2001 Volume 42 Issue 11 Pages 2392-2397
Calcium-deficient hydroxyapatite (DAp) having a rod-like or thin-blade-like shape was produced by hydrolysis of α-tricalcium phosphate (α-TCP) at different pH values. Mixed powder composed of 40 mass%DAp and 60 mass% stoichiometric hydroxyapatite (HAp) was suspended in an aqueous solution containing a small amount of dispersant by colloidal process. After dehydration, HAp-40 mass%DAp consolidated samples were sintered at 1473 K for 2 h. Rheological behaviour of the slurry, microstructure and bending strength of HAp-40 mass%DAp prepared by this process depended strongly on quantity of the dispersant. Good dispersion of HAp and DAp powders at an optimum quantityof the dispersant resulted in high relative density of HAp/DAp composites with homogeneous microstructure. DAp starting powder readily decomposed to α-TCP and HAp at 1473 K, while the formation of α-TCP phase took place less intensively in HAp-40 mass%DAp composites sintered at that temperature. In contrast to HAp/α-TCP composites, an interdiffusion of ions between HAp and DAp during sintering may result in the increase in the thermal stability of DAp. HAp-40 mass%DAp composites prepared by a suitable colloidal process exhibited higher bending strength than HAp-40 mass%α-TCP composites and stoichiometric HAp alone.