Abstract: This paper studies the effects of fused magnesium aluminate spinel and caustic calcined magnesia on synthesis of magnesium-iron-aluminum composite spinel.Fused magnesium aluminate spinel and caustic calcined magnesia hydroxide are evenly mixed with activated alumina and ferric hydroxide to prepare specimens with diameter of 20 mm× 10 mm,under air atmosphere sintering condition,the 1550 ℃ by 6 h high temperature sintering.The phase composition and microstructure of the samples were characterized by analysis of XRD,SEM and EDS.The results show that fused magnesium aluminate spinel is added to the sample,it generated corundum,hematite,hercynite and magnesium-iron-aluminum composite spinel phase four mineral phases,the chemical formula of magnesium-iron-aluminum composite spinel is Mg7.96Al15.31 Fe0.68O32,caustic calcined magnesia is added to the sample,it generated corundum phase,hercynite and magnesium-iron-aluminum composite spinel three mineral phases,the chemical formula of magnesium-iron-aluminum composite spinel is Al15.71 Mg3.35 Fe4.94 O32,the grain size of magnesium-iron-aluminum composite spinel is not much difference between grain size of hercynite in the sample of adding with fused magnesium aluminate spinel,hercynite is obviously biger than magnesiumiron-aluminum composite spinel in the sample of adding with caustic calcined magnesia.

Key words: This paper studies the effects of fused magnesium aluminate spinel and caustic calcined magnesia on synthesis of magnesium-iron-aluminum composite spinel.Fused magnesium aluminate spinel and caustic calcined magnesia hydroxide are evenly mixed with activated alumina and ferric hydroxide to prepare specimens with diameter of 20 mm× 10 mm,under air atmosphere sintering condition,the 1550 ℃ by 6 h high temperature sintering.The phase composition and microstructure of the samples were characterized by analysis of XRD,SEM and EDS.The results show that fused magnesium aluminate spinel is added to the sample,it generated corundum,hematite,hercynite and magnesium-iron-aluminum composite spinel phase four mineral phases,the chemical formula of magnesium-iron-aluminum composite spinel is Mg7.96Al15.31 Fe0.68O32,caustic calcined magnesia is added to the sample,it generated corundum phase,hercynite and magnesium-iron-aluminum composite spinel three mineral phases,the chemical formula of magnesium-iron-aluminum composite spinel is Al15.71 Mg3.35 Fe4.94 O32,the grain size of magnesium-iron-aluminum composite spinel is not much difference between grain size of hercynite in the sample of adding with fused magnesium aluminate spinel,hercynite is obviously biger than magnesiumiron-aluminum composite spinel in the sample of adding with caustic calcined magnesia.