Synthesis and characterization of ultrafine and mesoporous structure of cobalt ferrite Hamid Emadi, Ali Nemati Kharat * School of Chemistry, University College of Science, University of Tehran, Tehran, Iran 1. Introduction There is an increasing interest in the synthesis of nanostrcu- tures due to their application in various fields of technology [1–7]. As an important part of nanomaterials, nanomagnetic materials have attracted considerable attention due to their utilizations in the magnetic field sensor, bio-sensors magnetic-storage media, power generation, magnetic resonance imaging, tracers to radioactive materials, and so on [8,9]. These new properties and applications which differ from bulk of these materials can be attributed to the finite number of atoms and large surface area [10]. High magneto resistance, quantum tunneling of the magnetization, and superparamagnetism are examples of the new features of the magnetic materials which are due to the small size of magnetic particles [11–14]. Among of the ferrites, cobalt ferrite is considered as a candidate for high density magnetic recording media because of its moderate saturation magnetization, high coercivity, mechanical hardness, and chemical stability [15]. Cubic spinel structure is the most popular form of ferrites which is consisting of trihedral [A] site and octahedral [B] site in the AB 2 O 4 crystal structure [16]. Cobalt ferrite (CoFe 2 O 4 ) has inverse spinel structure which Co 2+ ions are located in octahedral site while Fe 3+ ions are equally distributed between tetrahedral and octahedral sites and degree of inversion is determined by preparation conditions [17]. Distribution of these cations can affect nature of magnetic properties and lead to formation of spinel ferrites with various magnetic properties including ferrimagnet, antiferromagnet, and paramagnet. Also, these properties originate from the magnetic moments of the unpaired electrons which are coupled by super exchange interac- tion via the oxygen anions. Cobalt ferrite (CoFe 2 O 4 ) is a ferrimagnetic oxide and well known as hard magnetic material which can be applied in magnetic recording applications such as audio and video tape and high-density digital recording disks, etc. [18–20]. It is believed that the properties of ferrites are greatly affected by synthetic route because dependent on synthetic method, the cations distribution may be changed and magnetic property may vary. With this regard, different methods were applied for the synthesis of CoFe 2 O 4 such as sol–gel [21,22], hydrothermal synthesis [23], ball milling [24], chemical precipitation [25] and citrate-gel method [26]. Microwave irradiation in polyol medium was used for the synthesis of CoFe 2 O 4 nanostructures in current investigation. Application of microwave irradiation has different advantages including rapid heating rates, short processing durations, low power requirements, and product uniformity [27–29]. In comparison with other conventional heating process, microwave is regarded as situ mode of energy conversion which heat is generated internally within the material, instead of originating from external sources. In other words the microwave energy changes to heat by strong inter-molecular friction and Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx * Corresponding author. Tel.: +98 21 61112499; fax: +98 21 66495291. E-mail addresses: alnema@khayam.ut.ac.ir, nema22@hotmail.com (A.N. Kharat). A R T I C L E I N F O Article history: Received 29 January 2014 Received in revised form 29 April 2014 Accepted 30 April 2014 Available online xxx Keywords: Nanoparticles CoFe 2 O 4 Microwave Mesoporus structure Electron microscopy A B S T R A C T Ultrafine nanoparticles of cobalt ferrite (CoFe 2 O 4 ) were synthesized under microwave irradiation in polyol media and then were applied for the synthesis of mesoporous structures of cobalt ferrite. The effect of reaction parameters on products were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmittance electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FT-IR) spectra, vibrating sample magnetometer (VSM), and volumetric nitrogen adsorption. TEM and BET analysis showed presence of mesoporus structures with pore sizes less than 10 nm in the final product. ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. G Model JIEC-2027; No. of Pages 6 Please cite this article in press as: H. Emadi, A.N. Kharat, J. Ind. Eng. Chem. (2014), http://dx.doi.org/10.1016/j.jiec.2014.04.037 Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry jou r n al h o mep ag e: w ww .elsevier .co m /loc ate/jiec http://dx.doi.org/10.1016/j.jiec.2014.04.037 1226-086X/ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. Downloaded from http://www.elearnica.ir