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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 1,639 records · Page 91
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Phase separation during the direct powder bed fusion of SiC

Powder bed fusion (PBF) is an attractive additive manufacturing option for fabrication of SiC object with complex geometries. However, the density and microstructure controls remain a challenge. This study is aimed at understanding laser–SiC interactions, with emphasis on microstructure-processing relationships, to identify potential solutions for the process improvement. SiC tubes were fabricated by PBF of pure SiC powders without sintering additives. Further, comprehensive analysis by X-ray diffraction, Raman spectroscopy, and electron microscopy indicated that binding of SiC particles was achieved by incongruent melting of SiC to a Si/C mixture containing SiC micro- and nanocrystallites. The phase evolution under laser irradiation of SiC was explained by phase diagrams. This study uncovered the PBF SiC microstructure at different length scales and the relationship between the microstructure and the processing parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Advances in secondary ion mass spectrometry for N-doped niobium

Accurate secondary ion mass spectroscopy measurement of nitrogen in niobium relies on the use of closely equivalent standards, made by ion implantation, to convert nitrogen signal intensity to nitrogen content by determination of relative sensitivity factors (RSFs). Accurate RSF values for ppm-range nitrogen contents are increasingly critical, as more precision is sought in processes for next-generation superconducting radiofrequency (SRF) accelerator cavities. Furthermore, factors influencing RSF value measurements were investigated with the aim of reliably attaining better than 10% accuracy in nitrogen concentrations at various depths into the bulk. This has been accomplished for materials typical of SRF cavities at the cost of increased attention to all aspects.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Phase evolution and morphology in Cu-In-Ga sputtered precursors

The reaction of metallic precursors has become the primary method of industrial manufacturing for Cu(In,Ga)Se2. Commonly used Cu3Ga sputter targets have thus far dictated that the relative Ga composition of these precursors is Ga/(In+Ga) ≈ 0.25. Cu-In-Ga precursors are prepared with varying DC sputtering conditions and Ga compositions ranging from 0 ≤ Ga/(In+Ga) ≤ 0.75. The phase evolution and morphology of these precursors is characterized using x-ray diffraction (XRD) and scanning electron microscopy, including in situ annealing of precursors during XRD measurements. It is observed that the Ga composition of as-deposited precursors affects phase evolution with annealing. Consistent morphology changes were not observed with changing Ga, however, film morphology was controlled by adjusting In sputter conditions.

Lam, Isaac K. (ORCID:0000000198002765)↗
DOE OSTI2021

Nonlinear ultrasonic technique for the characterization of microstructure in additive materials

This study employs nonlinear ultrasonic techniques to track microstructural changes in additively manufactured metals. The second harmonic generation technique based on the transmission of Rayleigh surface waves is used to measure the acoustic nonlinearity parameter, β. Stainless steel specimens are made through three procedures: traditional wrought manufacturing, laser-powder bed fusion, and laser engineered net shaping. The β parameter is measured through successive steps of an annealing heat treatment intended to decrease dislocation density. Dislocation density is known to be sensitive to manufacturing variables. In agreement with fundamental material models for the dislocation-acoustic nonlinearity relationship in the second harmonic generation, β drops in each specimen throughout the heat treatment before recrystallization. Geometrically necessary dislocations (GNDs) are measured from electron back-scatter diffraction as a quantitative indicator of dislocations; average GND density and β are found to have a statistical correlation coefficient of 0.852 showing the sensitivity of β to dislocations in additively manufactured metals. Moreover, β shows an excellent correlation with hardness, which is a measure of the macroscopic effect of dislocations.

42 ENGINEERING↗
DOE OSTI2025

An experimental and computational investigation of the structure and spectroscopic signatures of α -UO 3

α-UO 3 is a common intermediate compound found in the nuclear fuel cycle, yet the exact crystal structure of this material has long been debated. Inconsistent computational and experimental data in previous works has led to varying conclusions between authors. Furthermore, to ensure the validity of our results in this work, the structural and spectroscopic signatures of pure phase α-UO 3 are investigated using powder X-ray diffraction and optical vibrational spectroscopy (infrared and Raman). Rietveld refinement of powder X-ray diffraction data on pure phase α-UO 3 collected in this work allows us to propose an alteration to the currently accepted C2mm structure (a = 3.9705 Å, b = 6.8553 Å, c = 4.15955 Å, α = β = γ = 90°) for α-UO 3 with no uranyl [UO 2 2+ ] bonds. Raman spectra collected using two excitation wavelengths (two instruments using 532 nm and one 785 nm) are presented, and differences with recently published results are discussed. Infrared spectra from two instruments used here agree well with recently published results, but the spectral range encompassed in our data extends past what has been reported with modern techniques. Additionally, we provide tentative vibrational mode assignments based on density functional perturbation theory calculations and resulting phonon eigenvector visualizations. Unexpected features in the optical vibrational spectra of α-UO 3 are explained by unique features in the structure we present.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2023

CalTestBed - OnTo Technology - Characterization of Recycled Cathode and Anode Particles as a Function of Process Step (Final Report)

Onto Technology carries out advanced Li-ion battery recycling for industry and. has the only patented technology to produce manufacturing quality electrode materials from recycled batteries. The technology can resolve ongoing cost problems for the industry in life-cycle and conservation of critical materials. Under the Cal TestBed program, Onto Technology teamed with principal investigators at Lawrence Berkeley National Laboratory, who performed tests to evaluate the electrochemical performance of refurbished electrode materials. Other tests to determine structure and morphology of the refurbished materials carried out at LBNL included X-ray diffraction (XRD) and scanning electron microscopy (SEM).

36 MATERIALS SCIENCE↗
DOE OSTI2023

Analysis of Coronado State Historic Site artifacts using X-rays

Two historic-period metal artifacts were provided by the New Mexico Historic Sites to Los Alamos National Laboratory for non-destructive analysis. The artifacts were a crossbow quarrel (or bolthead) and a reliquary pendant recovered from Kuaua Pueblo (also known as the Coronado Historic Site) in Bernalillo, NM. The quarrel is a heavily patinated metal that had been flattened due to compressive forces. The pendant consisted of a metal casing that had previously surrounded two center gemstones on the front and rear face of the pendant. The gemstone in the rear setting had fractured and was displaced from the setting, leaving only a small, loose fragment within the pendant for study. The front gem appeared to be very dark, near-black in color, and the fragment of the rear gem was a bright red color. The artifacts were analyzed to ascertain their composition and glean insight into their provenance using the following X-ray techniques: X-ray computed tomography, confocal micro X-ray fluorescence, and X-ray diffraction. Infrared spectroscopy and electron microscopy were used on selected areas. Ultraviolet Raman spectra were collected on the two gems and the pendant. The metal material of the artifacts was found to be primarily composed of copper. The gems in the pendant were composed of manganese (front gem) and calcium (side gem).

36 MATERIALS SCIENCE↗
DOE OSTI2026

Boride-based Ceramic Super-high Temperature Thermocouples in Harsh Environments (Final Scientific/Technical Report)

An electromotive force (emf) can be generated along a temperature gradient between the cold end and hot end of a thermoelectric material, termed the Seebeck effect. Based on the Seebeck effect, metallic alloys have been extensively employed to detect temperatures for centuries, named thermocouples. However, commercially available thermocouple alloys suffer from limitations, such as oxidation, chemical degradation, and poor long-term stability under high-temperature harsh environments. This DOE-funded project aimed to develop high-temperature, chemically tolerant thermocouples suitable for operation in extreme environments relevant to semiconducting thermoelectric materials. The research focused on boride-based semiconducting thermoelectric compounds as candidates for next-generation thermocouples with enhanced oxidation resistance, chemical stability, and thermal robustness under conditions representative of charcoal-fired electricity facilities. During the funded years, boride materials were synthesized using an arc-plasma technique under ambient air and argon atmospheres, enabling scalable and cost-effective production compared with conventional boride fabrication methods. The synthesized borides were processed into nanostructured powders, followed by consolidation into dense bulk materials using a spark plasma sintering (SPS) bottom-up approach. Comprehensive characterization was performed, including microstructural analysis, electrical transport measurements, and optical and thermal property evaluation. Both p-type and n-type boride electric legs were fabricated and integrated into boride-based thermocouples. The thermal and irradiation stabilities of the boride nanomaterials and bulk thermoelectric materials were systematically evaluated to assess suitability for long-term operation in harsh environments. Additionally, 12 students were broadly hands-on trained spanning the full research workflow, including word processing and technical editing (e.g., LATEX for manuscript and poster preparation), data collection and analysis (using Python and related libraries and hardware interfaces), sample preparation (including arc-plasma synthesis and spark plasma sintering), and advanced characterization techniques (such as X-ray diffraction, UV–vis spectroscopy, electron microscopy, differential thermal analysis (DTA), and Seebeck coefficient measurements, etc). Overall, this project demonstrated the feasibility of boride-based thermoelectric materials as durable high-temperature thermocouples, providing a promising pathway toward robust temperature sensing technologies aligned with DOE energy infrastructure and extreme-environment monitoring needs.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2020

Transient Microstructure Evolutions and Local Properties of Dual-Phase 980 MPa Grade Steel Via Friction Stir Spot Processing

Friction stir processing is a novel solid-state process to modify microstructures and their properties by intense, localized plastic deformation. However, little research has been reported for microstructure evolutions of advanced high-strength steels during the process. The present work focuses on the study of transient microstructure changes and local mechanical properties for friction stir spot processed dual-phase (DP) 980 MPa grade steel (DP980) under different peak temperatures. A pinless silicon nitride ceramic tool was used to produce relatively simple material deformation and flow near the tool. Friction stir spot processed steel samples were characterized by optical and electron microscopies. Furthermore, Vickers microhardness and nano-indentation measurements were used to study local mechanical properties for correlation with microstructures. A swallow layer of refined grains (<0.6 µm) was obtained with a low peak temperature (under 400 °C), whereas higher peak temperatures (>Ac 1 ) led to a change in grain size with different microstructures (fine-grained DP or martensite). Electron back-scattered diffraction characterizations revealed a large deformation in the as-received microstructures (mixture of ferrite and tempered martensite) induced by friction stir spot processing, leading to recrystallization and grain refinement around the stirred zone. Also, nano-indentation measurements showed a higher hardness than the hardness of the as-received DP980. Friction stir processing with different process conditions effectively changed microstructures and local mechanical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Understanding of Active Sites and Interconversion of Pd and PdO during CH 4 Oxidation

Pd-based catalysts are widely used in the oxidation of CH 4 and have a significant impact on global warming. However, understanding their active sites remains controversial, because interconversion between Pd and PdO occurs consecutively during the reaction. Understanding the intrinsic active sites under reaction conditions is critical for developing highly active and selective catalysts. In this study, we demonstrated that partially oxidized palladium (PdO x ) on the surface plays an important role for CH 4 oxidation. Regardless of whether the initial state of Pd corresponds to oxides or metallic clusters, the topmost surface is PdO x , which is formed during CH4 oxidation. A quantitative analysis using CO titration, diffuse reflectance infrared Fourier-transform spectroscopy, X-ray diffraction, and scanning transmission electron microscopy demonstrated that a surface PdO layer was formed on top of the metallic Pd clusters during the CH 4 oxidation reaction. Furthermore, the time-on-stream test of CH 4 oxidation revealed that the presence of the PdO layer on top of the metallic Pd clusters improves the catalytic activity. Our periodic density functional theory (DFT) calculations with a PdO x slab and nanoparticle models aided the elucidation of the structure of the experimental PdO particles, as well as the experimental C-O bands. The DFT results also revealed the formation of a PdO layer on the metallic Pd clusters. This study helps achieve a fundamental understanding of the active sites of Pd and PdO for CH 4 oxidation and provides insights into the development of active and durable Pd-based catalysts through molecular-level design.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Synthesis of epitaxial TaO$_2$ thin films on Al$_2$O$_3$ by suboxide molecular-beam epitaxy and thermal laser epitaxy

Tantalum dioxide (TaO2) is a metastable tantalum compound. Here, we report the epitaxial stabilization of TaO2 on Al2O3 (1-102) (r-plane sapphire) substrates using suboxide molecular-beam epitaxy (MBE) and thermal laser epitaxy (TLE), demonstrating single-oriented, monodomain growth of anisotropically strained thin films. Microstructural investigation is performed using synchrotron X-ray diffraction and scanning transmission electron microscopy. The tetravalent oxidation state of tantalum is confirmed using X-ray absorption and photoemission spectroscopy as well as electron energy-loss spectroscopy. Optical properties are investigated via spectroscopic ellipsometry and reveal a 0.3 eV Mott gap of the tantalum 5d electrons. Density-functional theory and group theoretical arguments are used to evaluate the limited stability of the rutile phase and reveal the potential to unlock a hidden metal-insulator transition concomitant with a structural phase transition to a distorted rutile phase, akin to NbO2. Our work expands the understanding of tantalum oxides and paves the way for their integration into next-generation electronic and photonic devices.

FOS: Physical sciences↗
DOE OSTI2022

Exposure of Stainless Steel 316 to Subcritical, Transition, and Near-Supercritical Water

This work investigates the oxidation of austenitic stainless steel 316 at temperatures close to the critical point of water: subcritical water at 330°C and 27 MPa, the transition between subcritical and supercritical water at 374°C and 27 MPa, and supercritical water (SCW) at 380°C and 27 MPa. The surfaces of the samples were characterized using x-ray diffraction, Raman spectroscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy before and after exposure. Magnetite (Fe3O4) was found to be present on all surfaces of all samples. The samples exposed to subcritical water also showed the presence of a nickel-iron chromium mixed spinel Ni(Fe2-xCrx)O4. The oxide morphology was observed to vary based on exposure temperature; an increased nucleation and growth rate, and an increased generation of Fe2+ was observed on samples exposed to the transition region and SCW.

Materials Science↗
DOE OSTI2024

Effects of Al Substitution for Fe in Na₅FeSi₄O₁₂ (5.1.8) Glasses: Structure and Crystallization

In this study, the effects of substituting Al for Fe in 5Na2O∙(Al2O3)x∙(Fe2O3)1-x∙8SiO2 glass, x=0 to 1, and Na5AlxFe1-xSi4O12 (5.1.8) crystal, were investigated using thermal analysis, Fe K-edge X-ray absorption, X-ray diffraction, Raman spectroscopy, and Electron Probe Microanalysis. In both glass and crystallized glass, nearly all the Fe was tetrahedrally coordinated Fe3+, as expected from the high concentration of Na2O. The substitution of Al for Fe in the glasses caused the glass transition temperature to increase as polymerization increased, as evidenced by Raman, likely due to both field strength differences of Al vs Fe and a small amount of Fe2+ network modifier present with Fe. After heat treatment at 700 °C for 24 hours, the glasses had crystallized, forming Na2SiO3 and NaAlSiO4 in compositions with high Al concentrations and the 5.1.8 crystal in compositions with high Fe concentrations. Through electron microprobe, it was determined that <0.04 formula unit Al incorporated into the 5.1.8 crystal, i.e. Na5Fe0.96Al0.04Si4O12. The 5.1.8 crystal only formed when Fe concentration was higher than Al in the starting glass.

Antonio, Raine (ORCID:0009000634297975)↗
NASA NTRS1975

Relative cooling rates of mare basalts at the Apollo 12 and 15 sites as estimated from pyroxene exsolution data

X-ray single-crystal diffraction studies, supplemented by electron microprobe analyses of core pigeonites and rim augites from rocks 12031, 15085, 15475, and 15495, have been used to suggest cooling rates for these and other Apollo 12 and 15 rocks studied by similar methods. The extent of subsolidus phase separation of pyroxenes is used as a measure of the cooling rate. The results were interpreted in terms of model cooling histories of a lava flow whose thickness was estimated from the absolute cooling rates obtained by cooling rate experiments and by temperature-time variation through an extrusive flow computed by employing simplified theory of Jaeger. All available data on the exsolution and cation distributions of pyroxenes from Apollo 12 and 15 samples at present are consistent with the hypothesis that these rocks were derived from the top and interior of lava flows with thicknesses of 4-10 m. A process for exsolution of augite from a host pigeonite on (100) has been related to its low-calcium content.

Takeda, H.↗
NASA NTRS1985

Corrosion behavior of surface films on boron-implanted high purity iron and stainless steels

Boron (dose, 2 x 10 to the 17th ions/sq cm) was implanted into high purity iron, AISI 316 austenitic stainless steel, and AISI 440C martensitic stainless steel, at 40 keV. The film structure of implanted samples was examined and characterized by contrast and diffraction analyses utilizing transmission electron microscopy. The effect of B(+) ion implantation on the corrosion behavior was studied using the potentiodynamic polarization technique. Tests were performed in deaerated 1 N H2SO4 and 0.1 M NaCl solutions. Scanning electron microscopy was used to examine the morphology of the corroded surfaces after testing.

Kim, H. J.↗