Effect of silicon content on the surface morphology of silicon-substituted hydroxyapatite bio-ceramics treated by a hydrothermal vapor method

Silicon-substituted nano-hydroxyapatite powders with up to 4.0 wt% silicon were prepared by a hydrothermal method. X-ray fluorescence spectroscopy, X-ray diffraction, and transmission electron microscopy analyses revealed that some SiO44− substituted PO43− in apatite lattice, while other SiO44− functional groups remained in the mother liquid. The content of silicon influenced the thermal stability, density, and grain size of the hydroxyapatite bio-ceramic samples at elevated temperatures. For instance, the crystallinity declined and grain size decreased slightly with increasing silicon contents. Whisker-type particles with different diameters grew on the silicon-substituted hydroxyapatite bio-ceramic surface upon hydrothermal vapor post-synthesis treatment of the bio-ceramics.