Acquisition of a Laser-Flash Apparatus for Measurement of Thermal Diffusivity to 2000C

0132275霍夫迈斯特热传输涉及地球科学中所有尺度的问题，例如，实验室实验、火成岩的结晶和结构、韧性断层、地幔柱、地球对流模式以及行星的形成和演化。理解这些过程需要了解热扩散率（D）或热导率（k = DrCV）。物理性质k描述了热量从刚性材料的热端流向冷端的速率，因此属于传导过程。当材料也流动时（对流过程），D适用。 由于密度（r）和热容（CV）在温度下受到很好的约束或很容易预测，D的测量提供了理解热传输所需的数据。 然而，对于地质和行星材料，D的温度依赖性通常是未知的，并且可用的数据是不一致的。在以前的方法中存在差异，因为热在实验的短尺度上以特定于给定实验的方式作为光传输。因此，这些结果不是一个实质性的属性。 这种复杂的情况之所以存在，是因为行星材料在某些波长的光下是透明的（而光就是热）。材料科学的技术进步已经导致了克服这个问题的设备。这笔赠款将用于购买这种激光闪光装置，以测量从室温到2000oC的热扩散率（D）。在美国的地球科学研究设施中，没有类似的仪器。该仪器不仅使现有数据不足的1000 oC范围（其中大多数数据已有30年历史）增加了一倍，而且使用方便快捷，并提供熔体的D（T）。由激光闪光装置产生的数据为k的唯象模型的T依赖性提供了所需的测试。 理论和实验相结合，不仅可以将测量的D和k外推到地球科学感兴趣的所有条件，而且将进一步加深我们对输运性质微观基础的理解。

0132275HofmeisterHeat transport pertains to problems on all scales in Earth science, e.g., laboratory experiments, crystallization and texture of igneous rocks, ductile faulting, mantle plumes, Earth's convection patterns, and planetary formation and evolution. Understanding such processes requires knowledge of either the thermal diffusivity (D) or the thermal conductivity (k = DrCV ). The physical property k describes the rate at which heat flows from the hot to the cold end of a rigid material, and thus pertains to conductive processes. When the material flows as well (convective processes), D applies. Because density (r) and heat capacity (CV) at temperature are well-constrained or readily predicted, measurements of D provide the data needed to understand heat transport. However, the temperature dependence of D is generally unknown for geological and planetary materials and the available data are inconsistent. Disparities exist in the previous methods because heat is transported as light over the short scales of the experiments in a manner that is specific to a given experiment. The results are thus not a material property. This complex situation exists because planetary materials are transparent at some wavelengths of light (and light is heat). Technological advances in materials science have led to a device which overcomes this problem. Funds from this grant will support acquisition of such a laser-flash apparatus to measure thermal diffusivity (D) from room temperature to 2000oC. No comparable instrument exists in Earth Science research facilities in the U.S. The apparatus not only doubles the 1000oC range typical for the scant existing data, most of which are 30 years old, but is easy and rapid to use, and provides D(T) on melts. The data generated by the laser flash apparatus provide the needed tests for the T dependence for phenomenological models for k. Combining theory and experiment not only allows extrapolation of measured D and k to all conditions of interest to Earth science, but will further our understanding of the microscopic basis of transport properties.***