Elsevier

Materials Letters

Volume 264, 1 April 2020, 127342
Materials Letters

Hierarchical N, S-codoped honeycomb-like porous C@Co9S8@CNTs structure as high-performance microwave absorber

https://doi.org/10.1016/j.matlet.2020.127342Get rights and content

Highlights

  • N, S-codoped honeycomb-like porous C@Co9S8@CNTs structure was prepared.

  • Hierarchical structure is the key factor for a high-performance microwave absorbing.

  • The reflection loss <−10 dB of the hierarchical structure was 4.64 GHz.

  • The maximum absorption of the hierarchical structure was −56.0 dB.

Abstract

Herein, a facile method is developed to fabricate hierarchical N, S-codoped honeycomb-like porous C@Co9S8@CNTs composites, in which the coating length of carbon nanotubes (CNTs) on the surface of comby porous carbon framework could be easily controlled by the addition of cobalt chloride content in precursor. When the addition of cobalt chloride was 0.26 mmol, the longer CNTs with length of 3.1 µm was formed, which induced have significantly on enhancement of the comprehensive microwave absorption properties of hierarchical N, S-codoped honeycomb-like porous C@Co9S8@CNTs structure. By adding only 10 wt% to paraffin, the resulting composites exhibited a maximum reflection loss of −56.0 dB at 6.5 GHz with 3.4 mm thickness, and the effective bandwidth was 4.64 GHz (5.60–7.76, 15.52–18 GHz). These outstanding microwave absorption properties were ascribed to the stronger dielectric loss by the higher aspect ratio of the CNTs. This work would provide a new direction how to design porous carbon-based microwave absorbers with high performance at low filler loading.

Introduction

With the speedy development of civil and military communication technologies, the electromagnetic (EM) interference problem has evolved to be a new kind of pollution source [1], [2], [3]. High performance microwave absorbers with lightweight, low intensity, broadband absorption and strong absorption capacity, have gained great attraction because they can effectively convert EM wave energy into thermal and alleviate the EM wave pollution issues. Previous works have already proved that constructing carbon-based hierarchical structures is a useful strategy to obtain high performance microwave absorber [4], [5], [6], [7]. Among them, hierarchically porous carbon-based composites have attracted growing interests because of their relatively lower density and high dielectric loss. However, a major concern for these absorbers lies in that the high filler loading in matrix (≥30 wt%) would lead to the high specific gravity of absorption coating and be detrimental to their further real application.

To meet the lightweight requirement, it is very necessary to rationally design the architecture carbon-based hierarchical composite and modulate its structure. Herein, we propose a facile template approach to fabricate honeycomb porous C@Co9S8@CNTs composites with hierarchical structure by pyrolysis of sucrose, thiourea and cobalt chloride in the existence of NaCl template. In the pyrolysis process, Co9S8 particles were in situ generated in porous carbon framework and then catalyzed the growth of CNTs on surface of porous carbon framework, producing hierarchical structure. Furthermore, the length of CNTs could be easily adjusted by changing the addition of cobalt chloride content, and thus the corresponded microwave absorption was controlled.

Section snippets

Experimental

The preparation process and the structural characterization of hierarchical N, S-codoped honeycomb-like porous C@Co9S8@CNTs composites, and electromagnetic parameter measurements are displayed in the Supporting Information.

Results and discussion

As shown in Fig. 1a, hierarchical N, S-codoped honeycomb-like porous C@Co9S8@CNTs composites were obtained by pyrolysis of sucrose, thiourea and cobalt chloride in the existence of NaCl template. Here, NaCl is served as a template to produce porous framework, and sucrose is used as carbon precursor during the pyrolysis process. Furthermore, NH3 and H2S released from thiourea during pyrolysis process, act as sulfurization and nitrogen dopant to react with Co2+ and sucrose, thereby forming Co9S8

Conclusions

In summary, hierarchical N, S-codoped honeycomb-like porous C@Co9S8@CNTs composites have been successfully synthesized through a facile template method. The electromagnetic parameters showed that the length of CNTs on comby porous carbon framework had significantly on the samples’ microwave absorbing properties, and the N, S-codoped honeycomb-like porous C@Co9S8@CNTs composites that possessed a longer length of CNTs displayed superior comprehensive microwave absorption properties in the terms

CRediT authorship contribution statement

Xiaoyu Bai: Validation, Investigation. Lei Wang: Conceptualization, Methodology, Data curation, Writing - original draft, Writing - review & editing, Visualization, Supervision, Project administration. : . Ying Lin: Resources, Funding acquisition.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work is supported by the Scientific Research Starting Foundation of Shaanxi University of Science and Technology (Grant No. 2017QNBJ-04) and Science and Technology Foundation of Shaanxi Province (Grant No. 2018JM5010 and 2018JQ5149).

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