SHANG Heng, YUAN Wenjie, ZHU Qingyou, DENG Chengji, ZHU Hongxi
(The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, Hubei, China)

Abstract: With the advantages of their components such as high melting point, low thermal conductivity and good corrosion resistance, calcium aluminate/ magnesium-aluminum spinel composites have a very wide application prospect in high temperature industries. Calcium aluminate/magnesium-aluminum spinel composites were prepared at 1300-1600 °C by using light-burned dolomite, alumina and tin oxide as raw materials. Effects of tin oxide on the phase composition, microstructure and properties of calcium aluminate/ magnesium-aluminum spinel composites were investigated by X-ray diffraction and scanning electron microscopy. The results showed that the mass loss and shrinkage of sintered samples varied due to the sublimation of tin oxide and the decomposition of light-burned dolomite. Tin oxide not only enhanced the formation of calcium hexaluminate and magnesium-aluminum spinel but also made monocalcium aluminate and CaSnO₃ involved in composites as a result of the effect of SnO₂ on the reaction process. Moreover, the morphology of the phases was changed because of the solution of SnO₂ in calcium hexaluminate and magnesium-aluminum spinel. With the increase of SnO₂ addition, the apparent porosity of composites firstly increased and then decreased. When the SnO₂ content was 35%, the composites sintered at 1600 ℃ achieved the highest compressive strength of 240 MPa.
Key words: calcium aluminate; magnesium-aluminum spinel; tin oxide; microstructure; strength