Synthesis and sintering of nanocrystalline hydroxyapatite powders by gelatin-based precipitation method

The effect of gelatin on the nucleation, growth of carbonated hydroxyapatite (CHAp) crystals and subsequent influence on the microstructure of the sintered body was investigated. Nanocrystalline powders of carbonated hydroxyapatite (CHAp) were prepared from calcium nitrate tetrahydrate Ca(NO3)2·4H2O and diammonium hydrogen phosphate ((NH4)2HPO4) in the presence of gelatin under aqueous solution of different concentrations. X-ray diffraction (XRD) results, combined with fourier transform-infrared spectroscopy (FTIR), indicate gelatin solution concentration being a predominant factor for inhibiting nucleation and growth that is believed to relate strongly to the interaction between Ca ions in the solution and Rsingle bond(COO)− ions of gelatin molecules. FTIR collected on the powder with 4 wt.% gelatin after heat-treatment at 900 °C for 2 h in air exhibits single phase of CHAp. Scanning electron microscopy (SEM) shows that the powder obtained after heat-treatment at 900 °C is composed of nanocrystalline (50–100 nm) CHAp particles, and that the subsequently sintered bodies is highly porous.