Development of Near Net Shape Forming Processes of Ceramic Parts by Colloidal Processing
Techniques for producing near net shape ceramic components using aqueous forming processes are reviewed. Particular focus is on three dimensional, complex shape forming by gel casting and thin film forming by tape casting. Recent progress has been made in formulations that rely on dispersion of submicron ceramic particles in aqueous solutions containing polymers such as chitosan or poly vinyl alcohol and a temperature activated crosslinking agent (DHF, 2,5-dimethoxy- 2,5-dihydrofuran). These formulations can be produced to have low viscosity so that they can either be poured or injected into complex shape molds or cast into tapes. After casting, the suspension is heated to about 70 oC to activate the crosslinking agent. During crosslinking of the polymer, the rheological and mechanical behavior of the suspension is changed from liquid-like to solid-like. This allows the complex shaped bodies to be removed from the mold, dried and sintered. The strengthening of the cast tape due to crosslinking the polymer allows it to be dried without cracking. Rheological and mechanical behaviour, green and fired densities as well as examples of formed components will be presented. The green bodies can be readily machined with common high speed tool steel tools.
G. V. Franks et al., "Development of Near Net Shape Forming Processes of Ceramic Parts by Colloidal Processing", Advances in Science and Technology, Vol. 45, pp. 374-381, 2006