Preparation Of SiC Porous Ceramics By Gelcasting Combined With Foaming

SiC porous ceramics with high strength,wear resistance,corrosion resistance,oxidation resistance,high surface area and excellent thermal shock resistance,have broad application prospects in the filtration and separation,catalyst carrier,heat exchange and sound insulation field.In this paper,SiC porous ceramics with high porosity and high strength were prepared by gelcasting combined with foaming method using SiC micro powder as raw material.Based on the influence law study of the ratio of monomer to crosslinker,monomer content and solid content on the viscosity of the slurry before gelation and the bending strength of SiC porous ceramics.Then,the effect of two different sintering additives including clay-Al₂O₃ and Y₂O₃-Al₂O₃,sintering temperature,foaming agent type and content on the pore structure and bending strength of Si C porous ceramics was systematically investigated.The results are as follows:?1?The effect of process parameters on the viscosity of SiC ceramic slurry and the properties of SiC porous ceramics was studied.The results showed that the viscosity of SiC slurry increased when the ratio of monomer to crosslinker and the solid content increased,while the viscosity of SiC ceramic slurry decreased when monomer content increased.The bending strength of SiC porous ceramic increased firstly and then decreased when the ratio of monomer to crosslinker and the monomer content increased,at the mean time,the bending strength increased when the solid content increased.Considering the viscosity of the slurry and the properties of SiC porous ceramics,the optimum process parameters of SiC slurry are as follows:the solid content was 60 wt%,the monomer content was 15 wt%,the ratio of monomer to crosslinker agent was 12:1,the porosity of SiC porous ceramics was 47.3%,the bending strength reached 16.9 MPa.?2?The effect of sintering temperature and sintering addtives on the properties of SiC porous ceramics was studied.The results show that the change law of properties of SiC porous ceramics with different sintering addtives was basically same:the bulk density and the bending strength increased while the porosity decreased when the sintering temperature increased.For the Y₂O₃-Al₂O₃ sintering additive system,the porosity of SiC porous ceramics was 46.5-57.3%,and the bending strength was10.1-25.2 MPa when the sintering temperature of the SiC porous ceramics changed from 1250-1350?.For the clay-Al₂O₃ sintering additive system,the porosity was36.5-45.4%and the bending strength was 17.3-41.0 MPa when the sintering temperature changed from 1300-1450?.Comparing with the samples adding different sintering additive system,when the sintering temperature of the two samples was the same,due to the formation of liquid phase and more mullite content,the porosity of SiC porous ceramics with clay-Al₂O₃ sintering additive was lower and the bending strength was higher.When the sintering temperature was 1350?,the porosity and bending strength were 42.0%and 32.4 MPa.?3?The effect of the type and content of foaming agent on the structure and properties of SiC porous ceramic was studied.The results showed that when the CTAB and SDBS content increased under the range of 0-0.7 wt%.The porosity and bending strength of the SiC porous ceramics with SDBS were 42.3-48.1%and 12.0-33.6 MPa,respectively.The porosity of the samples with CTAB was 42.3-73.6%,and the bending strength was very low.Due to the foaming ability and bubble stability of CTAB are better than that of SDBS,the porosity of the samples with CTAB was larger than that of the samples with SDBS.With the increase of foaming agent content,the pore size of the samples with SDBS increased,while pore size of the sample with CTAB was mainly100-200?m,and the number of pore with large size was more and more.