Preparation And Electromagnetic Properties Of Magnetic Metal/Carbon Composites With The Two-dimensional Laminar Morphology

The two-dimensional lamellar carbon-based microwave absorbing composites compounded with magnetic metals have attracted much attention and research due to their small density,large specific surface area and certain high temperature resistance.In this paper,different kinds of magnetic metal/carbon microwave absorbing materials with the two-dimensional lamellar morphology were prepared by a sodium chloride template method and metal-organic frameworks（MOFs）as the precursor.And the morphology,phase composition and microwave absorption properties of the composites can be controlled by adjusting the addition of sodium chloride template and the metal contents in the composites.The research includes as follows:1.The mono-metallic Co/C and Fe/C composites with special two-dimensional lamellar morphology were successfully prepared by liquid phase synthesis and subsequent high-temperature thermal reduction process using sodium chloride as template,cobalt acetate and ferrous chloride as metal sources,and polyvinylpyrrolidone（PVP-k30）as carbon sources.By changing the metal content of Co and Fe,we are dedicated to regulating the morphology and structure of the Co/C and Fe/C composites,and optimizing the electrical loss and magnetic loss capacity.As for the Co/C composite,it shows an effective microwave absorbing bandwidth of 4.6 GHz（12.1-16.7 GHz）and the minimum reflection loss of-47.9 dB at a thickness of 2.0 mm.As for the Fe/C composite,it shows the better microwave absorption properties with an effective microwave absorbing bandwidth of 5.4 GHz（11.5-16.9 GHz）and the minimum reflection loss of-37.2 dB at the same thickness of 2.0 mm.2.The bimetallic ferrocobalt alloys/carbon composites with special two-dimensional lamellar morphology were successfully prepared by the NaCl template method using cobalt acetate and ferrous chloride as metal sources,and polyvinylpyrrolidone（PVP-k30）as carbon sources.By changing the relative contents of magnetic metal irons,we are dedicated to regulating the morphology,phase compositions,graphitization degree and microwave absorbing properties of the composites.The as-prepared bimetallic ferrocobalt alloys/carbon composites have displayed excellent microwave absorption properties.For example,the Co_0.1Fe_0.9/C composite shows the minimum reflection loss of–43.7 dB at a thickness of 1.6 mm.When the thickness increases to 1.7 mm,it shows a broad effective microwave absorbing bandwidth of 5.2 GHz.As for the Co_0.9Fe_0.1/C composite,it shows the minimum reflection loss of–54.7 dB at a thin thickness of 1.5 mm.When the thickness increases to 1.65 mm,it shows a broad effective microwave absorbing bandwidth of 5.4 GHz（12.6-18 GHz）.3.The bimetallic（Co,Zn）alloys/porous carbon nanocomposites（BPCNs）with special two-dimensional leaf-like morphology were successfully prepared derived from MOFs precursors and by subsequently high temperature reduction.The ZIFs composites with special two-dimensional lamellar leaf-like morphology were prepared by the liquid-phase self-assembly method.And Co as well as Zn nanoparticles can be well dispersed in the carbon skeleton without the formation of agglomeration.After high temperature reduction of the ZIFs precursors,the prepared BPCNs still retained the special two-dimensional leaf-like morphology and there was no collapse of the porous structure happened.Moreover,the prepared BPCNs exhibit excellent microwave absorption properties.When the relative content of Co comes up to 40%,the prepared BPCN-0.4 owns a broad effective microwave absorbing bandwidth of5.7 GHz at a thickness of 2.5 mm,and the minimum reflection loss can reach-47.9 dB.