Synthesis of mesoporous zirconium titanates using alkycarboxylate surfactants and their transformation to dense ceramics
Mesoporous zirconium titanates with Ti/Zr ratios of two have been prepared through the controlled hydrolysis of mixtures of zirconium and titanium alkoxides and long chain carboxylates (lauric, palmitic or stearic acids) in the absence of solvent. X-ray diffraction, transmission electron microscopy, and gas adsorption measurements indicate that the zirconium titanate mesophases consist of a disordered arrangement of uniform pores. The average pore diameter obtained depends on the carboxylate chain length. These zirconium titanate mesophases are stable to temperatures in excess of 600 C and possess a uniform distribution of Zr and Ti within the pore walls without the formation of extraneous phases as determined by XRD and energy dispersive X-ray analysis. The formation of the mesophase was also investigated by small angle X-ray scattering which shows the growth of fractal structures as a function of time. When impregnated with calcium ions the reactive mesoporous precursor can be converted to the dense ceramic, zirconolite, at temperatures as low as 900 C. The zirconolites formed using the present methods exhibit some compositional variability.