烧结NdFeB永磁体化学镀镍前的酸洗工艺研究

对NdFeB永磁体化学镀镍前的不同酸洗处理工艺进行了试验,并对不同酸洗工艺获得的镀层结合力和耐蚀性进行了测定比较.结果表明,经硝酸与氢氟酸混合酸液酸洗后的试样具有较平整的表面,在此表面上得到的镀层经高压锅及锉刀试验证明具有良好的结合力,浸泡试验检测表明其具优良有的耐蚀性.     

4种涂层对NdFeB磁体耐腐蚀性能和磁性能的影响

NdFeB耐蚀性能差,对其实施涂层保护可以提高其耐蚀性能,但又影响到磁性能.对比研究了Ni,Zn,环氧树脂,PARYLENE-C涂层对NdFeB磁体在3种溶液中对磁性能的影响.结果表明:在酸、碱、盐环境中,高分子材料涂层对磁体的保护效果最好,环氧树脂涂层相对差些,Ni涂层次之,Zn涂层最差;Ni涂层和Zn涂层对样品的磁性能影响不大,但环氧树脂涂层使其BHmax减少了12.66 kJ/m3;高分子材料涂层使其BHmax减少了31.68 kJ/m3,且使Hcj增加了41.38 kA/m.因此,为保证其性能和正常使用,应根据不同的使用环境来选择适当的涂层.     

Intergrain Interaction, Coercivity and Henkel Plot for NdFeB Magnets

For both sintered and nanocomposite NdFeB magnets, deltaM(H) of the Henkel plot increases from zero, and reaches a peak, then decreases and changes to the negative values with increasing applied field. This shows that the intergrain interaction changes from the exchange-coup ling type into the magnetostatic interaction type. The magnetic field corresponding to the peak of deltaM(H) is slightly smaller than the coercivity of magnet. The peak of deltaM(H) for aligned sintered magnet is greater than that for misaligned magnet. deltaM(H) peak of the nanocomposite NdFeB magnets increases with decreasing grain sizes. It indicates that the effect of alignment field on the properties of magnet is similar to that of exchange-coupling interaction.     

Preparation of Ni–Co alloy coating on sintered NdFeB magnet by potentiodynamic electrodeposition

A protective Ni–Co alloy coating was successfully prepared on sintered neodymium–iron–boron (NdFeB) magnet via potentiodynamic electrodeposition in this paper. The microstructure and surface morphology analysis of Ni–Co alloy coating showed that the surface morphologies were quite compact and more uniform than that prepared by direct current (DC) electrodeposition; significantly, the chemical composition analysis indicated that the content of Co in the alloy coatings amounted to 33–34?wt-%. Potentiodynamic polarisation and long term immersion test results revealed that the Ni–Co alloy coating could supply excellent corrosion protection for NdFeB substrate in 3.5?wt-% NaCl solution. Overall, the Ni–Co alloy coating with higher Co content prepared by potentiodynamic electrodeposition exhibited better corrosion protection for sintered NdFeB magnet compared with that prepared by DC electrodeposition.     

钕铁硼永磁合金的晶粒相互作用和矫顽力

钕铁硼永磁合金的矫顽力由单个晶粒的矫顽力和晶粒之间的相互作用决定。晶粒的矫顽力及其相互作用与晶粒取向有关。按照不同的矫顽力机制,晶粒的矫顽力及其角度关系有不同的表达式。晶粒相互作用可分为长程静磁相互作用和近邻晶粒的交换耦合相互作用。烧结磁体的交换作用影响很小,静磁相互作用影响较大,使晶粒混乱取向磁体的矫矫顽力大于晶粒理想取向磁体的矫顽力。综合考虑单个晶粒的矫顽力和不同取向晶粒之间的相互作用的影响。     

添加润滑剂对烧结钕铁硼磁体性能的影响

研究了烧结钕铁硼永磁材料的粉末流动性及添加润滑剂对粉末流动性与磁体取向度和磁性能的影响.结果表明:影响松装状态磁粉流动性的主要因素是粉末颗粒团聚,影响密实磁粉流动性的主要因素是颗粒间的摩擦力.添加适量的润滑剂可以防止粉末颗粒团聚、明显地减小摩擦力,改善粉末流动性,提高磁体的取向度、剩磁与磁能积.采用添加润滑剂和橡皮模等静压制成型工艺,批量生产的烧结钕铁硼磁体性能达到:Br=1.457 T,jHc=1148 kA/m(14.43 kOe),(BH)max=408 kJ/m3(51.3 MGOe).     

放电等离子烧结NdFeB磁体的氧化和腐蚀行为

采用放电等离子烧结技术制备了新型NdFeB磁体,研究了NdFeB磁体在湿热环境下的氧化行为和在电解质溶液中的电化学特性.在扫描电子显微镜下分析了磁体的显微组织结构和成分.结果表明,与传统烧结NdFeB磁体相比,新型磁体的显微组织特征为:主相Nd2Fe14B晶粒细小、均匀,富钕相在主相晶粒边界上分布较少,主要集中在三角晶界处.这种组织结构有效抑制了磁体沿富钕相发生的晶间腐蚀的过程,使磁体具有良好的耐腐蚀性能.     

放电等离子烧结NdFeB磁体的磁化特征

利用放电等离子烧结技术(SPS)制备烧结钕铁硼磁体SPS NdFeB。为了更好地理解SPS Nd-FeB磁体的磁硬化机理,利用振动样品磁强计研究了SPS NdFeB磁体在室温下的磁化和反磁化过程。结果表明,在强度为800kA/m的较低外加磁场和强度为1760kA/m的较高外加磁场下的磁化特征明显不同,前者可称为形核控制模式,后者则为钉扎控制模式。比较样品的磁化过程和反磁化过程的曲线,发现样品的矫顽力大小等于样品磁化过程钉扎场的大小。     

Properties improvement and structural optimization of sintered NdFeB magnets by non-rare earth compound grain boundary diffusion

Grain boundary diffusion using rare earth (RE)-containing compounds has recently become an effective approach for improving the coercivity and reducing the heavy RE content in sintered NdFeB magnets. Here we report the enhancement of magnetic properties and corrosion resistance of NdFeB magnets by a non-RE compound diffusion process. The Dy-free sintered NdFeB magnets were coated with an MgO layer by magnetron sputtering, followed by solid diffusion heat treatment. With the successful diffusion of MgO into the magnet, the coercivity increasing from 1094 to 1170 kA/m and the maximum energy product increasing from 240 to 261 kJ/m³, together with the enhanced temperature stability and corrosion resistance, have been demonstrated. The underlying mechanisms for these enhancements have been analyzed. Microstructural investigations show that MgO entered mainly into the intergranular regions and modified the composition and structure of the grain boundary phase. The intergranular Nd–O–Fe–Mg phases observed in the MgO diffused magnet contribute to the improved performance. The current non-RE compound grain boundary diffusion process has significance in further minimizing the use of rare earth (RE).     

Precipitation in NdFeB-type magnet materials

The microstructure of sintered magnets and melt-spun samples made from Nb-containing (Nd,Dy)FeB material has been investigated using transmission and scanning electron microscopy, X-ray microanalysis and thermogravimetric analysis. Comparison of the sintered specimens with NdDyFeB and NdFeB magnets revealed the existence of two additional phases. One of these is an Fe2Nb Laves compound. The second additional phase takes the form of small Nb-containing coherent precipitates within the main Nd2Fe14B grains. In the sintered magnet these particles ranged in size from 20-50 nm. Melt-spun ribbon contained a dispersion of smaller inclusions, typically 5-10 nm in diameter. The presence of these precipitates may be related to the enhanced coercivity found in the magnet and melt-spun samples.     

烧结钕铁硼永磁体矫顽力理论及其影响

综述了建立在不同缺陷模型基础上的烧结钕铁硼永磁体矫顽力的成核理论、热激活理论、钉扎理论和发动场理论等;简述了添加合金元素对钕铁硼磁体矫顽力的影响,通常少量多加合金元素有利于其整体性能的提高;详述了钕铁硼磁体的生产工艺,如熔炼、制粉、成型、烧结回火等对其矫顽力的影响;提出了提高烧结钕铁硼永磁矫顽力的有效途径和未来其生产研究的主要方向.     

高性能的尼龙1010 粘结NdFeB 永磁材料的制备

研究热塑性树脂尼龙1010 作粘结剂制备高密度粘结N dFeB 永磁材料的工艺及其对粘结 永磁性能的影响。结果表明: 快淬N dFeB 磁粉的表面状态、混炼工艺及热压成型温度、压力及时间 明显影响着尼龙1010 粘结N dFeB 永磁的性能。只有经抗氧化处理的快淬N dFeB 永磁粉, 在双辊 混炼机上, 当尼龙1010 处于半熔融状态时, 在适当短的时间混合均匀后, 才可热压制成高密度的 粘结N dFeB 永磁材料。      

DyAl薄膜真空扩散渗及时效处理对烧结NdFeB磁性和耐蚀性的影响

采用直流磁控溅射的方法,在烧结NdFeB磁体表面制备DyAl合金薄膜,对镀膜样品进行了真空扩散渗(800℃×6h)和时效处理(900℃×2.5h+490℃×5h),研究其耐热性和耐蚀性。经过真空扩散渗及时效处理,磁体的内禀矫顽力Hcj提高14.7%,磁体PCT失重从26.155 mg/cm2降低为1.731 mg/cm2,动态极化曲线显示Dy、Al元素的扩散改变了基体的腐蚀电位和腐蚀电流。结果表明,DyAl薄膜扩散进入NdFeB表层基体中,提高了磁体的耐热性和耐蚀性。     

The properties of aluminium coating on sintered NdFeB by DC magnetron sputtering

Pure aluminium coating was deposited on sintered NdFeB magnets by direct current (DC) magnetron sputtering to improve the corrosion resistance. The corrosion behaviour of sintered NdFeB coated with aluminium was characterized by potentiodynamic polarization measurement. The adhesive strength between the aluminium coating and the sintered NdFeB was characterised by vertical tensile test and high-low temperature shock test. The influence of the coating on the magnetic properties of the sintered NdFeB was also characterised. It was found that the aluminium coating can improve the corrosion resistance of the sintered NdFeB evidently. The aluminium coating was well adhesive with the substrate and did not deteriorate the magnetic properties of the sintered NdFeB magnets. These two characters may overcome the disadvantages of NiCuNi coating which is usually electroplated on NdFeB in industry.     

不同表面处理工艺对快淬NdFeB永磁粉抗氧化性和磁性能影响

本文对快淬ＮｄＦｅＢ永磁粉分别采用化学镀镍,重铬酸盐钝化处理,重铬酸盐钝化还原处理以及硅烷偶联处理的重铬酸盐钝化－还原／硅烷复合处理等工艺进行了表面包覆,研究了表面包覆处理前后的快淬ＮｄＦｅＢ磁粉的抗氧化特性,并初步比较了包覆处理前后的快府ＮｄＦｅＢ磁粉制成粘结ＮｄＦｅＢ磁体的磁性能,结果表明上述工艺方法的均能改善ＮｄＦｅＢ磁粉的抗氧化性,其中以重铬酸盐钝化－还原／硅烷偶联处理形成的包覆层的抗氧化     

塑料粘结钕铁硼的温度稳定性研究

本文研究国产快淬钕铁硼粘结磁体的温度稳定性，包括１００℃长时间时效，短时不同温度时效及温度循环对粘结钕铁硼磁损失的影响并同美国ＭＱＰ－Ｂ磁体的温度稳定性进行了比较，结果表明国产Ｍ４磁粉比ＭＱＰ－Ｂ粉具有较好的温度稳定性，Ｍ２磁粉温度稳定性较差，另外通过预先稳定化处理的方法可改善粘结钕铁硼的温度稳定性。     

HDDR各向异性粘结NdFeB研究

本文在回顾粘结ＮｄＦｅＢ发展历程的基础上,综述了ＨＤＤＲ各向异性粘结ＮｄＦｅＢ研究现状,以及ＨＤＤＲ工艺在其它稀土永磁制备中的应用。     

Structure, corrosion, and hardness properties of Ti/Al multilayers coated on NdFeB by magnetron sputtering

Ti/Al multilayers deposited on sintered NdFeB magnets by direct current magnetron sputtering with ion-beam assistance were studied in this report. Ti layers with a hexagonal close packed structure were obtained in the Ti/Al multilayers. The columnar structure growth of Al layers was successfully interrupted by the intercalated Ti layers. The Ti/Al multilayers showed more compact and uniform surfaces than the Al single layer. The corrosion current densities of the sintered NdFeB magnets coated with Ti/Al multilayers were much lower than that of the Al single layer. The Ti/Al multilayers also presented improved hardness.     

磁性高分子粘结钕铁硼的性能

研究了二茂金属高分子铁磁粉(O PM ) 与快淬钕铁硼磁粉复合制成的一种新的粘结永磁复合材料的性能, 并与非磁性高分子粘结钕铁硼的性能进行了比较。结果表明, 磁性高分子的含量降低, 磁性高分子粘结钕铁硼永磁材料的最大磁能积(BH )_m、剩磁B_r、矫顽力Hb_c升高, 内禀矫力H j_c略为下降; 但在含相同体积分数磁粉情况下, 磁性高分子粘结N dFeB 的磁性能比非磁性的高分子粘结N dFeB 的磁性能高, 其温度稳定性也几乎相同。      

环状永磁体表面径向磁通密度分布的模拟计算

利用AutoCAD软件构建四极磁环的三维模型,采用Ansoft Maxwell软件的有限元分析法对各向异性粘结钕铁硼(NdFeB)四极环状磁体表面径向磁通密度分布进行数值模拟。研究了各向异性粘结NdFeB永磁材料的剩磁B_r和矫顽力H_(cb)及环状磁体的高度、厚度和内外径,对环状磁体表面径向磁通密度与磁特性的影响。结果表明,环状磁体表面径向磁通密度与NdFeB材料的矫顽力H_(cb)及磁体的厚度密切相关,而NdFeB材料的剩磁B_r及磁体的高度对其影响较小。