electrostatic stabilization

One way to keep particles from clumping is to make them all carry the same electric charge, so they shove each other away like the same poles of two magnets. Rub a balloon on your hair and the strands, now all charged alike, fan apart; electrostatic stabilization does the same trick to a slurry. Give every ceramic particle a surface charge of the same sign, and the particles repel one another, staying spread out in the liquid instead of collapsing together under the van der Waals attraction.

Where does the charge come from? An oxide particle in water grows surface hydroxyl (-OH) groups, and depending on the pH these give up or grab a proton: in acid the surface goes positive (picking up H+), in base it goes negative (losing H+). Around each charged particle the water gathers a matching cloud of oppositely charged ions — the electric double layer. When two particles approach, their two ion clouds overlap and push back, and that overlap repulsion is the stabilizing force. Its reach is set by the Debye length: in pure water or with little dissolved salt the cloud is thick (say 10 nm) and the repulsion reaches far; add salt and the cloud is squeezed thin (under 1 nm), the repulsion collapses, and the particles fall together. So electrostatic stabilization is strongest at a pH well away from the isoelectric point and at low salt content.

In practice you tune it with pH and with dispersants that charge the surface. An alumina slip cast near pH 4, far below alumina's isoelectric point of about pH 9, carries a strong positive charge and disperses beautifully; the same slip near pH 9 has almost no charge and flocculates. The catch is that electrostatic stabilization is fragile: it fails at high ionic strength, near the isoelectric point, and in non-aqueous solvents where charges barely form. That fragility is exactly why steric stabilization (polymer coats) is often used instead of, or together with, charge — the combination is called electrosteric stabilization.