Graded membrane supports produced by centrifugal casting of a slightly polydisperse suspension

Tubular structures of a continuous particle size gradient are formed if a hollow cylindrical mold filled with a suspension of dispersed powder with a size distribution is centrifuged around its center axis. The mean particle size in the final structure increases gradually with increasing radial coordinate. Because the bulk properties can be optimized simultaneously with the surface composition, this process has advantages for the production of porous tubular ceramic membrane supports in case subsequent membrane layers are coated on the inner surface of the support. Particle velocities and concentrations in the suspension, as well as the compact profile, are numerically analyzed for completely filled molds. Using the analysis the composition at each location in the compact can be predicted, which can be used to calculate the permeance (flux per unit pressure difference), as well as the particle composition of the inner and outer surfaces. (C) 2001 Elsevier Science Ltd. All rights reserved.