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Zhang P.,Hefei University of Technology | Zhang P.,Anhui Earth Panda Advance Magnetic Material Co. | Zhang P.,Anhui Province Key Laboratory of Rare Earth Permanent Magnet Materials | Liu J.,Hefei University of Technology | And 7 more authors.
Surface and Coatings Technology | Year: 2015

An Al coating was achieved on NdFeB substrate via plasma assisted physical vapor deposition method. The coatings were treated with trivalent chromium passivation and were characterized by a scanning electron microscope equipped with an energy dispersive spectrometer. The adhesive strength between the coatings and NdFeB substrates was evaluated by tensile test. The coatings achieve much higher adhesive strength (25.7MPa) than that of Al coating without plasma assistance. The anticorrosive property of the coatings was studied by electrochemical impedance spectroscopy, neutral salt spray and potentiodynamic polarization curve tests. The corrosion current density of the passivated Al coated NdFeB specimens is 0.2205μA·cm-2, which is two orders of magnitude lower than that of bare NdFeB substrates. Also, the NSS and EIS tests confirm the excellent anticorrosive properties of the Al coated NdFeB specimens with plasma assisted physical vapor deposition method. © 2015 Elsevier B.V.


Li C.,Beijing University of Technology | Yue M.,Beijing University of Technology | Liu W.,Beijing University of Technology | Zuo T.,Beijing University of Technology | And 4 more authors.
Journal of Material Cycles and Waste Management | Year: 2015

The scrap sintered Nd–Fe–B magnets were recycled as the raw materials for bonded magnets using the hydrogen decrepitation (HD) process. The HD powders have the lowest oxygen and hydrogen content by hydrogenation at 150 °C with 1 bar H2 pressure and dehydrogenation at 600 °C. The powders with the largest particle size (>380 μm) bear the best magnetic properties (Br = 110.59 emu/g, Hcj = 9005.80 Oe). The magnetic properties of the resulting bonded magnet prepared from the above powders were Br = 7.02 kGs, Hcj = 4.56 kOe, (BH)max = 7.13 MGOe. © 2014, Springer Japan.


Liu W.Q.,Beijing University of Technology | Sun H.,Beijing University of Technology | Yi X.F.,Anhui Earth panda Advance Magnetic Material Co. | Liu X.C.,Beijing University of Technology | And 3 more authors.
Journal of Alloys and Compounds | Year: 2010

NdFeB permanent magnets with a small amount of Dysprosium (Dy) nanoparticles doping were prepared by conventional sintered method, and the microstructure and magnetic properties of the magnets were studied. Investigation shows that the coercivity rises gradually, while the remanence decreases simultaneously with increased Dy doping amount. As a result, the magnet with 1.5 wt.% Dy exhibits optimal magnetic properties. Further investigation presumed that Dy is enriched as (Nd, Dy)2Fe 14B phase in the surface region of the Nd2Fe 3,4B matrix grains indicated by the enhancement of the magnetocrystalline anisotropy field of the Nd2Fe3,4B phase. As a result, the magnet doped with a small amount ofDy nanoparticles possesses remarkably enhanced coercivity without sacrificing its magnetization noticeably. © 2010 Elsevier B.V. All rights reserved.


Li Z.,Beijing University of Technology | Liu W.,Beijing University of Technology | Zha S.,Beijing University of Technology | Li Y.,Beijing University of Technology | And 6 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2015

(Nd1-xCex)30Fe69B (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) alloys were prepared by inducting melting, and the effect of substitution of Ce for Nd on their microstructure and intrinsic magnetic properties were investigated. With the increase of Ce content, Curie temperature (Tc) decreases from 582.4 to 504.8 K, saturation magnetization (Ms) decreases from 15.88 to 12.71 kGs, and anisotropy field (HA) decreases from 67.4 to 52.7 kOe. However, the reductions of the intrinsic magnetic properties are relatively gentle, and they still have potential to be prepared as permanent magnets. Moreover, further microstructure observations show that Ce is tending to diffuse into the Nd-rich grain boundary phase instead of main phase during the substitute process. Such aggregation behavior is beneficial to fabricate Ce containing magnet with high Ms. © 2015 Elsevier B.V. All rights reserved.


Wang Z.,Beijing University of Technology | Liu W.-Q.,Beijing University of Technology | Zhang D.-T.,Beijing University of Technology | Yue M.,Beijing University of Technology | And 4 more authors.
Rare Metals | Year: 2016

Nd–Fe–B permanent magnets doped with CuZn5 powders were prepared via conventional sintered method. The effects of CuZn5 contents on magnetic properties and corrosion resistance of the magnets were systematically studied. It shows that the remanence, coercivity, and maximum energy product decrease gradually with the increase in CuZn5 doping content. The magnet’s corrosion kinetics in autoclaves environment and its electrochemical properties in electrolytes were also examined. It is interesting to see that the weight loss of 3.5 wt% and 4.5 wt% CuZn5 powders doping magnets is only 1 and 0 mg·cm−2 after autoclaves test at 121 °C, 2 × 105 Pa for 500 h, respectively, which is much lower than that of the magnets without CuZn5 doping. Electrochemical results show that the CuZn5 powders doping magnets display more positive corrosion potential (Ecorr) and lower corrosion current density (Icorr) than those of the original magnets without CuZn5 doping in sulphuric acid electrolyte and distilled water. It is, therefore, concluded that doping CuZn5 powders is a promising way to enhance the corrosion resistance of sintered Nd–Fe–B magnets. © 2016 The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg


Wang L.,Beijing University of Technology | Chen J.,Anhui Earth panda Advance Magnetic Material Co. | Yue M.,Beijing University of Technology | Liu R.,Beijing University of Technology | And 5 more authors.
Journal of Rare Earths | Year: 2011

Crystallographic alignment and magnetic anisotropy were studied for Nd xFe94-xB6 (x=8, 9, 10, 11) ribbons prepared via melt-spinning. Effect of Nd content and wheel speed on the crystal structure and magnetic properties of the ribbons was investigated. Both the free and wheel side of the ribbons could obtain strong c-axis crystal texture of Nd 2Fe14B phase perpendicular to the ribbons surface at low wheel speed, but the texture weakened gradually with the increase of the wheel speed. Increase of Nd content led to better formation of crystal texture in the ribbons, indicating that the α-Fe phase might undermine the formation of crystal texture. Magnetic measurement results showed that the magnetic anisotropy of the ribbons exhibited corresponding behavior with the invariance of the c-axis crystal texture of Nd2Fe14B phase in the ribbons, and the coercivity of the ribbons rose with the increase of both Nd content and wheel speed during melt-spun process. © 2011 The Chinese Society of Rare Earths.


Liu R.,Beijing University of Technology | Chen J.,Anhui Earth Panda Advance Magnetic Material Co | Deng Y.,Beijing University of Technology | Na R.,Beijing University of Technology | And 3 more authors.
Journal of Rare Earths | Year: 2010

Ternary Tb-Fe-B ribbons were prepared via melt-spun technique under different wheel speeds of 5-25 m/s. Effect of wheel speed on the crystal structure and microstructure of the ribbons was investigated. All the ribbons quenched under different wheel speeds crystallized in single Tb 2Fe14B phase with tetragon structure. Different crystallographic alignment evolutions were observed in the free side surface and wheel side surface of the ribbons. On the free-side surface, an in-plane c-axis crystal texture of Tb2Fe14B phase was found in the ribbons quenched at 5 m/s. However, with the increase in the wheel speed, the direction of the c-axis texture turns to perpendicular to the ribbon surface. On the wheel-side surface, a strong c-axis texture perpendicular to the ribbon surface was observed in the ribbons quenched at 5 m/s, and then weakened gradually with the increase in the wheel speed. Further investigation showed that the competition of the two types of temperature gradients during the quench process was responsible for the crystallographic alignment evolution in the ribbons. © 2010 The Chinese Society of Rare Earths.


Patent
Beijing University of Technology and Anhui Earth Panda Advance Magnetic Material Co. | Date: 2016-11-09

The present invention discloses a short process preparation technology of sintered NdFeB magnets from the NdFeB sludge, which relates to a field of recycle technology of NdFeB sludge. The present invention comprises the following steps: water bath distillation of organics in sludge, ultrasonic cleaning, calcium reduction and diffusion, ultrasonic rinsing in a magnetic field and drying, powders mixing and sintering. NdFeB sludge as raw materials was directly prepared from recycled sintered magnets with high magnetic properties. Most of the organics in the sludge could be removed by a vacuum distillation process with stepwise heating. The ultrasonic rinsing process in a magnetic field could effectively remove the remaining organics. The recycled sintered magnets exhibited good maximum energy product [(BH)_(max)] of 35.26 MGOe. The present invention has important features, such as the short processing time, efficient environmental protection, high recycling rate and effective utilization rate of rare earth metals.


Patent
Beijing University of Technology and Anhui Earth Panda Advance Magnetic Material Co. | Date: 2016-04-19

The present invention discloses a short process preparation technology of sintered NdFeB magnets from the NdFeB sludge, which relates to a field of recycle technology of NdFeB sludge. The present invention comprises the following steps: water bath distillation of organics in sludge, ultrasonic cleaning, calcium reduction and diffusion, ultrasonic rinsing in a magnetic field and drying, powders mixing and sintering. NdFeB sludge as raw materials was directly prepared from recycled sintered magnets with high magnetic properties. Most of the organics in the sludge could be removed by a vacuum distillation process with stepwise heating. The ultrasonic rinsing process in a magnetic field could effectively remove the remaining organics. The recycled sintered magnets exhibited good maximum energy product [(BH)_(max)] of 35.26 MGOe. The present invention has important features, such as the short processing time, efficient environmental protection, high recycling rate and effective utilization rate of rare earth metals.


Trademark
Anhui Earth Panda Advance Magnetic; Material Co. | Date: 2013-11-12

Magnets; magnetic material and apparatus; electric sound compounding piece; loudspeakers; insert earphones; acoustic pickups; vibrating membranes; microphones; megaphone; horn speakers.

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