注射成型粘结NdFeB磁体的研发进展

简述注射成型粘结NdFeB磁体的制备工艺，分析了磁粉、粘结剂、取向磁场和工艺参数对注射成型粘结NdFeB磁体磁性能的影响以及该磁体的性能状况，并概述了粘结NdFeB磁体的产业发展及其应用领域，最后提出注射成型粘结NdFeB磁体的开发重点。     

注射成形法制取各向异性粘结NdFeB磁体的研究

研究了磁粉粒度、取向磁场强度、取向时间及装载量对注射成形各向异性粘结NdFeB磁体性能的影响，并分析了其原因。结果表明：NdFeB磁粉粒径太粉末或太细均不利于磁体性能的提高，其最佳粒径范围是60μm～100μm；随着取向磁场强度的逐渐增加，磁体剩磁Br及矫顽力bHc增加较大但其内禀矫顽固力jHc则基本不变；与此同时为保证磁粉取向完全，磁场取向时间必须大于5g。在此基础上，通过实验找出了最佳的装载量并制备出最大磁能积（BH）max和抗压强度σb分别为99kJ/m^3及125MPa的高性能注射成形各向异性粘结NdFeB磁体。     

表面处理对磁粉抗氧化性及注射成形粘结磁体的影响

对NdFeB磁粉进行了不同表面处理,研究了表面处理对磁粉抗氧化性、喂料流动性及粘结磁体性能的影响规律.结果表明:(1)NdFeB磁粉经改性处理后,粉末在300℃及500℃的氧化增重率大大降低;而且采用先磷酸后硅烷的复合处理工艺要比单一的硅烷处理或单一的磷酸处理效果更好;(2)KH550硅烷耦联剂能有效地改善NdFeB磁粉与尼龙粘结剂相容性,相应制得的喂料流动性要好于未改性磁粉,而且能相对提高NdFeB磁粉的装载量,使得最大装载量(体积分数)达到67%;(3)通过对磁粉表面改性,改善了磁粉与塑料粘结剂的界面特性,不仅提高了注射成形粘结磁体的磁学及力学性能,而且改善了粘结磁体的耐热性能.     

磁粉粒度对注射成形粘结NdFeB磁体性能的影响

研究磁粉粒度对注射成形粘结NdFeB磁体性能的影响。结果表明：随着磁粉粒度减小,喂料粘度值升高,粘流指数n值降低,其注射工艺性能更好;制备粘结磁体的抗压强度更高,但其不可逆磁损失也增大。NdFeB磁粉粒度太粗或太细均不利于磁体性能的提高,其最佳粒径范围是80-100μm;通过粒度级配可以降低喂料粘度值或提高临界装载量,在此基础上制备高性能的各向异性粘结NdFeB磁体,其Br、iHc、（BH）max及σbb分别为878 mT、1 212.3 kA/m、128 kJ/m^3及73 MPa。     

温压钕铁硼粘结磁体制备技术的研究

采用温压工艺制备了钕铁硼粘结磁体,研究了温压压力、温压温度、粘结剂种类及含量对磁体磁性能的影响,以及温压工艺对钕铁硼粘结磁体氧含量的影响.利用Nd2Fe14B/a-Fe系双相纳米晶磁粉为原料,在200℃下,采用12MPa的压力,获得性能最佳的磁体,其密度为6.43 g/cm3,磁性能为:Br=0.808 T,Hcb=461 kA/m,Hci=623 kA/m,(BH)max=101 kJ/m3.     

HDDR各向异性NdFeB研究进展

HDDR工艺目前已经成为了制备各向异性NdFeB磁粉的最主要方法.总结了本世纪以来HDDR法制备各向异性磁粉的各向异性成因、HDDR处理工艺、添加元素等方面取得的进展,以及磁粉粒度、粘结剂选择、成型方法对磁体性能的影响.     

不同基体粘结NdFeB磁体的磁性能及稳定性研究

通过磁粉表面处理及在NdFeB磁粉中添加不同比例的粘结剂,制备了金属基和塑料基两种粘结磁体,研究了不同基体磁体的稳定性和磁性能,从断口SEM照片及结合理论分析可得出结论磁粉的表面处理可以改善磁体的稳定性及磁性能,通过磁性能测试及对比和退磁率的测量可以看出塑料基磁体的磁性能低于金属基磁体,但其稳定性却显著提高,塑料基磁体的使用温度可达150～180 ℃.     

注射成形法制备高性能粘结NdFeB磁体

利用新研制的磁场注射成形机,研究了磁粉表面改性处理、取向磁场强度及装载量对注射成形各向异性粘结NdFeB磁体性能的影响.结果表明:磁粉经硅烷改性后,可在其表面形成一层抗氧化膜,其氧化质量增加率由2.3%下降至0.35%,相应制得的粘结磁体最大磁能积及抗压强度分别提高了17.8%和35.9%;而随着取向磁场强度的增加,磁体剩磁Br及矫顽力bHc均有较大幅度的增加,但其内禀矫顽力iHc则基本不变;同时,通过实验得出了最佳的装载量为65%(体积分数),并制备了最大磁能积(BH)max及抗压强度σbb分别为99 KJ/m3和125 MPa的注射成形粘结NdFeB磁体.     

粘结剂含量对粘结NdFeB磁体力学性能和磁性能的影响

粘结剂作为粘结NdFeB磁体制备过程中的重要组成部分,其作用是提高磁粉颗粒的流动性和粘结强度,保证产品的力学性能和磁性能的稳定。采用理论与实验相结合的方法,研究了粘结剂含量对粘结NdFeB磁体力学性能和磁性能的影响。在此基础上,制备了高性能粘结NdFeB磁体。利用扫描电子显微镜（SEM）对磁体的结构和形貌进行了表征。在NIM-200C磁滞回线仪和电子万能试验机（AG-X plus）上分别测定了环形粘结NdFeB磁体（RSM）的磁性能和力学性能。结果表明,当粘结剂含量为3%（质量分数）时,粘结NdFeB磁体密度最高（5.59 g/cm³）,抗压强度最高（159 MPa）,磁性能最佳。     

磁粉粒度分布和抗氧化剂对注射成型NdFeB粘结磁体性能的影响

本文研究了磁粉的粒度分布以及不同抗氧化剂的加入对注射成型NdFeB粘结磁体密度和磁性能的影响。结果表明，磁粉的粒度分布影响熔体的粘度，适当的粒度分布可以提高磁粉的松装密度和磁体的密度，获得高性能的粘结磁体；抗氧化剂的加入，很好地解决了NdFeB粘结磁体在湿热环境下易氧化生锈的问题，大大提高了磁体的抗氧化性能。     

放电等离子烧结-热变形各向异性Nd-Fe-B磁体的微观组织及磁性能

采用放电等离子烧结及后续热变形技术制备各向异性Nd-Fe-B磁体,研究烧结温度对放电等离子烧结Nd-Fe-B磁体微观组织和磁性能的影响。随着烧结温度在650~900°C范围内的升高,烧结态Nd-Fe-B磁体的剩磁、内禀矫顽力及最大磁能积呈现先升后降的趋势。在800°C下烧结所获得磁体的磁性能最佳。随后,对800°C烧结后具有最佳磁性能的磁体采用放电等离子烧结技术进行后续热变形处理。与初始吸氢-歧化-脱氢-再复合粉末和烧结态磁体相比,热变形磁体拥有更显著的各向异性和更好的磁性能。当热变形温度为800°C且压缩比为50%时,热变形磁体中的Nd2Fe14B晶粒呈扁平片状且不发生异常长大;磁体沿热压方向具有最佳的磁性能：Br、Hcj和（BH）max分别为1.16 T、449 k A/m和178 k J/m3。     

热变形温度对纳米晶Nd-Fe-B磁体性能的影响

为了研究纳米晶Nd-Fe-B磁体的热变形机理,在不同温度下对快淬粉进行热压热变形处理.通过分析不同温度下热变形过程中应力和磁体应变的变化,以及磁性能和SEM测试,研究了温度对热变形磁体性能和微观结构的影响,分析了热变形过程的热变形机理.结果表明,纳米晶磁体存在最佳的热压温度和热变形温度.当热压温度为550℃,热变形温度...     

Magnetic properties and thermal stability of anisotropic bonded Nd-Fe-B magnets by warm compaction

Anisotropic bonded magnets were prepared by warm compaction using anisotropic Nd-Fe-B powder. The forming process, magnetic properties, and temperature stability were studied. The results indicate that the optimal temperature of the process, which was decided by the viscosity of the binders, was 110℃. With increasing pressure, the density of the magnets increased. When the pressure was above 700 MPa, the powder particles were destroyed and the magnetic properties decreased. The magnetic properties of the anisotropic bonded magnets were as follows: remanence Br = 0.98 T, intrinsic coercivity iHc=1361 kA/m, and maximum energy product BHmax = 166 kJ/m3. The magnets had excellent thermal stability because of the high coercivity and good squareness of demagnetization curves. The flux density of the magnets was 35% higher than that of isotropic bonded Nd-Fe-B magnets at 120℃ for 1000 h. The flux density of the bonded magnets showed little change with regard to temperature.     

Epoxy resin effect on anisotropic Nd-Fe-B rubber-bonded magnets performance

A novel anisotropic Nd-Fe-B flexible bonded magnet with epoxy resin lubricant was prepared by the two-step method to enhance its performance. Temperature characteristics of epoxy resin and its effect on magnetic properties and preparation of anisotropic Nd-Fe-B flexible bonded magnets were investigated and optimized. DOA of aligned flexible bonded magnets with epoxy resin lubricant increases significantly due to epoxy resin lower viscosity and subsequent better powder particles lubrication at a certain aligning temperature. Meanwhile, H_irr decreases sharply due to improved oxidation resistance of epoxy resin fully encapsulating magnetic powder during magnetic alignment process. Utilizing 1 wt% optimized encapsulating epoxy resin and heating unaligned flexible bonded magnets to 80 °C for 30 min during magnetic alignment resulted in the largest Δ(BH)_max and ΔDOA. Δ(BH)_max increased to over 126% along with ΔDOA increase to over 75%, much higher compared with unaligned flexible bonded magnets prepared exclusively by calendering.     

Statistical model of magnetization reversal in Nd-Fe-B sintered magnets

Statistical model of magnetization reversal was used to simulate the magnetization reversal behavior in the sintered Nd-Fe-B magnets with double grain-size distributions due to the abnormal grain growth (AGG). The magnetic properties and mechanical properties due to the formation of AGG grains in Nd-Fe-B sintered magnets were tested. The results show that the magnetic properties, especially the rectangularity were severely deteriorated after the formation of the AGG grains and a step was shown on the demagnetization curve, and the occurrence of AGG mayaccount for the poor rectangularity and existence of the step on demagnetization curve according to the statistical model of magnetization reversal. The fracture toughness and bending strength are lowered because of the stress concentration in the AGG grains. The SEM images show that the formation of AGG grains is caused by the solid sintering due to the absence of RE-rich phase. Statistical model of magnetization reversal can qualitative by explain the dependence of the magnetization reversal behavior on the grain size in the Nd-Fe-B sintered magnets.     

烧结钕铁硼添加合金元素的研究进展

磁性能优越的烧结钕铁硼永磁材料已成为永磁产业的支柱.过去的二十多年里钕铁硼已经在硬盘驱动器的VCM、电动机、信号发生器、手机和MRI等多种器件中得到广泛应用.在未来,由于汽车和电子应用领域对节能电动机的需求,使得电动机市场有望进一步扩展.因此,研究团队致力于钕铁硼磁性能的提高,从而推进电动机市场的快速发展.本文对近些年...     

Magnetic microstructure and coercivity mechanism of high performance Nd-Fe-B magnets

Magnetic microstructure of high performance Nd-Fe-B magnets was investigated by using magnetic force microscopy. The correlation between magnetic microstructure and coercivity for high performance Nd-Fe-B magnets was studied. It is found that the magnets with different coercivity mechanism take on different microstructures and magnetism. Moreover, the magnetic microstructures of high performance permanent magnets can be explained by the starting field theory model.     

添加稀土氢化物对烧结Nd-Fe-B磁体强度的影响

研究了添加镨氢化物对烧结Nd-Fe-B磁体磁性能、微观结构和抗弯强度的影响。结果表明：添加镨氢化物可以有效提高磁体的抗弯强度，同时对磁体的矫顽力有一定提高。SEM微观形貌观察表明：添加镨氢化物可有效改善磁体的微观结构。有效提高了主相晶粒原子间扩散速度，从而改变了磁体的微观结构和提高了烧结磁体的抗弯强度。     

化学法合成Nd-Fe-B磁性纳米粒子的评述—微结构与磁性能

高性能钕铁硼磁体广泛应用于各个领域。当Nd-Fe-B磁粉的晶粒尺寸接近单畴临界尺寸时,其矫顽力最大。化学法制备Nd-Fe-B磁粉可以很好地控制磁粉的微观结构和晶粒尺寸。同时,金属盐作为前驱体和简单的工艺流程可以降低成本和能源损耗。介绍了几种化学法制备Nd-Fe-B磁粉,分别为溶胶凝胶法、自燃烧法、微波辅助燃烧法、热分解法和机械化学法。研究了这些化学法的制备工艺和反应机理。最后,对不同化学方法合成的Nd-Fe-B磁粉的显微组织进行了对比分析,阐述了微观组织与磁性能之间的联系,展望了磁性材料未来的发展趋势。     

Fracture Strength and Surface Magnetic Flux Uniformity in an Isotropic Polymer-Bonded Ring-Shaped Nd-Fe-B Magnet

Ring-shaped (RS) polymer-bonded magnets were produced from a mixture of an isotropic nanocrystalline Nd-Fe-B powder with a nominal composition of 59.8 wt.% Fe, 29 wt.% Nd, 5 wt.% Zr, 4.8 wt.% Co and 1.4 wt.% B and a variety of epoxy resins as binders, using a compaction-molding technique. The morphology and average particle size of the powders are determined by an SEM. The magnetic properties of the magnets were measured using a permeameter. Magnetic flux on the surface of the magnets was determined by a Gauss meter. The mechanical properties of the RS specimens were determined using a tensile fracture strength (FS) test. The effects of polymer type and amount, hardener amount, applied pressing pressure and curing temperature and time on FS were investigated. The experimental results showed that at optimal conditions of 8 wt.% solid epoxy, 3.5 wt.% solid hardener, a pressing pressure of 900 MPa and a curing time of 8 h at 170 °C, a maximum tensile strength of?~?36 MPa was achieved. Surface magnetic flux uniformity in optimal mechanical conditions was also found to be optimum at around?±?40 G, which is one of the best flux uniformities in bonded magnets.