Characterization of porous silica gels prepared via the sol-gel process by29Si CP/MAS solid-state NMR spectroscopy
- 1 November 1990
- journal article
- research article
- Published by Taylor & Francis in Molecular Physics
- Vol. 71 (4) , 769-780
- https://doi.org/10.1080/00268979000102101
Abstract
The structure of silica gels prepared by acid or basic hydrolysis of Si(OC2H5)4 has been investigated by 29Si MAS-NMR. The influence of hydrolysis conditions (pH) and drying temperature is studied by determining the percentages of SiO4 local coordination units with two, three and four covalent bonds to neighbouring silica centres. Further information is obtained by monitoring the 1H-29Si crosspolarization dynamics; an oscillatory component of the magnetization transfer is observed. The cross-relaxation rate 1/T SiH and the spin-diffusion rate 1/T HH are discussed in terms of current models of the sol-gel process, in which the structure of the resulting gel is influenced by the kinetics of both the hydrolysis and subsequent condensation reactions.Keywords
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