Quantitative characterization of advanced porous ceramics based on a probabilistic theory of ultrasonic wave propagation

A straightforward nondestructive method based on the probabilistic theory of ultrasonic wave propagation [JSME Int. J., Ser. A, Mech. Mater. Eng. 39, 266 (1996)] was developed to quantitatively evaluate porosities, pore shapes, and pore sizes in advanced porous ceramics merely by measuring the ultrasonic delay time and pulse width. The extensive ultrasonic measurements and image microanalyses were conducted in advanced porous alumina, sialon, and zirconia with different porosities. A universal equation was established for porous ceramics, clarifying the intrinsic relationships between ultrasonic characteristics (propagation time and pulse width) and pore distribution (porosity, pore shape, and pore size). The critical volume fraction porosity were estimated separately as approximately 0.06, 0.11, and 0.10 in these ceramics using image microanalysis techniques, at which the transition from the continuous to discontinuous pore phase takes place during sintering. An excellent agreement of two useful corollaries with the data on the above nondestructive and destructive examinations validates the quantitative applicability of the probabilistic theory to pore characterization of advanced ceramics, metals, and their combinations. (C) 1999 American Institute of Physics. [S0021-8979(99)03219-3].