Compaction curves in each stage were studied by direct observation of internal structure of the compact and the characteristics of spray-dried granules. Three kinds of alumina granules were fabricated by spray drying with changing slurry conditions. The granules were characterized on the shape, the compression strength and the relative density. The compaction curves in uni-axial pressing were measured by using a compression testing machine from 0 to 100 MPa. The internal structures of granules compacts pressed at various pressures were observed using a laser scanning fluorescent microscope. Observation and characteristics of granules indicated that granules started deformation at a yield stress in compaction curves and those granules fractured at the stress of granule strength. The relative density of granules compact did not correspond with the relative density of granules. The result suggests that the rearrangement on particles in the granule start before the finishing granule deformation.
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