Hierarchical flower-like Fe3O4/MoS2 composites for selective broadband electromagnetic wave absorption performance

https://doi.org/10.1016/j.compositesa.2019.105760Get rights and content

Highlights

  • The Fe3O4/MoS2 composites are synthesized via a facile hydrothermal method.

  • The EAB of 6.1 GH at thin thickness of 2.0 mm could be obtained.

  • For the low frequency of C and X bands, the 100% coverage can be realized.

Abstract

The brilliant electromagnetic wave (EMW) absorbers are urgent with the extensive attention of electromagnetic pollution. Herein, the binary Fe3O4/MoS2 composites are successfully synthesized via a facile hydrothermal method, where the different morphologies of 3D MoS2 nanoflowers decorated with the monodispersed Fe3O4 particles by tailoring the molar ratio of Fe3O4 to MoS2. Moreover, we find that the dielectric/magnetic loss and good impedance matching have dramatically contributed to the enhanced EMW absorption ability for binary Fe3O4/MoS2 composites compared to pristine Fe3O4 nanoparticles. Meanwhile, the effective absorption bandwidth (EAB, RL < −10 dB, > 90% absorption) of 6.1 GHz at thin thickness of 2.0 mm could be obtained while it exhibits the strongest minimum reflection loss (RLmin) of −64.0 dB with ultra-thin thickness of 1.7 mm. Noticeably, even for the low frequency of C (4–8 GHz) and X (8–12 GHz) bands, the 100% frequency occupy ratio can be realized while the RL intensity is still not severely deteriorated, which is superior than most of MoS2-based absorbers that have been reported so far. Hence, it can be expected that the Fe3O4/MoS2 composites in this work featured with strong absorption intensity, selectable wide bandwidth (especially for 100% coverage both for C and X bands) as well as ultra-thin thickness (EAB of 6.1 GHz at 2.0 mm) will ensure it an attractive EMW absorber.

Introduction

With extensive attention of electromagnetic (EM) pollution, the excellent EM wave absorbents that featured with excellent attenuation intensity and wide bandwidth at a thin thickness have been received a flourish of interest in recent decades [1], [2], [3]. Up to now, numerous candidates, including carbon materials [4], MXene [5], metal alloys [6], conductive polymers [7], metamaterial [8] and magnetic ferrites [9], [10], have been extensively explored.

Among these absorbers, magnetic ferrites such as Fe3O4, is a representative candidate for high-performance EMW absorbers profiting from its large constant magnetic moment, good conductivity, decent permittivity and high Curie temperature, which benefit to both magnetic loss and dielectric loss [9]. In spite of excellent absorption property, the obvious drawbacks of high density, large loading content and poor impedance matching as well as narrow effective absorption bandwidth (EAB) originated from Snoek’ limit, hinder their practical applications. To break such obstruction, an efficient combination of magnetic Fe3O4 nanoparticles with other appropriate dielectric materials, especially two-dimensional (2D) dielectric materials such as MXenes [11], graphene [12], transition-metal dichalcogenides (TMDs) [13], and the like, have been considered to be a promising and necessary solution.

As an outstanding one of 2D TMDs, MoS2 sheets have been widely investigated in lithium-ion batteries [14], catalysis [15] and sensors [16] due to its favorable intrinsic properties such as lower density, better chemical stability and unique electronics transportation [17], [18]. Particularly, the dielectric loss originated from interfacial and dipole polarization makes it largely advantageous for EMW absorbers [19]. For instance, Zhang et al. [20] fabricated a series of polyaniline@MoS2@Fe3O4 nanowire composites via situ polymerization and hydrothermal reactions, and the sample showed a strong absorption value of −49.7 dB with broad bandwidth of 6.48 GHz at 1.3 mm. Similarly, Wang and his coworkers [21] synthesized the MoS2/Fe3O4/graphene hierarchical structure consisting of MoS2-graphene modified with Fe3O4 particles by the mean of hydrothermal method and subsequent co-precipitation reaction, and the RLmin of −45.7 dB at the thickness of 2.5 mm was achieved. Recently, the MoS2-Fe3O4-C ternary composites were reported by Yang et al. [22] via a hydrothermal method followed by a chemical vapor deposition (CVD) method and the RLmin reached −53.03 dB at 7.86 mm. More recently, Aishwarya et al. [23] developed MWNTs/r-GO@MoS2@Fe3O4 composites for a ‘trigger-free’ self-healing EMI shield, which displayed high EMI shielding of 43.6 dB. Indeed, the EMW absorption property is largely enhanced by hybridizing Fe3O4 with MoS2 and other materials demonstrated by these reports. However, for most of researches, they pay more attention on pursing the stronger RLmin and excellent broad bandwidth (generally in X/Ku band) but neglecting the demand of low frequency band including C/X band. Hence, it is still a great challenge to meet the different demands with broad bandwidth including low frequency band by accurately tailoring the heterostructures. Additionally, relative to the MoS2/Fe3O4-based multi-component (ternary or more) hybrids, reports on EM wave absorbing performance of binary MoS2/Fe3O4 composites are scarce so far. Compared to the complicated synthesis routine for multi-component hybrids, it is more facile to fabricate binary composites due to its fewer components, which is of great technological importance. Therefore, it will be urgently necessary for exploring a facile fabrication of binary Fe3O4/MoS2 composites for the EMW absorption with broad bandwidth including low frequency band (C/X bands).

In this work, the binary Fe3O4/MoS2 composites were successfully fabricated by a facile hydrothermal method. The results indicated that the different morphologies of 3D MoS2 nanoflowers decorated with the monodispersed Fe3O4 particles were obtained by tailoring the molar ratio of Fe3O4 to MoS2. Besides, profiting from dielectric loss (MoS2), magnetic loss (Fe3O4) and good impedance matching (appropriate Fe3O4 content), the EMW absorption ability exhibited largely enhanced for binary Fe3O4/MoS2 composites compared to pristine Fe3O4 particles. The EAB of 6.1 GHz at thin thickness of 2.0 mm could be achieved while it showed the strongest RLmin intensity of −64.0 dB at ultra-thin thickness of 1.7 mm. Remarkably, the 100% frequency occupy ratio for the both low frequency of C (4–8 GHz) and X (8–12 GHz) bands could be realized while the RL intensity was still not severely deteriorated, which is superior than most of MoS2-based absorbers that have been reported so far. Hence, our work sheds light on the facile synthesis of brilliant EMW absorbers with selective broadband EM wave absorption performance.

Section snippets

Materials

The ethylene glycol (EG), and sodium acetate (NaAc), Sodium molybdate dihydrate (Na2MoO4·2H2O), Ferric (III) chloride hexahydrate (FeCl3·6H2O), thiourea (CH4N2S), polyethylene glycol (PEG Mw-20000 g/mol), were obtained from National Reagent Corp. (Tianjin, China).

Synthesis of the Fe3O4 microspheres

The Fe3O4 microspheres were synthesized by the hydrothermal method. Firstly, a modified solvothermal method was used to prepared the Fe3O4 microspheres similar to the previous literature [24]. Briefly, the 2.0 g PEG and 7.2 g NaAc were

Results and discussion

The synthesis of the hierarchical Fe3O4/MoS2 nanoflowers is illustrated schematically in Scheme 2. First, the numerous monodispersed Fe3O4 nanoparticles are prepared by the solvothermal process. And then the Fe3O4 nanoparticles are closely adorned on the MoS2 sheets by the means of the Van deer Waals interactions between these two phases in the hydrothermal process [25], which is similar to the MoS2/FeS2 reported by Che et al. [26]. With increasing the interaction time, the MoS2 sheets will be

Conclusion

In a word, we have effectively synthesized the hierarchical flower-like Fe3O4/MoS2 composites via a facile hydrothermal method. By tuning the Fe3O4 content, the different morphologies of Fe3O4/MoS2 composites were obtained, which showed better EWM absorption performance owing to the contribution of good impedance matching and dielectric/magnetic loss. For sample S3, it exhibited the best EMW absorption ability, where the RLmin was −64 dB at the thickness of 1.7 mm and the EAB of 6.1 GHz at the

CRediT authorship contribution statement

Jiaolong Liu: Writing - original draft, Visualization, Investigation. Hongsheng Liang: Validation, Methodology. Hongjing Wu: Writing - review & editing, Supervision, 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.

Acknowledgments

Financial support was provided by the National Science Foundation of China (Grants nos. 21806129 and 51872238), the Fundamental Research Funds for the Central Universities (Nos. 3102018zy045 and 3102019AX11) and the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2017JQ5116).

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