The thermal decomposition method is among the easiest techniques for the formation of nanoferrites. This process involves thermal decomposition of organo-metallic precursors such as metallic acetylacetonates and carbonyls in the presence of organic solvents and surfactants (oleic acid and hexadecyl amine) for the synthesis of nanoferrites (Byun et al. 2009). Based on the type of precursor of metals, the low or high temperature can be used like a temperature of about 500°C is employed for the calcinations of maghemite (c-Fe203) in the air in order to form a-Fe203 (Darezereshki et al. 2012). On the other hand, during synthesis of Fe,04, a low temperature of 165°C is used to decompose Fe,(CO)12 complex in diethylene glycol diethyl ether, with the oleic acid used as a stabilizer. The heating rate, temperature, or concentrations of precursors are the adjustable variable to get a controlled size and shape of ferrite nanoparticles, with nanoparticles with a highly monodisperse, uniform texture, and narrow distribution particle size (Dong et al. 2015). The oleic acid and iron oleate precursor’s ratios are changing, and the thermal decomposition time changed from 2 and 10 h used in order to get spherical and cubic c-Fe20„ respectively (Salazar-Alvarez et al. 2008). The production at a high scale with controlled size and shape can be carried out by employing this technique (Park et al. 2004; Wu et al. 2015; Fantechi et al. 2015). The procedure can be employed for the growth of ferrite nanoparticles required for medical as well as industrial applications.
In the solvothermal procedure, both non-aqueous and aqueous solvents can be used to produce nanoparticles with specific switch over the shape, size distribution, and crystalline phases (Wu et al. 2015). These physical characteristics can be modified by altering certain experimental variables such as the reaction temperature, solvent, reaction time, surfactant, and precursors. A number of ferrite nanoparticles and their corresponding composites have been prepared using the solvothermal synthesis method. Usually, the solvothermal technique is conveniently applied for the development of ferrite nanoparticles required with developed physical and chemical characteristics and it is applicable to both industrial and biomedical areas, as required.
Formation of nanoferrites by the sonochemical procedure has been reported as a suitable method, especially to form Fe304 and c-Fe,0, nanoferrites (Shaft et al. 2001, 2002). During ultrasonic irradiation, bubbles are produced in the solvent medium and can effectively accumulate the diffuse energy of ultrasound; upon extreme collapse, high energy is released to heat the content of the bubble. It produces a transient localized hot spot with an actual temperature and pressure esoteric of the bubbles of approximately 5000 К and 1000 bars respectively with heating and cooling rates >1010 К S-'. These extraordinary circumstances allow the use of a range of chemical reactions that are normally not accessible (Bang and Suslick. 2010). The composition of the systems expected to be synthesized using the sonochemical method is identical to the composition of the vapor in the bubbles; this assists in controlling the purity of nanoparticles (Tartaj et al. 2003). It is exclusively vital in crystal growth reduction, enables control over the particle size distribution, and uniformity of mixing but less significant for the formation of nanoferrites with controllable shapes and disparity (Wu et al. 2015). During the development of industrially vital non-ferrite NPs such as a-Fe,03, the dependency of particle size on the intensity of ultrasound wave and reaction temperature has also been observed (Hassanjani-Roshan et al. 2011). In this study, deviation in a-Fe,0, nanoparticle size was noticed, with a change in temperature and ultrasonic intensity. This indicates that with the sonochemical technique, utilized temperature, and ultrasonic intensity are the major determining factors that influence the particle size of nanoparticles. Commonly, it is attractive for the formation of magnetic nanoparticles due to the comfort of controlling reaction conditions and the opportunity for obtaining magnetic nanoparticles with high crystalline, coupled with low working temperature conditions.
The microwave-assisted synthesis procedure is a current technique which is used for the formation of versatile nonmaterial. In a microwave method, energy is conveyed directly to materials by using molecular interaction with the EMR. Heat is generated as the result of electromagnetic energy conversion to thermal energy from 100 to 200°C with a shorter reaction time (Mondal et al. 2015).
The exhaust drain connected to the Teflon vessel is used to drain any vapor produced during operation (Bhatt et al. 2011; Wu et al. 2015; Gonzalez-Moragas et al. 2015). The reasonable cost production of nanoferrites is possible with narrow size distribution in an instant, and is able to produce a high quality yield (Ding et al. 2008; Hu and Yu. 2008; Wu et al. 2015). The improved multi-mode equipment of the microwave-assisted method for the synthesis of nanoferrites has recently been reported (Gonzalez- Moragas et al. 2015). The large-scale production of nanoferrites can be carried out in equipment in multi-mode with exposure of several vessels in parallel mode. It is important to overcome hindrances faced in microwave-assisted synthesis with a single vessel. It offers the formation of nanoferrites on a higher scale with low yield, as compared to other methods.