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

Tubular structures of a continuous particle size gradient are formed if a h ollow 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 coor dinate. Because the bulk properties can be optimized simultaneously with th e surface composition, this process has advantages for the production of po rous tubular ceramic membrane supports in case subsequent membrane layers a re coated on the inner surface of the support. Particle velocities and conc entrations in the suspension, as well as the compact profile, are numerical ly analyzed for completely filled molds. Using the analysis the composition at each location in the compact can be predicted, which can be used to cal culate the permeance (flux per unit pressure difference), as well as the pa rticle composition of the inner and outer surfaces. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.