Experimental Investigations of Carbon in Earth's Core

地球碳的实验研究？核心知识价值。以前的研究提出，全球碳循环涉及Fe3C或Fe7C3作为地球固体部分的主要成分。尽管测试富含碳化物的内核假设的关键数据仍然缺失。Fe-C二元体系相关系的实验结果限制在70 GPa以内。声速数据仅适用于Fe3C，在300 K条件下高达68 GPa，在高温条件下高达47 GPa。Fe3C在压力下的密度测量已达到~ 200gpa，但高温数据很少。特别是，需要实验来评估70 GPa附近的磁转变对碳化铁的热弹性和振动性能的影响，并量化温度对其磁性、密度和声速的影响。提出了利用多砧和金刚石砧单元压力装置研究碳化铁在核心压力和~ 3000 K下的压缩和熔化行为。具体目标包括：[1]利用核共振散射法测定Fe3C和Fe7C3的部分声子密度；[2]用同步x射线衍射法建立了Fe3C和Fe7C3的态热方程；[3]采用原位x射线衍射和聚焦离子束fib猝灭分析相结合的方法确定了Fe-C二元体系的共晶成分。提议的活动将提供关于候选碳化铁与岩心压力和高温的相关系、密度和声速的新数据，从而能够对以碳为主要成分的内核模型进行严格的测试。预期的结果将增进我们对地球的了解。深碳循环是固体地球研究的一个核心和及时的问题。这些研究将通过阐明磁体积和非谐性在潜在核材料的热力学和晶格振动中的作用，为核化学的最终模型奠定基础。核心碳含量的关键限制将补充地球化学，地震学和地球动力学研究，以扩大深部地球研究的前沿。这项工作还将有助于天体物理学和行星科学研究碳从恒星诞生到行星分化的途径，以及材料科学和凝聚态物理学研究极端环境下碳基材料和强相关系统的行为。更广泛的影响。首席PI致力于通过课程设置、讲座和辅导课（例如，为密歇根数学和科学学者计划和动态地球研究暑期学校合作研究所）从高中到博士后水平的教学和培训。拟议中的实验将训练一名研究生利用密歇根大学高压研究实验室和阿贡国家实验室先进光子源（APS）的最先进实验技术解决基础科学问题。拟议的活动将通过区域和国家设施的合作项目，包括地球物理实验室、APS和国家纳米技术基础设施网络（NNIN），加强研究和教育的基础设施。该项目将为社区制定校准标准，以支持与碳有关的研究。该提案将涉及女性研究人员，并为陈博士作为新PI提供部分支持。pi将继续积极通过出版物、国内和国际会议、互联网和新闻媒体广泛传播研究成果。

Experimental Investigations of Carbon in Earth?s Core Intellectual merit. Previous studies proposed that the global carbon cycle involved Fe3C or Fe7C3 as a dominant component in the solid portion of Earth?s core, even though critical data to test the hypothesis of carbide-rich inner core are still missing. Experimental results on the phase relation of the Fe-C binary system are limited to 70 GPa. Sound velocity data are only available for Fe3C, under conditions up to 68 GPa at 300 K and up to 47 GPa at high temperatures. Density measurements on Fe3C have reached ~ 200 GPa in pressure, but high temperature data are scarce. In particular, experiments are needed to assess the effects of magnetic transition near 70 GPa on the thermoelastic and vibrational properties of the iron carbides, and to quantify the influence of temperature on their magnetism, density and sound velocities. It is proposed to investigate the compression and melting behavior of iron carbides up to the core pressure regime and ~ 3000 K using multi-anvil and diamond anvil cell pressure devices. Specific goals include: [1] determine the partial phonon density of Fe3C and Fe7C3 using the nuclear resonant scattering method; [2] establish the thermal equation of state of Fe3C and Fe7C3 using the synchrotron X-ray diffraction methods; [3] determine the eutectic composition of the Fe-C binary system using a combination of in situ X-ray diffraction and focused ion beam FIB-based quench analysis methods. The proposed activities will provide new data on the phase relations, densities, and sound velocities of candidate iron carbides to core pressures and high temperatures, thus enabling a stringent test of inner core models involving carbon as a major component. The expected results will advance our understanding of Earth?s deep carbon cycle, a central and timely issue in solid Earth research. The investigations will establish stepping-stones toward an ultimate model of core chemistry by elucidating the role of magneto-volume and anharmonicity in the thermodynamics and lattice vibration of potential core materials. Key constraints on the carbon content of the core will complement geochemical, seismological, and geodynamic studies to expand the frontier of deep Earth research. This work will also contribute to astrophysics and planetary science on the pathways of carbon from star birth to planet differentiation, and to materials science and condensed-matter physics on the behavior of carbon-based materials and strongly correlated systems under extreme environments. Broader impact. The lead PI is committed to teaching and training at high school to postdoctoral levels through course offerings, lectures, and tutorial sessions (e.g., for the Michigan Math and Science Scholar program and at the Cooperative Institute for Dynamic Earth Research Summer Schools). The proposed experiments will train a graduate student to tackle fundamental scientific problems using the state-of-the-art experimental techniques in the high-pressure research laboratories at U. Michigan and the Advanced Photon Source (APS) at the Argonne National Laboratory (ANL). The proposed activity will enhance the infrastructure for research and education through collaborative projects at regional and national facilities including the Geophysical Laboratory, APS, and National Nanotechnology Infrastructure Network (NNIN). The project will produce calibration standards for the community to support carbon-related research. The proposal will involve female researchers and provide partial support for Dr. Chen as a new PI. The PIs will continue to actively disseminate research results broadly through publications, national and international meetings, the Internet, and news media.