Preparation of Composite Nanoparticles of Fe-Zn Bioxide Using Surface Modification and Their Subsequent Characterization

During the liquid-phase synthesis of γ-Fe₂O₃ nanoparticles using a chemically induced transition in FeCl₂ solution (400 mL, 0.25 M), the surface modification of the particles was undertaken by adding ZnCl₂ solution, in an attempt to prepare composite nanoparticles. The magnetization, morphology, chemical composition, and crystal structure of the product were characterized using a vibrating sample magnetometer, transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The experimental results showed that when the concentration of ZnCl₂ solution did not exceed 2 M (50 mL), the γ-Fe₂O₃-ZnFe₂O₄ bioxide composite nanoparticles coated by FeCl₃ · 6H₂O could be prepared. These particles were nearly spherical and their average size was about 11 nm; specific saturation magnetization was about 48 Am²/kg. The molar, mass, and volume percentages of every composition phase, as well as the average density of the composite nanoparticles, were estimated from the characterization results. A particle model with a core that is γ-Fe₂O₃ covered with ZnFe₂O₄ is proposed.