Study Of Flexible Carbon Fiber Composite Materials And Electromagnetic Shielding Properties

With progress in science and technology over the years,various wireless communication devices(e.g.portable electronic devices,wireless devices,and cell phones)are gradually becoming miniaturized,which not only brings people a lot of convenience,but also brings serious electromagnetic interference(EMI).Therefore,the development of high-performance electromagnetic interference shielding materials is of great significance in commercial and military communications technology.Up to now,metals and metallic composites are the most widely used materials for EMI shielding.However,the high electrical conductivity of the metal will lead to secondary electromagnetic pollution that caused by the multiple reflections of the incident electromagnetic waves on metal surfaces.In addition,the high density,poor mechanical flexibility,poor corrosion resistance and expensive processing costs severely restricted their further applications.Therefore,a quest for developing a superior ultra-light EMI shielding material is still a research hotspot.In this paper,this subject chooses in-situ heat treatment to explore the direction of fiber modification.The main research contents and conclusions of the thesis are as follows:Cotton fiber is used as a carbon source,and it is immersed in a metal precursor solution and carbonized at high temperatures to prepare a cotton fiber-based carbon film.The mechanical properties are further improved through polyimide resin encapsulation.The prepared CCF@Co Fe/PI composite films integrate various intriguing attributes,including lightweight,favorable flexibility and tensile strength of 9?11 MPa,as well as superb EMI shielding performance of?32 dB over the X-band with the thickness of only 0.16 mm.Moreover,an EMI shielding efficiency of?62 dB can be achieved by overlapping 6 layer films with the thickness of no more than 1 mm.A flexible carbon fiber composite film by modification and carbonization of chopped carbon fiber.Due to the presence of polyimide resin,the prepared composite film has good mechanical properties.The tensile strengths of the CF@NiCo₂O₄/PI composite film obtained by carbonizing fibers at 400?and polyimide resin encapsulation and the CF@NiCo/PI composite film obtained by carbonizing fibers at 800?and polyimide resin encapsulation are 26 MPa and 12 MPa,respectively.Meanwhile,the addition of magnetic metal particles improves the electromagnetic shielding performance of the composite film.When the thickness is only 1.1 mm,the total electromagnetic shielding effectiveness of the CF@NiCo/PI composite film reaches?86 dB,which is close to the military-grade protection level.The composite film prepared in the paper has excellent electromagnetic shielding performance.Magnetic metal particles carbonized at high temperature were dispersed uniformly covered on the carbon skeleton,forming a unique structure.The magnetic particles and the conductive carbon skeleton can produce strong synergistic which is conducive to achieving high attenuation efficiency and extended bandwidth to improve the EMI shielding effectiveness.The lightweight and magnetic microporous carbon-based films not only exhibit excellent EMI shielding effectiveness but also show high-temperature resistance,all of which have a great potential in the application of commercial and military communication technology.