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

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, φ max , of the coated suspensions occurred at around pH ∼ 4.0 and increased with increasing coating thickness from under φ max = 25 vol% with 1 wt% boehmite to above φ max = 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, φ max .