A leaching and selective precipitation approach is proposed in this work to recover rare earth elements(REEs) from NdFeB magnet wastes collected from industry. Hydrochloric acid and oxalic acid were employed as the le...A leaching and selective precipitation approach is proposed in this work to recover rare earth elements(REEs) from NdFeB magnet wastes collected from industry. Hydrochloric acid and oxalic acid were employed as the leaching and precipitation agents, respectively. Hexamethylenetetramine(HMTA) or tartaric acid was used as the chelating agent during leaching. Both leaching and precipitation processes were optimized individually. For leaching process, the effects of two different chelating agents, the concentrations of leaching agent, chelating agent, and temperature on the extraction and recovery yields were investigated. The optimized process based on the factorial experiment was determined to be the hydrochloric acid concentration of 6 mol/L, the tartaric acid concentration of 50 g/L, and the temperature of 313 K, by which the extraction yields of Fe and REEs up to 67.99% and 99.27%, respectively, are obtained. For the precipitation process, the optimized oxalic acid dosage and pH value were also determined. The produced RE oxide products have the purity and recovery yield up to 95.83% and 90.18%,respectively. These results indicate that the present method with low acid consumption and high product purity has advantages over many other approaches for REE recovery.展开更多
We investigated the structural and magnetic properties of Sm（Co0.7Fe0.1Ni0.12Zr0.04B0.04）7.5 melt spun ribbons. Samples were arc melted then melt spun at 37 m/s up to 55 m/s to obtain ribbon for powdering. Annealing...We investigated the structural and magnetic properties of Sm（Co0.7Fe0.1Ni0.12Zr0.04B0.04）7.5 melt spun ribbons. Samples were arc melted then melt spun at 37 m/s up to 55 m/s to obtain ribbon for powdering. Annealing was performed in argon atmosphere for 30- 75 min at 600-870 oC. In as-spun ribbons the hexagonal SmCo7 （TbCu7-type of structure） of crystal structure was determined from x-ray diffraction patterns, while fcc-Co has been identified as a secondary phase. After annealing, the 1：7 phase of the as-spun ribbons transformed into 2：17 and 1：5 phases. X-ray patterns for as-milled powders exhibited very broad peaks making it difficult to identify a precise structure but repre-sented the 1：7 structure after annealing at low temperature （650 oC）. TEM analysis showed a homogeneous nanocrystalline microstructure with average grain size of 30-80 nm. Coercivity values of 15-27 kOe were obtained from hysteresis loops traced up to a field of 5 T. The co-ercivity decreased as temperature increases, but it maintained values higher than 5 kOe at 380 oC. The maximum energy product at room temperature increased, as high as 7.2 MGOe, for melt-spun isotropic ribbons produced at higher wheel speeds. Anisotropic ribbons had a maximum energy product close to 12 MGOe.展开更多
A reciprocating magnetic refrigerator was developed based on the active magnetic regeneration technology. Rare earth metal Gd and intermetallic compound LaFe11.2Co0.7Si1.1 were used as the magnetic operating materials...A reciprocating magnetic refrigerator was developed based on the active magnetic regeneration technology. Rare earth metal Gd and intermetallic compound LaFe11.2Co0.7Si1.1 were used as the magnetic operating materials in the machine. The particles of the magnetic operating materials, with diameter of 0.5-2 mm and total mass of 950 g, were mounted in the cooling bed. A magnetic field was assembled using NdFeB rare earth permanent magnets. It had the magnetic field space of Φ 34×200 and the magnetic induction of 1.5 T. The water at pH=10 is used as a heat transfer fluid. When the ambient temperature is 296 K, a temperature span of 18 K was achieved after operation of 45 min at a frequency of 0.178 Hz. The temperature span and the output power increase significantly with the increasing velocity of heat transfer.展开更多
基金Projects supported by the Guangdong Provincial Science and Technology Program(2015B010105008)the Dongguan Innovative Research Team Program(201536000200027)
文摘A leaching and selective precipitation approach is proposed in this work to recover rare earth elements(REEs) from NdFeB magnet wastes collected from industry. Hydrochloric acid and oxalic acid were employed as the leaching and precipitation agents, respectively. Hexamethylenetetramine(HMTA) or tartaric acid was used as the chelating agent during leaching. Both leaching and precipitation processes were optimized individually. For leaching process, the effects of two different chelating agents, the concentrations of leaching agent, chelating agent, and temperature on the extraction and recovery yields were investigated. The optimized process based on the factorial experiment was determined to be the hydrochloric acid concentration of 6 mol/L, the tartaric acid concentration of 50 g/L, and the temperature of 313 K, by which the extraction yields of Fe and REEs up to 67.99% and 99.27%, respectively, are obtained. For the precipitation process, the optimized oxalic acid dosage and pH value were also determined. The produced RE oxide products have the purity and recovery yield up to 95.83% and 90.18%,respectively. These results indicate that the present method with low acid consumption and high product purity has advantages over many other approaches for REE recovery.
基金Project supported by HITEMAG European project (G5RD-CT-2000-002B)DARPA Metamaterials program (ADA458377)
文摘We investigated the structural and magnetic properties of Sm（Co0.7Fe0.1Ni0.12Zr0.04B0.04）7.5 melt spun ribbons. Samples were arc melted then melt spun at 37 m/s up to 55 m/s to obtain ribbon for powdering. Annealing was performed in argon atmosphere for 30- 75 min at 600-870 oC. In as-spun ribbons the hexagonal SmCo7 （TbCu7-type of structure） of crystal structure was determined from x-ray diffraction patterns, while fcc-Co has been identified as a secondary phase. After annealing, the 1：7 phase of the as-spun ribbons transformed into 2：17 and 1：5 phases. X-ray patterns for as-milled powders exhibited very broad peaks making it difficult to identify a precise structure but repre-sented the 1：7 structure after annealing at low temperature （650 oC）. TEM analysis showed a homogeneous nanocrystalline microstructure with average grain size of 30-80 nm. Coercivity values of 15-27 kOe were obtained from hysteresis loops traced up to a field of 5 T. The co-ercivity decreased as temperature increases, but it maintained values higher than 5 kOe at 380 oC. The maximum energy product at room temperature increased, as high as 7.2 MGOe, for melt-spun isotropic ribbons produced at higher wheel speeds. Anisotropic ribbons had a maximum energy product close to 12 MGOe.
基金This project was supported financially by the "863"project Ministry of Science and Technology(2002AA324010).
文摘A reciprocating magnetic refrigerator was developed based on the active magnetic regeneration technology. Rare earth metal Gd and intermetallic compound LaFe11.2Co0.7Si1.1 were used as the magnetic operating materials in the machine. The particles of the magnetic operating materials, with diameter of 0.5-2 mm and total mass of 950 g, were mounted in the cooling bed. A magnetic field was assembled using NdFeB rare earth permanent magnets. It had the magnetic field space of Φ 34×200 and the magnetic induction of 1.5 T. The water at pH=10 is used as a heat transfer fluid. When the ambient temperature is 296 K, a temperature span of 18 K was achieved after operation of 45 min at a frequency of 0.178 Hz. The temperature span and the output power increase significantly with the increasing velocity of heat transfer.
