An investigation into the hydrolysis and condensation reactions of zirconium (IV) butoxides

The sol-gel process permits the careful control of the size and morphology of materials during the earliest stages of production (Hench and West, 1990). Some of the current applications are development of advanced materials for structural, electrical and optical purposes. One of the important methods of preparing these high-purity materials is the synthesis of metal oxide gels and particles from metal alkoxides. The hydrolysis and condensation reactions of the zirconium alkoxides are extremely vital to the sol-gel process, since the alkoxides react to form the respective oxide powders and gels. However, a rapid mixing technique must be used to study these reactions because they can be nearly completed within a few seconds. Monitoring these reactions within a millisecond time regime allows one to control the morphology, size, and uniformity of the resulting particles. Two instrumental analyses that can be combined with the rapid mixing technique are Fourier Transform Infrared Spectroscopy (FTIR) and small-angle X-ray scattering (SAXS). FTIR was used in studying soluble-species reaction kinetics. The aggregation kinetics of the polymeric clusters and particles forming in time were studied using the SAXS technique. Key parameters such as mixing time, base and water concentrations, alkoxide concentrations, and alkoxide-to-water ratios were fully investigated to control the powder synthesis. These experimental results can be used to verify and determine model parameters for reaction and aggregative kinetics.