A5012317493- Astro and Planetary Science
- Intermetallics and Advanced Alloy Properties
- High-pressure geophysics and materials
- Microstructure and mechanical properties
- Planetary Science and Exploration
- Advanced ceramic materials synthesis
- Semiconductor materials and interfaces
- Advancements in Solid Oxide Fuel Cells
- Advanced Chemical Physics Studies
- Thermal properties of materials
- Superconductivity in MgB2 and Alloys
- High Temperature Alloys and Creep
- Geological and Geochemical Analysis
- Advanced materials and composites
- Solidification and crystal growth phenomena
- Fullerene Chemistry and Applications
- Hydrogen Storage and Materials
- Metallurgical and Alloy Processes
- Astrophysics and Star Formation Studies
- Thermal and Kinetic Analysis
- Stellar, planetary, and galactic studies
- Thermal Expansion and Ionic Conductivity
- Graphene research and applications
- Boron and Carbon Nanomaterials Research
- Structural Integrity and Reliability Analysis
University of Arizona
2013-2024
Rogers (United States)
2021-2024
Planetary Science Institute
2022
Pennsylvania State University
2010-2014
University of Illinois Urbana-Champaign
2013-2014
Max Planck Society
2006
A first-principles approach to calculating the elastic stiffness coefficients at finite temperatures was proposed. It is based on assumption that temperature dependence of mainly results from volume change as a function temperature; it combines calculations constants 0 K and phonon theory thermal expansion. Its applications Al, Cu, Ni, Mo, Ta, NiAl, Ni₃Al up their respective melting points show excellent agreement between predicted values existing experimental measurements.
Stress introduces anisotropy in the transport coefficients materials, affecting diffusion. Using first-principles quantum-mechanical methods for activation barriers of atomic jumps, combined with extended self-consistent mean-field theory to compute strain-reduced symmetry, we predict significant stress-induced Si impurity diffusion nickel. This causes complex spatial- and temperature-dependent fluxes; as an example, heterogenous strain field a dislocation creates unusual flow patterns that...
Molten mixtures of network-forming covalently bonded ZnCl2 and network-modifying ionically NaCl KCl salts are investigated as high-temperature heat transfer fluids for concentrating solar power plants. Specifically, using molecular dynamics simulations, the interplay between extent network structure, composition, transport properties (viscosity, thermal conductivity, diffusion) ZnCl2–NaCl–KCl molten is characterized. The Stokes-Einstein/Eyring relationship found to break down in these...
We perform a first-principles study of the effect strain on migration Si atoms in Ni. For that purpose, barriers are computed using nudged elastic band method and attempt frequencies direct force method. Good agreement is found with tracer diffusion experiments. used dipole model to calculate effects by performing calculations unstrained cells, therefore reducing significantly computing time. validate this approach comparing results calculated strained cells obtain an excellent up 1%....
The anisotropy of antiphase boundary (APB) energies in ordered L12–Ni3Al is studied, owing to its importance understanding the anomalous flow behavior this intermetallic compound. We report first-principle calculations for two types APBs compound: (001) and (111). magnetic perturbations associated with these are calculated as a function supercell size ensure that their periodic images isolated both magnetically elastically. perturbation (111) APB wider than APB. fully relaxed, spin-polarized...
Thermodynamics of defects in the (LaxCa1-x)FeO3-δ perovskite is modeled by means CALPHAD approach. In this phase, A-sites are occupied La+3 and Ca+2, Fe B-site known to exist +2, +3, +4 oxidation states depending on oxygen vacancy concentration. Therefore, ionic sublattice model: (La+3, Ca+2)(Fe+2, Fe+3, Fe+4)(O−2, Va)3 used describe model parameters evaluated from experimental nonstoichiometry phase equilibria data. With Fe+2 Fe+4 treated as major species B-site, calculated diagrams good...
Ab initio molecular dynamics simulations have been used to predict diffusion coefficients in Al–Si binary melts as a function of composition and temperature. The self-diffusion Al Si are obtained from the mean-squared displacements velocity autocorrelation functions employing two different exchange correlation functionals. Si-concentrations include 0, 7, 12 15 at% with temperature ranging 900–1800 K. In these melts, aluminum silicon exhibit nearly identical coefficients. first nearest...
A multiscale computational framework combining the first-principles calculations and CALPHAD approach with phase-field method is presented to simulate microstructure evolution in multicomponent steel alloys. We demonstrate potential of by predicting microstructural elastically periodic arrays Mo-V binary sub-system. The utilizes using special quasi-random structures. Hitherto unavailable thermodynamic material properties alloy are obtained employing fed into model predict at different...
A phase diagram‐assisted powder processing approach is shown to produce low‐oxygen (0.06 wt%O) ZrB 2 ceramics using minimal B 4 C additions (0.25 wt%) and spark plasma sintering. Scanning electron microscopy scanning transmission with elemental spectroscopy are used identify “trash collector” oxides. These oxides composed of manufacturer metal impurities that form discreet oxide particles due the absence standard Zr–B found in high oxygen samples. preliminary Zr–B–C–O quaternary...
Abstract Carbon was used to reduce oxides in spark plasma sintered ZrB 2 ultra‐high temperature ceramics. A thermodynamic model evaluate the reducing reactions remove B O 3 and ZrO from powder. Powder oxygen content measured carbon additions of 0.5 0.75 wt% were used. C–ZrO pseudo binary diagram, –B –C ternaries, Zr–C–O potential phase diagrams generated show how can be related an open system experiment tube furnace. Scanning transmission electron microscopy identified impurity phases...
Abstract Calcium-aluminum-rich inclusions (CAIs) in chondritic meteorites are composed of refractory minerals thought to be the first solids have formed solar nebula. Among them, hibonite, nominally CaAl12O19, holds particular interest because it can incorporate significant amounts Ti into its crystal structure both Ti3+ and Ti4+ oxidation states. The relative these cations that incorporated reflect redox conditions under which grain or last equilibrated their measurement provide insight...
AbstractThe mechanical response of symmetric tilt grain boundaries (GBs) in silicon bicrystals under shear loading are characterized using molecular dynamics simulations. It is seen that shear, high-angle GBs namely Σ5 and Σ13 having a rotation axis [0 0 1] demonstrate coupled GB motion, such the displacement grains parallel to interface accompanied by normal motion. An atomic-scale characterization revealed concerted rotations tetrahedra within primary mechanisms leading Interestingly, so...
Abstract Thermodynamic modeling of Zr–B–C–O quaternary system is conducted within the CALPHAD framework by employing data obtained from first‐principle calculations and literature. The lower order binary B–O assessed in this work estimating thermodynamic properties stable solid phases B 2 O 3 6 gas liquid phases. First‐principle calculations, conjunction with special quasirandom structure were used to predict enthalpies mixing for ternary solid‐solution phase FCC‐Zr(C, O). calculated results...