Nd2Fe14B/α - Fe/Nd2Fe14B磁性三层膜的微磁学模拟

以Nd2 Fe14B/α - Fe/Nd2 Fe14B三层膜为对象,应用微磁学理论计算了该体系的磁滞回线,并对其磁性能与软磁层厚度的关系进行了分析.结果表明,当软磁层厚度小于临界尺寸(5nm)时,磁滞回线为矩形,三层膜完全耦合；当软磁层厚度为5nm时,最大磁能积可达到最大值642.51 kJ/m3.在所研究的软磁层厚度范围内,随着软磁层厚度的增加,三层膜矫顽力单调下降.     

Nd2Fe14B/Fe3B基纳米复合粘结磁体的磁特性

通过实验研究了Nd2Fe14B／Fe3B双相纳米复合磁粉分别与几种不同性能的磁粉复合成粘结磁体后磁性能的变化。通过对复合磁体的理论分析得知，由Nd2Fe14B／Fe3B与RE2Fe14B或铁氧体磁粉复合成的粘结磁体中，成分间并未发生化学反应。以Nd2Fe14B／Fe3B铁氧体复合粘结磁体为例，根据理论分析推出的剩磁Br-成分含量关系曲线与实际曲线吻合得很好，表明剩磁与成分含量间存在着近似的线性关系，从而可通过数学手段建立磁性能参数与成分含量的函数关系式，用于简化混粉工艺。另外，添加铁氧体可对该复合磁体较差的热稳定性起到补偿作用，并减少了磁不可逆损失。     

Computer Simulated Magnetic Properties of Nd2Fe14B/α-Fe Nanocomposite Magnets

Micromagnetic models of assemblies of randomly oriented, exchanged coupled nanocrystals consisting of magnetically hard Nd₂Fe₁₄B and very soft alpha Fe have been simulated. The modeling of two-dimensional chessboard consisted of 50 vol. % hard and 50 vol.% soft nanocrystals with the size varying from 5, 10, 25, to 50 nm. Hysteresis curves of each model system were obtained by solving the Landau-Lifshitz-Gilbert equation by time integration of the stiff differential equations. The simulation was focused on the effect of domain size and distribution in each nano crystal of fixed size. Eventually the simulated results were compared with magnetic properties obtained from experimental results of NdFeNbB based magnetic alloys showing the identical grain sizes to the simulated model. The present study exhibited the important role of soft phase in terms of volume fraction and arrangement of the phase.     

纳米晶Fe_3B/Nd_2Fe_(14)B粘结永磁体的磁性能研究

本文研究了粘结剂含量和温度－时间变化对纳米晶Ｆｅ３Ｂ／Ｎｄ２Ｆｅ１４Ｂ粘结永磁材料的磁性能影响。结果表明降低粘结剂含量可显著地提高纳米晶Ｆｅ３Ｂ／Ｎｄ２Ｆｅ１４Ｂ粘结永磁的磁性能；环境温度对纳米晶Ｆｅ３Ｂ／Ｎｄ２Ｆｅ１４Ｂ粘结永磁的磁性能具有重要影响，在较高的温度下其磁性能将显著下降，因此纳米晶Ｆｅ３Ｂ／Ｎｄ２Ｆｅ１４Ｂ粘结永磁只能在较低的温度环境下使用     

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.     

Nd2Fe14B/α-Fe和Pr2Fe14B/α-Fe型纳米晶永磁合金工艺与性能的对比研究

对快淬法制备的Nd2Fe14B/α-Fe和Pr2Fe14B/α-Fe型双相纳米晶永磁在快淬条件和晶化过程中的软、硬磁相之间晶粒的形核长大行为作了对比,发现PrFeB系更容易得到较好磁性能。     

Magnetomechanical Properties of the Alloy Nd2Fe14B

We have studied the elastic and inelastic properties of the polycrystalline ferromagnet Nd₂Fe₁₄B in the temperature range 20–550 °C. We used the low-frequency (80 Hz) internal friction method to measure the Curie point of Nd₂Fe₁₄B. We observe an internal friction peak at T ≈ 280 °C. The nature of this peak is explained in terms of the magnetoelastic saturation concept.__________Translated from Poroshkovaya Metallurgiya, Nos. 3–4(442), pp. 87–93, March–April, 2005.     

合金元素对Nd2Fe14B/α-Fe磁性能的影响

通过单一添加 ,研究了C ,Pr,Nb对Nd2 Fe1 4B/α Fe纳米复合永磁体磁性能的影响 ;用少量C取代B ,可以显著提高Nd9Fe85.5Nb1 .0B4 .5-yCy 永磁体的内禀矫顽力iHc,用Pr代替部分Nd可以提高双相快淬薄带的矫顽力并改善退磁曲线的矩形度。当Nb含量控制为 0 .5 %时 ,Nd2 Fe1 4B/α Fe的各项磁性能均有显著提高。采用五因子二水平正交分析方法 ,研究了Ga ,Nb ,Zr,Hf和Pr复合添加对磁性能的作用。Nb是影响剩余磁极化强度Jr 和最大磁能积 (BH) max最为显著的因子 ,而Pr对iHc 的影响最强烈。另外 ,在Nb ,Pr之间 ,Nb ,Hf之间 ,Ga与Pr以及Ga与Hf之间的交互作用也对磁性能有显著影响 ,优化的合金成分为Nd2 .2 5Pr6 .75Fe84 .5Ga1 .5Nb0 .5B4 .5,在 15m·s- 1 带速下获得的最佳磁性能为Jr=1.0 5 3T ,iHc=5 3 0 .9kA·m- 1 ,(BH) max=12 4kJ·m- 3。     

Segmentation and Alignment of Nd2Fe14B Platelets in Nd-Cu Eutectic Alloys Using the Electromagnetic Vibration Technique

Metallurgical and Materials Transactions A - An anisotropic Nd2Fe14B magnet has been of particular significance in engineering, which is usually produced via powder metallurgy. In this study, we...     

Effect of Multiple Alloying Elements on Microstructure and Magnetic Properties of Nanocomposite Nd2Fe14B／α-Fe Magnets

TheappearanceofnanocompositemagnetsbroketheremanencelimitpredictedbyStoner Wolhfarthmodethattheremanenceofisotropicmagnetwouldnotexceedhalfofitssaturationmagnetization[1] .Accord ingtoSkomski′scalculation[2 ] ,highmaximalenergyproduct (BH) maxof 80 0kJ·m-3 couldbeachievedinNd2 Fe14 B α FenanocompositewhentheaveragegrainsizeofNd2 Fe14 Bisrefinedtoabout 2 0nmandthatofα Fetoabout 10nm ,becauseoftheeffectofrema nenceenhancement (Mr Ms >0 .5 ) .Unfortunately ,thereported (BH) max(185kJ·…     

Structural State and Magnetic Properties of Nd2Fe14B-Type Rapidly Quenched Alloys

Using the X-ray, elastic neutron diffraction (END) and small angular neutron scattering (SANS) methods (Diffractometers D2 and D3 respectively), transmitting electronic microscopy (JEOL JEM-200CX) and magnetometry technique (vibrating sample magnetometer - VSM) the structure and magnetic properties of the rapidly quenched (RQ) alloys of the following compositions: A) Nd₁₄Fe₇₈B₈; B) Y₁₂Fe₈₂B₆; C) Nd_13.3Co_6.6Fe_72.6Ge_0.9B_6.6; D)Nd₉Fe₈₅B₆; E) Nd₉Fe₇₉B₁₂; F) Nd₉Fe₇₄Ti₄CB₁₂ have been studied. At some quenching conditions or after consequent heat treatments of these alloys the nanoscale state of the main 2–14–1 phase and α-Fe grains can be formed. Their size depends on the sample-preparation conditions and lies in the interval of 10–200 nm. Their influence on magnetic properties of alloys under study is discussed.     

Electrical and Magnetic Properties of Nd2Fe14B Magnet in Demagnetized and Magnetized States at Low Temperatures

Below room temperature the spin reorientation phase transition was observed for Nd₂Fe₁₄B magnet with T_sr ∼ 135 K. Spin reorientation refers to a change in the preferred direction of the M magnetization. The Nd₂Fe₁₄B magnet changes from a uniaxial or easy-axis material at TT_sr to an easy-cone material at T <T_sr. The transition from easy-axis to easy-cone anisotropy is an interesting physical phenomenon, which is important in a practical sense. The purpose of the present work is to study the electrical and magnetic properties of Nd₂Fe₁₄B magnet in the interval of temperatures ∼ 15–273 K in demagnetized and magnetized states. For the first time measurements of electrical resistance (ρ) and a complex magnetic susceptibility (χ = χ′+iχ″) of Nd₂Fe₁₄B alloy in demagnetized state and at two directions of magnetization in a range of temperatures ∼ 15–273 K were carried out. The following new effects were found out: (i) It was established that occurrences of the positive contribution to the value of ρ at the perpendicular magnetization and the negative contribution at the parallel magnetization. (ii) It was shown that, the value of the magnetic contribution in resistivity at the parallel magnetization, Δρ|, has a minimum in a vicinity of temperature of the spin reorientation transition, T_sr. (iii) It was established the occurrence of maximums of χ′ and χ″ values in a vicinity of temperature of the spin reorientation transition. (iv) It was established that T_sr value at perpendicular magnetization goes down and at parallel magnetization increases in comparison with the demagnetized sample. The received data have the practical importance for the application of Nd₂Fe₁₄B based permanent magnets at low temperatures.     

金属间化合物Nd(Fe1-xCox)10V2的结构和磁性研究

通过 X射线衍射和磁测量等手段对金属间化合物 Nd(Fe1 - x Cox) 1 0 V2 的结构和磁性进行了研究。结果表明 ,金属间化合物 Nd(Fe1 - x Cox) 1 0 V2 (x=0 ,0 .0 5 ,0 .1,0 .15 ,0 .2 )的晶体结构均为 Th Mn1 2 型结构 ;随着 Co含量 x的增大 ,晶格常数 a、c和晶胞体积 V将单调减小 ,居里温度 Tc呈单调增大 ,饱和磁化强度 Ms逐渐增加。取向样品Nd Fe1 0 V2 的 X射线衍射和变温穆斯堡尔谱研究结果表明该化合物在 T=12 0 K条件下存在自旋重取向现象。     

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.     

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.     

Magnetic Properties and Molecular Field Analysis of （ Ce, Nd） 2 （Fe, Si, Mn） 17 Compounds

The temperature-dependent magnetization of the ( Ce, Nd) 2 (Fe, Si, Mn) 17 intermetallic compounds were measured and analyzed by molecular field theory (MFr). The relationship between Tc and the intrasublattice coupling interactions was discussed. The two-sublattice MFT model can well describe the temperature dependence of the magnetization for all the compounds investigated. Ce ion in (Ce, Nd)2Fel7 compounds does not simply dilute the magnetic structure, but is likely present in a mixed-valence state. The substitution of Si for Fe strongly raises Tc and the mean Fe moment remains unchanged for Ce2(Si, Fe)17 compounds, and the 3d exchange coupling constant JFF increases linearly. Mn decreases Tc of Nd2(Mn, Fe)17 compound by reducing JFF。     

Dependence of Effective Anisotropy on Grain Size in Nanocrystalline Nd2 Fe14 B Hard Magnetic Material

Anisotropy of material is the key factor determin ing coercivity and anisotropy of nano grain is dramati cally influenced by grain size[1~2]. So the coercivityof nano magnetic material with different grain sizeswould have obvious difference.…     

钕铁硼中不同状态氧释放行为的研究(英文)

钕铁硼磁体中氧含量偏高是影响其大工业生产、造成钕铁硼磁体性能偏低的主要原因之一,因此合理地控制氧在钕铁硼中含量及其存在状态,为分析工作提出了重要研究课题。依据样品中不同状态氧与碳的结合能不同的特点,本文使用惰气熔融红外吸收法对钕铁硼材料样品中不同状态氧进行了定性和定量的方法研究。首先通过斜率加热模式,确定钕铁硼样品在不同分析加热电流下存在着两种状态氧化物。根据斜率加热模式下得到的每种状态氧化物对应的释放条件,使用分段加热模式,完全分离两种状态氧的释放峰。对原始样品和第一段加热后的中间产物分别进行x射线衍射