The Design And Preparation Of Nanostructured Cobalt-based/carbon Composite Absorbing Material

Due to the rapid development of modern science and technology and the popularity of electronic products, the electromagnetic pollution has drew extensive attention to people. Because of the high absorption of electromagnetic radiation and higher efficiency which compared with electromagnetic shielding materials,absorbing materials become a major way of preventing electromagnetic pollution.In this article, on the basis of studying the principle of absorbing and contrast the advantages and disadvantages of different species of absorbing materials, Co@C composite material is used as electromagnetic wave absorber and been studied.According to the existing problems of this kind of materials synthesis now, a new synthesis idea is put forward to improve the synthetic method in this article.Using the hydro-thermal method and in-situ polymerization method, the Co CO3@PANI with spindle shape has been prepared. Via the high temperature carbonization under the atmosphere of N2/H2, Co CO3@PANI has been changed to Co@C with core-shell structure. Co@C composite particles which using this method of synthetic can keep with the same precursor morphology and has good stability. By adjusting the quantity of coated carbon and the carbonization temperature, the permittivity and permeability of composite material are improved to optimize the impedance matching characteristics, which can make the composite material have good wave absorbing properties. This article shows that,when the carbonization temperature is 650 o C and the mass ratio of precursor and aniline is 1:1, Co@C composite particles has the best wave absorption performance. The maximum reflectivity value of this sample is-20.5 dB, and the effective bandwidth(<-10 d B) is 5.5 GHz.On the basis of the preparation of Co@C with spindle shape, in order to further improve the electromagnetic wave absorption performance of the sample system, Fe is introduced in the system to generate Cox Fey@C composite particles.By adjusting the cobalt carbon ratio of Cox Fey@C, the permittivity and permeability of composite material are improved to optimize the impedance matching characteristics, and wave absorption performance can be better. This article shows that, when the ratio of cobalt and iron is 2:1, Cox Fey@C composite particles has the best wave absorption performance. The maximum reflectivity value of this sample is-25.5 dB, and the effective bandwidth(<-10 d B) is 6GHz.Finally, by changing the synthesis methods of precursor, the Co@C with flower shape has been prepared to explore the effect of absorbing performancewhen the morphology of composite particles has changed. The study founds that,due to the complexity and vulnerability of sample in morphology, the particle size uniformity and dispersion get worse after Co@C composite particles has been prepared.Because of it the sample with flower shape has low permittivity and wave absorption performance.