Acicular particle orientation in a shear-centrifuge filter

Abstract

Acicular particles of potassium hexatitanate (K 2Ti 6O 13), 5 to 40 μm long with an aspect ratio of between 10 and 100, were dispersed in aqueous solutions of poly(vinyl alcohol) (PVA). The slurries were cast by using a shear-centrifuge filter (SCF) with a cylindrical stator, to obtain a green sheet with a preferred orientation of the particles. The green sheet obtained by SCF from a slurry with a solid volume fraction of 0.005 in a 1 wt.% PVA solution showed a degree of orientation of 73%. A two-step process with a low, initial shear rate followed by a higher one brought about better orientation. The importance of controlling the balance of the rate of shear and the rate of filtration was discussed.