The Synthesis Research Of Co-Zn Doped And Silica Coated Magnetic Iron Oxide Nanoparticles

The nanosized Fe3O4which contains both the characters of magnetic materialsand nanomaterials has become an active research field and widely used in thefollowing areas such as biological medicine, absorbing material, magnetofluid,magnetic recording materials and so on.In this article, Fe3O4nanoparticles and Co-Zn doped Fe3O4nanoparticles havebeen successfully synthesized by chemical coprecipitation method. Furthermore,silica coated magnetic nanoparticles have been prepared by sol-gel method. Themagnetic core could be α/γ-Fe2O3or Fe. The morphology, structure and magneticproperty of these products were characterized by X-ray diffraction (XRD), scanningelectron microscopy (SEM), transmission electron microscopy (TEM), Ramanspectroscopy, physical property measurement system (PPMS) and energy dispersivespectrometer (EDS). The influence of the various experiment parameters werediscussed in this paper.The results showed that:(1) The preparation and characterization of Fe3O4nanoparticles. We havesuccessfully prepared Fe3O4nanoparticles with a size of10nm at the followingexperiment parameters: reaction temperature at40℃, reaction time about15min,maturation temperature at75℃, maturation time about15min. The Ms (saturationmagnetization) of the products reached to65.4emu/g and showedsuperparamagnetism at room temperature. We also studied the products’ morphologyand magnetic property at different maturation time. The results showed that, the sizeof the prepared Fe3O4nanoparticles firstly increased and then decreased with thematuration temperature gradually increased, the easily volatile of the solvent whichwas mainly consisted of ethanol might be responsible to the phenomenon.(2) The preparation and characterization of Co-Zn doped Fe3O4nanoparticles.①The Co doped Fe3O4nanoparticles showed more serious aggregation than thepure Fe3O4nanoparticles which were synthesized at a same experiment condition.The size of the prepared Co doped Fe3O4nanoparticles increased with the rise of reaction temperature and maturation time. Their morphology and magnetic propertywere better at the experiment parameter as follows: reaction temperature at60℃,reaction time of15min, maturation temperature at75℃, maturation time of1h,which size was about62nm, and the Ms reached to73emu/g.②The Zn dopedFe3O4nanoparticles showed a good appearance compared with the pure Fe3O4nanoparticles which were synthesized at a same experiment condition. Theirmorphology and magnetic property were better at the experiment parameter asfollows: reaction temperature at40℃, reaction time of15min, maturationtemperature at75℃, maturation time of15min, which size was about35nm, andthe Ms reached to66emu/g.③The size of the Co-Zn doped products increasedobviously and ranged from75～300nm, furthermore, the Ms reached to69.6emu/gwhich increased slightly.(3) Silica coated magnetic nanoparticles by sol-gel method. Silica coatedmagnetic nanoparticles (Fe@SiO2and γ-Fe2O3@SiO2) were successfully prepared bysol-gel method. We firstly annealed the Xerogel at a lower temperature(350℃or500℃) in air, then a heat treatment at a higher temperature (800℃) in Ar2atmosphere, the carbon from xerogel’s incomplete combustion played a role ofreductant. The results showed that, the prepared Fe@SiO2nanoparticles werenear-spherical with the size of100nm~150nm, which showed superparamagnetic atroom temperature with the saturation magnetization of10.8emu/g. The thickness ofcoated silica was20nm. And, the prepared γ-Fe2O3@SiO2nanoparticles werenear-spherical with the size of120nm and showed superparamagnetic at roomtemperature with the saturation magnetization of21.1emu/g. The reaction processand mechanism were analyzed in this work.