Effect of alumina sol on the preparation of magnesia-alumina spinel foam ceramics by foaming-sol method

In this work, magnesia-alumina spinel foam ceramics were prepared by foaming-sol method using magnesia alumina spinel as raw material, anionic surfactant potassium oleate (PO) as foaming agent, and alumina sol as curing agent. The curing mechanism and the effect of alumina sol content on the stability of foam slurry and the properties of foam ceramics were investigated. In the foam slurry, the alumina sol can react with PO, so magnesia-alumina spinel can be fixed in the foam structure through the gel network to improve the stability of the foam slurry. The gelation process reduces the viscosity of the foam slurry. The pores of magnesia-alumina spinel foam ceramics sintered at 1500°C are mostly closed pores and the average pore was 29.7–42.1 µm. With the increase of alumina sol content, the bulk density of magnesia-alumina spinel foam ceramics increased from 1.3 to 1.9 g/cm³, the cold compressive strength from 8.8 to 22.7 MPa, and the thermal conductivity from .417 to .806 W·m⁻¹·K⁻¹(350°C).