Preparation And Microwave Absorbing Properties Of Lightweight Carbon-Based Magnetic Composite Fibers By Electrospinning

The electromagnetic interference and pollution caused by the widespread use of electronic products such as mobile phones,computers,remote sensors,and radars seriously threaten public health and the environment.Innovation and application of high-performance electromagnetic wave absorbing materials is one of the important ways to solve this problem.Carbon-based materials as dielectric loss-type absorbing materials are often used in the field of electromagnetic wave absorption due to the wide range of raw materials,simple preparation processes,light weight,and excellent chemical stability.However,when carbon material is used as absorbing material,it still has the disadvantages of poor impedance matching and low absorption strength.The non-equilibrium molecular dynamics simulation based on the electromagnetic loss mechanism and the development of enhanced electromagnetic attenuation materials by combining dielectric and magnetic loss materials are of great significance for expanding the application of electromagnetic wave absorbing materials.In this thesis,carbon/metal and carbon/alloy composites were prepared using carbon fiber as the matrix and electrospinning combined with in-situ reduction technology.SEM and TEM were used to analyze the microscopic morphology of the composite,and XRD,FTIR,Raman,and XPS were used to analyze the composite structure,the magnetic properties of the composite materials were measured using VSM,and the absorbing properties of the materials were characterized by VNA.The findings are as follows:1.Porous carbon nanofibers were prepared by the PAN/PVP co-spinning method.The results show that the prepared carbon nanofibers are continuous and porous.As the carbonization temperature increases,the degree of graphitization of the material gradually increases.At the same thickness,the RL values corresponding to different samples show a trend of increasing first and then decreasing.When the carbonization temperature is800?,it shows the best absorbing performance.When the sample thickness is 4 mm in the range of 2-18 GHz,the RL of porous carbon nanofibers reaches-43.5 dB,and the effective absorption bandwidth?RL<-10 dB?is 9.8 GHz.2.C/Co nanofibers were prepared by electrospinning combined with in situ reduction technology.The results show that the increase of metallic Co content will form granular protrusions on the surface of carbon fibers.C/Co nanofibers exhibit typical ferromagnetic behavior.As the Co content increases,the saturation coercivity increases from 10.1 emu/g to 23.9 emu/g and the corresponding coercive force increases from 504.6Oe to 701.1 Oe.With the increase of Co content,the electromagnetic wave absorption performance shows a trend of first enhancement and then decrease.When the Co content is 15 wt.%,the C/Co nanofibers show the best impedance matching and attenuation ability,The effective absorption bandwidth in the range of at 2-18 GHz reaches 12.9 GHz,covering most of the C band and the entire X-Ku band.The minimum reflection loss(RL_min)at a thickness of 3.5 mm reaches-58.8 dB.3.PAN/FeCo nanofibers were prepared by electrospinning method,and carbonized at 800?for 2h under nitrogen atmosphere to obtain C/FeCo nanofibers.The FeCo particles formed in situ were uniformly dispersed along the carbon nanofibers skeleton and surrounded by an ordered graphite layer.The saturation magnetization and coercivity of C/FeCo nanofibers increase with the increase of FeCo content,and its saturation magnetization increases from 8.1 emu/g to 30.4 emu/g,and the corresponding coercivity increases from 179.9 Oe to 266.3 Oe.The reflectance of C/FeCo nanofibers increases with FeCo alloy content first and then decreases.When the FeCo alloy content is 20 wt.%,The minimum reflection loss(RL_min)measured at a thickness of 2.7 mm is-98.4 dB,and its effective absorption bandwidth is 10.2 GHz,covering the entire X-band and Ku-band.The result shows that C/FeCo-20 nanofibers have the best impedance matching.