深冷处理对纳米复合永磁材料织构度和磁性能的影响

利用熔体快淬技术制备了(N d11.4F e82.9B5.7)0.99Z r1,(N d11.4F e82.9B5.7)0.99G a1和P r8F e87B5快淬带。利用深冷技术对纳米晶复合快淬带进行超低温处理。研究了深冷处理对纳米复合永磁材料织构度和磁性能的影响。结果表明深冷处理有助于快淬带织构度的增强,使快淬样品的饱和磁化强度Ms发生变化,矫顽力Hci变化不大。经深冷处理后P r8F e87B5样品最佳(BH)m ax达到187.9kJ.m-3。     

Preparation and Magnetic Properties of Melt-Spinning Nd2Fe14B/α-Fe Nanocomposite Magnets

Nd11Fe71Co8V1.5Cr1B7.5 magnet was prepared by melt-spinning and subsequently annealed. The effects of the wheel speed on the magnetic properties and microstructure were studied. The results reveal that fine nanocomposite microstructure consisting of Nd2Fe14B and α-Fe phases can be developed at an optimum wheel speed of about 21 m·s-1. After optimal annealing (640 ℃×4 min), magnetic properties of Br=0.64 T, jHc=903.5 kA·m-1 and (BH)max=71 kJ·m-3 were obtained for the bonded magnets. The addition of Cr element significantly reduces grain size, increasing the intrinsic coercivity and maximum magnetic energy product.     

Effect of Zirconium Content on Microstructure and Magnetic Properties of Nanocomposite Bonded Magnets

Five kinds of bonded magnets with compositions of Nd10.5Fe78.4-xCo5ZrxB6.1(atom percentage x＝0,1.0,1.5,2.0,2.5)were prepared by rapid quenching, post heat treatment and mould-pressing.The microstructure and crystallization behavior were studied by X-ray diffraction (XRD), differential thermal analysis (DTA) and atomic force microscopy (AFM). The results suggest that high content of Zr can increase the glass formation ability (GFA) of alloys. When the content of Zr is controlled at a certain level, Fe2Zr with high melting point is formed in the alloys, and grain size is reduced consequently. At the same time, because of Zr addition, the coercivity and squareness of demagnetization loop are obviously improved, and the energy product is accordingly increased. As a result, optimal magnetic properties of Nd10.5Fe78.4-xCo5ZrxB6.1(Br＝0.659 T,Hcj＝628 kA·m-1,Hcb＝419 kA·m-1,(BH)m=73 kJ·m-3) are obtained when x=2.     

Investigation of Abnormal Grain Growth in Sintered Nd-Fe-B Permanent Magnet

The abnormal growth of grains of sintering Nd13.6 Dy0.4 Fe79.5 B6.5 magnets were investigated in low oxygen manufacturing process.The abnormal growth of grains occurs easily when the sintering temperature is higher than 1080℃ during the manufacture process.In the magnets, the oxygen content is less than 700 × 10-6 and the average particle size of powder is smaller than 4 μm.The squareness of demagnetization curve of magnet is deteriorated.For high performance magnets, the abnormal growth grain should be avoided by selecting a suitable sintering temperature.     

Effect of Gallium Addition on Magnetic Properties of Nd2Fe14B-Based/α-Fe Nanocomposite Magnets

The influence of Ga addition on the crystallization behavior and the magnetic properties of nanocomposite Nd2Fe14B-based/α-Fe magnets was investigated. It was found that the addition of 0.2% did not change the crystallization temperature of amorphous alloy, but the magnetic properties were improved significantly because of the strong exchange coupling interaction between the hard and soft magnetic phases. The optimum magnetic properties with iHc=600.3 kA·m-1, Br＝0.75 T, and (BH)max=88.03 kJ·m-3 were obtained in bonded Nd9.5(FeCoZr)83.8Ga0.2B6.5 magnet with 15 m·s-1 wheel speed and 670 ℃ annealing treatment. The apparent improvement of magnetic properties originates from the grain refinement calculated using the Scherrer formula from corresponding XRD patterns and the excellent rectangularity of the demagnetization curve.     

Effect of Gallium Addition on Magnetic Properties of Nd2Fe14B-Based/ α-Fe Nanocomposite Magnets

The influence of Ga addition on the crystallization behavior and the magnetic properties of nanocomposite Nd2Fe14B-based/α-Fe magnets was investigated. It was found that the addition of 0.2% did not change the crystallization temperature of amorphous alloy, but the magnetic properties were improved significantly because of the strong exchange coupling interaction between the hard and soft magnetic phases. The optimum magnetic properties with iHc = 600. 3 kA· m^-1, B r = 0.75 T, and （BH）max = 88.03 kJ· m^-3 were obtained in bonded Nd9.5（FeCoZr）83.8 Ga0.3 B6.5 magnet with 15 m·s^- 1 wheel speed and 670 ℃ annealing treatment. The apparent improvement of magnetic properties originates from the grain refinement calculated using the Scherrer formula from corresponding XRD patterns and the excellent rectangularity of the demagnetization curve.     

Study on Key Techniques for Producing High Performance NdFeB Sintered Permanent Magnets

ＮｄＦｅＢｍａｇｎｅｔｓｈａｖｅｂｅｅｎｉｍｐｒｏｖｅｄｄｒａ ｍａｔｉｃａｌｌｙｓｉｎｃｅｉｔｗａｓｉｎｖｅｎｔｅｄｉｎ 1 983 .Ｔｗｏｔｙｐｅｓｏｆｓｉｎｔｅｒｅｄｍａｇｎｅｔｓ ,ｈｉｇｈｅｎｅｒｇｙｐｒｏｄ ｕｃｔｓ ((ＢＨ ) ｍａｘ)ａｎｄｄｏｕｂｌｅｈｉｇｈ (ｈｉｇｈ(ＢＨ ) ｍａｘａｎｄｈｉｇｈｃｏｅｒｃｉｖｉｔｙ (ｉＨｃ) )ａｒｅｔｈｅｔｗｏｔｅｎｄｅｎｃｉｅｓｆｏｒＮｄＦｅＢｓｉｎｔｅｒｅｄｍａｇｎｅｔｓ .Ｂｏｔｈｆａｃｔｏｒｉｅｓａｎｄｒｅｓｅａｒｃｈｉｎｓｔｉｔｕｔｅｓａｒｅｆｏｃｕｓ…     

Effect of super heat treatment on crystallization behavior and magnetic properties of Nd4.5Fe77B18.5 nanocomposites

Melt-spun Nd4.5Fe77B18.5 ribbons were prepared under various superheat temperatures.The microstructure characteristics,crystallization behavior,and subsequent magnetic properties of Fe3B/Nd2Fe14B nanocomposite magnets were investigated using X-ray diffraction,differential thermal analysis,and vibrating sample magnetometry.It was shown that melt spinning at different quenching temperatures caused the as-quenched ribbons to have distinctive crystallization behavior.Depending on superheat temperature,phase tra...     

NdFeB稀土永磁材料研究进展

本文综述了NdFeB稀土永磁材料的研究进展,主要包括结构、矫顽力机制、添加元素、磁性能、腐蚀行为及其防护等方面,并就国内NdFeB产业的发展进行了讨论。     

Effect of melt superheating treatment on crystallization behavior and magnetic properties of melt-spun Fe-rich Nd-Fe-B ribbons

Melt-spun Nd7Fe90B3 ribbons were prepared under different melt treatment conditions,i.e.,the melt temperature was varied prior to ejection onto the quenching wheel.The microstructure characteristics,crystallization behavior,and subsequent magnetic properties of α-Fe/Nd2Fe14B-based exchange-spring magnets were investigated using X-ray diffraction,differential scanning calorimeter,transmission electron microscopy,and vibrating sample magnetometer.It was shown that melt spinning at different quenching temperat...     

Investigation on Hard Magnetic Properties of Nanocomposite Permanent Magnets with Precipitate-Typed Microstructure by Micromagnetic Finite-Element Methods

Maximumenergyproduct (BH) maxisakeychar acteristicofapermanentmagnet (PM ) .Theoptimal(BH) maxislimitedbythevalueofJr2 / 4 μ0 (Jrrema nence)correspondingtoanidealrectangularhysteresisloopwhencoercivityμ0 HcisatleastlargerthanJr/ 2 .FormostrareearthPM ,thecoercivityisfarlargerthantheremanence[1,2 ] .Thus ,remanenceenhance mentbecomesanimportantroleindeveloping(BH) max.Sincehighremanencewasfoundinisotrop icnanostructuredPM ,muchefforthasbeenpaidtoachievehighperformancePM[3,4 ] .Thehigh…     

Texture of Nanocomposite Nd2Fe14B/α-Fe Melt Spun Ribbons

Highly textured nanocomposite Nd9Fe84.5Nb0.5B6 ribbons were obtained by rapid solidification at wheel speeds from 15 to 20 m·s-1.X-ray diffraction(XRD)shows that these ribbons are preferentially orientated with the c axis of Nd2Fe14B phase perpendicular to the surface of the ribbons.The texture of Nd2Fe14B phase on the free surface is stronger than that on the contact surface and decreases with increase of wheel speed.The texture of Nd2Fe14B phase seems to be caused by the preferential growth of the crystal nuclei favorable orientation with their c-axes along the temperature gradient during rapid solidification,which can be explained by a growth circular cone(GCC).The intensity of the anisotropy can be expressed by the magnitude of the cone generating angle.The supercooling velocity and wheel speed will influence the cone generating angle,which in turn influences the anisotropy.The remanence and maximum energy product in the direction perpendicular to the ribbon surface is much higher than that in the direction parallel with the ribbon surface.High remanence and maximum energy product can be obtained in the direction perpendicular to the ribbon surface.The texture of Nd2Fe14B phase decreases gradually after annealing above 600 ℃,which is mainly attributed to the precipitation of new α-Fe from Nd2Fe14B phase with super-saturated Fe.Decreasing the annealing temperature or reducing the annealing time is beneficial for preserving the anisotropy of Nd2Fe14B phase after annealing.     

Relationship between crystal growth mode,preferred orientation and magnetostriction of （Tb0.3Dy0.7）Fe1.95 alloys

The relationship between crystal growth mode, preferred orientation and magnetostrictive properties of （Tb0.3Dy0.7）Fe1.95 alloys was investigated at different directional solidification rates. The results showed that preferred orientation had a strong influence on the characteristics of （Tb0.3Dy0.7）Fe1.95 alloys. At lower solidification rates, the sample with 〈110〉 preferred orientation showed larger low-field magnetostriction and apparent compressive stress effect. The excessive solidification rate resulted in failure of preferred orientation and a poor magnetostrictive performance. With an increase in solidification rates, the crystal growth modes changed gradually from cellular and primary dendrite morphology to developed dendritic morphology. In addition, domain configurations were observed using magnetic force microscopy, and the change of magnetostrictive properties was interpreted in terms of revealing the domain configurations.     

Relationship between crystal growth mode, preferred orientation and magnetostriction of (Tb0.3Dy0.7)Fe1.95 alloys

The relationship between crystal growth mode, preferred orientation and magnetostrictive properties of (Tb0.3Dy0.7)Fe1.95 alloys was investigated at different directional solidification rates. The results showed that preferred orientation had a strong influence on the characteristics of (Tb0.3Dy0.7)Fe1.95 alloys. At lower solidification rates, the sample with <110> preferred orientation showed larger low-field magnetostriction and apparent compressive stress effect. The excessive solidification rate resulted in failure of preferred orientation and a poor magnetostrictive performance. With an increase in solidification rates, the crystal growth modes changed gradually from cellular and primary dendrite morphology to developed dendritic morphology. In addition, domain configurations were observed using magnetic force microscopy, and the change of magnetostrictive properties was interpreted in terms of revealing the domain configurations.     

Synthesis of Ti-Ce-Si Binary and Ternary Nanocomposite Photocatalyst by Supercritical Fluid Drying Technology

Recently,photodegratation of various organiccontaminants with powdered semiconductors as cata-lysts has received much attention for their potential inthe utilization of light energy.TiO2is one of the mostwidely used photocatalysts due toits relatively nontox-ic,high activity,strong oxidizing property,and excel-lent stability.However,some weaknesses such as poormechanic strength,compressive strength and thermalstability have li mited its industrial applications.Therefore,it is necessary to i mp…     

Micromagnetic Analysis on Demagnetization Process of Single-Phase Nanocrystalline Permanent Magnets with Different Degrees of Orientation

A three-dimentional finite element micromagnetic algorithm was developed to study the magnetization reversal of Pr2Fe14B single-phase nanocrystalline permanent magnets. A single-phase nanocrystalline Pr2Fe14B magnets composed of 216 irregular shaped grains was built. The magnetic hysteresis loops were simulated by micromagnetic finite element method. The contribution of intergrain exchange coupling ment degree （IGEC） to remanence enhancement is considered related to the alignin oriented magnets, and decreased with improved grain alignment. For the magnets with perfectly crystallo- graphic alignment of grains, the contribution of IGEC to remanence enhancement is nearly zero. The shape of demagnetization curve is not only dependent on grain alignment degree but also on the strength of IGEC in magnets.     

固化温度和时间对快淬粘结磁体性能的影响

用E20环氧树脂加入固化剂顺丁烯二酸酐制备了快淬（Nd，Pr）FeCoZrB粘结磁体，研究了固化温度和时间对粘结磁体抗压强度和磁性能的影响。随固化温度升高，固化时间增加，粘结磁体的交联反应充分进行，抗压强度明显增加；但由于聚合交联反应生成的水腐蚀磁粉，以及高温固化时磁体空隙中的氧气与磁粉发生了氧化，使磁体磁性能显著降低。     

Preparation Technology and Performances of Zn-Cr Coating on Sintered NdFeB Permanent Magnet

Since appearing in1983,sintered NdFeB perma-nent magnet has been applied widely and become ani mportant basic material in high technology fields be-cause of its excellent magnet property,wide sources ofraw material and low price[1].Active phase such asNd-rich phase and B-rich phase in NdFeB permanentmagnet facilitated easy corrosion in corrosion medium,which weakenedits magnet property,andturnedit intopowder-like,non-usable product.So surface treatingfor anticorrosion was veryi mportant for…     

稀土永磁及磁记录材料的矫顽力与有效激活体积

指出了文献 [1]中的一个错误。给出了不同模型的稀土永磁材料以及磁记录材料的矫顽力 Hc和有效激活体积υ之间的正确关系 ,这样的关系被表示成一个复杂的函数关系 ,同时指出 ,对不同模型的稀土磁性材料 ,这个函数关系是不同的