Coagulation of mixed organic systems and alumina particles for paste production

Pastes of alumina with plastic properties were prepared by direct coagulation casting (DCC) of concentrated suspensions (≥50 vol%). Two polyelectrolytes were used to produce mixed systems of organic and mineral particles. An anionic polymer, bearing both sulfonate and carboxylate functions, was used to disperse efficiently alumina powder in water. A cationic polymer, the chitosan (CT), which complexes with the anionic one was added into the stable suspension to form an organic network dispersed into the ceramic matrix. The sequence of addition of the chitosan in the suspension appears to be a significant parameter in order to optimise the suspension formulation. After in situ coagulation, cylinders were extruded.