Granulation process can be realised by dry or wet methods. Dry granulation is preferred when the product is sensitive to water. Extruders, tumbling beds etc. can be used for dry granulation. In wet granulation, a binder solution in liquid form is used to facilitate the agglomeration process. Spray drying is widely used in the advanced ceramic industry to improve the flowability of fine powders. Bertrand, studied to determine the characteristicsn of spray-dried granules prepared from yttria doped zirconia slurries . Bala showed two different ways, spray drying and spray freeze drying, to yield flowable, full granules from nanopowders based on yttria stabilized zirconia. Bertrand explained the properties of ceramic coatings performed using spray drying and used polyvnyl alcohol as a binder in his experiments.
The objective of this study was to obtain granulated magnesiadoped monoclinic zirconia powder. The properties of the refractory produced from these powders were assessed and compared to the commercial refractory nozzles based on zirconia. Flow properties,compressibility and powder morphology were characterized to investigate the suitability of granulated powders for industrial die-pressing.Flow properties and compressibility were identified with “Tapping Test” and “Hall Funnel” method. The flowability and compressibility were characterized by Carr’s compressibility index which was calculated after measuring tap density by Autotap. Comparing the initial (loose) powder volume with the final (tapped) volüme, the flowability of the powder can be predicted. This comparison is normally performed by calculating the ratio of the volumes (Hausner) or the change in volume as a percentage of the initial volume.
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