Effect of Heat Treatment on Microstructure and Magnetic Properties of Ce-Doped NdFeB Ribbons

The substitution for Nd by abundant element cerium (Ce) is a practical way for the comprehensive utilization of rare earth resources in NdFeB permanent magnets. In this letter, we have prepared the Ce-doped NdFeB ribbons and conventional NdFeB ribbons by melt quenching method and investigated the effects of heat treatment on the crystallization behavior, microstructure, and magnetic properties of the alloy. The results show that: (1) The crystallization behavior and the microstructural changes of the (Nd,Ce)FeB magnets are similar to the conventional NdFeB magnet when heat treatment. In addition, the Ce₂Fe₁₄B phase has a significant effect on the properties of the whole magnets. (2)The NdFeB phase and CeFeB phase are relatively close to each other after being precipitated from the amorphous phase. The coupling effect between the two phases is strong enough to weaken the effect of the addition of Ce and making the properties of the NdFeB magnets to not reduce too much after adding Ce.     

退火处理对烧结Nd-Fe-B永磁体磁性能的影响

本文研究了Nd Fe B材料的低温退火处理,普通商品化生产的N35磁体在3Pa真空度、492℃条件下对普通钕铁硼退火处理1h,其矫顽力Hc和最大磁能积(BH)max值均有较大幅度的提高。     

NdFeB/酚醛树脂原位复合材料研究

采用原位聚合法制备了NdFeB/酚醛树脂(PF)母料,并进一步制备了粘结磁体.采用红外分析了NdFeB/PF母料的结构,并用多种方法对粘结磁体的磁性能和力学性能进行了研究.研究表明:在原位制备过程中,PF的聚合倾向于在NdFeB的表面进行,形成PF包覆的NdFeB,NdFeB磁粉进入了PF的生成体系,形成了海岛结构.比较三种工艺制备的磁体综合性能可知,采用NdFeB/PF母料粉料作粘结剂制备的磁体的综合性能最好.     

塑料粘结钕铁硼─铁氧体材料的复合效应研究

本文研究了ＮｄＦｅＢ－铁氧体－塑料３者复合成的永磁材料的复合效应。结果表明塑料粘结ＮｄＦｅＢ－铁氧体复合材料的＿ｂＨｃ、＿ｊＨｃ、（ＢＨ）＿ｍ随ＮｄＦｅＢ含量增加而升高，呈中间偏凹的趋势，压缩强度和硬度下降；同时随着塑料含量增加，磁性能Ｂ＿ｒ，＿ｂＨｃ，（ＢＨ）＿ｍ降低，而内禀矫顽力＿ｊＨｃ却上升。     

The properties of aluminium coating on sintered NdFeB by DC magnetron sputtering

Pure aluminium coating was deposited on sintered NdFeB magnets by direct current (DC) magnetron sputtering to improve the corrosion resistance. The corrosion behaviour of sintered NdFeB coated with aluminium was characterized by potentiodynamic polarization measurement. The adhesive strength between the aluminium coating and the sintered NdFeB was characterised by vertical tensile test and high-low temperature shock test. The influence of the coating on the magnetic properties of the sintered NdFeB was also characterised. It was found that the aluminium coating can improve the corrosion resistance of the sintered NdFeB evidently. The aluminium coating was well adhesive with the substrate and did not deteriorate the magnetic properties of the sintered NdFeB magnets. These two characters may overcome the disadvantages of NiCuNi coating which is usually electroplated on NdFeB in industry.     

High Energy and High Coercivity Sintered NdFeB Magnets by Low Oxygen Process

1. IntroductionSince NdFeB magnets were discovered[ll, theirmagnetic performance has been improved by many researchers. The maximum energy product of sinteredNdFeB magnets has been increased from 240 kJ/m'to 430 kJ/m' by Kaneko et al.[2] in 1993. The maximtun energy product commercially available todayis close to 358 kJ/m'. Because of this high performance of NdFeB products, the applications have increased enormously in the last decade. For example,hard disk drivers (HDD), magnetic reso…     

Direct-write 3D printing of NdFeB bonded magnets

We report a method to fabricate Nd–Fe–B (NdFeB) bonded magnets of complex shape via extrusion-based additive manufacturing (AM), also known as 3D-printing. We have successfully formulated a 3D-printable epoxy-based ink for direct-write AM with anisotropic MQA NdFeB magnet particles that can be deposited at room temperature. The new feedstocks contain up to 40 vol.% MQA anisotropic NdFeB magnet particles, and they are shown to remain uniformly dispersed in the thermoset matrix throughout the deposition process. Ring, bar, and horseshoe-type 3D magnet structures were printed and cured in air at 100°C without degrading the magnetic properties. This study provides a new pathway for fabricating NdFeB bonded magnets with complex geometry at low temperature, and presents new opportunities for fabricating multifunctional hybrid structures and devices.     

用人工神经网络研究合金元素对NdFeB永磁体磁性能的影响

为了系统研究合金元素对Nd-Fe-Co-Zr-B系永磁合金磁性能的影响，采用均匀设计方法设计了Nd、Co、Zr和B的4因素6水平U18（6^4）试验方案，根据试验结果，建立了合金成分与磁性能之间的人工神经网络（ANN）预测模型。利用该预测模型获得的成分-性能的二维曲线、三维曲面及等高线图，研究了单个合金元素以及多元素间的交互作用对NdFeB磁体磁性能的影响规律。结果表明：预测结果与实测结果吻合良好，预测精度高；Nd、Zr为提高矫顽力Hcj而降低剩磁Br的元素；Co、B则对提高Br有利而对提高Hcj不利；合金元素对Hcj与Br的影响呈相反的趋势；元素间交互作用对磁性能影响显著。     

不同包覆处理工艺对粘结NdFeB永磁体性能的影响

采用干混、湿混、硅烷 (KH5 5 0 )包覆处理等工艺对快淬NdFeB磁粉进行包覆处理 ,研究了包覆处理前后快淬NdFeB磁粉的抗氧化性 ,并初步研究了用包覆处理前后的快淬NdFeB磁粉制得的粘结NdFeB永磁体的力学性能及磁性能。结果表明 ,湿混及硅烷包覆处理都能提高快淬NdFeB磁粉及磁体的性能 ,而硅烷包覆处理的效果更明显     

粘结剂对注射成型钕铁硼粘结磁体性能的影响

为了制备出高性价比的注射成型粘结钕铁硼永磁材料,系统地研究了粘结剂对注射成型磁体的加工性能、磁性能和力学性能等的影响。用国产的快淬钕铁硼磁粉和尼龙6粘结剂制备出了磁性能为Br:0．5158T,Hcb：321kA／m,Hcj：730kA／m,(BH)m：40kJ／m^3的注射钕铁硼磁体。     

混杂粘结磁体研究

采用将不同性质的NdFeB磁粉和锶铁氧体磁粉混杂的方法制备粘结磁体,研究了锶铁氧体质量分数对混杂粘结NdFeB/锶铁氧体磁体的磁性能、温度稳定性等的影响规律,并建立了混杂磁体磁能积与锶铁氧体组分之间的经验关系式,实现了混杂磁体性能在一定范围内连续可调.     

放电等离子烧结NdFeB磁体的氧化和腐蚀行为

采用放电等离子烧结技术制备了新型NdFeB磁体,研究了NdFeB磁体在湿热环境下的氧化行为和在电解质溶液中的电化学特性.在扫描电子显微镜下分析了磁体的显微组织结构和成分.结果表明,与传统烧结NdFeB磁体相比,新型磁体的显微组织特征为:主相Nd2Fe14B晶粒细小、均匀,富钕相在主相晶粒边界上分布较少,主要集中在三角晶界处.这种组织结构有效抑制了磁体沿富钕相发生的晶间腐蚀的过程,使磁体具有良好的耐腐蚀性能.     

Intergrain Interaction, Coercivity and Henkel Plot for NdFeB Magnets

For both sintered and nanocomposite NdFeB magnets, deltaM(H) of the Henkel plot increases from zero, and reaches a peak, then decreases and changes to the negative values with increasing applied field. This shows that the intergrain interaction changes from the exchange-coup ling type into the magnetostatic interaction type. The magnetic field corresponding to the peak of deltaM(H) is slightly smaller than the coercivity of magnet. The peak of deltaM(H) for aligned sintered magnet is greater than that for misaligned magnet. deltaM(H) peak of the nanocomposite NdFeB magnets increases with decreasing grain sizes. It indicates that the effect of alignment field on the properties of magnet is similar to that of exchange-coupling interaction.     

粘结NdFeB磁体的制备工艺

利用NdFeB 磁粉、聚酰亚胺制备了粘结NdFeB 磁体。研究了磁粉粒度、偶联剂用量、粘结剂用量、成型压力和粘结剂性能对粘结磁体磁性能及力学性能的影响。实验结果表明,合理的粒度配比(粗∶细为33∶67) 、偶联剂用量(磁粉0. 9 %) 、粘结剂用量(磁粉3. 2 %) 、合适的压力(600 MPa) 以及以聚酰亚胺作为粘结剂,可以获得具有较好磁性能和力学性能的粘结NdFeB 磁体。      

NdFeB磁体表面化学镀Ni-Co-p合金及其耐腐蚀性能研究

采用化学镀方法制备Ni-Co-P三元合金镀层以改善NdFeB磁体的耐腐蚀性能.优化了镀液配方以及施镀工艺,研究了镀液pH值和金属离子配比([Co2 ]/[Ni2 Co2 ])对沉积速度和镀层成分的影响,测量了NdFeB基体和不同镀层在3.5%(质量分数,下同)NaCl溶液中的极化曲线.结果表明,随镀液pH值增加,沉积速度提高,镀层中Co含量升高,Ni含量和P含量逐渐降低;随镀液中Co2 比例增加,沉积速度下降,镀层中Co含量升高,Ni和P含量降低.化学镀Ni-Co-P合金后的NdFeB磁体在3.5%NaCl溶液中的腐蚀速度降低了约两个数量级;当镀液金属离子配比[Co2 ]/[Ni2 Co2 ]=0.3时,镀层耐腐蚀性能最好,且优于相同施镀条件下所得到的Ni-P镀层.     

Properties improvement and structural optimization of sintered NdFeB magnets by non-rare earth compound grain boundary diffusion

Grain boundary diffusion using rare earth (RE)-containing compounds has recently become an effective approach for improving the coercivity and reducing the heavy RE content in sintered NdFeB magnets. Here we report the enhancement of magnetic properties and corrosion resistance of NdFeB magnets by a non-RE compound diffusion process. The Dy-free sintered NdFeB magnets were coated with an MgO layer by magnetron sputtering, followed by solid diffusion heat treatment. With the successful diffusion of MgO into the magnet, the coercivity increasing from 1094 to 1170 kA/m and the maximum energy product increasing from 240 to 261 kJ/m³, together with the enhanced temperature stability and corrosion resistance, have been demonstrated. The underlying mechanisms for these enhancements have been analyzed. Microstructural investigations show that MgO entered mainly into the intergranular regions and modified the composition and structure of the grain boundary phase. The intergranular Nd–O–Fe–Mg phases observed in the MgO diffused magnet contribute to the improved performance. The current non-RE compound grain boundary diffusion process has significance in further minimizing the use of rare earth (RE).     

永磁体钕铁硼的热出气率

简要叙述了小孔流导法测量材料出气率实验原理和装置 ,给出了永磁体钕铁硼在不同情况下的热出气率 ,并对影响钕铁硼材料出气率的各种因素进行了分析 ,为使用钕铁硼永磁材料的真空系统的设计提供了依据     

Influences of Permanent Magnets Temperature Characteristic on the Levitation Force of YBaCuO Bulk Superconductors

Influences of the temperature characteristic of sintered SmCo and NdFeB permanent magnets (PM) on the levitation force of YBaCuO bulk superconductor have been investigated in this paper. It is found that for a NbFeB PM and a SmCo PM which have the same geometric parameters, a larger influence on the levitation force of a temperature decrease of the NdFeB PM has been found. The maximum change of levitation force is as high as 47.6% at a gap of 2?mm between the bottom surface of NdFeB PM and the top surface of YBaCuO bulk when the temperature of the NdFeB PM decreases from room temperature to 77?K. This work provides basic data for high temperature superconducting levitation system measurements.     

Hard magnets

Abstract

The properties and production of hard magnets are described by particular reference to NdFeB magnets. Thus, both the intrinsic properties (e.g. saturation magnetisation) and extrinsic properties (e.g. coercivity H_c) are discussed and it is shown how these properties are exploited in sintered magnets.

MST/1320     

酚醛树脂粘结钕铁硼磁体温压制备技术研究

用温压成型工艺制备了酚醛树脂粘结钕铁硼磁体,通过对磁体密度、剩磁、矫顽力、磁能积和抗弯强度的分析,研究了耦联表面处理对磁粉抗氧化性能的影响及成型工艺对磁体性能的影响.结果表明:偶联处理可以明显提高磁粉的抗氧化能力;在压力为620MPa,温压温度为180℃且不进行二次固化条件下获得了性能最佳的磁体,其密度为6.12g/cm3,抗弯强度为59.25MPa,剩磁为0.6824T,内禀矫顽力为730kA/m,最大磁能积为78.2kJ/m3.