Preparation And Properties Of Mullite Composite Silicon Carbide Porous Ceramics

Silicon carbide porous ceramic materials have their own unique physical and chemical properties,For example,it has excellent mechanical properties,good chemical resistance,high thermal conductivity,low expansion and high thermal shock resistance,and has been widely used in metallurgy,chemical engineering,environmental protection,and energy.Mullite has stability.Using mullite bonded silicon carbide not only improves the thermal shock resistance of porous ceramics,but also enhances the oxidation resistance of silicon carbide,while the mechanical properties have been enhanced.In this experiment,silicon carbide,chromatographic alumina and coal gangue were used as the main raw materials.A mullite-bonded silicon carbide porous ceramic material was prepared by adding graphite as a pore-forming agent.The effects of coal gangue,YF3,and CaO on the bending strength,porosity,and oxidizing properties of silicon carbide and their effects on the phase and microstructure of porous ceramic materials were systematically studied.The porosity of samples was measured by Archimedes drainage.The flexural strength of samples was tested by three point bending test,the phase composition of samples was analyzed by XRD ray diffractometer,and the microstructure changes of cross-section were characterized by scanning electron microscope(SEM).(1)The effect of coal gangue content on the properties of mullite-bonded silicon carbide porous ceramics was studied systematically.At the same time,the particle size of silicon carbide particles and the graphite content of pore-forming agent were systematically studied.The experimental results show that as the content of graphite increases,the bending strength of the sample gradually decreases and the porosity increases gradually.(2)The effect of YF3 doping on the properties of mullite bonded silicon carbide porous ceramics was systematically investigated.The experimental results show that YF3 can effectively enhance the reaction of silica and alumina generated by the oxidation of silicon carbide to generate a metastable glass phase of Y-Al-Si-O with lower viscosity,Y-Al-Si-O The metastable glassy phase promotes the oxidation of silicon carbide and the formation of mullite,and enhances the flexural strength of the ceramic substrate.At the same time,the results show that the excessive addition of YF3 is not conducive to the improvement of the performance of the ceramic substrate.(3)The effect of the addition of alkali metal oxide CaO on the mullite-bonded silicon carbide porous ceramics was investigated.The addition of CaO can promote the reaction between Al2O3 and SiO2,resulting in the liquid phase of Ca-Al-Si-O with low viscosity,strengthening the oxidation reaction of SiC,making mullite easier to produce,and bending the sample.The strength is effectively improved,but the formation of a liquid phase of excessively low viscosity Ca-Al-Si-O also results in a decrease in the porosity of the sample.When the content of CaO is 2 wt%,the porosity of the prepared mullite-bonded silicon carbide porous ceramic is 38.25%and the flexural strength is 62.34 MPa,which achieves the best overall performance.