Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Mechanochemically synthesized Fe 2 B nanoparticles embedded in SiO 2 nanospheres Sıddıka Mertdinç ⁎ , Duygu Ağaoğulları, M. Lütfi Öveçoğlu Istanbul Technical University, Chemical and Metallurgical Engineering Faculty, Metallurgical and Materials Engineering Department, Particulate Materials Laboratories (PML), 34469 Maslak, Istanbul, Turkey ARTICLE INFO Keywords: A. Powders: solid state reaction B. Microstructure-final B. X-ray methods D. Borides D. SiO 2 ABSTRACT This study reports on the preparation of diiron boride (Fe 2 B) powders via mechanochemical synthesis (MCS) followed by a purification step and on the embedment of pure Fe 2 B nanoparticles into silica (SiO 2 ) nanospheres. Fe 2 O 3 ,B 2 O 3 and Mg powders used as starting materials were blended in stoichiometric amounts and mechan- ochemically synthesized up to 7 h in a high-energy ball mill. As-synthesized powders were purified from the undesired Mg-based by-products by HCl leaching. After that, pure Fe 2 B nanoparticles with sizes of smaller than 40 nm were embedded in SiO 2 nanospheres using a tetraethyl orthosilicate (TEOS) and ammonia (NH 3 ) con- taining solution. Characterization investigations of the as-synthesized, leached and SiO 2 -embedded powders were carried out using X-ray diffractometer (XRD), scanning electron microscope/energy dispersive spectro- meter (SEM/EDS), particle size analyzer (PSA), transmission electron microscope (TEM), Fourier transform in- frared spectrometer (FTIR) and vibrating sample magnetometer (VSM). The average particle size of the Fe 2 B incorporated SiO 2 nanospheres was measured as about 330 nm. Magnetic measurements revealed that pure Fe 2 B powders and their SiO 2 -embedded samples had soft ferromagnetic behaviour with coercivity of 125 and 168 Oe, respectively. 1. Introduction Synthesis of magnetic nanoparticles (MNPs) and improvement of their properties have attracted considerable interest in recent years because of their supermagnetism, high magnetic coercivity and sus- ceptibility and low Curie temperature [1]. MNPs are potential candi- dates in various biomedical applications such as cancer detection and therapy, magnetic resonance imaging (MRI), magnetic drug targeting and delivery, cell and tissue repairment, catalysis, hyperthermia and xerography applications [2–7]. Not only iron, cobalt, nickel and their alloys but also iron oxides, iron-cobalt oxides were used as MNPs in biomedical applications [3,7–9]. In particular, Fe 3 O 4 or Fe 2 O 3 are the most commonly used nanoparticles substituting for cobalt or nickel which are considered as toxic and have low chemical stabilities, al- though they are highly magnetic materials [1,10,11]. Besides, iron borides can attract attention among the nanocrystalline ferromagnetic materials due to their soft magnetic properties [12,13]. Iron borides are generally produced via chemical reduction pro- cesses using FeCl 3 /NaBH 4 , Fe(CO) 5 /(C 2 H 5 ) 3 NBH 3 or FeBr 3 /LiBH 4 as starting materials [12]. In addition, electric arc method, thermal plasma method, melt-spinning, sol-gel method, auto ignition, co- precipitation processes, self-propagating high-temperature synthesis (SHS), chemical vapour deposition method (CVD) are the other pro- duction routes for iron borides [12–15]. Solid-state processes are also utilized for the synthesis of iron borides [13,16,17]. Mechanochemical synthesis (MCS) is one of the solid-state production method used for obtaining high-purity borides [17–22], composites or advanced mate- rials with submicron- or nano-sized particles [23]. MCS process, trig- gered by repeated welding and fracturing of the initial powders during milling, provides an ignition in the presence of a reducing agent and enables a chemical reaction in the absence of externally applied heat [18,19,23]. The mill type, milling speed, milling time, ball-to-powder weight ratio, milling media, milling atmosphere, initial particle size are the process parameters of the MCS process [23]. There are few studies related to the solid-state synthesis of iron boride powders in the ar- chival literature. Şimşek et al. [17] synthesized Fe 2 B powders starting from Fe, B 2 O 3 and Mg containing blends via MCS in a high-energy ball mill. Mohammadi et al. [13] produced Fe 2 B powders from Fe 2 O 3 ,B 2 O 3 and CaH 2 including mixtures by using a solid-state reduction route. Also, Fu et al. [24] used Fe 2 O 3 , Al and B initial materials to obtain Fe 3 B powders by aluminothermic reduction. There is still an open area in the MCS of iron borides starting from economical oxide raw materials with https://doi.org/10.1016/j.ceramint.2018.05.116 Received 11 April 2018; Received in revised form 10 May 2018; Accepted 14 May 2018 ⁎ Corresponding author. E-mail addresses: mertdinc@itu.edu.tr (S. Mertdinç), bozkurtdu@itu.edu.tr (D. Ağaoğulları), ovecoglu@itu.edu.tr (M.L. Öveçoğlu). Ceramics International xxx (xxxx) xxx–xxx 0272-8842/ © 2018 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Please cite this article as: Mertdinç, S., Ceramics International (2018), https://doi.org/10.1016/j.ceramint.2018.05.116