Elsevier

Journal of Alloys and Compounds

Volume 634, 15 June 2015, Pages 232-238
Journal of Alloys and Compounds

Fabrication of hierarchical graphene@Fe3O4@SiO2@polyaniline quaternary composite and its improved electrochemical performance

https://doi.org/10.1016/j.jallcom.2015.02.062Get rights and content

Highlights

  • Graphene@Fe3O4@SiO2@polyaniline hierarchical structures have been fabricated.

  • The reflection loss of the composites is below −10 dB in 10.5–16.3 GHz.

  • The maximum absorption of the composites is −40.7 dB at 12.5 GHz.

Abstract

Hierarchical graphene@Fe3O4@SiO2@polyaniline quaternary composite is fabricated subtly. Their microwave absorption properties are also investigated in the 2–18 GHz frequency range. Transmission electron microscopy (TEM) and scanning electron microscope (SEM) reveal that Fe3O4@SiO2@polyaniline core@shell@shell heteronanostructures are densely covered on the surfaces of graphene, and form hierarchical structures. Compared with two-dimensional binary nanocomposites of graphene@Fe3O4, the hierarchical structure exhibits enhanced EM absorption in terms of both the maximum reflection loss value and the absorption bandwidth. The maximum reflection loss value can reach −40.7 dB at 12.5 GHz with a thickness of 2.5 mm and the bandwidth corresponding to the reflection loss below −10 dB is 5.8 GHz (from 10.5 to 16.3 GHz).

Introduction

In recent years, microwave absorption materials (MAWAMs) have received increasing attentions due to their military and civil applications such as military countermeasure to radar detection and the reduction of electromagnetic pollution/radiation [1]. Hence, considerable efforts have been devoted to microwave absorption materials. The idea MAWAMs are required to have wide absorption frequency range, strong absorption properties, low density, good thermal stability, and antioxidant capability [2]. Traditional materials, such as carbon black, graphite and ferrite, cannot reach the standards due to their relatively low absorbing abilities and narrow bandwidth of absorption frequency [3]. Therefore, designing and fabricating new types of MAWAMs with effective electromagnetic wave absorption ability are highly demanded.

Graphene, a new class of two-dimensional carbon nanostructure, has attracted much attention for its unique physical, chemical, and mechanical properties [4]. Graphene possesses not only a stable structure but also high specific surface area and excellent electronic conductivity. These properties make graphene or graphene-based materials very promising as a new type lightweight MAWAMs [5]. Recently, graphene-based materials including graphene–Fe3O4 nanoparticles [6], graphene-bowl-like Fe3O4 hollow spheres [7], graphene–Co nanocrystal [8], graphene–PANI [9] nanocomposites have been utilized in electromagnetic absorption field, and all of them showed strong electromagnetic absorption properties. However, these research works mostly focus on graphene-based binary nanocomposites, only a few studies looked at constructing the graphene-based hierarchical structures by fabricating heteronanostructures on the side surfaces of graphene sheets. It is well-known that the absorption properties of a material are closely related to the structure of microwave absorber [10]. Recent advances show that excellent microwave absorption properties can be obtained from hierarchical nanostructures with complicated geometrical morphologies [11]. Herein, graphene-based hierarchical structures were constructed via fabricating Fe3O4@SiO2@polyaniline(PANI) core@shell@shell heteronanostructures on the surfaces of graphene. The morphology, microstructures, static magnetic properties and microwave absorption performances of the as-prepared hierarchical structures are also fully investigated.

Section snippets

Experimental

All of the chemicals and reagents were purchased from Sinopharm Chmical Reagent Co., Ltd, China and used as received. Deionized water was used for all experiments.

Results and discussion

The strategy for synthesizing graphene@Fe3O4@SiO2@polyaniline hierarchical structures is schematically depicted in Scheme 1. First, the surfaces of graphene were densely covered by uniform Fe3O4 nanoparticles via the reduction reaction between FeCl3 and DEG in the presence of GO, forming graphene@Fe3O4 nanocomposites. Then, Fe3O4 nanoparticles on surfaces of graphene were coated with SiO2 layer by the Stöber method to obtain graphene@Fe3O4@SiO2 nanocompostes. Finally, graphene@Fe3O4@SiO2

Conclusion

In conclusion, we have been constructed a new kind of graphene-based hierarchical structures, graphene@Fe3O4@SiO2@PANI, in which Fe3O4@SiO2@PANI heteronanostructures are densely covered on surfaces of graphene. When evaluated as microwave absorbers, the hierarchical structures exhibit excellent electromagnetic absorption properties including the strong absorption ability to electromagnetic wave and lightweight characteristics. The maximum reflection loss of the hierarchical structures is −40.7 

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