Elsevier

Materials Letters

Volume 122, 1 May 2014, Pages 103-105
Materials Letters

Magnetic and electromagnetic properties of Fe3O4/C self-assemblies

https://doi.org/10.1016/j.matlet.2014.01.016Get rights and content

Highlights

  • Fe3O4/C self-assemblies have been synthesized by the simple hydrothermal method.

  • Amorphous carbon layer may restrain the growth of Fe3O4 nanoparticles.

  • The MS of Fe3O4/C self-assemblies is lower than that of Fe3O4 nanoparticles.

Abstract

Fe3O4/C self-assembled rod-like nanostructures with average diameter of 10 nm and length of 200 nm have been synthesized by the hydrothermal method. Fe3O4/C rod-like nanostructures were self-assembled by Fe3O4/C nanoparticles. The saturation magnetization of Fe3O4/C self-assemblies is 41.7 emu/g. Compared to Fe3O4 nanoparticles, the higher dielectric loss of Fe3O4/C self-assemblies is ascribed to the amorphous carbon layer. Due to the existence of carbon layer on Fe3O4, the real part of permeability of Fe3O4/C self-assemblies is higher than that of Fe3O4 nanoparticles at 2–16 GHz. Two overlapped peaks of imaginary part of permeability in Fe3O4/C self-assemblies are from the natural and exchange resonance.

Introduction

During the last few years, with the rapid growth in utilization of electrical and electronic devices, the damage of ecological environment caused by electromagnetic (EM) radiation pollution and threat to the health of human have become more serious [1]. Much attention has been focused on EM-absorbing materials. Fe3O4 have been extensively investigated as EM-wave absorbers with low cost and strong absorption characteristics [2]. However, the Fe3O4 have main disadvantages such as high density and narrow absorption bandwidth. In order to improve the EM properties of Fe3O4, various Fe3O4-based nanocomposites including the conductive and nonmagnetic material have been widely investigated. Fe3O4/cabon [3], Fe3O4/TiO2 [4], Fe3O4/SiO2 [5], and Fe3O4/SnO2 [6] have been reported and their EM properties have been studied.

For magnetic materials, the key to enhancing microwave absorbing properties lies in the improvement of complex permeability. High permeability and high resonance frequency are both required. As is well known, the static permeability (μs) and the resonance frequency (fr) of the magnetic materials satisfy the equations: 2πfr=γHa and Ha=4|K1|/3μsMs, where γ=2.8 GHz kOe−1 is the gyromagnetic ratio and Ha is the crystalline anisotropic field and coefficient, respectively [2], [7], [8]. Ha includes the volume anisotropic field, surface anisotropic field and shape anisotropic field contributions [2], [7], [8]. Therefore, the large shape anisotropy can effectively improve the initial permeability and resonance frequency. Fe3O4/C nanocomposites have been synthesis by different methods [9]. In this paper, we report a new approach to synthesize Fe3O4/C self-assembled rod-like nanostructures by the simple hydrothermal method and investigate their magnetic and EM properties in detail.

Section snippets

Experimental

Analytically pure reagents were used in this experiment. The Fe3O4 nanoparticles and Fe3O4/C self-assemblies were prepared without and with glucose at the same experimental conditions, respectively. The detailed processes were as follows: a mixture was prepared by the hydrated ferrous sulfate (FeSO4·7H2O, 2.78 g), glucose (C6H12O6, 2 g) and deionized water (50 ml). Then, ethyl alcohol (C2H5OH, 99%, 50 ml) and hydrazine hydrate (N2H4, 50%, 4 ml) were dissolved in the above mixture with continous

Results and discussion

Fig.1 shows the XRD patterns of as-prepared samples, in which all the diffraction peaks can be indexed to the cubic phase of Fe3O4 (JCPDS 19-0629). The peaks from sample without glucose (Fig. 1(a)) are stronger and narrower than those from sample with glucose (Fig. 1(b)). According to the Scherrer formula, the average size of the sample without glucose is estimated to be 22 nm, while the average size of the sample with glucose is 10 nm. The morphology of samples with/without glucose is given in

Conclusions

Fe3O4/C self-assemblies were synthesized by a simple hydrothermal method. The average diameter and length of Fe3O4/C self-assemblies is 10 and 200 nm, respectively. The MS of Fe3O4/C self-assemblies is lower than that of Fe3O4 nanoparticles. The dielectric loss of Fe3O4/C self-assemblies is higher than that of Fe3O4 nanoparticles. Due to the existence of carbon layer on Fe3O4, μ' of Fe3O4/C self-assemblies is higher than that of Fe3O4 nanoparticles at 2–16 GHz. Two overlapped peaks of μ of Fe3O4

Acknowledgments

This study has been supported by the National Natural Science Foundation of China (Grant nos. 21071003 and 51201002).

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