Preparation And Microwave Absorption Properties Of Reduced Graphene Oxide-based Composites

The high-performance electromagnetic wave(EMW)absorption materials have great potential in both military and civil fields due to thin thickness,light weight,strong absorption intensity and broad bandwidth.Among the high-performance EMW absorption materials,graphene,owing to low density,ultrahigh surface area,excellent dielectric and mechanical properties and outstanding chemical stability,has become a research direction.However,the high dielectric constant makes its impedance matching extremely poor,causing a large number of EMW to be reflected.Therefore,graphene exhabits the weak EMW absorption performance.In this paper,with the aim of enhancing the impedance matching and EMW absorption properties of r GO,the effective method was the introduction of conductive polymers and core-shell nanoparticles into r GO matrix.Additionally,the epoxy resin-based EMW absorption materials were prepared by uniformly dispersing them into the epoxy resion matrix in order to measure the application value of powdered microwave absorbent,and the EMW absorption performance was also discussed.The details of research are as follows:(1)Reduced graphene oxide covalently grafted polyaniline(r GO-g-PANI)composites were synthesized by grafting of nanorod-like PANI on the surface of r GO by means of interfacial polymerization,in which r GO modified by aniline served as the reactivity point.The optimal microwave absorption performance was obtained with 30wt% of r GO-g-PANI in paraffin wax.The minimum RL could reach up to-45.2d B,and the effective absorption bandwidth covered 4.4GHz when the thickness of EMW absorbent was 3mm.The above results indicated that the grafting of PANI nanorod significantly improved the EMW absorption property of r GO.Of course,we made the comparison of the microwave absorption performance of r GO/PANI and r GO-g-PANI for the sake of highlighting the enhancement effect of grafting over physical adsorption,and discussed the mechanism.(2)Core-shell Co/NPC@Zn O nanoparticles were fabricated by the calcination of ZIF-67@Zn O,in which Co-based zeolitic imidazolate framework(ZIF-67)served as core and Zn O used as shell.The nanoparticles could exhabit the strongest absorption intensity when the dopant ratio in paraffin wax was 30wt%.Then,a three-dimensional network structure of r GO-coated Co/NPC@Zn O nanoparticles was prepared by the compound of GO and nanoparticles,followed by the reduction of hydrazine hydrate.The results suggested that the minimum RL was-45.4d B,and the effective absorption bandwidth could reach up to 5.4GHz.2mm of absorbent thickness was the highlight of Co/NPC@Zn O/r GO.The enhancement menchanism of Co/NPC@Zn O was also discussed in combination with r GO.(3)Although the above synthesized powdered absorbent shows the excellent EMW absorption performance,it does not have the universal applicability in engineering field.Therefore,the epoxy resin-based EMW absorption materials were constructed by uniformly dispersing the above powered microwave absorbent into epoxy resion matrix for the purpose of investigating its absorption on EMW in practical application.Then,pure EP was compared with EP/r GO-g-PANI and EP/Co/NPC@Zn O/r GO in the way of microwave absorption properties.The calculated result of EM parameters demonstrated that the introduction of the powered microwave absorbent could really enhance the EMW absorption performance of EP,and the enhancement effect of Co/NPC@Zn O was slightly superior to its of PANI nanorod.These researches provide the references for the application of r GO-g-PANI and Co/NPC@Zn O/r GO composites in engineering field.