Study On Photothermal Measuring Method Of The Thermal Conductivity Tensor Of Anisotropic Materials With Unknown Principal Axes

Developmental status and basal theories of photothermal technology were introduced.The thermally physical characteristics of opaque Anisotropic Materials were studied by using photothermal radiation. At first, the 3-D theoretical model of photothermal radiation was built in the cylindrical coordinate axes, by reviewing thermally uniaxial materials irradiated by continuously modulated beam. Compared with the 3-D theoretical model that was obtained when the incident laser was Gaussian beam, the 1-D one that was obtained when the incident beam irradiated equably the sample was defective. At the same time, if the ratio between the radius of incident Gaussian beam and that of the sample was over 0.7, An important conclusion, the 3-D theoretical model was replaced completely by the 1-D one, was drawn .After that, according to thermal conduction theories of anisotropic materials that were irradiated with continuously modulated laser, a photothermal measuring method about the thermal conductivity tensor and the orientation of the principal axis of the conductivity of arbitrarily opaquely anisotropic materials in the Descartes coordinate axes was given by virtue of the theories of So(3) group rotation. And taking example for the graphite, the method was correct by demonstrating experimentally.