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/α-Fe纳米晶复合永磁材料的计算机模拟研究

采用计算机模拟的方法计算了 Nd2 Fe1 4B/α- Fe纳米晶复合永磁材料的磁性能 ,并对软磁相比例及不规则晶粒对磁性能的影响进行了研究。结果显示 ,当软磁相比例增加时 ,由于软磁相高的饱和磁极化强度以及软硬磁相间的交换耦合作用的影响 ,剩磁逐渐增加 ,但矫顽力则随着软磁相的增加而逐渐下降。不规则晶粒对磁体的剩磁基本没有影响 ,但降低矫顽力。     

Sm-Co/α-Fe/Sm-Co周期多层膜的微磁学模拟

以Sm-Co/α-Fe/Sm-Co周期多层膜体系为对象,微磁学理论为基础,运用OOMMF软件,采用三维动力学模型系统地模拟研究了该体系的磁性能与磁层厚度和体系层数的关系。结果表明:在所研究的磁层厚度范围内,当固定体系厚度不变和固定体系层数不变时,随着磁层厚度的增加,体系的剩磁和最大磁能积均逐渐减小;硬磁层的磁化反转形式不仅与软磁层的尺寸有关,而且与硬磁层本身的厚度也有一定的关系,也就是说,软磁层的临界尺寸与硬磁层的厚度也有关;体系的层数和厚度对体系的磁性能也有着不可忽略的影响。     

SmCo/Co多层交换弹性纳米晶复合永磁薄膜的制备和磁耦合研究

利用磁控溅射的方法,在室温条件的Si基片上制备了[SmCo(25nm)/Co(x)]4/SmCo(25 nm)多层交换弹性纳米晶复合永磁薄膜(Co层厚度x=0～10 nm),经过550 ℃/20 min的真空退火处理使薄膜结晶后,进行磁性测试和磁耦合分析.结果表明:SmCo层厚度固定为25 nm时,调整Co层的厚度,从0至10 nm逐渐增加,矫顽力从2270.3 kA·m-1逐渐降低至1040.5 kA·m-1,同时,饱和磁化强度和剩磁随Co层厚度增加逐渐增加,上升了60％.当加入10 nm的Co层后,多层膜的最大磁能积比125 nm的单层SmCo薄膜增加了46％.另外,与SmCo/Co双层交换弹性薄膜在退磁过程中表现的零场附近的软硬磁双相行为相比,SmCo/Co多层交换弹性薄膜表现出单相反转行为,说明体系中的两种磁性层具有更好的磁耦合.经过磁耦合研究发现,当Co软磁层较薄时,薄膜中磁性颗粒以颗粒间交换耦合为主;当软磁层厚度增加时,颗粒间交换耦合减弱,静磁耦合增强,保证了软硬磁相之间的良好磁耦合作用.Co层的加入有效地提高了薄膜的磁性能.     

钴含量对烧结钕铁硼居里温度及磁性能影响规律研究

与烧结钐钴磁体相比,烧结钕铁硼稀土永磁具有优异的室温磁性能和力学性能,但其居里温度较低,只有310℃左右,限制了其在耐高温磁应用领域的使用推广。钴元素部分取代钕铁硼中的铁元素可以提高钕铁硼永磁体的居里温度,传统的钴添加方式会使磁体中形成铁钴软磁相,从而造成磁体的矫顽力大大降低。本文研究了不同钴添加量对钕铁硼磁体物相、居里温度和磁性能的影响规律,结合Al、Ga、Cu等元素对钕铁硼永磁体晶界相物相结构的协同调控作用,避免了钴元素取代铁元素过程中Fe-Co软磁相的产生。本研究制备的高钴含量钕铁硼磁体矫顽力高H_cj>28kOe,居里温度T_c>450℃,剩磁温度系数|α|20℃～100℃<0.078%/℃,矫顽力温度系数|β|20℃～100℃<0.55%/℃。     

显微组织对纳米复合永磁材料磁性能的影响的探讨

探讨了显微组织对纳米复合永磁材料的矫顽力、剩磁和最大磁能积的影响.得出了要同时得到良好的磁性能,须综合考虑晶粒尺寸和软磁性含量.设计纳米复合磁体的原则应该是:软磁相和硬磁相的晶粒尺寸分别控制在10 nm和20 nm左右,软磁性含量控制在30%~40%,而且两者之间充分交换耦合.     

磁控溅射法渗镝对烧结钕铁硼性能及显微结构的影响

采用磁控溅射法在钕铁硼表面沉积一层金属Dy,高温扩散后,Dy扩散进入磁体内部,与磁体中Nd发生置换,形成均匀连续的富Nd相,并在主相晶粒表层区域形成(Nd,Dy)2Fe14B相,扩散深度约为350μm。其中,厚度为10 mm的无Dy磁体和低Dy含量磁体添加1%Dy(质量分数)后,经扩散处理,矫顽力分别提高了52.1%和32.2%。结果表明,经磁控溅射法渗镝,钕铁硼矫顽力显著提高,剩磁无明显降低。     

流态化气相沉积温度对FeNi50/SiO2复合粉末形成过程及性能影响北大核心

为探明流态化气相沉积过程中核壳结构的形成温度,在正硅酸乙酯热分解的热力学基础上,通过设置不同反应温度,在FeNi50合金粉末表面包覆SiO2绝缘层,采用XRD、FTIR、SEM以及VSM等测试分析仪器对粉末形貌、成分和性能进行了表征。结果表明:正硅酸乙酯的热分解温度为612.70℃,合成具有FeNi50/SiO2核壳结构的软磁复合粉末的最低温度为630℃,软磁复合粉末SiO2绝缘包覆层的厚度为0.520μm;随着沉积温度的升高,SiO2绝缘层厚度也随之增加,FeNi50/SiO2复合粉末的饱和磁感应强度逐渐降低,矫顽力几乎无变化,电阻率呈增加趋势,相对于原料FeNi50合金粉末,具有FeNi50/SiO2核壳结构的软磁复合粉末的电阻率提高了近两个数量级。     

高Dy含量烧结Nd-Fe-B的晶界扩散处理研究

研究了晶界扩散处理对高Dy含量烧结Nd-Fe-B磁体性能和结构的影响。经蒸镀渗Dy晶界扩散处理,高Dy含量Nd-Fe-B磁体的矫顽力从1 713 kA/m提高至2 161 kA/m,而剩磁和最大磁能积基本没有下降,处理后磁体内Dy平均质量分数仅增加0.30%。不同深度片层分析表明,虽然磁体近表面片层比中心片层的Dy含量高,但是片层间矫顽力相差较少,而且所有片层的矫顽力均远高于未处理磁体片层的矫顽力。电子探针Dy元素面分布结果显示,在未处理高Dy含量磁体的晶界与主相中均存在Dy元素富集区且富集浓度较低,而经扩散处理后,晶界富Nd相中的Dy富集区浓度及所占比例明显提高;包括磁体芯部在内,磁体内大部分角隅处富Nd相内Dy含量明显增加,进一步提高了高Dy含量磁体内部各处的矫顽力。     

Finemet合金Fe73.5Si13.5B9Cu1Nb3在较低退火温度条件下Hc,Br,Ps的比较

通过比较Finemet金属非晶薄带,在较低退火温度(450℃、500℃、530℃)下矫顽力Hc、剩磁Br以及损耗Ps的差异,得出关于其软磁性能优劣的结论,力图阐明退火温度等对Finemet金属晶化过程及软磁性能的影响.利用线性拟合的方法,得出了不同频率下关系式Ps=aT b当中的常数a、b,进一步说明了Finemet金属薄带在高频时的优异软磁性能.     

Magnetic Properties and Kinetics Parameters of Electroless Magnetic Loss CoFeB Films

Electroless CoFeB films with good soft magnetic properties were fabricated on polyester plastic substrate from sodium tartarate as a complexing agent.The plating rate of electroless CoFeB films is a function of concentration of sodium tetrahydroborate,pH of the plating bath,plating temperature and the metallic ratio.The estimated regression coefficient b0-b3 confidence interval,residual error r and confidence interval rint were confirmed by a computer program.The optimal composition of the plating bath was obtained and the dynamic electromagnetic parameters of films were measured in the 2-10 GHz range.At 2 GHz,the μ＇,μ″ of the electroless CoFeB films were 304 and 76.6,respectively,as the concentration of reducer is 1 g/L.Magnetic hysteresis loop of the deposited CoFeB films show a remanence close to the saturation magnetization and coercivity of about 55.7-127.4 A/m.The loops along the hard axis display low anisotropic field Hk of 2 388-3 582 A/m.     

铜闪速熔炼烟灰酸浸渣制备磁性材料

为了综合回收利用铜闪速熔炼烟灰,对铜闪速熔炼烟灰酸浸渣制备磁性材料进行了探索性研究.对熔炼烟灰酸浸渣进行了不同浓度盐酸浸出渣和除铅等工艺处理,研究了各工艺下浸出渣的磁性能.结果表明:杂质的去除有利于饱和磁化强度和剩磁的提高,但导致矫顽力下降.盐酸浸出处理的最佳性能出现在当盐酸浓度为3 mol/L时,饱和磁化强度和剩磁分别为10.965 A·m2/kg和0.964 A·m2/kg,矫顽力为3.33×103 A/m;除铅处理后浸出渣的磁化强度和剩磁分别达到11.065 A·m2/kg和0.94 A·m2/kg,矫顽力为3.228×103 A/m.      

Magnetic Properties of B-Rich Nano-Composite REyTM 90-y-xNbxB10 Alloys

We report and discuss the results of a study of the structures and magnetic properties of B-rich (10 at%) nanocomposite alloys, based on the formula RE_yTM_90-y-x Nb_xB₁₀ (RE=Nd, Nd+Pr, TM=Fe, Fe+Co; y=8,10,12, x=0,2,4) and processed by devitrification of melt-spun amorphous precursors. Considerable enhancement of the intrinsic coercivity, together with good to excellent remanence and energy density values were observed for Co-containing compositions with y =10 and x =2,4. The intrinsic coercivity and remanence enhancements are ascribed to the grain refining effects of Nb, particularly with respect to the soft magnetic phases, and thus to more complete exchange coupling of the soft grains to the hard phase grains than for the Nb-free alloy.     

A Monte Carlo study of spring-exchange magnets containing ultra-high coercive phases

The aim of the present work is to study magnetization processes in the spring-exchange magnetic composites containing magnetically soft, hard and ultra-high coercive phases, experimentally found in Tb-Fe-B-Nb group of alloys. In order to modeling hysteresis loops a special Monte Carlo procedure,suitable for irregular geometry of the composites, was applied. The obtained results indicate that sufficiently strong coupling between soft and hard magnetic phase leads to collective, single-phase-like movement of such phases, which in turn, causes increase of the coercivity and internal magnetic energy.     

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…     

Magnetic Properties of （Sm, Tb）FeCo/Cr/TbFeCo Trilayers with Perpendicular Anisotropy

A series of （Sm, Tb）FeCo/Cr/TbFeCo trilayers with perpendicular anisotropy was prepared by RF magnetron sputtering, and the effect of Cr interlayer thickness on magnetic properties and interlayer exchange coupling was investigated. All the samples showed strong out-of-plane anisotropy but their hysteresis loops displayed two types ： singlephase and double-phase, indicating that interlayer exchange coupling and magnetic properties varied with the thickness of Cr interlayer. Both saturation field Hs and （1-Mr/Ms） curves indicated that interlayer exchange coupling oscillated between antiferromagnetic and ferromagnetic with a period of 1.6 nm, and the oscillation strength attenuated with increasing Cr interlayer thickness. After being annealed at 450℃ for 25 min, the hysteresis loops of all the samples became single-phase type and coercivity Hc decreased greatly, which could be attributed to the decrease of effective anisotropy in （Sm, TbFeCo） grains.     

晶界扩散Tb对烧结Nd-Fe-B组织与磁性能的影响

用磁控溅射法在烧结Nd-Fe-B磁体表面沉积Tb金属薄膜并进行晶界扩散处理,对比经不同热扩散温度及时间处理后的磁体组织和磁性能变化.结果 表明,925℃×10 h+500℃×2 h为最佳晶界扩散工艺,可将磁体矫顽力提高到1630.9 kA· m-1,较原始磁体提升50％,同时剩磁和磁能积无明显下降,磁体仍具有较高的退磁...     

Effects of magnetic annealing on crystallization and magnetic properties of Nd2Fe14B/α-Fe nanocomposite magnets

Crystallization and magnetic properties of Nd2Fe14B/α-Fe nanocomposite magnets have been investigated by annealing the as-spun ribbons with magnetic field.The crystallization process was accelerated by field annealing.The hysteresis loop became to be fat by magnetic annealing at 645 oC for 4 min,which was 690 oC for ribbons annealing without magnetic field.The relative content of α-Fe phase was increased from the results of XRD.The strength of the magnetic field had no obvious influence on the remanence and coercivity,but modified the squareness of hysteresis loop.     

Correlation of Magnetic Properties with Mechanical Properties of a High Tensile Grade Steel in Various Heat Treated Conditions

A high tensile grade steel was soaked for 30 min in the range of soaking temperatures 800–980 °C followed by cooling through air, oil, and water with the aim to produce a wide range of microstructure and mechanical properties. Microstructural modifications were observed through optical and scanning electron microscopy. Mechanical properties were evaluated through a micro Vicker’s hardness tester and Zwick made tensile testing machine. Magnetic properties such as coercivity, remanence and maximum induction were measured through a magnetic hysteresis loop (MHL) tester; MagStar for the correlation with mechanical properties for their non-destructive evaluation. The coercivity was correlated with the mechanical properties and was found to have a strong correlation due to the common reason of obstruction of dislocations and magnetic domain wall motion on the change in microstructural modifications such as volume fraction of phase, their finer and coarser form. The results clearly showed that by monitoring coercivity through MHL, mechanical properties of steels which altered due to microstructural modifications during heat treatment of the steels could be evaluated for their precise control.     

Microstructure and Magnetic Properties of Anisotropic Nd-Fe-B Magnets Fabricated by Single-Stage Hot Deformation

Anisotropic Nd-Fe-B magnets were fabricated by the single stage hot deformation (SSHD) method. The magnetic properties of the anisotropic Nd-Fe-B magnets are as follows: the maximum energy product is 234.7 kJ·m-3, remanence 1.16 T and coercivity 684.3 kA·m-1. A study of the relationship between microstructure and magnetic properties for the anisotropic Nd-Fe-B magnets was carried out. The results show that the grains of Nd2Fe14B have grown up preferentially along the direction perpendicular to the pressing direction.