Enhanced microwave absorption properties of Ni-doped ordered mesoporous carbon/polyaniline nanocomposites

https://doi.org/10.1016/j.mseb.2012.08.022Get rights and content

Abstract

We propose and demonstrate a new scheme to improve microwave absorption property through polyaniline (PANI)-functionalized Ni-doped ordered mesoporous carbon (OMC) by in situ polymerization method. The polymer-functionalized nanocomposites, embedding polyaniline within ordered mesoporous carbon, exhibit strong and broadband microwave absorption due to its better dielectric loss characteristic. OMC-Ni0.15/PANI exhibits an effective absorption bandwidth (i.e., reflection loss (RL)  −10 dB) of 4.7 GHz and an absorption peak of −51 dB at 9.0 GHz. The absorption peak intensity and position can be tuned by controlling the thickness of the coating.

Highlights

► OMC-Ni/PANI nanocomposites were prepared by in situ polymerization method. ► The effective absorption bandwidth was 4.7 GHz for OMC-Ni0.15/PANI. ► OMC-Ni/PANI showed excellent microwave absorption with respect to OMC-Ni. ► This effect could be mainly attributed to the improvement of impendence matching.

Introduction

Recently electromagnetic interference (EMI) has become a severe pollution problem due to the extensive utilization of electronic devices [1], [2], [3], [4], [5], [6]. To overcome the EMI shielding problem, the development of microwave absorbing materials with strong absorption over a broad frequency range is required urgently. For traditional microwave absorbing materials such as carbonyl iron or iron oxides (e.g. Fe2O3 and Fe3O4), the disadvantage of overweight limits their wide application [7], [8]. Although many efforts have been focused on, the challenges in preparation of light-weight, efficient and wide bandwidth microwave absorbers are still existed. Recently, ordered mesoporous carbon (OMC)-based materials have attracted increasing interests because of their large dielectric loss properties. OMC and OMC-based nanocomposites have been widely researched as a promising absorber with designed pore architecture, including OMC/silica composites [9], OMC/γ-Fe2O3 [10], ordered mesoporous C-TiO2 [11], etc. However, the OMC-based composites usually possess high conductivity and most of the incident microwave radiation is reflected rather than absorbed due to the skin effect [6].

Herein, we propose and demonstrate a new scheme to enhance microwave absorption property using the light-weight polyaniline (PANI) functionalized Ni-doped OMC nanocomposites. The incorporated polymers can embed in the small pores inside the carbon walls of OMC to construct bicontinuous interpenetrating framework, which may provide great advantage as dielectric loss materials. The magnetic Ni-based species coated onto OMC contribute the soft magnetic characteristics to the nanocomposites and improve the microwave absorption property [9], [10]. The polymer-functionalized Ni-doped OMC was obtained by an in situ polymerization of PANI. Compared with the general methods to synthesize OMC-Ni/PANI nanocomposites, the present strategy includes three advantages. First, the polyaniline is in situ synthesized during the polymerization, and therefore it is easy to form a thin uniform layer on the internal surface of the primary mesoporous. Dispersive PANI particles are also formed on the external surface of the mesoporous carbon. It is relatively convenient and low-cost to form the OMC-Ni/PANI nanocomposites compared with physically mixed and electropolymerization methods [12]. Second, the OMC-Ni/PANI nanocomposites are relatively stable since strong interactions between PANI layers or particles and OMC nanorods can be obtained during the in situ polymerization. Third, the size and morphology of the nanocomposites can be easily tuned.

Section snippets

Synthesis of OMC-Ni

The OMC-Ni was synthesized by soft-template method by using triblock copolymer Pluronic F127 as a structure-directing agent, soluble phenolic resin and nickel nitrate as carbon and nickel sources, respectively [13], [14]. Typically, 2.44 g phenol was melted at 50 °C, then 0.43 g NaOH (20 wt.%) aqueous solution was added slowly, followed by the addition of 2.34 g formaldehyde (37 wt.%) at 70 °C and held for 1 h with a reflux condenser to form the resol solution. Meanwhile, 4.58 g F127 and 0.38 g Ni (NO3)2

Results and discussion

Fig. 1 shows the TEM images of OMC, OMC-Ni0.05 and OMC-Ni0.15, respectively. The regularity of mesostructures (Fig. 1(a) and (b)) and the highly parallel pore channels (Fig. 1(d) and (e)) are clearly observed, indicating a large region of ordered mesopores in pure OMC and Ni-doped OMC with low Ni loading. However, when the Ni loading increases, the regularity of OMC-Ni can be destroyed (Fig. 1(c)). As is shown in Fig. 1(c), the Ni nanoparticles are well dispersed and embedded into the OMC walls

Conclusions

The OMC-Ni/PANI nanocomposites were fabricated by in situ polymerization in the pores and on the surface of OMC-Ni. The microwave absorption properties of OMC-Ni/PANI nanocomposites were studied over a frequency range of 2–18 GHz. The minimum RL is −51.2 dB and the effective absorption bandwidth of OMC-Ni0.15/PANI is 4.7 GHz, which are both larger than those of single OMC-Ni. The absorption peaks and effective absorption bandwidth can be tuned by controlling the Ni loading and the matching

Acknowledgment

This project was supported financially by the National Natural Science Foundation of China (nos. 50771082 and 60776822) and the Doctorate Foundation (CX201207), the Graduate Starting Seed Fund (Z2011011) of Northwestern Polytechnical University, the Natural Science Foundation of Shaanxi Province (2012JM1009) and the Scientific Research Program Funded by Shaanxi Provincial Education Department (12JK0984).

References (29)

  • S.M. Abbas et al.

    Journal of Magnetism and Magnetic Materials

    (2007)
  • T. Maeda et al.

    Journal of Magnetism and Magnetic Materials

    (2004)
  • L. Jing et al.

    Journal of Alloys and Compounds

    (2009)
  • Z.P. Wu et al.

    Scripta Materialia

    (2011)
  • G.X. Tong et al.

    Journal of Alloys and Compounds

    (2011)
  • G.X. Tong et al.

    Journal of Alloys and Compounds

    (2011)
  • J.H. Zhou et al.

    Journal of Alloys and Compounds

    (2011)
  • T. Wang et al.

    Journal of Solid State Chemistry

    (2010)
  • Y.Q. Dou et al.

    Journal of Power Sources

    (2011)
  • J.Y. Yao et al.

    Carbon.

    (2009)
  • X. Qi et al.

    Journal of Solid State Chemistry

    (2009)
  • M.S. Cao et al.

    Materials and Design

    (2003)
  • S.M. Abbas et al.

    Materials Science and Engineering B

    (2005)
  • H.J. Wu et al.

    Materials Chemistry and Physics

    (2012)
  • Cited by (0)

    View full text