Preparation Of Reduced Graphene Oxide-doped Ferrites-polyaniline Nanocomposites And Their Microwave Absorption Performance

The increasingly development of electronic products not only meets people’s living requirements,but also promotes innovation of military installation and weaponry.However,the subsequent electromagnetic pollution becomes potential threat which is harmful for health and social production.Thus,it has been a research focus to obtain light weight,efficient and easily prepared microwave absorption material.Graphene(RGO)which has light density,larger specific surface area,high conductivity and dielectric loss;Ferrites possess simple preparation and high magnetic loss.Moreover,doped ferrites with rare earth elements can change the infield and electromagnetic parameters of ferrites,which is beneficial for microwave absorption performance;Polyaniline(PANI)is a conductive polymer which has nice physical-chemical stability and dielectric loss.Based on this analysis,synthesize a composite with graphene,ferrite and polyaniline,which is possible to gain microwave absorption material with high dielectric loss and magnetic loss.In this study,three different kinds of graphene-doped ferrite-polyaniline were synthesized via different methods and processes.The phase,morphology,structure and performance were investigated by XRD,FT-IR,Raman,FESEM,HRTEM,VSM and vector network analyzer.Meanwhile,we studied the effects of impedance matching,loss factors and thickness on microwave absorption performance.Specific works as follow:(1)The RGO/NCZF/PANI nanocomposites were prepared by hydrothermal and in-situ polymerization.The ferrite nanoparticles with an average grain size of 30~50 nm attached to the graphene sheets,and then RGO/NCZF binary nanocomposites were coated by PANI,which generated a nice composite structure.The magnetic performance was enhanced by the Ce and Zn doping.The saturation magnetization of composite decreased gradually with the increase of graphene.When the ratio of m(GO):m(NCZF)was 5 %,the RGO/NCZF/PANI-1 displayed the best microwave absorption performance.The minimum reflection loss(RL)was-38.6 dB located at 16.4 GHz with an effective absorption bandwidth of 3.8 GHz and a thickness of 6 mm.Besides,the frequency of the minimum RL shifted towards low frequency because of the electromagnetic cancellation effect.(2)The RGO/SNCF/PANI nanocomposites were prepared by sol-gel,self-assembly and in-situ polymerization.The ferrite particles distributed on the surface of graphene with a little agglomeration.The substitution of Nd and Co resulted in unequivalence doping and magnetic moment changes,which lead to the charge transformation in ferrites and the increase of dielectric loss and magnetic loss.Based on the transmission line theory,when the ratio of m(GO):m(NCZF)was 6 %,the RGO/SNCF/PANI-2 possessed the best relative input impedance,which resulted in the most excellent microwave absorption performance.The minimum RL is-42.8 dB located at 14.56 GHz with an effective absorption bandwidth of 5.7 GHz and a thickness of only 2 mm.(3)The RGO/SNCF/NCZF/PANI nanocomposites were prepared by hydrothermal,in-situ polymerization and self-assembly.Square shape NCZF and hexagonal shape SNCF particles were coated by rodlike PANI.The SNCF/NCZF/PANI composites interspersed between the RGO sheets to formulate quaternary nanocomposites.The dielectric loss factor was obviously enhanced because of the high conductivity of RGO and PANI,which not only increased the dielectric loss of nanocomposites,but also made up the weakness of low dielectric loss of ferrites.When the ratio of m(GO): m(NCZF)was 11 %,the RGO/SNCF/NCZF/PANI-3 has the minimum RL of-41.6 dB located at 6.8 GHz with an effective absorption bandwidth of 3.2 GHz and a thickness of 5 mm.In addition,nearly each samples had two effective absorption bandwidths which located in 4~8 GHz and 12~18 GHz.It indicated that RGO/SNCF/NCZF/PANI nanocomposites with an appropriate ratio and the thickness were possible to show an outstanding microwave absorption performance in the whole 2~18 GHz.