Fabrication And Characterization Of Porous SiC Ceramics Prepared By Selective Laser Sintering

Due to the high temperature resistance,strong corrosion resistance,excellent chemical stability,mechanical properties,porous SiC ceramics have been widely used in the fields of molten metal filtration,smoke filtration,and automobile exhaust purification.Mold forming is conventional preparation methods of porous SiC ceramics,which can fabricate simple structure of porous ceramics,and it is difficult to prepare the porous ceramics with complex configuration.Recently,selective laser sintering technology（SLS）was presented and this preparation method may be used to fabricate complex porous ceramic structures.However,it is immature to prepare porous SiC ceramics by SLS technology.The strength of SLS-forming porous SiC ceramics is low and can not meet the requirements of the practical application.In this work,the green part of the complex porous SiC ceramic structures were firstly prepared by SLS technology and they are strengthened by the followed sintering process.The SiC ceramic structures with high porosity and mechanical properties were fabricated.The influences of sintering process,mullite content,hollow microsphere size and content on porosity,volume density,bending strength and other properties of porous SiC ceramics were investigated.The morphology and phase composition of porous SiC ceramics were also analyzed and characterized.（1）The effects of the sintering process on the properties of porous SiC ceramics were studied.The results showed that the sintering process can promote the strength of the green part prepared by SLS technology.With the increase of sintering temperature,holding time and decrease of heating rates,the strength of porous SiC ceramics were improved.When the sintering temperature,heating rate,holding time are 1300°C,3°C/min,3 h,the porosity,density,bending strength of porous SiC ceramics are 44.99%,1.40 g/cm³ and 61.93 MPa.（2）The effects of mullite content on the properties of porous SiC ceramics were studied.The results showed that the addition of mullite can effectively improve the strength of porous SiC ceramics.With the increase of mullite content,the strength of porous SiC ceramics were increased.When the content of mullite is 30 wt%,the porosity,density,bending strength of porous SiC ceramics are44.99%,1.40 g/cm³ and 61.93 MPa.（3）The effects of SiO₂ hollow microsphere on the properties of porous SiC ceramics were studied.The results showed that the porosity of porous SiC ceramics can be promoted by the addition of SiO₂ hollow microspheres.When the particle size became larger or the content of SiO₂ hollow microsphere increased,the open porosity of porous SiC ceramics were gradually increased.When the diameter and the content of SiO₂ hollow microsphere are 50μm,10wt%,the total porosity of porous SiC ceramics,opening porosity,bending strength are 67.3%,62.5%,39.28 MPa.