Direct observation of non-uniform distribution of PVA binder in alumina green body
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To study the effect of binder distribution in a powder granule on the internal structure of the compacts, the internal structure of green bodies with various PVA contents was examined by a liquid immersion technique and SEM. By the liquid immersion technique, a dark three-dimensional network was found in the as-compacted green bodies, but disappeared after binder removal. This result shows that the structure corresponds to binder-rich surface layer of the spray-dried granule. Detailed examination on green bodies after the binder removal showed that the low density region was present at the boundaries of granules and was related to the binder-rich region. The voids between granules increase with increasing the PVA content.
KeywordsPolymer Alumina Surface Layer Internal Structure Direct Observation
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