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Fabrication of ultrafine Nd-Fe-B powder by a modified reduction-diffusion process 被引量:1
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作者 JANG T.S. LEE D.H. +2 位作者 CHOI C.J. SEO W.S. LEE Y.H. 《Rare Metals》 SCIE EI CAS CSCD 2006年第z2期223-226,共4页
In order to obtain ultrafine Nd-Fe-B powder, a spray-dried precursor was treated by reduction-diffusion (R/D) process. And, unlike the conventional R/D process, calcium reduction that is a crucial step for the formati... In order to obtain ultrafine Nd-Fe-B powder, a spray-dried precursor was treated by reduction-diffusion (R/D) process. And, unlike the conventional R/D process, calcium reduction that is a crucial step for the formation of Nd2Fe14B was performed without conglomerating the precursor with Ca powder. By adopting this modified process, it is possible to synthesize the hard magnetic Nd2Fe14B at the reaction temperature as low as 850 ℃. The average size of Nd2Fe14B particles that are uniformly distributed in the optimally treated powder was <<1 μm. Most Nd2Fe14B particles were enclosed with thin layers of Nd-rich phase. Typical magnetic properties of such powder without eliminating impurity CaO were iHc=~5.9 kOe, Br=~5.5 kG, and (BH)max=~6 MGOe. 展开更多
关键词 NdFeB powder spray drying reduction-diffusion process ND2FE14B magnetic powder
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Microwave absorption properties regulation and bandwidth formula of oriented Y_(2)Fe_(17)N_(3-δ)@SiO_(2)/PU composite synthesized by reduction-diffusion method 被引量:1
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作者 Hao Wang Liang Qiao +4 位作者 Zu-Ying Zheng Hong-Bo Hao Tao Wang Zheng Yang Fa-Shen Li 《Chinese Physics B》 SCIE EI CAS CSCD 2022年第11期341-351,共11页
As concepts closely related to microwave absorption properties,impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms.In this work,red... As concepts closely related to microwave absorption properties,impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms.In this work,reduction–diffusion method was innovatively applied to synthesize rare earth alloy Y_(2)Fe_(17).In order to regulate the electromagnetic parameters of absorbers,the Y_(2)Fe_(17)N_(3-δ)particles were coated with silica(Y_(2)Fe_(17)N_(3-δ)@SiO_(2))and absorbers with different volume fractions were prepared.The relationship between impedance matching,matching thickness,and the strongest reflection loss peak(RLmin)was presented obviously.Compared to the microwave absorption properties of Y_(2)Fe_(17)N_(3-δ)/PU absorber,Y_(2)Fe_(17)N_(3-δ)@SiO_(2)/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness,light weight,strong absorbing intensity,and broad bandwidth.Based on microwave frequency bands,the microwave absorption properties of the absorbers were analyzed and the related parameters were listed.As an important parameter related to perfect matching,reflection factor(√ε_(r)/μ_(r))was discussed combined with microwave amplitude attenuation.According to the origin and mathematical model of bandwidth,the formula of EAB(RL<-10 dB)was derived and simplified.The calculated bandwidths agreed well with experimental results. 展开更多
关键词 microwave absorption rare earth alloy reduction-diffusion method Y_(2)Fe_(17)N_(3-δ)@SiO_(2) reflection factor impedance and phase matching bandwidth formula
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Preparation of DyFe_2 by the Reduction-Diffusion Process 被引量:1
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作者 Guangsi GUO, Guangqiang LI, Zhenqi HUANG, Zhitong SUI and Liang LIU (School of Materials and Metallurgy, Northeastern University, Shenyang 110006, China) Thlin ZHOU (Baotou Research Institute of Rare Earth, Baotou 014010, China) 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2000年第2期181-182,共2页
The free energy change for the reduction-diffusion reaction which was used to prepare the DyFe_2 D_y2 O_3(s) + 3Ca(g) + 4Fe(s) = 3C_aO(s) + 2D_yFe_2(s) intermetallic compound powder was calculated. The reduction-diffu... The free energy change for the reduction-diffusion reaction which was used to prepare the DyFe_2 D_y2 O_3(s) + 3Ca(g) + 4Fe(s) = 3C_aO(s) + 2D_yFe_2(s) intermetallic compound powder was calculated. The reduction-diffusion experiments were carried out at 1073, 1123. 1273 and 1373 K respectively using powders of D_y2O_3, iron, and calcium grains as raw materials. XRD and EDX analysis confirmed that D_yFe_2 was formed by the diffusion of Dy into Fe. 展开更多
关键词 Preparation of DyFe2 by the reduction-diffusion Process
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Preparation of DyFe_2 and TbFe_2 by Reduction-Diffusion Process
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作者 GuangsiGUO GuangtaiWANG ZhitongSUI 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2004年第1期68-70,共3页
The pure intermetallic compounds (Tb1-x;Dyx)Fe2 are super-magnetostriction materials, which were produced from DyFe2 and TbFe2 in this paper. The thermodynamic possibility and kinetic feasible conditions for DyFe2 and... The pure intermetallic compounds (Tb1-x;Dyx)Fe2 are super-magnetostriction materials, which were produced from DyFe2 and TbFe2 in this paper. The thermodynamic possibility and kinetic feasible conditions for DyFe2 and TbFe2 preparation by reduction-diffusion in Ca-Dy2O3-Fe and Ca-Tb4O7-Fe systems were analyzed and the products of DyFe2 and TbFe2 were confirmed by XRD. The contracting core model was applied to describe the reduction-diffusion process in which the diffusion is a rate-controlled step. The apparent activation energies of DyFe2 and TbFe2 processes are 45 and 39 kJ/mol respectively. 展开更多
关键词 Ca-Dy2O3 -Fe Ca-Tb4O7-Pe reduction-diffusion DyFe2 TbFe2 Contracting core model
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Mechanism of reduction-diffusion reaction in Sm-Fe binary system at low temperature using molten salts
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作者 Jungryang Kim Shusuke Okada +1 位作者 Kenta Takagi Kimihiro Ozaki 《Journal of Rare Earths》 SCIE EI CAS CSCD 2024年第10期1889-1894,共6页
In this study,the mechanism of the reduction-diffusion reaction in a Sm-Fe binary system at low temperature was studied to investigate the possibility of synthesis of a Fe-rich TbCu_(7)-type SmFe_(x)(x>9)by the low... In this study,the mechanism of the reduction-diffusion reaction in a Sm-Fe binary system at low temperature was studied to investigate the possibility of synthesis of a Fe-rich TbCu_(7)-type SmFe_(x)(x>9)by the low-temperature diffusion-reduction(LTRD)process using LiCl-KCl eutectic molten salts.Firstly,the Sm-Fe phase transformation depending on the Sm-Fe composition,the LTRD temperature,and time was investigated,and it is found that the obtained metastable phase is only TbCu_(7)-type SmFe_(~8.5),which is not a Fe-rich phase.This Fe content does not change even after an expended LTRD process,and the metastable TbCu_(7)-type SmFe_(~8.5)tends to transform to the stable Sm_(2)Fe_(17)phase.In addition,it is found that the Sm-Fe phase starts to synthesize from the Sm-rich phase in the order of SmFe_(2),SmFe_(3),and SmFe_(8.5)as the LTRD temperature increases(when the time was 10 h)or the LTRD time increases(when the temperature was 550℃).Core-shell-like particles are observed in the case of a short LTRD time,and the core and the shell are Fe and the Sm-rich Sm-Fe phase,respectively,indicating that the Sm-rich phase begins to produce on the surface of the Fe particles.It is difficult to synthesize a Fe-rich TbCu_(7)-type SmFe_(x)(x>9)phase with the Sm-Fe binary system,suggesting that a different approach,such as addition of other elements,will be necessary. 展开更多
关键词 Low-temperature synthesis Synthesis mechanism reduction-diffusion process Molten salts Sm-Fe compounds Rare earths
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Recycled Nd-Fe-B sintered magnets prepared from sludges by calcium reduction-diffusion process 被引量:10
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作者 Xiaowen Yin Min Liu +5 位作者 Baicen Wan Yu Zhang Weiqiang Liu Yufeng Wu Dongtao Zhang Ming Yue 《Journal of Rare Earths》 SCIE EI CAS CSCD 2018年第12期1284-1291,共8页
Environmental friendly recycling process for Nd-Fe-B sintered magnet sludges generated in the manufacturing process, which contain large amount of rare earth, including Nd, Pr and Dy, is badly needed so far. In presen... Environmental friendly recycling process for Nd-Fe-B sintered magnet sludges generated in the manufacturing process, which contain large amount of rare earth, including Nd, Pr and Dy, is badly needed so far. In present study, we have developed an effective route to obtain recycled sintered magnets from Nd-Fe-B sintered magnet sludges by calcium reduction-diffusion(RD) process. Compared to conventional recycling process, our research is focused on recovering most of the useful elements, including Nd, Pr, Dy, Co, and Fe together instead of just rare earth elements. To improve the recycling efficiency and reduce pollution, the co-precipitating parameters were simulated and calculated using MATLAB software. Most of useful elements were recovered by a co-precipitation method, and the obtained composite powders were then directly fabricated as recycled Nd-Fe-B powders by a calcium reduction-diffusion(RD) method. The recovery rates are 98%, 99%, 99%, 93%, and 99%, for Nd, Pr, Dy, Co, and Fe, respectively. The amount of useful elements contained in the recovered composite powders is greater than99.71 wt%. The process of RD for synthesizing NdFeB and subsequently removing CaO was thoroughly investigated. Furthermore, the recycled Nd-Fe-B magnet exhibits a remanence of 1.1 T, a coercivity of1053 kA/m, and an energy product of 235.6 kJ/m~3, respectively, indicating that recycled Nd-Fe-B sintered magnet was successfully recovered from the severely contaminated sludges via an effective recycling route. 展开更多
关键词 Nd-Fe-B sintered magnet sludges reduction-diffusion Removing CaO Recycled magnet Rare earths
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Novel synthesis of single-crystalline TbCu_(7)-type Sm-Fe powder by low-temperature reduction-diffusion process using molten salt 被引量:2
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作者 Shusuke Okada Kenta Takagi 《Journal of Rare Earths》 SCIE EI CAS CSCD 2022年第7期1126-1133,共8页
In this study,molten salt was used as a solvent for calcium(Ca)to let a reduction-diffusion(R-D)reaction occur below the melting point of Ca(1115 K),which is the lower limit temperature of the co nventional RD process... In this study,molten salt was used as a solvent for calcium(Ca)to let a reduction-diffusion(R-D)reaction occur below the melting point of Ca(1115 K),which is the lower limit temperature of the co nventional RD process.When the R-D reaction is conducted below 923 K with LiCl molten salt,submicron-sized TbCu_(7)-type Sm-Fe powder is formed.The c/a ratio of the powder estimated by a synchrotron X-ray diffraction pattern is 0.8456,which is consistent with the Sm_(0.67)Fe_(5.667)(SmFe_(8.5))phase.An electron backscatter diffraction analysis reveals that single-crystalline TbCu_(7)-type SmFe_(8.5) powder was synthesized for the first time. 展开更多
关键词 reduction-diffusion TbCu_(7) Molten salt Permanent magnet Rare earths
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Preparation of Sm_2Fe_(17) alloy by reduction-diffusion process 被引量:1
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作者 Hai-Bo Chen Jing-Wu Zheng +3 位作者 Liang Qiao Yao Ying Li-Qiang Jiang Sheng-Lei Che 《Rare Metals》 SCIE EI CAS CSCD 2018年第11期989-994,共6页
SmFealloy is the intermediate material for the preparation of SmFeNx(x ≈ 3); thus, the synthesis of pure SmFemother alloy is the key to obtaining highperformance SmFeNx. Reduction-diffusion(R-D) is a cost-effective m... SmFealloy is the intermediate material for the preparation of SmFeNx(x ≈ 3); thus, the synthesis of pure SmFemother alloy is the key to obtaining highperformance SmFeNx. Reduction-diffusion(R-D) is a cost-effective method. In this study, the R-D process of synthesizing SmFewas analyzed by scanning electron microscopy(SEM), energy-dispersive X-ray spectroscopy(EDX), X-ray diffraction(XRD), and X-ray fluorescence(XRF). Furthermore, the influences of the tightness of compacted reactants, the compensation amount of SmO,and the particle size of Fe on the formation of SmFewere discussed from the aspects of the three raw materials.The results show that Sm reduced from SmOreacts with Fe particles to form intermetallic compound SmFedirectly in the R-D reaction process of preparing SmFe;the generation of Sm and its migration to the surface of Fe particles control the reaction rate; a proper tightness of compacted reactants is necessary for ensuring the purity of SmFeproduct; pure SmFecan be obtained when the compensation of SmOis 33 % of the stoichiometry; and the sufficiency of the reaction improves with the decrease in the size of Fe powders under the same reaction condition. 展开更多
关键词 Sm_2Fe_(17) reduction-diffusion Rare earth Permanent magnet
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Microwave absorption and bandwidth study of Y_(2)Co_(17)rare earth soft magnetic alloy with easy-plane anisotropy
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作者 马云国 乔亮 +7 位作者 郑祖应 郝宏波 王浩 孙哲 涂成发 王涛 杨正 李发伸 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第8期310-318,共9页
The easy-plane anisotropy of the Y_(2)Co_(17)rare earth soft magnetic alloy has high saturation magnetization and operating frequency,and good impedance matching.Therefore,it is expected to become a kind of high-perfo... The easy-plane anisotropy of the Y_(2)Co_(17)rare earth soft magnetic alloy has high saturation magnetization and operating frequency,and good impedance matching.Therefore,it is expected to become a kind of high-performance microwave absorbing material.In this paper,Y_(2)Co_(17)alloy was prepared by a reduction-diffusion method,and its micropowder was prepared as polyurethane(PU)based composite absorbing materials(Y_(2)Co_(17)/PU composites).The microwave properties of composites with different volume fractions were calculated.The composites showed outstanding absorption characteristics in the range of 20-30 vol%,and the minimum reflection loss(RL)was less than-50 d B.When the volume fraction was25%,the effective absorption bandwidth could cover the X-band at a thickness of 1.5 mm,and the Ku-band at a thickness of1.08 mm.The absorption mechanism was analyzed by the interface reflection model.The RL absorption peak bandwidth mechanism was discussed by using the amplitude relation and calculating the effective absorption bandwidth at different thicknesses.The effective absorption bandwidth values were in good agreement with the theoretical expectation. 展开更多
关键词 reduction-diffusion method microwave absorption interface reflection model effective absorption bandwidth
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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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Preparation of Sm_2Fe_(17)Alloys in Ca-Sm_2O_3-Fe System 被引量:1
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作者 邓庚凤 孙光飞 +3 位作者 陈菊芳 祁毓俊 庞利佳 方克明 《Journal of Rare Earths》 SCIE EI CAS CSCD 2005年第5期530-533,共4页
Thermodynamics and kinetics for the preparation of Sm2Fe17 alloys by reduction-diffusion (R-D) method in CaSm2O3-Fe System were investigated. With increasing reaction temperature, it is found that the reaction rate ... Thermodynamics and kinetics for the preparation of Sm2Fe17 alloys by reduction-diffusion (R-D) method in CaSm2O3-Fe System were investigated. With increasing reaction temperature, it is found that the reaction rate of R-D and the amount of Sm in the Sm2Fe17 alloy increase, and the increased amount at lower temperature is higher than that at higher temperature. Moreover, results from contracting core modal show that the peritectic reaction between Sm and Fe is a ratedetermined step in the whole R-D process. The apparent activation energy and the pre-exponential factor for this reaction are 73.74 kJ· mol^ -1 and 7.79 × 10^- 3 respectively. 展开更多
关键词 rare earth permanent magnet material Sm2Fe17 compound reduction-diffusion contracting core model tare earths
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Synthesis of size-controlled and dispersible Sm_(2)Fe_(17)N_(3) magnetic particles by reduction diffusion process using molten salt
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作者 Junhua Xi Zhi Yang +8 位作者 Muhammad Haseeb Yuanyuan Chen Xiaofeng Nie Liying Cong Qiong Wu Enfeng Fu Hongguo Zhang Weiqiang Liu Ming Yue 《Journal of Rare Earths》 SCIE EI CAS CSCD 2024年第11期2105-2111,I0004,共8页
The synthesis of size-controlled Sm_(2)Fe_(17) magnetic particles is a prerequisite for the fabrication of highperformance Sm_(2)Fe_(17)N_(3) permanent magnetic materials.Here,Sm_(2)Fe_(17) was synthesized using a cos... The synthesis of size-controlled Sm_(2)Fe_(17) magnetic particles is a prerequisite for the fabrication of highperformance Sm_(2)Fe_(17)N_(3) permanent magnetic materials.Here,Sm_(2)Fe_(17) was synthesized using a costeffective reduction-diffusion method.The calcium chloride molten salt was introduced to control the particle size and achieve a single phase of Sm_(2)Fe_(17).The effects of reduction-diffusion reaction temperature and the amount of added calcium chloride on the phase constitution and microstructure of the final product of reduction-diffusion were systematically investigated.Adding an appropriate amount of calcium chloride can effectively inhibit the overgrowth and sintering of the reduced particles.By employing the strategy of adding 20 wt% of calcium chlorides into the green compacts,we were able to successfully synthesize uniform Sm_(2)Fe_(17) particles that are well-dispersed,with an average size of 2.2 μm.Furthermore,by combining the optimal reduction-diffusion conditions and the nitriding process,the hard magnetic Sm_(2)Fe_(17)N_(3) material was successfully obtained.This study could be useful for the development of high-performance Sm_(2)Fe_(17)N_(3) magnetic materials utilizing reduction-diffusion technology. 展开更多
关键词 Sm_(2)Fe_(17)N_(3) reduction-diffusion Rare earths Permanent magnets Molten salt
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Magnetocaloric properties of Nd-doped Gd5Si4 microparticles and nanopowders
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作者 Kaiyang Zhang Huanhuan Wang +1 位作者 Ying Wang Tao Wang 《Chinese Physics B》 SCIE EI CAS 2024年第11期396-402,共7页
The preparation of materials with enhanced magnetocaloric properties is crucial for magnetic refrigeration. In thisstudy, Nd-doped Gd5Si4 microparticles and nanomaterials were synthesized using the reduction–diffusio... The preparation of materials with enhanced magnetocaloric properties is crucial for magnetic refrigeration. In thisstudy, Nd-doped Gd5Si4 microparticles and nanomaterials were synthesized using the reduction–diffusion method. Theimpact of Nd doping with varying compositions on the structure and entropy change properties of the materials was investigated.The Curie temperatures of both the micron- and nano-sized materials ranged from 190 K to 210 K, which were lowerthan previously reported values. Micron-sized samples doped with 1% Nd exhibited superior magnetocaloric properties,demonstrating a maximum entropy change of 4.98 J·kg^(-1)·K^(-1) at 5 T, with an entropy change exceeding 4 J·kg^(-1)·K^(-1)over a wide temperature range of approximately 70 K. Conversely, the nanomaterials had broader entropy change peaks butlower values. All samples exhibited a second-order phase transition, as confirmed by the Arrott plots. 展开更多
关键词 magnetocaloric Gd5Si4 Nd doping reduction-diffusion method
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Corrosion mechanism of H_2O on Sm_2Fe_(17) and nitrogenation process of corroded Sm_2Fe_(17) 被引量:2
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作者 Jianwei Xu Jingwu Zheng +7 位作者 Haibo Chen Liang Qiao Yao Ying Wei Cai Wangchang Li Jing Yu Min Lin Shenglei Che 《Journal of Rare Earths》 SCIE EI CAS CSCD 2019年第6期638-644,共7页
Sm_2 Fe_(17) prepared by reduction-diffusion method needs to be washed with water to remove calcium oxide. Electrochemical corrosion occurs when Sm_2 Fe_(17) powder is in contact with liquid water. Corrosion mechanism... Sm_2 Fe_(17) prepared by reduction-diffusion method needs to be washed with water to remove calcium oxide. Electrochemical corrosion occurs when Sm_2 Fe_(17) powder is in contact with liquid water. Corrosion mechanism of H_2 O on Sm_2 Fe_(17) powder and nitrogenation process of corroded Sm_2 Fe_(17) were studied by analyzing the structure and morphology. It is indicated that the metallic hydroxide forms and deposits on the Sm_2 Fe_(17) powder surfaces during water corrosion. At the same time, oxygen and hydrogen enter the unit cell of Sm2 Fe_(17), causing a slight increase in Curie temperature. In the subsequent nitriding process,the hydroxide is dehydrated and hydrogen is desorbed. The resulting oxide reacts with Sm_2 Fe_(17)N_x to form a-Fe and Sm_2 O_3. Thermodynamic calculations using the HSC Chemistry 6.0 software indicate that the reaction can occur spontaneously. The effect of water corrosion on the magnetic properties of the nitride can be eliminated by hydrogen reduction prior to nitriding. 展开更多
关键词 Sm2Fe17 NITROGENATION reduction-diffusion method Water CORROSION Α-FE FORMATION RARE earths
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