Sintering of bioceramics using a modified domestic microwave oven

In this study, hydoxyapatite (HA) prepared from calcined bovine bone was studied. Two methods were used for HA sintering: conventional sintering (CS) and microwave sintering (MS). HA was obtained by calcination of bovine bone at 800 A degrees C for 4 h followed by wet ball milling. Afterwards, the powder was compacted under 75 MPa and sintered for 2 h at different temperatures, from 1050 to 1200 A degrees C. It has been found that the bulk density of HA increases by increasing sintering temperature when both CS and MS were used. Nevertheless, at the same temperature and for a shorter time (15 min), the HA sintered by microwave were characterised by a density relatively higher than that of sintered by conventional furnace. For example, at 1100 A degrees C the bulk densities of samples using CS and MS were about 2.49 (for 120 min) and 2.93 (for 15 min) g/cm(3), respectively. Furthermore, a near theoretical density (98.6%) was obtained when HA samples were sintered at 1200 A degrees C for 15 min only but using the proposed MS, which was much higher than that (89.7%) of HA samples sintered at the same temperature for longer holding time (120 min). Besides this, the X-ray analyses have shown that heat-treatment, using these two processes, has lead to HA decomposition into tricalcium phosphate and/or tetracalcium phosphate.