The effects of rare earth doping on the formation process of α-FeOOH crystallite and the properties of γ-Fe2O3 magnetic powder were investigated. The growth of needle α FeOOH crystallite was completed by the basic ...The effects of rare earth doping on the formation process of α-FeOOH crystallite and the properties of γ-Fe2O3 magnetic powder were investigated. The growth of needle α FeOOH crystallite was completed by the basic process. The experimental results show that the rare earth doping can increase the aspect axial ratio of needle α-FeOOH grains. its anti-sintering capability during the heat-treatment and the thermostability of γ-Fe2O3 magnetic properties. The magnetic properties of γ-Fe2O3 doping with rare earth are as follows: the coercivity Hc=36.3 kA/m (445 Oe), the ratio saturation magnetization σs=90.4μWbm/kg (72 emu/g), the ratio remanent magnetization σr=54 μWbm/kg (43 emu/g), and the temperature coefficient of remanent magnetization of γ-Fe2O3 doping with 0.1 mol% Dy can reach -5 ×10-4℃-1.展开更多
γ-Fe2O3 nanoparticles were successfully synthesized by a chemically induced transformation of α-FeOOH.In this method,the precursor(α-FeOOH)was prepared by chemical precipitation,and then treated with a mixed FeCl2/...γ-Fe2O3 nanoparticles were successfully synthesized by a chemically induced transformation of α-FeOOH.In this method,the precursor(α-FeOOH)was prepared by chemical precipitation,and then treated with a mixed FeCl2/NaOH solution to produce the nanoparticles.X-ray diffraction indicated that when the precursor was treated with FeCl2(0.22 mol/L)and NaOH(0.19 mol/L),pure γ-Fe2O3 nanoparticles were obtained.However,when the concentration of FeCl2 was<0.22 mol/L or the concentration of NaOH was<0.19 mol/L,α-FeOOH and γ-Fe2O3 phases co-existed in the nanoparticles.Transmission electron microscopy observations showed that in the samples with co-existing phases,the nanoparticles did not have identical morphologies.The pure γ-Fe2O3 nanoparticles were polygonal rather than spherical.The volume ratio of α-FeOOH and γ-Fe2O3 was estimated for the two-phase samples from magnetization data obtained from a vibrating sample magnetometer.This chemically induced transformation is novel,and could provide an effective route for the synthesis of other metal oxide nanocrystallites.展开更多
文摘The effects of rare earth doping on the formation process of α-FeOOH crystallite and the properties of γ-Fe2O3 magnetic powder were investigated. The growth of needle α FeOOH crystallite was completed by the basic process. The experimental results show that the rare earth doping can increase the aspect axial ratio of needle α-FeOOH grains. its anti-sintering capability during the heat-treatment and the thermostability of γ-Fe2O3 magnetic properties. The magnetic properties of γ-Fe2O3 doping with rare earth are as follows: the coercivity Hc=36.3 kA/m (445 Oe), the ratio saturation magnetization σs=90.4μWbm/kg (72 emu/g), the ratio remanent magnetization σr=54 μWbm/kg (43 emu/g), and the temperature coefficient of remanent magnetization of γ-Fe2O3 doping with 0.1 mol% Dy can reach -5 ×10-4℃-1.
基金supported by the National Natural Science Foundation of China (11074205)
文摘γ-Fe2O3 nanoparticles were successfully synthesized by a chemically induced transformation of α-FeOOH.In this method,the precursor(α-FeOOH)was prepared by chemical precipitation,and then treated with a mixed FeCl2/NaOH solution to produce the nanoparticles.X-ray diffraction indicated that when the precursor was treated with FeCl2(0.22 mol/L)and NaOH(0.19 mol/L),pure γ-Fe2O3 nanoparticles were obtained.However,when the concentration of FeCl2 was<0.22 mol/L or the concentration of NaOH was<0.19 mol/L,α-FeOOH and γ-Fe2O3 phases co-existed in the nanoparticles.Transmission electron microscopy observations showed that in the samples with co-existing phases,the nanoparticles did not have identical morphologies.The pure γ-Fe2O3 nanoparticles were polygonal rather than spherical.The volume ratio of α-FeOOH and γ-Fe2O3 was estimated for the two-phase samples from magnetization data obtained from a vibrating sample magnetometer.This chemically induced transformation is novel,and could provide an effective route for the synthesis of other metal oxide nanocrystallites.
