.

Anderson, Iver E.↗
DOE OSTI2022

Metal stack templates for suppressing secondary grains in sca1n

A metal stack for templating the growth of AlN and ScAlN films is disclosed. The metal stack comprises one, two, or three layers of metal, each of which is compatible with CMOS post-processing. The metal stack provides a template that promotes the growth of highly textured c-axis {002} AlN and ScAlN films. The metal stacks include one or more metal layers with each metal layer having either a hexagonal {002} orientation or a cubic {111} orientation. If the metal stack includes two or more metal layers, the layers can alternate between hexagonal {002} and cubic {111} orientations. The use of ScAlN results in a higher piezoelectric constant compared to that of AlN for ScAlN alloys up to approximately 44% Sc. The disclosed metal stacks resulted in ScAlN films having XRD FWHM values of less than approximately 1.1° while significantly reducing the formation of secondary grains in the ScAlN films.

Esteves, Giovanni↗
DOE OSTI2024

GAMPix: a novel fine-grained, low-noise and ultra-low power pixelated charge readout for TPCs

Here, we report on the development of a novel pixel charge readout system, Grid Activated Multi-scale pixel readout (GAMPix), which is under development for use in the GammaTPC gamma ray instrument concept. GammaTPC is being developed to optimize the use of liquid argon time projection chamber technology for gamma ray astrophysics, for which a fine grained low power charge readout is essential. GAMPix uses a new architecture with coarse and fine scale instrumented electrodes to solve the twin problems of loss of measured charge after diffusion, and high readout power. Fundamentally, it enables low noise and ultra low power charge readout at the spatial scale limited by diffusion in a time projection chamber, and has other possibly applications, including future DUNE modules.

Shutt, Tom↗
DOE OSTI2023

Understanding grain boundary segregation under irradiation: A mesoscale modeling study

Grain boundaries (GBs) are an important component in the design of irradiation resistant materials as they play a crucial role as point defect sinks for non-equilibrium vacancies and self-interstitials. However, in the presence of sustained point defect fluxes, the coupled transport of atomic components with inherently different diffusivities often leads to radiation-induced segregation (RIS), with undesired effects on properties such as intergranular corrosion and stress-assisted cracking. In this talk, we investigate the fundamental mechanisms leading to GB segregation in BCC FeCr-based alloys using multiscale modeling and experiments. A phase-field model is employed to account for both thermodynamic and kinetic segregation mechanisms. The full Onsager transport matrix is derived using kinetic Monte Carlo, molecular dynamics, and kinetic cluster expansion (KineCluE) calculations. The thermodynamics of GB segregation is described via an atomic density-based modification to the CALPHAD free energy. The modeling predictions are then compared against segregation data from atom probe characterization for various temperatures, compositions, and neutron irradiation conditions. We will conclude by discussing the utility of the multiscale modeling approach to shed light on the fundamental mechanisms leading to solute-GB interaction.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Grain Boundary Segregation Suppresses Local Short‐Range Ordering in Nanocrystalline High‐Entropy Alloys

Multi-principal-element alloys like high-entropy alloys (HEAs) have potential applications in many engineering fields due to their unique mechanical/functional properties. While HEAs are generally considered random solid solutions, recent studies revealed that they are prone to short-range-ordering (SRO) due to the complex multi-pair-wise interactions among the constituent elements. Meanwhile, SROs' evolution can sometimes be deleterious, and it is necessary to have control over their evolution. Examining the AlCoCrFe-Zr model alloy, long-range ordering occurs following the expectation of enthalpic predictions. Advanced characterization techniques—transmission electron microscopy, high-energy synchrotron X-ray diffraction/pair distribution function, and atom probe tomography, reveal that SRO is suppressed in as-milled and GB-decorated NC-(AlCoCrFe)100-xZrx (x = 0–1.5 atomic %). Warren-Cowley coefficient calculations are further used to validate the suppression of SRO. Besides the low segregation enthalpies of Cr, Fe, and Zr, and the high-mixing enthalpy of Cr and Fe, the short diffusion path to GBs due to high-GB density in the NC-HEAs and the higher energy state of the GBs than the matrix promotes GB-segregation that further alters the matrix chemistry and consequently disfavors SRO formation within the matrix. Despite the GB-segregation of Cr, Fe, and Zr, the matrices and GBs remain in a random solid solution.

36 MATERIALS SCIENCE↗