Search results for "phase stability"
showing 7 items of 7 documents
First-principles studies of Ni–Ta intermetallic compounds
2012
National Natural Science Foundation of China [51131002, 50772018]; Program for New Century Excellent Talents in Universities of China [NCET-07-0139]; NSERC; CRC
Influences of Ortho‐Fluoroazobenzenes on Liquid Crystalline Phase Stability and 2D (Planar) Actuation Properties of Liquid Crystalline Elastomers
2019
Structural Stability of Hafnia-Based Materials at Ultra-High Temperature
2018
This study assesses the structural stability at ultra-high temperature of the following selected compositions: 6.5 and 14 mol. % of RE2O3 (RE = Dy, Y, Er, Yb, and Lu) doped HfO2. Under thermal cycling and thermal shock, the structural stability was evaluated at 2400°C with water vapor flux using a specific test bench with a 3 kW CO2 laser. The cubic phase stability, which is theoretically important in the broad temperature range from 25 to 2800°C, was determined by a quantitative analysis of the X-ray diffractograms. Fully and partially stabilized HfO2, obtained respectively with 14 mol. % and 6.5 mol. % of dopants, showed different behaviors to thermal damage. Thermal expansion was measure…
Irreversibility of the pressure-induced phase transition of quartz and the relation between three hypothetical post-quartz phases
2004
Our atomistic computer simulations mainly based on classical force fields suggest that the pressure-induced transition from $\ensuremath{\alpha}$ quartz to quartz II at $21\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ is irreversible. While quartz II is ferroelastic in principle, the transition itself is coelastic, as the shape of the newly formed crystal is determined by the handedness of $\ensuremath{\alpha}$-quartz. Upon releasing the pressure, our model quartz II remains stable down to $5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, where it undergoes an isosymmetric transformation into a less dense polymorph. If the classical force field model of quartz II is compressed quickly to $50\phantom{\…
Erratum to “Cerium effect on the phase structure, phase stability and redox properties of Ce-doped strontium ferrates”
2008
Phase Stability of Natural Ni0.75Mg0.22Ca0.03CO3 Gaspeite Mineral at High Pressure and Temperature
2020
[EN] Divalent metal carbonates play an important role in Earth's carbon cycle, but the effect of chemical substitution is still poorly known. In this work, we have studied the structural and vibrational properties of natural mineral gaspeite (Ni0.75Mg0.22Ca0.03CO3) under high pressure and temperature using in situ synchrotron X-ray diffraction and Raman spectroscopy in diamond-anvil cells. These experiments have been complemented by ab initio simulations. Synchrotron high-pressure XRD measurements at room temperature using He as the pressure transmitting medium have shown that the calcite-type structure is stable up to 23.3 GPa. A bulk modulus at zero pressure of B-0 = 105(2) GPa with B-0' …
On the high-pressure phase stability and elastic properties ofβ-titanium alloys
2017
We have studied the compressibility and stability of different β-titanium alloys at high pressure, including binary Ti–Mo, Ti–24Nb–4Zr–8Sn (Ti2448) and Ti–36Nb–2Ta–0.3O (gum metal). We observed stability of the β phase in these alloys to 40 GPa, well into the ω phase region in the P–T diagram of pure titanium. Gum metal was pressurised above 70 GPa and forms a phase with a crystal structure similar to the η phase of pure Ti. The bulk moduli determined for the different alloys range from 97 ± 3 GPa (Ti2448) to 124 ± 6 GPa (Ti–16.8Mo–0.13O).