Effect of nanoparticulate boehmite sol as a dispersant for slurry compaction of alumina ceramics

This work reports the use of monohydroxy aluminium oxide particulate sol [boehmite, AlOOH], as a dispersing medium for slurry compaction of submicron-sized alumina powders. Nanoparticulate boehmite sol, at controlled pH conditions, resulted in homogeneously dispersed alumina suspension which could be compressed into a definite shape by applying simple pressure. The partially flocculated boehmite sol at pH 6.2 acts as good dispersant and resulted in alumina-boehmite solids lending > 80 wt.%. The alumina dispersed in boehmite sol containing 17.24 vol.% boehmite concentration showed maximum green and sintered density. The maximum theoretical green density was 63% and the maximum linear drying shrinkage was < 3%. The maximum theoretical sintered density was about 97% at 1450 degrees C. The slurry compaction resulted in high-density, fine-grained, sintered alumina having average grain size at about 2 mu m. The nanoparticulate boehmite sol was found to be a matrix compatible dispersant for alumina ceramics and yields higher solid loading and particle packing under slurry pressing. (C) 2000 Elsevier Science B.V. All rights reserved.