17O Solution NMR Characterization of the Preparation of Sol−Gel Derived SiO2/TiO2 and SiO2/ZrO2 Glasses

Autor:	Florence Babonneau, Laurent Delattre
Rok vydání:	1997
Předmět:	Silanol chemistry.chemical_compound Zirconium chemistry General Chemical Engineering Alkoxide Inorganic chemistry Materials Chemistry chemistry.chemical_element Cleavage (crystal) General Chemistry Titanium Sol-gel
Zdroj:	Chemistry of Materials. 9:2385-2394
ISSN:	1520-5002 0897-4756
DOI:	10.1021/cm970372f
Popis:	17O nuclear magnetic resonance was used to investigate the classical two-step procedure for the preparation of sol−gel derived SiO2−TiO2 or SiO2−ZrO2 glasses. The formation of significant amount of Si−O−M bonds (M = Ti, Zr), resulting from the reaction of silanol groups with M−OR groups, was clearly demonstrated and seems to be kinetically favored when titanium (or zirconium) alkoxide is added to a prehydrolyzed solution of tetraethoxysilane. However, under the chosen experimental conditions, the as-formed oligomeric species are unstable, leading to a partial cleavage of the Si−O−Ti bonds; this phenomenon was not observed for the SiO2−ZrO2 system. Two approaches have been investigated to prevent such evolution: postaddition of water to promote condensation of the highly reactive Ti−OR groups or use of chemical modifiers to slow the reactivity of the titanium (or zirconium) alkoxide.
Databáze:	OpenAIRE
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