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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Phase evolution during conventional and reactive flash sintering of (Mg,Ni,Co,Cu,Zn)O via in situ X-ray diffraction

Reactive flash sintering (RFS) enables the simultaneous synthesis and sintering of ceramics and has been shown to affect the reaction pathway of different materials. Herein, in situ synchrotron X-ray diffraction (XRD) is used to investigate the (Mg,Ni,Co,Cu,Zn)O entropy-stabilized oxide formation during: (i) conventional heating and (ii) RFS under current rate-controlled mode. The same reaction pathway is verified in both instances: the starting rock-salt (RS), spinel (Co 3 O 4 ), tenorite (CuO), and wurtzite (ZnO) phases transform into a single RS phase with a (1 1 1) to (2 0 0) intensity ratio of 0.67, consistent with a random distribution of the cations into the structure. Pt lattice peak shift from the XRD patterns is used as standard to monitor the sample surface temperature, revealing a strong endothermic reaction during the RS single-phase formation (Pt peaks shift toward higher angles while increasing sample temperature/current density). Furthermore, in RFS, the single-phase RS structure is formed in just 60 s at a furnace temperature of 600°C and a current rate of 220 mA mm -2 /min. Therefore, RFS greatly accelerates the synthesis of (Mg,Ni,Co,Cu,Zn)O, however, it does not play a role in the reaction pathway for this material formation.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Microstructure, Texture, and Strength Development during High-Pressure Torsion of CrMnFeCoNi High-Entropy Alloy

The equiatomic face-centered cubic high-entropy alloy CrMnFeCoNi was severely deformed at room and liquid nitrogen temperature by high-pressure torsion up to shear strains of about 170. Its microstructure was analyzed by X-ray line profile analysis and transmission electron microscopy and its texture by X-ray microdiffraction. Microhardness measurements, after severe plastic deformation, were done at room temperature. It is shown that at a shear strain of about 20, a steady state grain size of 24 nm, and a dislocation density of the order of 1016 m−2 is reached. The dislocations are mainly screw-type with low dipole character. Mechanical twinning at room temperature is replaced by a martensitic phase transformation at 77 K. The texture developed at room temperature is typical for sheared face-centered cubic nanocrystalline metals, but it is extremely weak and becomes almost random after high-pressure torsion at 77 K. The strength of the nanocrystalline material produced by high-pressure torsion at 77 K is lower than that produced at room temperature. The results are discussed in terms of different mechanisms of deformation, including dislocation generation and propagation, twinning, grain boundary sliding, and phase transformation.

36 MATERIALS SCIENCE↗
DOE OSTI2022

On the high-temperature stability of the Al 8 Cu 3 Ce intermetallic in an additively manufactured Al-Cu-Ce-Zr alloy

High-temperature resistant eutectic Al alloys are crucial materials for lightweight and energy efficient design in the automotive and aviation industries. Additive manufacturing offers a pathway to refine eutectic microstructures and develop novel alloys with superior high-temperature strength. High-volume fraction intermetallic Al-Cu-Ce alloys have been developed to deliver high-temperature strength in combination with reduced hot-tearing susceptibility. Zr is added to provide additional strengthening via nanoscale Al 3 Zr precipitation, and to stabilize and avoid coarsening of the Al 8 Cu 3 Ce phase. However, the detailed interaction between Zr and Al 8 Cu 3 Ce remains unexplored. In this work, we show with synchrotron X-ray diffraction that laser powder bed fusion fabricated Al-Cu-Ce and Al-Cu-Ce-Zr alloys contain predominantly the Al 8 Cu 3 Ce intermetallic in the as-fabricated condition. Heat treatment of the Al-Cu-Ce alloy results in the Al 8 Cu 3 Ce → Al 8 Cu 4 Ce phase transformation. In the Al-Cu-Ce-Zr alloy, minor fractions of (Al,Cu,Si) 4 Ce and Al 2 Cu-θ are found in the as-fabricated condition, while Al 8 Cu 3 Ce remains stable during heat treatment. Atom probe microscopy quantifies intermetallic stoichiometries and reveals how Zr is enriched at the Al-matrix/Al 8 Cu 3 Ce interface acting as a diffusion barrier against solute exchange. Calibrated thermodynamic modeling underpins this as a kinetic effect. Here, a qualitative microstructural model summarizes, how Zr stabilizes Al 8 Cu 3 Ce against phase transformations and coarsening.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Effective Lanthanide Diffusivity through U-Zr Metallic Fuel

Fuel-cladding chemical interaction (FCCI) is one of the main concerns for the performance of U-Zr metallic fuels. Although FCCI results in complex phase transformations and morphological changes in both the fuel and cladding sides of the interface, the formation of a brittle layer in the cladding side of the interface (sometimes referred to as wastage) has one of the most significant impacts on the cladding mechanical integrity. This brittle layer is associated with the formation of intermetallic compounds between the cladding constituents Fe, Cr and the lanthanide fission product species. The formation of this cladding wastage layer has been the focus of recent efforts to develop a mechanistic modeling framework, including production of lanthanides in the fuel, transport through the fuel to the fuel-cladding interface, and phase transformation to form intermetallic phases. To calculate the rate of transport of lanthanides through the fuel, a multi-scale computational approach has been used. Atomistic calculations have been performed to determine the diffusivities of Nd, the most prevalent lanthanide species, through the solid fuel matrix and along pore surfaces. These diffusivities have been used as input parameters for a mesoscale model to determine an effective diffusion coefficient that accounts for the formation of porosity, its interconnection, and infiltration with bond sodium from the fuel-cladding gap. The effective diffusivity has been used in engineering-scale simulations using the BISON fuel performance code, and BISON simulations have been compared to representative validation cases from the EBR-II reactor.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Redox Chemistry of the Subphases of α-CsPbI2Br and β-CsPbI2Br: Theory Reveals New Potential for Photostability

The logic in the design of a halide-mixed APb(I 1-x Br x ) 3 perovskite is quite straightforward: to combine the superior photovoltaic qualities of iodine-based perovskites with the increased stability of bromine-based perovskites. However, even small amounts of Br doped into the iodine-based materials leads to some instability. In the present report, using first-principles computations, we analyzed a wide variety of α-CsPbI 2 Br and β-CsPbI 2 Br phases, compared their mixing enthalpies, explored their oxidative properties, and calculated their hole-coupled and hole-free charged Frenkel defect (CFD) formations by considering all possible channels of oxidation. Nanoinclusions of bromine-rich phases in α-CsPbI 2 Br were shown to destabilize the material by inducing lattice strain, making it more susceptible to oxidation. The uniformly mixed phase of α-CsPbI 2 Br was shown to be highly susceptible towards a phase transformation into β-CsPbI 2 Br when halide interstitial or halide vacancy defects were introduced into the lattice. The rotation of PbI 4 Br 2 octahedra in α-CsPbI2Br allows it either to transform into a highly unstable apical β-CsPbI 2 Br, which may phase-segregate and is susceptible to CFD, or to phase-transform into equatorial β-CsPbI 2 Br, which is resilient against the deleterious effects of hole oxidation (energies of oxidation >0 eV) and demixing (energy of mixing <0 eV). Thus, the selective preparation of equatorial β-CsPbI 2 Br offers an opportunity to obtain a mixed perovskite material with enhanced photostability and an intermediate bandgap between its constituent perovskites.

36 MATERIALS SCIENCE↗
DOE OSTI2026

U.S. Distribution Transformer Demand Phase III - Key Drivers and Managing Demand [Slides]

This presentation demonstrates a significant analysis, on forecasting the demand for distribution transformers. The analysis is conducted for the United States, estimating the initial in-service capacity of these assets, and forecasting demand for these assets through 2050 with several sensitivities conducted. It examines not only demand for these assets, but importantly, how utility planning practices can impact the demand for theses assets in time. Under load growth scenarios, whether utilities practice like-for-like replacement strategies as failures occur, or whether they practice proactive up-sizing, anticipating electric load growth, can have major impacts on future demand. It also examines several other growth factors, such as the increasing demand for step-up transformers, which share many of the same characteristics as distribution transformers, and the demand for specific transformers for large project growth from data centers.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2026

Oxide nucleation via threshold-driven volume instability in Ni oxidation

Oxide nucleation dictates the onset of metal oxidation, yet the atomistic pathways bridging initial oxygen adsorption to bulk phase transformation remain elusive. Here, we utilize in-situ atomic-resolution imaging to directly capture the nucleation of nickel oxide, revealing a threshold-driven, cooperative transformation of Ni into NiO. Our observations identify a distinct incubation period during which oxygen progressively accumulates in subsurface layers. Once a critical concentration and penetration depth are reached, a collective lattice reconfiguration is triggered, abruptly converting multiple Ni layers into NiO. Atomistic simulations corroborate this mechanism, identifying a cooperative lattice instability induced by subsurface oxygen saturation. These results establish subsurface oxygen incorporation as the missing mechanistic link between surface adsorption and three-dimensional oxide formation, providing an atomistic framework to understand and control reactive phase transformations in materials synthesis, catalysis, and degradation.

36 MATERIALS SCIENCE↗
DOE OSTI2018

First-Principles and Thermodynamic Simulation of Elastiс Stress Effect on Energy of Hydrogen Dissolution in Alpha Iron

Mobile hydrogen, when dissolving in metals, redistributes due to the density gradients and elastic stresses, and enables destruction processes or phase transformations in local volumes of a solvent metal. It is rather important in solid state physics to investigate these interactions. The first-principle calculations performed in terms of the density functional theory, are used for thermodynamic simulation of the elastic stress effect on the energy of hydrogen dissolution in α-Fe crystal lattice. The paper presents investigations of the total energy of Fe–H system depending on the lattice parameter. As a result, the relation is obtained between the hydrogen dissolution energy and stress. A good agreement is shown between the existing data and simulation results. The extended equation is suggested for the chemical potential of hydrogen atom in iron within the local stress field. Two parameters affecting the hydrogen distribution are compared, namely local stress and phase transformations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

From classical thermodynamics to phase-field method

Phase-field method is a density-based computational method at the mesoscale for modeling and predicting the temporal microstructure and property evolution during materials processes. The focus of this article is on connecting the most common phase-field equations to the very basic first and second laws of classical thermodynamics through rudimentary irreversible thermodynamics. It briefly discusses the relations of the continuum phase-field equations to their counter parts at the microscopic and atomic levels. It attempts to clarify the contributions of long-range elastic, electrostatic, and magnetic interactions to domain structure evolution during structural, ferroelectric, and ferromagnetic phase transformations by separating order parameter changes due to the presence of quasi-static fields and those arising from phase transformations. A few examples are presented to demonstrate the possibility of employing the phase-field method to provide guidance to designing materials for optimum properties or discovering novel mesoscale phenomena or new materials functionalities. Here, the article ends with a brief perspective on a number of potential future directions on the development and applications of phase-field method beyond its traditional applications to structural alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Fabrication and characterization of a novel β metastable Ti-Mo-Zr alloy with large ductility and improved yield strength

Highlights: • Ti-12Mo-5Zr alloy exhibits excellent combination of improved yielding strength (>650 MPa), high ductility (uniform elongation ≈30%) and work-hardening behaviour. • The superior performances arise from the synergic effects between phase transformation induced plasticity and twinning induced plasticity. • The ‘d-electron’ alloy design approach in Ti-12Mo-5Zr alloy, i.e. Zr substitution to Ti, validates the feasibility of yielding stress improvement of TWIP/TRIP titanium alloys. - Abstract: In this paper, a novel ternary β-metastable titanium alloy, Ti-12Mo-5Zr (wt%), was designed based on the “d-electron” alloy design theory. The Ti-12Mo-5Zr alloy displays excellent combination of improved yielding stress (>650 MPa), high ductility (uniform elongation ≈30%) and work-hardening behaviour. The detailed microstructural analysis indicates that the superior performances arise from the synergic effects between phase transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP). Conforming to the design strategy, the improvement of mechanical performance results from the addition of Zr alloying element in substituting Ti, attributing to solution hardening effect and the increasing of critical resolved shear stress (CRSS) of stress induced martensitic transformation (SIM α″).

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effects of Heat Input on Weld-Bead Geometry, Surface Chemical Composition, Corrosion Behavior and Thermal Properties of Fiber Laser-Welded Nitinol Shape Memory Alloy

Bead-on-plate laser welding was carried out on 1-mm-thick Nitinol sheets at different heat input values. The variations in weld-bead geometry and variations in microstructures across the bead were studied. The effects of heat input on surface layer composition of the welded samples, corrosion properties and phase transformation temperature were examined. From x-ray photoelectron spectroscopy (XPS), it was clear that relative intensity of elemental Ni peak was higher in parent material and the oxidation state of Ti was Ti{sup 4+}. It was further observed from Auger electron spectroscopy (AES) that the Ti to Ni ratio on the top surface of the welded samples was more than 1, and as a result of this the stability of TiO{sub 2} layer was enhanced, which eventually helped to improve the corrosion property of the welded samples. The polarization resistance of the welded samples was increased by more than ten times compared to that of the un-welded samples. From differential scanning calorimetry (DSC), it became evident that phase transformation temperatures got changed due to welding.

36 MATERIALS SCIENCE↗
NASA NTRS1981

Heat storage in alloy transformations

The feasibility of using metal alloys as thermal energy storage media was determined. The following major elements were studied: (1) identification of congruently transforming alloys and thermochemical property measurements; (2) development of a precise and convenient method for measuring volume change during phase transformation and thermal expansion coefficients; (3) development of a numerical modeling routine for calculating heat flow in cylindrical heat exchangers containing phase change materials; and (4) identification of materials that could be used to contain the metal alloys. Several eutectic alloys and ternary intermetallic phases were determined. A method employing X-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation from data obtained during one continuous experimental test. The method and apparatus are discussed and the experimental results are presented. The development of the numerical modeling method is presented and results are discussed for both salt and metal alloy phase change media.

Birchenall, C. E.↗
DOE OSTI2017

Synthesis and characterization of iodosodalite

Abstract The effects of six process variables were investigated on the hydrothermal growth of iodosodalite, Na 8 Al 6 Si 6 O 24 I 2 : pH (Na OH concentration), aging time, temperature, Al/Si ratio, precursors used (i.e., zeolite 4A, kaolinite, meta‐kaolin, colloidal silica, and sodium aluminate), and precursor concentration. Powder X‐ray diffraction ( XRD ) with Rietveld refinements, X‐ray photoelectron spectroscopy ( XPS ), Fourier transform infrared spectroscopy ( FTIR ), and scanning electron microscopy ( SEM ) were performed to characterize the structures, phase fractions, chemical state, and surface morphology of the synthesized products. Iodosodalite yield increased as aging time and pH increased. The crystallization of iodosodalite was favored in the temperature range 140°C‐180°C. Decreasing the Al/Si ratio by half increased the crystallization of basic cancrinite. Lowering the precursor concentration by adding water revealed the crystallization of nepheline hydrate I and a decrease in the sodalite fraction. Among the tested precursors, zeolite 4A yielded the highest mass fraction of iodosodalite in the synthesized powders. From the aging time and temperature variation experiments, the phase transformation of zeolite A→sodalite→cancrinite was observed. XPS and FTIR results showed the presence of only iodide but not iodate in the synthesized product. The crystallization of various minerals suggests that mechanisms for transport of the ions and formation of the aluminosilicate frameworks vary with hydrothermal conditions.

Chong, Saehwa↗
DOE OSTI2018

Influence of nitrogen content levels on structural properties and photocatalytic activities of nanorice-like N-doped TiO2 with various calcination temperatures

Highlights: • Hydrothermal method enhances the integration of N species into TiO{sub 2}. • TiO{sub 2} doping with nitrogen prevents the phase transformation from anatase to rutile. • The N-doped TiO{sub 2} exhibits nanorice-like morphology. • Nitrogen atom incorporates into the lattice of TiO{sub 2} with interstitial site (TiON). • Nitrogen doping content in TiO{sub 2} accelerates the kinetic rate of photocatalytic reaction. - Abstract: The purposes of this research were to study the effect of nitrogen content levels on structural properties and photocatalytic activities of catalysts with various calcination temperatures and to test the photocatalytic degradation of paraquat under UV and visible light. The results showed that the effect of calcination temperature was significant on physical properties and amount of nitrogen element, but insignificant on phase structure and oxidation state of titanium (Ti) atom. The N-doped TiO2 samples demonstrated only anatase phase because nitrogen dopant in TiO2 restrained the phase transformation from anatase to rutile and displayed nanorice-like morphology. The bandgap energy was about 3.07–3.18 eV. The nitrogen content was only observed at 100, 300 and 400 °C. The nitrogen (N) atom can be incorporated in TiO2 structural lattice with interstitial site. The specific surface area and nitrogen content level showed the important roles for the photodegradation of paraquat under UV and visible light irradiation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Mechanical properties, deformation behavior and microstructure evolution of Ti-43Al-6Nb-1Mo-1Cr alloys

Highlights: • The alloys exhibit excellent high-temperature tensile properties. • Activation energy of deformation (Q) and n are 571 KJ/mol and 2.765, respectively. • The hot processing maps of strain 0.5 and 0.6 are displayed. • Phase transformations and microstructure evolution are explained in different conditions. • Three types of deformation mechanisms are exhibited at different temperature. - Abstract: The high-temperature properties, microstructure evolution and deformation behavior of a novel Ti-43Al-6Nb-1Mo-1Cr(at.%) alloy were studied in this paper. The ultimate tensile strength (UTS) and elongation (δ) were tested at 800, 850, and 900 °C, in which the excellent strength 551 MPa, 510 MPa, and 382 MPa, and elongation 2.9%, 12.7%, and 16.8% were exhibited, respectively. Isothermal compression tests were carried out in the temperature range of 1100–1250 °C and strain rate range of 0.001–1.0 s{sup − 1}. Based on dynamic materials model (DMM) and phase diagram, dynamic recrystallization mechanism and phase transformation during thermal deformation were clarified and the hot processing maps were calculated. The experimental results show that the values of stress exponent (n) and the apparent deformation activation energy (Q) of Ti-43Al-6Nb-1Mo-1Cr(at.%) were calculated to be 2.77 and 571 KJ/mol. Meanwhile, three various types of microstructure evolution in different deformation conditions were discussed and concluded.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Real-time monitoring of laser powder bed fusion process using high-speed X-ray imaging and diffraction

Here, we employ the high-speed synchrotron hard X-ray imaging and diffraction techniques to monitor the laser powder bed fusion (LPBF) process of Ti-6Al-4V in situ and in real time. We demonstrate that many scientifically and technologically significant phenomena in LPBF, including melt pool dynamics, powder ejection, rapid solidification, and phase transformation, can be probed with unprecedented spatial and temporal resolutions. In particular, the keyhole pore formation is experimentally revealed with high spatial and temporal resolutions. The solidification rate is quantitatively measured, and the slowly decrease in solidification rate during the relatively steady state could be a manifestation of the recalescence phenomenon. The high-speed diffraction enables a reasonable estimation of the cooling rate and phase transformation rate, and the diffusionless transformation from β to α’ phase is evident. The data present here will facilitate the understanding of dynamics and kinetics in metal LPBF process, and the experiment platform established will undoubtedly become a new paradigm for future research and development of metal additive manufacturing.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Heteroatom anchoring to enhance electrochemical reversibility for high-voltage P2-type oxide cathodes of sodium-ion batteries

P2-type cathode has received extensive attention due to its faster Na+ diffusion and a high theoretical capacity in sodium-ion batteries (SIBs). However, undesirable phase transformations have induced dramatic capacity decay of SIBs during the cycling process. In this study, heteroatom anchoring through Cu/Mg dual doping is introduced into P2-type Na 0.67 Ni 0.33 Mn 0.67 O 2 cathode to enhance high-voltage electrochemical reversibility and modulate interfacial Na + kinetics. Further, the as-prepared Na 0.67 Ni 0.23 Mg 0.05 Cu 0.05 Mn 0.67 O 2 exhibits an outstanding capacity retention (83.4% after 2000 cycles at 10C) and rate performance (73 mAh g -1 at 10C, accounting for 58.7% of that at 0.1 C) over the voltage range of 2.5–4.4 V. Intensive explorations further manifest that the modified mechanism of dual-ion doping strategy is attributed to the synergistic coupling effect of a substantial change in Na occupancy distribution and an increase in oxygen vacancy buffer. Thus, the optimized cathode expedites Na + diffusion and reduces detrimental phase transformation, which favors high-rate performance and long-term cycling stability. This study develops a route to rationally design high-voltage cathode materials for SIBs.

25 ENERGY STORAGE↗