Influence of bivalent ions on the dispersion and gelation of ceramics suspensions

We report on the dispersion and gelling mechanisms of Al₂O₃ and Si₃N₄ suspensions fabricated via gelcasting. These systems were prepared by introducing bivalent ions into a gelcasting system known as ISOBAM, a water-soluble copolymer of isobutylene and maleic anhydride. The addition of metal ions negatively affects viscosity, while the influence of bivalent ions on the storage modulus is closely related to the microscopic configuration of ISOBAM. This configuration is altered due to the competition between particles and metal ions in the suspension to adsorb ISOBAM. An increase in the ionic potential of metal ions accelerates the gelling rate of Al₂O₃ suspensions and increases the surface area of ISOBAM self-assembly around the particles, thereby extending the microscopic conformation. In Si₃N₄ suspensions, the surface area of ISOBAM around the particles initially decreases and then increases, primarily due to pH changes resulting from the hydrolysis of metal ions and Si₃N₄.