In-Situ Fabrication of TCP/Al2O3 and Fluorapatite/Al2O3 Composites by Normal Sintering of Hydroxyapatite and Al2O3 Powder Mixtures

A powder mixture of 70 wt% Al2O3 and 30 wt% hydroxyapatite (HA) is sintered at 1300 degrees C or 1350 degrees C for 2 h at normal pressure. An MgF2-added composition to make HA into fluorapatite (FA) is also prepared for comparison. The samples without MgF2 show alpha & beta-tricalcium phosphates (TCPs) and Al2O3 phases with no HA at either of the sintering temperatures. In the case of 1,350 degrees C, a CaAl4O7 phase is also found. Densification values are 69 and 78 %, and strengths are 156 and 104 MPa for 1,300 and 1,350 degrees C, respectively. Because the decomposition of HA produces a H2O vapor, fewer large pores of 5-6 mu m form at 1,300 degrees C. The MgF2-added samples show FA and Al2O3 phases with no TCP Densification values are 79 and 87 %, and strengths are 104 and 143 MPa for 1,300 and 1,350 degrees C, respectively. No large pores are observed, and the grain size of FA (1-2 mu m) is bigger than that of TCP (0.7 mu m >=) in the samples without MgF2. The resulting TCP/Al2O3 nd FA/Al2O3 composites fabricated in situ exhibit strengths 6-10 times higher than monolithic TCP and HA.