MEASUREMENT OF THERMAL-EXPANSION COEFFICIENT OF MO/PSZ SINTERED COMPOSITES BY LASER SPECKLE PHOTOGRAPHY

A non-contact measurement system for the coefficient of thermal expansion (CTE), as well as the displacement of a rigid body, using laser speckle photography has been constructed which enables to determine precisely a regional CTE variation in a specimen at temperatures as high as 1473 K. Mo/PSZ sintered composites was used for the measurement of the dependence of CTE on temperature and Mo/PSZ mixing ratio. A double photographic exposure of laser speckle patterns before and after thermal displacement and a re-irradiation of laser beam to the photographic film yield a Young's fringe corresponding to the displacement involved. A stepwise temperature increment method has been employed to get better speckle patterns and for the determination of CTE at high temperature. It has been found that, Au coating is needed to avoid the fading of speckle patterns and thus of the Young's fringes due to laser beam transparency through PSZ. The temperature and composition dependences of CTE of Mo/PSZ composites have been found to be determined with sufficient accuracy. It has been suggested the present method will be applied for the determination of regional CTE variation in functionally gradient materials having graded compositional distributions in themselves.