INTERACTION OF KINETICS GOVERNING THE PRECIPITATION OF NANOPARTICLES

摘要

When precipitation is envisaged as a production process for nanoparticles, all influencing parameters have to be set with respect to all kinetics of the ruling effects in order to meet the required characteristics of the product. Although much is known about the several decisive effects, such as thermodynamically driven nucleation, crystal growth, polymorphism and agglomeration, the attempt to give a comprehensive description of the entire process starting from those single models often fails. The study presented here is an attempt to enhance this understanding of the interaction of the single kinetics mainly through respecting the influence of the surface properties of the precipitates. A physical model is introduced which relates changes in the interfacial tension of the crystals to the excess concentration of lattice ions at the surface. This excess is shown to result from a variation of the molar ratio of the lattice ions in the mother liquor, a parameter often adjusted to control the colloidal stability of the precipitates. On the example of an experimental study on the precipitation of Boehmite (g-AlOOH) the improvement of the comprehensive description, when respecting the surface properties, is shown, focussing on the interaction of agglomeration and polymorphism. Good agreement is found between experimental results and theoretical predictions based on this introduced physical model.