Study On Preparation And Properties Of Ti₃SiC₂-SiC Composite

Ti₃SiC₂ is a new type of ceramic material,which has many excellent properties of metal and ceramics.It has the advantages of high temperature resistance,good high temperature oxidation resistance,high thermal and electrical conductivity,low hardness,and easy processing.It has broad application prospects in many aspects and is expected to become one of the most promising new ceramic materials.The raw material Ti₃SiC₂ is compounded with SiC to prepare Ti₃SiC₂-SiC composite material to improve the material's strength,toughness and plasticity,and obtain Ti₃SiC₂-SiC composite ceramics with better comprehensive performance.In this experiment,high-purity Ti₃SiC₂-SiC composite material was prepared by pressureless sintering method.In this experiment,pressureless sintering method was used to prepare Ti₃SiC₂/SiC composites with Si powder,TiC powder,and Al powder as raw materials.X-ray diffraction analysis,vector network analyzer,scanning electron microscope,micro-control electronic universal testing machine and other detection methods and methods are used to analyze and study the microstructure and mechanical properties of the Ti₃SiC₂/SiC composite material.The main research contents are as follows:(1)Based on the molar ratio of raw materials TiC:Si:Al=3:2:0.2,in an argon atmosphere,at temperatures of 1400?,1500?,and 1600?,the synthesized composite material is mainly TiC The crystal phase contains a small amount of Ti₃SiC₂and SiC phases,indicating that Ti₃SiC₂ and SiC phases can be formed in this solid-state replacement in-situ reaction.From the XRD diffraction pattern,it can be observed that as the temperature rises,the high temperature promotes the product The Ti₃SiC₂ quickly decomposes to form TiC(solid),while Si volatilizes from the sintered body.The composite material has high porosity and loose microstructure.Among them,composite material with a relative density of 44.32%can be obtained at 1400?.Its fracture toughness and bending strength reached 1.78 MPa·m^1/2and 145.62 MPa,respectively.The dielectric properties of Ti₃SiC₂/SiC samples are related to the content of Ti₃SiC₂.As the content of Ti₃SiC₂ increases,the real part and imaginary part of the sample's complex permittivity both show increasing trend.(2)Based on the molar ratio of raw materials TiC:Si:Al=3:2:0.2/0.5/1/2/3,in argon atmosphere,at a temperature of 1400?,the synthesized composite material will increase with the sintering aid With the increase of Al content,Ti₃SiC₂ and SiC gradually become the main phases of Ti₃SiC₂/SiC composites;when the raw material ratio is TiC:Si:Al=3:2:1,the main phase of the composite is Ti₃SiC₂ and the second phase is SiC,X-ray diffractometer did not detect the diffraction peak of TiC,indicating that TiC is basically eliminated in the composite material.The results show that the proper amount of Al can promote the mass production of Ti₃SiC₂ and SiC,and the porosity decreases and the density of the material structure increases.As the density of materials increases,the fracture toughness and bending strength are further enhanced to reach 2.21 MPa·m^1/2 and192.56 MPa,respectively.The complex permittivity of Ti₃SiC₂/SiC samples increases with the increase of Ti₃SiC₂ content.(3)With the molar ratio of raw materials TiC:Si:Al=3:1.8/2.0/2.2/2.4/2.6:1,in argon atmosphere,at temperature of 1400?,the synthesized composite material increases with the Si content Increase,when TiC:Si:Al=3:2.2:1,X-ray diffraction detects that the Ti₃SiC₂ diffraction peak is the strongest in the composite material,the main phase is Ti₃SiC₂,and the second phase is SiC;it is observed by scanning electron microscope that Ti₃SiC₂ is a flake Layered,SiC is granular,and SiC with an average grain size of about 1?m is dispersed in a Ti₃SiC₂ matrix with an average grain size of about5?m.In-situ synthesis produces a large number of Ti₃SiC₂ with good plasticity and toughness,and the material is more dense The relative density reaches 67.75%,the racture toughness and the bending strength are 2.59 MPa·m^1/2 and 230.35 MPa,respectively.The complex permittivity of the Ti₃SiC₂/SiC sample is the highest,and the dielectric performance of the composite is the best.