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Determination of thermal diffusivity in diathermic materials by the laser-flash technique
Rainer Hofmann, Oliver Hahn, Friedrich Raether, Harald Mehling, Jochen Fricke

A new method has been developed for the determination of thermal diffusivity in diathermic (i.e. semi-transparent and nonabsorbing) materials. It accounts for the direct radiative exchange between front and rear side coatings often used in laser-flash measurements. By a comparison of laser-flash measurements on uncoated and graphite-coated glass samples, the reliability of the new method was experimentally confirmed. Numerical simulations on float glass and calcium difluoride showed that for the determination of thermal diffusivity both materials can be approximately described as diathermic within an error of less than 3%. In contrast, it is shown that at 823 K the determination of the thermal diffusivity leads to an error of 12% for glass and of 9% for calcium difluoride, if the direct radiative interaction is neglected.

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