Ultra-high porosity of open-cell alumina ceramic foams prepared by adding tiny amounts of γ-AlO(OH) sol

Abstract

A creative and environmentally friendly preparation of high-porosity open-cell ceramic foams was investigated. The samples were prepared from the α-Al2O3 slurry with 25 wt.% solid loading in which a tiny amount of boehmite (γ-AlO(OH)) sol was added for the formation of particle-stabilized foams without introducing any sacrificial phases. The volumetric shrinking of γ-AlO(OH) enables the formation of open-cell while avoiding the generation of polluting gases. The resulting alumina ceramic foams have a synergistic increase in porosity and compressive strength, reaching a compressive strength of 1.17MPa and an ultra-high porosity of 94.8%. This is due to the fact that the pore struts (connecting neighbouring cells) are almost defect-free, while the high sintering activity of γ-AlO(OH) promotes the sintering of ceramic phase and formation of alumina with small grains which has the strengthening effect on the obtained structures. By achieving open-cell, the heat conduction path increased, which reduces the thermal conductivity of the ceramic foam. This work provides an alternative and environmentally friendly new strategy for open-cell ceramics processing.

Keywords

• ceramic foams
• high porosity
• open-cell alumina structure
• γ-alo(oh) additive