Si-substituted hydroxyapatite nanopowders: Synthesis, thermal stability and sinterability

Synthetic hydroxyapatites incorporating small amounts of Si have shown improved biological performances in terms of enhanced bone apposition, bone in-growth and cell-mediated degradation. aper reports a systematic investigation on Si-substituted hydroxyapatite (Si 1.40 wt%) nanopowders produced following two different conventional wet methodologies: (a) precipitation of Ca(NO3)2·4H2O and (b) titration of Ca(OH)2. The influence of the synthesis process on composition, thermal behaviour and sinterability of the resulting nanopowders is studied. s were characterised by electron microscopy, induced coupled plasma atomic emission spectroscopy, thermal analysis, infrared spectroscopy, N2 adsorption measurements, X-ray diffraction and dilatometry. Semicrystalline Si-substituted hydroxyapatite powders made up of needle-like nanoparticles were obtained, the specific surface area ranged between 84 and 110 m2/g. Pure and Si-substituted hydroxyapatite nanopowders derived from Ca(NO3)2·4H2O decomposed around 1000 °C. Si-substituted hydroxyapatite nanopowders obtained from Ca(OH)2 were thermally stable up to 1200 °C and showed a distinct decreased thermal stability with respect to the homologous pure sample. Si-substituted hydroxyapatites exhibited higher sintering temperature and increased total shrinkage with respect to pure powders. Nanostructured dense ceramics were obtained by sintering at 1100 °C Si-substituted hydroxyapatites derived from Ca(OH)2.