Study On The Preparation And Characterization Of In-situ Growth SiC Nanowire Felt

SiC has the properties combination of high temperature resistance,outstanding chemical stability,excellent mechanical properties which is widely used as high-temperature structural material,wear resistant material and corrosion resistant material.Meanwhile,SiC is also a kind of new generation wide bandgap semiconductor material with the properties of wide energy bandgap,high critical breakdown voltage,excellent thermal conuctivity,high electorn drift speed,which is widely used in high temperature,high voltage and strong radiation environment.SiC nanowire is a kind of one-dementional nano material,benefit from the special nanostructure,the SiC nanowire has excellent field electron emission performance,superplastic property,photocatalytic performance and photoluminescence performance besides the properties of SiC bulk material,which is applicable as electronic nanodevices,nano reinforced composites,photocatalysts,hydrophobicdevices,optoelectronic nanodevices.In this paper,SiC nanowire felt with highly porous 3D nanowire architecture was synthesized by polymer pyrolysis chemical vapor deposition?PPCVD?process to deposit SiC nanowires in the pores of carbon foam,followed by high temperature oxidation of carbon foam.And the element composition,microstructure,mechanical properties,thermal insulation performance,hydrophobic property of the prepared SiC nanowire felt were studied.Here,the carbon foam with high porosity?over 99%?was used as the growth matrix and the templet of the SiC nanowire felt,which was fabricated by the directly pyrolysis of melamine foam?MF?.The density,volume shrinkage,porosity,length and diameter of the carbon skeleton of the carbon foam prepared at different pyrolysis temperature were analysised.At the same time,the effects of different heating rates at pyrolysis process on the macroscopic morphology was studied.The preparation process of carbon foam with controllable morphology and geometric size was obtained.The SiC nanowires with the length of over 500?m and diametr of 80-100 nm was successfully prepared in the pores of carbon foam by PPCVD process.After the oxidation of carbon foam,the pure SiC nanowire felt was prepared.In this paper,the SEM,TEM,TG,XRD,FT-IR,Lser thermal conductivity measuring instrument,universal testing machine,Hydrophobic angle measuring instrument were used to study the the element composition,microstructure,mechanical properties,thermal insulation performance,hydrophobic property of the prepared SiC nanowire felt.The results indicate that the SiC nanowires with the diamenter of 80-100 nm and length of over 500?m is?-SiC with good crystallization which is composed of Si and C elements,and little O element was found due to the oxidation of the SiC nanowires.The growth of SiC nanowires was employed by V-L-S mechanism.A large number of ultra-long SiC nanowires make up the highly porous 3 D nanowire network structure,the presence of many bundles and branches among the SiC nanowires at atomic level improves the strength and flexibility of SiC nanowire felt.The compressive strss of SiC nanwire felt is 0.11 MPa and the recoverable compression strain is more than 90%when the compression strain was less than 30%.The prepared SiC nanowire exihibites high-temperature oxidation resistance?750??,noncombustible and fire resistance,excellent thermal insulating performance?0.03 W·m-1·k-1at room temperature,0.23 W·m-1·k-1at 900? in He?,which can be used as high-temperature heat insulator,ceramic matrix composite,high temperature flue gas filter,catalyst support and fire-proofing material.The hydrophobic angle of the prepared SiC nanowire felt without the high-temperature oxidation of the carbon foam is more than 150°,showing that the SiC nanowire felt without the high-temperature oxidation of the carbon foam has super hydrophobic properties.When the SiC nanowire felt with carbon foam is burned at high-temperature,the hydrophobic group-CH₃ was burned off,SiC nanowire felt lost the hydrophobic properties.