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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Failure Morphologies of Cyclically Oxidized ZrO2-Based Thermal Barrier Coatings

Advanced and baseline thermal barrier coatings (TBCs) were thermal cycle tested in air at 1163 C until delamination or spallation of the ceramic top coat. The top coat of the advanced TBC s consisted of ZrO2 with various amounts of Y2O3, Yb2O3, Gd2O3, or Nd2O3 dopants. The composition of the top coat of the baseline TBC was ZrO2-8wt.%Y2O3. All top coats were deposited by air plasma spraying. A NiCrAlY or NiCoCrAlY bond coat was deposited by low pressure plasma spraying onto a single-crystal, Ni-base superalloy. The TBC lifetime for the baseline coatings was approximately 190 cycles (45 minutes at 1163 C per cycle) while the lifetime for the advanced coatings was as high as 425 cycles. The fracture surfaces and sample cross sections were examined after TBC failure by SEM and optical microscopy, and the top coats were further examined by X-ray diffraction. These post-test studies revealed that the fracture path largely followed splat boundaries with some trans-splat fracture. However, there were no obvious distinguishing features which explained the difference in TBC lifetimes between some of the advanced and baseline coatings.

Nesbitt, James A.↗
NASA NTRS1981

Silicide surface phases on gold

The crystalline silicide layers formed on (111) and (100) surfaces of Au films on various Si single-crystal substrates are studied by LEED and AES in conjunction with sputter-depth profiling as a function of annealing temperature. On the (111) surface, three basic silicide structures are obtained corresponding to layers of various thicknesses as obtained by different preparation conditions. The (100) surface shows only two different structures. None of the structures is compatible with the various bulk silicide structures deduced from X-ray diffraction. Using LEED as a criterion for the presence or absence of silicide on the surface, smaller layer thicknesses are obtained than reported previously on the basis of AES studies.

Green, A. K.↗
DOE OSTI2025

Synthesis of Layered Gold Tellurides AuSbTe and Au 2 Te 3 and Their Semiconducting and Metallic Behavior

Previous studies on natural samples of pampaloite (AuSbTe) revealed the crystal structure of a potentially cleavable and/or exfoliable material, while studies on natural and synthetic montbrayite (Sb-containing Au 2 Te 3 ) claimed various chemical compositions for this low-symmetry compound. Few investigations of synthetic samples have been reported for both materials, leaving much of their chemical, thermal, and electronic characteristics unknown. Here, in this study, we investigate the stability, electronic properties, and synthesis of the gold antimony tellurides AuSbTe and Au 1.9 Sb 0.46 Te 2.64 (montbrayite). Differential thermal analysis and in situ powder X-ray diffraction revealed that AuSbTe is incongruently melting, while Au 1.9 Sb 0.46 Te 2.64 is congruently melting. Calculations of the band structures and four-point resistivity measurements showed that AuSbTe is a semiconductor and Au 1.9 Sb 0.46 Te 2.64 a metal. Various synthesis attempts confirmed the limited stable chemical composition of Au 1.9 Sb 0.46 Te 2.64 , identified successful methods to synthesize both compounds, and highlighted the challenges associated with single-crystal synthesis of AuSbTe.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1981

Tribological properties and surface chemistry of silicon carbide at temperatures to 1500 C

Silicon carbide surfaces were heated to 1500 C in a vacuum and analyzed at room temperature with X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The basic unit of the surfaces was considered as a plane of a tetrahedron of either SiC4 and CSi4 composition. AES spectra were obtained from 250-1500 C, with an analysis depth of 1 nm revealed the presence of little Si and mostly graphite. XPS analysis depth was 2 nm or less, and Si was found in the second 1 nm. Sliding friction tests with single-crystal silicon carbide in contact with iron in a vacuum were characterized by a stock-slip value. The coefficient of friction increased with increasing temperature up to 400 C, then decreased with increasing temperature from 400-600 C. Reheating surfaces to 800 C after preheating them to that temperature produced no changes in AES readings. It is concluded that the maximum density of silicon and silicon-carbide is at 800 C, and the higher the sliding temperature, the more metal that is transferred.

Miyoshi, K.↗
NASA NTRS2006

CFD Growth of 3C-SiC on 4H/6H Mesas

This article describes growth and characterization of the highest quality reproducible 3C-SiC heteroepitaxial films ever reported. By properly nucleating 3C-SiC growth on top of perfectly on-axis (0001) 4H-SiC mesa surfaces completely free of atomic scale steps and extended defects, growth of 3C-SiC mesa heterofilms completely free of extended crystal defects can be achieved. In contrast, nucleation and growth of 3C-SiC mesa heterofilms on top of 4H-SiC mesas with atomic-scale steps always results in numerous observable dislocations threading through the 3C-SiC epilayer. High-resolution X-ray diffraction and transmission electron microscopy measurements indicate non-trivial in-plane lattice mismatch between the 3C and 4H layers. This mismatch is somewhat relieved in the step-free mesa case via misfit dislocations confined to the 3C/4H interfacial region without dislocations threading into the overlying 3C-SiC layer. These results indicate that the presence or absence of steps at the 3C/4H heteroepitaxial interface critically impacts the quality, defect structure, and relaxation mechanisms of single-crystal heteroepitaxial 3C-SiC films.

Neudeck, Philip G.↗
NASA NTRS1975

Evaluation of silicon ribbon material for solar cell fabrication

Optical microscopy, electron microscopy, and X-ray diffraction were utilized to characterize silicon ribbon structure. Complex twin formation was observed in nearly all ribbons examined. Twins formed in the 110-plane 112-line ribbon orientation appear stable, and this orientation may be preferable when the ribbon is utilized for solar cells. In addition to twinning, grain boundaries and other structural defects were observed in the ribbon material. Hall effect, resistivity, spreading resistance, surface photovoltage, and solar cell electrical/optical measurements were performed on ribbon samples and correlated with structural and ribbon growth characteristics. Only those ribbon samples with either single-crystal structure or with 'parallel' twin formations were capable of solar-cell performance approaching that of Czochralski material.

Leipold, M.↗
NASA NTRS1976

Interaction of metal layers with polycrystalline Si

Solid-phase reactions of metal films deposited on 0.5-micron-thick polycrystalline layers of Si grown by chemical vapor deposition at 640 C were investigated by MeV He-4 backscattering spectrometry, glancing angle X-ray diffraction, and SEM observations. For the metals Al, Ag, and Au, which form simple eutectics, heat treatment at temperatures below the eutectic results in erosion of the poly-Si layer and growth of Si crystallites in the metal film. Crystallite formation is observed at temperatures exceeding 550 C for Ag, at those exceeding 400 C for Al, and at those exceeding 200 C for Au films. For Pd, Ni, and Cr, heat treatment results in silicide formation. The same initial silicides (Pd2Si, Ni2Si, and CrSi2), are formed at similar temperatures on single-crystal substrates.

Nakamura, K.↗
DOE OSTI2025

Understanding the Electronic Behavior of f-Element Intermetallics

Due to their partially filled f-orbitals, lanthanide and actinide intermetallic materials exhibit intriguing electronic, structural, and magnetic properties. These materials provide a unique platform to explore exotic magnetic and quantum phenomena that arise from their strongly correlated f-electrons, offering insights into f-electron behavior. Incorporating light elements such as boron and carbon can significantly impact the electronic, chemical, and physical properties of these materials, with varying influence between lanthanides and actinides due to the more localized f-electrons in lanthanides. In this work, lanthanide-based intermetallic single crystals containing light atoms were synthesized using the molten metal flux growth method. In this method, one or more low-melting metals such as aluminum, gallium, tin, and bismuth are used in excess as the reaction medium. This solution-state approach allows for lower reaction temperatures compared to solid-state reactions and enables the isolation of kinetic products rather than thermodynamically stable compounds. The synthesized crystals were analyzed using an extensive array of analytical and computational characterization techniques, including single crystal X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, magnetization measurements, and density functional theory calculations. These analyses provided detailed insights into the structural and magnetic properties of the synthesized materials.

37 - INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL C↗
DOE OSTI2026

Understanding Discharge‐Driven Growth of Cathode Impedance in Ni‐Rich NMC Cathodes

Degradation of LiNi x Mn y Co 1-x-y O 2 (NMC)-based lithium-ion batteries depends strongly on cut-off voltage ranges. In addition to the high upper cut-off voltage, a high depth of discharge (i.e., lower cut-off voltage) significantly worsens cathode impedance growth and capacity fade during long-term cycling. However, there is currently no consensus on the mechanism behind the negative role of a deep discharge. Here, this phenomenon was investigated in graphite||NMC cells with single-crystal cathodes (LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NMC622) or LiNi 0.76 Co 0.14 Mn 0.10 O 2 (NMC76)) using targeted aging protocols (constant high-voltage holds vs. charge–discharge cycling), while monitoring transition-metal (TM) dissolution, cathode-electrolyte interface (CEI) impedance, and NMC surface composition. We demonstrate a correlation between discharge-driven CEI impedance growth and increased TM dissolution. Furthermore, this degradation pathway is more pronounced in lower-Ni NMC622 than in higher-Ni (NMC76) under comparable delithiation states at charge, with both compositions undergoing the H2→H3 phase transition. X-ray photoelectron spectroscopy (XPS) reveals NMC composition-dependent evolution of surface lattice oxygen and restructured surface layer composition between charged and discharged states. These findings add mechanistic depth to the role of discharge as an active driver of interfacial degradation and provide new insights into its composition dependence.

25 ENERGY STORAGE↗
DOE OSTI2024

Shock compression of crystalline TeO 2 to the high-pressure fluid regime: Insights from ab initio molecular dynamics simulations

The shock response of fully-dense and porous crystalline tellurium dioxide (TeO 2 ⁠) to the high-pressure and high-temperature fluid regime was investigated within the framework of density functional theory with Mermin’s generalization to finite temperatures. The principal and porous shock Hugoniot curves were predicted from canonical ab initio molecular dynamics (AIMD) simulations, with the phase space sampled along isotherms up to 80 000 K, for densities ranging from ρ = 3 to 17 g/cm 3 . The polymorphs investigated are α-TeO 2 paratellurite (⁠P4 1 2 1 2), TeO 2 cotunnite (⁠Pnma⁠), and TeO 2 post-cotunnite (⁠P2 1 /m⁠). Based on the discontinuity found in the calculated U s – u p slope of TeO 2 post-cotunnite at a shock velocity of U s ≃ 8.35km/s and a particle velocity of u p ≃ 3.64 km/s, the shock melting temperature and pressure are predicted to be ≃ 6500 K and ≃ 170 GPa. Results from the AIMD simulations are in line with the static compression data of TeO 2 paratellurite and cotunnite, and with the recent shock Hugoniot data for single-crystal α- TeO 2 for pressures up to 85 GPa, obtained using the inclined-mirror method and the velocity interferometer system for any reflector combined with powder gun and two-stage light-gas gun.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2026

Quadratic magnetoresistance across the insulator–metal transition in V4O7 thin films

We present a comparative magnetotransport study of V4O7 thin films grown simultaneously on single-crystal Al2O3 (r-cut) and amorphous SiO2 substrates, to examine substrate-induced effects on electronic transport across the insulator–metal transition (IMT). Temperature-dependent resistivity reveals a broad electronic ordering regime below the IMT, with both films exhibiting similar transition temperatures but differing by nearly an order of magnitude in absolute resistivity. Despite this strong substrate dependence of the resistivity scale, the magnetoresistance remains predominantly quadratic in magnetic field over wide temperature intervals for both substrates. Analysis of the quadratic magnetoresistance defines an effective mobility scale that evolves systematically across the IMT and exhibits a similar temperature dependence for the two films. Structural characterization, including atomic-resolution scanning transmission electron microscopy of the V4O7/Al2O3 interface and azimuthal X-ray diffraction measurements, reveals a sharp interface and well-defined in-plane crystallographic registry for the r-cut film, in contrast to the rotationally averaged in-plane structure expected for films grown on amorphous SiO2. These results indicate that while substrate-controlled structural registry modifies the resistivity scale, the quadratic magnetotransport response across the IMT remains largely robust, providing a consistent diagnostic of electronic transport in V4O7 thin films.

25 ENERGY STORAGE↗
DOE OSTI2025

Epitaxial growth of conducting perovskite SrTiO3 on (0001) c-axis sapphire using a γ-Al2O3 intermediate layer

Epitaxial growth of complex oxides on large-area wafers, such as sapphire and silicon, represents a key step toward scalable oxide device production. Solid phase epitaxy allows the synthesis of γ-Al 2 O 3 on α-Al 2 O 3 and provides a template with a matched lattice constant and appropriate cubic symmetry for subsequent heteroepitaxial growth of perovskite complex oxides. Nb-doped SrTiO 3 thin films were deposited epitaxially on (111)-oriented γ-Al 2 O 3 intermediate layers on (0001) c-axis-oriented sapphire α-Al 2 O 3 crystals using pulsed laser deposition. The Nb:SrTiO 3 thin films with a thickness of 53 nm, grown at 700 °C on γ-Al 2 O 3 , reached fully relaxed lattice parameters and were epitaxially oriented with respect to the substrate. Nb:SrTiO 3 layers deposited using identical deposition conditions directly on α-Al 2 O 3 , without the γ-Al 2 O 3 intermediate layer, were polycrystalline. The sheet conductivity of Nb:SrTiO 3 grown on γ-Al 2 O 3 /α-Al 2 O 3 is more than ten times higher than that of Nb:SrTiO 3 grown directly on α-Al 2 O 3 without the γ-Al 2 O 3 layer. The results point to new directions for the integration of (111)-oriented pseudocubic perovskite complex oxides and the integration of epitaxial complex oxides over larger areas using α-Al 2 O 3 single-crystal substrates.

Atomic force microscopy↗
DOE OSTI2025

Thermal expansion of LaB 6 from 298 to 998 K

We propose LaB 6 as a temperature calibration standard for high-temperature (HT) X-ray diffractometry owing to its high temperature stability. Such HT applications require a reliable HT lattice parameter or, equivalently, peak position data, which have not been readily accessible to the diffraction community to date. As such, the thermal expansion behavior of NIST SRM 660a LaB6 was assessed in the temperature range 298–998 K using HT Bragg–Brentano parafocusing θ:θ X-ray diffractometry in conjunction with Rietveld analysis. Data were collected in the 2θ range 20–150° at a data collection rate of 0.5° θ min −1 in air and at 1 atm. The temperature was stepped in 50 K increments. The cubic unit-cell lattice parameter [a(T)] of LaB 6 in Å was found to vary as a(T) = 4.15678 (±0.00001) + Ξ(T − 298 K) + Ψ(T − 298 K) 2 , where Ξ = 2.4645 × 10 −5 (±4.8904 × 10 −8 ) Å K −1 and Ψ = 1.0325 × 10 −8 (±6.7376 × 10 −11 ) Å K −1 . The isobaric volume thermal expansion coefficient (TEC) was obtained as α V P = (5.9291 × 10 −6 ) + (4.9680 × 10 −9 )(T − 298 K) K −1 , from which the corresponding linear TEC was obtained as α L P = (1.9764 × 10 −6 ) + (1.6560 × 10 −9 )(T − 298 K) K −1 . The 3 × 3 matrix representations of the single-crystal isobaric linear TEC and the volume expansivity were obtained for the cubic crystal class to which LaB 6 belongs. Also, the temperature dependence of the lattice parameter data of this study was compared with past landmark studies on LaB 6 by Dutchak et al. [Inorg. Mater. (1972), 8, 1877–1880] and Aivazov et al. [Inorg. Mater. (1979), 15, 1015–1016].

LaB6 standard material↗
DOE OSTI2025

Impact of dynamic Jahn-Teller effect on magnetic excitations, lattice vibration, and thermal conductivity in U 𝑥 ⁢T⁢h 1−𝑥 ⁡O 2 system

Vibrational and magnetic properties of single-crystal uranium-thorium dioxide (U 𝑥 ⁢T⁢h 1−𝑥⁡ O 2 ) with a full range of 0 < 𝑥 < 1 are investigated. Thorium dioxide is a diamagnet whose thermal properties are governed by lattice vibration. The addition of paramagnetic uranium ions leads to the emergence of magnetic effects that alter the thermophysical properties noticeably even at room temperature. The interaction of phonons with magnetic moments of uranium 5⁢𝑓 electrons mediated by magnetoelastic coupling results in an anomalous low-temperature thermal conductivity profile. Analysis of the magnetic susceptibility measurements indicates a departure from the Curie-Weiss relationship characteristic of noninteracting paramagnetic ions, previously associated with the dynamic Jahn-Teller (DJT) effect characterized by coupling between spin and the oxygen sublattice. The T 2⁢g Raman peak position follows a nonlinear trend as a function of uranium concentration and hints that these Raman active optical modes play a role in either DJT or in mediating quadrupole-quadrupole interactions. A first-principle-based thermal transport model is implemented to explain the low-temperature transport measurements, where the anomalous reduction is attributed to phonon-spin resonant scattering. The interplay between spins and phonons is also captured using high-resolution inelastic x-ray scattering (IXS) measurements of phonon linewidths. Our results provide insights into the phonon interactions with the magnetic excitations governing DJT effect and impacting the low-temperature thermal transport processes in this material system. Furthermore, these findings have implications for understanding low-temperature thermal transport and magnetic properties in advanced materials for information processing and energy applications.

36 - MATERIALS SCIENCE↗
DOE OSTI2026

Epitaxial Electrodeposition of Fe with Controlled In-Plane Variants for a Reversible Metal Anode in an Aqueous Electrolyte

The development of reversible metal anodes is a key challenge for advancing aqueous battery technologies, particularly for scalable and safe stationary energy storage applications. Here, in this study, we demonstrate a strategy to realize epitaxial electrodeposition of iron (Fe) on single-crystal copper (Cu) substrates in aqueous electrolytes. We compare the electrodeposition behavior of Fe on polycrystalline and single-crystalline Cu substrates, revealing that the latter enables highly uniform, dense, and crystallographically aligned Fe growth. Comprehensive electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) analysis confirms the formation of Fe with specific out-of-plane and in-plane orientations, including well-defined rotational variants. Our findings highlight that epitaxial electrodeposition of Fe can suppress dendritic growth and significantly enhance Coulombic efficiency during plating/stripping cycles. This approach bridges fundamental crystallography with practical electrochemical performance, providing a pathway toward high-efficiency aqueous batteries utilizing Earth-abundant materials.

aqueous battery↗
DOE OSTI2025

Computing virtual dark-field X-ray microscopy images of complex discrete dislocation structures from large-scale molecular dynamics simulations

Dark-field X-ray microscopy (DFXM) is a novel diffraction-based imaging technique that non-destructively maps the local deformation from crystalline defects in bulk materials. While studies have demonstrated that DFXM can spatially map 3D defect geometries, it is still challenging to interpret DFXM images of the high-dislocation-density systems relevant to macroscopic crystal plasticity. This work develops a scalable forward model to calculate virtual DFXM images for complex discrete dislocation structure(s) (DDS) obtained from atomistic simulations. Our new DDS-DFXM model integrates a non-singular formulation for calculating the local strain from the DDS and an efficient geometrical optics algorithm for computing the DFXM image from the strain field. We apply the model to complex DDS obtained from a large-scale mol­ecular dynamics simulation of compressive loading on single-crystal silicon. Simulated DFXM images exhibit prominent contrast for dislocation features between the multiple slip systems, demonstrating the potential of DFXM to resolve features from dislocation multiplication. In conclusion, the integrated DDS-DFXM model provides a toolbox for DFXM experimental design and image interpretation in the context of bulk crystal plasticity for a range of measurements across shock plasticity and the broader materials science community.

X-ray imaging↗
DOE OSTI2026

Synthesis of Lanthanide-Based Intermetallic Silicides

Lanthanide-containing materials are of interest because of their useful magnetic and electronic behavior. To study this intrinsic behavior, researchers need high-quality single crystals to avoid interference from grain boundaries or defects commonly found in polycrystalline samples. One method for growing single crystals is metal-flux synthesis, an approach that promotes crystal growth at lower reaction temperatures thus providing access to complex intermetallic phases. My project focuses on synthesizing novel lanthanide-containing intermetallic silicides related to previously reported f-element compounds with the Gd1??Fe4Si10?? structure type. I investigated reactions targeting lanthanum, praseodymium, neodymium, samarium, europium, and gadolinium-containing products, and used scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) to identify promising lanthanide-containing phases. I prepared reactions by loading lanthanide oxides, Co, Si, Al, and Ga into alumina crucibles in a 0.2:1:1:10:10 Ln2O3/Co/Si/Al/Ga mmol ratio, where Ln = La, Nd, Pr, Sm, Eu, or Gd. The reactions were sealed in quartz tubes, heated in a furnace, and centrifuged to separate crystals from excess flux. Afterwards, I mechanically isolated single crystals and prepared them for characterization. Pr-, Nd-, and Sm-containing reactions were confirmed through SEM-EDS to have formed the targeted quaternary phase. Single crystal X-ray diffraction (SC-XRD) data showed the Nd-containing crystals exhibited a hexagonal unit cell associated with the Gd1??Fe4Si10?? structure type. La- and Eu-containing reactions instead formed competing Co(Al/Ga/Si)3 phase crystals. Single-crystal XRD, powder XRD, and magnetic susceptibility and heat-capacity measurements will be collected for the remaining lanthanide-containing crystals. This data will help determine the complete crystal structure of the lanthanide analogues, their phase purity and whether they exhibit localized magnetic behavior, magnetic ordering, or other electronic signatures that can be compared with the previously reported actinide analogues. The disordered structure of this intermetallic family is associated with unusual magnetic and electronic behavior meaning lanthanide analogues may show potential as thermoelectric materials. Developing new thermoelectric candidate materials is relevant to energy efficiency and waste-heat recovery, which supports DOE’s broader goal of advancing science and technology solutions for America’s energy needs.

37 - INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL C↗
NASA NTRS1977

Measurements of the frequency spectrum of transition radiation

We report a measurement of the frequency spectrum of X-ray transition radiation. X rays were generated by electrons of 5 and 9 GeV in radiators of multiple polypropylene foils, and detected in the range 4 to 30 keV with a calibrated single-crystal Bragg spectrometer. The experimental results closely reproduce the features of the theoretically predicted spectrum. In particular, the pronounced interference pattern of multifoil radiators and the expected hardening of the radiation with increasing foil thickness are clearly observed. The overall intensity of the radiation is somewhat lower than predicted by calculations.

Cherry, M. L.↗