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Sonochemical Synthesis of Cobalt Ferrite Nanoparticles

DOI: 10.1155/2013/934234

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Cobalt ferrite being a hard magnetic material with high coercivity and moderate magnetization has found wide-spread applications. In this paper, we have reported the sonochemical synthesis of cobalt ferrite nanoparticles using metal acetate precursors. The ferrite synthesis occurs in three steps (hydrolysis of acetates, oxidation of hydroxides, and in situ microcalcination of metal oxides) that are facilitated by physical and chemical effects of cavitation bubbles. The physical and magnetic properties of the ferrite nano-particles thus synthesized have been found to be comparable with those reported in the literature using other synthesis techniques. 1. Introduction The spinel ferrite nanoparticles have exceptional electronic and magnetic properties, which are quite different from the bulk materials [1]. As a result, the magnetic ferrite nanoparticles have found wide applications in information storage systems, ferrofluids, and medical applications like magnetic drug delivery and hyperthermia for cancer treatment [2]. Among metal ferrites, zinc, nickel, and cobalt ferrites have been mostly applied. Cobalt ferrite (CoFe2O4) is a hard magnetic material that is known to have high coercivity and moderate magnetization [3]. On nanoscale, the cobalt ferrite achieves properties of high saturation magnetization, high coercivity, strong anisotropy, high mechanical hardness, and high chemical stability [4]. Conventional techniques for synthesis of metal nanoparticles (including cobalt ferrite particles) are sol-gel method [5, 6], microemulsions [7, 8], reverse micelles [9], autocombustion, [10] and coprecipitation [11]. A relatively new technique for synthesis of ferrite nanoparticles is the sonochemical route [12–16], in which the reaction mixture is exposed to ultrasound irradiation. Spectacular physical and chemical effects induced by ultrasound bring about the synthesis of metal ferrites from the metal salt precursors, usually acetates. The hydrolysis of acetates, followed by oxidation of the hydroxides to oxides and the reaction between oxides to yield ferrites is brought about by ultrasound and its secondary effect, cavitation. Cavitation is essentially nucleation, growth and transient implosive collapse of gas bubbles driven by ultrasound wave [17]. This technique has been well demonstrated for zinc ferrites. In our previous papers [15, 16], we have tried to illuminate the links between physics of ultrasound and cavitation and the chemistry of zinc ferrite nanoparticles. It was revealed in these studies that chemical species produced during transient


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