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EAGER: Testing New Formulae for Pressure Derivatives of Specific Heat, Thermal Conductivity, and Thermal Diffusivity

EAGER：测试比热、热导率和热扩散率的压力导数的新公式

基本信息

批准号：
2122296
负责人：
Anne Hofmeister
金额：
$ 3.73万
依托单位：
Washington University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-07-01 至 2024-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2122296&HistoricalAwards=false
关键词：
EAGER Testing New Formulae Pressure

项目摘要

Heat flow is ubiquitous. How efficiently matter transports heat is of fundamental importance. Understanding heat transport is critical to numerous engineering and scientific endeavors, such as designing tiny electronic devices or modeling the cooling rate of large planetary bodies. The most accurate method for measuring heat transport properties (laser-flash analysis) has shown that values from diverse types of solids depend on the length over which heat is flowing. Static properties (e.g., density) do not behave in this manner, so tests against length were not made earlier. This finding led to new formulae describing thermal dynamic behavior (conductivity, diffusivity, and heat capacity) as functions of pressure. The formulae describe steady-state conditions. This contrasts with equations of classical thermodynamics developed in the 1800s to describe idealizations such as constant temperature. These findings are critical for Geophysics because matter in Earth’s deep interior is under extreme pressures. Here, the researchers will further test the formulation which they previously validated for a limited number of solids and over a limited range of temperature. They now quantify heat properties in a wider range of solids, and other states of matter, and over a greater temperature range. They use a new laser flash apparatus for liquids (water in particular); the new apparatus allows measuring heat capacity and attains low temperature. They re-analyze data on gases available in the literature. The goal is extreme accuracy in the measurement, notably that of initial slope and temperatures near ambient conditions. Both the old and the new formulation for thermal properties are tested. This project may initiate a paradigm shift in the way we quantify heat flow. Its outcomes improve our understanding of the microscopic mechanism responsible for it. They have potentially wide repercussions for pure and applied physical sciences. The project also supports a female scientist with disability and provides training to undergraduate students at University of Washington. Discovery that thermal diffusivity (D) and thermal conductivity (k) of insulators, semi-conductors, metals, alloys, and glasses depends on the length-scale (L) of measurements has repercussions for pure and applied physical sciences. Linear dependence on L for small length-scales agrees with dimensional analysis of Fourier’s heat equation. It shows that results from diamond anvil cell experiments are problematic, foremost because these are benchmarked against 1 atm data for L 100 times larger. Reliable data below 2 GPa pressure exist on mm-sized samples from well-worn methods. Analyzing these results for 25 solids of diverse bond type show that the logarithmic pressure derivative of specific heat (cP) equals -1 times the linear compressibility. Mathematical analysis allowing for k depending on L (i.e., volume) also related its logarithmic pressure response to equation-of-state properties, and likewise for D. The new k vs. P formula was confirmed against reliable data for 20 solids. Therefore, the team’s preliminary tests suggest, but do not prove, that the new formulae are thermodynamic identities describing steady-state conditions, which is a commonly encountered restriction. Isothermal is not, because thermal emissions are ubiquitous. Thus, the time-independent formulations from classical thermodynamics do not describe properly the time-depended conditions in the Earth where heat is flowing. To test the new formula for cP vs. P, databases already in existence can be used. Since a generally applicable formula for steady state is the goal, diverse states of matter and bond type are being tested. The researchers also collect data on liquids and ices (e.g., water, metals melting near 298 K). They use a new laser flash apparatus – the LFA467 instrument and its commercial low-pressure cell to 10 MPa - covering ~100 to 500°C, that simultaneously measures D and cP. Spurious radiative transfer is removed via coating the interior of the cell with graphite. A dilatometer spanning this T range is used when density vs T is not available, to constrain k. Using machine learning to parameterize cP, D, and k vs. P, L, T, will either distinguishing whether the new or previous formulae are correct, or will lead to new and accurate formulae, permitting extrapolation to high pressure inside Earth. Thus, the proposed work provides basic physics that is essential to Geophysics. Confirmed P derivatives of cP and k (or D) pertain to any process inside Earth and other large bodies. The work outcomes lead to improving accuracy of geophysical and petrologic models and has potential to improve our understanding of planetary interiors. Since new thermodynamic identities have not been developed for ~100 years, other physical sciences, such as study of chemical reactions, may be impacted.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.

热流无处不在。物质如何有效地传输热量至关重要。了解热传输对于许多工程和科学工作至关重要，例如设计微型电子设备或模拟大型行星体的冷却速率。测量热传输特性的最准确方法（激光闪光分析）表明，不同类型固体的值取决于热量流动的长度。静态属性（例如密度）不会以这种方式表现，因此之前没有进行长度测试。这一发现催生了将热动态行为（电导率、扩散率和热容）描述为压力函数的新公式。这些公式描述了稳态条件。这与 1800 年代开发的用于描述恒温等理想化的经典热力学方程形成鲜明对比。这些发现对于地球物理学至关重要，因为地球内部深处的物质承受着极大的压力。在这里，研究人员将进一步测试他们之前在有限数量的固体和有限的温度范围内验证过的配方。他们现在可以量化更广泛的固体和其他物质状态以及更大的温度范围内的热特性。他们对液体（特别是水）使用了一种新的激光闪光装置；新设备可以测量热容量并达到低温。他们重新分析文献中提供的气体数据。目标是实现极高的测量精度，特别是初始斜率和接近环境条件的温度。新旧配方的热性能均经过测试。该项目可能会引发我们量化热流方式的范式转变。其结果提高了我们对其微观机制的理解。它们对纯粹和应用物理科学具有潜在的广泛影响。该项目还支持一名残疾女科学家，并为华盛顿大学的本科生提供培训。绝缘体、半导体、金属、合金和玻璃的热扩散率 (D) 和导热率 (k) 取决于测量长度 (L) 的发现对纯粹和应用物理科学产生了影响。小长度尺度对 L 的线性依赖性与傅里叶热方程的量纲分析一致。它表明金刚石砧座实验的结果是有问题的，最重要的是因为这些结果是以 L 100 倍大的 1 atm 数据为基准的。毫米大小的样品通过陈旧的方法获得了低于 2 GPa 压力的可靠数据。分析 25 种不同键类型的固体的结果表明，比热 (cP) 的对数压力导数等于 -1 倍的线性压缩率。数学分析允许 k 取决于 L（即体积），还将其对数压力响应与状态方程属性相关联，对于 D 也是如此。新的 k 与 P 公式根据 20 种固体的可靠数据得到了证实。因此，该团队的初步测试表明，但并未证明，新公式是描述稳态条件的热力学恒等式，这是一个常见的限制。等温则不然，因为热排放无处不在。因此，经典热力学的时间无关公式不能正确描述地球上热量流动的时间相关条件。为了测试 cP 与 P 的新公式，可以使用现有的数据库。由于普遍适用的稳态公式是目标，因此正在测试不同的物质状态和键类型。研究人员还收集液体和冰的数据（例如水、在 298 K 附近熔化的金属）。他们使用新型激光闪光设备——LFA467 仪器及其商用低压单元（10 MPa）——覆盖范围约 100 至 500°C，可同时测量 D 和 cP。通过在电池内部涂上石墨来消除杂散辐射传输。当密度与 T 不可用时，使用跨越该 T 范围的膨胀计来约束 k。使用机器学习对 cP、D 和 k 与 P、L、T 进行参数化，可以区分新公式或以前的公式是否正确，或者得出新的准确公式，从而可以外推到地球内部的高压。因此，所提出的工作提供了对地球物理学至关重要的基础物理学。已确认的 cP 和 k（或 D）的 P 导数适用于地球和其他大型天体内部的任何过程。这些工作成果提高了地球物理和岩石学模型的准确性，并有可能提高我们对行星内部结构的了解。由于新的热力学恒等式已经约 100 年没有被开发出来，其他物理科学，例如化学反应的研究，可能会受到影响。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。