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