Controlled colloid formation

Much progress has recently been made in the preparation of uniform colloidal particles of internally mixed composition, that is, consisting of more than one cation, either in exact stoichiometric or variable molar ratios. In the latter case the surface and the bulk properties may differ significantly. Of practical importance is the introduction of techniques, such as the controlled double jet precipitation, which can yield well defined powder dispersions in large quantities. The availability of these powders has made it possible to quantify optics of uniform pigments and to develop a better understanding of the properties of ceramic materials produced from powders of monodispersed particles. Finally, based on many experimental results, the concepts regarding the formation of monodispersed colloids by precipitation have been revised. Much evidence has been offered showing that the processes involved are more complex than originally assumed. An aggregation stage that consists of primary particles, rather than diffusional growth, appears to dominate in the generation of most uniform colloids.