29Si and 31P MAS NMR spectra of 50CaO.50SiO2 glasses before and after soaking in a simulated body fluid(SBF) for various periods were measured and the chemical processes leading to apatite formation were derived. The network of 50CaO.50SiO2 glass consisted mainly of Q2 group. The fraction of Qn (n=2-4) group changes with immersion time in SBF. In the initial stage of apatite formation the Q2 group comprising the 50CaO.50SiO2 glass network dissolves or changes rapidly into the Q3 group by not only self condensation but also the polymerisation of the Q2 group with phosphate ions with a few P-OH bonds in the SBF. The phosphate silicate matrix layer and hydrated silica gel layer formed on the glass surface mainly consist of the Q3 group. These layers provide the active sites where phosphate ions can be adsorbed easily and apatite nuclei can form. The local structure around a P atom may be very similar to that of hydroxyapatite or CaHPO4.2H2O crystals.
|Physics and Chemistry of Glasses
|Published - 12月 1 1996
ASJC Scopus subject areas