| Surface forces of colloidal particles play critical roles in the macroscopic behavior of particulate systems such as dispersion and coagulation, adhesion and coating, and the rheological behavior of ceramic slurries. As particle size is decreased from micrometer to nanometer range, surface forces are increasingly important. Polyelectrolytes are the chemical additives commonly used to efficiently control the stabilization of the colloidal system. Their conformations on the solid surfaces as well as the interactions between the adsorbed polyelectrolytes are important issues in colloidal processing. Most experimental and theoretical approaches to the surface forces are based on particle sizes in the micrometer range. However, nanoparticles at close proximity or high solids loading are expected to show different behavior than what can be estimated from conventional theories such as continuum or mean field theories.; My study examined the effect of pH, ionic strength, and molecular weight of the polyelectrolytes on the surface forces of colloidal particles by the interplay with the adsorption, turbidity, and direct surface force measurement in terms of the conformation on the solid surfaces. The colloid probe technique based on atomic force microscopy (AFM) is well established for micron size particles; and could be extended for nanosize particles by using carbon nanotubes as proximal probes. Nanotubes with their high aspect ratio avoid the contribution from cone shapes that happens with AFM tips. The difference in particle size significantly influences surface forces for sterically dispersed colloidal systems. |
