X-ray Scattering Experiments on Melting and Equations of State of Candidate Compositions of Earth's Core

地核候选成分熔化的X射线散射实验和状态方程

• 批准号: 1427123
• 负责人: Andrew Campbell
• 金额: $ 38万
• 依托单位: University of Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-15 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1427123&HistoricalAwards=false
• 关键词: ray; Scattering; Experiments; Melting; Equations

The results expected from this project will improve our understanding of the temperature and chemical composition of Earth's core. Earth's core is known to be an iron-rich alloy, mostly molten but with a solid inner core. In addition to iron it contains approximately 5% nickel and approximately 10% of a lighter element, whose identity is uncertain but is likely a combination of oxygen, sulfur, silicon, and/or carbon. A more precise understanding of the composition of Earth's core is important to constrain our understanding of the chemical and physical processes that led to the formation of our planet. Furthermore, the temperature structure in the deep Earth is poorly known, and can be better constrained with more accurate measurements of the melting temperatures of candidate core compositions under the relevant pressure, temperature conditions. Accordingly, the aims of this project are to measure the melting temperatures and densities of iron alloys under the extreme pressure, temperature conditions that exist in Earth's core. The experimental results will be applied to place more accurate bounds on the temperatures and composition of Earth's core.The project has several specific experimental research goals. These include (1) Establishing melting temperatures in the ternary systems Fe-O-S, Fe-Si-S, and Fe-Si-O up to pressures appropriate in Earth's outer core; (2) Analyzing X-ray diffuse scattering measured from melts in these ternary systems to place constraints on their liquid densities; (3) Extending the equations of state of Fe3C and Fe3S to higher pressure and temperature conditions, to permit more precise thermodynamic treatment of S,C-bearing Fe-alloys, and more precise density-based constraints on the maximum content of S and C allowable in Earth's core. To achieve these goals the PI will perform synchrotron-based X-ray scattering experiments on samples that are pressurized and laser heated in a diamond anvil cell, reaching the extreme pressure, temperature conditions (in excess of 140 GPa and 4000 K) that exist in Earth's core. In parallel with these investigations, he will continue to develop experimental methods to improve the ability of his lab and others to investigate the material properties of Earth's core. These research projects will also serve as a platform on which the PI's training of graduate and undergraduate students will be trained in laboratory research and scientific pursuit.

该项目的预期结果将增进我们对地核温度和化学成分的了解。众所周知，地核是一种富含铁的合金，大部分处于熔融状态，但具有坚固的内核。除铁外，它还含有约 5% 的镍和约 10% 的较轻元素​​，其成分不确定，但可能是氧、硫、硅和/或碳的组合。更精确地了解地核的组成对于限制我们对导致地球形成的化学和物理过程的理解非常重要。此外，地球深处的温度结构知之甚少，并且可以通过在相关压力、温度条件下更准确地测量候选核心成分的熔化温度来更好地约束。因此，该项目的目的是测量铁合金在地核存在的极端压力、温度条件下的熔化温度和密度。实验结果将用于对地核的温度和成分进行更准确的限制。该项目有几个具体的实验研究目标。这些包括（1）建立三元体系 Fe-O-S、Fe-Si-S 和 Fe-Si-O 的熔化温度，直至达到地球外核适当的压力； (2) 分析从这些三元体系中的熔体测量的 X 射线漫散射，以对其液体密度施加限制； (3) 将Fe3C和Fe3S的状态方程扩展到更高的压力和温度条件，以允许对含S、C的铁合金进行更精确的热力学处理，并对地核中允许的S和C的最大含量进行更精确的基于密度的限制。为了实现这些目标，PI 将对在金刚石砧室中加压和激光加热的样品进行基于同步加速器的 X 射线散射实验，以达到地核中存在的极端压力和温度条件（超过 140 GPa 和 4000 K）。在进行这些研究的同时，他将继续开发实验方法，以提高他的实验室和其他实验室研究地核材料特性的能力。这些研究项目也将作为PI对研究生和本科生进行实验室研究和科学追求训练的平台。