Influence of MgO-Al2O3 hollow sphere content on the microstructure and mechanical properties of calcium hexaluminate porous ceramics

Abstract

ABSTRACT Calcium hexaluminate (CA6) porous ceramics were prepared by foaming and pore-forming agent methods, with Al2O3 and calcium aluminate cement (CAC) as raw materials and magnesium aluminum spinel hollow spheres (MASHSs) as pore-forming agent. The effects of the amount of magnesium aluminum spinel hollow sphere on the phase composition, bulk density, apparent porosity, flexural strength, microstructure, and thermal conductivity of CA6-based porous ceramics were systematically studied. The pores of such porous ceramics are mainly formed by the enhanced amount of MASHSs and the generation of CA6 phase. The results demonstrate that with the elevation of MASHSs content, the microstructure of the samples transforms from a uniform distribution of closed pores to an interconnected micro-pore arrangement. Notably, the fracture paths transition from cohesive to interfacial interactions between MASHSs. This intricate interplay culminates in a remarkable outcome – our ceramics exhibit thermal conductivities ranging from 0.210 to 0.451 W/(m/k), an augmented gas permeability of 25.96 × 10−11m2, and exceptional compressive strengths reaching up to 22.3 MPa. Overall, this study provides insights into the influence of MASHSs content on the microstructure and thermal-mechanical properties of porous materials, which may contribute to the development of advanced ceramic materials with tailored properties.