Preparation and properties of porous MgO based ceramics from magnesite tailings and fused magnesia

Abstract

Porous MgO based ceramics have been widely used in some key industries due to their excellent performance. To investigate the feasibility of preparing porous magnesia ceramics using magnesite tailings as a magnesium source. Porous MgO based ceramics were prepared using magnesite tailings, fused magnesia as main raw materials and soluble starch as pore-forming agent. The starting materials were mixed in different ratios and sintered at 1500 °C for 2 h to obtain good mechanical and thermophysical properties. The Mg2SiO4 plays a fixing role, inhibiting the growth of MgO grains and further promoting the discharge of pores. This fixation can prevent the linear expansion of cracks, thus increasing the fracture surface energy of the specimen. In addition, the scattering effect of pores on gas molecules decreases as the magnesite tailings content increase, so that the thermal conductivity increases. The results showed that when the mass ratio of magnesite tailings to fused magnesia was increased from 1:1 to 1:0 with 4 wt% soluble starch as the pore-forming agent, the apparent porosity decreased from 35.59% to 11.8%; the bulk density increased from 2.37 to 2.82 g∙cm−3; the linear shrinkage ratio increased from 9.28 to 24.23%; the cold compressive strength increased from 47.75 to 226.52 MPa; the residual strength retention rate after one thermal shock cycles at 1100 °C was between 64.05 and 87.76%; and the thermal conductivity increased from 7.44 to 12.23 W∙m−1 K−1.