Freeze casting of composite system with stable fiber network and movable particles

Freeze casting was employed to fabricate alumina fiber-based porous ceramics. The binder particles were rejected by ice crystals from the gaps of the network to fibers and bonded them to obtain strong and light network. The effects of fiber character, cooling temperature and slurry viscosity on the structure formation were investigated. The structure and properties of the fibrous porous ceramics were determined by two factors: the fiber network and the dispersion of binders. The cooling temperature and slurry viscosity affected the dispersion of the particles rejected by the solidification front while the fiber length affected the fiber network. The material with optimal properties was obtained with 5 wt% PVA, 5 wt% silica sol and 1 vol% alumina fibers when freezing at −20 °C. The bulk density was 0.199 g/cm3 and the specific strength was 3.860 N m/kg.