The structure of TiO₂–SiO₂ and CaO–SiO₂ sol-gel glasses from neutron diffraction and solid state NMR using isotopic enrichment of titanium, calcium and oxygen

Author： Pickup D. M. Sowrey F. E. Skipper L. J. Newport R. J. Gunawidjaja P. Drake K. O. Smith M. E. Saravanapavan P. Hench L. L.

Publisher： Society of Glass Technology

ISSN： 0031-9090

Source： Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B, Vol.46, Iss.4, 2005-08, pp. : 433-438

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Abstract

An advanced materials characterisation methodology has been used to examine systematically a range of sol-gel glass materials of contemporary interest. Neutron diffraction using ⁴⁶Ti and ⁴⁸Ti stable isotopes, and isotope-enriched ¹⁷O MAS NMR, have been used to characterise the structure of catalytically active (TiO₂)_x(SiO₂)_1−x sol-gel glass as a function of calcination temperature (T=250, 500 and 750°C). The results reveal directly two Ti–O distances in a homogeneous (TiO₂)_0·18(SiO₂)_0·82 sol-gel derived glass. The detailed nature of the Ti environment may be discerned from a combination of neutron scattering data with solid state NMR, including the possible presence of phase separation at the higher temperature. Neutron diffraction using ⁴⁴Ca, and isotope enriched ¹⁷O MAS NMR have also been used to study the detailed nature of the structure of CaO–SiO₂ bioactive sol-gel glasses. The results offer a direct observation of multiple Ca–O distances in this material, and pave the way to a fuller understanding of the role of Ca in its bioactivity. The results presented here are consistent with, but greatly extend our previous XRD, ¹⁷O and ²⁹Si MAS-NMR, XANES and EXAFS studies of these materials.