Measurements of sound velocity and density of core materials by combination of dynamic and static methods

地球的金属地核是地球的发动机，为地球磁场的产生提供能量，并为板块构造提供动力。性能核心控制着发动机的功能。了解地核的物理和化学性质对于了解我们的星球是如何运作的至关重要。岩心的密度和速度剖面是由地震观测得来的。为了推导出有意义的铁芯成分模型，需要在同时高压和高温下精确测量铁芯的密度和速度。​研究结果将用于开发一个综合的岩心成分模型。这项研究将促进跨学科研究，并大大提高对地核及其对地球动力学过程影响的认识。这些项目将为研究生和博士后提供跨学科研究领域的培训。通过该项目开发的高压技术将广泛应用于合成先进材料，特别是超硬材料。本研究的目的是通过静态高压压缩和冲击波实验相结合的方法，获得Fe-S-Si-O体系中芯材密度和声速的最佳测量方法。提议的项目包括(1)通过激波压缩测量Fe-9wt%O合金和Fe-3wt%S-3wt%Si-3wt%O混合物的密度和声速，以及(2)通过静态和动态压缩测量Fe-9wt%Si合金的密度和声速。提出了一种新的方法来定义二元体系中成分接近估算核心成分的端元合金的密度和速度。在一套二元系统中获得的数据可以在一个小范围内插值到包括Fe， S， Si和O在内的多元素岩心组成，该插值将进一步与新的多元素组成实验测量（Fe-3wt%S-3wt%Si-3wt%O）进行测试，最终缩小与地球物理观测一致的岩心组成范围。

Earth's metallic core is the engine of the planet, providing the energy to generate its magnetic field and the driving force for plate tectonics. The properties the core control the function of the engine. It is fundamentally important to understanding the physical and chemical properties of the core in order to understand how our planet works. The density and velocity profiles of the core have been derived from seismic observations. Accurate measurements of density and velocity of core iron-alloys under simultaneous high pressure and temperature are required to derive meaningful composition models of the core. Dr. Yingwei Fei investigates the density and sound velocity of core materials over a wide pressure-temperature range by combining static and dynamic experimental methods. The results will be used to develop a comprehensive core composition model. The study will promote interdisciplinary research and significantly advance knowledge of the Earth's core and its influence on the dynamics processes of the planet. The projects will provide training in interdisciplinary research areas for graduate students and postdoctoral associates. The high-pressure techniques developed through the project will have general applications for synthesis of advanced materials, particularly super-hard materials.The objective of the research is to obtain the best measurements of the density and sound velocity of core materials in the Fe-S-Si-O system by combination of static high-pressure compression and shockwave experiment. The proposed projects include (1) measurements of density and sound velocity of a Fe-9wt%O alloy and Fe-3wt%S-3wt%Si-3wt%O mixture by shock compression, and (2) additional measurements of density and sound velocity of an Fe-9wt%Si alloy by static and dynamic compressions. The proposal outlines a new approach to define the density and velocity of the end-member alloys whose compositions are close to the estimated core composition in a binary system. The data obtained in a suite of binary systems can be interpolated in a small range for a multi-element core composition that includes Fe, S, Si, and O. The interpolation will be further tested against new experimental measurements on a multi-element composition (Fe-3wt%S-3wt%Si-3wt%O), and ultimately narrow down the core composition range that is consistent with the geophysical observations.