Effect of Hydrogen on the Properties of Fe alloys in the Earth's Core

氢对地核铁合金性能的影响

• 批准号: 1921298
• 负责人: Sang-Heon Shim
• 金额: $ 29.9万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-08-01 至 2022-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1921298&HistoricalAwards=false
• 关键词: Effect; Hydrogen; Properties; Fe; alloys

For more than half a century, scientists have known that the Earth's core - the 3500-km large ball of mostly iron at the center of the planet - has a density 5-10% lower than that of pure iron. This is because the core contains light elements, such as Si, O, S, C, and H. While the core cools down forming the solid inner core, light elements segregate preferentially in the liquid outer core. This process powers in part the magnetic field which shields us from the solar wind. Furthermore, knowing the composition of the core is critical to constrain its formation and evolution. Light elements in metallic iron have, thus, been extensively studied at the extreme pressure and temperature conditions of the deep Earth. However, because of experimental limitations, the effect of hydrogen on core materials is still largely unknown. Here, the researchers investigate how hydrogen affect the properties of the core. Taking advantage of recent technical developments, they study the iron-hydrogen system at the high pressure and temperature of Earth's interior. The experiments, carried out at national synchrotron facilities, quantify the melting temperature and density of iron-rich alloys. Theoretical calculations at the atomic level guide the experimental approach and the data analysis. The results improve current models of the core with implications for the understanding of its formation, evolution and present-day magnetic field, with numerous ramifications in Earth Sciences. This two-year project provides support for an early-career female scientist and a graduate student, and training opportunities for undergraduate summer interns in state-of-the art Mineral Physics. It also increases the public awareness of the important role of hydrogen in the Earth through presentations during open-house events at Arizona State University.Here, the team investigates Fe-H, Fe-Ni-H and Fe-Si-H alloys in the laser-heated diamond anvil cell (DAC), where specimens are compressed at the tips of two opposing diamonds and heated by focused laser beams. Target pressures and temperatures are up to 150 GPa (~1.5 million atm) and in excess of 2000 K. Quantifying hydrogen-iron alloys at these conditions in the DAC has been challenging because H2 tends to break the anvils on heating. The team has recently demonstrated that this issue can be overcome by pulsed laser heating. This technique, coupled with an improved X-ray detection system at synchrotron facilities, allows the researchers to quantify in situ the effect of hydrogen on the structure, equation of state, bulk modulus and melting temperatures of iron-rich alloys. Run products are investigated by electron microscopy to study their texture and the partitioning of Si and Ni among the phases in presence. Ab initio calculations guide the experimental approach and the data analysis. The key questions leading the research are: (1) Does hydrogen change the crystal structures of iron metal and alloys in the Earth's core? What is the effect of hydrogen on (2) the equations of state of iron metal and alloys and (3) their melting temperatures at core conditions?This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

半个多世纪以来，科学家们已经知道地核——地球中心3500公里的大球，主要由铁组成——的密度比纯铁的密度低5-10%。这是因为地核中含有轻元素，如Si、O、S、C和h。当地核冷却形成固体内核时，轻元素优先在液体外核中分离。这个过程部分地为磁场提供能量，磁场保护我们免受太阳风的影响。此外，了解地核的组成对限制其形成和演化至关重要。因此，在地球深处的极端压力和温度条件下，金属铁中的轻元素已被广泛研究。然而，由于实验的限制，氢对核心材料的影响在很大程度上仍然未知。在这里，研究人员调查了氢是如何影响核心性质的。利用最新的技术发展，他们研究了地球内部高压和高温下的铁氢系统。这些实验在国家同步加速器设施中进行，量化了富铁合金的熔化温度和密度。原子水平的理论计算指导实验方法和数据分析。这些结果改进了目前的地核模型，对理解地核的形成、演化和当今的磁场具有重要意义，并在地球科学领域产生了许多影响。这个为期两年的项目为一名早期职业女性科学家和一名研究生提供支持，并为最先进的矿物物理学的本科生暑期实习生提供培训机会。它还通过在亚利桑那州立大学的开放日活动上的演讲，提高了公众对氢在地球上的重要作用的认识。在这里，研究小组在激光加热的金刚石砧细胞（DAC）中研究了Fe-H， Fe-Ni-H和Fe-Si-H合金，其中样品被压缩在两个相对的金刚石的尖端，并被聚焦的激光束加热。目标压力和温度高达150 GPa（~ 150万大气压），超过2000 K。在DAC中对这些条件下的氢铁合金进行量化是具有挑战性的，因为H2在加热时往往会破坏铁砧。该团队最近证明，这个问题可以通过脉冲激光加热来解决。该技术与同步加速器设施中改进的x射线检测系统相结合，使研究人员能够就地量化氢对富铁合金的结构、状态方程、体积模量和熔化温度的影响。用电子显微镜研究了产物的织构和相间Si和Ni的分配。从头计算指导实验方法和数据分析。引导这项研究的关键问题是：(1)氢是否会改变地核中铁金属和合金的晶体结构？氢对(2)铁金属和合金的状态方程和(3)它们在核心条件下的熔化温度的影响是什么？该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Effect of nickel on the high-pressure phases in FeH

• DOI: 10.1103/physrevb.104.224106
• 发表时间: 2021-12
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: H. Piet;A. Chizmeshya;Bin Chen;S. Chariton;E. Greenberg;V. Prakapenka;S. Shim

Stable hexagonal ternary alloy phase in Fe-Si-H at 28.6–42.2 GPa and 3000 K

Fe-Si-H 中稳定的六方三元合金相，在 28.6–42.2 GPa 和 3000 K 下

• DOI: 10.1103/physrevb.105.104111
• 发表时间: 2022
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Fu, Suyu;Chariton, Stella;Prakapenka, Vitali B.;Chizmeshya, Andrew;Shim, Sang-Heon
• 通讯作者: Shim, Sang-Heon

Hydrogen solubility in FeSi alloy phases at high pressures and temperatures

• DOI: 10.2138/am-2022-8295
• 发表时间: 2022-12-16
• 期刊: AMERICAN MINERALOGIST
• 影响因子: 3.1
• 作者: Fu, Suyu;Chariton, Stella;Shim, Sang-Heon
• 通讯作者: Shim, Sang-Heon

Water‐Induced Diamond Formation at Earth's Core‐Mantle Boundary

地核-地幔边界处的水诱发钻石形成

• DOI: 10.1029/2022gl098271
• 发表时间: 2022
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Ko, Byeongkwan;Chariton, Stella;Prakapenka, Vitali;Chen, Bin;Garnero, Edward J.;Li, Mingming;Shim, Sang‐Heon
• 通讯作者: Shim, Sang‐Heon