Research progress of permanent ferrite magnet materials

Permanent ferrite magnet materials are extensively employed due to their exceptional magnetic properties and cost-effectiveness.The fast development in electromobile and household appliance industries contributes to a new progress in permanent ferrite materials.This paper reviews the deveolpement and progress of permanent ferrite magnet industry in recent years.The emergence of new raw material,the advancement of perparation methods and manufacturing techniques,and the potential applications of permanent ferrite materials are introduced and discussed.Specifically,nanocrystallization plays a crucial role in achieving high performance at a low cost and reducing reliance on rare earth resources,and therefore it could be a promising development trendency.

Recent progress in high temperature permanent magnetic materials

Permanent magnetic materials capable of operating at high temperature up to 500℃ have wide potential applications in fields such as aeronautics, space, and electronic cars. SmCo alloys are candidates for high temperature applications, since they have large magnetocrystalline anisotropy field （6-30 T）, high Curie temperature （720-920℃）, and large energy product （〉200 kJ.m-3） at room temperature. However, the highest service temperature of commercial 2：17 type SmCo magnets is only 300℃, and many efforts have been devoted to develop novel high temperature permanent magnets. This review focuses on the development of three kinds of SmCo based magnets： 2：17 type SmCo magnets, nanocrystalline SmCo magnets, and nanocomposite SmCo magnets. The oxidation protection, including alloying and surface modification, of high temperature permanent magnets is discussed as well.

The Production Management Improvement Model of Small and Medium-sized Permanent Magnetic Materials Manufacturing Companies

An integrated production planning and control model based on MRPⅡand JIT is put forward through analyzing the characteristics of magnetic materials manufacturing companies. Master Production Schedule with limited capacity and operational plan in workshop level based on the basic data of flow chart are formulated by this model which applied JIT idea and based on customer order demand. Push production is adapted during execution phase combined with process flow cards. The model is helpful to reduce inventory,keep certain flexbility of production and improve continuity and equilibrium of manufacturing process.

Design and Performance Analysis of Permanent Magnet Claw Pole Machine with Hybrid Cores

Permanent magnet claw pole machine(PMCPM) is a special kind of transverse flux permanent magnet machine. Compared with other electrical machines, it has the advantages of high torque density and high efficiency for high speed operation. However, because of its complex irregular structure, the manufacturing process using silicon sheets is complicated. Soft magnetic composite material(SMC) is manufactured by powder metallurgy technology, which can produce various shapes of stator core structures, so it is easier to produce various irregular shapes of the stator core. However, the raw SMC material is relatively expensive, and the mechanical strength of SMC is weak. In this paper, a PMCPM with hybrid cores is proposed. With the adoption of hybrid silicon sheet-SMC cores and amorphous alloy-SMC cores, the torque ability of PMCPM can be improved greatly and it can have higher efficiency for more wide operation frequency. Meanwhile, its mechanical strength has been improved and it can be designed for high torque direct drive applications as it is a modular machine. Furthermore, three methods are proposed to reduce the additional eddy current loss which resulted from the employment of hybrid cores in PMCPM.

An Empirical Study of CAPM’s Applicability to Rare Earth Permanent Magnet Material Stocks

China has the world’s largest reserves of rare earth elements.Rare earth permanent magnet material has always been one of the popular industries in the investment market.CAPM is the basic asset-pricing model in financial economics.There are a number of studies conducted to examine the applicability of CAPM to stock markets in different industries and to investigate the modification method to improve the model’s prediction accuracy.In this study,seven leading enterprises in China’s rare earth permanent magnet material industry listed on the A-share market were selected as the research subjects.Based on CAPM,regression analysis was conducted on the monthly data from March 2016 to February 2022.The results demonstrated that using the β coefficient to explain the risk of China’s rare earth permanent magnet industry is ineffective.The ultimate benefit was less affected by market indexes but mainly by non-systematic risks.CAPM has low applicability to China’s rare earth permanent magnet material industry and requires further improvement.Nevertheless,CAPM still has some guiding significance in making enterprise comparisons and investment decisions.

A Study of Two-Phase Nanocrystalline Nd_(8.5)Fe_(75)Co_5Cu_1Zr_3Nb_1B_(6.5)Permanent Magnet

Nanocrystalline Nd 8.5 Fe 75 Co 5Cu 1Zr 3Nb 1B 6.5 ribbons were prepared by melt spun (18 m·s -1 ) and subsequent heat treatment (670 ℃/4 min). Excellent magnetic properties of the bonded magnet were achieved as follows: B r=0.68 T (6 8 kGs), J H c=620.3 kA·m -1 (7.8 kOe), ( BH ) max =74 kJ·m -3 (9 3 MGOe). The results of TEM photomicrographs confirm that the appearance of α Fe phase is earlier than that of Nd 2Fe 14 B phase during crystallization process. The addition of Cu and Zr elements shows to be advantageous to the improvement of an intrinsic coercivity and squareness of hysteresis loop, as well as energy product.

Mn-based permanent magnets

Mn-based intermetallic compounds have attracted much attention due to their fascinating structural and physical properties,especially their interesting hard magnetic properties.In this paper,we have summarized the magnetic and structural properties of Mn-based intermetallic compounds(Mn X,where X=Al,Bi,and Ga).Various methods for synthesizing single phases of MnAl,MnBi,and Mnx Ga were developed in our lab.A very high saturation magnetization of 125 emu/g,coercivity of 5 kOe,and maximum energy product(BH)_(max)of 3.1 MG·Oe were achieved at room temperature for the pureτ-Mn–Al magnetic phase without carbon doping and the extrusion process.Low temperature phase(LTP)MnBi with a purity above 95 wt.%can be synthesized.An abnormal temperature coefficient of the coercivity was observed for the LTP MnBi magnet.Its coercivity increased with temperature from 100 K to 540 K,reached a maximum of 2.5 T at about540 K,and then decreased slowly to 1.8 T at 610 K.The positive temperature coefficient of the coercivity is related to the evolution of the structure and magnetocrystalline anisotropy field of the LTP MnBi phase with temperature.The LTP MnBi bonded magnets show maximum energy products(BH)_(max)of 8.9 MG·Oe(70 kJ/m^(3))and 5.0 MG·Oe(40 k J/m^(3))at room temperature and 400 K,respectively.Ferrimagnetic Mn_(x)Ga phases with L10 structures(x〈2.0)and D0_(22)structures(x〉2.0)were obtained.All of the above structures can be described by a D0_(22)supercell model in which 2 a-Ga and 2 b-Mn are simultaneously substituted.The tetragonal D0_(22)phases of the Mn_(x)Ga show high coercivities ranging from 7.2 kOe for low Mn content x=1.8 to 18.2 kOe for high Mn content x=3 at room temperature.The Mn_(1.2)Ga sample exhibits a room temperature magnetization value of 80 emu/g.The hard magnetic properties of coercivityiH_(c)=3.5 kOe,remanence M_(r)=43.6 emu/g,and(BH)_(max)=2.5 MG·Oe were obtained at room temperature.Based on the above studies,we believe that Mn-based magnetic materials could be promising candidates for rare earth free permanent magnets exhibiting a high Curie temperature,high magnetocrystalline anisotropy,and very high coercivity.

Development of Strip Casting Technology in Rare Earth Permanent Magnet Alloys and Hydrogen Storage Alloys in China

The SC technique is now being applied widely in material preparation, especially in rare earth functional materials in virtue of its advanced process and high performance product. The applications of SC technique in rare earth permanent magnet alloys and hydrogen storage alloys were analyzed integrative, on the basis of summary of SC technique development in this paper. The paper mainly includes development history of SC technology, effect of SC technology on alloy microstructure, application of SC technology in RE storage hydrogen alloy and sintered Nd-Fe-B alloy, development of SC equipment and SC product industry. At the same time, the paper points out the existing problem of SC products.

Enhancing magnetic properties of anisotropic NdDyFeCoNbCuB powder by applying magnetic field at high temperature during hydrogen desorption

Anisotropic powder was prepared with precursor （NdDy）-（FeCoNbCu）-B sintered magnets by hydrogen decrepitation, desorption, and subsequent annealing treatment. The hydrogen desorption was performed in magnetic fields of 0, 1, 3, and 5 T. The orientation of tetragonal phase grains of the powder was evaluated from the hysteresis loops measured by extraction magnetometer. Residual hydrogen content of the powder was evaluated by thermal-magnetic analysis. The powder with Hcj, Br, and （BH）max of 1138 kA.m^-1, 1.029 T, and 172.5 kJ.m^-3, respectively, was achieved under the condition of the magnetic field of 3 T. Magnetic properties of the powder, especially, the remanence of the powder, are enhanced upon magnetic fields, which is due to better orientation of powder particles and less residual hydrogen in the powder resulted from the magnetic field during the hydrogen desorption process.

Dependence of Magnetic Properties of Rapidly Quenching (Nd,Pr)_x (FeCoZr)_(94-x)B_6 Bonded Magnets on Rare Earths Content

By using sub-overquenching and annealing method which has a wide processing window, (Nd, Pr), ( Fe-CoZr)(94-x)B-6(x = 12, 10.5, 10, 9) bonded magnets were prepared and the effect of rare earths content on magnetic properties was investigated. Being spun at sub-ove.quenching speed the as-spun ribbons consist of amorphous phases mixed with fine crystallites. After crystallization under optimum annealing conditions and bonded with 3.25% (mass fraction) epoxy, the magnets obtained the optimum magnetic properties. The rare earths content directly determines the magnetic properties. With the reduction of rare earths content, B-r increases but H-ci and (BH)(max) decrease. x = 10 is the critical value for the magnetic proper-ties change. Below this value, Br increases slowly meanwhile H-ci and (BH)(max) decrease strongly because alloy contains extra fractions of soft magnetic phase which are not coupled with the hard magnetic phase.. This experimental result is consistent with the calculated results using the model of volume fraction of soft magnetic phase coupled completely suggested.

Structure and Magnetic Properties of LaCo_(13-X)M_X Intermetallic Compounds

LaCo_(13) has the highest 3d metal content ,of any known rare-earth intermetallic compounds,a1. 03MA/m saturation magnetization at room temperature and a high T_c (1318K). Unfortunately ,it is cubic ,lacking of the necessary anisotropy,thus diminishing the chance that it will be used as a permanent rnagneticmaterial. In this paper ,the structure and magnetic properties of LaCo_(13) Six (x=2 , 4 )and LaCo_(13) Ge_X(x=2,2. 5 ,3 ,4)intermetallic compounds have been studied. The crystal structure was found to be tetragonal whenx=4 for LaCo_(13-X) Six and x=3 , 4 for LaCo_(13-X) Gex ,but the difference between the lattice parameters a and c isvery small. In order to gain the tetragonal structure ,the annealing temperature of LaCo_(13-X) Ge_X must be con-trolled strictly. The magnetic rneasurement results show that the Curie temperatures of all these compoundsare high ,but the saturation magnetization at room-temperature decreases greatly with x increasing.

Magnetic force improvement and parameter optimization for magnetic abrasive polishing of AZ31 magnesium alloy

The magnetic force acting on workpiece to be machined plays a significantly important role in magnetic abrasive polishing process.But in a case of polishing nonferrous materials,the strength of magnetic force is very low and it leads lower polishing efficiency.The magnesium alloy that has superior mechanical properties for industrial application such as a lightweight and high specific strength is one of the most famous nonferrous materials.An improving strategy of the magnetic force for the AZ31 magnesium alloy installed with a permanent magnet was proposed and experimental verification was carried out.For the proposed strategy,the effect of process parameters on the surface roughness of the AZ31 magnesium alloy was evaluated by a design of experimental method.

Neutron diffraction studies of permanent magnetic materials

Neutron diffraction technology as an advanced material research technique has special advantages in studying magnetic materials compared to the conventional techniques such as X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and X-ray photoelectron spectroscopy(XPS).In this review,the applications of neutron diffraction technology on permanent magnetic materials were briefly reviewed:(1)the determination of the crystal structure and magnetic structure of the typical permanent magnet material,(2)in situ neutron diffraction study of the crystal structure evolution of the permanent magnets,and(3)phase transition in permanent magnetic materials.

Influence of Pr on Magnetic Properties and Microstructure of Melt-Spun(Nd_(1-x)Pr_x)_(10.5)(FeCoZr)_(83.5)B_6 Alloy

The influence of Pr on thermal stability, microstructure, and magnetic properties of melt-spun (Nd1-xPrx)(10.5)(FeCoZr)(83.5)B-6(x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) alloy was investigated. By sub-overquenching to get the mixture of amorphous and fine crystallites and post annealing under the optimum conditions, bonded magnets with the best magnetic properties were prepared. With the increase of Pr content, H-ci increases, but B-r decreases. (BH)(max) of magnets bonded with 3.25% (mass fraction) epoxy reaches the maximum of 70.6 kJ .m(-3) at x = 0.6 similar to 0.8. Substitution of Pr for Nd causes the crystallization temperature and crystallization energy to decrease. This thermal stability difference results in that (Nd0.8Pr0.8)(10.5)(FeCoZr)(83.5)B-6 alloy has a rougher and more inhomogeneous microstructure than that of (Nd(0.8)Pro(0.2))(10.5)(FeCoZr)(83.5)B-6 alloy, furthermore, leads to the decrease of B-r with the increase of Pr content.

Preparation of Rapidly Quenching (Nd,Pr)_(12)(FeCoZr)_(82)B_6 Alloy and Magnetic Properties of Bonded Magnets

The optimum quenching rates and annealing conditions to prepare near stoichiometrical (Nd,Pr)(12)(FeCoZr)(82)B-6 bonded magnets were investigated by using sub-overquenching and post annealing method. The quenching rates, annealing temperatures, and annealing time directly influence the microstructure and magnetic properties of alloy ribbons. The optimum magnetic properties of bonded magnets are achieved by melt spinning at 24 m (.) s(-1) wheel surface speed, annealing at 655 degreesC for 10 min, and bonding with 3.25% (mass fraction) epoxy. The best magnetic properties of remanence B-r, intrinsic coercivity H-ci and maximum energy product (BH)(max) are 0.669 T, 811 kA (.) m(-1), and 75 kJ (.) m(-3), respectively.

Effect of Zr on Microstructure and Magnetic Properties of Nanocrystalline (Nd, Pr)FeB/α-Fe Composite Alloys

For nanophase (Nd, Pr)FeB/α-Fe composite alloys were prepared by melt spinning, the appreciable addition of Zr reduces their average grain size. Observed by atom force microscopy (AFM), the average grain diameter of crystallized ribbons on their free surface, reduces from 175 nm of Zr-free alloy to 79 nm of Zr-1at%, by about 55%. If the concentration exceeds 1%, the effects of Zr on fining grain size are evidently weakened. The average grain size on free surface of Zr-1.5at% is 72 nm. With the addition of 1at% Zn, the bonded magnets has the best combination of properties: B_r=0.675 T, H_(ci)=616 kA·m^(-1), (BH)_(max)=77 kJ·m^(-3). Below 1at%, the coarser grains lead to a lower magnetic property. Beyond 1at%, the layer of Zr-rich intergranular phase will thicken, which results in weakening of the exchange coupling among adjacent grains, and then causes degrading of magnetic properties of magnets.

Editorial for rare metals,special issue on advanced permanent magnetic materials

Permanent magnetic materials(PMMs)are a kind of indispensable functional materials in modern society,which play crucial role in many applications such as computers,medical devices,and home appliances.Specially,with the rapid development of green technologies such as electric transportation,wind turbines,and precision motors,the need for high-quality PMMs has become strong and urgent.Meanwhile,the cutting-edge researches involving development and improvement of PMMs and related theories have drawn considerable attentions.This motives rare metals to have a special issue focusing on PMMs.

Effective anisotropy and coercivity in nanocrystalline single-phase NdFeB permanent magnetic material

The effect of exchange-coupling interaction on the effective anisotropy and its varying tendency in nanocrystalline single-phase NdFeB permanent magnetic material have been investigated. The results show that the exchange-coupling interaction between grains makes the effective anisotropy of material, Keff, decrease with the reduction of grain size. The variation of Keff is basically the same as that of coercivity. The decrease in effective anisotropy is the main reason of the reduction of coercivity for nanocrystalline single-phase NdFeB permanent magnetic material. In order to get high anisotropy and coercivity in nanocrystalline single-phase NdFeB permanent material, the grain size should be larger than 35 nm.

轴向磁力轴承结构综述

按照悬浮力的产生方式将轴向磁力轴承分为主动型、被动型和混合型,主动型的优点是能够产生可控电磁力,被动型的优点是结构简单,混合型兼顾了主动型和被动型的特点。在研究同心单环结构的基础上,分析了具备冗余性的同心多环冗余结构及叠片式冗余结构,从电磁力角度看,整体式同心双环结构优于同心三环结构,叠片式六环结构优于叠片式四环结构和叠片式八环结构。最后,对轴向磁力轴承在结构、控制及工业应用方面的发展前景进行了展望,轴向磁力轴承的结构应当朝着更具备冗余性和重构能力的方向优化。

高性能烧结NdFeB永磁材料市场发展与低成本技术途径

烧结NdFeB永磁材料以其优异的磁性能在各领域获得了广泛应用。首先概括了烧结NdFeB永磁材料的应用领域,然后简要介绍了材料的生产工艺流程。在此基础上,重点阐述了烧结NdFeB永磁材料高性能化和低成本化的重要技术途径——重稀土晶界扩散工艺,详细介绍了各类晶界扩散方法及其优缺点。最后展望了高性能烧结NdFeB永磁市场发展趋势。