Preparation Of SiC_NW-C_f/LAS Composite And Its Mechanical Properties And Wave Absorption Properties Study

Silicon carbide nanowires with low dimension and small size effect showed excellent properties in the electrical,optical,magnetic and mechanical performance,so it have potentially important value for composite materials,electronic materials,sensors,etc.Accompanied by the rapid development of the social economy,the demanding request for materials have been put forward in cutting-edge technology.The integration of structure and function is becoming more and more popular in material reseacher's favor.The Si C nanowires as a reinforced phase are not only enhanced by the mechanical properties,but also the electromagnetic wave dissipation capacity of the material.It is of great significance to prepare the composite materials of one-dimensional silicon carbide and structural fuction,and the growth mechanism of nanowires and the properties of composite materials.This article uses the carbon fiber and acetylene black as carbon sources,Fe Ni50 as catalyst,the Si C nanowires was prepared by in-situ growth in carbon fiber non-woven fabric through the thermal evaporation method.Second,the Cf and Si CNW as reinforced phase composite materials(Si CNW-Cf/LAS)are synthesized by the combination of sol-gel and vacuum heat pressure sintering process.The influences of different carbon sources,different mole ration of silicon and carbon,different catalyst concentration on carbon fiber in-situ growth Si CNW were studied.The mechanism of growth of nanowires was discussed.The mechanical properties and absorbing properties of Si CNW-Cf/LAS composite are studied.The main research results are obtained as following:The Si CNW is formed by using carbon fiber and acetylene black as different carbon sources.In the case of carbon fiber as the only source of carbon,the catalyst concentration was 0.005mol/L,and the ration of silicon and carbon was 1:1,the Si CNW was developed on the surface of the carbon as wool brush.The XRD test indicates that the products made are ?-SiC.The TEM characterization further proves that the prepared Si CNW are single crystal structures.Using SEM to analyze the material of Si CNW-Cf,the appearance of “mushroom head” in the end of Si CNW,indicating that the Si CNW have a VLS growth mechanism in this paper.When carbon fiber is a single source of carbon,it is harder to grow the Si CNW in the case of the mole ration of silicon and carbon decreasing.When the catalyst concentration was 0.1mol/L,the surface of the carbon fiber was seriously corroded,and there were many pits.The Si CNW diameter are larger,and there are many more bulky “mushroom head”.As the concentration of the catalyst decreases,the corrosion pits decrease,the diameter of the Si CNW decreases,and the spherical particles in the end are reduced even disappeared.The diameter and distribution of the nanowires growing is more uniform when the catalyst concentration is 0.005mol/L.The main crystalline phase of the Si CNW-Cf/LAS composite,which is prepared by different mole ration of silicon and carbon,is a ?-spodumene.The diffraction peak of Si C is detected only in moles of silicon carbon ratio of 1:1.But compared to the main crystal,the peak is quite small.The bending strength of Si CNW-Cf/LAS composite materials is at the maximum of 597±11MPa in the intermediate layer of Si CNW-Cf's mole ratio of silicon and carbon at 1:1.It's fracture toughness and fracture work are also highest in different proportions,respectively,11.01MPa·m1/2 and 3.54kJ·m-2.The fracture toughness is increased by 46.4% compared to the composite material without the intermediate layer(7.52 MPa·m1/2).From the point of view of the fracture,the fibers of the composite with the reduction of the silicon carbon ration in the middle layer are gradually shortened until they are at the end of the fracture.Thess lead to the bending strength and fracture toughness of the material decreasing dramatically.The complex dieletric constant of the Si CNW-Cf/LAS composite material is more stable,and the range of variation is small.It is proved that the addition of the LAS matrix has improved the stability of its dielectric constant.As the same time,the size of the dielectric constant is enhaced due to the addition of fiber cloth compared to the Si CNW-Cf.The reflection attenuation performance of the Si CNW-Cf/LAS composite materials prepared at the mole ratio of silicon and carbon in 1:1,1:2,1:3 is comparable.The Si CNW-Cf/LAS composite material has the maximum effective bandwidth when it is 1:2.The reflection attenuation is less than-10 d B at 13.4-18 GHz when the composite thickness is 1.5mm,so the effective bandwidth is 4.6GHz.The complex dielectric constant of the SiC NW-Cf/LAS is closely related to the Debye dipolar relaxation process.The loss of the electromagnetic for Si CNW-Cf/LAS is based on the Debye dipolar relaxation,electronic polarization,interfacial polarization,etc.