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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Post-forming Room Temperature Brittle Fracture in a High-Strength Low-Alloy Steel Sheet After Various Forming Modes

The effects of various sheet forming modes on the post-forming room temperature fracture behavior of a 550-MPa yield strength high-strength low-alloy (HSLA) steel are investigated. In-plane biaxial stretching, plane strain (cold rolling), uniaxial tension, cylindrical cup drawing, and in-plane compression (IPC) are examined up to a von Mises effective prestrain ε{sub eff} = 0.7. Most of the results pertain to sub-size Charpy-type impact specimens prepared from the prestrained material. After sufficiently large prestrains, the fracture behavior is highly anisotropic. Low-energy fracture modes, namely cleavage and intergranular fracture, occur after all modes of prestraining along plane directions that are perpendicular to the principal compressive prestrain. These planes are parallel to the sheet surface after biaxial stretching and cold rolling and correspond to brittle splits extending into the primary, ductile fracture surface. After cup drawing, the brittle planes are oriented perpendicular to the circumferential compressive prestrain. This results in very low energy fractures propagating in the length direction of a fully drawn cup. After in-plane compression, brittle fracture occurs along planes that are perpendicular to the compression direction. The fracture toughness for a crack propagating along such a plane after IPC to ε{sub eff} = 0.38 was very low (12.7 MPa √m), much lower than in the undeformed condition (247 MPa√m). Changes in grain shape and in crystallographic texture caused by the various prestraining modes, as well as the microstructural damage at non-metallic inclusions and carbides, are examined to try to understand the fracture behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Crystal structure of danofloxacin mesylate (C 19 H 21 FN 3 O 3 )(CH 3 O 3 S)

The crystal structure of danofloxacin mesylate has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Danofloxacin mesylate crystallizes in space group P1 (#1) with a = 6.77474(8), b = 12.4973(4), c = 12.82826(28) Å, α = 84.8709(29), β = 87.7501(10), γ = 74.9916(4)°, V = 1044.723(11) Å 3 , and Z = 2. The protonation of the danofloxacin cations was established by the analysis of potential intermolecular interactions and differs from that expected from isolated-cation calculations. The crystal structure consists of alternating layers of cations and anions parallel to the ac-plane. There is parallel stacking of the oxoquinoline rings along the a-axis. The expected N–H∙∙∙O hydrogen bonds between the cations and anions are not present. Each cation makes an N–H∙∙∙O hydrogen bond with the other cation, resulting in zig-zag chains along the a-axis. Both cations have strong intramolecular O–H∙∙∙O hydrogen bonds. There are several C–H∙∙∙O hydrogen bonds between the danofloxacin cations and mesylate anions. The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®).

36 MATERIALS SCIENCE↗
DOE OSTI2023

A hybrid 3D/2D field response calculation for liquid argon detectors with PCB based anode plane

Liquid Argon Time Projection Chamber (LArTPC) technology is commonly utilized in neutrino detector designs. It enables detailed reconstruction of neutrino events with high spatial precision and low energy threshold. Its field response (FR) model describes the time-dependent electric currents induced in the anode-plane electrodes when ionization electrons drift nearby. An accurate and precise FR is a crucial input to LArTPC detector simulations and charge reconstruction. Established LArTPC designs have been based on parallel wire planes. It allows accurate and computationally economic two-dimensional (2D) FR models utilizing the translational symmetry along the direction of the wires. Recently, novel LArTPC designs utilize electrodes formed on printed circuit board (PCB) in the shape of strips with through holes. The translational symmetry is no longer a good approximation near the electrodes and a new FR calculation that employs regions with three dimensions (3D) has been developed. Extending the 2D models to 3D would be computationally expensive. Fortuitously, the nature of strips with through holes allows for a computationally economic approach based on the finite-difference method (FDM). In this paper, we present a new software package pochoir that calculates LArTPC field response for these new strip-based anode designs. This package combines 3D calculations in the volume near the electrodes with 2D far-field solutions to achieve fast and precise field response computation. We apply the resulting FR to simulate and reconstruct samples of cosmic-ray muons and 39 Ar decays from a Vertical Drift (VD) detector prototype operated at CERN. We find the difference between real and simulated data within 5%. Current state-of-the-art LArTPC software requires a 2D FR which we provide by averaging over one dimension and estimate that variations lost in this average are smaller than 7%.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Correlating dislocation structures to basal and prismatic slip bands near grain boundaries in tensile-tested Mg–4Al using a multiscale electron microscopy approach

Dislocation structures where basal and prismatic slip bands meet grain boundaries in tensile-tested Mg with 4 wt% Al (Mg–4Al) were studied using a multiscale electron microscopy approach to explore the assumptions made for the dislocation pileup theory: a) slip bands consist of dislocation arrays piling up near grain boundaries, and b) stress concentration in the adjacent grain is solely caused by dislocation pileup. After post-testing electron backscatter diffraction (EBSD) scans, focused-ion-beam (FIB) lift-out specimens were prepared from regions of interest so that the specimen plane is parallel to the bulk sample surface to allow for direct correlation between mesoscale and microscale characterization. High dislocation density and the dislocation arrays in the slip bands corroborated with the first assumption. Evidence of plastic deformation in all grains, however, showed that the second assumption was false. Additionally, dislocation structures including crystal rotation boundaries and dislocations dissociating to the basal plane provide additional stress relief mechanisms near grain boundaries that are not accounted for in many crystal plasticity models, which requires auxiliary models to more accurately predict the stress and strain distribution in a microstructure.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Kink mechanism in Cu/Nb nanolaminates explored by $\mathcal{in}$ $\mathcal{situ}$ pillar compression

We report Nano metallic laminates (NMLs) exhibit different failure modes depending on the loading conditions due to their mechanical anisotropies. Kinking is a typical failure mode in many NMLs compressed along a layer-parallel direction. However, a detailed description of the microstructure evolution during kink band (KB) formation and an in-depth understanding of the formation mechanisms are lacking. In this work, the KB process is investigated in Cu/Nb NMLs by in situ micro pillar compression in the scanning electron microscope (SEM) along a layer-parallel direction. Post-mortem S/TEM and transmission Kikuchi diffraction (TKD) analyses show that kink banding leads to significant microstructure changes characterized by an accumulation of geometrically necessary dislocations (GNDs) and of tilt geometrically necessary boundaries (GNBs) near KB boundaries (KBBs). The distinct microstructure evolution implies that KB formation is facilitated by the inhomogeneous microstructures resulting in constrained deformation modes. Specifically, dislocations active on slip planes nearly parallel to the interfaces make a major contribution to kink evolution after the onset of kinking. Once layer-parallel slip systems are activated, preexisting lattice dislocations and dislocations nucleating from interfaces will accumulate as GNDs near KBBs via the stochastic storage of lattice dislocations that have certain Burgers vectors. GNDs can further transform into GNBs via cross-slip and climb driven processes near the KBB. Furthermore, GNBs near KBBs can grow by incorporating more GNDs or by coalescence to accommodate the KB evolution. We further hypothesize that microstructural perturbations and their ensuing stresses can initiate KB formation in Cu/Nb NMLs.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Strain-induced alignment and phase behavior of blue phase liquid crystals confined to thin films

Here, we report on the influence of surface confinement on the phase behavior and strain-induced alignment of thin films of blue phase liquid crystals (BPs). Confining surfaces comprised of bare glass, dimethyloctadecyl [3-(trimethoxysilyl)propyl] ammonium chloride (DMOAP)-functionalized glass, or polyvinyl alcohol (PVA)-coated glass were used with or without mechanically rubbing to influence the azimuthal anchoring of the BPs. These experiments reveal that confinement can change the phase behavior of the BP films. For example, in experiments performed with rubbed-PVA surfaces, we measured the elastic strain of the BPs to change the isotropic–BPII phase boundary, suppressing formation of BPII for film thicknesses incommensurate with the BPII lattice. In addition, we observed strain-induced alignment of the BPs to exhibit a complex dependence on both the surface chemistry and azimuthal alignment of the BPs. For example, when using bare glass surfaces causing azimuthally degenerate and planar anchoring, BPI oriented with (110) planes of the unit cell parallel to the contacting surfaces for thicknesses below 3 μm but transitioned to an orientation with (200) planes aligned parallel to the contacting surfaces for thicknesses above 4 μm. In contrast, BPI aligned with (110) planes parallel to confining surfaces for all other thicknesses and surface treatments, including bare glass with uniform azimuthal alignment. Complementary simulations based on minimization of the total free energy (Landau–de Gennes formalism) confirmed a thickness-dependent reorientation due to strain of BPI unit cells within a window of surface anchoring energies and in the absence of uniform azimuthal alignment. In contrast to BPI, BPII did not exhibit thickness-dependent orientations but did exhibit orientations that were dependent on the surface chemistry, a result that was also captured in simulations by varying the anchoring energies. Overall, the results in this paper reveal that the orientations assumed by BPs in thin films reflect a complex interplay of surface interactions and elastic energies associated with strain of the BP lattice. The results also provide new principles and methods to control the structure and properties of BP thin films, which may find use in BP-templated material synthesis, and BP-based optical and electronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Enhanced negative energy with a massless Dirac field

Motivated by traversable wormhole constructions that require large amounts of negative energy, we explore constraints on the amount of negative energy that can be carried by a free Dirac field in a slab-shaped region between two parallel spatial planes. Specifically, we ask what is the minimum possible uniform energy density that can exist at some time, considering all possible states and all possibilities for the physics outside the slab. The vacuum state where we identify the two sides of the slab with antiperiodic boundary conditions gives one possible state with uniform negative energy, but we argue that states with more negative energy exist above 1+1 dimensions. Technically, we reduce the problem to studying a massive Dirac field on an interval in 1+1 dimensions and numerically search for states with uniform energy density in a lattice regulated model. We succeed in finding states with enhanced negative energy (relative to the antiperiodic vacuum) which also appear to have a sensible continuum limit. Our results for the mass-dependence of the minimum uniform energy density in 1+1 dimensions suggest that for a 3+1 dimensional massless Dirac fermion, it is possible to have states with arbitrarily large uniform negative energy density in an arbitrarily wide slab.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

In situ measurements of a homogeneous to heterogeneous transition in the plastic response of ion-irradiated <111> Ni microspecimens

We report on the use of quantitative in situ microcompression experiments in a scanning electron microscope to systematically investigate the effect of self-ion irradiation damage on the full plastic response of <111> Ni. In addition to the well-known irradiationinduced increases in the yield and flow strengths with increasing dose, we measure substantial changes in plastic flow intermittency behavior, manifested as stress drops accompanying energy releases as the driven material transits critical states. At low irradiation doses, the magnitude of stress drops reduces relative to the unirradiated material and plastic slip proceeds on multiple slip systems, leading to quasi-homogeneous plastic flow. In contrast, highly irradiated specimens exhibit pronounced shear localization on parallel slip planes, which we ascribe to the onset of defect free channels normally seen in bulk irradiated materials. Our in situ testing system and approach allows for a quantitative study of the energy release and dynamics associated with defect free channel formation and subsequent localization. As a result, this study provides fundamental insight to the nature of interactions between mobile dislocations and irradiation-mediated and damage-dependent defect structures.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Mechanochemical synthesis of finite particle of layered double hydroxide-acetate intercalation compound: Swelling, thin film and ion exchange

Acetate intercalated Mg-Al layered double hydroxide was successfully synthesized by the solid-state reactions between magnesium acetate and aluminum hydroxide as the starting materials using a planetary mil. The acetate intercalated Mg-Al layered double hydroxide prepared by the present solid-state reaction was finite particle and was processed into stable aqueous suspension with variable transparency and viscosity depending on the concentration. By drying the suspension on a substrate under nitrogen atmosphere, thin film (with the thickness of several micrometers) of the acetate intercalated Mg-Al layered double hydroxide with the basal plane oriented parallel to the substrate was obtained. The ion exchange ability of the film, which is as an advantage of the acetate form of layered double hydroxide, was shown by the ion exchange with coumarin-3-carboxylate to give a photoluminescent film. The solid-solid reaction is advantageous for the preparation of layered double hydroxides due to the simple and eco-friendly nature (no solvent) of the operation, lower possibility of carbonate contamination and finite particles of the products. - Graphical abstract: Acetate intercalated Mg-Al layered double hydroxide was successfully synthesized by the solid-state reactions using a planetary mil. The acetate intercalated Mg-Al layered double hydroxide prepared was processed into aqueous suspension and film. Display Omitted.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Templating Growth of a Pseudomorphic Lepidocrocite Microshell at the Calcite–Water Interface

The growth of lepidocrocite (gamma-FeOOH) has been observed through oxidation of Fe(II) on calcite (CaCO 3 ). Here, we seek to understand the structural relation between lepidocrocite and the calcite substrate and its growth mechanism. The formation of iron oxyhydroxide layers having distinct morphologies was observed during the dissolution of calcite in acidic Fe(II)-rich solutions. A pseudomorphic lepidocrocite shell together with multiple iron oxyhydroxide layers encapsulated within the shell was imaged by optical and transmission X-ray microscopies. The presence of a several-nanometer-thick ordered lepidocrocite film was observed by X-ray reflectivity, with the lepidocrocite (100) plane oriented parallel to the calcite (104) surface. Lath-shaped lepidocrocite aggregates formed during the initial precipitation, which eventually grew into clusters of parallel platy crystals. The formation of a nanometer-thick well-ordered lepidocrocite film on a pristine calcite surface appears critical for the subsequent pseudomorphic overgrowth. Detachment of the lepidocrocite film from the dissolving calcite surface yielded a free-standing pseudomorphic iron oxyhydroxide shell, suggesting weak interactions between the shell and the calcite substrate. This growth mechanism yields the potential of using carbonate minerals as templates for pseudomorphic synthesis of iron oxyhydroxides having well-defined size and morphology.

25 ENERGY STORAGE↗
DOE OSTI2025

Control over Banded Morphologies and Circular Dichroism in Chiral Halide Perovskites

Chiral halide perovskites (c-HPs) merge the chirality of organic cations with the semiconducting properties of metal halide frameworks, creating a family of chiral semiconductors with tunable chiroptoelectronic behavior. Here, we describe the impact of periodic banded morphologies of textured c-HP ( R/S -NEA) 2 PbBr 4 films (NEA = 1- (1-naphthyl)ethylammonium) on their chiroptical behavior. Due to the interplay between the crystalline and glassy phases, the c-HP film growth is driven by rhythmic precipitation, producing a distinctive controllable radial banded pattern with the ( R/S -NEA) 2 PbBr 4 inorganic planes oriented parallel to the substrate. The banded morphology can be controlled, as evidenced by the growth temperature dictating the ridge-to-ridge spacing as well as the density of banded regions. The resulting circular dichroism (CD) spectral shape, intensity, and polarity vary in a seemingly random manner across processing conditions. However, these spectral features can be explained by considering key features of the banded morphology, such as refraction of the incident light due to surface morphology, birefringence, and stacked, rotated crystallites. These effects cannot be canceled by averaging front and back CD spectra of c-HP films, and our model incorporating these effects reproduces all observed CD spectra remarkably well. The control over the c-HP morphology and prediction capabilities of our CD modeling leads to further understanding of this class of semiconductors and the possibility of exploiting structural features for light polarization control akin to enhanced metamaterials.

14 SOLAR ENERGY↗
DOE OSTI2022

Phase transformation path in Aluminum under ramp compression; simulation and experimental study

Abstract We present a framework based on non-equilibrium molecular dynamics (NEMD) to reproduce the phase transformation event of Aluminum under ramp compression loading. The simulated stress-density response, virtual x-ray diffraction patterns, and structure analysis are compared against the previously observed experimental laser-driven ramp compression in-situ x-ray diffraction data. The NEMD simulations show the solid–solid phase transitions are consistent to experimental observations with a close-packed face-centered cubic (fcc) (111), hexagonal close-packed (hcp) structure (002), and body-centered cubic bcc (110) planes remaining parallel. The atomic-level analysis of NEMD simulations identifiy the exact phase transformation pathway happening via Bain transformation while the previous in situ x-ray diffraction data did not provide sufficient information for deducing the exact phase transformation path.

36 MATERIALS SCIENCE↗
DOE OSTI2018

X-ray diffraction of ramp-compressed aluminum to 475 GPa

Here, we report on a series of experiments that use high-power lasers to ramp-compress aluminum (Al) up to 475 GPa. Under this quasi-isentropic compression, Al remains in the solid state and two solid–solid phase transformations are observed. In situ x-ray diffraction is performed to detect the crystal structure. A velocimetry diagnostic measures particle velocities in order to infer the pressure in the Al sample. We show that a solid–solid phase transition, consistent with a transformation to a hexagonal close-packed (hcp) structure, occurs at 216 ± 9 GPa. At higher pressures, a transformation to a structure consistent with the body-centered cubic (bcc) structure occurs at 321 ± 12 GPa. These phase transitions are also observed in 6061-O (annealed) Al alloy at 175 ± 9 GPa and 333 ± 11 GPa, respectively. Finally, correlations in the high-pressure crystallographic texture suggests the close-packed face-centered cubic (fcc) (111), hcp (002), and bcc (110) planes remain parallel through the solid–solid fcc–hcp and hcp–bcc transformations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Positive spin Hall magnetoresistance in single-crystalline Pt/CoO(001) bilayers

Here, the spin Hall magnetoresistance (SMR) effect in single-crystalline Pt/CoO(001) bilayers has been systematically investigated. X-ray magnetic linear dichroism measurements prove that CoO antiferromagnetic (AFM) spins can be switched into the direction orthogonal to the applied field. We find the SMR signal is comprised of two components related to either the switching of CoO AFM Néel order or the applied strong field effect. Both SMR components show a “positive” angular dependence with $R_{∥} > R_{⊥}$, while $R_{∥} (R_{⊥})$ is defined as the resistance with the applied in-plane field parallel (perpendicular) to the current. The observed positive SMR is mainly attributed to the uncompensated spins at the Pt/CoO interface, instead of the CoO AFM spins. Our study may attract a great deal of interest to understand the complicated SMR effect in AFM spintronics materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Laser angle-resolved photoemission as a probe of initial state k z dispersion, final-state band gaps, and spin texture of Dirac states in the Bi 2 Te 3 topological insulator

Here, we have obtained angle-resolved photoemission (ARPES) spectra from single crystals of the topological insulator material Bi 2 Te 3 using tunable laser spectrometer. The spectra were collected for eleven different photon energies ranging from 5.57 to 6.70 eV for incident light polarized linearly along two different in-plane directions. Parallel first-principles, fully relativistic computations of photo-intensities were carried out using the experimental geometry within the framework of the one-step model of photoemission. Good overall accord between theory and experiment is used to gain insight into how properties of the initial and final state band structures as well as those of the topological surface states and their spin-textures are reflected in the laser-ARPES spectra. In conclusion, our analysis reveals that laser-ARPES is sensitive to both the initial state k z dispersion and the presence of delicate gaps in the final state electronic spectrum.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Two sides of a fault: Grain-scale analysis of pore pressure control on fault slip

Pore fluid pressure in a fault zone can be altered by natural processes (e.g., mineral dehydration and thermal pressurization) and industrial operations involving subsurface fluid injection and extraction for the development of energy and water resources. However, the effect of pore pressure change on the stability and slip motion of a preexisting geologic fault remains poorly understood; yet, it is critical for the assessment of seismic hazard. In this study, we develop a micromechanical model to investigate the effect of pore pressure on fault slip behavior. The model couples fluid flow on the network of pores with mechanical deformation of the skeleton of solid grains. Pore fluid exerts pressure force onto the grains, the motion of which is solved using the discrete element method. We conceptualize the fault zone as a gouge layer sandwiched between two blocks. We study fault stability in the presence of a pressure discontinuity across the gouge layer and compare it with the case of continuous (homogeneous) pore pressure.We focus on the onset of shear failure in the gouge layer and reproduce conditions where the failure plane is parallel to the fault. We show that when the pressure is discontinuous across the fault, the onset of slip occurs on the side with the higher pore pressure, and that this onset is controlled by the maximum pressure on both sides of the fault. In conclusion, the results shed new light on the use of the effective stress principle and the Coulomb failure criterion in evaluating the stability of a complex fault zone.

58 GEOSCIENCES↗
DOE OSTI2017

Measurement of Body-Centered-Cubic Aluminum at 475 GPa [Observation of Body-Centered-Cubic Aluminum at 475 GPa]

Nanosecond in situ x-ray diffraction and simultaneous velocimetry measurements were used to determine the crystal structure and pressure, respectively, of ramp compressed aluminum at stress states between 111 and 475 GPa. The solid-solid Al phase transformations, fcc-hcp and hcp-bcc, are observed at 216 ± 9 GPa and 321 ± 12 GPa, respectively, with the bcc phase persisting to 475 GPa. Here, this is the first in situ observation of the high-pressure bcc phase of Al. High-pressure texture of the hcp and bcc phases suggests close-packed or nearly close-packed lattice planes remain parallel through both transformations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗