CSEDI Collaborative Research: Experimental and Theoretical Investigations on the Elastic and Viscoelastic Properties of Fe-Ni-C Liquids

CSEDI合作研究：Fe-Ni-C液体弹性和粘弹性的实验和理论研究

• 批准号: 1565678
• 负责人: Jianwei Wang
• 金额: $ 18.32万
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-15 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1565678&HistoricalAwards=false
• 关键词: CSEDI; Collaborative; Research; Experimental; Theoretical

The Earth's core, the most remote and dynamic part of our planet, is composed of liquid iron alloys solidified at its center. The nature and dynamics of the core are closely related to manifold geophysical problems such as the driving force of mantle convection, the geodynamo, and planetary evolution. The core is predominantly iron (Fe) alloyed with 5-10% nickel (Ni) and some lighter elements, such as sulfur (S), silicon (Si), carbon (C), oxygen (O), and hydrogen (H). The knowledge of the properties of Fe-rich alloys and liquids under relevant core conditions is a prerequisite for understanding the composition, thermal state and dynamics of the core. In comparison to crystalline iron alloys for the inner core, there exists a remarkable lack of data on liquid properties of iron-rich alloys due to experimental challenges, which have been investigated at conditions far below those expected for the outer core. The lack of data on liquid properties and great challenges facing experimental investigations under relevant core conditions are expected to continue in the foreseeable future. This prompts the team to adopt a synergistic approach by integrating experiments at experimentally-achievable pressures with computations up to core conditions. The focus of this collaborative research will be on the elastic and viscoelastic properties of Fe-Ni-C liquids under high pressures through the synergy between experiment and theory. This approach for investigating liquid properties represents a potential methodology for studying liquid properties under extreme conditions, so as to speculate on the suitability of such combined efforts for similar high-pressure liquid state physics research. The proposed research offers a unique opportunity to engage graduate and undergraduate students to utilize state-of-the-art experimental techniques and computational tools at multi-scale facilities (departmental, university, and national laboratory) for solving fundamental problems in an active research area.The elastic and viscoelastic properties of Fe-Ni-C liquids will be investigated at high pressures by experimental techniques such as X-ray absorption, ultrasonic interferometry, X-ray diffraction, and X-ray viscometry, in combination with computational techniques, to establish a comprehensive mineral physics database on the density, sound velocity, viscosity, and structure of the liquids in a previously uncharted pressure-temperature-composition sector. The laboratory data will provide an important foundation on which the interpretation of ultrahigh pressure laboratory data and theoretical data will be based. The low-pressure data will be used to benchmark and validate results from theoretical calculations at low-pressure, and the higher-pressure calculation results will be used to estimate and predict liquid properties under core conditions. Such a methodology largely eliminates errors often induced in long extrapolations from low-pressure to core pressures, and identifies prospective biases in theoretical calculations. High pressure-temperature behaviors of the iron-rich liquids by the synergistic efforts from laboratory experiments and theoretical calculations will help improve our understanding of the physics and chemistry of the core. Stringent tests of carbon-rich core composition models for the outer core will be performed based on the liquid properties determined from this research. The outcome of the proposed projects, i.e., structure, density, sound velocity, and viscosity of core materials, will become essential parts of the study on carbon reservoirs and deep carbon cycle in the Earth and planetary interiors. The new experimental data could also be readily used in the discussion of planetary cores, such as the lunar core. The team is committed to disseminating the results through peer-reviewed journal publications and to publicizing their work to their local and greater communities through news releases, public lectures, and their research websites.

地核是地球上最遥远、最活跃的部分，由在其中心凝固的液态铁合金组成。地核的性质和动力学与地幔对流驱动力、地球发电机、行星演化等多种地球物理问题密切相关。核心主要是铁 (Fe)，并含有 5-10% 的镍 (Ni) 和一些较轻的元素，例如硫 (S)、硅 (Si)、碳 (C)、氧 (O) 和氢 (H) 。了解相关堆芯条件下富铁合金和液体的特性是了解堆芯的成分、热状态和动力学的先决条件。与内核的结晶铁合金相比，由于实验挑战，富铁合金的液体特性明显缺乏数据，这些实验的条件远远低于外核的预期条件。在可预见的未来，液体特性数据的缺乏以及相关核心条件下的实验研究面临的巨大挑战预计将继续存在。这促使团队采用协同方法，将实验可实现的压力下的实验与核心条件的计算相结合。 这项合作研究的重点将是通过实验和理论的协同作用来研究高压下 Fe-Ni-C 液体的弹性和粘弹性能。这种研究液体性质的方法代表了一种研究极端条件下液体性质的潜在方法，从而推测这种联合努力是否适合类似的高压液态物理研究。拟议的研究提供了一个独特的机会，让研究生和本科生在多规模设施（部门、大学和国家实验室）利用最先进的实验技术和计算工具来解决活跃研究领域的基本问题通过X射线吸收、超声干涉、X射线衍射、X射线粘度测定等实验技术，结合计算技术，研究高压下Fe-Ni-C液体的弹性和粘弹性特性，建立综合矿物物理学关于以前未知的压力-温度-成分领域中液体的密度、声速、粘度和结构的数据库。实验室数据将为超高压实验室数据和理论数据的解释提供重要基础。低压数据将用于对低压理论计算结果进行基准测试和验证，高压计算结果将用于估计和预测岩心条件下的液体特性。这种方法在很大程度上消除了从低压到核心压力的长时间外推中经常引起的错误，并识别了理论计算中的预期偏差。通过实验室实验和理论计算的协同努力，富铁液体的高压-温度行为将有助于提高我们对地核物理和化学的理解。将根据本研究确定的液体特性对外核的富碳核心成分模型进行严格的测试。拟议项目的成果，即核心材料的结构、密度、声速和粘度，将成为地球和行星内部碳库和深层碳循环研究的重要组成部分。新的实验数据也可以很容易地用于行星核心的讨论，例如月球核心。该团队致力于通过同行评审的期刊出版物传播研究结果，并通过新闻稿、公开讲座和研究网站向当地和更大的社区宣传他们的工作。