Colloid and Interface Chemistry Aspects of Ceramics

摘要

The major goal of this project was to address the properties and interactions offine powders of interest in ceramics. In order to arrive at quantitative conclusions and assure reproducibility of data, the first requirement was to have well defined dispersions consisting of uniform particles of different chemical compositions (simple or mixed) and in different shapes. Thus, one part of the program has dealt with the synthesis of such 'monodispersed' powders. Specifically, we have produced colloidal particles of different metals, metal oxides, and silicon nitride. In addition, internally mixed particles of stoichiometrically defined metal ratios (such as metal niobates) and of variable composition have been obtained. Finally, coated particles of inorganic cores covered with shells of either different inorganic compounds or of polymers were prepared. All these systems were characterized in terms of their bulk and surface properties. In the other part of the program, we studied, theoretically and experimentally, interactions between unlike particles (i.e., the stability of mixed dispersions), in order to evaluate compaction and sintering effects of such powders. The rate of heterocoagulation was followed in aqueous dispersion of different combinations of particles and the obtained data were compared with expected values based on different theoretical models. The significant discrepancies between the experimentally evaluated and calculated stability ratios could be reconciled, if the surface charge segregation was taken into account. Adhesion of particles, Ceramic powders, Coated particles, Colloid particles, Composite particles, Heterocoagulation, Monodispersed colloids, Powders.