Solution synthesis and novel magnetic properties of ball-chain iron nanofibers
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Wenhua Wu College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China
Jianguo Guanb) State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China
Jianping Wang, Ji Ma, Jinhao Yuan, and Sunli Wang College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China (Received 3 May 2011; accepted 24 August 2011)
The current work describes the simple solution process of ball-chain polycrystalline Fe nanofibers with aspect ratios (k) and diameters (D) of over 165 and 3095 nm. Static magnetic and microwave electromagnetic property studies demonstrated that such properties strongly depend on the k and D of the Fe nanofibers. As the k and D increase, the U-shape of the saturation magnetization (Ms) reaches a maximum of 180.0 emug1, owing to the cooperative action of nanoeffects and magnetic interactions, whereas the coercivity (Hc) gradually increases due to aspect ratio variations. In contrast, the change in trends of the permittivity (e9, e0) and the dielectric loss (tgdE) are represented as an inverted U-shape; the permeability (l9, l0) and magnetic loss (tgdM) increase at low-frequency ranges and decrease at high frequency ranges. Stronger absorption and broader bandwidths of Fe nanofibers compared with Fe nanoparticles are ascribed to higher dielectric losses. The prepared Fe nanofibers have high potential in light-weight and broad bandwidth microwave absorbing applications.
I. INTRODUCTION
Magnetic metal fibers have recently attracted wide attention because of their important application as materials for electromagnetic shielding, absorption, magnetic recording, and medical and biological engineering.1 Polycrystalline Fe fibers are recognized as potential microwave-absorbing materials, owing to their low density, shape and magnetocrystalline anisotropy, and various losses. Such characteristics enable Fe fibers to achieve broad bandwidths and strong absorption, and avoid the high-density defects of metal powders and ferrites.2,3 Electromagnetic parameters are key factors that determine the absorption properties of Fe fibers. To this end, some methods have been utilized to modulate Fe fibers, including changing their volume fractions,4 controlling their diameters and aspect ratios,5 modifying their surface characteristics,6 alloying,7 and mixing techniques.8,9 Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2011.307 2590
J. Mater. Res., Vol. 26, No. 20, Oct 28, 2011
http://journals.cambridge.org
Downloaded: 27 Jan 2016
However, there remain practical difficulties in the large-scale enhancement of the electromagnetic parameters of microwave-absorbing materials, one of which is permeability. The diameters and aspect ratios of Fe fibers were theoretically confirmed to be crucial for modulating the electromagnetic parameters of Fe fibers,10,11 but the experimental analysis of such characteristics has focused chiefly on Fe microfibers,
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