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Fe5O7(OH)4H2O ferrihydrite is a low-crystallinity antiferromagnetic material.c-Fe2O3(maghemite)magnetic nanoparticles were prepared from a ferrihydrite precursor,by chemically induced transformation in FeCl2/NaOH solution.The magnetization,morphology,crystal structure and chemical composition of the products were determined by vibrating sample magnetometry,transmission electron microscopy,X-ray diffraction(XRD),energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy(XPS).Ferrihydrite underwent aggregation growth and transformed into a-FeO(OH)(goethite)particles,which subsequently transformed into c-Fe2O3nanoparticles,that became coated with NaCl.The c-Fe2O3particles had a flake-like morphology,when prepared from 0.01 mol/L FeCl2and a FeCl2:NaOH molar ratio of 0.4.The c-Fe2O3particles were more spherical,when prepared from a FeCl2:NaOH molar ratio of 0.6.The Fe content of the flake-like particles was lower than that of the spherical particles.Their magnetizations were similar,and the coercivity of the flake-like particles was larger.The differences in morphology and magnetization were attributed to the surface effect,and the difference in coercivity to the shape effect.
Fe5O7 (OH) 4H2O ferrihydrite is a low-crystallinity antiferromagnetic material.c-Fe2O3 (maghemite) magnetic nanoparticles were prepared from a ferrihydrite precursor, by chemically induced transformation in FeCl2 / NaOH solution.The magnetization, morphology, crystal structure and chemical composition of the products were determined by vibrating sample magnetometry, transmission electron microscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy (goethite) particles, which succeeded transformed into c-Fe2O3nanoparticles, that became coated with NaCl. The c-Fe2O3particles had a flake-like morphology, when prepared from 0.01 mol / L FeCl2 and a FeCl2: NaOH molar ratio of 0.4.The c -Fe2O3 particles were more spherical, when prepared from a FeCl2: NaOH molar ratio of 0.6. The Fe content of the flake-like particles was lower than that of the spherical particles. Their magnetizations were similar, and the coercivity of the flake-like particles was larger. differences in morphology and magnetization were attributed to the surface effect, and the difference in coercivity to the shape effect.