세미나
2024년 3월 29일(금) 세미나 안내 | ||
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제목: Shock Wave Voyages: Exploring from Super-Earth Cores to Earth's Crust
연사: 김동훈 교수 (고려대학교 지구환경과학과)
일시: 2024년 3월 29일 금요일 16:30 장소: 과학관 B102호 Abstract: Dynamic compression is a powerful means of studying the physical and chemical properties of materials under extreme conditions on time scales between nano- and micro-seconds. Dynamic compression allows for the study of a broad range of time-dependent condensed matter phenomena, such as structural phase transformations, inelastic deformation, and fracture. Furthermore, dynamic compression has been used to constrain the equation of state of materials to conditions that traditional static-compression techniques cannot reach. Recently, newly developed ramp-loading techniques using high-powered lasers and pulsed-power systems provide access to new regimes of pressure-temperature space. Ramp compression combined with in situ X-ray diffraction allows observation of the structural behavior, phase transitions, and kinetics of planetary materials at extreme conditions.
This talk will summarize our recent studies at the Omega laser and Z facility. Specifically, we
performed laser-driven ramp-compression experiments with in situ X-ray diffraction to explore
the structural behavior and phase transitions in silicon carbide, SiC, and germanium dioxide,
GeO2. For SiC, the rocksalt (B1) phase was observed from 140 - 1500 GPa. Using the equation
of state of B1 SiC measured here I determine mass-radius curves for carbon-rich planets which
are found to have a lower density (~10%) than Earth-like planets. For GeO2 which serves as an
analog for SiO2, we have examined its crystal structure up to 882 GPa. X- ray diffraction results
show that GeO2 adopts the HP-PdF2-type structure under ramp loading from 154 GPa to 440
GPa. Above 440 GPa, we observe evidence for a post-HP-PdF2 phase in GeO2. The best
candidate for this new phase is the cotunnite-type structure. These results offer a test of
theoretical calculations as well as insights into the possible high-pressure behavior of SiO2. At
the Z-facility, shock-compression experiments were performed on iron-bearing bridgmanite
(Mg0.92,Fe0.08)SiO3 in the range of ~450 GPa to constrain its melting point on the Hugoniot. Our
Hugoniot sound velocity measurements will allow for interpreting the melting point of Mg-rich
silicates. These experiments will offer insights into impact processes relevant to planetary
formation and evolution. |
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이전글 | 2024년 3월 29일(금) 세미나 안내 | |
다음글 | 2024년 4월 2일(화) 세미나 안내 |