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

地球的金属核心是地球的引擎，提供产生磁场的能量和板块构造的驱动力。发动机的核心性能控制着发动机的性能。了解地核的物理和化学性质对于理解我们的星球是如何运行的至关重要。从地震观测中得到了岩心的密度和速度剖面。为了得到有意义的铁芯成分模型，需要准确测量高温高压下铁芯合金的密度和速度。费英伟博士采用静态和动态相结合的实验方法，在较宽的压力-温度范围内研究了堆芯材料的密度和声速。结果将被用来开发一个全面的核心成分模型。这项研究将促进跨学科研究，并大大促进对地核及其对地球动力学过程的影响的了解。这些项目将为研究生和博士后助理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在合成先进材料，特别是超硬材料方面具有广泛的应用。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，获得对Fe-S-Si-O系核心材料密度和声速的最佳测量结果。建议的项目包括(1)用冲击压缩方法测量Fe-9wt%O合金和Fe-3wt%S-3wt%Si-3wt%O混合物的密度和声速；(2)用静态和动态压缩方法测量Fe-9wt%Si合金的密度和声速。该提案概述了一种新的方法来确定端元合金的密度和速度，这些端元合金的组成接近于二元系中估计的核心组成。在一套二元系中获得的数据可以在小范围内对包括Fe、S、Si和O的多元素岩心成分进行内插。该内插将与新的多元素成分(Fe-3wt%S-3wt%Si-3wt%O)的实验测量结果进行进一步的检验，最终缩小与地球物理观测相一致的岩心成分范围。

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.