In present work, the Fe3O4 magnetic nanoparticles were successfully synthesized by coprecipitation method. In order to study the effects of influential factors on the structural and magnetic properties of particles, the experimental runs were designed using response surface methodology(RSM) based on central composite design(CCD), while the reaction temperature, Fe2þ/Fe3þ cation ratio,and pH of reaction were defined as effective factors on the two responses include the amountsof crystallinity degree and saturation magnetization(Ms). The investigation of structural, magnetic, and microstructural properties of particles were carried out by X-ray diffraction(XRD), vibrating sample magnetometer (VSM), and dynamic light scattering(DLS) and transmission electron microscopy(TEM) analyses. As a result, the predictive quadratic models were fitted on the both responses while the R2 values were more than 0.97 for both models.The highest amounts of both responses(crystallinity degree:88.07% and Ms: 65.801emu/g)are presented when the reaction temperature, cationratio, and pH amounts are equal to 90 °C, 0.60,and10.5, respectively. Finally, the TEM results show the particles with size of about 10nm and narrow size distribution.

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