Abstract
Alumina suspensions for extrusion were prepared by adding metylcellulose and glycerol to a system of water, ammonium polyacrylic acid, and alumina powder. The effect of the additives on the rheology of mixtures was evaluated. The mixtures which could be formed into a sheet of less than 100μm in thickness showed Bingham flow characteristics. As the flow characteristics of the mixture, an empirical equation, P/k=A+B ln R, was obtained, where P is the extrusion pressure for forming alumina sheets, k is the apparent yield stress of the mixture, A and B are constants, and R is the extrusion ratio. The effect of methylcellulose and glycerol on the particle packing and the flexibility of alumina green sheets was discussed. A dense, translucent, alumina sheet of 80μm thick was obtained after firing at 1400°C for 4h.
