Song Zhuorui, Zhang Lin, Wang Dihui, Tan Susheng, Ban Heng
Department of Mechanical Engineering and Material Science, University of Pittsburgh, Pittsburgh, Pennsylvania, 15261, USA.
Department of Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, 15261, USA.
Rev Sci Instrum. 2021 Mar 1;92(3):034903. doi: 10.1063/5.0019771.
A new approach to measure the cross-plane thermal diffusivity of a microscale slab sample, which can be fabricated by the focused ion beam and attached to a substrate, is proposed. An intensity-modulated pump laser is applied to heat the front surface of the sample uniformly, and the thermoreflectance signal is observed at the rear surface to evaluate thermal wave transport in the material. The thermal diffusivity can be obtained by fitting the phase lags of the experimental data with a theoretical model. The model was developed for the sample with thin-film coatings and heat transfer to the substrate. Although the absorbed heat can cause a significant DC temperature increase in the microscale sample, a thin-film coating with high thermal conductivity can effectively reduce the DC temperature increase within low thermal conductivity samples. To validate the method, we conducted measurements of a fused silica sample of 2.16 µm thickness, coated with 95 nm Ti film on the front surface and 120 nm Au film on the rear surface. The measured thermal diffusivity is in good agreement with the literature value. The uncertainty analysis shows that the measurement uncertainty is within 6%. This proposed approach, designed for microscale samples, offers a unique option for thermal property measurements of special materials, such as irradiated nuclear fuel or other irradiated materials, to enable microscale property determination while minimizing sample radioactivity.
提出了一种测量微尺度平板样品横向热扩散率的新方法，该样品可通过聚焦离子束制备并附着在基板上。采用强度调制泵浦激光均匀加热样品的前表面，并在后表面观察热反射信号以评估材料中的热波传输。通过将实验数据的相位滞后与理论模型拟合可获得热扩散率。该模型是针对带有薄膜涂层且热量向基板传递的样品开发的。尽管吸收的热量会使微尺度样品中的直流温度显著升高，但具有高导热率的薄膜涂层可有效降低低导热率样品中的直流温度升高。为验证该方法，我们对一个厚度为2.16 µm的熔融石英样品进行了测量，该样品前表面涂有95 nm的钛膜，后表面涂有120 nm的金膜。测得的热扩散率与文献值吻合良好。不确定度分析表明测量不确定度在6%以内。这种为微尺度样品设计的方法为特殊材料（如辐照核燃料或其他辐照材料）的热性能测量提供了一种独特的选择，能够在最小化样品放射性的同时确定微尺度性能。
