New Modification Of Molding Process Combining PIP Process Preparation Of SiC Ceramics

SiC ceramic and SiC matrix ceramic composites have high melting point,oxidation resistance,erosion resistance,low density,corrosion resistance,high strength and many other excellent performances,they have widely application foreground in the field of aerospace and nuclear fields.The sintering process of SiC ceramic matrix need high temperature and sintering additives,high temperature will cause a bad influence on the performance of the material process;Sintering additives also have effct on the mechanical property of material.PIP process of preparing SiC ceramic matrix have advantages of low sintering temperature and without sintering additives,which has an extensive research inbroad and abroad.But traditional PIP process of preparing SiC ceramic need heat moulding,it is not fit for preparing large profiled.And some basic datas,such as flexural strength,compressive strength,flexural modulu,thermal conductivity and poisson’s ratio,are still not perfect about SiC ceramic matrix made by PIP preparation process.This article intends to study on modifying PIP process to prepare SiC ceramic matrix,explore Protein Coagulation Casting+PIP process and Freeze Drying+PIP process of preparation of SiC ceramics,System to study the influence of initial compositions on flexural strength,compression strength,density,thermal conductivity and other properties,and test the flexrual modulu and poisson’s ratio,then test and analysis the structure,composition and the content of SiC of PIP pyrolytic product.Tested and analysed the PIP pyrolytic product composition and content of SiC.Study found:PIP product has a small amount ofβ-SiC microcry stalline,a large number of amorphous SiC and some free C and Si-C-O phase.The Si element content in the pyrolysis product of PCS was 65.98 wt%,O element content was 1.56 wt%,C element content was 32.46wt%,SiC content was 92.84wt%.And Si element content in the pyrolysis products of LPVCS was 52.17wt%,O element content was 9.48wt%,C element content was 38.35 wt%,SiC content was 76.28 wt%.Green bodies of SiC ceramic were prepared by Protein Coagulation Castingprocess using SiC powder and PCS as raw materials,then sintered and improved performance by PIP process at 1100℃using LPVCS as precursor.We studied the influence of amount of the PCS,the amount of protein,solid content etc,on the structure and properties of SiC ceramics.The results show that the PIP process can effectively improve the performance of the SiC ceramic.With more addition of PCS,SiC ceramic density increases,but the opening rate and the pore size decrease.Flexural strength,compression strength and thermal conductivity decreased after first increase;For the amount of protein increases,density,flexural strength,felxural modulus and compression strength decreased after first increase,but opening porosity show the opposite trend.Maximum value of flexural strength,flexural modulus,compression strength respectively were 99.9MPa,28.36GPa,28.36GPa,poisson’s ratio was 0.101.Thermal conductivity increased,and the maximum value was 4.83W·m^-1·K^-1.With the increase of solid content,density,bending strength,compression strength and thermal conductivity increased,while open porosity is reduced.Used SiC powder and PCS as raw materials,adopt Freeze-Drying preparation of green bodies of SiC ceramic,then sintered and improved performance by PIP process at1100℃using solution of PCS as precursor.We studied the influence of the amount of PCS and solid content on the structure and properties of SiC ceramics.The study found that with the increased of PCS addition,density increased,but open porosity decerased,flexrual strength and compression strength are increased,and the thermal conductivity decreases;With the increase of solid content,the density increased,opening rate decreased.And the flexuralstrength,compression strength,thermal conductivity were increased.