An investigation on the properties of ZrO₂ suspensions

The preparation and properties of ZrO₂ suspensions consisting of 55wt% zirconia powder, ethanol, polyvinyl butyral (PVB) as the dispersant and binder were studied. The quantitative optimization of dispersant was investigated from the measurement of the viscosity and the final sedimentation volume fraction of suspension with different concentration of PVB as dispersant. The suspensions were prepared in two stages. First, the dispersant was added to the solvent followed by zirconia powder. This slurry was ball milled for 24 h in order to separate zirconia particles and to break up weak agglomerates. Then binders with different content were added to the above suspension and the resulting slurry was milled for 24 h. The results show that the zirconia powder in suspension with 0.7wt% PVB as dispersant can be dispersed well. For binder content lower than 6wt%, cracks are noticed during drying when the green coatings are handled. For binder content more than 6wt%, there are many air bubbles in suspension. The zirconia suspension with suitable viscosity and stability is obtained in ethanol with 0.7wt% PVB as dispersant and 6wt% PVB as binder.