2020, Volume 6, Issue 2
Engineering >> 2020, Volume 6, Issue 2 doi: 10.1016/j.eng.2019.11.007
An Efficient Process for Recycling Nd–Fe–B Sludge as High-Performance Sintered Magnets
a College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China
b State Key Laboratory of Rare Earth Permanent Magnetic Materials, Hefei 231500, China
c Key Laboratory of Advanced Functional Materials, Ministry of Education, Beijing University of Technology, Beijing 100124, China
d Earth-Panda Advanced Magnetic Materials Co., Ltd., Hefei 231500, China
Next Previous
Abstract
Given the increasing concern regarding the global decline in rare earth reserves and the environmental burden from current wet-process recycling techniques, it is urgent to develop an efficient recycling technique for leftover sludge from the manufacturing process of neodymium-iron-boron (Nd–Fe–B) sintered magnets. In the present study, centerless grinding sludge from the Nd–Fe–B sintered magnet machining process was selected as the starting material. The sludge was subjected to a reduction-diffusion (RD) process in order to synthesize recycled neodymium magnet (Nd2Fe14B) powder; during this process, most of the valuable elements, including neodymium (Nd), praseodymium (Pr), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and cobalt (Co), were recovered simultaneously. Calcium chloride (CaCl2) powder with a lower melting point was introduced into the RD process to reduce recycling cost and improve recycling efficiency. The mechanism of the reactions was investigated systematically by adjusting the reaction temperature and calcium/sludge weight ratio. It was found that single-phase Nd2Fe14B particles with good crystallinity were obtained when the calcium weight ratio (calcium/sludge) and reaction temperature were 40 wt% and 1050 °C, respectively. The recovered Nd2Fe14B particles were blended with 37.7 wt% Nd4Fe14B powder to fabricate Nd–Fe–B sintered magnets with a remanence of 12.1 kG, and a coercivity of 14.6 kOe, resulting in an energy product of 34.5 MGOe. This recycling route promises a great advantage in recycling efficiency as well as in cost.
Keywords
Nd–Fe–B grinding sludge Recycled sintered magnets ; Calcium reduction-diffusion ; Rare-earth-rich alloy doping
Figures
Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
References
[ 1 ] Gutfleisch O, Willard MA, Brück E, Chen CH, Sankar SG, Liu JP. Magnetic materials and devices for the 21st century: stronger, lighter, and more energy efficient. Adv Mater 2011;23(7):821–42. link1
[ 2 ] Jones N. Materials science: the pull of stronger magnets. Nature 2011;472 (7341):22–3. link1
[ 3 ] Coey JMD. Hard magnetic materials: aperspective. IEEE Trans Magn 2011;47 (12):4671–81. link1
[ 4 ] Nakamura H. The current and future status of rare earth permanent magnets. Scr Mater 2017;154:273–6. link1
[ 5 ] Dong SZ, Li W, Chen HS, Han R. The status of Chinese permanent magnet industry and R&D activities. AIP Adv 2017;7(5):056237. link1
[ 6 ] Itoh M, Miura K, Machida K. Novel rare earth recovery process on Nd–Fe–B magnet scrap by selective chlorination using NH4Cl. J Alloys Compd 2009;477 (1–2):484–7. link1
[ 7 ] Li XT, Yue M, Liu WQ, Li XL, Yi XF, Huang XL, et al. Large batch recycling of waste Nd–Fe–B magnets to manufacture sintered magnets with improved magnetic properties. J Alloys Compd 2015;649:656–60. link1
[ 8 ] Zakotnik M, Tudor CO. Commercial-scale recycling of NdFeB-type magnets with grain boundary modification yields products with ‘‘designer properties” that exceed those of starting materials. Waste Manag 2015;44:48–54. link1
[ 9 ] Takeda O, Okabe TH. Current status on resource and recycling technology for rare earths. Metall Mater Trans E 2014;1(2):160–73. link1
[10] Binnemans K, Jones PT, Blanpain B, Van Gerven T, Yang Y, Walton A, et al. Recycling of rare earths: a critical review. J Clean Prod 2013;51:1–22. link1
[11] Belova VV. Development of solvent extraction methods for recovering rare earth metals. Theor Found Chem Eng 2017;51(4):599–609. link1
[12] Jha MK, Kumari A, Panda R, Rajesh Kumar J, Yoo K, Lee JY. Review on hydrometallurgical recovery of rare earth metals. Hydrometallurgy 2016;161:77–101. link1
[13] Kim D, Powell LE, Delmau LH, Peterson ES, Herchenroeder J, Bhave RR. Selective extraction of rare earth elements from permanent magnet scraps with membrane solvent extraction. Environ Sci Technol 2015;49(16):9452–9. link1
[14] Vahidi E, Zhao F. Environmental life cycle assessment on the separation of rare earth oxides through solvent extraction. J Environ Manage 2017;203(Pt 1):255–63. link1
[15] Bian YY, Guo SQ, Jiang L, Tang K, Ding WZ. Extraction of rare earth elements from permanent magnet scraps by FeO-B2O3 flux treatment. J Sustain Metall 2015;1(2):151–60. link1
[16] Hua ZS, Wang J, Wang L, Zhao Z, Li XL, Xiao YP, et al. Selective extraction of rare earth elements from NdFeB scrap by molten chlorides. ACS Sustain Chem Eng 2014;2(11):2536–43. link1
[17] Sun GF, Chen JF, Dahl W, Klaar HJ, Burchard WG. The synthesis of Nd–Fe–Co–B by reduction–diffusion and its magnetic properties. J Appl Phys 1988;64 (10):5519–21. link1
[18] Asabe K, Saguchi A, Takahashi W, Suzuki RO, Ono K. Recycling of rare earth magnet scraps: part I carbon removal by high temperature oxidation. Mater Trans 2001;42(12):2487–91. link1
[19] Suzuki RO, Saguchi A, Takahashi W, Yagura T, Ono K. Recycling of rare earth magnet scraps: part II oxygen removal by calcium. Mater Trans 2001;42 (12):2492–8. link1
[20] Saguchi A, Asabe K, Takahashi W, Suzuki RO, Ono K. Recycling of rare earth magnet scraps part III carbon removal from Nd magnet grinding sludge under vacuum heating. Mater Trans 2002;43(2):256–60. link1
[21] Saguchi A, Asabe K, Fukuda T, Takahashi W, Suzuki RO. Recycling of rare earth magnet scraps: carbon and oxygen removal from Nd magnet scraps. J Alloys Compd 2006;408–412:1377–81. link1
[22] Yin XW, Liu M, Wan BC, Zhang Y, Liu WQ, Wu YF, et al. Recycled Nd–Fe–B sintered magnets prepared from sludges by calcium reduction–diffusion process. J Rare Earths 2018;36(12):1284–91. link1
[23] Yue M, Yin XW, Li XT, Li M, Li XL, Liu WQ, et al. Recycling of Nd–Fe–B sintered magnets sludge via the reduction–diffusion route to produce sintered magnets with strong energy density. ACS Sustain Chem Eng 2018;6(5):6547–53. link1
[24] Zhong Y, Chaudhary V, Tan X, Parmar H, Ramanujan RV. Mechanochemical synthesis of high coercivity Nd2(Fe,Co)14B magnetic particles. Nanoscale 2017;9(47):18651–60. link1
[25] Lin JH, Liu SF, Cheng QM, Qian XL, Yang LQ, Su MZ. Preparation of Nd–Fe–B based magnetic materials by soft chemistry and reduction–diffusion process. J Alloys Compd 1997;249(1–2):237–41. link1
[26] Km CW, Km YH, Cha HG, Kang YS. Study on synthesis and magnetic properties of Nd–Fe–B alloy via reduction–diffusion process. Phys Scr 2007; T129:321–5. link1
[27] Chen CJ, Liu TY, Hung YC, Lin CH, Chen SH, Wu CD. Effect of CaCl2 and NdCl3 on the manufacturing of Nd–Fe–B by the reduction–diffusion process. J Appl Phys 1991;69(8):5501–3. link1
[28] Chen CQ, Kim D, Choi C. Influence of Ca amount on the synthesis of Nd2Fe14B particles in reduction–diffusion process. J Magn Magn Mater 2014;355:180–3. link1
[29] Claude E, Ram S, Gimenez I, Chaudoüet P, Boursier D, Joubert JC. Evidence of a quantitative relationship between the degree of hydrogen intercalation and the coercivity of the two permanent magnet alloys Nd2Fel4B and Nd2Fe11Co3B. IEEE Trans Magn 1993;29(6):2767–9. link1
[30] Ram S, Joubert JC. Production of substantially stable Nd–Fe–B hydride (magnetic) powders using chemical dissociation of water. Appl Phys Lett 1992;61(5):613–5. link1
[31] Mottram RS, Kianvash A, Harris IR. The use of metal hydrides in powder blending for the production of NdFeB-type magnets. J Alloys Compd 1999;283 (1–2):282–8. link1
[32] Kianvash A, Mottram RS, Harris IR. Densification of a Nd13Fe78NbCoB7-type sintered magnet by (Nd,Dy)-hydride additions using a powder blending technique. J Alloys Compd 1999;287(1–2):206–14. link1
[33] Li C, Liu WQ, Yue M, Liu YQ, Zhang DT, Zuo TY. Waste Nd–Fe–B sintered magnet recycling by doping with rare earth rich alloys. IEEE Trans Magn 2014;50(12):1–3. link1
京公网安备 11010502051620号
