Fabrication of mullite fiber porous ceramics with even structures by filtration freeze-drying

Abstract

In this study, mullite fibrous porous ceramics (MFPCs) were fabricated by freeze-drying wetted bodies formed using vacuum filtration. The effects of freezing temperatures on the microstructure and mechanical properties were investigated. The investigations revealed that freeze-drying could effectively stop silica sol migration and obtain a uniform porous ceramic microstructure in which the binder covered the fiber surfaces and bonded the fibers at nodes. Owing to the homogeneous microstructure, the compressive strength of the obtained MFPCs with open porosity of 85.4% was more than 2.0 MPa, and there were two elastic regimes and one plastic regime in the stress–strain curve of the MFPCs, moreover, which revealed that the MFPCs fractured step by step under compression. In addition, the freezing temperatures affected the properties of the MFPCs because of the formation of plates derived from the binder.