SOLVENT DEBINDING KINETICS OF ALUMINA GREEN BODIES BY POWDER INJECTION-MOLDING

Solvent debinding of alumina green bodies shaped by powder injection molding is investigated. Debinding is carried out in normal hexane (n-C6), normal heptane (n-C7) and normal octane (n-C8), at 50, 60 and 80 degrees C. Wax is the major constituent being leached. A shrinking core is observed at the early stage of 50 degrees C solvent debinding. Debinding kinetics is adequately described by a single-parameter (effective diffusivity D-e) model except in the region of the core. The effective diffusivity decreases with the increase of carbon number of solvent from 5.2 x 10(-6) (n-C6) to 3.5 x 10(-6) cm(2)/s (n-C8) at 50 degrees C and from 6.2 x 10(-6) (n-C6) to 3.8 x 10(-6) cm(2)/s (n-C8) at 60 degrees C. For each solvent, the effective diffusivity is proportional to (leaching temperature/solvent viscosity). A core of clear edge not removed by solvent leaching could cause cracks in the subsequent processing steps. Cracks are observed around the edge of core after thermal debinding.