Diffusion of polymeric binder in alumina powder compact in a low PH range

摘要

In our recent paper [1-4], segregation of binder during the drying process of slurry is found to be one of the major origins of processing defects in ceramics. Several parameters, such as temperature, specimen size, solution volume and specimen porosity, are suggested to affect the segregation. Diffusion of binder is also found to play an important role in segregation. It can reduce segregation, since it counteracts the flow of binder with solvent. Although a systematic detailed understanding of binder diffusion is very important, direct determination of binder diffusion in ceramic slurry seems to be very difficult. To obtain relevant information on the diffusion of binder in a ceramic slurry, this paper presents results of the diffusion of polyvinyl alcohol (PVA) in aqueous phase in pores between powder particles in alumina compact for pH of PVA solution from 1.65 to 5.40. Under these conditions the adsorption of PVA on the alumina surface, which may affect the results reported in the earlier paper, can be minimized.