INFLUENCE OF THE DEBINDING METHOD ON THE MECHANICAL-PROPERTIES OF PLASTIC FORMED CERAMICS

A new method of extraction of organic additives, by a supercritical fl uid is presented. Flexural strengths and Weibull moduli of extrusion m olded alumina, debinded by classical pyrolysis and by supercritical CO 2 extraction are compared. Better mechanical properties are obtained a fter a short time (3 h) of supercritical treatment (sigma = 277 MPa, m = 13.7) than after 18 h of pyrolysis (sigma = 253 MPa, m = 12.4). The binder extraction from green pieces by supercritical fluids is limite d by two factors, solubility and diffusivity of organic compounds. The major factors causing defects in the pyrolytic binder removal, such a s binder redistribution in the liquid phase and the outward diffusion of degradation products, do not take place in the supercritical debind ing method.