Research On The Reaction Of MgAl₂O₄/SiC Composites

MgAl₂O₄and SiC, which have excellent physical and chemical properties, are widelyused in high temperature industry. It maybe obtain a new material that has betterperformances, and have promising applications in metallurgical, cement, nonferrousmetallurgical, petrochemical industries, etc. Accordingly, this subject researches thereaction of MgAl₂O₄-SiC composites to provide some theoretical support for preparationand application of MgAl₂O₄-SiC composites.Different proportion of MgAl₂O₄and SiC were weighed and mixed evenly, after thatpressed into column shaped of Φ30mm×30mm at200MPa, then sintered at1400℃,1500℃and1600℃for3h in air atmosphere and carbon bed atmosphere respectively.The phase compositions of samples were analyzed by XRD method and microstructureby SEM. the result showed that the specimen containing SiC can form cordierite at1400℃in the air atmosphere, the amount of cordierite has related to the amount of SiCaddition. The specimens containing SiC oxidized slightly at1500℃and oxidizedcompletely at1600℃. In order to improve the sinterability and oxidation resistance ofMgAl₂O₄/SiC composites, different content of Si power and Al powder were added to thespecimens containing20%SiC. It concluded that the specimens with addition of Alpowder has better oxidation resistance than the specimens with Si powder at eachsintering temperature due to the formation of Al₂O₃film on surface of specimens for theoxidation of Al powder. The addition of Si powder has effect of oxidation resistance, butthe effect lost at high temperature for the oxidation product of Si powder can reactionwith MgAl₂O₄to form cordierite.When MgAl₂O₄/SiC composites sintered in carbon bed atmosphere, it concludes thatalumina-rich spinel was formed for the volatilization of Mg. The relative content ofMgAl₂O₄and SiC did not change the amount of Mg through calculating the lattice ofMgAl₂O₄, so the oxidation of MgAl₂O₄/SiC composites are mainly caused by theoxidation of SiC. A little cordierite was observed on the surface of MgAl₂O₄and SiC bythe SEM analysis, the particles accumulate simply, so the specimen has poor sinterability.The research on specimens with addition of Al powder or Si powder sintered at carbonbed atmosphere showed that the oxidation of SiC deduces, but the Al powder or Si powder has high activity, which that could form liquid phase to improve the sinterabilityof MgAl₂O₄/SiC composites sintered in carbon bed atmosphere.