Appropriate metallic coating for thermal diffusivity measurement of nonopaque materials with laser flash method and its effect

摘要

Laser flash method is used as a standard method for the thermal diffusivity measurements, which required the absorber of the laser pulse and the emitter of the infrared ray. However, due to the transmission, the nonopaque materials are difficult to be measured with the laser flash method directly. Quartz glass disks were evaluated with the laser flash method to ensure the appropriate measuring condition. To verify the appropriate metallic conditions, different thick platinum and gold coatings were sputtered on the both surfaces of the glass disks by controlling the sputtering time. Sample thickness dependence and temperature dependence of thermal diffusivity for quartz glass were also evaluated with the metallic coatings. In addition, thermal diffusivity of Al_2O_3-TiC ceramics disks, which is a certified reference material supplied by NMIJ, were also evaluated with and without the metallic coating to ensure the effect of metallic coating by the laser flash method. A 32.7 nm-thick gold coating was found to be the appropriate measurement condition in consideration of stability, operability and economic efficiency for the laser flash method.