Synthesis of Ni-SiO₂ composite microspheres in situ in ethylene glycol

In this study, the Ni-SiO₂ composite microspheres were synthesised in situ in ethylene glycol. The nickel colloidal suspension was synthesised by hydrazine reduction in ethylene glycol with the addition of polyvinylpyrrolidone, and then coated on by silica using the modified Stöber process. The as-synthesised samples were characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and vibrating sample magnetometer. XRD patterns showed that as-prepared nickel colloids are consistent with face-centred cubic phase and the broad peak at around 25° is attributed to amorphous SiO₂ in Ni-SiO₂ composite microspheres. TEM and SEM images indicated as-obtained Ni-SiO₂ composite microspheres appear near spherical with a size of about 100-200-nm, and get well dispersed. Magnetisation curves demonstrated the saturation magnetisation value of as-prepared Ni-SiO₂ composite microspheres is 4.4 emu/g with the content of nickel of about 20 wt.%.