Photo-thermoelectric technique for anisotropic thermal diffusivity measurements

A photo-thermoelectric technique was employed to perform anisotropic thermal diffusivity measurements in nanocomposites and multilayer structures. In this technique a thermal wave is produced into the specimen by absorption of modulated laser radiation while the thermal wave is detected using a fast thermoelectric effect at the junction between a sharp wire probe and the sample surface. To allow effective heating and signal detection, additional thin-film layers may need to be deposited onto the samples. However, heat transport through the layers and into the thermoelectric probe may affect the thermal transport measurements. This work presents a heat conduction model that takes these effects into account and can be used to guide the selection of the probe and thin-film materials and thicknesses such that the accuracy of the thermal measurements is minimally affected. The discussion of the experimental technique is illustrated with simulation results, calibration experiments, and an example of anisotropic thermal diffusivity characterization in aligned multiwall carbon nanotube arrays.