Preparation and Characterization of Magnetic Ferrofluid MnZn Ferrite Nanoparticles

Abstract

Nanoparticles of Mn1-xZnxFe2O4 have been prepared by co-precipitation method and followed by heat treatment in hydrothermal autoclave reactor; where x varied from 0 to 0.5, with amount of change 0.1 in every experiment. XRD results showed that it was difficult to prepare MnZn-ferrite directly by using the coprecipitation method. Field emission scanning electron microscopes (FESEM) images confirmed that the preparation method produced spherical nanoparticles with a slight change in the particle size distribution. The particle size has shrunk after the heat treatment. The average particle size had estimated to be about 20 nm. Fourier Transform Infrared Spectroscopy (FTIR) spectra of samples showed two distinct absorption bands, the band at ~ 617(cm-1) and the ~426 (cm-1) attributed to the tetrahedral and octahedral site respectively. The absorption bands of the tetrahedral site slightly shifted towards high frequency with increasing zinc content. According to a magnetic measurement, the study indicated that the size of particles was sufficiently small to behave superparamagnetically, the hysteresis loop curves perfectly matched, that evidence the formation of typical soft magnetic materials. The heating efficiency of water-based ferrofluid studied under magnetic field strength 6.5kA/m and the frequency 190 kHz. The results showed that the heating rate of ferrofluid samples (x=0.3, 0.4 and 0.5) was not changed. Also, constancy of temperature at 44􀔨 when x=0.1 made it favoring for hyperthermia treatment as self-regulate magnetic nanoparticles. Depending on the increase in the heating curve, the susceptibility, effective relaxation time and Néel relaxation time were determined. The second series of nanocrystalline 􀀉􀂇􀬵􀬿􀭶 􀬶􀬾 􀀝􀂐􀭶 􀬶􀬾􀀉􀂇􀬶 􀬷􀬾􀀒􀬸 􀬶􀬿 (where x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) powder has been synthesized by co-precipitation method followed by heat treatment in an autoclave reactor. Identifying and structural characterization of samples had been carried out by using X-ray diffraction. The results demonstrated that all the samples have spinel structure and the zinc ions are engaged within spinel structure. As well as, it is revealed that the pure single phase has been obtained. FE-SEM images had revealed that all samples have homogeneous spherical shape with narrow distribution of the particles size (􀌱20nm). FTIR spectra of 􀀉􀂇􀬵􀬿􀭶 􀬶􀬾 􀀝􀂐􀭶 􀬶􀬾􀀉􀂇􀬶 􀬷􀬾􀀒􀬸 􀬶􀬿 samples showed two distinctive absorption bands lie in the region ~561 and ~376 cm-1, which indicates formation of spinel structure for ferrite. Magnetic measurements were performed at room temperature by VSM on both types of samples; condensed nanoparticle (bulk) and nanoparticles that dispersed in paraffin wax. Both types of samples showed negligible coercivity and remanent magnetization. As it revealed the presence of unblocked superparamagnetic nanoparticles in the samples at defined temperature. A significant variation of saturation magnetization was noticed by changing the zinc content in the structure, and highest value has gained at x=0.5. Then saturation magnetization gradually decreased with the increase in zinc content. Heating efficiency of water based ferrofluid samples carried out through hyperthermia experiments. It tested under an alternating magnetic field 6.5 kA/m and frequency 270 KHz, the results showed that the intrinsic loss power (ILP) had doubled at x=0.3 as compared with magnetite.