Optimizing the Pore Structure and Properties of Alumina-Based Foamed Ceramics through Curing Condition Prioritization

Abstract

The alumina-based foamed ceramics were prepared using α-alumina powder as raw materials by direct-foaming method. Calcium aluminate cement (CAC) was chosen as a binder to accelerate the solidification of foamed suspensions, and the effect of curing temperature on the rheological properties of suspensions, phase composition, microstructure, pore characteristics, compressive strength and thermal conductivity of foamed ceramics was investigated. What’s more important, the thermal conductivity was analyzed using the Grey relational degree model to explore the effect of the pore characteristics on the thermal conductivity of foamed ceramics. The findings revealed that the higher curing temperature led to the increase in viscosity and stability of the foamed suspensions, as well as a faster hydration rate of CAC, which resulted in a reduction in the pore size of the fired ceramics from 312 μm to 160 μm and the thermal conductivity (1000 ºC) from 0.309 W/(m·K) to 0.248 W/(m·K). It is worth noting that as the curing temperature rose, the porosity of the ceramics increased while the compressive strength improved from 0.83 MPa to 1.26 MPa, due to the smaller pore size, the more uniform pore size distribution and more regular pore roundness. According to the Grey relational degree model, pores in the range of 250-300 μm had the most significant impact on the thermal conductivity of the foamed ceramics.