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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 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

The evolution of orientation relationships during the transformation of a twin-free T-particle to tenfold T-twins in an Al alloy during homogenisation

Highlights: • The ORs of T-phase change continuously during its transformation to tenfold twins. • The changes in ORs are achieved by lattice rotations of T-phase about [010]{sub T} axis. • The OR change of T-phase exhibits a relationship with its cross-section shape. • The OR change of T-phase reduce the interface misfit increased by newly-formed twins. • Rotation of T-particle requires coordinate deformation at the near-interface region. - Abstract: The crystallographic and morphological analysis of T-phase formation in Al alloys was investigated using high-resolution electron microscopy (HRTEM) and selected-area electron diffraction pattern (SAEDP). The results show that the orientation relationships (ORs) of the T-phase change continuously from its original ORs during the transformation of a twin-free T-particle to the tenfold T-twins. These OR changes were achieved by lattice rotations of T-twin domains (T-TDs) about the [010]{sub T}//[010]{sub Al} axis by an angle ranging from 0° to 9°, and this exhibits a relationship with the shape of the cross-sections of the T-phase (T-CSs). The changes in ORs of the T-phase can reduce the increase in interface misfit between the newly-formed T-TDs and the Al matrix. The matrix could only accommodate the rotation of a T-particle at the near-interface region at relatively high temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Grain boundary inter-connections in polycrystalline aluminum with random orientation

Highlights: • The GBICs in a pure aluminum are not random, showing remarkable preference on the planes of low Miller index. • {1 1 1}/{1 1 1} is the most frequent GBIC in pure aluminum. • {1 1 1}/{1 1 1} GBIC is mainly coming from the GBs formed by rotations around , and axes. • {1 1 1}/{1 1 1} GBIC possesses higher PCSD and definite dislocation structures compared to the general GBs. • To pursue {1 1 1}/{1 1 1} GBIC is a pint-cut for the GBE research in high stacking fault energy FCC materials. - Abstract: Grain boundary inter-connection (GBIC) is the matching of two crystallographic planes from two abutting grains ending on the grain boundary (GB) position in polycrystalline materials, which can be expressed as {h_1k_1l_1}/{h_2k_2l_2}. GBIC is the critical parameter that intrinsically defines the character and properties of a GB. In current work, a zone-melted polycrystalline aluminum bar with a purity higher than 99.99% (mass fraction) was subjected to a multi-directional forging (MDF) with a true strain of 4 followed by a recrystallization annealing at 360 °C. Such process repeated at least 4 times until an equiaxed-grain microstructure with random orientation and averaged grain size approximate 30 μm was achieved. Then the GBICs were determined by electron backscatter diffraction (EBSD) measurement and stereology-based five-parameter analysis (FPA) coupled with crystallographic analysis after the grain boundaries (GBs) were filtered according to their misorientations (e.g. angle/axis pair). The results revealed that the GBICs for any group of GBs with a given misorientation are not random, showing remarkable preference on the planes of low Miller index forming mixed and twist GBs. The work also demonstrated that among the high angle boundaries (HABs), {1 1 1}/{1 1 1}, including coherent ∑3 boundaries, is the most frequent GBIC, mainly due to the GBs formed by rotations around <1 1 1>, <1 2 2> and <1 1 2> axes. Near coincidence site (NCS) and O-lattice theory analyses indicate that the {1 1 1}/{1 1 1} GBICs usually possess higher planar coincidence site density (PCSD) and definite dislocation structures compared to the general GBs, implying their more structural stability when only crystallography is taken into account. This result agrees very well with the recent results obtained by molecular dynamic simulations. It is significant to the grain boundary engineering (GBE) in the high stacking fault energy (SFE) face-centered cubic (FCC) materials such as aluminum and its alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Localized orientation gradients in additively manufactured stainless steel 316H structures

The high solidification rates during additive manufacturing cause highly localized thermal and strain gradients. The effect of these gradients on the evolution of local orientation misorientations within a grain is not well understood. In this study, stainless steel 316H parts were fabricated via laser powder bed fusion using three different energy densities: 43, 71, and 135 J/mm 3 . Electron backscatter diffraction showed that the maximum misorientations of the grains can be up to 25° along the build direction. Misorientation gradients (RM g ) within grains are process-dependent and can change from 0.036°/μm to 0.015°/μm with increased volumetric energy densities. In conclusion, the characterized misorientation gradients are an indication of the level of dislocations and, to an extent, the plastic deformation resulting from the rapid solidification during laser powder bed fusion.

316H↗
DOE OSTI2011

Transformation of c-oriented nanowall network to a flat morphology in GaN films on c-plane sapphire

Highlights: {yields} High quality wurtzite structures GaN nanowall network formed on c-plane sapphire. {yields} Tapering of nanowalls at the apex cause electron confinement effects. {yields} Temperature dependent transformation of the six fold nanowall network to a flat morphology. {yields} Growth kinetics is influenced by adatom diffusion, interactions and bonding for GaN layer. -- Abstract: The work significantly optimizes growth parameters for nanostructured and flat GaN film in the 480-830 {sup o}C temperature range. The growth of ordered, high quality GaN nanowall hexagonal honeycomb like network on c-plane sapphire under nitrogen rich (N/Ga ratio of 100) conditions at temperatures below 700 {sup o}C is demonstrated. The walls are c-oriented wurtzite structures 200 nm wide at base and taper to 10 nm at apex, manifesting electron confinement effects to tune optoelectronic properties. For substrate temperatures above 700 {sup o}C the nanowalls thicken to a flat morphology with a dislocation density of 10{sup 10}/cm{sup 2}. The role of misfit dislocations in the GaN overlayer evolution is discussed in terms of growth kinetics being influenced by adatom diffusion, interactions and bonding at different temperatures. The GaN films are characterized by reflection high energy electron diffraction (RHEED), field emission scanning electron (FESEM), high resolution X-ray diffraction (HRXRD) and cathodoluminescence (CL).

36 MATERIALS SCIENCE↗
DOE OSTI2012

Oriented growth of urchin-like zinc oxide micro/nano-scale structures in aqueous solution

Highlights: Black-Right-Pointing-Pointer Highly oriented and well-defined ZnO urchin-like crystals were successfully fabricated by a facile and effective hydrotherm method. Black-Right-Pointing-Pointer Polyvinylpyrrolidone- and hydrogen peroxide-assisted synthesis of ZnO could optimize its crystalline quality and the obtained ZnO have smooth surface, radial growth of morphology, obvious crystal edges and decreased defects. Black-Right-Pointing-Pointer The physicochemical properties of samples were studied by analysis of its structure, morphology, surface and optical properties. Black-Right-Pointing-Pointer This study represented a multistep mechanism based on [Zn(OH){sub 4}]{sup 2-} growth units about formation such urchin-like structure. -- Abstract: The urchin-like ZnO microcrystals with high crystallinity decomposed from [Zn(OH){sub 4}]{sup 2-} directly were obtained via a hydrothermal method. The morphology, particle size, crystalline structure and fluorescence of the as-prepared ZnO were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) analyses. The results demonstrated that the urchin-like ZnO crystals with wurtzite structure had a narrow distribution in size, which could be adjusted in the range of 30-80 {mu}m by varying reaction time. Broad visible light emission peak was also observed in the PL spectra of the synthesized ZnO products. A multistep growth process about how to form such a structure was proposed.

36 MATERIALS SCIENCE↗
DOE OSTI2012

The epitaxial growth of (1 1 1) oriented monocrystalline Si film based on a 4:5 Si-to-SiC atomic lattice matching interface

Highlights: ► A monocrystalline Si film was demonstrated by XRD to epitaxially grow on the 6H-SiC substrate. ► A 4:5 Si-to-SiC lattice matching structure was observed at the Si/SiC interface. ► The calculated value of the actual lattice mismatch is only 0.26%. ► Defects can be effectively reduced at the 4:5 Si-to-SiC lattice matching Si/SiC interface. -- Abstract: Due to a huge lattice mismatch of about 20% theoretically existing between SiC and Si, it is difficult for growing monocrystalline Si/SiC heterojunction to realize the light control of SiC devices. However, based on a 4:5 Si-to-SiC atomic lattice matching interface structure, the monocrystalline Si films were epitaxially prepared on the 6H-SiC (0 0 0 1) substrate by hot-wall chemical vapor deposition in our work. The film was characterized by X-ray diffraction analysis with only (1 1 1) orientation occurring. The X-ray rocking curves illustrated good symmetry with a full width at half maximum of 0.4339° omega. A 4:5 Si-to-SiC atomic matching structure of the Si/6H-SiC interface clearly observed by the transmission electron microscope revealed the essence of growing the monocrystalline Si film on the SiC substrate.

36 MATERIALS SCIENCE↗
DOE OSTI2012

The effect of complexing agents on the oriented growth of electrodeposited microcrystalline cuprous oxide film

Highlight: ► Cu{sub 2}O microcrystalline film is electrodeposited on ITO with complexing agents. ► As the stability constant increasing, the overpotential is negatively shifted. ► The formation energy of different planes is affected by overpotential. ► The overpotential can significantly alter the growth priority of different planes. ► The morphology of Cu{sub 2}O film is significantly modified by complexing agents. -- Abstract: Three conventional complexing agents, including lactic acid, citric acid and EDTA, are applied in the electrodeposition of microcrystalline cuprous oxide (Cu{sub 2}O) film on indium tin oxide glass substrate. Both scanning electron microscopy and X-ray diffraction have been performed to characterize the morphology and texture of microcrystalline Cu{sub 2}O film. It is found that the stability constant of copper-based complex compound can obviously influence the deposition overpotential of Cu{sub 2}O, and the overpotential can significantly alter the growth priority of different planes, which results in oriented growth of Cu{sub 2}O grains. The quantitative relationships between the stability constant and the deposition overpotential of different complexing agents, as well as the relationship between the overpotential and the formation energy of microcrystalline cuprous oxide's (1 1 0), (1 1 1) and (2 0 0) planes are calculated, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2013

[Bmim][TfO] ionic liquid-assisted oriented growth of Co{sub 3}O{sub 4} nanoworms

Graphical abstract: Display Omitted Highlights: ► First time, we have used [Bmim][TfO]IL for the synthesis of Co{sub 3}O{sub 4} nanoworms. ► IL assists to form oriented growth of cubic Co{sub 3}O{sub 4} nanoworms without intermediate. ► Cubic Co{sub 3}O{sub 4} nanoworms are in the range of 20 nm width and 100–200 nm length. ► IL and oxidizing agent have not altered the Co{sub 3}O{sub 4} structural characteristics. ► Co{sub 3}O{sub 4} nanoworms exhibit crystalline domain dependent weak ferromagnetism. -- Abstract: Monodispersed worm-like structure of Co{sub 3}O{sub 4} nanocrystals of 20 nm width and 100–200 nm length are prepared directly without any intermediate product by 1-n-butyl-3-methylimidazolium trifluoromethane sulfonate ionic liquid ([Bmim][TfO] IL) assisted precipitation method. The higher concentration of [Bmim][TfO] IL in the reaction medium leads to the formation of homogeneous nanoworms. The effect of synthesis temperature and the oxidizing agent (H{sub 2}O{sub 2}) on the Co{sub 3}O{sub 4} particle's morphology and their magnetic properties are discussed. Thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) analysis were used to characterize the Co{sub 3}O{sub 4} monodispersed nanoworms. The magnetic property of the spinel Co{sub 3}O{sub 4} nanoworms is highly dependent on crystalline domains and exhibits weak ferromagnetic behavior with a narrow hysteresis loop opening.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Surface modifications and optical variations of (−1 1 1) lattice oriented CuO nanofilms for solar energy applications

Graphical abstract: - Highlights: • The films are grown using a low cost SILAR method. • The pH value is found to play a significant role in the property of the resulting films. • The fabrication of band pass filters between 450 nm and 1000 nm is envisaged. • Electrical conductivity and optical band gap values were found to be 68.1 × 10{sup −3} Ω{sup −1} cm{sup −1} and 1.08 eV. • Coating may aid the small band of frequencies could pave way for enhancing the efficiency. - Abstract: This paper reports on the preparation and characterization of Successive Ionic Layer by Adsorption and Reaction (SILAR) grown CuO thin films. The films were deposited onto glass substrates at various solution pH values. The thickness of the film is increased with increase of solution pH values. X-ray diffraction analysis revealed that the prepared films exhibited the monoclinic structure with (−1 1 1) predominant orientation. The optimized pH value is 11 ± 0.1. The microstructure, morphology, optical and electrical properties are studied and reported. The transmission spectra (T) at normal incidence revealed that the films exhibit indirect transitions and may be tailored for passing selected bands of frequencies in visible near IR range. The activation energy is estimated to be about 0.29 eV.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Orientations of Al4C3 and Al films grown on GaAs substrates

We present that a method for growth of aluminum epilayers on III-V substrates using metalorganic chemic vapor deposition (MOCVD) processes could be beneficial for optoelectronic and photovoltaic device fabrication. However, de- position from common precursors under standard MOCVD conditions results in polycrystalline Al 4 C 3 . Both Al 4 C 3 films grown on GaAs (100) substrates, and those grown on GaAs (111) B substrates, show strong alignment of the rhombohedral [110] for the Al 4 C 3 crystallites with the in-plane GaAs<110>directions. However, by using plasma-enhanced MOCVD at low growth temperatures, elemental Al can be deposited. Al growth by this method on (001), (111) B and (110) GaAs substrates gave textured, polycrystalline films. In all cases, the Al crystallites are primarily oriented with a<110>aligned with an in-plane<110>of the substrate at initial growth stages. Lastly, these insights may lead towards growth of large-grained or epitaxial Al films.

14 SOLAR ENERGY↗
DOE OSTI2023

Influence of energy density on the microstructure, growth orientation, and anisotropy of magnetic properties in additively manufactured Fe-3.8wt%Si transformer steels

Fe-3.8wt%Si transformer steels were processed using two different additive manufacturing (AM) techniques, laser powder bed fusion (LPBF) and directed energy deposition (DED). While the LPBF processed samples exhibited a strong <001> orientation of the BCC grains along the build axis, the DED processed samples exhibited a randomized texture along the build axis. DED processed samples showed substantially coarser columnar grains as compared to their LPBF counterparts. Here, the columnar grains exhibited a substantial number of low-angle sub-grain boundaries. All samples exhibited very good soft magnetic properties, with saturation magnetization (M s ) values ranging from 205 - 232 emu/gm, and coercivity (H c ) values ranging from 1.2 – 4.2 Oe. The Coercivity (H c ) values were significantly lower when the magnetic field was applied parallel to the build axis, as compared to being perpendicular, which can be rationalized based on the columnar nature of the grains, resulting in a higher number density of grain boundaries in case of the field applied perpendicular to the build axis.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Impact of layer thickness and well orientation on caprock integrity for geologic carbon storage

Economic feasibility of geologic carbon storage demands sustaining large storage rates without damaging caprock seals. Reactivation of pre-existing or newly formed fractures may provide a leakage pathway across caprock layers. In this paper, we apply an equivalent continuum approach within a finite element framework to model the fluid-pressure-induced reactivation of pre-existing fractures within the caprock, during high-rate injection of super-critical CO 2 into a brine-saturated reservoir in a hypothetical system, using realistic geomechanical and fluid properties. We investigate the impact of reservoir to caprock layer thickness, wellbore orientation, and injection rate on overall performance of the system with respect to caprock failure and leakage. We find that vertical wells result in locally higher reservoir pressures relative to horizontal injection wells for the same injection rate, with high pressure inducing caprock leakage along reactivated opening-mode fractures in the caprock. After prolonged injection, leakage along reactivated fractures in the caprock is always higher for vertical than horizontal injection wells. Furthermore, we find that low ratios of reservoir to caprock thickness favor high excess pressure and thus fracture reactivation in the caprock. Finally, injection into thick reservoir units thus lowers the risk associated with CO 2 leakage.

58 GEOSCIENCES↗
DOE OSTI2020

Orientation and morphology of Pt nanoparticles in γ-alumina processed via ion implantation and thermal annealing

Structure and chemistry of metal/metal-oxide interfaces are critical for many catalytic processes and sensing. Pristine interfaces of Pt and γ-Al 2 O 3 were fabricated using high-energy ion implantation and thermal processing. Amorphous regions of alumina develop in single crystal α-alumina during Pt+ implantation and an 800 °C thermal treatment crystalizes amorphized alumina to γ-Al 2 O 3 and allows Pt ions to precipitate within the developing γ-alumina, yielding Pt nanoparticle tetrahedra terminated by {111} surfaces. The phase of alumina that developed and the distribution, morphology, and orientation of Pt nanoparticles was determined using x-ray diffraction, Rutherford backscattering spectrometry, transmission electron microscopy and scanning transmission electron microscopy.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Increased fracture depth range in controlled spalling of (100)-oriented germanium via electroplating

Controlled spalling in (100)-oriented germanium using a nickel stressor layer shows promise for semiconductor device exfoliation and kerfless wafering. Demonstrated spall depths of 7-60 um using DC sputtering to deposit the stressor layer are appropriate for the latter application but spall depths < 5 um may be required to minimize waste for device applications. This work investigates the effect of tuning both electroplating current density and electrolyte chemistry on the residual stress in the nickel and on the achievable spall depth range for the Ni/Ge system as a lower-cost, higher-throughput alternative to sputtering. By tuning current density and electrolyte phosphorous concentration, it is shown that electroplating can successfully span the same range of spalled thicknesses as has previously been demonstrated by sputtering and can reach sufficiently high stresses to enter a regime of thickness (<7 um) appropriate to minimize substrate consumption for device applications.

14 SOLAR ENERGY↗
DOE OSTI2011

Beyond the crystallization paradigm: Structure determination from diffraction patterns from ensembles of randomly oriented particles

We amplify on the priciples of the method we have recently proposed for recovering an oversampled diffraction pattern of a single particle from measured diffraction patterns from multiple particles in orientations related by rotation about an axis parallel to the incident radiation. We propose an alternative method of phasing a reference resolution ring by means of a non-negativity constraint on the diffraction intensities, point out the need for caution about enantiomeric ambiguities in the reconstruction of a diffraction pattern from its angular correlations, and show that converged correlations may be deduced by appropriate averaging of even very noisy data.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Determination of solute site occupancies within γ' precipitates in nickel-base superalloys via orientation-specific atom probe tomography

In this study, the analytical limitations in atom probe tomography such as resolving a desired set of atomic planes, for solving complex materials science problems, have been overcome by employing a well-developed unique and reproducible crystallographic technique, involving synergetic coupling of orientation microscopy with atom probe tomography. The crystallographic information in atom probe reconstructions has been utilized to determine the solute site occupancies in Ni-Al-Cr based superalloys accurately. The structural information in atom probe reveals that both Al and Cr occupy the same sub-lattice within the L1 2 -ordered g precipitates to form Ni 3 (Al,Cr) precipitates in a Ni-14Al-7Cr(at.%) alloy. Interestingly, the addition of Co, which is a solid solution strengthener, to a Ni-14Al-7Cr alloy results in the partial reversal of Al site occupancy within g precipitates to form (Ni,Al) 3 (Al,Cr,Co) precipitates. This unique evidence of reversal of Al site occupancy, resulting from the introduction of other solutes within the ordered structures, gives insights into the relative energetics of different sub-lattice sites when occupied by different solutes.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Recycling-oriented characterization of plastic frames and printed circuit boards from mobile phones by electronic and chemical imaging

Highlights: • A recycling oriented characterization of end-of-life mobile phones was carried out. • Characterization was developed in a zero-waste-perspective, aiming to recover all the mobile phone materials. • Plastic frames and printed circuit boards were analyzed by electronic and chemical imaging. • Suitable milling/classification strategies were set up to define specialized-pre-concentrated-streams. • The proposed approach can improve the recovery of polymers, base/precious metals, rare earths and critical raw materials. - Abstract: This study characterizes the composition of plastic frames and printed circuit boards from end-of-life mobile phones. This knowledge may help define an optimal processing strategy for using these items as potential raw materials. Correct handling of such a waste is essential for its further “sustainable” recovery, especially to maximize the extraction of base, rare and precious metals, minimizing the environmental impact of the entire process chain. A combination of electronic and chemical imaging techniques was thus examined, applied and critically evaluated in order to optimize the processing, through the identification and the topological assessment of the materials of interest and their quantitative distribution. To reach this goal, end-of-life mobile phone derived wastes have been systematically characterized adopting both “traditional” (e.g. scanning electronic microscopy combined with microanalysis and Raman spectroscopy) and innovative (e.g. hyperspectral imaging in short wave infrared field) techniques, with reference to frames and printed circuit boards. Results showed as the combination of both the approaches (i.e. traditional and classical) could dramatically improve recycling strategies set up, as well as final products recovery.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Flow over an espresso cup: inferring 3-D velocity and pressure fields from tomographic background oriented Schlieren via physics-informed neural networks

Tomographic background oriented Schlieren (Tomo-BOS) imaging measures density or temperature fields in three dimensions using multiple camera BOS projections, and is particularly useful for instantaneous flow visualizations of complex fluid dynamics problems. We propose a new method based on physics-informed neural networks (PINNs) to infer the full continuous three-dimensional (3-D) velocity and pressure fields from snapshots of 3-D temperature fields obtained by Tomo-BOS imaging. The PINNs seamlessly integrate the underlying physics of the observed fluid flow and the visualization data, hence enabling the inference of latent quantities using limited experimental data. In this hidden fluid mechanics paradigm, we train the neural network by minimizing a loss function composed of a data mismatch term and residual terms associated with the coupled Navier–Stokes and heat transfer equations. We first quantify the accuracy of the proposed method based on a two-dimensional synthetic data set for buoyancy-driven flow, and subsequently apply it to the Tomo-BOS data set, where we are able to infer the instantaneous velocity and pressure fields of the flow over an espresso cup based only on the temperature field provided by the Tomo-BOS imaging. Moreover, we conduct an independent PIV experiment to validate the PINN inference for the unsteady velocity field at a centre plane. To explain the observed flow physics, we also perform systematic PINN simulations at different Reynolds and Richardson numbers and quantify the variations in velocity and pressure fields. Furthermore, the results in this paper indicate that the proposed deep learning technique can become a promising direction in experimental fluid mechanics.

97 MATHEMATICS AND COMPUTING↗