Elsevier

Materials Letters

Volume 186, 1 January 2017, Pages 78-81
Materials Letters

Conductivity and electromagnetic interference shielding of graphene-based architectures using MWCNTs as free radical scavenger in gamma-irradiation

https://doi.org/10.1016/j.matlet.2016.09.086Get rights and content

Highlights

  • A green approach for synthesis of three dimensional graphene architectures.

  • MWCNTs were used to reduce free radicals during irradiation process.

  • Two kinds of conductive networks in the architecture were made up.

  • The conductivity and shielding properties had improved significantly.

Abstract

In this work, we reported a green approach for synthesis of large-scale and low cost three dimensional graphene/polyacrylamide/multi-walled carbon nanotubes (3DGPW) architectures by γ–ray irradiation. Multi-walled carbon nanotubes were used to reduce free radicals and avoid defects brought into graphene during irradiation process. Meanwhile two kinds of conductive networks in the architecture were made up by graphene sheets and multi-walled carbon nanotubes. With the help of free radical scavenger and two kinds of conductive network structures, a remarkable conductivity of 3344.5 S/m was achieved for 3DGPW, which was 20 folds higher than that achieved for three dimensional graphene/ polyacrylamide architectures. In addition, the average value of the electromagnetic interference shielding increased from 9.8 to 24.6 dB. Therefore, the designed 3DGPW architectures could be considered as promising candidates for applications electromagnetic interference shielding materials.

Introduction

Recently, 3D graphene-based macroscopic architectures have been successfully synthesized by various methods, e.g., chemical vapor deposition on matrix foams [1], three-dimensional printing [2], self-assembly [3], [4], aerosolization [5] etc. Among them, they usually involve bottleneck problems like high temperature, inefficiency, valuableness, use of a great number of chemical reagent or small scale production. Gamma ray (γ-ray) irradiation has been broadly used in hydrogel preparation, exfoliation and the reduction of modified graphene sheets [6]. As a mature non-contact technique to combine the simple processes, γ-ray irradiation, exhibits many advantages, e.g. mild conditions, easy scaled-up production, high purity, economic benefits, no chemical residues and great penetrating power with ultra-uniformity [7], [8]. But during the irradiation process, the average size of sp2 carbon domains decreased, which were induced by the formation of small graphitic domains. More defects were brought into graphene sheets and largely disordered structures were formed during the irradiation process, which are main challenges to overcome.

Martinez et al. [9] found that gamma irradiated MWCNTs could react with the free radicals generated in the irradiation process. It had also been reported that MWCNTs could be used for shielding rays and quenching the free radicals [10]. Therefore, it was believed that MWCNTs could reduce free radical under the irradiation environment.

On this basis, we used MWCNTs as free radical scavenger and presented a new, green and one-step approach to engineer advanced 3D graphene/polyacrylamide/MWCNTs (3DGPW) architectures via γ-ray irradiation. The electrical conductivity and electromagnetic interference (EMI) shielding property of the products were investigated systematically.

Section snippets

Experimental

Graphite oxide (GO) aqueous solution of 300 mL 10.0 mg/mL and 3 g acrylamide (AM) powder were mixed with MWCNTs under stirring for 0.5 h in a glass tube. The details of 3DGPW preparation were described in supplementary materials. Then the mixture were irradiated with a 60Co γ-ray in airtight-capped glass vessels. The irradiation dose was accumulated to 100 kGy with a dose rate of 0.5 kGy/h. The 3DGPW/N2 architectures were obtained by thermal-annealing process at 700 °C for 2 h in N2 atmosphere with a

Results and discussion

The prepared 3D graphene architectures hydrogels after freeze drying showed a spongy and black appearance as presented in Fig. 1a (insert). SEM micrographs of 3D graphene architectures (Fig. 1a) revealed a characteristic 3D network composed of graphene, PAM and MWCNTs. The macropores were uniform with honeycomb-like structures. Higher resolution SEM image (Fig. 1b and c) showed that the pore walls consist of thin layers with graphene sheets and MWCNTs..

XRD patterns were shown in Fig. 2a. The

Conclusion

As three dimensional graphene materials were currently being explored for a broad range of applications, γ-ray irradiation technique undoubtedly provided a large-scale engineered and high purity for graphene self-enhancement materials. MWCNTs serving as free radical scavenger could reduce the number of radicals generated in irradiated process, and two kinds of conductive networks in the architecture were made up by graphene sheets and MWCNTs simultaneously. Consequently, a remarkable

Acknowledgments

The work was funded by the National Natural Science Foundation of China (11575126, 51502202), the Natural Science Foundation of Tianjin (16JCZDJC37800) and the Science and Technology Plans of Tianjin (15PTSYJC00230).

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These authors contributed equally to this work.

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