钕铁硼磁性塑料及其注射成型的研究

通过对快淬钕铁硼(NdFeB)磁粉进行包覆，并用硅烷偶联剂KH550进行表面处理，以PA12做粘结剂，添加复配润滑剂及抗氧剂，在保证磁性能即高磁粉含量(91％)的条件下，很好地解决了NdFeB塑料粘结磁体流动性差及磁体在湿热环境下易氧化生锈的问题。并研究了注射成型NdFeB塑料粘结磁体的制备工艺、磁粉表面处理、磁粉含量、添加剂等因素对磁性能、加工性能、力学性能的影响。     

NdFeB磁粉表面电沉积包覆纳米金属层研究

在NdFeB磁粉表面包覆金属层是改变其性质的有效手段,但目前常用的化学沉积法、电化学沉积法与化学气相沉积法等都无法实现磁粉表面完整、牢固的包覆.探索新的NdFeB磁粉表面金属完整包覆技术具有重要的理论意义及应用价值.根据NdFeB片状磁粉在磁场下的磁化特征,设计了磁力搅拌流化床电解槽,利用电沉积实现磁粉表面的纳米金属层包覆.测量了磁粉包覆前后的磁性能和电极电位,测定了包覆不同厚度Cu对磁粉制成粘结磁体抗压强度的影响.结果表明,利用磁力搅拌流化床电沉积法可以实现NdFeB磁粉的完全包覆,包覆层厚度可以控制在纳米尺度.磁粉包覆后的磁性能和电极电位发生了明显改变,包覆铜样品的粘结磁体抗压强度明显提高.     

NdFeB塑料粘结磁体的研究进展

主要从粘结磁体的反应共混、耐腐蚀性、加工流变性能和动态性能4个方面论述NdFeB粘结磁体的最新研究进展.NdFeB粘结磁体既拥有NdFeB磁体较好的磁性能,又能表现出粘结剂(主要是塑料)固有的流变性能,是未来NdFeB磁体发展的方向.     

NdFeB磁粉表面抗氧化处理的研究

分别对NdFeB/PPS黏结磁体用的快淬NdFeB磁粉表面进行了无水磷酸化处理、钛酸酯处理、KH560处理以及无水磷酸化加KH560处理,研究了表面处理对磁粉抗氧化性能、表面形貌和晶态结构的影响.结果表明:四种表面处理工艺均能在磁粉表面形成防护层,并能有效地提高磁粉的抗氧化能力;无水磷酸化加KH560处理工艺对磁粉表面的包覆和抗氧化能力的提升效果最明显;表面处理没有改变磁粉本身结构.     

钕铁硼/聚苯乙烯粘结磁体的流变行为

文章以通用聚苯乙烯(GPPS)为粘结剂,采用毛细管流变仪研究了钕铁硼(NdFeB)与GPPS粘结磁体的流变行为。结果表明:NdFeB/GPPS体系为非牛顿型流动体系,遵从假塑性流体的流动规律;表观粘度随着剪切速率的增加而下降,随着磁粉含量的增加而上升;随着温度的升高,熔体的非牛顿指数呈增大的趋势,而随着磁粉含量的增加,熔体的非牛顿指数呈减小的趋势;粘流活化能随磁粉含量的增加而增大,随剪切应力的增加而降低,但变化均较小。     

钕铁硼磁体表面高耐蚀性锌铝涂层的制备及性能研究

通过浸涂-离心工艺在NdFeB磁体表面制备了ZnAl涂层,对涂层形貌、元素成分及织构进行了分析,研究了ZnAl/NdFeB磁体的极化曲线、高温老化和耐盐雾性能,测试了磁体涂覆后磁通量的变化。结果表明,NdFeB磁体表面制备的ZnAl涂层中Zn、Al以金属单质的形式存在,且以片状形态堆叠于磁体表面。涂覆后,磁体在3.5%NaCl溶液中的腐蚀电流密度降低了2个数量级。高温高湿老化400 h和中性盐雾试验720 h后,ZnAl/NdFeB磁体表面无变化。NdFeB磁体的磁通在涂覆后只降低了0.14%~0.26%,说明ZnAl涂层对NdFeB磁体的磁性能影响甚微。     

注射成型聚氯乙烯粘结磁体的研制

研究了偶联剂、磁粉用量以及加工工艺对注射成型聚氯乙烯（PVC）粘结磁体性能的影响.结果表明：当偶联剂用量为磁粉质量的1%时,磁体的综合性能最佳;偶联剂有一个临界胶束浓度（CMC）,当偶联剂用量大于CMC时,继续加入偶联剂效果不明显;磁粉预处理加工工艺,所制备的磁体性能较好;拉伸强度随磁粉用量增加而降低,磁性能在磁粉一定用量时达到最大值.     

磁粉并用对磁性丁腈橡胶胶料性能的影响

以铁氧体磁粉和钕铁硼(NdFeB)磁粉为磁性填料制备磁性丁腈橡胶(NBR)胶料,研究两种磁粉单用和并用对胶料性能的影响。结果表明,两种磁粉单用时,采用NdFeB磁粉制备的磁性NBR胶料的磁性能更优异。两种磁粉并用时,随着NdFeB磁粉用量的增大,胶料的硬度增大,拉伸强度和撕裂强度先增大后减小,在铁氧体磁粉/NdFeB磁粉并用比为700/10时达到最大;胶料的剩余磁感应强度和最大磁能积先增大后减小,在铁氧体磁粉/NdFeB磁粉并用比为700/30时最大,分别为0.197 T和7.3 kJ·m^-3。     

塑料粘接磁体注射成型技术的研究

阐述了塑料粘接磁体注射成型工艺、特点,着重分析了粘接剂、磁粉含量、磁场注塑机、模具结构等关键技术对塑料粘接磁体生产与使用的影响.     

添加剂对尼龙6铁氧体粘结磁体磁性能影响

系统研究了偶联剂和润滑剂等添加剂对注射成型尼龙6铁氧体粘结磁体磁性能的影响。结果表明,用偶联剂对磁粉进行表面处理,能够很好地改善树脂与磁粉的相容性,提高磁粉在树脂中的分散性,其中当偶联剂用量为2％（质量分数,下同）时,磁性能最好,剩磁（Br）、矫顽力（HcB）、内禀矫顽力（HcJ）以及最大磁能积（BHmax）分别达到0．23T,176．3kA／m,283．8kA／m,10．4kJ／m^3;润滑荆的使用能有效改善体系的流动性,降低共混过程中对磁粉结构的破坏,改善磁体的磁性,当润精剂用量为1％时,HcJ增加了9．3％。     

Tensile and heat resistance behavior of modified thermoplastic polyurethane elastomer in anisotropic neodymium-iron-born bonded magnet

The emergence of anisotropic neodymium-iron-boron (NdFeB)-bonded magnets with high energy density and freedom of shape design is effective in minimizing the dimensions and mass of electric motors. However, limitations in mechanical strength and heat resistance at elevated temperatures hinder their further application. To overcome these challenges, we present a novel approach to enhance the tensile strength and heat resistance of the NdFeB-bonded magnet involving the modification of thermoplastic polyurethane (TPU) through the melt-mixing method with a styrene–acrylonitrile-glycidyl methacrylate terpolymer (SAG) modifier and engineered TPU was then employed in fabricating NdFeB-bonded magnets via calendering molding. The microstructure of the magnets exhibited aligned NdFeB particles due to mechanical stress during calendering molding, which results in anisotropy. Interestingly, the magnetic properties of bonded magnets based on modified TPU remain almost the same compared to their unmodified counterparts, showcasing a maximum energy product of around 12 MGOe. The mechanical tests demonstrated a maximum 32.4% increase in the tensile strength of bonded magnets based on modified TPU. A progressive shift to a higher temperature (100 to 120°C) of magnet samples fractured occurs in the heat resistance measurement of the bonded magnets based on modified TPU, meaning improvement in heat resistance of NdFeB bonded magnets.     

永磁材料粘结剂的研究现状与应用

由于粘结的钕铁硼磁体具有优异的磁性能，其商业价值备受人们的关注。本文介绍了粘结钕铁硼磁体常用的粘结剂类型、研究现状及提高磁性能的方法，此外还介绍了这类粘结剂的应用及发展前景。     

Thermal stability of anisotropic bonded magnets prepared by additive manufacturing

In this research, anisotropic NdFeB + SmFeN hybrid and NdFeB bonded magnets are additively printed in a polyphenylene sulfide (PPS) polymer binder. Printed NdFeB + SmFeN PPS bonded magnets displayed excellent magnetic properties (B_r [remanence] = 6.9 kG [0.69 T], H_cj [coercivity] = 8.3 kOe [660 kA/m], and BH_max [energy product] = 9.9 MGOe [79 kJ/m³]) with superior corrosion resistance and thermal stability. The anisotropic NdFeB bonded magnet shows a high coercivity of 14.6 kOe (1162 kA/m) with a BH_max of 8.7 MGOe (69 kJ/m³). The coercivity and remanence temperature coefficients for NdFeB + SmFeN hybrid bonded magnets are −0.10%/K and −0.46%/K, and for NdFeB bonded magnets are −0.14%/K and −0.53%/K in the range of 300–400 K, indicating that the hybrid bonded magnets are thermally stable. The average flux aging loss for hybrid magnets was also determined to be very stable over 2000 h at 448 K (175°C) in air with 2.04% compared to that of NdFeB magnets with 3.62%.     

Synthesis and properties of magnets/polyethylene composites

Polyethylene‐based magnetic composites have been prepared by ethylene polymerization on the surface of NdFeB magnets, which is previously activated by ball milling with catalyst components. The level of magnets has been controlled by catalyst preparation and polymerization parameters such as Al/Ti ratio and polymerization temperature. The coertivity and the residual magnetizability were investigated. It was found that the magnetic properties of magnet powders are largely retained. In addition, in contrast to composites prepared by melt mixing, the adhesion force between magnets and polymer matrix is improved significantly and better mechanical properties are expected. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3412–3416, 1999     

Polymer bonded magnets. II. Effect of liquid crystal polymer and surface modification on magneto‐mechanical properties

We studied the effect of liquid crystal polymer (LCP) and surface modification of neodymium‐iron‐boron (Nd‐Fe‐B) magnetic alloy on the magneto‐mechanical behavior of poly (phenylene sulfide) (PPS) bonded Nd‐Fe‐B magnets to accelerate efforts to develop useful thermoplastic magnets with optimal performance. The results indicate that blending the LCP with PPS provides the required balance of properties for the targeted applications. These properties include superior magneto‐mechanical performance at elevated temperatures, minimal melt viscosity at optimal LCP volume fraction, high stiffness, and improved dimensional stability, making the thermoplastic magnets suitable for use at elevated temperatures and in chemically corrosive environments where commercial rare earth alloy magnets are not useable. Enhanced wetting of the magnetic Nd‐Fe‐B powders by the polymers, formation of reinforcing LCP domains, and interactions between the polymers and the magnetic powders are thought to be responsible for the beneficial function of the LCP and Nd‐Fe‐B surface modifier in the PPS bonded Nd‐Fe‐B magnets.     

烧结型钕铁硼的制备土艺及其发展趋势

钕铁硼磁体被称为第三代稀土永磁材料,烧结钕铁硼磁体是目前综合磁性能最高的永磁材料。介绍了烧结钕铁硼磁体先进生产工艺的特点及其相关理论,指出了目前国内烧结钕-铁-硼磁体存在的主要问题及今后的发展趋势。     

黏结磁性材料复合体系流动缺陷的研究

利用双料简毛细管流变仪，讨论了在高磁性粉末装载量下黏结磁性材料复合熔体流动缺陷问题。实验表明，黏结磁性材料复合熔体具有超高的流动黏度，在毛细管内受压流动时流动行为与管径尺寸相关。在小管径时容易产生“时黏时滑”、“压力振荡”等流动不稳定现象。分析认为，黏结磁性材料复合熔体体系是低量黏结剂和超高量的磁性粉末共混合体系，在小管径毛细管内受压流动时由于粉末粒子自由转动空间较小，产生剪切迁移行为不均匀，集聚在管壁处的低黏度物料量不稳定而引起管壁滑移等不稳定流动缺陷。