Preparation of SiO₂ / Ni core-shell structured nanoparticles and their magnetic properties

Magnetic Ni nanoparticles coated with silica were successfully synthesized via the liquid deposition methodusing Na₂SiO₃ as the main raw material , and their st ructures and properties were studied by X-ray diff raction(XRD) , Fourier t ransform inf rared spect rometer ( FTIR) , t ransmission elect ron microscopy ( TEM) , thermogravimet ric analysis ( TGA) , differential scanning calorimet ry (DSC) and vibrating sample magnetometer (VSM) . XRD ,FTIR and TEM result s show that there is noncrystal silica on the surface of Ni nanoparticles and it prevents the nanoparticles f rom agglomerating. The oxidation resistance of SiO₂ / Ni nanoparticles is improved because of the protection of the silica coating. Magnetic properties show that Ni and SiO₂ / Ni are ferromagnetic materials. The hysteresisloop of Ni has an excursion because of the anti-ferromagnetic NiO. The silica coating reduces the saturation magnetization and improves the coercivity.