27 research outputs found
Recommended from our members
Pressure-temperature stability studies of FeOOH using x-ray diffraction
The Mie-Gruneisen formalism is used to fit a Birch-Murnaghan equation of state to high-temperature (T), high-pressure (P) X-ray diffraction unit-cell volume (V) measurements on synthetic goethite (alpha-FeOOH) to combined conditions of T = 23-250o C and P = 0-29.4 GPa. We find the zero-pressure thermal expansion coefficient of goethite to be alpha0 = 2.3 (+-0.6) x 10-5 K-1 over this temperature range. Our data yield zero-pressure compressional parameters: V0 = 138.75 (+- 0.02) Angstrom3, bulk modulus K0 = 140.3 (+- 3.7) GPa, pressure derivative K0' = 4.6 (+- 0.4), Gruneisen parameter gamma0 = 0.91 (+- 0.07), and Debye temperature Theta0 = 740 (+- 5) K. We identify decomposition conditions for 2alpha-FeOOH --> alpha-Fe2O3 + H2O at 1 - 8 GPa and 100-400oC, and the polymorphic transition from alpha-FeOOH (Pbnm) to epsilon-FeOOH (P21mn). The non-quenchable, high-pressure epsilon-FeOOH phase P-V data are fitted to a second-order (Birch) equation of state yielding, K0 = 158 (+- 5) GPa and V0 = 66.3 (+- 0.5) Angstrom3
Phase transition kinetics revealed in laser-heated dynamic diamond anvil cells
We report on a novel approach to dynamic compression of materials that
bridges the gap between previous static- and dynamic- compression techniques,
allowing to explore a wide range of pathways in the pressure-temperature space.
By combining a dynamic-diamond anvil cell setup with double-sided laser-heating
and in situ X-ray diffraction, we are able to perform dynamic compression at
high temperature and characterize structural transitions with unprecedented
time resolution. Using this method, we investigate the phase
transition of iron under dynamic compression for the first time, reaching
compression rates of hundreds of GPa/s and temperatures of 2000 K. Our results
demonstrate a distinct response of the and
transitions to the high compression rates achieved. These findings open up new
avenues to study tailored dynamic compression pathways in the
pressure-temperature space and highlight the potential of this platform to
capture kinetic effects in a diamond anvil cell.Comment: Reworked the text and figures to be more in line with the format of
PR
Recommended from our members
Phase transition kinetics revealed by <i>in situ</i> x-ray diffraction in laser-heated dynamic diamond anvil cells
We report successful coupling of dynamic loading in a diamond anvil cell and stable laser heating, which enables compression rates up to 500 GPa/s along high-temperature isotherms. Dynamic loading in a diamond-anvil cell allows exploration of a wider range of pathways in the pressure-temperature space compared to conventional dynamic compression techniques. By in situ x-ray diffraction, we are able to characterize and monitor the structural transitions with the appropriate time resolution i.e., millisecond timescales. Using this method, we investigate the γ−ε phase transition of iron under dynamic compression, reaching compression rates of hundreds of GPa/s and temperatures of 2000 K. Our results demonstrate a distinct response of the γ−ε and α− ε transitions to the high compression rates achieved, possibly due to the different transition mechanisms. These findings open up new avenues to study tailored dynamic compression pathways in the pressure-temperature space and highlight the potential of this platform to capture kinetic effects (over ms time scales) in a diamond anvil cell
Observation of Fundamental Mechanisms in Compression-Induced Phase Transformations Using Ultrafast X-ray Diffraction
As theoretically hypothesized for several decades in group IV transition metals, we have discovered a dynamically stabilized body-centered cubic (bcc) intermediate state in Zr under uniaxial loading at sub-nanosecond timescales. Under ultrafast shock wave compression, rather than the transformation from alpha-Zr to the more disordered hex-3 equilibrium omega-Zr phase, in its place we find the formation of a previously unobserved nonequilibrium bcc metastable intermediate. We probe the compression-induced phase transition pathway in zirconium using time-resolved sub-picosecond x-ray diffraction analysis at the Linac Coherent Light Source. We also present molecular dynamics simulations using a potential derived from first-principles methods which independently predict this intermediate phase under ultrafast shock conditions. In contrast with experiments on longer timescale (> 10 ns) where the phase diagram alone is an adequate predictor of the crystalline structure of a material, our recent study highlights the importance of metastability and time dependence in the kinetics of phase transformations
Ultrafast Radiographic Imaging and Tracking: An overview of instruments, methods, data, and applications
Ultrafast radiographic imaging and tracking (U-RadIT) use state-of-the-art
ionizing particle and light sources to experimentally study sub-nanosecond
dynamic processes in physics, chemistry, biology, geology, materials science
and other fields. These processes, fundamental to nuclear fusion energy,
advanced manufacturing, green transportation and others, often involve one mole
or more atoms, and thus are challenging to compute by using the first
principles of quantum physics or other forward models. One of the central
problems in U-RadIT is to optimize information yield through, e.g.
high-luminosity X-ray and particle sources, efficient imaging and tracking
detectors, novel methods to collect data, and large-bandwidth online and
offline data processing, regulated by the underlying physics, statistics, and
computing power. We review and highlight recent progress in: a.) Detectors; b.)
U-RadIT modalities; c.) Data and algorithms; and d.) Applications.
Hardware-centric approaches to U-RadIT optimization are constrained by detector
material properties, low signal-to-noise ratio, high cost and long development
cycles of critical hardware components such as ASICs. Interpretation of
experimental data, including comparisons with forward models, is frequently
hindered by sparse measurements, model and measurement uncertainties, and
noise. Alternatively, U-RadIT makes increasing use of data science and machine
learning algorithms, including experimental implementations of compressed
sensing. Machine learning and artificial intelligence approaches, refined by
physics and materials information, may also contribute significantly to data
interpretation, uncertainty quantification and U-RadIT optimization.Comment: 51 pages, 31 figures; Overview of ultrafast radiographic imaging and
tracking as a part of ULITIMA 2023 conference, Mar. 13-16,2023, Menlo Park,
CA, US
Pressure-temperature stability studies of FeOOH using x-ray diffraction
The Mie-Gruneisen formalism is used to fit a Birch-Murnaghan equation of state to high-temperature (T), high-pressure (P) X-ray diffraction unit-cell volume (V) measurements on synthetic goethite (alpha-FeOOH) to combined conditions of T = 23-250o C and P = 0-29.4 GPa. We find the zero-pressure thermal expansion coefficient of goethite to be alpha0 = 2.3 (+-0.6) x 10-5 K-1 over this temperature range. Our data yield zero-pressure compressional parameters: V0 = 138.75 (+- 0.02) Angstrom3, bulk modulus K0 = 140.3 (+- 3.7) GPa, pressure derivative K0' = 4.6 (+- 0.4), Gruneisen parameter gamma0 = 0.91 (+- 0.07), and Debye temperature Theta0 = 740 (+- 5) K. We identify decomposition conditions for 2alpha-FeOOH --> alpha-Fe2O3 + H2O at 1 - 8 GPa and 100-400oC, and the polymorphic transition from alpha-FeOOH (Pbnm) to epsilon-FeOOH (P21mn). The non-quenchable, high-pressure epsilon-FeOOH phase P-V data are fitted to a second-order (Birch) equation of state yielding, K0 = 158 (+- 5) GPa and V0 = 66.3 (+- 0.5) Angstrom3
High Pressure Brillouin Spectroscopy and X-ray Diffraction of Cerium Dioxide
Simultaneous high-pressure Brillouin spectroscopy and powder X-ray diffraction of cerium dioxide powders are presented at room temperature to a pressure of 45 GPa. Micro- and nanocrystalline powders are studied and the density, acoustic velocities and elastic moduli determined. In contrast to recent reports of anomalous compressibility and strength in nanocrystalline cerium dioxide, the acoustic velocities are found to be insensitive to grain size and enhanced strength is not observed in nanocrystalline CeO2. Discrepancies in the bulk moduli derived from Brillouin and powder X-ray diffraction studies suggest that the properties of CeO2 are sensitive to the hydrostaticity of its environment. Our Brillouin data give the shear modulus, G0 = 63 (3) GPa, and adiabatic bulk modulus, KS0 = 142 (9) GPa, which is considerably lower than the isothermal bulk modulus, KT0∼ 230 GPa, determined by high-pressure X-ray diffraction experiments
The Resistive-heating characterization of laser heating system and LaB₆ characterization of X-ray diffraction of beamline 12.2.2 at advanced light source
X-ray diffraction from LaB₆ standards document a precision of 478 ppm in lattice-parameter determinations for beamline 12.2.2 at Lawrence Berkeley National Laboratory′s Advanced Light Source, a facility for characterizing materials at high pressures and temperatures using laser- and resistance-heated diamond cells. Melting of Ni, Mo, Pt and W, resistively heated at 1 atm pressure in Ar, provides a validation of the beamline spectroradiometric system that is used to determine sample temperatures. The known melting temperatures, which range from 1665 to 3860 K for these metals, are all reproduced to within ±80 K.4 page(s