Synthesis of Nanocrystalline Cobalt Ferrite by the Sonochemical Method in Highly Basic Aqueous Solution

摘要

This study reported the preparation of nanocrystalline CoFe_2O_4 in single step by the sonochemical method in highly basic aqueous solution without requiring of high temperature calcination process. To prepare nanocrystalline CoFe_2O_4, the mixed solution of the required molar ratio of cobalt nitrate hexahydrate (Co(N03).6H20) and ferric nitrate nonahydrate (Fe(N03).9H20) was precipitated in high concentration of sodium hydroxide medium solution (NaOH) under high intensity ultrasonic irradiation (20 kHz, 150 W/cm2). The effect of NaOH concentration (5, 10, 15 and 20 M) on phase formation, microstructure and magnetic property of CoFe_2O_4 was investigated. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) results showed that the as-prepared powders were single phase CoFe_2O_4 with cubic spinel structure. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) study showed that nanocrystalline CoFe_2O_4 had monosized distorted spherical morphology and an agglomeration of the nanocrystalline CoFe_2O_4 into nanoparticles was observed when increasing the NaOH concentration. The nanocrystalline CoFe_2O_4 exhibited superparamagnetic property and the saturation magnetization (M_s) obtained from vibrating sample magnetometry (VSM) was found to correlate with the crystallite size and varied from 39-45 emu/g.