Abstract
To obtain concentrated silicon nitride slurries appropriate for a vibro-casting (solid casting) to fabricate large scale products such as valve cocks or refractory blocks used in glass industry, the influence of pH on deflocculation/flocculation for silicon nitride fine powder/water suspensions was investigated. The viscosity of the concentrated slurries with various pH values was measured by means of pulling up ball method under vibration.
The silicon nitride fine powder-water suspensions were found to be deflocculated in the range of 2-4 and 10-12 of pH, while they were flocculated primarily between 5 and 9 of pH, and secondarily below 2 or over 13 of pH.
The apparent viscosity of the concentrated and deflocculated silicon nitride slurries under vibration was lower than that of the flocculated slurries. The apparent viscosity of both deflocculated and flocculated silicon nitride slurries decreased with increasing frequency and amplitude of vibration. However, feed of vibration with high frequency and large amplitude to silicon nitride slurries raised their apparent viscosity instead.
