Study On The Preparation And Properties Of RGO-C/C-SiC Composites

Carbon fiber reinforced carbon/silicon carbide(C/C-SiC)ceramic double matrix composites maintain low density,high specific strength and other characteristics of C/C composites,and have better oxidation resistance.They are widely used in the fields of space optical machines,brake and aerospace applications.However,with the advent of the high-frequency and high-speed 5G era,various advanced equipments have put forward higher requirements for C/C-SiC composites.It is expected that the composites will possess longer life-time,higher strength,lower density,more resistant to high temperatures,and have physical functions such as electromagnetic interference shielding,to produce materials with structural and functional properties combined.Increasing the content of SiC can improve the oxidation resistance of C/C-SiC composites,but the electromagnetic shielding performance of materials often is weakened with increasing SiC.Therefore,in this paper,we propose to introduce reduced graphene oxide(rGO)with high surface area and high conductivity into SiC to improve the conductance and electromagnetic shielding properties of SiC,and keep its antioxidant properties at the same time.Then,the comprehensive performance of C/C-SiC composites are enhanced.In this paper,the polycarbosilane-tetrahydrofuran solution containing graphene oxide(GO)is used as the impregnating solution.SiC contained rGO is combined with carbon fiber cloths protected by pyrocarbon through precursor infiltration and pyrolysis(PIP)process.Then,the carbon cloth laminate preforms were densified to prepare rGO-C/C-SiC composites.The effects of rGO concentration,number of PIP,CVI deposition time,and alternation times of PIP-SiC and CVI-Py C on the mechanical,anti-oxidation,conductivity,and electromagnetic shielding properties of composites were investigated in detail.The composition-structure-property interrelated relationship of rGO-C/C-SiC composites with structural and functional properties combined is revealed.The main contents and conclusions of this article are as follows:(1)Study on the influence of graphene content on the properties of C/C-SiC composites.The results show that,as the rGO content increases,the flexural strength,electrical conductivity,and electromagnetic interference shielding effectiveness of the composites increase first and then decrease.Compared with the sample A_{(GO:PCS=0 wt.%)},the flexural strength of sample C_{(GO:PCS=2 wt.%)}increased by 28%to 251.67±20.21MPa.In addition,the conductivity and electromagnetic shielding effectiveness of sample C_{(GO:PCS=2 wt.%)}are also optimal.The increased polarization loss and conduction loss make the average SE_Tof sample C_{(GO:PCS=2 wt.%)}with thickness less than 1 mm as high as 45 d B in the X-band.However,the performances of sample D_{(GO:PCS=5 wt.%)}were lower than that of sample C_{(GO:PCS=2 wt.%)}due to the agglomeration of rGO.(2)Study on the influence of the number of PIP and the time of CVI on the properties of rGO-C/C-SiC composites.It was found that the oxidation resistance of rGO-C/C-SiC composites gradually increased with the increase of the number of PIP through constant temperature rate oxidation test.Compared with the sample PIP-1,initial temperature of oxidation,temperature at maximum oxidation rate and finish temperature of oxidation of PIP-5 increased by 68?,85.8?and 46.7?,respectively.Moreover,isothermal oxidation test showed that the oxidation apparent activation energy of PIP-5 was higher than that of PIP-1.The flexural strength and electromagnetic shielding effectiveness of rGO-C/C-SiC composites increased first and then decreased as the number of PIP increased.Under the same number of PIP,the electromagnetic interference shielding performance of the composite material increased with increasing the time of CVI.(3)Study on the effect of CVI-Py C and PIP-SiC alternation times(n)on the properties of rGO-C/C-SiC composites.Different microstructures rGO-C/C-SiC composites were prepared by changing the alternate times between rGO modified SiC and Py C matrix.It was found that mechanical properties of the composite decreased with the increasing value of n.The sample S3 with n=4 has the smallest bending strength and fracture toughness of 130±15.52Mpa and 6±0.6MPa·m¹/² among composites.However,the electrical conductivity and electromagnetic interference shielding effectiveness of(SiC₁-Py C_10h)4 increase with increasing value of n.Compared with(SiC₄-Py C_40h)1,the conductivity of(SiC₁-Py C_10h)4 is 53%larger;the average SE_T in the X-band is 10d B larger,reaching 41d B.