Aqueous processing of SiC green sheets II: Binder and plasticizer

Well-dispersed SiC slurries in the presence of binder and plasticizer were prepared and investigated in this series of work. In this part, poly(vinyl alcohol) (PVA) 1788 was investigated as a potential binder for aqueous tape casting process. The minimum amount of binder was determined through a primary calculation. Effects of the binder on SiC slurries properties were analyzed in term of zeta potential measurement and rheological test. Coupled with PEI as dispersant and glycerol as plasticizer, they lead to homogeneous systems which seem compatible. The suspensions (formulated with 47.9 wt% SiC powder, 1 wt% dispersant, 3.5 wt% binder, and 3.5 wt% plasticizer) exhibited a shear-thinning behavior with a very limited time-dependent character. After tape casting and drying process, the properties of green tapes were evaluated in term of solid content and gap height. The optimal solid content of SiC was found to be near 22.25 vol%, and the gap height, near 200 μm. The microstructure of green tape was characterized by TEM. Results showed that preparation of homogeneous green tapes with relative densities at about 51 vol% was feasible.