The Research On Preparation And Modification Of Cordierite Bonded Silicon Carbide Porous Ceramics

With the industrial development of the world economy,using energy consumption as the main driving force of the electric power,metallurgy,chemical,coal and other industries facing severe environmental pollution crisis.Due to the porous silicon carbide ceramics having excellent high-temperature mechanical properties,good corrosion resistance,thermal shock resistance and other strong features,it is increasingly becoming the industrial production of high temperature gas dust removal efficiency core components.Cordierite as Al2O3-MgO-SiO2 system stable compound,its low coefficient of thermal expansion;high thermal stability,which is combined with a porous silicon carbide ceramic material can not only improve the overall thermal shock resistance,while can reduce the sintering temperature of the substrate,effectively improve the high temperature strength and filtration efficiency of porous ceramics.In this experiment,silicon carbide,alumina,talc,diatomate,kaolin as the main raw material,by adding graphite as a pore-forming agent to prepare cordierite-bonded silicon carbide porous ceramics.The effects of mass ratio of diatomate,La2O3,TiO2 on flexural strength,porosity,dielectric properties,phase composition and microstructure of silicon carbide porous ceramics were discussed.The open porosity of the sintered specimens was determined by the Achimedes methods with distilled water as the liquid medium,flexural strength were via the three-point bending test,phase composition and microstructure of the silicon carbide porous ceramics were tested by the X-ray diffraction(XRD)and scanning electron microscopy(SEM)respectively.Through systematic research,the main research conclusions are as follows:(1)Cordierite-bonded silicon carbide porous ceramics with diatomite as silicon source were prepared via reaction bonding technique.It was found that the cordierite structure can incorporate of diatomite(like Fe2O3)by solid solution formation,which can highly enhance on the electrical properties of cordierite-bonded SiC porous ceramics.Meanwhile,due to the enhancement of necks at the contacting pionts growth by the additions of diatomite(5.17wt%),a high three-point flexural strength of 49.19MPa was achieved at an open porosity of 37.72%sintered at 1250? for 3h.(2)The effects of La2O3 addition on the modification of cordierite-bonded silicon carbide porous ceramics were systematic research.La2O3 as a hexagonal close packed lanthanide rare earth elements can effectively inhibit the generation of cristobalite,promoting low temperature synthesis cordierite phase.When 0.6wt%La2O3 was added,a high three-point flexural strength of 62.26MPa was achieved at an open porosity of 31.40%.However,too much La2O3 addition,which produces a molten liquid will cause the value of the porosity and flexural strength of the ceramic material plunged.(3)The effects of TiO2 addition on the modification of cordierite-bonded silicon carbide porous ceramics were also been tentative researched.TiO2 used as a sintering aid with high chemical activity.Ti4+ by diffusion into the interior of the substrate,then displace the Mg2+,Al3+ of the cordierite to form interstitial solid solution,by lowering the temperature in the liquid phase generated,promoting low temperature synthesis of cordierite.