Energy calculation of a permanent magnet system by surface and fluxintegrals (the flux-mmf method)

Formulas are derived for the total magnetic energy of a system with no currents, linear soft magnetic materials, and linear permanent magnets that satisfy a zero curl condition involving their magnetization vector (zero equivalent volume current density). This class of magnets includes common parallel and radially magnetized NdFeB and ferrite magnets above the knee in their demagnetization curves. The formulas express the energy as a constant plus either an integral over the magnet surface of the magnetic vector potential or an integral through the magnet of the magnetic flux. The formulas provide theoretical foundation for the flux-magnetomotive force (mmf) method for calculating cogging torque of permanent magnet motors     

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.     

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     

Permanent magnet applications

The main uses of permanent magnets are covered either by the range of cast and magnetically treated alnico alloys or by the several grades of sintered barium/strontium hexaferrite, but minority materials have their special applications and continue to develop. Three different technical classes of permanent magnet applications can be distinguished. Firstly, magnets working in a magnetic circuit of static reluctance, e.g., speakers, moving-coil measuring instruments, microwave devices, separators, etc. Secondly, those working in a varying self-demagnetizing field due to change of circuit reluctance, such as clamping and holding magnets which range from planning-board indicators to large chucks for machine-tools. Thirdly, magnets which work in both a self-demagnetizing field and a varying externally produced field, as in motors, generators, the several types of magnetic couplings, and magnetic suspensions. For each of these three classes the basic design principles are indicated and typical applications are described. Additionally, there are uses for high-hysteresis permanent magnet materials without premagnetization, as in hysteresis motors.     

1991 12th International Conference on Magnet Technology

The following topics are dealt with: accelerator magnets; fusion magnets; superconducting motors and generators; MHD (magnetohydrodynamic) magnets; high magnetic fields, wigglers, undulators, and test facilities; NMR (nuclear magnetic resonance) magnets; magnetic separation; instrumentation and measurements; stability and AC losses; materials; computations; cryogenic systems and components; and magnets and conduit conductors     

粘结剂对粘结钕铁硼/锶铁氧体复合磁体磁性能的影响

为获得磁性能适中的磁体,采用流动温压成型技术制备了各向同性粘结Nd Fe B/锶铁氧体复合磁体.利用振动样品磁强计(VSM)研究了不同粘结剂对粘结Nd Fe B/锶铁氧体复合磁体磁性能的影响.研究表明:环氧值适中的酚醛环氧树脂制备的磁体具有较好的磁性能;当采用环氧值为0.480 mol/100 g酚醛环氧树脂BPANE8200H做粘结剂时,粘结Nd Fe B/锶铁氧体复合磁体获得了最佳的磁性能:Br=0.55 T,Hcj=620.6 k A/m,(BH)max=45.6 k J/m3.在保证磁体磁性能的前提下兼顾力学性能,粘结磁体流动温压成型温度参数的设置必须考虑粘结剂的软化点温度.     

Tunable,Flexible Composite Magnets for Marine Monitoring Applications

This paper presents flexible NdFeB‐PDMS composite magnets with tunable magnetic and mechanical properties optimized for applications in corrosive marine environments. The magnetic and mechanical properties are studied for different NdFeB powder concentrations and the performance of the magnetic composites for different exposure times to sea water investigated systematically. The remanence and saturation magnetizations could be tailored by the powder concentration, whereby up to 70 wt% concentration could be employed without compromising the integrity of the magnets. The elastic modulus of the composite magnets is about 10⁵ times lower than the one of a bulk permanent magnet. This ensures a high bending flexibility, which allows the magnets to be attached to curved surfaces as illustrated for a giant clam, crab, and turtle. At the same time, the weight of the composite magnets is reduced by a factor of about 10, which poses less burden to animals’ natural free movement. Without a protective layer, the composite magnets lose more than 50% of their magnetization after 51 days in seawater. However, the durability of the composite magnets has been improved considerably by using polymer coatings. Parylene C is the most effective for this, providing corrosion resistance, flexibility, and enhanced biocompatibility. Parylene C films of 2 and 4 μm thicknesses provided excellent protection of the magnetic composite in corrosive aqueous environments for 65 and 82 days, respectively. By combining the composite magnets with tunnel magnetoresistance sensors, a magnetic animal monitoring system is established that is used to track the behavior of giant clam, crab, and turtle.

     

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/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.     

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.     

1995～1996年磁性功能材料进展

综述了１９９５～１９９６年间几种磁性功能材料的新进展。这些材料包括高磁矩Ｆｅ－Ｎ化合物，高最大磁能积ＮｄＦｅＢ永磁材料，庞磁电阻材料，Ｍｎ－Ｚｎ铁氧体大功率材料，新的Ｉｎｖａｒ磁性材料和铁电反铁磁材料     

W对烧结NdFeB磁体的显微组织和磁性能的影响

主要研究了在烧结ＮｄＦｅＢ磁体的晶界添加Ｗ对显微组织和磁性能的影响，实验结果表明，随Ｗ添加量的增大，晶粒逐渐细化，剩磁稍有下降，面矫顽力逐渐升高，在含Ｗ为１％ｗｔ时，矫顽力达到峰值。扫描电镜的观察显示，加Ｗ磁体在晶界区生成许多杆状相，能谱和Ｘ线射线衍射分析均表明此相为ＷＦｅＢ化合物。     

HDDR各向异性NdFeB温压混炼过程

研究了在HDDR各向异性NdFeB粘结磁体温压成形过程中粘结剂和润滑剂的添加量以及二者同磁粉的混炼工艺对磁体磁性能及机械强度的影响。利用B－H回线仪和扫描电子显微镜对磁体的磁特性和显微组织结构进行了分析测试，同时测试了不同工艺条件下处理的磁体的机械强度。结果表明，粘结剂的适量添加能够保证磁体同时具有较好的磁性能和机械强度。润滑剂的加入既降低了磁粉之间的摩擦力，又减小了磁粉在压制过程中的损伤度，从而使粘结磁体获得良好的磁粉填充率、磁取向度和磁性能。而粘结剂和润滑剂与磁粉之间的混炼方式决定了磁体中粘结剂的结合效果，从而决定了磁体最终的机械强度。采用合理的混炼工艺，可以使粘结磁体同时获得最佳的磁性能和机械强度。     

Anisotropic NdFeB Magnet Fabricated by Single Stroke Hot Deformation

1. IntroductionHard magnetic properties of the materials, such ascoercivity (He), remanence (B,), and energy product[(BH)...] depend strongly on the composition andthe processing conditionslll. The optimally quenchedmelt-spun ribbons of NdFeB alloys produced by rapidqllenching process have equiaxed and randomly oriellted NdZFe14B grains. In order to obtain anisotropicNdFeB grains, the general method is followed by hotpressing and die-upsetting of the ribbon powder oneafter anotherll'2]. …     

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。     

NdFeB纳米晶双相复合永磁材料研究进展

NdFeB纳米晶双相复合永磁材料，由于其潜在的优异磁性能和商业价值，成为当今材料领域研究的热点。本文就近年来NdFeB纳米晶双相复合永磁材料的发展状况，从该类合金的交换耦合作用、分类以及提高磁性能的方法三个方面为重点，作简要的评述。     

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.     

A study of Nd2Fe14B and a neodymium-rich phase in sintered NdFeB magnets

The microstructure and properties of NdFeB sintered permanent magnets were analysed by different methods. Samples analysed were sintered and thermally treated. The hard magnetic Nd₂Fe₁₄B phase and amorphous neodymium-rich phase were observed by TEM. The neodymium-rich phase contained iron and boron, in elemental and in B₂O₃ form, which is known as a glass former. At the sintering temperature, Nd₂Fe₁₄B and the neodymium-rich phase are supersaturated with iron, which should be dissolved at the annealing temperature to react with neodymium and boron and form additional Nd₂Fe₁₄B phase. Iron precipitates of size up to 2 nm were detected in the Nd₂Fe₁₄B phase. These superparamagnetic precipitates of -Fe could affect the hard magnetic properties of NdFeB magnets.     

MAGNEQUENCH ND-FE-B MAGNETS

The advent of MAGNEQUENCH neodymium-iron-boron materials having excellent magnetic properties and potential economic advantages has initiated a new era in permanent magnet technology. These magnets have already been used in cranking motors, stepping motors, etc.

Different kinds of isotropic powders have been developed having high and low coercivities for use in varied applications. The properties of these powders are discussed. The properties of fully dense isotropic (MQ2) and anisotropic magnets (MQ3) are given. Anisotropic powders produced from hot deformed magnets are stable and it contrasts sharply with those prepared from sintered magnets. These anisotropic powders can be molded into bonded magnets with energy products of 15-17 MGOe.