Dirken, P.J. and Smith, M.E. and Whitfield, H.J. (1995) O-17 and SI-29 Solid- State NMR-Study of Atomic- Scale Structure in SOL-GEL-Prepared TIO2-SIO2 Materials. Journal of Physical Chemistry, 99 (1). pp. 395-401. ISSN 0022-3654.
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Solid state O-17 and Si-29 magic angle spinning (MAS) NMR spectroscopy has been applied to the study of the structure of three Ti-Si mixed oxides and their gel precursors. Gels were prepared by the hydrolysis of tetraethyl orthosilicate (TEOS) and titanium isopropoxide (Ti(OPrn)4). Both one-stage (addition of the Ti(OPrn)4 to the TEOS) and two-stage (partial hydrolysis of the TEOS before addition of the Ti(OPrn)4) procedures were used. Si-29 MAS NMR spectra hardly show any differences between the one- and two-stage gels. All consist of Q(2), Q(3), and Q(4) SiO4 species becoming Q(4) after heat treatment at 600 degrees C. This study shows that O-17 MAS NMR is a valuable tool in the characterization of amorphous oxides and that it is much more informative than Si-29 MAS NMR. O-17 MAS NMR shows that titanium is incorporated only as Ti-O-Si bonds in a two-stage gel, whilst samples that show phase separation alsb have Ti-O-Ti bonds. Ti-O-Si linkages persist until 600 degrees C and in conjunction with the Si-29 NMR data indicate that titanium enters the silica network. The assignment of the Ti-O-Si resonance is confirmed by studying the mineral fresnoite (Ba2TiSi2O8).
|Subjects:||Q Science > QD Chemistry|
|Divisions:||Faculties > Science Technology and Medical Studies > School of Engineering and Digital Arts|
|Depositing User:||P. Ogbuji|
|Date Deposited:||03 Jun 2009 08:39|
|Last Modified:||04 May 2012 14:29|
|Resource URI:||http://kar.kent.ac.uk/id/eprint/19492 (The current URI for this page, for reference purposes)|
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