Comparison of ZrO2-SiO2 sols synthesized by two methods: Preparation, stability and physical-chemical structure

摘要

In the present work, zirconium nitrate pentahydrate (Zr(NO3)(4)center dot 5H(2)O) was used as ZrO2 precursors. The ZrO2-SiO2 sols with the Zr/TEOS molar ratios (n(Zr)) ranging from 0 to 2.0 were synthesized by two different methods, which were called ZrO2-SiO2-1 and ZrO2-SiO2-2 sols, respectively. The Gibbs energies of activation for viscous flow (Delta G*) and reaction rate constants (k) of the sol system were calculated. The effects of n(Zr), Delta G* and k on the sol stability were investigated. The phase, chemical and pore structures of the two ZrO2-SiO2 materials calcined at 400 degrees C were investigated. The results show that, with the increase of n(Zr), the rho, eta and Delta G* values of the sol system increase, and the sol stability deteriorates. The ZrO2-SiO2-1 sol has a better stability than ZrO2-SiO2-2 sol. The Zr-O-Si bond was found in the ZrO2-SiO2-1 and ZrO2-SiO2-2 materials. The ZrO2-SiO2-2 material fired at 400 degrees C clearly showed sharp peaks corresponding to a crystalline tetragonal structure of zirconia, while ZrO2-SiO2-1 material didn't. The ZrO2-SiO2-2 material has a smaller pore size than ZrO2-SiO2-1 material. The result reveals that preparation method of sol plays an important role in the physicochemical properties of ZrO2-SiO2 sol.