Effects of Al2O3, ZrO2, and TiO2 ceramic additives on the sintering and mechanical properties of natural hydroxyapatite

Abstract

Hydroxyapatite (HA) is considered as the most appropriate ceramic material for implantation due to its close chemical and crystallographic resemblance to mineral part of vertebrates‟ bone and tooth, excellent biocompatibility, and bioactivity. Application of HA is restricted because of its poor mechanical properties. The study conducted in this thesis aimed to improve the mechanical properties of natural HA by the addition of several ceramics including Al2O3, ZrO2, and TiO2, in order to be used as a biomaterial in load–bearing applications. HA was produced from bovine femoral bones via calcination, the calcinated bone pieces were ground in a mortar by hand to obtain HA powder. A set of mechanical grinding (ball milling) experiments were conducted to determine the most suitable grinding speed and grinding duration for production of fine HA powder with smallest particle size achievable. Selected ceramic materials were separately added to fine HA powder with different weight ratios. The produced mixtures were pressed in a steel mold by uniaxial and cold isostatic pressing (CIP), respectively to produce cylindrical green specimens. The pressed specimens were sintered at different temperatures to obtain compact, dense materials with desired microstructure and higher mechanical strength than that of pure HA. The microstructures of produced materials were observed using scanning electron microscope (SEM), microhardness of each specimen and compressive strength of the selected ones were measured and compared with each other according to different ceramic additives and sintering temperatures.