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

A non-contact measurement system for the coefficient of thermal expans ion (CTE), as well as the displacement of a rigid body, using laser sp eckle photography has been constructed which enables to determine prec isely a regional CTE variation in a specimen at temperatures as high a s 1473 K. Mo/PSZ sintered composites was used for the measurement of t he dependence of CTE on temperature and Mo/PSZ mixing ratio. A double photographic exposure of laser speckle patterns before and after therm al displacement and a re-irradiation of laser beam to the photographic film yield a Young's fringe corresponding to the displacement involve d. A stepwise temperature increment method has been employed to get be tter speckle patterns and for the determination of CTE at high tempera ture. 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 suf ficient accuracy. It has been suggested the present method will be app lied for the determination of regional CTE variation in functionally g radient materials having graded compositional distributions in themsel ves.