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: 0721449
• 负责人: Steven Jacobsen
• 金额: $ 16万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-12-01 至 2008-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0721449&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.

这项研究旨在通过实验理解地球内部的构成。 NSF组合财团已将深地球材料的高压和高温弹性确定为重大挑战。地震各向异性在地球所有主要边界层中的存在和内部核心强调了矿物质物理学的各向异性弹性数据的重要性。通过该奖项，最先进的Gigahertz-尿腔干涉仪将与下一代大容量，宝石和化学蒸气沉积（CVD）Diamond-Anvil压力细胞相连，以获得某些地球体上相关的地球地球形成型矿物质的准确状态热力学方程。高P-T实验将以PI开发的超声方法的最新突破，其中纯极极化的超声剪切波通过P-TO-S转换将其传播到Diamond-Anvil细胞中。使用大型宝石砧座的汽油加载技术将大大扩展工作P-T范围，可以进行超声测量。这项研究中的超声波实验将集中于较深的含硅酸盐，氧化物和金属，例如林木石，镁层岩和金属铁，因为这些材料的研究对于现有光学方法是有问题的。单晶样品中的声波旅行时间将用于确定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，很容易确定绝热的体积和剪切模量，以直接确定与地震学观察的直接比较。最后，将使用GHz-Technique准确地确定退火CVD钻石的弹性张量，因为对单个弹性常数的知识将有助于表征新的砧材料，并可以提供对CVD钻石晶体非凡机械性能的起源的见解。这项工作将培养地球物理实验室与德国拜罗伊特的Bayerisches Geoinstitut之间的合作，其中涉及至少一名研究生，可能是参加卡内基机构暑期实习计划的几位本科生实习生，该计划部分由PI管理。