Preparation of core-shell SiO₂/Fe₃O₄ nanocomposite particles by reverse microemulsion

Core-shell structural SiO₂/Fe₃O₄ nanocomposite particles were prepared via hydrolysis and condensation of tetraethyl orthosilicate (TEOS) by using Fe₃O₄ nanoparticles as seeds in a Triton X-100/hexanol/cyclohexane/water reverse microemulsion system. The effects of the mass concentration of Fe₃O₄, the mole ratio of water to Triton X-100 (ω₀) and the mass concentrations of NH₄OH and TEOS on SiO₂/Fe₃O₄, nanocomposite particles were investigated. The results show that mass concentration of Fe₃O₄ has an effect on the core number and appearance of the nanocomposite particles. The mass concentrations of NH₄OH and ω₀ are the main factors of the SiO₂ heterogeneously growing on the Fe₃O₄ nuclei surface. The SiO₂ shell becomes thicker and the particle morphology becomes more uniform with the increase of TEOS mass concentration. The saturation magnetization of the nanocomposite particles decrease with the increase in the thickness of the silica shell, the coercive force of the nanocomposite particles is almost unchanged, and remained favorable to superparamagnetism.