Synthesis And Electromagnetic Properties Of Polyaniline Fiber/Li-Zn Ferrite Composites

With the development in the research of electromagnetic shielding and stealth technology,high-performance microwave-absorbing material,featured with negligible thickness,light weight,wide band and strong absorption,has become a focus of research in the field of defense industry and civil technology.Compared with traditional single absorbing materials,organic/inorganic microwave-absorbing composite material has a variety of electromagnetic wave losses and performance superiority,and has been extensively studied for recent years.Most of researches have been focused on core-shell composite materials,but the shell has shielding effect on the nuclear layer.In order to give full play to the absorbing properties of each component,this paper designs a kind of fiber-grafted structure of polyaniline fiber/lithium zinc ferrite composite materials(PANI fiber/LZFO),and carried out research work as follows.First,spinel-type lithium zinc ferrite oxide(Li0.35Zn0.3Fe2.35O4)was prepared by sol-gel method,and PANI fiber/LZFO doped with hydrochloric acid,sulfuric acid and nitric acid was prepared by the interfacial in-situ polymerization method and the effect of the type of doped acid on microstructure,morphology and electromagnetic properties were studied.The results showed that the fiber-grafted structure of PANI fiber/LZFO doped with HCl was clearest.And the aspect ratio of PANI fiber was the largest,which the diameter was 75~90nm and the length was 710~800nm.Compared with the core-shell structure,the microwave absorbing performance of PANI fiber/LZFO is better,that the absorption bandwidth is 5.6GHz and the maximum reflection loss can be increased from-21.4dB to-45.3dB.Second,influence of hydrochloric acid on the microcosmic appearance and electromagnetic performance of the PANI fiber/LZFO EMW absorbing material had been studied by changing the concentration of hydrochloric acid.The results showed that the PANI fibers undergone dendritic growth in the process of graft polymerization on the ferrite oxide surface.The magnetic loss of the composite increased with the increase of hydrochloric acid concentration,and its dielectric loss decreased with the rise of the hydrochloric acid concentration.When concentration of hydrochloric is 1.5mol/L,composite of PANI fiber/LZFO with good grafting structure and microwave absorbing performance can be made.Its peak reflection loss of-51.3dB and effective absorption bandwidth of 5.88 GHz could be achieved at the frequency of 17.4GHz.Finally,the influence of Each component on micro morphology,structure and magnetic properties of PANI LZFO/fiber composite materials had been explored by adjusting the ratio of aniline monomer to ferrite oxide composite(An: LZFO)in preparing the composite material.And optimal process of PANI fiber/LZFO preparation had been developed.Experimental results showed that the fiber grafting structure of PANI fiber/LZFO composite could introduce a variety of new loss mechanisms,and this is conducive to the improvement of the absorbing performance.Furthermore,the absorbing performance can be adjusted and optimised by changing the ratio of aniline monomer to LZFO as well as the thickness of the absorption layer.Electromagnetic and wave absorbing properties of PANI fiber/LZFO composites are best when the ratio of aniline monomer to LZFO was 1:10.