High P-T Elasticity of Deep Earth Materials With New Gigahertz-Ultrasonic Techniques

利用新的千兆赫超声波技术实现地球深部材料的高 P-T 弹性

• 批准号: 0440112
• 负责人: Steven Jacobsen
• 金额: $ 29.87万
• 依托单位: Carnegie Institution of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-12-01 至 2007-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0440112&HistoricalAwards=false
• 关键词: Elasticity; Deep; Earth; Materials; New

This study is aimed towards understanding the constitution of Earth's interior through experiment. The high-pressure and high-temperature elasticity of deep-Earth materials has been identified as a major Grand Challenge by the NSF COMPRES consortium. The presence of seismic anisotropy within all of Earth's major boundary layers and inner core highlights the importance of anisotropic elasticity data from mineral physics. Through this award, a state-of-the-art gigahertz-ultrasonic interferometer will be interfaced with the next generation of large-volume, gem and chemical vapor deposition (CVD) diamond-anvil pressure cells in an effort to obtain accurate thermodynamic equations of state for some geophysically relevant Earth-forming minerals. The high P-T experiments will feature a recent breakthrough in ultrasonic methods developed by the PI, wherein purely-polarized ultrasonic shear waves are transmitted into the diamond-anvil cell using a P-to-S conversion. The employment of gas-loading techniques with large gem anvils will greatly extend the working P-T range over which ultrasonic measurements can be made. The ultrasonic experiments in this study will focus on the darker, Fe-bearing silicates, oxides and metals such as ringwoodite, magnesiowustite, and metallic iron because the study of these materials is problematic for existing optical methods. Acoustic-wave travel times in single-crystal samples will be used to determine P-wave velocity, S-wave velocity, elastic-wave anisotropy and the complete elastic tensor, from which the adiabatic bulk and shear moduli are readily determined for direct comparison with seismological observation. Finally, the elastic tensor of annealed CVD diamond will be accurately determined using the GHz-technique because knowledge of the individual elastic constants will help to characterize the new anvil material and may provide insight into the origin of the extraordinary mechanical properties of CVD diamond crystals. This work will nurture collaborations between the Geophysical Laboratory and the Bayerisches Geoinstitut in Bayreuth, Germany, involving at least one graduate student and possibly several undergraduate interns attending the Carnegie Institution Summer Internship Program, which is managed in part by the PI.

这项研究的目的是通过实验来了解地球内部的构成。美国国家科学基金会COMPRES协会将深地材料的高压和高温弹性确定为一项重大挑战。地震各向异性的存在下，所有地球的主要边界层和内核突出了矿物物理的各向异性弹性数据的重要性。通过该奖项，最先进的千兆赫兹超声波干涉仪将与下一代大容量宝石和化学气相沉积（CVD）金刚石压砧压力单元连接，以获得一些与地球形成矿物相关的精确热力学状态方程。高P-T实验将采用PI开发的超声波方法的最新突破，其中使用P-to-S转换将纯偏振超声波剪切波传输到金刚石砧室中。采用大宝石砧的气体加载技术将大大扩展超声波测量的工作P-T范围。在这项研究中的超声波实验将集中在较暗的，含铁的硅酸盐，氧化物和金属，如ringwoodite，magnesiowustite，和金属铁，因为这些材料的研究是有问题的现有的光学方法。声波在单晶样品中的传播时间将用于确定P波速度、S波速度、弹性波各向异性和完整的弹性张量，从中可以很容易地确定绝热体模量和剪切模量，以便与地震观测直接比较。最后，退火CVD金刚石的弹性张量将使用GHz技术准确地确定，因为单个弹性常数的知识将有助于表征新的砧材料，并可能提供对CVD金刚石晶体的非凡机械性能的起源的洞察。这项工作将促进地球物理实验室和德国拜罗伊特的Bayerisches Geoinstitut之间的合作，涉及至少一名研究生和可能的几名本科生实习生参加卡内基研究所暑期实习计划，该计划部分由PI管理。