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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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6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Analysis of phase stability and chemical segregation in the Mo-V alloys using a generalized embedded atom method potential

A new interatomic potential for the Mo-V system is introduced to facilitate the study of phase stability and mechanical properties at lower temperatures. This potential is based on a generalization of the embedded atom method and includes contributions from embedding energy, explicit two- and three-body interactions and nonlocal many-body interaction terms. The parameters of the potential are optimized by using data from ab initio density functional theory (DFT) calculations. The potential is rigorously validated across a range of physical properties, such as elastic constants, equation of states, phonon dispersion curves, point defect properties and melting temperatures for different compositions. Even though our potential is trained on a small dataset, its accuracy is comparable to available machine learning potentials for Mo and V. Furthermore, our results show that an ordered B2 phase is stable at low temperatures in alloys containing 50% V, but the solid solution phase is stable above 800 K. However, such long-range ordering is not observed in V-rich or Mo-rich alloys. In addition, our results show that V segregates to dislocation cores and grain boundaries.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Sintering behaviors, phases, and dielectric properties of MO-TeO2-V2O5 (M = Ca, Sr, Ba) ultralow temperature ceramics

Highlights: • Introduction of TeO{sub 2} to MO-V{sub 2}O{sub 5} (M = Ca,Sr,Ba) ceramics promoted a M{sub 2}V{sub 2}O{sub 7} phase formation, and obtain excellent dielectric properties and a densification sintering at below 600°. • Chemical compatibility of ULTCC ceramics with aluminum electrode indicated that aluminum did not react with MO-TeO{sub 2}-V{sub 2}O{sub 5} ceramics. • Aluminum easily encouraged the transformation of M{sub 2}V{sub 2}O{sub 7} structures to M{sub 3}(VO{sub 4}){sub 2} structures and other structures under the ultra-low temperature sintering. - Abstract: Influences of TeO{sub 2} on phase evolutions and sintering behaviors of MO-TeO{sub 2}-V{sub 2}O{sub 5} (M = Ca, Sr, Ba) ultralow temperature ceramics were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Dielectric properties of MO-TeO{sub 2}-V{sub 2}O{sub 5} (M = Ca, Sr, Ba) ceramics and their chemical compatibility with an aluminum electrode were also studied. Introducing TeO{sub 2} to MO-V{sub 2}O{sub 5} (M = Ca, Sr, Ba) ceramics obviously decreased the sintering temperature and promoted formation of M{sub 2}V{sub 2}O{sub 7} (M = Ca, Sr, Ba) phases. Also, dielectric properties mainly depend on the amount of TeO{sub 2} added to MO-TeO{sub 2}-V{sub 2}O{sub 5} ceramics. Investigation of chemical compatibility with aluminum shows that aluminum does not react chemically with MO-TeO{sub 2}-V{sub 2}O{sub 5} ceramics; however, aluminum causes transformation of M{sub 2}V{sub 2}O{sub 7} phases to other phases (such as M{sub 3}(VO{sub 4}){sub 2}) to be easier. Sintering temperature of MO-TeO{sub 2}-V{sub 2}O{sub 5} (M = Ca, Sr, Ba) ceramics can be regulated below 600 °C, which is much less than the melting point of aluminum. In addition, MO-TeO{sub 2}-V{sub 2}O{sub 5} (M = Ca, Ba) ceramics maintain quality factors of ∼18,000 GHZ, a dielectric constant of 10–12, and dielectric loss lower than 10{sup −4}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Analysis of correlations between intrinsic ductility and electronic density of states in refractory alloys

High entropy alloys (HEAs) correspond to a new and emerging class of materials that allows us to explore a large composition space to tune mechanical strength and thermal stability. Therefore, to design better alloys, it is important to scan the high-dimensional space of chemistry, composition and temperature. Here, to facilitate this search, we present a method to screen intrinsically ductile body centered cubic (BCC) refractory alloys from electronic structure calculations by using the density of states (DOS) at the Fermi level, g(μ F ). This correlation between intrinsic ductility and g(μ F ) is tested by analyzing group V (V, Nb, Ta) and VI (Mo, W) refractory metals, binary alloys, such as W-Nb, W-V, Mo-Nb and Mo-V, and refractory alloys for which experimental stress-strain measurements are available. In addition, we perform a high-throughput exploration of the entire composition space of a recently proposed alloy system, CrMoNbV, and identify compositions that exhibit high intrinsic ductility.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Design and synthesis of highly active MoVTeNb-oxides for ethane oxidative dehydrogenation

Ethane oxidative dehydrogenation (ODH) is an alternative route for ethene production. Crystalline M1 phase of Mo-V mixed metal oxide is an excellent catalyst for this reaction. Here we show a hydrothermal synthesis method that generates M1 phases with high surface areas starting from poorly soluble metal oxides. Use of organic additives allows control of the concentration of metals in aqueous suspension. Reactions leading to crystalline M1 take place at 190 °C, i.e., approximately 400 °C lower than under current synthesis conditions. The evolution of solvated polyoxometalate ions and crystalline phases in the solid is monitored by spectroscopies. Catalysts prepared by this route show higher ODH activity compared to conventionally prepared catalysts. The higher activity is due not only to the high specific surface area but also to the corrugated lateral termination of the M1 crystals, as seen by atomic resolution electron microscopy, exposing a high concentration of catalytically active sites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on VMo by Materials Project

MoV crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. V is bonded to six equivalent V and six equivalent Mo atoms to form VV6Mo6 cuboctahedra that share corners with eighteen equivalent VV6Mo6 cuboctahedra, edges with six equivalent VV6Mo6 cuboctahedra, edges with twelve equivalent MoV6Mo6 cuboctahedra, faces with eight equivalent VV6Mo6 cuboctahedra, and faces with twelve equivalent MoV6Mo6 cuboctahedra. All V–V bond lengths are 2.70 Å. All V–Mo bond lengths are 2.86 Å. Mo is bonded to six equivalent V and six equivalent Mo atoms to form MoV6Mo6 cuboctahedra that share corners with eighteen equivalent MoV6Mo6 cuboctahedra, edges with six equivalent MoV6Mo6 cuboctahedra, edges with twelve equivalent VV6Mo6 cuboctahedra, faces with eight equivalent MoV6Mo6 cuboctahedra, and faces with twelve equivalent VV6Mo6 cuboctahedra. All Mo–Mo bond lengths are 2.70 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Materials Data on VMo by Materials Project

MoV crystallizes in the orthorhombic Cmmm space group. The structure is two-dimensional and consists of two MoV sheets oriented in the (0, 1, 0) direction. V is bonded in a 4-coordinate geometry to four equivalent Mo atoms. All V–Mo bond lengths are 2.63 Å. Mo is bonded in a 4-coordinate geometry to four equivalent V atoms.

36 MATERIALS SCIENCE↗