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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Preparation and Thermoelectric Properties of IR(sub x)Co(sub 1-x)Sb(sub 2) Alloys

The preparation and characterization of the binary arsenopyrite compounds CoSb2 and IrSb2 and IrxCo1-xSb2 alloys is reported. Single crystals of CoSb2 were grown by the vertical gradient freeze technique from solution rich in antimony. Polycrystalline samples of IrSb2 and IrxCo1-xSb2 alloys were prepared by hot-pressing of prereacted elemental powders. Samples were investigated by X-ray diffractometry, microprobe analysis and density measurements. It was found that a range of solid solution exist in the system IrxCo1-xSb2 for 0.1<x<0.8. Samples were also characterized by high temperature electrical resistivity, Seebeck coefficient and thermal conductivity measurements. All materials have p-type conductivity and are semiconductors. A band gap of about 0.98 eV was calculated for IrSb2. Preliminary measurements of the thermoelectric properties of these materials showed that their potential for thermoelectric applications is limited.

Thermoelectric Properties↗
DOE OSTI2021

Spin and Orbital Effects on Asymmetric Exchange Interaction in Polar Magnets: M(IO 3 ) 2 (M = Cu and Mn)

We report magnetic polar materials feature an astonishing range of physical properties, such as magnetoelectric coupling, chiral spin textures, and related new spin topology physics. This is primarily attributable to their lack of space inversion symmetry in conjunction with unpaired electrons, potentially facilitating an asymmetric Dzyaloshinskii–Moriya (DM) exchange interaction supported by spin–orbital and electron–lattice coupling. However, engineering the appropriate ensemble of coupled degrees of freedom necessary for enhanced DM exchange has remained elusive for polar magnets. Here, we study how spin and orbital components influence the capability of promoting the magnetic interaction by studying two magnetic polar materials, α-Cu(IO 3 ) 2 ( 2 D) and Mn(IO 3 ) 2 ( 6 S), and connecting their electronic and magnetic properties with their structures. The chemically controlled low-temperature synthesis of these complexes resulted in pure polycrystalline samples, providing a viable pathway to prepare bulk forms of transition-metal iodates. Rietveld refinements of the powder synchrotron X-ray diffraction data reveal that these materials exhibit different crystal structures but crystallize in the same polar and chiral P2 1 space group, giving rise to an electric polarization along the b-axis direction. The presence and absence of an evident phase transition to a possible topologically distinct state observed in α-Cu(IO 3 ) 2 and Mn(IO 3 ) 2 , respectively, imply the important role of spin–orbit coupling. Neutron diffraction experiments reveal helpful insights into the magnetic ground state of these materials. While the long-wavelength incommensurability of α-Cu(IO 3 ) 2 is in harmony with sizable asymmetric DM interaction and low dimensionality of the electronic structure, the commensurate stripe AFM ground state of Mn(IO 3 ) 2 is attributed to negligible DM exchange and isotropic orbital overlapping. The work demonstrates connections between combined spin and orbital effects, magnetic coupling dimensionality, and DM exchange, providing a worthwhile approach for tuning asymmetric interaction, which promotes evolution of topologically distinct spin phases.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1996

Elevated Temperature Compressive Properties of Zr-Modified Nial

Small Zr additions are known to substantially affect the deformation behavior and strength of polycrystalline NiAl, yet little information is currently available regarding the high-temperature properties of such alloys. Utilizing prealloyed powder technology, a series of four NiAl alloys have been produced containing from 0.05 to 0.7 at. pct Zr. The creep behavior of these alloys was characterized in compression between 1000 and 1400 K at strain rates ranging from approx. O.1 to 10(exp -9)/ sec. All the Zr-modified alloys were significantly stronger than binary NiAl under lower temperature and faster strain-rate conditions; however, the single-phase materials (Zr less than or equal to 0.1 at. pct) and binary NiAl had similar strengths at high temperatures and slow strain rates. The two-phase NiAl-Ni, AlZr alloys containing 0.3 and 0.7 at. pct Zr had nearly identical strengths. While the two-phase alloys were stronger than the single-phase materials at all test conditions, the degree of microstructural damage in the two-phase alloys due to internal oxidation during testing appeared to increase with Zr level. Balancing the poor oxidation behavior with the consistent strength advantage of the two-phase alloys, it is concluded that optimum elevated-temperature properties could be obtained in Heusler-strengthened NiAl containing between 0.1 and 0.3 at. pct Zr.

Whittenberger, J. Daniel↗
DOE OSTI2025

Localized triplons and site stuffing in the quantum dimer magnet BiYbGeO5

Thermodynamic and muon spin relaxation measurements have recently highlighted BiYbGeO5 as a new example of a rare-earth-based quantum dimer magnet with isolated Yb3+ spin-1/2 dimers. However, direct spectroscopic evidence of the triplet excitations and measurements of the structural disorder are lacking. In this work, polycrystalline BiYbGeO5 was synthesized using conventional high-temperature solid-state methods and investigated via high-resolution neutron powder diffraction and inelastic neutron scattering. Diffraction measurements down to 58 mK reveal no signatures of magnetic order and indicate that nearly 20% of Yb3+ sites are replaced by nonmagnetic Bi3+, introducing significant structural disorder. Inelastic neutron scattering shows dispersionless triplon excitations, consistent with localized, noninteracting spin dimers. Fits to the triplet excitation spectrum with an XXZ-type anisotropic exchange give 𝐽XX=0.100⁢(1)⁢meV and 𝐽Z=0.202⁢(1)⁢meV. These findings establish BiYbGeO5 as a structurally disordered but magnetically well-isolated quantum dimer system, providing a model platform for studying the resilience of entangled spin states to site dilution.

Kapoor, Rachit [Brock University, Canada]↗
DOE OSTI2023

Equibiaxial flexural strength determination of UO 2 using a ball-on-ring test

To increase nuclear fuel performance and reliability, their mechanical properties require an accurate and statistically relevant assessment. Biaxial flexural strength tests provide an alternative to bend bar techniques for assessing mechanical behavior; namely, the transverse rupture strength (TRS) of ceramic samples. Biaxial test samples require simple geometries and minimal surface preparation, reducing fabrication costs and handling hazards. This study investigated the TRS of polycrystalline UO 2 fuel forms at room temperature using a ball-on-ring test fixture. Here, pellets were fabricated from UO 2 powder using conventional powder processing and sintering techniques. The TRS and Weibull parameters were obtained through Weibull statistics on over 60 UO 2 samples tested under equibiaxial flexure. The larger sample size in this study enabled a more robust Weibull statistical analysis than alternative test methods, which may not capture the stochastic failure of typical ceramics. Furthermore, two different loading ball diameters were employed to assess the impact of contact damage on fracture strength. While Hertzian contact damage was observed with the smaller loading ball, the fracture strength remained unaffected. A fracture analysis of the tested UO 2 samples indicated a mixture of intergranular and transgranular fracture that transitions to transgranular fracture with increasing distance from the fracture origin. The characteristic strength of the combined data sets was determined to be 148 MPa, and the Weibull modulus was determined to be 9.1. The TRS values and Weibull parameters were close to values found in the literature for alternative testing techniques using samples with similar microstructure and density. The findings in this study validate the ball-on-ring method used to obtain the TRS of UO 2 with a sample geometry more representative of nuclear fuels. Additionally, experimental TRS results from this study can be implemented in modeling codes to predict fuel performance, which is critical to fuel burnup extension and advanced nuclear fuel technologies.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Ferromagnetism in Pr-rich binary Pr 7 Ru 3 intermetallic compound

We present the synthesis and experimental characterization of the binary intermetallic compound Pr 7 Ru 3 . The polycrystalline sample was prepared by arc melting pure Pr and Ru, followed by homogenization at 500 °C and 600 °C for 48 and 89 h, respectively. Powder x-ray diffraction confirms that Pr 7 Ru 3 crystallizes in an orthorhombic crystal structure (Pnma, space group no. 62) with the lattice parameters: a = 7.3606(7) Å, b = 23.120(1) Å and c = 6.5959(5) Å. Magnetization, resistivity, and heat capacity measurements reveal a ferromagnetic transition in Pr 7 Ru 3 with the Curie temperature T C ~ 24.5 K. The bulk transition is confirmed by a large λ-shape anomaly observed in the specific heat measurement. The magnetic susceptibility above the transition obeys the modified Curie-Weiss law with a positive Curie-Weiss temperature $\ominus$ CW = 30(1) K and an effective magnetic moment of 3.39(1) μ B /Pr. Resistivity data for Pr 7 Ru 3 reveals metallic-like behavior with a clear anomaly at the transition temperature which is smeared by an applied magnetic field. We also synthesized high-quality nonmagnetic analog La 7 Ru 3 for which superconducting transition is observed with T c = 1.95 K, in agreement with the literature.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Crystal plasticity finite element simulation of lattice rotation and x-ray diffraction during laser shock compression of tantalum

Here we present a crystal plasticity model tailored for high-pressure, high-strain-rate conditions that uses a multiscale treatment of dislocation-based slip kinetics. We use this model to analyze the pronounced plasticity-induced lattice rotations observed in shock-compressed polycrystalline tantalum via in situ x-ray diffraction. By making direct comparisons between experimentally measured and simulated texture evolution, we can explain how the details of the underlying slip kinetics control the degree of lattice rotation that ensues. Specifically, we show that only the highly nonlinear kinetics caused by dislocation nucleation can explain the magnitude of the rotation observed under shock compression. We demonstrate a good fit between our crystal plasticity model and x-ray diffraction data and exploit the data to quantify the dislocation nucleation rates that are otherwise poorly constrained by experiment in the dynamic compression regime.

36 MATERIALS SCIENCE↗
NASA NTRS2018

Thermophysical Properties of Nickel-Based Superalloys

The NASA Marshall Space Flight Center (MSFC) electrostatic levitation (ESL) laboratory has a long history of providing materials research and thermophysical property data. The lab can measure thermophysical properties such as density, surface tension, and viscosity of liquid materials, including elements, alloys, glasses, ceramics, and oxides. Nickel-based superalloys (e.g. Inconel, Hastelloy, and Waspaloy) have many high performance applications, including turbine engines for aerospace. Superalloy parts are typically manufactured by casting and forging. These processes generate both polycrystalline and monocrystalline parts. A relatively new method of fabrication of turbine disk materials is additive manufacturing, which is typically done for aerospace parts by powder-bed methods such as selective laser melting (SLM). Accurate modeling of casting and forging, as well as additively manufacturing processes, require thermophysical properties (density, surface tension, and viscosity). The thermophysical properties of liquid nickel-based superalloys, both conventional and additively manufactured, were measured at several temperatures in both undercooled and superheated condition. Surface tension and viscosity was measured using the oscillating drop method and density and thermal expansion was measured using edge detection methods.

SanSoucie, Michael P.↗
DOE OSTI2020

In situ X-ray measurements over large Q-space to study the evolution of oxide thin films prepared by RF sputter deposition

Sputter deposition is a versatile and industrially important deposition technique for thin films, with increasing demand for matching the characteristics of thin film materials to specific requirements. Additionally, the actual film properties are largely determined by sputtering parameters such as pressure conditions, temperature and power settings. By means of various X-ray diffraction and scattering techniques, it is shown that the characterization of film formation and growth is feasible in real time at synchrotron sources, thus adding an important dimension to the fundamental understanding of the evolution of thin film microstructure. In particular, grazing incidence small-angle X-ray scattering, grazing incidence X-ray powder diffraction and X-ray reflectometry are used in a complementary manner to study the influence of deposition temperature and substrate choice on the crystallization kinetics and growth of polycrystalline BaTiO 3 films.

36 MATERIALS SCIENCE↗
NASA NTRS1991

Applications of diamond films and related materials; Proceedings of the 1st International Conference, Auburn, AL, Aug. 17-22, 1991

The present conference discusses the nucleation and growth of diamond from hydrocarbons, the cutting tool performance of CVD thick-film diamond, the characterization of CVD diamond grinding powder, industrial applications of crystalline diamond-coated tools, standardized SEM tribometry of diamond-coated substrates, residual stress in CVD diamond films, the optical properties of CVD diamond films, polycrystalline diamond films for optical applications, and diamond growth on ferrous metals. Also discussed are ion beam-irradiation smoothing of diamond films, electronic circuits on diamond substrates, diamond-laminated surfaces for evaporative spray cooling, electron devices based on the unique properties of diamond, diamond cold cathodes, thin-film diamond microstructure applications, Schottky diodes from flame-grown diamond, diamond films for thermionic applications, methods of diamond nucleation and selective deposition, high-rate/large-area diamond film production, halogen-assisted diamond growth, the economics of diamond technology, and the optical and mechanical properties of diamondlike films.

Tzeng, Yonhua↗
NASA NTRS1995

Assessment of microalloying effects on the high temperature fatigue behavior of NiAl

Binary NiAl suffers from a lack of strength and poor creep properties at and above 1000 K. Poor creep resistance in turn affects low cycle fatigue (LCF) lives at low strain ranges due to the additional interactions of creep damage. One approach for improving these properties involved microalloying with either Zr or N. As an integral part of a much larger alloying program the low cycle fatigue behavior of Zr and N doped nickel aluminides produced by extrusion of prealloyed powders has been investigated. Strain controlled LCF tests were performed in air at 1000 K. The influence of these microalloying additions on the fatigue life and cyclic stress response of polycrystalline NiAl are discussed.

Noebe, R. D.↗
NASA NTRS1987

Effect of the microstructure on the thermoelectric properties of polycrystalline lanthanum chalcogenides

Small amounts of second phase materials can have important effects on the thermoelectric properties of polycrystalline gamma-La(3-x)X4 (X-S, Te; X in the range of 0 to 1/3). Microscopic examination by SEM of hot pressed La(3-x)Te4 samples has revealed from 1-5 vol. pct of La2O2Te, an amount which is not detected by X-ray powder diffraction measurements. This amount of La2O2Te resulting from oxygen contamination can reduce the concentration of electrons by as much as 10 to 75 percent below the electron concentration calculated for single phase La(3-x)Te4 in the composition range of greatest interest. Small amounts of second phase materials can also lower the lattice thermal conductivity by scattering low frequency phonons. These results indicate that microstructural effects should be considered when electrical and thermal properties of polycrystalline materials are analyzed.

Lockwood, A.↗
DOE OSTI2021

Potential Skyrmion Host Fe(IO3)3: Connecting Stereoactive Lone-Pair Electron Effects to the Dzyaloshinskii-Moriya Interaction

Magnetic skyrmions, which are topologically distinct magnetic spin textures, are gaining increased attention for their unique physical properties and potential applications in spintronic devices. Here we present a design strategy for skyrmion host candidates based on combinations of magnetic spin, asymmetric building units having stereoactive lone-pair electrons, and polar lattice symmetry. To demonstrate the viability of the proposed rational design principles, we successfully synthesized a Fe(IO 3 ) 3 polycrystalline sample and single crystals by using a new simplified low-temperature pathway, which is experimentally feasible for extending materials growth of transition metal iodates. Single crystal X-ray and powder synchrotron X-ray diffraction measurements demonstrated that Fe(IO 3 ) 3 crystallizes in the polar chiral hexagonal lattice with space group P63. The combined structural features of the macroscopic electric polarization along the c-axis stemming from the coalignment of the stereoactive lone-pairs of the IO 3 – trigonal pyramid and the magnetic Fe 3+ cation residing on the 3-fold rotation axis were selected to promote asymmetric exchange coupling. We find evidence of a predicted skyrmion phase at 14 K ≤ T ≤ 16 K and 2.5 T ≤ μ 0 H ≤ 3.2 T driven by a Dzyaloshinskii–Moriya (DM) interaction, a conclusion supported by the appreciable DM exchange and the zero-field spiral antiferromagnetic ground state of Fe(IO 3 ) 3 deduced from neutron diffraction experiments. The associated magnetic modulation wavelength of the putative skyrmions is expected to be short ~18 nm, comparable to the period of the DM-driven incommensurate order. This work links stereoactive lone-pair electron effects to enhanced DM interaction, demonstrating a new approach for chemical guidelines in the search for skyrmionic states of matter.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Nucleation of Dislocations in 3.9 nm Nanocrystals at High Pressure

As circuitry approaches single nanometer length scales, it has become important to predict the stability of single nanometer-sized metals. The behavior of metals at larger scales can be predicted based on the behavior of dislocations, but it is unclear if dislocations can form and be sustained at single nanometer dimensions. Here, we report the formation of dislocations within individual 3.9 nm Au nanocrystals under nonhydrostatic pressure in a diamond anvil cell. We used a combination of x-ray diffraction, optical absorbance spectroscopy, and molecular dynamics simulation to characterize the defects that are formed, which were found to be surface-nucleated partial dislocations. These results indicate that dislocations are still active at single nanometer length scales and can lead to permanent plasticity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1995

Effect of Processing Route on Strain Controlled Low Cycle Fatigue Behavior of Polycrystalline NiAl

The present investigation examines the effects of manufacturing process on the total axial strain controlled low cycle fatigue behavior of polycrystalline NiAl at 1000 K, a temperature above the monotonic Brittle-to-Ductile Transition Temperature (BDTT). The nickel aluminide samples were produced by three different processing routes: hot isostatic pressing of pre- alloyed powders, extrusion of prealloyed powders, and extrusion of vacuum induction melted ingots. The LCF behavior of the cast plus extruded material was also determined at room temperature (below the BD77) for comparison to the high temperature data. The cyclic stress response, cyclic stress-strain behavior, and strain-life relationships were influenced by the alloy preparation technique and the testing temperature. Detailed characterization of the LCF tested samples was conducted by optical and electron microscopy to determine the variations in fracture and deformation modes and to determine any microstructural changes that occurred during LCF testing. The dependence of LCF properties on processing route was rationalized on the basis of starting microstructure, brittle-to-ductile transition temperature, deformation induced changes in the basic microstructure, deformation substructure, and synergistic interaction between the damage modes.

Rao, K. Bhanu Sankara↗
NASA NTRS1987

Effect of composition and grain size on slow plastic flow properties of NiAl between 1200 and 1400 K

A series of about 15-micron diameter polycrystalline B2 crystal structure NiAl alloys ranging in composition from 43.9 to 52.7 Al (at. pct) have been compression tested at constant velocities in air between 1200 and 1400 K. All materials were fabricated via powder metallurgy techniques with hot extrusion as the densification process. Seven intermediate compositions were produced by blending various amounts of two master heats of prealloyed powder; in addition, a tenth alloy of identical composition, 48.25 Al, as one of the blended materials, was produced from a third master heat. Comparison of the flow stress-strain rate behavior for the two 48.25 Al alloys revealed that their properties were identical. The creep strength of materials for Al/Ni not above 1.03 was essentially equal, and deformation could be described by a single stress exponent and activation energy. Creep at low temperatures and faster strain rates is independent of grain sizes and appears to be controlled by a subgrain mechanism. However, at higher temperatures and slower strain rates, diffusional creep seems to contribute to the overall deformation rate.

Whittenberger, J. Daniel↗
DOE OSTI2025

Laser, vacuum and gas reaction chamber for operando measurements at NSLS-II's 28-ID-2

We present a laser reaction chamber that we have developed for in situ/operando X-ray diffraction measurements at the NSLS-II 28-ID-2 X-ray powder diffraction beamline. This chamber allows for rapid and dynamic sample heating under specialized gas environments, spanning ambient conditions down to vacuum pressures. We demonstrate the capabilities of this setup through two applications: laser-driven heating in polycrystalline iron oxide and in single-crystal WTe 2 . Our measurements reveal the ability to resolve chemical reaction kinetics over minutes with 1 s time resolution. This setup advances opportunities for in situ/operando X-ray diffraction studies of both bulk and single-crystal materials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

From Layered Antiferromagnet to 3D Ferromagnet: LiMnBi-to-MnBi Magneto-Structural Transformation

Here, the intermetallic compound LiMnBi was synthesized by the two-step solid-state reaction from the elements. The synthesis temperature of 850 K was selected based on in-situ high-temperature powder X-ray diffraction data. LiMnBi crystalizes in the layered-like PbClF structure type (a = 4.3131(7) Å, c = 7.096(1) Å at 100 K, P4/nmm space group, Z = 2). LiMnBi structure is built of the alternating [MnBi] and Li layers, as determined from single-crystal X-ray diffraction data. Magnetic properties measurements and solid-state 7 Li Nuclear Magnetic Resonance data collected for polycrystalline LiMnBi samples indicate the long-range antiferromagnetic ordering of Mn sublattice at ~340 K, with no superconductivity down to 5 K detected. LiMnBi is air- and water-sensitive. In aerobic conditions, Li can be extracted from LiMnBi structure to form Li 2 O/LiOH and MnBi (NiAs structure type, P6 3 /mmc). The obtained MnBi polymorph was previously reported to be one of the strongest rare-earth-free ferromagnets, yet its bulk synthesis in powder form is cumbersome. The proposed magneto-structural transformation from ternary LiMnBi to ferromagnetic MnBi involves condensation of the MnBi4 tetrahedra upon Li deintercalation and is exclusive to LiMnBi. In contrast, ferromagnetic MnBi cannot be obtained from either isostructural NaMnBi and KMnBi, or from the structurally related CaMn 2 Bi 2 . Such a distinctive transformation in the case of LiMnBi is presumed to be due to its fitting reactivity to yield MnBi and favorable interlayer distance between [MnBi] layers, while the interlayer distance in NaMnBi and KMnBi structural analogs is unfavorably long. The studies of delithiation from the layered-like LiMnBi under different chemical environments indicate that the yield of the MnBi depends on the type of solvent used and the kinetics of the reaction. A slow rate and mild reaction media lead to a high fraction of the MnBi product. The saturation magnetization of the “as-prepared” MnBi is ~50 % of the expected value of 81.3 emu/g. Overall, this study adds a missing member to the family of ternary pnictides and illustrates how soft-chemistry methods can be used to obtain “difficult-to-synthesize” compounds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗