Monolithic zirconia gels from metal—organic solutions

Abstract

It has recently been shown by Ganguli and Kundu [1] that amorphous and transparent coatings of pure ZrO 2 could be prepared by controlled hydrolysis of zirconium propoxide and subsequent polymerization by using a non-polar solvent like cyclohexane instead of the usual alcoholic solvents employed for preparing coatings and monoliths [2-7]. The non-polar, hydrophobic solvent was used to avoid precipitation caused by the high rate of hydrolysis of Zr(OC3H7)4. The present work is a continuation of the above study, leading to the preparation of pure, transparent and amorphous zirconia gels (including monoliths), using zirconium propoxide and cyclohexane. It was observed during this work that the rate of evolution of the volatiles from the gel-forming compositions could play a vital role in determining the nature of the product. This has also been systematically examined. Technical grade zirconium n-propoxide (Fluka) and Analar grade cyclohexane (BDH) were used for preparing the zirconia gels. The cyclohexane was thoroughly dried before use by repeated contact under stirring with activated silica gel and molecular sieve 4A. Solutions of the propoxide in cyclohexane (in the range 4 to 10 equivalent wt % ZrO2) were prepared in