Preparation And Characterization Of Magnetic Nanoparticles Coated SiO₂

In this thesis, the magnetic nanoparticles coated with silica were prepared via a reverse micelle method, and their crystalline structure, particle size, morphology and magnetic properties were characterized by XRD, TEM, FT-IR and VSM. The detailed content was given as follows:1) Firstly, Fe3O4 nanoparticles were synthesized by a chemical coprecipitation method, and the triammonium citrate used as addition was added during this process. Then, Fe3O4 nanoparticles were coated with silica (Fe3O4@SiO2) via a reverse micelle method. The structure and magnetic properties of the Fe3O4@SiO2 nanoparticles were investigated by XRD, TEM, FT-IR, VSM respectively and the results showed:The silica were coated successfully on the surface of Fe3O4 nanoparticles; Since the coating of silica, the saturation magnetization showed a result of decrease; The coercivity of the Fe3O4 nanoparticles was near zero before and after coating performance, revealing the Fe3O4@SiO2 nanoparticles were of superparamagnetic properties.2) Fe(acac)3 and H2PtCl6·6H2O were used as Fe ions and Pt ions sources. NaBH4 was used as reductant. FePt nanoparticles were prepared by wet chemical reduction method. Thereafter, FePt nanoparticles used as seed particles were added the reverse microemulsion which was made up of OP-10/buty alcohol/cyclohexane/water. FePt@SiO2 nanoparticles were successfully prepared by a water-in-oil microemulsion method. The structure and magnetic properties of the FePt@SiO2 nanoparticles were investigated by XRD, TEM, FT-IR, VSM and the results showed:the silica were coated successfully on the surface of FePt nanoparticles but their saturation magnetization changed scarely before and after coating performance; The coercivity of the FePt@SiO2 nanoparticles was near zero, indicating they were of superparamagnetic properties.