Characterization of Co-modified γ-Fe_2O_3 Based Composite Nanoparticles

摘要

During the synthesis of γ-Fe_2O_3 nanoparticles using a chemically-induced transition in a Fel_2 solution, Co-surface modification was attempted by adding Co(NO_3)_2 and NaOH to the solution. The magnetization behaviors, morphologies, crystal structure, and chemical compositions of the as-prepared samples were characterized using vibrating sample magnetometry, transmission electron microscopy, X-ray diffractometry, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The as-prepared particles consisted of γ-Fe_2O_3/CoFe_2O_4 composite crystallite and a CoCl_2-6H_2O coating. The molar, mass and volume ratios of the phases were estimated from the characterization results for each sample. The Co-modified γ-Fe_2O_3 nanoparticles' anisotropic constant is approximately 1.48×10~(-1) J/cm~3. Their coercivity depends on the size of composite crystallites, which is based on the γ-Fe_2O_3/CoFe_2O_4 content rather than the Co content.