General Introduction

Abstract

Sols and gels are two forms of matter that have been known to exist naturally for a long time. They include various materials such as ink, clays, and a number of other substances such as the eye vitrea, blood, serum, and milk [1]. Sols and gels have arose scientific interests for a long time. The oldest sols prepared in a laboratory were synthesized with gold by Faraday in 1853. They are still stable nowadays[2]. It was not until 1861 that Graham founded colloidal science. Since then the study of ceramic colloidal sols has been slowly progressing so that the manner in which the sols forms and their sensibility to a number of different factors are now starting to be understood. It is only since recently that we can control the size of particles with inorganic salts [2,3]. Similarly, it has been necessary to achieve a good understanding of the nature of sols and of the laws explaining their behaviors before synthesizing well-defined particle dispersions. A major contribution in the understanding of sols chemistry came from the DLVO or electrostatic theory. This theory was particularly the first one to distinguish a precipitate from a stable colloidal suspension.