Ceramics-Silikáty 51 (1) 1-8 (2007)

TEXTURAL AND STRUCTURAL PROPERTIES OF BIOACTIVE GLASSES IN THE SYSTEM CaO–SiO₂

N. J. Coleman, M. Bellantone, J. W. Nicholson, A. P. Mendham

Gel-derived CaO-SiO₂ binary glasses of CaO mole fractions 0.2, 0.3 and 0.4 have been prepared and characterised. Pore diameter, specific pore volume, skeletal density and porosity were found to increase with increasing CaO-content, whereas a concomitant decrease in specific surface area was observed. ²⁹Si NMR indicated that the 0.2 CaO mole fraction glass consisted of highly polymerized Q4 and Q3 silicate species, with some Q2 units. With increasing CaO mole fraction, these silicate species became progressively depolymerised such that isolated SiO4 tetrahedra were detected within the 0.4 CaO glass matrix. Unusually, the glasses retained a proportion of Q4 and Q3 species as the CaO mole fraction was increased. All glass formulations exhibited in vitro bioactivity. The rate of hydroxyapatite precipitation followed the order 0.2 CaO > 0.4 CaO > > 0.3 CaO, an effect that is attributed to differences in the rate of dissolution of calcium from these glasses. This, in turn, appears to be dependent upon the proportion of Ca²⁺ participating in the formation of the glassy network.

Keywords: Sol-gel, Bioactive, Mesoporous, Glass