Study On Density Of Sintered Magnesia

As the basic raw refractory, the bulk density of sintered magnesia has an important effect on the properties of magnesia refractory, especially on the properties corrosion resistance and high-temperature strength. China’s magnesia is mainly obtained by calcining magnesite, but due to the properties of our country’s magnesite and the restrictions on current production process, the quality of existing magnesia already cannot meet the market need.Taking the magnesite form south of Liaoning province as raw material, differential thermal analysis and Fourier infrared spectroscopic analysis were employed to observe and study the effects of additives on decomposition temperatures of magnesite. The effects of processing technology and small amounts of sintering additive on bulk density of sintered magnesia were investigated, and phase composition and microstructure were examined. The obtained conclusions are as follows.(1) Hydration process can improve the density of sintered magnesia, but the production process of magnesia is long and complex, it is so costly that it not suitable for mass industrial production.(2) Tetra-n-butyl titanate and yttria can improve the density of sintered magnesia. The bulk density of sintered magnesia reached3.40g/cm3after adding either tetra-n-butyl titanate or yttria into magnesite. However, the affect of cerium and lanthanum are not obvious to the density of sintered magnesia.(3) All of Tetra-n-butyl titanate, yttria, cerium oxide, lanthanum oxide, magnesium fluoride have no effect on decomposition temperatures of magnesite. However, magnesium chloride could reduce the decomposition temperature of magnesite. The decomposing temperature of magnesite was decreased by150℃after adding5%of magnesium chloride. When the addition of magnesium chloride was lower than10%, the decomposition temperature of magnesite decreased with the increase of magnesium chloride. There were no more changes on decomposition temperature when magnesium chloride contents were more than10%.(4) Magnesium chloride can destroy the primitive structure of magnesite. The structre of light calcined magnesia, which made from magnesia added magnesium chloride, is flocculent. Magnesium chloride can improve the density of sintered magnesia, However, the affect of magnesium fluoride were not obvious.