Evaluation of nanoparticle containing dispersions

摘要

The long-term stability of dispersions will be of great importance in a number of industries such as ceramic, microelectronic, paints and pigments. For instance, in microelectronics, suspensions with monodisperse spherical particles in the nanometer range ("slurries") were used in CMP (chemical mechanical polishing) process technology. The slurry must have the following possessions: ensure uniformly abrading free from defects, colloidal stability, and ease of use. In such "nanodisperse" systems the small size of the disperse phase is in a great contrast to the large surface/interface area. The dispersion stability is more difficult to realize and the interface properties dominate the properties of the whole system. The long term-stability can have different connotations to different applications. When applied to colloids, a stable colloidal system is one in which the particles resist flocculation or aggregation and exhibits a long shelf life. This will depend upon the balance of the repulsive and attractive forces that exist between particles as they approach one another. If all the particles have a mutual repulsion then the dispersion will remain stable. But, as we know, there are often differences in the performance of slurry, even with dispersions of the same origin. These differences, whose reasons are often unknown, can influence the production process in large extent. Therefore in this work we will describe different methods for slurry characterization. It should be demonstrated that only with the help of combination of different methods conclusions about the quality of slurry is possible.Influencing parameters of dispersion properties are determined by physical interaction forces which stabilize or destabilize such systems. One possible mechanism is the use of double layer repulsive forces described by DLVO-theory [1,2]. In this case the influence pH-value, electrolyte concentration and valence is important.