Effect of Sample-Shape Imperfection on Uncertainty in Measurements of the Thermal-Conductivity by the Laser-Flash Method

Resumo

The effect of the geometric shape of the samples on the uncertainty in measurements of the thermal conductivity coefficient of materials by the laser-flash method is investigated. A mathematical model simulating the process of measuring the thermal conductivity of samples made of graphite, Mg₂Si_0.4Sn_0.6, and bismuth telluride by the laser-flash method is created in the Comsol Multiphysics software. Cylindrical samples with plane-parallel sides, samples shaped as a truncated cylinder, as well as parallelepiped-shaped samples with a square base are investigated. It is shown that the uncertainty in the measurements does not exceed 2% for the samples with plane-parallel sides and sizes up to 12.7 mm. For the samples shaped as a truncated cylinder with a diameter of 3 mm and at an inclination angle of φ = 1.5°, the measurement uncertainty does not exceed 3%. With increasing sample diameter and angle φ, the measurement uncertainty increases significantly.