Aqueous processing of carbothermally prepared Ca- #alpha#-SiAlON and #beta#-SiAlON powders: powder and suspension characterisation

摘要

In order to control and understand the behaviourof aqueous suspension of carbothermally prepared Ca-#alpha#-SiAlON and #beta#-SiAlON powders, to be processed by slipcasting, different Suspension properties were determined viz.zeta potential, zero ESA signal, ViScosity, sediment volume,floc size, in combination with the powder properties. Thepowders showed similar suspension behaviour as a function ofpH (viscosity, sedimentation, isoelectric points) suggestingsimilar surface characteristics probably due to surfaceoxsidation after heating in air to remove residual carbon and/oradsorption of the deflocculant. The best deflocculation wasfound at pH 10-11 where water Suspensions of both powderswith Dolapix as a deflocculant separately investigated showedthe lowest viscosities (below 10 mPa.s), the lowest sedimentvolumes, and the zeta potentials have the highest absolute values.Visocsity and zeta potential measurements were found to be fasttechniques providing the most useful and complete informationof slip behaviour allowing a good choice of optimum suspension parameters.