Improvement of the thermal diffusivity measurement of thin samples by the flash method

In the conventional thermal diffusivity measurement by the flash method, the effect of finite width of the flash pulse and the effect of graphite layers on both front and rear surfaces are often neglected. In the present study, the error of the half-time method caused by the graphite layers is theoretically assessed and the minimum thickness ratio required for accurate measurement by the half-time method is investigated. In order to minimize the error of the flash method in measuring the thermal diffusivity of a thin sample coated by graphite, 3-layer model is proposed that includes corrections of the finite pulse effect and the heat loss effect. The proposed model is applied to measure the thermal diffusivities of copper, aluminum, iron and Inconel 600. It is found that the proposed 3-layer model reduces the measurement error considerably.