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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Investigation of Powder Processing, Heat Treating, and Texturing to Improve Gas Atomized alnico Magnets for use in Electric Drive Motors

Alnico permanent magnet materials have been proposed as a rare earth free permanent magnet alternative during an ongoing search to replace rare earth permanent magnets that are used for interior permanent magnet motors, a common motor found in electric vehicles. A powder processing approach was used to study two alnico alloys (Full-Co and lower cost Co-Lean, both with enhanced coercivity) to anticipate high volume manufacturing needed to supply millions of permanent magnets to interior permanent magnet motors. In this study the two alloys were gas atomized, compression molded, and solid-state sintered to fabricate near-final shape alnico magnets. The Full-Co displayed abnormal grain growth (resulting in >1 mm size grains) during sintering while the Co-Lean did not (~20 μm – 400 μm sized grains depending on the sintering hold times). Solid state grain alignment was used to promote a <001> textured (easy axis) microstructure to enhance magnetic properties, yet both alloys did not show predicted grain alignment behavior. Comparisons of the powder processing, microstructures, and magnetic properties of the two alloys will be discussed, as well as an evaluation as to why non-theoretical processing behavior of the Full-Co and Co-Lean alnico permanent magnets is occurring. Preliminary interior permanent magnet motor designs for alnico magnets are discussed, as this is the overarching objective for powder-based alnico permanent magnets.

Rinko, Emily↗
DOE OSTI2019

Evolution of Defect Properties and Texture During Tensile Deformation of Additively Manufactured 316L Stainless Steel Using In-situ Synchrotron X-ray Computed Microtomography and Diffraction

The ability of Additive Manufacturing to create complex 3D objects has attracted the attention of a wide variety of industries [1]. This in turn has led to detailed studies investigating the relationship between AM processing parameters and final part characteristics such as porosity and texture [2]. However little research has been done to study the effects of these subsequent characteristics on these parts’ performance [3]. In this study, 316L stainless steel samples were additively manufactured to have common AM defects. The samples were deformed plasticly while undergoing in-situ microtomography and diffraction measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2019

MINERALOGICAL AND TEXTURAL CONTROLS ON SHEAR STRENGTH, SLIP STABILITY AND PERMEABILITY OF FAULTS

Induced seismicity resulting from fluid injection into the subsurface related to water and CO2 disposal, hydraulic fracturing and the stimulation of geothermal reservoirs present an important societal concern. These human activities involve the injection of large volumes of pressurized fluid into the subsurface, potentially at high rates, raising local pore pressures and disturbing the pristine local stress regime by lowering effective normal stress on pre-existing faults and fractures. The reduction of effective normal stress may trigger fault/fracture reactivation and in some cases result in hazardous seismic ruptures. Effective management and engineering of anthropogenic seismic events requires substantial understanding in the mechanisms, especially for the controlling factors on coupled rheological and transport response, including fault shear strength, slip stability, and permeability evolution during such events. In this study, we explore the coupled rheological and transport response of faults and fractures during reactivation as controlled by two fundamental controlling properties, viz., mineralogy and textural features. We approach this problem through shear experiments on analog faults and fractures via laboratory and numerical experiments. Specifically, we investigate: (1) the influence of frictionally weak minerals (talc) in mixtures of mineral analogs featuring contrasting frictional properties, (2) the influence of iron oxide grain coatings on quartz aggregates, and (3) the influence of fracture roughness in mated fractures on the ensemble shear strength, slip stability, and permeability evolution during reactivation events. We address the following questions in this study: (1) how much and what distribution of frictionally weak minerals is required to induce significant weakening in faults consisting of a matrix of frictionally strong minerals, (2) how does a pre-imposed weak mineral layer influence the rheological and transport behavior of faults, (3) what is the influence of a trace amount of grain coating materials introduce on the coupled behavior of faults, and finally (4) how do asperity height and wave length control the ensemble behavior of faults. These questions are explicitly answered in the following.

58 GEOSCIENCES↗
DOE OSTI2020

Texture-inducible substrate

A texture-inducible substrate includes a backplate, a deformable membrane positioned in front of the backplate to form a gap therebetween, and a ferrofluid contained in the gap. The substrate also includes an electromagnet positioned on the backplate to induce, when activated, a local volume of the ferrofluid to expand in volume and increase in viscosity so as to locally deform and raise an adjacent section of the deformable membrane.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Domain Texture of the Orthorhombic Phase of La 2-x Ba x CuO 4

Bragg Coherent Diffraction Imaging (BCDI) experiments have been carried out at the Advanced Photon Source using a new cryostat system developed to achieve high mechanical stability and low vibrations. Here, we measured the (012) LTO Bragg peak which is unique to the low-temperature orthorhombic (LTO) phase of micron-sized crystals of the High-temperature Superconductor La 2-x Ba x CuO 4 (LBCO) to study the formation of structural domains. Each time the sample was cooled into the orthorhombic phase, the diffraction pattern of domains was different. Finally, this confirms the interpretation of pinning of the lower-temperature Charge Density Wave domains observed in coherent resonant X-ray speckle correlation analysis experiments.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Bedrock architecture, soil texture, and hyporheic zone characterization combining electrical resistivity and induced polarization imaging

The shallow (<15 m depth) subsurface environment of a short reach along a bedrock stream was investigated with electrical resistivity and induced polarization (IP) to map details of bedrock and soil sediments. The bedrock is mostly comprised of limestone, and is generally resistive compared to the overlying soil. The soil-bedrock interface was determined through a trial and error approach using a sharp boundary feature in the inversion model. The inferred bedrock surface determined from the inversions exhibited undulating patterns with troughs and ridges. A near continuous trough ran alongside the stream within the floodplain, and is suggestive of a paleochannel among other interpretations of this feature. The structure of the electrical resistivity above the bedrock showed small-scale elongated features. The chargeability from the IP method showed larger scale features. High values of chargeability were associated with the sediments in the floodplain, and low values were associated with bedrock, stream, and soil on the elevated banks above the stream. If the chargeability is associated with membrane polarization characteristic of clayey soils, then IP seems to highlight the mere existence of clay, while the resistivity may be more discernable of the relative proportion of clay. Vegetation differences may also explain the chargeability distribution, where parts of the survey with high chargeability had dense pine with no understory making the soils more organically rich.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Static and dynamic topological defects in the domain textures in the helical antiferromagnet Ni 2 ⁢CoTeO 6

Real-space Bragg coherent x-ray-diffractive imaging unveils the formation of bubble and stripe antiferromagnetic (AFM) phase domains on the surface of Ni 2 ⁢CoTeO 6 single crystal. The stripe domains exhibit dislocation-type topological defects. The defects typically form as defect-antidefect pairs and can be created or annihilated by temperature changes and local heating. Thermal fluctuations of the AFM domain walls are observed near the Néel temperature. Topological defect pairs dynamically form and disappear in the fluctuating state. These observations provide a real-space perspective on the dynamics of the AFM phase transition in a helical antiferromagnet. Finally, the remarkable tunability of AFM domain walls in a helical antiferromagnet underscores their potential for AFM spintronics applications.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Correlation between complex spin textures and the magnetocaloric and Hall effects in Eu⁢(Ga 1−𝑥 ⁢Al 𝑥 ) 4 (𝑥=0.9, 1)

Determining the electronic phase diagram of a quantum material as a function of temperature (𝑇) and applied magnetic field (𝐻) forms the basis for understanding the microscopic origin of transport properties, such as the anomalous Hall effect (AHE) and topological Hall effect (THE). For many magnetic quantum materials, including Eu⁢Al 4 , a THE arises from a topologically protected magnetic skyrmion lattice with a nonzero scalar spin chirality. We identified a square skyrmion lattice (sSkL) peak in Eu⁢(Ga 1−𝑥 ⁢Al 𝑥 ) 4 (𝑥=0.9) identical to the peak previously observed in Eu⁢Al 4 by performing neutron-scattering measurements throughout the phase diagram. Here, comparing these neutron results with transport measurements, we found that in both compounds the maximal THE does not correspond to the sSkL area. Instead of the maximal THE, the maximal magnetocaloric-effect boundaries better identify the sSkL lattice phase observed by neutron-scattering measurements. The maximal THE therefore arises from interactions of itinerant electrons with frustrated spin fluctuations in a topologically trivial magnetic state.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗