Sol-gel processing of bioactive glass powders

A series of glass powders in the CaO-P{dollar}sb2{dollar}O{dollar}sb5{dollar}-SiO{dollar}sb2{dollar} system were successfully produced by sol-gel processing, an alternative to the conventional melt processing of bioactive glass and glass-ceramics with remarkable advantages of high purity and high homogeneity as well as low processing temperature.; Characterization of gel-derived powders before and after in-vitro testing was conducted using FTIR reflection spectroscopy, X-ray diffraction analysis, inductively coupled plasma (ICP) analysis, thermal analysis and nitrogen absorption BET.; Most gel-derived powders before in-vitro testing were amorphous and porous with a large surface area, ranging from 200 to 650 m{dollar}sp2{dollar}/g. Surface area increased with increasing SiO{dollar}sb2{dollar} content (50 mol.% to 90 mol.%) in the compositions and could also be controlled by heat treatment temperature.; By defining bioactivity as the ability of materials to form a surface hydroxyapatite (HA) layer in a simulated body environment, the in-vitro tests indicated that all the gel-derived powders with different compositions were bioactive. Compositions with up to 70 mol.% SiO{dollar}sb2{dollar} showed higher rates of formation of HA in the tris-buffered in-vitro solutions than melt-derived Bioglasses{dollar}spcircler{dollar}. The bioactivity generally increased with decreasing SiO{dollar}sb2{dollar} content. However, gel-derived powders containing as high as 90 mol.% SiO{dollar}sb2{dollar} in composition still showed the formation of a hydroxyapatite surface layer within 7 days at 37{dollar}spcirc{dollar}C, whereas the SiO{dollar}sb2{dollar} a compositional boundary of bioactivity of conventional melt-derived bioactive glass and glass-ceramics never exceeds 60 mol.%. Thus, the SiO{dollar}sb2{dollar} compositional boundary for bioactivity is extended significantly from 60 mol.% up to 90 mol.% by using sol-gel technology.; The texture, especially the surface area, has an important role in developing the bioactive surface HA layer. The enhanced bioactivity and the extended compositional region of bioactivity appears to be due to the increased density of nucleation sites for crystallization of hydroxyapatite on the SiO{dollar}sb2{dollar}-rich surface of the sol-gel derived bioactive glass powders.