Effects of solution on apatite formation on substrate in biomimetic process

An alumina substrate forms a dense and uniform layer of bone-like apatite on it, when it is soaked in a simulated body fluid, provided that it is faced to a glass of composition, MgO 4.6, CaO 44.7, SiO₂ 34.0, P₂O₅ 16.2 and CaF₂ 0.5 mass%, placed at a distance of 0.2 mm. Effect of the ion concentrations, pH and temperatures of the fluid on the apatite formation on the substrate were investigated. The bone-like carbonate apatite was formed even in fluids lacking in calcium or phosphate ion, since those ions and carbonate ions are supplied from the glass and the surrounding fluids, respectively. An apatite was formed in fluids with pH 6.53 to 7.48 but not in those with pH less than 5.00, because the apatite is stable only in neutral to basic environment. Apatite formed in fluids at 30 to 60°C but not below 20°C, since only a small amount of silicate ions is released from the glass at lower temperatures.