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Effects of Boehmite-Coating Thickness on the Consolidation and Rheological Properties of Boehmite-Coated SiC Suspensions
Journal article   Peer reviewed

Effects of Boehmite-Coating Thickness on the Consolidation and Rheological Properties of Boehmite-Coated SiC Suspensions

Chia-Yi Yang, Wan Y. Shih and Wei-Heng Shih
Journal of the American Ceramic Society, v 84(12), pp 2834-2840
Dec 2001
DOI: https://doi.org/10.1111/j.1151-2916.2001.tb01101.x

Abstract

boehmite rheology/rheometry silicon carbide
We examined the effect of the boehmite coating thickness on the rheology and consolidation of boehmite-coated SiC suspensions. The thickness of the boehmite coating on SiC was varied by adjusting the boehmite concentration relative to SiC. For boehmite concentrations less than 10 wt%, the coating thickness increased with increasing boehmite concentration. For boehmite concentrations higher than 10 wt%, the coating thickness saturated. Further increase in the boehmite concentration led to the presence of small boehmite particles in the suspensions. All boehmite-coated suspensions gelled near their isoelectric points and the storage moduli of the gels with respect to pH exhibited a maximum near the isoelectric points. Below 10 wt% boehmite, the suspensions had very few small boehmite particles. The maximum storage modulus, G′0,max, of the boehmite-coated SiC gel decreased with increasing coating thickness, t, as G′0,max∝t−2, in good agreement with our earlier theoretical prediction. Meanwhile, the maximum sedimentation densities, φmax, of the coated suspensions occurred at around pH ∼ 4.0 and increased with increasing coating thickness from under φmax= 25 vol% with 1 wt% boehmite to above φmax= 65 vol% with 10 wt% boehmite due to increased zeta potential with increasing coating thickness. Above 10 wt% boehmite, the excess boehmite particles in the suspension increased the maximum suspension storage modulus, G′0,max, and decreased the maximum sedimentation density, φmax.

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Materials Science, Ceramics
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