Gelcasting of sol–gel derived mullite based on gelation of modified poly(isobutylene-alt-maleic anhydride)

Gelcasting is an attractive process of fabricating ceramics with complicated shapes. In the present work, modified poly(isobutylene-alt-maleic anhydride) (mPIAM), a low toxicity polymer, was used to form mullite green bodies. Poly(ethylene imine) (PEI) was used as a solidifying agent. The aqueous slurry containing 50 vol% mullite ceramic powders, 3 vol% mPIAM, and 0.15 vol% PEI was prepared for the gelcasting process, and the minimum viscosity of 50 vol% mullite slurries was obtained when 3.0 vol% monomer was added. The slurry was stable at room temperature but solidified after being heated at 60 °C for 25 min. The green body was dried at room temperature for 48 h, fired at 600 °C for 1 h, and pressureless sintered at 1500 °C for 3 h. Results showed that the produced green and sintered bodies both have homogenous structure. The relative density and flexural strength of the green body were 56.7%±0.8% and 12.5±0.6 MPa, respectively, while those for the sintered body were 96.7%±0.5% and 376±82 MPa, respectively.