Characterisation of aqueous suspensions of fumed aluminium oxide in presence of two Dolapix dispersants
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The stability of a fumed aluminium oxide nano powder suspended in water has been assessed through measurement of zeta potential and streaming current, using the fact that the particles exhibit maximum repulsion at high magnitude of charge. Two commercial dispersants belonging to a Dolapix series have been tested. Dolapix CE 64 has shown a better deflocculating action than Dolapix A 88. The iso electric point of the powder suspension has been found close to pH 9. A notable shift in the pH of iso electric point when Dolapix CE 64 was present, indicating that the interaction between particles and dispersant has involved chemical sorption. It has been found out, that at the relative low solids loading studied and within the limits of the pH measurement accuracy, a dispersant supplied in dose levels from 12 to 24 mg/g, has confined the pH of iso electric point to a relatively narrow range. A capillary suction time technique has been tried for evaluation of suspension fluidity as function of dispersant concentration and pH. For the dispersant stabilised suspensions, a correlation between their capillary suction time and pH of iso electric point has been documented.
KeywordsZeta Potential Fumed Silica Volumetric Titration Powder Suspension Measure Particle Size Distribution
We thank the Degussa AG for the powder samples and Dr. W. Wiehe for the raster electron microscopy.
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