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The rate of coagulation in systems of identical and unlike colloids in aqueous media has been studied by a simultaneous multi-angle static light scattering technique. The mixed dispersions consisted of polystyrene latex particles of different radii and of opposite sign of charge. A procedure based on the Rayleigh-Gans-Debye approximation permits one to estimate the absolute rate constant either for homo-or hetero-coagulation. The absolute coagulation rate constants were compared to those calculated theoretically, using the Smoluchowski theory. In homosystems, the fast coagulation rate corresponded to ca. 5540% of the Smoluchowski value. In the heterosystem, the coagulation rates exceeded the calculated values based on the diffusion-controlled process at a low ionic strength. An increase in the electrolyte content led to a decrease of the coagulation rate, which at high concentrations corresponded to ca. 85% of the Smoluchowski value.

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This study describes particle adhesion experiments carried out to elucidate interactions between particles in slurries used for polishing of wafers and disks. For this purpose the packed column technique was employed, which simulated chemical mechanical polishing of copper with silica and alumina, as well as of silicic oxide with ceria. The model systems consisted of uniform copper and glass beads as collectors, representing the wafers, and colloidal dispersions of silica, alumia, and silica coated with nanosize ceria, all of well-defined properties that are used as abrasives. It was shown that a strong correlation exists between deposition and detachment results of the adhesion studies and the polish rates measured using actual substrates with the same or similar slurries.

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