A5091357699- High-pressure geophysics and materials
- Luminescence Properties of Advanced Materials
- X-ray Diffraction in Crystallography
- Astro and Planetary Science
- Diamond and Carbon-based Materials Research
- Thermography and Photoacoustic Techniques
- Laser-Plasma Interactions and Diagnostics
- Advanced Semiconductor Detectors and Materials
- Geological and Geochemical Analysis
- Advanced Chemical Physics Studies
- Laser-induced spectroscopy and plasma
- Calibration and Measurement Techniques
- Rare-earth and actinide compounds
- Combustion and Detonation Processes
- Solid-state spectroscopy and crystallography
- Energetic Materials and Combustion
- High-Velocity Impact and Material Behavior
- Metallurgy and Cultural Artifacts
- Crystallography and Radiation Phenomena
- Gas Dynamics and Kinetic Theory
- Atomic and Subatomic Physics Research
- Gas Sensing Nanomaterials and Sensors
- Advanced Materials Characterization Techniques
- Electronic and Structural Properties of Oxides
- Spectroscopy and Laser Applications
University of Rochester
2020-2025
Sandia National Laboratories
2022-2025
Applied Energetics (United States)
2020-2024
Energetics (United States)
2021-2024
The properties of all materials at one atmosphere pressure are controlled by the configurations their valence electrons. At extreme pressures, neighboring atoms approach so close that core-electron orbitals overlap, and theory predicts emergence unusual quantum behavior. We ramp-compress monovalent elemental sodium, a prototypical metal ambient conditions, to nearly 500 GPa (5 million atmospheres). 7-fold increase density brings interatomic distance 1.74 Å well within initial 2.03 Na
The absorption and emission of X-rays in dysprosium-doped yttrium aluminum garnet (YAG:Dy) has produced unexpected thermographic behavior, which is investigated using a combination finite temperature ab initio molecular dynamic simulations, structural characterization, electronic structure calculations X-ray characteristics. Calculated average peak spectra (XAS) from simulations between 300 600 K result intensity loss due to thermalization effects, matching experimentally measured behavior...
We present measurements on <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:msub><a:mi>Fe</a:mi><a:mn>2</a:mn></a:msub><a:msub><a:mi mathvariant="normal">O</a:mi><a:mn>3</a:mn></a:msub></a:mrow></a:math> amorphization and melt under laser-driven shock compression up to 209(10) GPa via time-resolved x-ray diffraction. At 122(3) GPa, a diffuse signal is observed indicating the presence of noncrystalline phase. Structure factors have been extracted 182(6) showing two well-defined...
Theory and experiments show that, with increasing pressure, the chemical bonds of methane rearrange, leading to formation complex polymers then dissociation. However, there is disagreement on exact conditions where these changes take place. In this study, samples were precompressed in diamond-anvil cells shock compressed pressures reaching 400 GPa, highest yet explored methane. The results reveal a qualitative change Hugoniot curve at 80–150 which interpreted as signature dissociation based...
Equation-of-state (pressure, density, temperature, internal energy) and reflectivity measurements on shock-compressed CO_{2} at above the insulating-to-conducting transition reveal new insight into chemistry of simple molecular systems in warm-dense-matter regime. samples were precompressed diamond-anvil cells to tune initial densities from 1.35 g/cm^{3} (liquid) 1.74 (solid) room temperature then shock compressed up 1 TPa 93 000 K. Variation density was leveraged infer thermodynamic...
High-pressure equation of state and isentropic sound speed data for fluid silicon to pressures 2100 GPa (21 Mbar) are reported. Principal Hugoniot measurements were performed using impedance matching techniques with \ensuremath{\alpha}-quartz as the reference. Sound speeds determined by time correlating imposed shock-velocity perturbations in both sample (Si) reference material (\ensuremath{\alpha}-quartz). A change shock velocity versus particle (${u}_{s}--{u}_{p}$) slope on principal is...
Constraining the melting behavior of magnesium oxide, a major constituent gaseous and rocky planets, is key to benchmarking their evolutionary models. Using double-shock technique, we extended MgO melt curve measurements 2 TPa; this twice pressure achieved by previous experiments on any material. A temperature plateau observed between 1218 1950 GPa in second-shock states, which attributed latent heat melting. At GPa, measured 17 600 K, 17% lower than recent theoretical predictions. The...
Iron, nickel, and their alloys are critically important materials for industrial technological applications due to unique magnetic properties, strength, thermal expansion. In this study, lasers were used compress heat ${\mathrm{Fe}}_{36}\mathrm{Ni}$ alloy (36 wt% Ni) pure nickel up the melting temperature using a combination of shock ramp compression. The structure was measured nanosecond in situ x-ray diffraction, simultaneous velocimetry measure pressure 454 GPa. A mixed...
Mechanical equation-of-state data of initially liquid and solid CO2 shock-compressed to terapascal conditions are reported. Diamond-sapphire anvil cells were used vary the initial density state samples that then further compressed with laser-driven shock waves, resulting in a set from which precise derivative quantities, including Grüneisen parameter sound speed, determined. Reshock states measured 800 GPa map same pressure-density as single using different thermodynamic paths. The...
We present in-situ x-ray diffraction and velocity measurements of Fe$_2$O$_3$ under laser shock compression at pressures between 38-116 GPa. None the phases reported by static studies were observed. Instead, we observed an isostructural phase transition from $\alpha$-Fe$_2$O$_3$ to a new $\alpha^\prime$-Fe$_2$O$_3$ pressure 50-62 The differs 11% volume drop different unit cell compressibility. further two-wave structure in profile, which can be related intermediate regime where both $\alpha$...
The warm dense matter regime is generally found in materials compressed to several times their densities on the Earth's surface at temperatures hot enough produce a conducting fluid, but not so that cohesive binding overwhelmed by temperature. This region of phase space notoriously difficult constrain with theoretical models. Iron most stable element, and relevant astrophysics, planetary physics, industry. paper here describes experiments using giant kilojoule lasers shock compress iron...
We present measurements on Fe$_2$O$_3$ amorphization and melt under laser-driven shock compression up to 209(10) GPa via time-resolved in situ x-ray diffraction. At 122(3) GPa, a diffuse signal is observed indicating the presence of non-crystalline phase. Structure factors have been extracted 182(6) showing two well-defined peaks. A rapid change intensity ratio peaks identified between 145(10) 151(10) indicative phase change. Present DFT+$U$ calculations temperatures along Hugoniot are...
Energy-dispersive x-ray diffraction of thermographic phosphors has been explored as a complementary temperature diagnostic to visible phosphor thermometry in environments where the temperature-dependent optical luminescence is occluded. Powder samples were heated from ambient 300 °C incremental steps and probed with polychromatic synchrotron x rays; scattered photons collected at fixed angle 3.9°. Crystal structure, lattice parameters, coefficients thermal expansion calculated data. Of...
View Video Presentation: https://doi.org/10.2514/6.2023-0410.vid Phosphor thermometry has become an established remote sensing technique for acquiring the temperature of surfaces and gas-phase flows. Often, phosphors are excited by a light source (typically emitting in UV region), their temperature-sensitive emission is captured. Temperature can be inferred from shifts spectra or radiative decay lifetime during relaxation. While recent work shown that several remains thermographic x-ray...
Environments in which optical luminescence is occluded (e.g. sooty flames), temperature-dependent x-ray signatures of phosphors may be utilized as a complementary diagnostic to visible phosphor thermometry. Initial temperature sensitivity experiments were performed at synchrotron several phosphors, including Terbium doped Gadolinium oxysulfide (GOS:Tb) from T = 30 C – 300 C. Energy-dispersive diffraction (EDXRD) (GOS:Tb),was found an excellent candidate for thermometry due strong, distinct...