Hydrothermal calcification of bioglass film in CaHPO4 solutions

Abstract

Bioglass film was sol-gel coated on titanium substrate, followed by hydrothermal treatment in water, 2.5mM and 10mM CaHPO4 solutions, respectively. X-ray diffraction analysis reveals amorphous nature of the gel powder sintered at 610°C, but small diffraction peaks of Ca3SiO5 are also observed. The absorption bands of Si-O-Si bonds, PO4 and OH groups are present, while those of NO3 groups are absent in Fourier transform infrared spectrum of the sintered gel powder. Scanning electron microscopy observation shows that the surface of the sintered bioglass film is porous (pore size ~200nm), and nanocrystallites (width ~20nm, length ~200nm) are deposited on the samples hydrothermally treated in CaHPO4 solutions. Energy dispersive x-ray, x-ray photoelectron spectroscopy and x-ray diffraction analyses indicate that the nanocrystallites are composed of hydroxyapatite, which are formed through a dissolution-precipitation reaction. The formation of hydroxyapatite nanocrystallites at the film surface improves hydrophilicity of the coating samples. Potentiodynamic polarization test in the Ca-free Hank's solution demonstrates that the coating samples have better corrosion resistance than the polished one. The calcified titanium samples are expected to possess good biological properties.