Morphology of ferromagnetic sol–gel submicron silica powders doped with iron and nickel particles

Abstract

The sol–gel submicron spherical silica particles were obtained with the modified Stöber method using methanol. Iron and nickel dopants produced by the exploding wire method were introduced to the SiO 2 powders during the sol–gel process. The electron microscopy and laser diffraction particle size analyzer studies showed that the hybrid powders agglomerated easily in ethanol. The difference of ζ-potential in pure water between the pure silica (− 46.8 mV), the Fe-doped (− 39.7 mV) and the Ni-doped silica (− 41.5 mV) proved that doping changes the surface properties. The SEM studies confirmed that the Ni-particles could attach to the surface of the silica shells. With TEM it has been found that the differently sized Ni-particles may be encapsulated in silica shells, form clusters within silica or they may remain separate if they were larger than the silica particles. The saturation magnetization of the ferromagnetic hybrid powders was 0.81 emu/g (Fe-doped) and 0.51 emu/g (Ni-doped), while the hysteresis of magnetization revealed that the magnetic particles may have close to a single domain structure. The magnetization values and the X-ray studies confirmed that some Fe-oxides of the initial doping powder remained in the hybrid powder, while the Ni applied was nearly totally metallic.