Physics and Chemistry of Planetary Materials at Extreme Conditions

我的研究目的是提高我们了解地球和其他行星的深部内部动力学和演化的能力。地球和行星内部的动态和演化将影响地球和其他行星的最外层特征。然而，地球和行星的内部是无法接触到的，也不能直接调查。另一种方法是在类似于地球和行星内部的模拟环境中研究地球和行星材料。此外，材料在环境条件(1大气压和25摄氏度)下的行为与它们在更深处的表现不同。因此，只有在与一定深度对应的压力和温度条件下收集的数据才能有效地模拟地球和行星内部的结构和动力学。因此，研究地球和行星物质在与其深部相对应的压力和温度条件下的变化，为理解地球和行星内部的动力学和演化提供了有希望的途径。 我的研究项目使用高压仪器，即钻石顶压室(DAC，能够产生从1到3,000,000大气压的压力)，以及电阻和激光加热方法(能够将样品加热到3000-4000 K)，来研究极端压力和温度条件下的行星材料。广泛的压力和温度范围(1-300万大气压和300-4000 K)使我们能够复制地球和行星内部的条件。此外，利用自制的显微拉曼系统和同步辐射红外光谱，还研究了相关材料的光谱性质。 在这个方案中，我们合成了重要的深部地幔相(例如富铝和富铁的钙钛矿和后钙钛矿、含碳和含氢的硅酸盐、尖晶石、氧化物和铁合金)，并用同步辐射x射线衍射、x射线光谱、拉曼光谱和红外光谱对它们进行表征，以了解它们的结构和物理性质(如密度、体积、弹性、强度、应力)。利用电子探针(EPMA)、扫描电子显微镜(SEM)和分析透射电子显微镜(ATEM)对合成的样品进行分析，以了解样品中元素的分配和分布、铁合金的熔化准则以及纳米相的晶体结构。我们的目标是(1)了解在D“层内发现的地震异常(如超低速)的原因和机制，(2)建立可用于模拟地球内部动力学的混合地幔相的强度模型，(3)评估高温高压条件下铬尖晶石的高压形态及其与受冲击陨石的联系，以及(4)评估地球内部通过含碳和含氢的深部地幔相的氢和碳的收支。 拟议的项目将促进矿物物理、地球动力学、行星科学和材料科学领域的跨学科工作和教育。此外，HQP还将接受全面的高压研究培训。他们将在UWO使用强大的分析工具，并在不同地点使用最先进的同步加速器设施来进行他们的项目。特别是，HQP将从他们的同步加速器之旅中受益匪浅，因为他们将有极好的机会将自己暴露在社区的不同领域。这将对他们未来的职业生涯有很大的帮助。

The objective of my research is to improve our abilities to understand the deep interior dynamics and evolution of Earth and other planets. The dynamics and evolution of Earth’s and planetary interiors will influence the outermost features of the Earth and other planets. However, Earth’s and planetary interiors are inaccessible and cannot be directly investigated. Alternative approaches are to study Earth and planetary materials at simulated environments that are similar to Earth and planetary interiors. In addition, behavior of materials at ambient conditions (1 atm and 25 C) is different from what they exhibit at greater depths. Therefore, only those data collected at pressure and temperature conditions corresponding to the certain depths are valid for modeling the structure and dynamics of the Earth’s and planetary interiors. Therefore, study of Earth and planetary materials at pressure and temperature conditions corresponding to their deep interiors provide promising approach to understand the dynamics and evolution of Earth’s and planetary interiors. My research program uses high pressure apparatus, a diamond-anvil cell (DAC, able to generate pressure from 1 to 3,000,000 atm) together with resistive and laser heating methods (able to heat the sample to 3000 - 4000 K), to study planetary materials under extreme pressure and temperature conditions. The extensive pressure and temperature ranges (1 - 3,000,000 atm and 300 - 4000 K) allow us to replicate the conditions found within the Earth and planetary interiors. Moreover, using a custom-built micro-Raman system and synchrotron infrared spectroscopy, the spectroscopic properties of relevant materials are also examined. In this proposal, we synthesize the important deep mantle phases (e.g. aluminum and iron-rich perovskite and post-perovskite, carbon- and hydrogen-bearing silicates, spinels, oxides and iron alloys) and characterize them using synchrotron x-ray diffraction, x-ray spectroscopy, Raman and infrared to understand their structures and physical properties (e.g. density, volume, elasticity, strength, stress). The synthesized samples when quenched to ambient conditions will be examined by electron probe microanalysis (EPMA), scanning electron microscopy (SEM) and analytical transmitting electron microscopy (ATEM) for understanding the partitioning of the elements and element distributions within the samples, the melting criteria of the iron alloy, and the crystal structures of the nano-scale phases. Our goals are (1) to understand the causes and mechanism of seismic anomalies (e.g. ultralow velocity) found within the D” layer, (2) to build a strength model of mixed mantle phases that can be applied to modeling the dynamics of the Earth’s interior, (3) to evaluate the high pressure polymorphs of chromium spinel at high pressure-temperature conditions as well as its connection to the shocked meteorites, and (4) to evaluate the budgets of the hydrogen and carbon inside the Earth via the carbon- and hydrogen-bearing deep mantle phases. The proposed projects will promote interdisciplinary work and education in the fields of mineral physics, geodynamics, planetary science and material science. In addition, HQP will receive well-rounded training in the high pressure research. They will use powerful analytical tools at UWO and state-of-the-art synchrotron facilities at different locations for their projects. Especially, HQP will greatly benefit from their participations in the synchrotron trips as they will have excellent opportunities to expose themselves to different fields of communities. This will be of great help for their future careers.