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Enhancement of corrosion resistance in sintered Nd-Fe-B permanent magnet doping with different CuZn5 contents 被引量:7
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作者 Zhuang Wang Wei-Qiang Liu +3 位作者 Dong-Tao Zhang Ming Yue Xiu-Lian Huang Xu-Liang Li 《Rare Metals》 SCIE EI CAS CSCD 2017年第10期812-815,共4页
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 sys- tematically stu... 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 sys- tematically 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 ℃, 2 × 10^5 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 (Eoorr) 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. 展开更多
关键词 Sintered Nd-Fe-B magnet Corrosion resistance CuZn5 powders AUTOCLAVE Polarization characteristics
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Correlation of mechanical anisotropy with fine grain strengthening for Sm_(2)Co_(17)-type sintered permanent magnets 被引量:3
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作者 Lei Wang Chao Wang +4 位作者 Qiangfeng Li Youhao Liu Yikun Fang Xiaofei Yi Wei Li 《Journal of Rare Earths》 SCIE EI CAS CSCD 2022年第10期1584-1591,共8页
The as-solution-treated Sm_(2)Co_(17)-type magnets exhibiting a single 1:7 H phase with different average grain sizes(D) were designed.Anisotropy of bending strength(R_(bb))and compressive strength(R_(mc)) of the magn... The as-solution-treated Sm_(2)Co_(17)-type magnets exhibiting a single 1:7 H phase with different average grain sizes(D) were designed.Anisotropy of bending strength(R_(bb))and compressive strength(R_(mc)) of the magnets were investigated.Moreover,the R_(bb) increases from 86 to 173 MPa with D decreasing from~52 to~18 μm for group c//h samples.The Hall-Petch correlation was employed to reveal the effect of grain size on mechanical properties of the magnets,giving deep understanding of the mechanical anisotropy characteristics.The relatively high Hall-Petch coefficient K^(Rbb)(0.79 MPa·m^(1/2)) gives rise to the largest R_(bb)(173 MPa) for group c//h samples.The mechanical anisotropy of the samples is well explained based on crystal structure and grain size features(grain boundaries).Grain refinement is an effective way to enhance the mechanical properties of Sm_(2)Co_(17)-type sintered magnets. 展开更多
关键词 Sm_(2)Co_(17)-type permanent magnets Grain refinement Bending strength Compressive strength ANISOTROPY Rare earths
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Coercivity enhancement mechanism of grain boundary diffused Nd-Fe-B sintered magnets by magnetic domain evolution observation 被引量:2
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作者 Weiqiang Liu Yi Li +6 位作者 Dan Wu Ming Yue Zhanjia Wang Shanshun Zha Youhao Liu Xiaofei Yi Yihui Du 《Journal of Rare Earths》 SCIE EI CAS CSCD 2021年第6期682-688,I0003,共8页
The grain boundary diffusion(GBD) technology was used to prepare high performance Nd-Fe-B sintered magnets by NdH3 and TbH3 nanoparticle diffusion.The factors affecting the coercivity of GBD magnets include distributi... The grain boundary diffusion(GBD) technology was used to prepare high performance Nd-Fe-B sintered magnets by NdH3 and TbH3 nanoparticle diffusion.The factors affecting the coercivity of GBD magnets include distribution of rare earth rich grain boundary phase and substitution of the heavy rare earth.In order to distinguish the influence of various factors on the coercivity,the microstructure and magnetic domain evolution of the original,reference,Nd-diffused,and Tb-diffused magnets were analyzed.The core-shell structure formed by heavy rare earth substitution is the main factor of coercivity enhancement,and it can transform the magnetic domain reversal mode from easy-nucleation(EN) to difficultnucleation(DN).With increasing the diffusion depth,the shell of the core-shell structure gradually becomes thinner,DN grains gradually decrease while the EN grains gradually increase,indicating that the magnetic domain reversal mode is directly related to the core-shell structure. 展开更多
关键词 Nd-Fe-B sintered magnet Heavy rare earth COERCIVITY Grain boundary diffusion Core-shell structure Magnetic domain reversal
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An Efficient Process for Recycling Nd-Fe-B Sludge as High-Performance Sintered Magnets 被引量:1
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作者 Xiaowen Yin Ming Yue +8 位作者 Qingmei Lu Min Liu Feng Wang Yubing Qiu Weiqiang Liu Tieyong Zuo Shanshun Zha Xuliang Li Xiaofei Yi 《Engineering》 SCIE EI 2020年第2期165-172,共8页
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 ... 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℃,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(1 G=1×10^-4T),and a coercivity of 14.6 kOe(1 Oe=79.6A·m^-1),resulting in an energy product of 34.5 MGOe.This recycling route promises a great advantage in recycling efficiency as well as in cost. 展开更多
关键词 ND-FE-B GRINDING SLUDGE Recycled sintered MAGNETS CALCIUM reduction-diffusion Rare-earth-rich alloy doping
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Enhanced magnetic properties of anisotropic Nd-Fe-B nanocomposites by Fe(C)coating 被引量:1
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作者 Fengqing Wang Guiping Tang +4 位作者 Baoru Bian Lulu Yao Youhao Liu Qiang Zheng Juan Du 《Journal of Rare Earths》 SCIE EI CAS CSCD 2020年第1期84-89,共6页
Nanostructured anisotropic Nd-Fe-B/Fe(C) composite powders were prepared by coating Fe(C) softmagnetic nanoparticles on HDDR Nd-Fe-B hard magnetic powders using iron pentacarbonyl Fe(CO)5 as soft-phase precursor.The e... Nanostructured anisotropic Nd-Fe-B/Fe(C) composite powders were prepared by coating Fe(C) softmagnetic nanoparticles on HDDR Nd-Fe-B hard magnetic powders using iron pentacarbonyl Fe(CO)5 as soft-phase precursor.The effect of Fe(CO)5-loading amount on soft-phase purity,coating morphology and magnetic properties of the composite powders was investigated.Dense and continuous Fe(C) softphase coatings with average particle sizes of 58-68 nm are obtained at Fe(CO)5 loading amounts of x <12 wt%,leading to enhanced remanence and improved energy product of the coated powders.Positive value in δM-plots and single-phase-like demagnetization curves are observed in the Nd-Fe-B/Fe(C) composite powders,indicating the exchange coupling effect between the coated Fe(C) soft phases and the Nd-Fe-B hard phase. 展开更多
关键词 Permanent magnet ANISOTROPY Nanocompo site COATING Thermal decomposition Rare earths
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A facile process to optimize performance of regenerated Nd-Fe-B sintered magnets:Chemo-selective dissolution washing
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作者 Haibo Xu Qingmei Lu +9 位作者 Lichao Yu Liying Cong Haowen Tian Weiqiang Liu Youhao Liu Yunqiao Wang Jingwu Chen Xiaofei Yi Qiong Wu Ming Yue 《Journal of Rare Earths》 SCIE EI CAS CSCD 2023年第12期1976-1983,I0006,共9页
In this work,the recycled Nd-Fe-B powders and regenerated Nd-Fe-B sintered magnets with low impurity content were successfully prepared from Nd-Fe-B magnet sludge via reduction diffusion(RD)method followed by a chemo-... In this work,the recycled Nd-Fe-B powders and regenerated Nd-Fe-B sintered magnets with low impurity content were successfully prepared from Nd-Fe-B magnet sludge via reduction diffusion(RD)method followed by a chemo-selective dissolution washing proc ess.The chemo-selective dissolution effect of various solution(deionized water,dilute acetic acid solution,NH_(4)Cl-methanol solution) was evaluated by impurity content and magnetic properties of the recycled Nd-Fe-B powder.The NH_(4)Cl-methanol solution can selectively remove impurities with minimal damage to the magnetic phase.Besides,the optimal NH_(4)Cl concentration and liquid-to-solid ratio were investigated.As a consequence,the contents of Ca,O,and H after optimal washing process are reduced to 0.07 wt%,0.31 wt% and 0.22 wt%,respectively.Hence,M_(3) Tis increased to 146.72 emu/g,which is 33% higher than that of the initial sludge.Then,the regenerated Nd-Fe-B sintered magnets with properties of B_(r)=11.66 kG,H_(cj)=16.49 kOe,and(BH)_(m)=31.78 MGOe were successfully prepared by mixing with 40 wt% Nd4Fe14B alloy powders.Compared with the corresponding regenerated magnets washed with deionized water,the remanence and coercivity are increased by 18% and 59%,respectively. 展开更多
关键词 Recycling Nd-Fe-B magnet Sludge Chemo-selective dissolution Washing process Magnetic properties Reduction diffusion Rare earths
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Study on preparation and properties of CeO_2/epoxy resin composite coating on sintered NdFeB magnet 被引量:11
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作者 Pengjie Zhang Minggang Zhu +5 位作者 Wei Li Guangqing Xu Xiulian Huang Xiaofei Yi Jingwu Chen Yucheng Wu 《Journal of Rare Earths》 SCIE EI CAS CSCD 2018年第5期544-551,共8页
The CeO2/epoxy resin composite coating was deposited on NdFeB substrate by cathode electrophoresis method for enhancing the anticorrosion and anti-wear performances. The morphologies and structures were characterized ... The CeO2/epoxy resin composite coating was deposited on NdFeB substrate by cathode electrophoresis method for enhancing the anticorrosion and anti-wear performances. The morphologies and structures were characterized by a scanning electron microscope and an X-ray diffractometer. The micro hardness of the composite coating was evaluated by a microhardness tester. The corrosive behaviors of the coatings were studied by potentiodynamic polarization curve, electrochemical impedance spectroscopy and neutral salt spray tests. The concentration of CeO2 nanoparticles(NPs) in the electrophoresis bath was optimized according to the coating structures and anticorrosion performances. The results show that CeO2 NPs can enhance the microhardness of the composite coatings. Moreover, the nanoparticles disperse uniformly in the matrix when the concentration is lower than 30 g/L. The microhardness of CeO2/epoxy resin(30 g/L) composite coating is about 63% higher than that of the blank epoxy resin coating. And the NSS time of the CeO2/epoxy resin(30 g/L) composite coated sample can reach 1248 h.Meanwhile, the composite coatings possess no deteriorate influence on the magnetic properties of NdFeB substrates. The anticorrosion mechanisms of the composite coatings on the NdFeB substrate are deeply discussed. 展开更多
关键词 Sintered NdFeB Epoxy resin CeO2 nanoparticle Corrosion resistance Rare earths
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Effects of bias voltage on coating structures and anticorrosion performances of PA-PVD Al coated NdFeB magnets 被引量:4
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作者 Yujie Cao Pengjie Zhang +7 位作者 Wei Sun Weifeng Zhang Hanzhong Wei Jiquan Wang Bingshan Li Xiaofei Yi Guangqing Xu Yucheng Wu 《Journal of Rare Earths》 SCIE EI CAS CSCD 2021年第6期703-711,I0004,共10页
Al coated NdFeB magnets were prepared by plasma-assisted-physical-vapor-deposition(PA-PVD)method fo r enhancing the corro sion resistance.Mo rphologies and structures were characterized by an Xray diffractometer and a... Al coated NdFeB magnets were prepared by plasma-assisted-physical-vapor-deposition(PA-PVD)method fo r enhancing the corro sion resistance.Mo rphologies and structures were characterized by an Xray diffractometer and a scanning electron microscope.Corrosion behaviors of the samples with different bias voltages were studied by electrochemical methods and neutral salt spray test,respectively.The bias voltage during the deposition process was optimized according to the coating structures and corrosion resistances.The density and flatness of Al coating increase with increasing the bias voltage,and at the same time the thickness decreases.The coating density and thickness turn to be stable when bias voltage is 1800 V.Also,the corrosion behaviors of PA-PVD Al coatings in different media,such as NaOH,HNO_(3) and NaCl solutions,were studied.The self-corrosion potentials(E_(corr)) of PA-PVD Al coatings almost keep constant in NaOH and HNO_(3) solutions with diffe rent concentrations.However,the self-corrosion current densities(J_(corr)) decrease with the increasing concentrations.E_(corr) shifts to negative potential and J_(corr)decreases gradually when increasing the concentration of NaCl solution.The corrosion mechanisms of Al coatings are discussed based on the corrosion behaviors in different media. 展开更多
关键词 Physical vapor deposition Plasma assistance Al coating Sintered NdFeB Corrosion behavior Rare earths
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Improvement of coercivity and thermal stability of Nd-Fe-B sintered magnets by intergranular addition of Tb80Fe20 alloy 被引量:3
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作者 Ze Duan Haicheng Xuan +4 位作者 Jincai Su Jingwu Chen Xiaofei Yi Youhao Liu Peide Han 《Journal of Rare Earths》 SCIE EI CAS CSCD 2022年第12期1899-1904,I0003,共7页
To improve the coercivity and temperature stability of Nd-Fe-B sintered magnets for high-temperature applications,the eutectic Tb_(80)Fe_(20)(wt%)alloy powders were added into the Nd-Fe-B sintered magnets by intergran... To improve the coercivity and temperature stability of Nd-Fe-B sintered magnets for high-temperature applications,the eutectic Tb_(80)Fe_(20)(wt%)alloy powders were added into the Nd-Fe-B sintered magnets by intergranular method to enhance the coercivity(H_(cj))and thermal stability.The micro structure,magnetic properties and thermal stability of the Nd-Fe-B magnets with different Tb_(80)Fe_(20)contents were studied.The experimental results demonstrate that the coercivity(H_(cj))of the sintered Nd-Fe-B magnet is significantly enhanced from 14.12 to 27.78 kOe,and the remanence(Br)decreases not obviously by introducing 4 wt%Tb_(80)Fe_(20)alloy.Meanwhile,the reversible tempe rature coefficients of coercivity(β)and remanence(α)of the Nd-Fe-B magnets are increased from-0.5634%/℃to-0.4506%/℃and-0.1276%/℃to-0.1199%/℃at 20-170℃,respectively.The Curie temperature(TC)of the Nd-Fe-B magnet is slightly enhanced with the increase of Tb_(80)Fe_(20)content.Moreover,the irreversible flux magnetic loss(hirr)is obviously reduced as Tb80Fe20addition increases.Further analysis of the microstructure reveals that a modified microstructure,i.e.clear and continuous RE-rich grain boundary layer,is acquired in the sintered magnets by introducing Tb_(80)Fe_(20)alloy.The associated mechanisms on improved coercivity and thermal stability were comprehensively researched. 展开更多
关键词 Tb80Fe20 alloy COERCIVITY Nd-Fe-B sintered magnet Thermal stability Rare earths
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Corrosion resistance and mechanical properties of (Ho,Nd)FeB magnets 被引量:2
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作者 Yujie Cao Youhao Liu +5 位作者 Pengjie Zhang Guangqing Xu Jiaqin Liu Jingwu Chen Xiaofei Yi Yucheng Wu 《Journal of Rare Earths》 SCIE EI CAS CSCD 2021年第11期1409-1414,I0004,共7页
(Ho,Nd)FeB magnets with different Ho contents were prepared by Ho substitution for part of Nd during the casting process.Effects of Ho contents on the corrosion resistance and mechanical properties of(Ho,Nd)FeB magnet... (Ho,Nd)FeB magnets with different Ho contents were prepared by Ho substitution for part of Nd during the casting process.Effects of Ho contents on the corrosion resistance and mechanical properties of(Ho,Nd)FeB magnets were analyzed by a highly accelerated aging tester,an electrochemical workstation,a microhardness tester,a bending tester,a scanning electron microscope and an X-ray diffractometer.Results show that the addition of Ho can change the main phase structure,optimize the distribution of rare-earth rich(RE-rich) phases in grain boundary,and improve the corrosion resistance and mechanical properties of NdFeB magnets.When the content of Ho increases from 0 to 21.0 wt%,the weight loss of magnets decreases from 2.672 to 0.933 mg/cm^(2),and the microhardness and bending strength increase from 528.74 HV and 374.92 MPa to 633.84 HV and 459.80 MPa,respectively. 展开更多
关键词 (Ho Nd)FeB magnets Corrosion resistance Mechanical property Microstructure Rare earths
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Coercivity enhancement mechanism of Tb-diffusion Nd-Fe-B sintered magnets studied by magneto-optical Kerr optical microscope 被引量:1
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作者 Dan Wu Wei-Qiang Liu +5 位作者 Ming Yue Qiong Wu Dong-Tao Zhang Qing-Mei Lu Xu-Liang Li Jing-Wu Chen 《Rare Metals》 SCIE EI CAS CSCD 2021年第3期570-574,共5页
The coercivity,microstructure,and magnetic domain structure of Nd-Fe-B sintered magnets by grain boundary diffusion process(GBDP) with TbH3 nanoparticles were systematically investigated.Compared to the original magne... The coercivity,microstructure,and magnetic domain structure of Nd-Fe-B sintered magnets by grain boundary diffusion process(GBDP) with TbH3 nanoparticles were systematically investigated.Compared to the original magnet,the coercivity(Hci) of the GBDP magnets improved from 1702 to 2374 kA·m^(-1) with few remanence reduced from 1.338 to 1.281 T.Electron probe microanalysis(EPMA) analysis showed that Tb diffused along grain boundary,mainly concentrated in the boundary layer of the main phase,and formed a core-shell structure.Magneto-optical Kerr optical microscope(MOKE) analysis showed that there were two types of magnetic domain reversal in one grain:gradual reversal(GR) and abrupt reversal(AR).When the applied field decreased from saturated magnetic field,the reversal magnetic domain nucleated and then spread over the whole grain gradually,which was called GR.However,some grains kept the single domain state until Hh which was a value of reverse direction applied field in second quadrant in hysteresis loops.When the applied field increased above Hh,reversed magnetic domain would suddenly appear and occupy most of the area of the grain,which was called AR.That is because AR grains have higher reversed magnetic domain nucleation field(HRN2) than GR grains(HRN1).After GBDP,the area of AR region increased obviously and GR region decreased accordingly,indicating that the core-shell structure could change GR grain into AR grain.The coreshell structure could suppress flipping of the magnetization of the grains due to the large magnetic anisotropy of Tbrich shell.Therefore,large AR area led to high coercivity. 展开更多
关键词 Coercivity enhancement mechanism Magnetic domain Grain boundary diffusion Nd-Fe-B sintered magnets
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Calcium hydride reduced high-quality Nd-Fe-B powder from Nd-Fe-B sintered magnet sludge 被引量:2
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作者 Haibo Xu Qingmei Lu +7 位作者 Liying Cong Haowen Tian Weiqiang Liu Youhao Liu Yunqiao Wang Jingwu chen Xiaofei Yi Ming Yue 《Journal of Rare Earths》 SCIE EI CAS CSCD 2022年第12期1905-1912,I0004,共9页
The structural and magnetic properties were studied for recycling Nd-Fe-B powders from Nd-Fe-B sintered magnets sludge via reduction diffusion(RD)with calcium hydride(CaH_(2))particles.For comparison,traditional reduc... The structural and magnetic properties were studied for recycling Nd-Fe-B powders from Nd-Fe-B sintered magnets sludge via reduction diffusion(RD)with calcium hydride(CaH_(2))particles.For comparison,traditional reducing agent calcium granules were applied to prepare recycled Nd-Fe-B powders.Finer particle size and better size distribution as well as lower impurity content are achieved by using CaH_(2)instead of Ca.In detail,the average particle size of the recycled Nd-Fe-B powder is reduced from 4.66 to 3.43μm,and the bimodal distribution disappears.Moreover,the residual calcium content and oxygen content are reduced to about 0.080 wt%and 0.32 wt%.As a consequence,the roomtemperature magnetization of the CaH_(2)-recycled Nd-Fe-B powder is increased to 146.30 emu/g,6.8%and 33%,respectively,higher than that of Ca-reduced powder and the initial sludge.Further analysis indicates that CaH_(2)is able to reduce the sludge at lower tempe rature to fabricate well-dispersed,unifo rm recycled powder with high magnetization arising from a combination factors of its low melting point,low thermodynamic behavior,and the release of hydrogen during the reaction. 展开更多
关键词 Recycled Nd-Fe-B powders Magnetic properties Microstructure Reducing agent Reduction diffusion Rare earths
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