Chemical analysis of silica doped hydroxyapatite biomaterials consolidated by a spark plasma sintering method

Silica (SiO₂) and the silicate-based biomaterials play an important role due to their in vitro and in vivo biological response. The present study synthesized a novel nano-structured amorphous silica doped hydroxyapatite (HA) via an aqueous precipitation route. HA was prepared with 0, 1, 3 and 5 wt% silica, which are comparable to the measured silicon content of natural bone. After spray drying into micron sized powders, the silica doped HA (SiHA) powders were consolidated at 1000 °C with a dwell time of 3 min using a spark plasma sintering (SPS) technique. X-ray diffraction analysis showed a main apatite phase with minor secondary β-tricalcium phosphate (β-TCP) was observed in the as-consolidated SiHA compacts. Substitution of PO₄^{3 -} by SiO₄^{4 -} in the apatite structure resulting in a small increase in the lattice parameters in both a-axis and c-axis of the unit cell were identified by X-ray photoelectron spectrometer (XPS) analysis and Raman spectrometer investigation. The cell culture in vitro investigation demonstrated that the presence of silicon in the SPS consolidated compacts contributed to the relatively high cell proliferation ability when compared with phase pure HA.