Preparation and characterization of TiO2–SiO2 glass ceramics via the sol–gel process by adding organic additives

Abstract

This paper deals with the preparation of TiO2–SiO2 ceramics by using formamide, glycerol, or oxalic acid as drying control chemical additives (DCCAs) in order to improve the physical properties of the products, control the rates of hydrolysis and polycondensation, as well as the particle size homogeneity and porosity distribution. It was found that when using DCCAs, the gelation time was longer than without any additives. In acidic solution, the hydrolysis reaction is rapid, and the gelation tends to be slow; in an alkaline medium, the polycondensation of Si–OH and Ti–OH groups takes place much faster. The higher rate of nucleophilic substitution associated with the DCCAs leads to larger particles of the bulk ceramics.