Obtenção de Nanopartículas Superparamagnéticas de NiFe2O4 por Síntese Hidrotérmica Assistida por Micro-Ondas

Abstract

NiFe2O4 nanoparticles were synthesized by co-precipitation method, assisted by microwave heating. The colloidal precipitate was subjected to heating at various temperatures in order to determine the optimal temperature for the synthesis and resulted in materials with good morphology and small size of crystal. Next, we studied the effect of heating time on the structural and magnetic properties of nickel ferrite. The colloidal precipitate was subjected to microwave heating, keeping the temperature constant at 160 ° C at three different times 7 , 12 and 17 minutes. The XRD patterns of the samples confirmed the formation of nanoparticles, which showed cubic structure of the inverse spinel type and good crystallinity. The crystallite size was calculated using the Scherrer equation. The variation of the magnetization as a function of applied magnetic field at room temperature was studied using a vibrating sample magnetometer (VSM), obtaining values of remanent magnetization and coercivity equal to zero , suggesting superparamagnetic behavior. Increasing the heating time (7, 12 and 17 minutes) produced an increase in the size of the crystallite (9 – 27 nm) and an increase in the saturation magnetization (31 – 45 emu/g) to the sample. Blocking temperature was found by tracing graphic of remanent magnetization versus temperature. A sample of magnetite, courtesy of Advanced Materials Group – GQMAT, suffered modification of its surface by the polymer APTES (3-aminopropil)trietoxisilano, using microwave heating. Data obtained from the (VSM), thermogravimetry (TG) and Infrared (FT-IR) confirmed the adsorption from the experiments, it was possible to construct a heating ramp efficient for the production of nanomaterials to lower synthesis temperature and shorter heating time.