Study On Synthesis Of Nickel Nanowires And Electromagnetic Interference Shielding Performance Of Their Composites

With the rapid development of modern science and technology in the age of electronic information,although it brings great changes to people's daily life and production,it generates a large number of electromagnetic radiation problems by the electronics which seriously affects the health of human body and the normal functioning of mechanical equipments.Therefore,preparing electromagnetic shielding materials with high comprehensive performance is the key way to solve such problems.As one of the ferromagnetic materials,metallic nickel is an excellent electromagnetic shielding material owing to its unique electrical,thermal,mechanical property,and chemical stability.When one-dimensional nickel nanowires are used as fillers,a conductive network is easily formed in the composite materials,and good electromagnetic interference shielding effectiveness can be obtained at a small content.Herein,Nickel nanowires(NiNWs)with different morphologies and sizes are synthesized first,then NiNWs and Graphene(GP)as the fillers to construct different structures composites,and the electromagnetic shielding performance,magnetic property,electrical and thermal conductivity of the composites are systematically studied.The specific work is as follows:1.NiNWs are synthesized by two different chemical reduction methods.The morphology and size of NiNWs are controlled by changing the molecular weight and concentration of Polyvinylpyrrolidone(PVP).According to the experimental results,the synthesis mechanism of NiNWs controlled by PVP is analyzed.Another experimental method without PVP is used to synthesize NiNWs under an applied magnetic field,in order to obtain the best process conditions for preparing NiNWs by studying the effects of different reaction parameters on the morphology of NiNWs comprehensively.2.Electromagnetic shielding composite materials with a thickness of 60 ?m are prepared by using NiNWs and GP as fillers and polyvinylidene fluoride(PVDF)as polymer matrix.And based on the results,the shielding effectiveness,magnetic property,electrical and thermal conductivity of composites are improved with increasing content of the NiNWs,and all these performances of NiNWs/GP/PVDF composites are better than the NiNWs/PVDF with the same content of NiNWs.The electromagnetic shielding mechanisms of various kinds of composites are investigated and compared according to the experimental results.The composites prepared by NiNWs synthesized under magnetic field have higher electromagnetic shielding effectiveness comparing with NiNWs synthesized with PVP controlled.The NiNWs/GP/PVDF composite has an EMI SE value of 68 d B in the frequency range of 8.2-12.5 GHz when the content of NiNWs is 9 wt%.3.The GP/NiNWs/GP of PVDF composites with sandwich structure are prepared by hot pressing,and it is explored that the influence of the composite structure on the shielding performance.The composites with sandwich structure are more conducive to absorb electromagnetic wave comparing with NiNWs/GP/PVDF.And based on the results,the electromagnetic shielding mechanism of the composites with sandwich structure is analyzed.When the content of NiNWs is 9 wt%,the shielding effectiveness of the sandwich composite is as high as 70 d B in the frequency range of 8.2-12.5 GHz.According to the results,NiNWs with different morphologies and sizes are synthesized by chemical reduction methods.The ultrahigh efficiency EMI shielding of as-prepared NiNWs/GP/PVDF,NiNWs/PVDF,and sandwich structure composites,combining with superb electrical,thermal conductivity,mechanical flexibility and chemical stability features,suggest the great potentials for wearable flexible electronics,healthcare devices,and electronic security.