Study on Properties of Mg-Al Spinel Ceramics Prepared by Casting Sintering Method

Abstract

Magnesium alumina spinel (MgAl2O4) is a composite mineral composed of MgO and Al2O3, and its theoretical chemical composition is 28.33 wt% MgO and 71.67 wt% Al2O3, with excellent properties such as high melting point, high hardness, high strength, high resistivity, wide energy band gap, low coefficient of thermal expansion, corrosion resistance and thermal shock. In the process of synthesizing magnesia-alumina spinel ceramics, it is important to select suitable sintering temperature, suitable holding time, suitable kinds of mineralizers and suitable amount of mineralizers in order to improve the strength and toughness of magnesia-alumina spinel ceramics and reduce the water absorption of magnesia-alumina spinel ceramics. In this study, using fused magnesia powder and alumina powder as main raw materials, sodium hexametaphosphate as water reducer, silica powder as binder and titanium dioxide powder as mineralizer, magnesia-alumina spinel ceramics were synthesized by casting and sintering. The effects of sintering temperature and holding time on the properties of magnesia-alumina spinel ceramics were studied. The most suitable sintering temperature is about 1600 °C and the most suitable holding time is about 4 h. Titanium dioxide powder was selected as mineralizer, and the effect of adding titanium dioxide powder on the properties of synthesized magnesia-alumina spinel ceramics was studied. The experimental results show that the addition of titanium dioxide powder can improve the bending strength and reduce the water absorption of the synthesized magnesia-alumina spinel ceramics. When the addition of titanium dioxide powder increased to 7%, the bending strength of magnesia-alumina spinel ceramics increased to 33 MPa, and the water absorption decreased to 2.8%. SEM analysis shows that the addition of titanium dioxide powder can promote the formation of magnesia-alumina spinel phase, refine the grain size of magnesia-alumina spinel and strengthen the microstructure of magnesia-alumina spinel ceramics.