Preparation And Properties Of The Ferrite/chopped Carbon Fiber Absorbing Composite Materials

Currently, the rapid development of electromagnetic wave technology give greathelp to science and technology and life. However, the problems of electromagneticradiation and electromagnetic interference affect the work of the electrical equipmentand the life of people seriously.Therefore, when we used the electromagnetic wavewidely, we should controlled the electromagnetic problems closely.However, theability to absorb electromagnetic radiation in the microwave frequency range is anarea where current technology lacks.Therefore, the specific interest of this thesis ismicrowave absorption of absorbing materials. Furthermore, absorbing/bearingintegration of structural absorbing materials is currently a hot research topic in thefield of absorbing materials. Many researchers have devoted to the development ofhigh-performance absorbing agent. Synthesis the multilayer functional structurematerials such as the absorbing agent,resin,fiber is a new thinking and direction.Ferrite has both the mechanisms of dielectric loss and magnetic loss, but the diel-ectric loss is very small, the magnetic loss is main. Because of the synthesis processis simple, short synthetic cycle, lower cost, the good absorption performance in highfrequency band,W-type ferrite take a widely attention. In the experiment, I synthesisW-type strontium ferrite by using sol-gel self-propagating combustion. By adjustingthe different PH value of sol and the calcination temperature of late ferrite precursorcan determine the optimum synthetic process for synthesis of W-type strontium ferrite.According to the optimal synthesis process, preparation of W-type hexaferrite dopedwith La3+can improve the electromagnetic paraments and magnetic so that we can getthe good electromagnetic performance of modified ferrite.In addition, choppedcarbon fiber belongs to the dielectric loss type absorbing agent. Because of the lowdensity, excellent weather resistance,the well chemical stability, so it is often used asthe function absorbing agent of structural absorbing materials. In this paper, choosingdifferent length and different mass fraction of chopped carbon fiber are added to theepoxy resin. According to the test results can select the best length, the best content ofchopped carbon fiber as a dielectric loss type absorbing agent. Structure absorbing material has three layers, including transmission layer, absorbing layer and thereflector. The transmission layer is including4-layer low dielectric non-alkali glassfiber composite with epoxy resin. The reflector is carbon fiber/epoxy resin, thespecification for180mm*180mm. Absorbing layer includes double-layer, one layer ischopped carbon fiber/epoxy resin composite material, another layer is W-typeferrite/epoxy resin composite material. By adjusting the thickness and sequence of thedouble-layer absorbing layer to determine the absorbing excellent performance ofabsorbing/bearing integration of functional composite materials.The results showed that the PH value of7in sol and the precursor calcinationtemperature of1200℃can get the typical W-type hexaferrite when synthesis W-typeferrite using sol-gel self-propagating combustion. When the doping amount of La3+was0.3, the chemical composition of Sr0.7La0.3Co2Fe16O27, its electromagneticparameters and magnetic has been optimized and the absorbing effect is best.Through the results of reflectivity, the electromagnetic loss effect is best when thelength of chopped carbon fiber is3mm. Different mass fraction of chopped carbonfiber have certain absorption under different electromagnetic band between the massfraction of0.1%and0.9%. Therefore, we can join the certain content of choppedcarbon fiber according to the needs of practical application. Ferrite and choppedcarbon fiber as absorbing agent, the epoxy resin as binder made for compositeabsorbing layer. When the chopped carbon fiber/epoxy resin as the outer layer and thethickness of0.5mm, ferrite/epoxy resin absorbing layer as the inner layer and thethickness of1.5mm, it performance excellent absorbing in8~20GHz maximumabsorption can reach-24.5dB.