“Thermal Mirror” Method for Measuring Physical Properties of Multilayered Coatings
“Thermal Mirror” Method for Measuring Physical Properties of Multilayered Coatings
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测量多层涂层物理性能的“热镜”法
DOI：
10.1007/s10765-007-0157-3
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发表时间：
2007
影响因子：
2.2
通讯作者：
G. Rudin
中科院分区：
文献类型：
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作者：
T. Elperin;G. Rudin
在这项研究中，分析了用于测量低导热率不透明多层和功能梯度涂层物理性能的光热位移（“热镜”）方法的理论原理。该方法利用功率激光束对试件进行局部加热，在试件内形成二维瞬态温度场。光热位移方法的物理基础是由于非均匀热膨胀而导致照射表面的非平稳屈曲和位移。表面由第二个激光的低功率探测光束监测，该光束从样本反射，即该系统作为凸面“热镜”运行。光致位移随时间变化，探测光束根据位移的斜率以不同的角度反射。通过位置传感器测量作为时间函数的偏转角，并将这些测量结果与偏转角对时间和涂层物理性质的理论依赖性进行比较。这种依赖性是通过二维热弹性问题的求解来分析确定的。结果表明，对于由基材和涂层组成的样本，如果预先测量或已知基材的类似特性，则可以确定涂层的特性，例如热扩散率和线性热膨胀系数。
In this study theoretical principles underlying the photothermal displacement (“thermal mirror”) method for measuring physical properties of opaque multilayered and functionally graded coatings with low thermal conductivity are analyzed. In this method, the specimen is locally heated by a power laser beam, and a two-dimensional transient temperature field is formed in a specimen. The physical basis for the photothermal displacement method is the non-stationary buckling and displacement of an irradiated surface due to a non-uniform thermal expansion. The surface is monitored by a low-power probe beam of a second laser, which is reflected from the specimen, i.e., the system operates as a convex “thermal mirror.” The photoinduced displacement varies with time, and the probe beam is reflected at a different angle depending on the slope of the displacement. The deflection angle is measured as a function of time by a position sensor, and the results of these measurements are compared with the theoretical dependence of the deflection angle on time and physical properties of a coating. This dependence was determined analytically from the solution of the two-dimensional thermal elasticity problem. It is shown that for the specimen composed of a substrate and a coating it is feasible to determine the properties of the coating, e.g., the thermal diffusivity and coefficient of linear thermal expansion provided that the analogous properties of the substrate are previously measured or otherwise known.