Fabrication and analysis of lightweight magnesia refractories with micro-nanometer double pore size structure

Abstract

To effectively reduce the heat loss of high-temperature thermal equipment, it has become a mainstream trend to develop lightweight refractories with low thermal conductivity and high strength as thermal insulation linings. The pore size of traditional lightweight refractories is dominated by micron-level pores. In this study, a lightweight magnesia refractory with a double pore size (micron-nanometer) was prepared by the sol impregnation process. The formation mechanism of the nano pore was proposed, and the influence of sintering temperature on the microstructure, sintering performance, and thermal physics property of the sintered samples was investigated. The results showed that the bulk density of the lightweight magnesia refractories with nano pores (500–800 nm) increased from 1.26 to 1.94 g/cm³, the apparent porosity from 64.73 to 43.86%, and the cold crushing strength increased from 4.9 to 21.4 MPa during the increasing the sintering temperature from 1300 to 1600 °C. The average thermal conductivity of the sample at 1300 °C was 0.438W·m⁻¹·K⁻¹. The nano-MgO increased the migration distance with the periclase particles, and the number of nano pores was increased. In addition, the surface stress of the magnesia sol increased the speed of boundary migration and closed the pores before they were eliminated, and the formation of intercrystalline nano pores. The presence of nano-MgO can refine the pores, so that lightweight magnesia has lower thermal conductivity and excellent strength.