基于金刚石顶砧的高压原位热导率测量方法研究

Diamond anvil cell (DAC) can generate high pressures of hundreds of gigapascals. Based on the methods of in-situ physical parameter measurements, it has been used in various fields of scientific research. However, due to the limitations of difficult measurement of heat flux within the DAC, in-situ thermal conductivity measurements cannot be fulfilled in DAC at steady heat flux conditions, which results in many investigations about the heat properties of condensed matters cannot be conducted and becomes the shortcoming of high pressure research. In this project, in-situ thermoconductivity will be obtained by combining the in-situ temperature measurement at high pressures and the analysis of temperature field at the constant heat flux and using the finite element analysis of the distribution of temperature field to construct the calculation model of heat flux according to high pressure experimental conditions , with which the problem of heat flux calculation in DAC can be avoided. For accurately obtaining the sample, the temperature measurement will be conducted with the thin film thermocouple directly contacting with the sample in DAC, providing correct and reliable constraint conditions for temperature field calculation and providing scientific methods for the study of thermo behaviors and properties of matters under high pressure. The scheme of thermoconductivity measurement in the project will not generate unsteady state in the sample, so the obtained data can reflect the true basic physical properties and rules.

金刚石对顶砧（DAC）能够产生数百万大气压的高压。依托DAC的高压原位物理量探测方法，在众多科学研究领域有重要应用。然而，由于受DAC内热流计量困难的限制，利用DAC在稳恒热流条件下进行高压原位热导率测量无法实现，致使高压下凝聚态物质许多重要热学属性研究不能进行，成为高压科学研究的短板。本项目拟将高压原位温度测量方法和稳恒热流条件下的温度场分析结合起来，避开DAC内热流计量的难题，根据高压实验条件构建温度场计算模型，以高压原位测量的多点温度数据作为约束条件，利用有限元分析方法计算温度场分布，获得高压原位热导率数据。为准确获得样品温度，本项目将利用制备在金刚石压砧上的薄膜热电偶在DAC样品腔内直接进行温度测量，为温场分布计算提供准确可靠约束。为在高压下研究物质的热学行为和特性提供科学方法。本项目提出的热导率测量方案，不会在样品中产生非平衡态过程，所得到的数据能够反映样品的基本物理属性和规律。

依托金刚石对顶砧（DAC）装置的高压原位物性测量方法与技术创新，是高压科学最重要的基础和推动力。由于受热流计量障碍的限制，利用DAC在稳恒热流条件下进行高压原位热导率测量几乎无法实现，致使高压下与物质热学属性相关的研究难以展开，成为高压科学研究的短板。本项目避开热流计量的难题，将原位多点测温和稳恒热流条件下温度场分析相结合，以测温数据作为约束条件，实现了DAC内高压原位热导率的测量。按照申请书规划，项目组研制出DAC输运原位测试平台和新DAC装置，完成了DAC内稳恒热流场构建，创建了适合热导率测量的样品温度、压力测量以及在样品腔上制备热电偶和加温电炉新方法，建立起基于DAC的压砧、垫片热导率原位测量方法，给出了热导率准确测量所需遵循的原则，揭示了压力弛豫和氧逸度控制对测量的影响并提供了解决方案，利用新方法测量了金刚石单晶高温高压下的热导率及其随温度压力的变化规律。上述研究成果构建了完备的基于DAC的高压热导率原位测量科学方法，为高压下研究物质的热输运行为及特性提供科学途径。项目运行期间发表学术论文3篇，申报国家发明专利7项，获准2项，有6人获得博士学位。