High-purity Nd metal was recovered from waste Nd–Fe–B magnet by the molten salt electrowinning process with chemical pretreatment. X-ray diffraction（XRD）, scanning electron microscopy（SEM）, energy dispersive spe...High-purity Nd metal was recovered from waste Nd–Fe–B magnet by the molten salt electrowinning process with chemical pretreatment. X-ray diffraction（XRD）, scanning electron microscopy（SEM）, energy dispersive spectroscopy（EDS）, cyclic voltammetry（CV）,chronopotentiometry（CP）, and inductively coupled plasma-atomic emission spectrometer（ICP/AES） were used to characterize the deposit and electrochemical behaviors. The results show that NdF_3 is effectively synthesized from the Nd–Fe–B magnet using HCl solution and NH4F. During the chemical treatment of the waste magnet,iron impurity is eliminated as a soluble [NH4]3[FeF6]complex. Electrowinning using NdF_3 in LiF molten salt shows that Nd metal is deposited from the electrolyte onthe cathode at the reduction potentials ranging from-1.48to-1.35 V（vs. W） with the concentration change of NdF_3.The final purity of Nd metal deposit is higher than99.78 %.展开更多
Transformation-temperature-hydrogen pressure phase diagram was constructed for a Nd15Fe79B6 alloy in order to estimate appropriate conditions for hydrogenation, disproportionation, desorption and recombination reacti...Transformation-temperature-hydrogen pressure phase diagram was constructed for a Nd15Fe79B6 alloy in order to estimate appropriate conditions for hydrogenation, disproportionation, desorption and recombination reaction （the HDDR）. Optimised recom- bination time （the highest coercivity） was found to be 10 rain. for 5 g samples processed at 740 ℃. Several HDDR processes were carried out at 30 kPa of hydrogen pressure at various temperatures. No correlation between magnetic propertiec and a direction of measurement was observed for the samples processed at 740 ℃. Remanence anisotropy was induced along an alignment direction when the temperature of the HDDR process was increased up to 800 ℃ and 850℃ for 〈100 gm and 100-160 p.m particles, respec- tively. Simultaneously, a small drop in coercivity was observed in the direction of alignment for 〈100 pm particles, but no for 100-160 grn particles. Furthermore, probably an ordered phase was found by TEM microstructure analysis in the bulk sample dis- proportionated at 850 ℃ under 150 kPa of hydrogen. Grains with antiphase domains were observed and corresponding electron dif- fraction patterns were resolved, likely indicating superlattice structures.展开更多
基金financially supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP) of the Korea Government Ministry of Knowledge Economy (No. 20122010300041)the National Research Foundation of Korea (No. 2011-0091839)
文摘High-purity Nd metal was recovered from waste Nd–Fe–B magnet by the molten salt electrowinning process with chemical pretreatment. X-ray diffraction（XRD）, scanning electron microscopy（SEM）, energy dispersive spectroscopy（EDS）, cyclic voltammetry（CV）,chronopotentiometry（CP）, and inductively coupled plasma-atomic emission spectrometer（ICP/AES） were used to characterize the deposit and electrochemical behaviors. The results show that NdF_3 is effectively synthesized from the Nd–Fe–B magnet using HCl solution and NH4F. During the chemical treatment of the waste magnet,iron impurity is eliminated as a soluble [NH4]3[FeF6]complex. Electrowinning using NdF_3 in LiF molten salt shows that Nd metal is deposited from the electrolyte onthe cathode at the reduction potentials ranging from-1.48to-1.35 V（vs. W） with the concentration change of NdF_3.The final purity of Nd metal deposit is higher than99.78 %.
基金Project supported by the National Centre for Research and Development(INNOTECH-K2/IN2/18/181960/NCBR/13)
文摘Transformation-temperature-hydrogen pressure phase diagram was constructed for a Nd15Fe79B6 alloy in order to estimate appropriate conditions for hydrogenation, disproportionation, desorption and recombination reaction （the HDDR）. Optimised recom- bination time （the highest coercivity） was found to be 10 rain. for 5 g samples processed at 740 ℃. Several HDDR processes were carried out at 30 kPa of hydrogen pressure at various temperatures. No correlation between magnetic propertiec and a direction of measurement was observed for the samples processed at 740 ℃. Remanence anisotropy was induced along an alignment direction when the temperature of the HDDR process was increased up to 800 ℃ and 850℃ for 〈100 gm and 100-160 p.m particles, respec- tively. Simultaneously, a small drop in coercivity was observed in the direction of alignment for 〈100 pm particles, but no for 100-160 grn particles. Furthermore, probably an ordered phase was found by TEM microstructure analysis in the bulk sample dis- proportionated at 850 ℃ under 150 kPa of hydrogen. Grains with antiphase domains were observed and corresponding electron dif- fraction patterns were resolved, likely indicating superlattice structures.
