Processing, microstructure and toughness of Al2O3 platelet-reinforced hydroxyapatite

Experimental design has been used to analyse the processing of alumina platelet-reinforced hydroxyapatite ceramics. Composite materials were developed by slip casting and hot pressing. The most appropriate slurry composition allowing production of homogeneous composites was 65 wt% of powder and 3.1 wt% of deflocculant. HAP slurries containing up to 20 vol% of platelets had a quasi-Newtonian behaviour and a shear thinning flow was found at 30 vol% of alumina. A preferred orientation of platelets within the matrix was observed which led to anisotropic mechanical characteristics. Platelet incorporation induced strong toughening of the matrix. In comparison with the monolithic HAP (K-1C perpendicular to = 0.75 (+/- 0.15) MPa root m; K-1C// = 0.65 (+/- 0.20) MPa root m), the toughness increased tip to 20 vol% of alumina content and reached maximum values of K-1C perpendicular to = 2.95 (+/- 0.45) MPa root m and K-1C// = 1.95 (+/- 0.35) MPa root m. (C) 1997 Elsevier Science Limited.