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。     

烧结NdFeB磁体的晶粒取向和矫顽力的角度关系

本文研究了烧结ＮｄＦｅＢ磁体的晶粒取向矣矫顽力的影响和矫顽力的角度关系，结果表明：晶粒的混乱取向使矫顽力上升而不是下降，矫顽力的发动场理论比成核机制和钉扎机制与实验结果符合更好。     

晶粒取向与烧结NdFeB磁体的磁性能

研究了烧结ＮｄＦｅＢ磁体的硬磁性能与晶粒取向程度的关系，结果表明：随着晶粒取向程度的增强，磁体的剩余磁极化强度Ｊｒ单调上升、内禀矫顽力ｊＨｃ单调下降，磁感矫顽力ＢＨｃ先上升，达到一极大值后下降，从而导致了最大磁能积（ＢＨ）ｍａｘ的饱和行为。应用矫顽力的发动场理论很好地解释了这一实验现象。     

Nd－Fe－B滚镀锌工艺

Ｎｄ－Ｆｅ－Ｂ滚镀锌工艺晋西机器厂表面处理分厂（太原市０３００２７）李峰１前言钛铁硼烧结永磁体是继ＳｍＣＯ５和Ｓｍ２ＣＯ１７之后的第三代稀土永磁材料，由于钛铁硼永磁体具有高的磁化强度、矫顽力和磁能积，作为高技术领域中的磁性功能材料，具有广阔的应用前景...     

Nd—Fe—B永磁合金的微结构和晶粒相互作用

本文介绍了Ｎｄ２Ｆｅ１４Ｂ相的晶格结构及内禀磁性，概述了Ｎｄ－Ｆｅ－Ｂ永磁体的微结构和晶粒相互作用，磁体微结构包括晶粒尺寸，取向和结构缺陷，晶粒相互和可区分为长程静磁相互作用及近邻晶粒的交换耦合作用，我们分析了微结构相互作用的关系及其磁体性能的影响，最后介绍了具有发展前景的纳米交换耦合的双相复合永磁材料。     

Nd-Fe-B永磁合金的微结构和晶粒相互作用

本文介绍了Ｎｄ２Ｆｅ１４Ｂ相的晶格结构及内禀磁性，概述了Ｎｄ－Ｆｅ－Ｂ永磁体的微结构和晶粒相互作用。磁体微结构包括晶粒尺寸、取向和结构缺陷。晶粒相互作用可区分为长程静磁相互作用及近邻晶粒的交换耦合相互作用。我们分析了微结构和相互作用的关系及其对磁体性能的影响，最后介绍了具有发展前景的纳米交换耦合双相复合永磁材料。     

钕铁硼－铝镍钴粘结永磁的复合效应

本文比较系统地研究了钕铁硼－铝镍钴复合粘结永磁的复合效应，结果表明在塑料含量一定时ＮｄＦｅＢ－ＡｌＮｉＣｏ＿５复合永磁的剩余磁感应强度Ｂｒ随ＮｄＦｅＢ含量变化基本不变；剩用温度系数α＿（Ｂｒ）随ＮｄＦｅＢ含量增加而线性增大；内禀矫顽力＿ｊＨ＿ｃ，矫顽力＿ｂＨ＿ｃ，最大磁能积（ＢＨ）＿ｍ均随ＮｄＦｅＢ含量Ｘ增加呈指数函数增大，并具有下列数学关系式：＿ｊＨ＿ｃ＝１５０ｅ￣（４．１５ｘ）＋４４０，＿ｂＨ＿ｃ＝１４９ｅ￣（３．３７ｘ）＋４００，（ＢＨ）＿ｍ＝０．１７２ｅ￣（３．６１ｘ）＋０．４     

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。     

各向异性HDDR工艺Nd(Fe,Co)B粘结磁体的反磁化过程和矫顽力

研究了取向磁场对ＨＤＤＲ工艺制备的各向异性Ｎｄ（Ｆｅ,Ｃｏ）Ｂ粘结磁体顽力的影响。实验指出：阴着施加取向磁场强度的逐渐增强,磁体的制磁和矫顽力不同程度的增加。磁体的反磁化过程包括晶粒内部的成核过程和晶粒之间的畴壁位移过程,矫力应由两种反磁化过程的共同作用决定。     

Sn对烧结钕铁硼合金高温磁性能的影响及机制分析

研究了Ｓｎ对三元ＮｄＦｅＢ合金和含Ｄｙ、Ａｌ的钕铁硼合金高温磁性能的影响，发现添加Ｓｎ成分系统中，都能显著降低磁通不可逆损失，但是，Ｓｎ只对含Ｄｙ合金的矫顽力热稳定性有明显改善作用，从微磁学角度分析表明，对于三元ＮｄＦｅＢ合金，不可逆损失减小的原因是Ｓｎ改善了显微组织，从而降低了合金内部的局部退磁场。而对于含Ｄｙ的合金，掺入Ｓｎ使局部退磁减小及矫顽力热稳定性改善，两者都对磁通不可逆损失降低有贡献、     

Positron Annihilation Behaviors and Magnetic Properties of Single-phase Nd2Fe14B and Nanocomposite Nd2Fe14B／α- Fe Magnets

Positron annihilation behaviors have been studied in the single phase Nd2Fe14B magnet and the nanocomposite Nd2Fe14B/α-Fe magnet, prepared by melt spinning. The results showed that the number of vacancy-cluster at grain boundaries increases with increasing annealing temperature for the both types of magnets. The increase of this kind of defect can improve the coercivity of     

Positron Annihilation Behaviors and Magnetic Properties of Single-ph.ase Nd2Fe14B and Nanocomposite

Positron annihilation behaviors have been studied in the single phase Nd2Fe14B magnet and the nanocomposite Nd2Fe14B/α-Fe magnet, prepared by melt spinning. The results showed that the number of vacancy-cluster at grain boundaries increases with increasing annealing temperature for the both types of magnets. The increase of this kind of defect can improve the coercivity of the single-phase magnet. Conversely, the increase of vacancy-cluster amount leads to decreasing of the coercivity for the nanocomposite magnet. It implies that the mechanism of dominant magnetic hardening for the two types of magnets is different, and the domain walls pinning mechanism in the single-phase magnet and the reversal magnetization nucleation mechanism in the nanocomposite magnet operate, respectively.     

Coercivity Enhancement of Nd—Fe—B Thin Film Magnets through Dy Surface Diffusion Process

The Dy capping layer was deposited at different temperatures on the Nd-Fe-B thin films to investigate the mechanism of the coercivity enhancement through the Dy surface diffusion. The highest coercivity of 2005 kA/m (25.2 kOe) was obtained at the Dy deposition temperature of 460℃, which was significantly higher than the value of 1297 kA/m (16.3 kOe) without Dy capping layer. By performing the transmission electron microscopy (TEM) analysis, it was found that some of the grain boundaries were enriched with Nd element, which could be partly ascribed to the promotion by the Dy surface diffusion. In comparison to the evolution of the spin reorientation temperature of Nd2Fe14B phase after the deposition of the Dy capping layer, it is concluded that structural modification plays a significant role in the coercivity enhancement due to the Dy surface diffusion.     

Study on Two-phase Nanocrystalline Nd_(8.5)Fe_(74)Co_5Cu_1Nb_1Zr_3Cr_1B_(6.5)Permanent Magnet

Nd8.5Fe74Co5Cu1Nb1Zr3Cr1B6.5 bonded magnets were prepared by melt-spun and subsequent heat treatment. Magnetic properties of Br=0.68T,JHc=716 kA/m, (BH)max=77kJ/m3 were achieved. The addition of Cr element shows to be significantly advantageous in reducing grain size and increasing the intrinsic coercivity.     

Study on Two-phase Nanocrystalline Nd8.5Fe74Co5Cu1NblZr3Cr1B6.5 Permanent Magnet

Nd8.5Fe74Co5Cu1Nb1Zr3Cr1B6.5 bonded magnets were prepared by melt-spun and subsequent heat treatment. Magnetic properties of Br=0.68 T, JHc=716 Ka/m, (BH)max=77 Kj/m3 were achieved. The addition of Cr element shows to be significantly advantageous in reducing grain size and increasing the intrinsic coercivity.     

Synthesis, magnetic properties and formalism of magnetic properties of high-quality refined Nd2Fe14B powders for permanent magnet devices

Stable Nd2Fe14B powders of refined grain size of 0.1–1.0 μm were prepared using a combination of the rapid quenching (of the melt into thin ribbons), mechanical attrition and grain-surface passivation (or surface hardening) and coating by a thermally rigid, adhesive and corrosion-proof material in air. The ribbons (of 15–30 μm thickness) were cut, crushed and milled under H2 gas at approximately 1 bar and room temperature to give hydrided Nd2Fe14BHx, x≲5, flakes of 1–5 μm sizes, which are brittle and easily obtained in powder form by high-energy ball milling. The interstitial H atoms in the hydride sample were desorbed by slowly heating (5°C min-1) the sample between 25 and 600°C in N2 gas (which helps the desorption of the H atoms without decomposition of the sample) in a reactor and then pumping off the total gas at 600°C. The H-desorbed specimen, when annealed at 600–800°C under a dynamic vacuum, results in a refined powder, showing a characteristically high remanence, Jr of 9–12 kG, together with a high intrinsic coercivity, Hci, of 10–28.3 kOe, depending on the size and surface structure of the grains. This powder is highly pyrophoric and catches fire in open air but can be stabilized by passivating and coating the grain surfaces with a mixture of carbon, AIN and Nd2O3 by milling the mixture in a suitable organic liquid (to allow the additives to adhere the sample without excess oxidation) followed by annealing at an elevated temperature in N2 gas at approximately 1 bar. In this process, the separated Nd2Fe14B grains acquire a thin nitride–carbide (probably amorphous) stabilized surface passivation layer which prevents further oxidation of the sample in air at room temperature. The passivation layer, in combination with a thin film of the Nd-rich intergranular phases, if any, peculiarly appears to be non-magnetic compared with the main ferromagnetic Nd2Fe14B phase. It keeps the ferromagnetic Nd2Fe14B grains separated and thus inhibits mixing between the local magnetic lines of forces confined to them. As a result, they behave like ideal single-domain particles and therefore exhibit a reasonably improved Hci value, without a significant decrease in the high Jr or the high saturation magnetization Ms which are useful for the high-energy-density magnets and related devices and components. The results are modelled and discussed with microstructures, magnetic properties, thermal stability and loss, if any, in the mass of the specimens during exposure to ambient atmosphere. This revised version was published online in November 2006 with corrections to the Cover Date.     

Metallographic study on Nd-Fe-Co-B sintered magnets

Metallographic study has been carried out on the Nd-Fe-Co-B alloys to clarify the change in coercivity with the Co composition substituted for Fe in the Nd2Fe14B type sintered magnets. The decrease in coercivity caused by the Co substitution is attributed to the formation of soft-magnetic phases such as Nd(Fe, Co)2and Nd(Fe, Co)3. The mole ratio of Nd to (Fe+Co) of these soft-magnetic phases decreases with increasing the Co substitution. The Co concentration is much higher in these soft-magnetic phases than in Nd2(Fe, Co)14B matrix. The A1 addition in Nd-Fe-Co-B magnet makes the Nd(Fe, Co)2compound unstable to form the non-magnetic Nd3(Fe, Co, Al) compound, resulting in the increase in the coercivity of Nd-Fe-Co-B magnet.     

变形量对热压/热变形纳米复合Nd_9Fe_（84.5）Co_1B_（5.5）永磁体晶粒尺寸和矫顽力的影响

采用热压/热变形工艺制备纳米复合Nd9Fe84.5Co1B5.5永磁体,研究了热变形过程中的变形量对磁体平均晶粒尺寸的影响以及由此带来的晶间相互作用和矫顽力的变化。结果表明变形量54%的磁体中的硬、软磁性相的平均晶粒尺寸分别为61.0和51.8nm,与其热压状态时的两相平均晶粒尺寸（52.1和54.0nm）接近;而变形量74%的磁体中的硬、软磁性相的平均晶粒尺寸则分别显著减小至19.2和22.4nm。随着两相晶粒尺寸的显著细化,磁体中的晶间相互作用由以静磁耦合作用为主转变为以晶间交换耦合作用为主,这导致其矫顽力提高了64%。     

Structure and Magnetic Properties of Nd-Fe-B/a-Fe Nanocomposite Magnets by Co, Nb, Dy Substitutions

Structure and magnetic properties of the nanocomposite magnets prepared by mechanical alloying procedure with composition 55 wt pct Nd (Fe0.92B0.08)5.5+45 wt pct a-Fe, 55 wt pct Nd(Fe0.8-xCo0.12Nbx B0.08)5.5+45 wt pct a-Fe (x=0.00, 0.01, 0.03) and 55 wt pct (Nd0.9Dy0.1) (Fe0.77Co0.12Nb0.03B0.08)5.5+45 wt pct a-Fe were studied. It was found that substitution of Co for Fe could significantly improve the permanent magnetic properties of the nanocomposite magnets and typically, the maximum magnetic energy product was increased from 104.8 kJ/m3 (13.1 MGOe) to 141.6 kJ/m3 (17.7 MGOe). In contrast to the case of conventional nominally single-phase magnets, the addition of Nb results in promoting the growth of a-Fe grain and is thus unfavorable for the improvement of permanent magnetic properties of the nanocomposites. Although the addition of Dy can increase the coercivity of the magnets, the increase of magnetic anisotropy of hard phase leads to decrease of the critical grain size of soft phase. Additionally it causes the difficulty of preparing the nanocomposites because it is more difficult to control the grain size of soft phase to meet the requirement of appropriate exchange coupling between hard and soft grains.     

Tuning magnetic properties,thermal stability and microstructure of NdFeB magnets with diffusing Pr-Zn films

Grain boundary diffusion process(GBDP) serves as a promising approach in improving magnetic properties and thermal stability of Nd FeB permanent magnets. Herein, non-heavy rare earth Pr-Zn films deposited on the magnet surface using DC-magnetron sputtering system are reported. The thermal stability and coercivity enhancement mechanism of Pr-Zn GBDP magnets were investigated. Results show that the coercivity of Pr-Zn GBDP magnet increases from 963.96 kA m~(-1) to 1317.14 kA m~(-1) without any remanence reduction. Notably, the demagnetization curve of Pr-Zn GBDP magnet still remains a high squareness ratio. The temperature coefficient of coercivity and anti-demagnetization ability of Pr-Zn GBDP magnet under high temperatures are improved after GBDP treatment. The well-optimized rare earth-rich(RE-rich) grain boundary phases and high effective anisotropy field of(Nd,RE)2 Fe14 B magnetic hardening layers surrounding main grains are the key factors to impact the magnetic properties and thermal stability of Nd FeB permanent magnets via GBDP treatment.