Preparation And Characterization Of Iron Oxide Nanoparticles

Iron oxide nanoparticles were prepared from ferric chloride aqueous solution and sodium hydroxide (or ammonia) by hydrothermal synthesis in autoclave. Chemical analysis, X-ray powder difrraction(XRD), infrared spectroscopy (FT-IR), transmission electron microscopy(TEM) were employed to analyze the purity, phase composition, particle size and morphology of Iron oxides.The spherical, elliptic, spindle and decussate particles were produced by controlling the conditions of hydrothermal synthesis. The diameters of uniform spherical particles were about 100nm. The axial ratio of elliptic particles was about 3 and the length was about 200nm, while the ratio and the length increased a little to about 5 and 500nm respectively for spindle particles. It was determined, by using chemical analysis and XRD, that the product is mainly consist of Fe2O3, whose purity is above 93%.The effects of the hydrothermal temperature, the initial pH value, the initial concentration of FeCl3, the kind and dosage of additive, microwave radiation, and of the reaction time were investigated. After 7 days ofhydrothermal synthesis in 100, the spherical particles were produced from 0.1mol-L FeCl3 solution and pH=4.0~4.5(no additive); the elliptic particles were obtained from 0.5mol-L FeCl3 solution and pH=4.0~-4.5 (NaH2PO4 as additive with additive to Fe3+molar ratio of 1/200); the spindle particles were formed from 0.5molL FeCl3 solution and pH=4.0~ 4.5 (NaH2PO4 as additive with additive to Fe3+molar ratio of 1/100), the decussate particles were produced from 0.5mol-L FeCl3 solution and pH=10.0~11.0 (NaH2PO4 as additive with additive to Fe3+molar ratio of 1/100).The intermediate P-FeOOH was prepared by forced hydrolyses from ferric chloride aqueous solution, it is inevitable that P-FeOOH be formed when the initial pH<5 with the existence of Cl. The mechanism and the affecting factors for the transformation of P-FeOOH to a-Fe2O3 were investigated. It is believed that Cl" can accelerate the phase transformation from p-FeOOH to a-Fe2O3.