Cross-linked polyvinyl alcohol as a binder for gelcasting and green machining

Autores: Chabert, F.|Dunstan, D.E.|Franks, G.V.
Fuente: J. Am. Ceram. Soc.
91 (10), 3138-3146
2008

Submicrometer alumina suspensions, dispersed in aqueous acidic solutions of polyvinyl alcohol (PVA) and 2,5-dimethoxy-2,5-dihydrofuran, have been evaluated for suitability as a cross-linkable binder system for casting complex-shaped ceramic components. Suspensions of up to 50 vol% solids have rheological behavior, which is suitable for pouring and filling molds. Complex-shaped green bodies are then formed by heating the suspension in the mold for a period of time (typically 15?60 min) at moderate temperature (60°-80°C) to gel the suspension. High green densities (58%-62% of full density) can be obtained. The dried green bodies have strength in excess of 1 MPa and may be readily machined. No more than 1-3 wt% PVA per weight of alumina is necessary, ensuring burnout that minimizes generation of flaws. The ceramic components can be fired to >96% of full density when fired for 2 h at 1400°-1450°C. Cross-linkable PVA may receive more widespread acceptance in ceramic processing than previous gelcasting formulations because PVA is already a common processing additive.