THE EFFECT OF SILICON OXIDE ON THE PROPERTIES OF A HYDROXYAPATITE-MAGNESIUM OXIDE COMPOSITE

A hydroxyapatite-1wt%magnesium oxide (HA-1M) composite with and without a silicon oxide (SiO₂) additive at amounts of 0.25, 0.5, and 1.0 weight% was sintered between 1100 and 1300 °C to investigate the effect of the SiO₂additive on the sintering behaviour, mechanical properties and in vitro bioactivity of HA-1M. The HA-1M composite consists of HA, whitlockite and farringtonite. In the SiO₂ added samples, the phases of akermanite, clinopyroxene, merwinite, melilite and diopside were detected. These phases contributed to achieving better mechanical properties in the SiO₂ added samples than that of the HA-1M composite. The highest fracture toughness (1.47 ± 0.04 MPam1/2) and compression strength (183 ± 25.09 MPa) were achieved by sintering the HA-1M composite at 1200 °C. In the SiO2 added samples, the highest compression strength and fracture toughness were calculated as 201.53 ± 18.01 MPa and 1.78 ± 0.22 MPam1/2, respectively, which belongs to the HA-1M-0.5SiO₂ composite. With the addition of SiO₂ at an amount of 0.5wt%, the ratio of the apatite layer formed on the surface of the HA-1M composite increased.