Sintering of zirconia coated hydroxyapatite particles

The surface of relatively large-sized spherical fine HAP particles (D-m=9.32 mu m) were coated with small-sized fine PSZ particles (D-m=0.12 mu m) by a dry impact blending method. The surface of the HAP particles were found to be coated completely with the fine PSZ particles, The HAP/PSZ composite particles were sintered. The fracture toughness, microstructure and crystal phases of the sintered body were investigated. The fracture toughness of the sintered body consisting of 100% HAP was 1.1 MPa . m(1/2), although those of the sintered bodies with HAP/PSZ weight ratios of 10/2, 10/5 and 10/10 (made by hot pressing) were 1.8, 1.8 and 2.8 MPa . m(1/2), respectively, Direct particle connections were seldom observed, electron-microscopically, among the fine HAP particles in the sintered body of the composite particles. The sintered body comprises a three-dimensional and continuously-reticulate PSZ phase in which the spherical fine HAP particles are scattered. X-ray diffractometry revealed that the sintered bodies with HAP/PSZ molar ratios of 10/2, 10/5 and 10/10 made by the hot pressing consisted of HAP and PSZ (tetragonal zirconia) only, It could be understood, from these observations, that toughening by PSZ still remain effective in the sintered body of the composite particles.