High-strength porous mullite ceramics fabricated from particle-stabilized foams via oppositely charged dispersants and surfactants

Abstract

Closed-cell ceramics have attracted broad attention in many areas such as thermal insulation and radomes due to their high strength, low density, and moisture isolation. In this paper, closed-cell mullite ceramics were prepared from particle-stabilized foams via oppositely charged dispersants and surfactants. Mullite particles were dispersed via an anionic dispersant and then hydrophobically modified via a cationic surfactant. The surfactant with long hydrocarbon chains made the particles very hydrophobic, which contributed to the gelation of the particle-stabilized foam. Finally, high-strength porous mullite ceramics with closed cells were obtained. Typically, a compressive strength up to 27.3 MPa was obtained for ceramics with 75% porosity. This is higher than those fabricated by other processes due to the fine and homogeneous cells of the ceramics. We close with a discussion on the effects of the dispersant and surfactant concentration on the porosity, microstructure, and compressive strength of the porous mullite ceramics.