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Efficient Nanostructuring of Isotropic Gas-Atomized MnAl Powder by Rapid Milling(30s)

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Engineering 2020年第2期6卷 173-177页

作者： J.Rial E.M.Palmero A.Bollero division of permanent magnets and applications IMDEA NanoscienceCampus Universidad Autonoma de MadridMadrid 28049Spain

An unprecedentedly short milling time of 30 s was applied to gas-atomized MnAl powder in order to develop permanent magnet properties and,in particular,*** is shown that such a short processing time followed by annealing results in efficient nanostructuring and controlled phase *** defects resulting from the microstrain induced during milling,together with the creation of the bphase during post-annealing,act as pinning centers resulting in an enhanced *** study shows the importance of finding a balance between the formation of the ferromagnetic s-MnAl phase and the bphase in order to establish a compromise between magnetization and coercivity.A coercivity as high as 4.2 kOe(1 Oe=79.6 A·m^-1)was obtained after milling(30 s)and annealing,which is comparable to values previously reported in the literature for milling times exceeding 20 *** reduction of the postannealing temperature by 75℃ for the as-milled powder and a 2.5-fold increase in coercivity,while maintaining practically unchanged the remanence of the annealed gas-atomized material,opens a new path for the synthesis of isotropic MnAl-based powder.

关键词： permanent magnets(PMs) Nanostructuring Phase transformation MnAl Gas atomization Ball milling

Correlation of mechanical anisotropy with fine grain strengthening for Sm_(2)Co_(17)-type sintered permanent magnets

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Journal of Rare Earths 2022年第10期40卷 1584-1591页

作者： Lei Wang Chao Wang Qiangfeng Li Youhao Liu Yikun Fang Xiaofei Yi Wei Li division of Functional Materials Research Central Iron and Steel Research InstituteBejing 100081China State Key Laboratory of Rare Earth permanent Magnetic Materials Hefei 231500China

The as-solution-treated Sm_(2)Co_(17)-type magnets exhibiting a single 1:7 H phase with different average grain sizes(D) were *** of bending strength(R_(bb))and compressive strength(R_(mc)) of the magnets were ***,the R_(bb) increases from 86 to 173 MPa with D decreasing from~52 to~18 μm for group c//h *** 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 *** 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 *** 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.

关键词： Sm_(2)Co_(17)-type permanent magnets Grain refinement Bending strength Compressive strength Anisotropy Rare earths

Improvement of coercivity and thermal stability of Nd-Fe-B sintered magnets by intergranular addition of Tb80Fe20 alloy

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Journal of Rare Earths 2022年第12期40卷 1899-1904,I0003页

作者： Ze Duan Haicheng Xuan Jincai Su Jingwu Chen Xiaofei Yi Youhao Liu Peide Han College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan 030024China State Key Laboratory of Rare Earth permanent Magnet Materials Hefei 231500China

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 *** micro structure,magnetic properties and thermal stability of the Nd-Fe-B magnets with different Tb_(80)Fe_(20)contents were *** 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)***,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℃,*** Curie temperature(TC)of the Nd-Fe-B magnet is slightly enhanced with the increase of Tb_(80)Fe_(20)***,the irreversible flux magnetic loss(hirr)is obviously reduced as Tb80Fe20addition *** analysis of the microstructure reveals that a modified microstructure,*** and continuous RE-rich grain boundary layer,is acquired in the sintered magnets by introducing Tb_(80)Fe_(20)*** associated mechanisms on improved coercivity and thermal stability were comprehensively researched.

关键词： Tb80Fe20 alloy Coercivity Nd-Fe-B sintered magnet Thermal stability Rare earths

Electromagnetic design and performance of conduction cooled superconducting magnet for spoke resonator cryomodule for Proton Improvement Plan(PIP)-II

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Superconductivity 2024年第3期11卷 14-33页

作者： Kumud Singh Janvin Itteera Mahima Vikas Tiwari Himanshu Bisht Sanjay Malhotra R.R.Singh Rajesh Jalan Sanjay Howa Rajesh Chimurkar Sunil Kumar S.Stoynev M.Turenne M.Yu B.Hanna J.Hayman C.Boffo Electromagnetic applications&Instrumentation division Bhabha Atomic Research CentreTrombay 400085India Fermi Accelerator National Laboratory Batavia IL 60510-5011USA

The Proton Improvement Plan(PIP)-II project is part of Fermilab’s upgrade of its proton accelerator complex,to provide a powerful,high-intensity proton beam to the laboratory’s upcoming research *** project includes an 800 MeV superconducting(SC)linear accelerator(linac),with five flavours of cavities and *** medium energy section of the linac contains two types of superconducting Single Spoke Resonator(SSR)RF cavities(SSR1 and SSR2),which are interleaved with strong solenoid focusing lenses.A unified design of the solenoid has been developed,with one solenoid design satisfying both SSR1 and SSR2 *** integral focusing strength requirement of 4.5 T^(2)m with a full width half maximum(FWHM)of 180 mm indicates the peak field strength∼6.8 T in the magnet aperture,necessitating a superconducting design within the limits of NbTi as magnet wire *** are complex combined units that include one focusing solenoid with bucking coils to minimize fringe fields and four corrector coils each,with independent current leads to produce dipole and quadrupole *** simplify the current lead design and reduce complexity,the project opted conduction cooling for these magnets,thus requiring a redesign compared to previous prototype bath cooled *** designs for high energy accelerators adopt bath cooled design of the solenoid focusing lenses for medium energy *** present design explores a unique and technically superior solution for the cryomodule operation by decoupling the magnet and cavity cooling to certain *** in cryomodule operations shall be studied after integration of magnets in the Linac *** we discuss the design requirements,challenges,electromagnetic design,superconducting wire selection and the results from magnetic measurements of the first pre-series units.

关键词： conduction module magnets

A novel strategy for the fabrication of highperformance nanostructured Ce-Fe-B magnetic materials via electron-beam exposure

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Science China Materials 2021年第10期64卷 2519-2529页

作者： Liang Zha Cholsong Kim Chao Yun Dong Zhou Wei Li Xiangdong Kong Li Han Wenyun Yang Shunquan Liu Jingzhi Han Changsheng Wang Honglin Du Weixing Xia Alberto Bollero Jinbo Yang State Key Laboratory for Mesoscopic Physics School of PhysicsPeking UniversityBeijing 100871China Functional Materials Research Institute Central Iron&Steel Research InstituteBeijing 100081China Department of Micro-Nano Fabrication Technology Institute of Electrical EngineeringChinese Academy of SciencesBeijing 100190China Key Laboratory of Magnetic Materials and Devices Ningbo Institute of Material Technology and EngineeringChinese Academy of SciencesNingbo 315201China division of permanent magnets and applications IMDEA NanoscienceMadridSpain Collaborative Innovation Center of Quantum Matter Beijing 100871China Beijing Key Laboratory for Magnetoelectric Materials and Devices Beijing 100871China

Ce_(2)Fe_(14)B compound has a great potential to serve as a novel permanent magnet alternative thanks to the abundant and inexpensive rare-earth element(cerium),while its low magnetocrystalline anisotropy and energy product severely restrict its *** this work,a novel strategy combining melt-spinning and electron-beam exposure(EBE)aiming for fabricating high-performance Ce-Fe-B magnetic materials is reported to solve the above-mentioned ***,this strategy facilitates developing a suitable grain boundary configuration without using any additional heavy rare-earth *** the optimal EBE condition,the maximum energy product((BH)max)of pure Ce-Fe-B alloy is 6.5 MGOe,about four times higher than that obtained after conventional rapid thermal processing method for the same *** enhanced intergranular magnetostatic coupling effect in the EBE sample is validated by mapping the first-order-reversal-curve(FORC)*** in-situ observation of magnetic domain wall motion for Ce-Fe-B alloy using Lorentz transmission electron microscopy reveals that the boundary layers are very effective in pinning the motion of domain walls,leading to the increased coercivity under EBE,and this pinning effect is further verified by micromagnetic *** results suggest that Ce Fe B materials using EBE could be a promising candidate after further processing,which could fill the performance“gap”between hexaferrite and Nd-Fe-B-based magnets.

关键词： nanoscale magnets rapid thermal annealing Ce-Fe-B magnetic properties nanocrystalline material

Thermal Stability of Low Cost Nd-Fe-B magnets

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Journal of Materials Science & Technology 1992年第1期8卷 70-72页

作者：连法增任建军艾禄张效时赵恒和 Northeast University of Technology Shenyang 110006China Shenyang permanent Magnetic Materials Factory Shenyang110015China

*** the Nd-Fe-B magnets appearedin 1983,researchers,producers and users ofthe permanent magnetic materials have paidgreat attention to *** the mag-nets have low Curie temperature Tc andbad thermal stability as well as easeoxidation,their applications are limited insome *** researchers are greatly in-terested in increase energy product

关键词： low cost impure Nd-Fe-B magnets thermal stability

Thickness-dependent coercivity mechanism and hysteresis loops in hard/soft magnets

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Rare Metals 2020年第1期39卷 22-27页

作者： Xiao-Jiao Weng Guo-Ping Zhao Hong Tang Lai-Chuan Shen Yao Xiao College of Physics and Electronic Engineering Sichuan Normal UniversityChengdu610101China Collaborative Innovation Center for Shanxi Advanced permanent Materials and Technology Linfen041004China State Key Laboratory of Metastable Materials Science and Technology Yanshan UniversityQinhuangdao066004China

Two models are established to reveal the underlying coercivity mechanism for SmCo/Fe films,where one model considers a transition layer between hard and soft layers,while the other model does not consider this *** on the two models,hysteresis loops,nucleation fields and coercivity are obtained by one-dimensional(1 D)and three-dimensional(3 D)micromagnetic *** particular,the calculated nucleation fields(H_N)and coercivity(H_C)match very well with the experimental *** is found that the increase in the soft phase thickness(Ls)leads to a transition of the coercivity mechanism from nucleation to *** a pinning is inherently related to nucleation and has both attributes of traditional nucleation and pinning,called as a hybrid coercivity mechanism *** is general for all hard/soft composites and can be extended to single-phased permanent magnets where defects are inevitable.

关键词： Coercivity mechanism Nucleation Pinning Hysteresis loops

Anisotropic corrosion behavior of sintered(Ce_(0.15)Nd_(0.85))_(30)Fe_(bal)B permanent magnets

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Journal of Rare Earths 2019年第3期37卷 287-291页

作者： Xiaoning Shi Minggang Zhu Dong Zhou Zheng Jing Meiling Zhang Wei Li division of Functional Material Central Iron & Steel Research Institute

In this work, the corrosion behavior of the surface parallel to the oriented c-axis(c‖) and perpendicular to c-axis(c⊥)in the(Ce_(0.15)Nd_(0.85))_(30)Fe_(bal)B dual main phase magnet was studied. With the addition of Ce,the volume fraction of RE-rich phase shown in the backscattered electron(BSE) images is basically approximate on the two surfaces. The free corrosion potential(E_(corr)) of the c‖ surface is more negative,which shows the worse corrosion resistance from the perspective of thermodynamics. While the reaction kinetics parameters with the smaller free corrosion current(i_(corr)) and the larger transfer resistance(R_(ct)) react the opposite conclusion in 3.5 wt% NaCl solution. Moreover, the c‖ surface performs smaller ions concentration of corrosion product and less damaged corrosion morphology compared to c⊥ surface after the free corrosion. The inconformity is not affected by the RE-rich phase, but by the anisotropy of the grains that the c‖ surface has larger density of the atoms and the lower ratio of(Nd, Ce)/Fe.

关键词： Sintered Nd-Fe-B Ce Dual main phase Anisotropic Electrochemistry Corrosion

Oxide evolution in NdDy-Fe-B magnet during aging process

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Journal of Rare Earths 2012年第10期30卷 1020-1023页

作者：王景代冯海波李安华李岩峰朱明刚李卫 division of Functional Materials Central Iron and Steel Research Institute

Sintered NdDy-Fe-B magnets were made from strip cast flakes by powder metallurgy method. For the magnet with 6 wt.% Dy substituted Nd, a remarkable coercivity increase of 70% was obtained after aging at 900 ℃ for 2 h and a high coercivity of 23.5 kOe was achieved after aging at 520 ℃ for 2 h. The average diameter of the oxide particles decreased during the following 900℃ aging treatment. Dy and O diffusion from oxide particles to Nd-rich phase during the aging process was observed. The oxide evolution and Dy element diffusion were helpful to the coercivity enhancement.

关键词： permanent magnet aging dysprosium oxide coercivity rare earths