Research Article
Construction of three-dimensional hierarchical porous nitrogen-doped reduced graphene oxide/hollow cobalt ferrite composite aerogels toward highly efficient electromagnetic wave absorption

https://doi.org/10.1016/j.jmst.2022.05.050Get rights and content

Highlights

  • NRGO/hollow CoFe2O4 composite aerogels were constructed by a facile two-step route.

  • The prepared composite aerogels showed a 3D hierarchical porous network structure.

  • EM absorbing capacity was regulated by the ferrite structure and addition amounts.

  • Strong absorption, wide bandwidth, thin thickness and low loading were achieved.

  • The potential EM dissipation mechanism of attained composite aerogels was proposed.

Abstract

The development of graphene-based composites with low density, robust absorption, wide bandwidth and thin thickness remained a great challenge in the field of electromagnetic (EM) absorption. In this work, nitrogen-doped reduced graphene oxide/hollow cobalt ferrite (NRGO/hollow CoFe2O4) composite aerogels were constructed by a solvothermal and hydrothermal two-step route. Results demonstrated that the as-fabricated composite aerogels had the ultralow density and a unique three-dimensional (3D) network structure, and lots of hollow CoFe2O4 microspheres were almost homogeneously distributed on the wrinkled surfaces of lamellar NRGO. Moreover, superior EM absorbing capacity could be achieved by modulating the ferrite structure, addition amounts of hollow CoFe2O4 and thicknesses. It was noteworthy that the NRGO/hollow CoFe2O4 composite aerogel with the addition amount of ferrite of 15.0 mg possessed the minimum reflection loss of -44.7 dB and maximum absorption bandwidth of 5.2 GHz (from 12.6 to 17.8 GHz) at a very thin thickness of 1.8 mm and filling ratio of 15.0 wt.%. Furthermore, the possible EM attenuation mechanism had been proposed. The results of this work would be helpful for developing RGO-based 3D composites as lightweight, thin and highly efficient EM wave absorbers.

Introduction

With the rapid development of 5G communication technology and the wide application of electronic devices, artificial electromagnetic (EM) radiation pollution exists in our living environment that not only reduces the life of the instrument but also harms the health of human beings [1,2]. Thus, developing highly efficient EM wave absorbing materials with low density, robust absorption, broad band and thin thickness has become a research focus in the field of functional materials [3,4].

Recently, reduced graphene oxide (RGO) has been considered as an ideal candidate for EM attenuation owing to the high specific surface area, excellent mechanical strength, low density and notable dielectric loss [5], [6], [7], [8]. Nevertheless, the excessive electrical conductivity of RGO cannot satisfy the requirement of impedance matching, resulting in poor absorption and strong reflection of incident EM waves [9,10]. As a consequence, the mismatched impedance and no magnetic loss greatly hinder the practical application of RGO in the field of EM absorption.

As a kind of spinel ferrites, cobalt ferrite (CoFe2O4) has been reported as the EM wave absorbent due to its facile synthesis, low cost and moderate magnetic loss [11], [12], [13]. Unfortunately, the drawbacks like narrow bandwidth, weak absorption and large density limit the potential application of CoFe2O4 as a lightweight and high-efficiency EM absorber [14,15].

Previous investigations have demonstrated that the compound of RGO with cobalt ferrite for preparing the RGO/CoFe2O4 composites could be an effective route to improve the EM wave attenuation capacity of RGO [16,17]. Although the prepared RGO/CoFe2O4 composites possessed the robust EM absorbing capacity owing to improved impedance matching and enhanced interfacial polarization loss, the thick matching thickness, high density and large filling ratio still hinder their practical application. Therefore, it is of great importance for fabricating RGO/CoFe2O4 composites with special structure to reduce the density, filling ratio and matching thickness of absorbers.

In the present study, nitrogen-doped reduced graphene oxide/hollow cobalt ferrite (NRGO/hollow CoFe2O4) composite aerogels with the three-dimensional (3D) network structure and ultralight feature were constructed by the facile solvothermal reaction and subsequent hydrothermal self-assembly process. Significantly, the as-fabricated NRGO/hollow CoFe2O4 composite aerogels presented a unique hierarchical porous structure, which was constructed by introducing the macropores stacked from the adjacent NRGO sheets and mesopores of hollow CoFe2O4. Moreover, the effects of ferrite structure and addition amounts on the EM wave absorbing properties of NRGO/CoFe2O4 composite aerogels were examined. Furthermore, the attained NRGO/hollow CoFe2O4 composite aerogels had good dispersion of ferrite microspheres, and achieved both robust absorption and wide bandwidth at a very thin thickness and low filling ratio. Additionally, the probable EM attenuation mechanism was revealed. Therefore, the prepared NRGO-based magnetic composite aerogels would be employed as potential lightweight and high-efficient EM absorbents.

Section snippets

Experimental

The detailed construction and characterization of NRGO/CoFe2O4 composite aerogels could be found in the electronic supplementary materials. For convenience, the prepared NRGO/hollow CoFe2O4 composite aerogels with the addition amounts of hollow CoFe2O4 of 5.0 mg, 15.0 mg and 30.0 mg were named S1, S2 and S3, separately. For comparison, the NRGO/solid CoFe2O4 composite aerogel (S4) was prepared by the similar procedures with the addition of 15.0 mg solid CoFe2O4.

The schematic construction

Structural investigation

In order to examine the crystal structure of the samples, the X-ray diffraction (XRD) characterization was performed. As depicted in Fig. 2(a), the hump diffraction peak at around 25.0° for all samples can be ascribed to the (002) plane of RGO. Furthermore, the characteristic peaks appear at 2θ = 30.1°, 35.4°, 43.1°, 56.8° and 62.6°, corresponding to (220), (311), (400), (511) and (440) crystallographic planes of CoFe2O4 (JCPDS No.22-1086), separately [18,19]. Besides, the diffraction peaks of

Conclusions

In conclusion, NRGO/hollow CoFe2O4 composite aerogels were fabricated by the solvothermal reaction and subsequent hydrothermal process. The prepared NRGO/hollow CoFe2O4 composite aerogels presented the extremely low density and special 3D hierarchical porous netlike structure, which was formed by the stacking of adjacent NRGO lamellas covered with numerous hollow CoFe2O4 microspheres. Moreover, results revealed that the EM absorbing performance was notably influenced by ferrite structure and

Supplementary material

Supplementary data associated with this article could be found in the attachment.

CRediT authorship contribution statement

Jing Xu: Writing – original draft, Data curation, Investigation. Ruiwen Shu: Conceptualization, Methodology, Validation, Writing – review & editing, Funding acquisition, Resources. Zongli Wan: Software, Investigation. Jianjun Shi: Resources, Supervision.

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.

Acknowledgments

This work was financially supported by the Foundation of Provincial Natural Science Research Project of Anhui Colleges (No. KJ2021ZD0047), the Anhui Provincial Natural Science Foundation (No. 2008085J27), the China Postdoctoral Science Foundation (No. 2019M652160) and the Research Foundation of the Institute of Environment-friendly Materials and Occupational Health (Wuhu), Anhui University of Science and Technology (No. ALW2020YF05).

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