The zeta-potential and microstructure of ZrO_2 sol derived from a hydrolysis method

摘要

Powder and porous ceramics of ZvOj are useful for many industrial applications such as catalytic sup-ports and reaction-converters. Z1O2 sols are poten-tially useful for the fabrication of composite materials as well as the catalytic coating layers in exhaust-gas purifying devices. Among the many preparation methods of Zr(>2 powder and porous media, the hydrolysis technique of aqueous zirco-nium salts is advantageous for controlling the primary particle sizes and their aggregates in solution [1-8]. The aqueous sol formation from a zirconium salt is essentially dependent on the hydrolytic species and their polymerization in the solution [7, 8]. More practical fabrication techniques have been reported by several workers [1-6]. For a catalysis application, it is important to know the possibility of tailoring the pore-structure as deter-mined by the microstructure of primary particles and their agglomeration behaviour [9]. Also, knowledge of the surface structure and chemistry is required in order to design the catalytic activities of multi-component composite particles. We have previously examined the activity of pure Z1O2 and ZrO?-RO.v (R: rare earth metals) solid solutions as a catalytic support [10-14]. Although ZrO2 powders from hydrolysis have a large surface area, they are less active for carbon-monoxide oxidation as compared to rare-earth modified ZrC>2 prepared by the co-precipitation method. A better understanding of the hydrolysis process of Z1O2 sols may enhance their effectiveness in a variety of applications such as catalytic supports, absorbate layers, and precursor chemicals for advanced processing. Furthermore, it also serves as an interesting model system for studying dispersion-agglomeration processes in cera-mic fabrication. In this letter, we examine two important properties of ZvO2 sol: the zeta-potential and microstructure of the particle and/or aggregate using small-angle neutron scattering (SANS) and the Brunauer-Emmett-Teller (BET) technique.