Structural development of solution-derived, monodisperse powders studied using cryo-TEM.

Abstract

High quality advanced ceramic materials can be produced by using unagglomerated monodisperse powders for preparation of ceramic pre-forms. Stöber et al. first showed that monodisperse silica particles could be derived from silicon alkoxides, and Bugosh et al. demonstrated the control over particle size and mass fraction that could be obtained. Similarly, Barringer and Bowen produced titania colloids but without using a catalyst. In these preparation procedures, a solution of metal alkoxide monomers undergoes hydrolysis and condensation to form the particles. By the chemical processing of monodisperse powders, one can control the particle size and stabilization. In order to understand and control the influence of the processing conditions on the morphology of these particles, the growth mechanism needs to be understood. As yet, there are no widely accepted growth models for the various materials.Using cryo-microscopy, one can directly observe the development of these particles by freezing the reaction at various stages and observing the products at that time. A thin liquid film of solution is fast frozen, vitrifying the solvent and trapping the particles suspended in solution, thus avoiding potential artifacts, such as agglomeration, that can be caused by drying the sample.