Cu2S相变过程中热扩散系数的精确测量和解析

材料发生相变时, 其结构和物理性能可能会发生剧烈的变化。采用激光闪射法测量热扩散系数时, 激光照射样品可能会伴随有光吸收/发射现象以及温度的显著升高, 导致其测量值偏离真实值。本工作以Cu₂S为研究对象, 发现激光照射样品后, 光吸收/发射的影响很小可以忽略, 但样品温度的升高则会明显影响热扩散系数的测量。通过构建具有不同石墨层厚度的石墨/Cu₂S双层结构, 利用石墨层减弱激光照射时Cu₂S样品的温度增加幅度, 成功使热扩散系数出现显著降低的起始温度接近采用DSC测量材料发生相变的起始温度。本研究进一步建立了石墨/Cu₂S双层结构样品的热流输运模型, 从石墨/Cu₂S双层结构样品的实验测试热扩散系数中解析出了Cu₂S在相变区间的本征热扩散系数。本工作对于理解和精确表征具有相变特征的离子导体热电材料、光敏、热敏材料的热扩散系数具有重要的意义。

Measurement and Analysis of Cu2S Thermal Diffusivity during Phase Transition

Thermal diffusivity can be measured by the laser flash method. Previous study showed that Cu₂S has extremely low thermal diffusivity during the first-order phase transition. However, when laser is applied on the measured sample, both the absorption/emission of light and the increase of temperature on the measured sample will occur. Their effects on the measurement accuracy of the thermal diffusivity during the phase transition have not been investigated yet. In this study, it is found that the absorption/emission of light has neglectable influence on the thermal diffusivity measurement of Cu₂S. However, the increase of temperature can significantly influence the measurement results and shift the temperature when the thermal diffusivity of Cu₂S starts to decrease below the starting temperature of the phase transition determined by DSC. This can be solved by building a Cu₂S/graphite double-layer structure via using the graphite to absorb part of the laser’s energy. Furthermore, a thermal transport model is developed to extract the real thermal diffusivity from the measured thermal diffusivity of the Cu₂S/graphite double-layer structure. This work is meaningful for accurate characterization and understanding of the thermal diffusivity of phase transition materials, photosensitive materials, and heat sensitive materials.