Preparation And Absorption Properties Of Ni Nanoparticles/Carbon Based Composites

Nickel(Ni)has been regarded as one of the most promising microwave absorbing materials due to its good magnetic loss,compatible dielectric loss,high Snoek limit,easy production,and abundant reserves.Based on the combination of self-developed nickel nanoparticles with core-shell structure and carbon materials,this thesis achieves multi-component synergy through structural regulation and component recombination strategies,improves impedance matching,and prepares high-performance microwave absorbers.In the past,the reflection loss of nickel-based composite materials is generally concentrated in the vicinity of high frequencies,and the low-frequency nickel-based absorbing materials are rarely studied.Therefore,aiming at this vacancy,this paper prepares different nickel/carbon composites to study their microwave absorption effect in the low frequency range.The specific research contents are as follows:1.Preparation and microwave properties of nickel/nitrogen doped porous carbon nanosheets:The Ni/C composite was prepared by sol-gel method and post-calcination method,in which urea was used as nitrogen source and citric acid was used as carbon source.The morphology characterization results showed that the nickel nanoparticles were evenly embedded on the carbon nanosheet,and the Carbon nanosheets are multilayer interconnected frames which had multilayer pore structure.At the filling ratio of 10 wt.%,the nickel/nitrogen doped porous carbon nanosheets achieve a maximum reflection loss of-49.07 d B at 5.6 GHz.The excellent microwave absorption properties of the nickel/nitrogen doped porous carbon nanosheets synthesized in this work will be discussed in detail from the aspects of synergistic effect,microstructure,etc.2.Preparation and microwave properties of nickel/carbon nanotubesCarbon nanotubes have attracted extensive attention due to their low density,high chemical stability,and interesting electrical properties.However,a single carbon nanotube as a microwave absorbing material has poor impedance matching and poor microwave absorption performance.Therefore,in order to improve its microwave absorbing properties,a simple hydrothermal method was used to prepare nickel/carbon nanotube composites,and the best microwave absorption effect was achieved when the ratio of nickel nanoparticles to carbon nanotubes was 1:2,shows a good absorption loss effect in multiple bands,reaching the best loss of-44.34 d B at 4.48 GHz,and the bandwidth reaches 4.08 GHz at 2.0 mm.The nickel/carbon nanotube composites synthesized in this work adopt a mild and simple synthesis method,and achieve a lightweight and efficient microwave absorption effect.3.Preparation and microwave properties of nickel/graphene oxide/carbon nanotubeNickel/graphene oxide/carbon nanotubes were prepared by a simple hydrothermal method.Electron microscopy studies showed that the nickel nanoparticles were uniformly dispersed on the graphene oxide nanosheets,and the carbon nanotubes were inserted into the nanosheets to form a continuous three-dimensional conductive network.Taking advantage of the synergistic effect between nickel nanoparticles with magnetic loss and graphene oxide/carbon nanotubes with dielectric loss,the Ni/GO/CNT composite achieves-42.06 d B at 6.4 GHz,which corresponds to a thickness of 4.5 mm.The purpose of this work is to explore a simple method to fabricate dispersed nickel nanoparticles/graphene oxide/carbon nanotube composites,which are candidates for high-performance microwave absorption in practical applications.