Preparation And Influencing Factors Analysis Of High Performance Cordierite Ceramics

Cordierite（2MgO · 2Al₂O₃ · 5SiO₂）has excellent properties with low thermal expansion coefficient（CTE）,good high temperature performance,good adsorption performance,large specific surface area,stable chemical properties and good dielectric properties.Therefore,cordierite ceramics as a turbine engine heat exchangers and other fields,in the car exhaust treatment,ozone suppression catalysis,toxic gas purification,play a significant role.Due to the application range is still in the expansion of the cordierite,its performance,especially puts forward higher requirements for thermal expansion performance.It became a hot research topic that how to decrease the CTE of cordierite effectively.In this experiment,cordierite ceramics were prepared by high-temperature solidstate reaction synthesis method using "talc-kaolin-alumina" system.Therefore,the main raw materials used in this experiment are talc,kaolin,calcined kaolin and aluminum hydroxide.The effects of chemical composition,additives and pore-forming agents on the properties of cordierite were studied.The phase composition,crystal structure,surface morphology hole shape,pore size and hole distribution of the cordierite ceramic samples were observed by XRD,FT-IR and SEM respectively.By comparing the CTE,water absorption,porosity and compressive strength of cordierite ceramics,Determine the best preparation process.The main conclusions are as follows:The optimum formulation for cordierite ceramics is an aluminum-enriched formulation with an aluminum-magnesium ratio of 1.05.The CTE of the sample is 1.619 × 10-6 / ℃,and the water absorption and porosity are 14.66% and 25.12% respectively.SEM images show the distribution of pore structure and cracks,and its size and distribution are more uniform.From the XRD spectrum and FT-IR spectrum analysis,when the raw materials contain more Al₂O₃,can be fully reacted with MgO to produce magnesia-alumina spinel,and then react with SiO₂ to generate a large number of cordierite,can reduce the mesophase.This is conducive to the formation of cordierite,reducing the generation of other hybrids.With the addition of vanadium pentoxide,fused silica and zirconia as additives,it was found that the addition of 4% V₂O₅ was the best.The CTE of the sample was reduced to 0.866 × 10-6 ℃-1,and the water absorption and porosity increased to 22.65% and 33% respectively.By XRD and FT-IR analysis,although a small amount of enstatite,but the sample cordierite purity is still high.The V⁵⁺ ions in V₂O₅ have high activity and enter into the six-membered channel in the sintering process,which causes a certain degree of distortion of the six-membered ring,and forms new bonds V-O-Si and V-O,replacing Al-O-Si bonds and Mg-O bonds.The cordierite structure is slightly deformed,which makes the cordierite crystal structure in the a-axis more compact,c-axis structure is not affected.So that the CTE of cordierite is reduced,and the decomposition of V₂O₅ can produce many uniformly distributed pores in the ceramic sample,so that the porosity of the ceramic increases.With MC,starch,carbon powder and rice husk as the pore-forming agent,it was found that the addition of 10% MC was the best.The water absorption and porosity of the samples were increased by 29.87% and 40.53% respectively,and the CTE was reduced to 1.029 × 10-6℃-1.The XRD and FT-IR analysis showed that the samples were almost pure cordierite.There will be a small amount of enstatite.It can be seen from the SEM images that the size of grain size distribution,the formation of many pores which is irregular shape.