Preparation of calcium hexaluminate porous ceramics by novel pectin based gelcasting freeze-drying method

Abstract

High-purity calcium hexaluminate (CA6) porous ceramics have been prepared with novel pectin based gelcasting freeze-drying method. CaCO3 and Al2O3 were used as raw materials and ficus pumila pectin was used as gelling agent. Effects of solid content on properties of CA6 porous ceramics, such as phase composition, microstructural characteristics, apparent porosity, bulk density, compressive strength, and thermal conductivity have been investigated. Pores in CA6 ceramics are found to be mainly formed by water molecules sublimation during freeze-drying and organic decomposition processes. Moreover, freeze-drying method is shown to be beneficial to improve heat insulation performance of porous ceramics. As-prepared CA6 porous ceramics with different solid contents possess high apparent porosity of 66.4-75.1%, low bulk density of 0.90-1.20 g/cm3, low thermal conductivity of 0.227-0.360 W/(mK), and relatively high compressive strength of 0.71-2.06 MPa, which fully meet requirements for their functional and structural applications.