Preparation And Sintering Properties Of SiC Honeycomb Ceramics For Exhaust Gas Purification Of Diesel Vehicles

With the continuous development of the economy,the per capita car ownership has also been on the rise.Diesel engines with low fuel consumption and high power have gradually replaced gasoline engines as the main power plant for vehicles.At present,the cordierite honeycomb ceramics,which is widely used in diesel exhaust gas purification catalyst carriers,have low thermal conductivity,narrow firing range,and the inability of the catalyst to stably adhere to the inner wall of the ceramic honeycomb resulting in poor catalytic purification effect on the diesel exhaust gas,the cordierite honeycomb ceramic has limited its popularization and application.The good mechanical properties at room temperature and the best high temperature mechanical properties in ceramic materials of SiC honeycomb ceramic make it has an irreplaceable research value in the application of catalyst carrier for diesel exhaust purification.For the problem of SiC difficult to sinter,using Al₄SiC₄ as a sintering aid for the preparation of recrystallized SiC honeycomb ceramics,it is also very important to explore the mechanism of Al4SiC4 on the crystal transformation of SiC recrystallization process.The project uses SiC micro-powders of different particle sizes as the main raw material,and SiC honeycomb ceramics are prepared by extrusion molding.The effects of 0.5 wt%?-Al₂O₃ and 4 wt%Al₄SiC₄,and optimization of SiC honeycomb ceramic composition and heat treatment system on the microstructure and properties of SiC honeycomb ceramics were investigated.The recrystallization process of SiC fine particles and the crystal transformation process of SiC coarse particles during the heat treatment process of SiC honeycomb ceramics and the influence mechanism of Al₄SiC₄on these two reaction processes have been described in detail.The conclusions are as follows:?1?Compared with SiC ceramic honeycomb ceramics containing 0.5 wt%of?-Al₂O₃,the relative strength of 4H-Si C in SiC honeycomb ceramics with Al₄Si C₄ is high.It shows a good skeleton structure,pore size concentration,and greater compressive strength.?2?When the addition amount of Al₄SiC₄ is 4 wt%,the SiC honeycomb ceramics exhibit a good skeleton structure,concentrated pore size,and maximum compressive strength.As the addition of Al₄SiC₄ continues,the hive structure of Si C honeycomb ceramics has undergone a certain degree of deformation.The Al decomposed from Al₄SiC₄ not only forms Al-Si droplets by contacting with Si to accelerate the recrystallization of fine SiC particles,but also solid solution into SiC crystals to form Al-SiC solid solution and promote the crystal transformation of coarse SiC particles.?3?The heat treatment system has a great influence on the growth of SiC grains and the formation of skeletal structure in Si C honeycomb ceramics.When the holding time is 1h,the grain growth of Si C honeycomb ceramics is complete,showing a good skeleton structure,the pore size is concentrated,and has a greater compressive strength.