Shape-controlled synthesis of FeNi 3 nanoparticles by ambient chemical reduction and their magnetic properties
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Li Fan and Qin Zhenping College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, China
Cui Suping and Nie Zuorenb) College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China (Received 22 November 2011; accepted 8 February 2012)
A facile method to control the morphology of FeNi3 nanoparticles by solution reduction reaction is presented. The spherical to platelet FeNi3 particles were obtained by changing pH from 11.5 to12.5 with 0.16 mol/L of hydrazine under ultrasound irradiation, with the ratio of Fe2+ to Ni2+ as 1:3. The amount of hydrazine had little influence on the morphology of the particles. The saturation magnetization (Ms) and coercive force (Hc) of the platelet particles were 59 emu/g and 120 Oe, respectively. The real part l9 of the permeability of the platelet particles was about 2.43–2.71 and was frequency-independent in the range of 0.1–1.0 GHz. The imaginary part (l99) of the particles showed increase from 0.04 to 2.14 within the same frequency range.
I. INTRODUCTION
Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2012.67
high saturation magnetization and low coercivity.15 The nanometric Fe–Ni alloys have been produced by various methods, such as mechanical alloying,16,17 decomposition of carbonyl compounds,18 electrodeposition,19,20 inert-gas condensation method,21 sol–gel synthesis,13 and chemical reduction process.22–29 Among these routes, chemical reduction in aqueous solution can be easily performed and has advantages for lower cost, lower temperature, and less time. The reducing agents, such as polyol,23 NaBH4,24 hypophosphite,25 and hydrazine hydrate (N2H4H2O),22,26,27 are commonly used. However, polyol process should be performed at temperature higher than about 100 °C, and NaBH4 reduction may produce Fe2B during reaction.24 Hydrazine hydrate is a moderate reducing agent with low cost and has been proven to be good alternative for producing metallic particles. Spherical FexNi1x alloys (x 5 0.15, 0.20, 0.22, 0.25, 0.30, 0.50, and 0.65) have formed with the reduction of N2H4H2O under alkaline condition.22,26 The spherical FeNi3 alloy nanoparticles have been synthesized using hydrazine hydrate as reducing agent at room temperature.24 Sheetlike FeNi3 nanoparticles have been produced using hydrazine hydrate as a reductant at 55 °C moderate temperature under ultrasonic irradiation.27 And FeNi3 alloy nanoplatelets were prepared using hydrazine hydrate as a reductant and sodium dodecyl sulfate as a surfactant by hydrothermal reduction at 180 °C.28 Although the mechanism of the shape control has been suggested, the transformation from nanosphere to nanoplatelets was not detailed. In the present work, the FeNi3 platelet nanoparticles were obtained by hydrazine reducing route at room temperature under ultrasonic irradiation. The formation of FeNi3 nanoparticles and the possible
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Ó Materials Research Society 2012
In recent years, much at
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