From Zironyl Chloride to Zirconia Ceramics, a Plant Operation Perspective

The differences between two hydrous zirconium filter cakes manufactured at pH 3 and 12 were studied and further processing consistent with industrial procedures was undertaken. The loss on drying was found to be approximately 23% for both filter cakes, however for the loss on ignition the ph 3 sample was found to have a 12% higher loss at 33%. The specific surface area (SSA) was found to be 238 m2/g for the pH 3 sample and 312 m2/g for pH 12. The pH 12 sample showed a linear decrease of SSA with calcination temperature and both samples achieved the same SSA after 1000 oC. The pH 3 sample took 29 hours to attrition mill to a target D90 of less than 2 m, the pH 12 sample achievedthe same target in 26 hours. X-ray diffraction revealed that both samples had crystallite sizes in the order of 30 nm and greater than 90% monoclinic phase. Both samples achieved approximately 86% theoretical density when uniaxially pressed and sintered, corresponding with 20% linear shrinkage. The pH 3 sample had greater statistical variability in most results, indicating it would be harder to control. Differences in appearance when tape cast were also noted for the two powders