Preparation Of Fe₃O₄@c Composite Microsphere And Its Application In The Microwave Absorbing And Elecchemistry Fileds

This article sythesised Fe3O4@C composites，which was based on Fe3O4/Ccomposites, aimed at solving the problem of disproportion and uncontrollability ofcarbon content when composing Fe3O4with carbon. Fe3O4microspheressynthesized by hydro-thermal method was used as basis, Fe3O4@C, with500nmFe3O4microspheres as cores have been successfully prepared through in situpolymerization of phenolic resin on the Fe3O4surface and subsequenthigh-temperature carbonization. The thickness of carbon shell, from20nm to60nm, can be well controlled by modulating the weight ratio of resorcinol and Fe3O4microspheres. It was used to have application in microwave absorption andelectrochemistry fields. Carbon microspheres hollow with the thinnest carbonlayer were ultimately obtained on the basis of the Fe3O4@C composites, and wereapplied to supercapacitor field.In this article, X-ray diffraction was used to characterize the crystalling phaseof the materials, and the results showed that the original crystalling phase of thecompound microballoon of Fe3O4@C can be maintained, when carbonized under600oC and650oC, while under700oC would be altered. Scanning electronicmicroscope and transmission electronic microscope were applied to characterizethe appearance and the carbon thickness of the materials, and the results provedthat the thickness of carbon shell can be well controlled by modulating the weightratio of resorcinol and Fe3O4microspheres Raman spectra were performed torepresent the graphitization degree of the sample, and the results indicated that thegraphitization of the sample was identical with different value of carbon contents.The thermogravimetric analysis was carried out the theoretical contents of carbonin the composite materials, and the results showed that the practical contents ofcarbon in the materials was lower than theoretical contents, due toautopolymerization of resorcinol and formaldehyde and generation of low-gradepolymer. Vibrating sample magnetometer was applied to characterize the magneticproperties and saturated magnetization intensity of the samples, and the resultsdisplayed that the carbon shell will not affect the magnetic nature of thecomposites, but just lower the content of Fe3O4microspheres.An HP-8722E vectornetwork analyzer was applied to determine the relative permeability andpermittivity in the frequency range of1-18GHz for the calculation of reflectionloss, and the optical performance was found in Fe3O4@C composite materialscarbonized under650℃. And finally, electrochemistry tester was used to test theelectrochemistry property and the results showed that the Fe3O4@C composite materials can perform strong cyclical stability, when used as cathode activematerial.