Densification behaviour of nanocrystalline hydroxyapatite bloceramics

The sinterability of nanocrystalline hydroxyapatite (HA) particles by microwave sintering was compared with conventional pressureless sintering. The results revealed that microwave heating was effective in producing a useful HA body in a very short sintering cycle without disrupting the HA phase stability. The maximum hardness of 7.21GPa and 6.38GPa was obtained ford HA sintered at 1050 degrees C by the conventional method and 1150 degrees C by microwave sintering, respectively. The maximum fracture toughness measured for the microwave-sintered and conventional-sintered HA was 1.45 MPam(1/2) at 1050 degrees C and 1.22 MPam(1/2) at 1000 degrees C, respectively. Although the relative density of microwave -sintered HA was slightly lower than the conventional - sintered HA throughout the sintering regime employed, taking into account of the heating and soaking periods, the time taken by microwave sintering to achieve a relative density of 96.5% was about 3% of the time consumed for samples sintered by the conventional heating. Microwave heating was found to be an effective technique to produce a useful HA body for clinical applications without causing grain coarsening. (c) 2007 Elsevier B.V. All rights reserved.