Dispersion and stability of colloidal boron carbide suspensions

The effects of several anionic, cationic and non-ionic polyelectrolyte dispersants on the stability and rheology of aqueous boron carbide (B4C) suspensions were investigated using zeta potential measurements, settling experiments, and rheological studies. Zeta potential measurements and settling experiments were useful to narrow down the best pH range for each dispersant while using minimal amounts of material. However, these techniques did not effectively predict which dispersants would ultimately be the most effective. Slurry milling for 2-4 h was essential to obtain stable homogeneous slurries (30-45 vol%), while more viscous pastes (50 vol%) would require longer milling times. The best concentration of each dispersant could be identified using rheological measurements. The viscosity of highly-loaded slurries containing the optimum concentration of each dispersant was compared, showing that cationic PEI 25 k was the most effective dispersing agent. The importance of average particle size and particle size dispersion was also demonstrated.