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Equation of State and structural phase transition of zirconium carbide at high pressure

wallpapers News 2021-12-16
ZrC sample with 99.5% purity. At room temperature and pressure, ZrC has a face-centered cubic structure and space group Fm3m. In a cell, zirconium atom (Zr) occupies a position of (0,0,0) and carbon atom (C) occupies a position of (0.5, 0.5, 0.5).The sample morphology was analyzed using DSM-7500F scanning electron microscope (SEM) produced by Japan Electronics Co., LTD. The resolution is 1.0 nm (15 kV). SEM of ZrC samples under atmospheric pressure is shown in Figure 2. The initial average cluster size of ZrC is about 4 μm. The structure and properties of ZrC clusters are closely related to the cluster size, which makes them have different physical and chemical properties from conventional materials. According to the average cluster size analysis of ZrC, it is considered a bulk material.
X-ray diffraction experiments of the ZrC copper target have been carried out with an X-ray diffractometer. The 2θ Angle range is -110° ~ 162°, the minimum controllable step size is 0.000 1°, the resolution is 0.028°, and the wavelength (λ) is 0.154 06 nm. The crystal plane indices of ZrC are (111), (200), (220), (311), and (222), respectively. ZrC is a pure phase and its diffraction peak is sharp, indicating that its crystallization is good.Thus, the cell parameter (a) is 0.469 6 nm (0.000 1), which is very close to the result reported in reference [17] (a=0.468 9 nm).A modified MAO-Bell diamond with a diameter of 300 μm was used to conduct high-pressure X-ray diffraction experiments on the anvil. The T301 sealing pad was repressed to about 35 μm, and a sample hole with a diameter of 120 μm was drilled in the center of the indentation by laser.Silicone oil was used as pressure transfer medium and 10 μm ruby was used as a pressure transfer material
High-pressure diffraction experiments of in-situ synchrotron radiation were carried out on beam 4W2 of the Beijing Synchrotron Radiation Facility (BSRF). Pilatus detector is used to receive diffraction signals. CeO2 standard is used to calibrate the distance between the sample and the detector and the tilt angle of the detector. The exposure time of each diffraction image is 5-8 min
zirconium carbide experience conclusion
The equation of state and structural phase transformation of ZrC in a quasi-hydrostatic high-pressure environment with diamond on the anvil are studied. The results show that: The discontinuous change of VZrC with P occurs at 10.3 GPa and ends at 13.7 GPa. This anomaly reveals the existence of phase transition. Since the electronic structure and density of electronic states of ZrC do not change at high pressure, it is considered that the phase transition is not an electronic structural phase transition, but a topological phase transition. Meanwhile, the b1-phase bulk elastic modulus of ZrC is 158.6 (8.6) GPa by synchrotron radiation X-ray diffraction experiment, and the bulk elastic modulus of ZrC after topological phase transformation is 233.8 (8.8) GPa.

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