熔体温度对快淬法制备纳米晶复合Nd_(8.5)Fe_(77)Co_5Zr_3B_(6.5)合金微观结构和磁性能的影响

将Nd_(8.5)Fe_(77)Co_5Zr_3B_(6.5)(at%)合金熔化至不同温度后,以18 m/s的甩带速度快淬,对淬态条带进行了退火处理,分析了其微观结构和磁性能的变化。结果表明,熔体温度对淬态及其退火态合金的微观结构和磁性能可以产生重要影响,熔体温度为1210℃时制备的快淬条带由Nd_2Fe_(14)B相和部分非晶相组成,具有一定的硬磁性;随着快淬时熔体温度的升高,淬态条带中非晶相的质量分数逐渐增加,其磁性逐渐转变为软磁性。几种合金经退火处理后均由大量Nd_2Fe_(14)B相与少量软磁相组成,熔体温度较低的合金退火后其晶粒尺寸较小,磁性能较好。熔体温度为1210℃时制备的合金退火后磁性能最佳,内禀矫顽力Hci为559.2 kA/m,剩余磁化强度Br为0.98 T,最大磁能积(BH)_(max)为127.8 kJ/m~3。     

工艺参数对钕铁硼化学镀Ni-Mo-P/PTFE复合镀层耐蚀性的影响

采用化学镀方法在钕铁硼表面制备Ni-Mo-P/PTFE复合镀层,并运用正交实验法考察PTFE乳液浓度、镀液温度、化学镀时间和搅拌速率对Ni-Mo-P/PTFE复合镀层腐蚀速率的影响.结果表明:Ni-Mo-P/PTFE复合镀层的腐蚀速率随着镀液温度升高、PTFE乳液浓度增加和搅拌速率提高都呈先减小后增大的趋势,而随着化学...     

高效永磁同步电动机的技术开发和应用

高效率电动机的开发和应用,在世界各国都引起了重视.能源部门把推广使用高效率电动机作为国家节约电能的重要措施.利用高磁场永磁材料钕铁硼装入电动机转子中,成为高效永磁同步电动机,能提高效率,节能效果显著,而这仅仅是钕铁硼在电机技术应用中种的一种.     

Hot deformed anisotropic nanocrystalline NdFeB based magnets prepared from spark plasma sintered melt spun powders

Anisotropic magnets were prepared by spark plasma sintering (SPS) followed by hot deformation (HD) using melt-spun powders as the starting material. Good magnetic properties with the remanence J_r > 1.32 T and maximum of energy product (BH)_max > 303 kJ/m³ have been obtained. The microstructure evolution during HD and its influence on the magnetic properties were investigated. The fine grain zone and coarse grain zone formed in the SPS showed different deformation behaviors. The microstructure also had an important effect on the temperature coefficients of coercivity. A strong domain-wall pinning model was valid to interpret the coercivity mechanism of the HDed magnets. The increase of stray field and weakening of domain-wall pinning effects were the main reasons of the decrease of the coercivity with increasing the compression ratio. The influences of non-uniform plastic deformation on the microstructure and magnetic properties were investigated. The polarization characteristics of HDed magnets were demonstrated. It was found out that the HDed magnets had better corrosion resistance than the counterpart sintered magnet.     

Kinetics of mechanically activated disproportionation of NdFeB alloy during reactive milling in hydrogen: Experimental studies,mechanism and modelling

The process of solid–gas reaction milling in hydrogen was applied to achieve full disproportionation and microstructure nanocrystallization of NdFeB alloy. The NdFeB alloy was disproportionated by room-temperature reactive ball milling in hydrogen, with the mechanical energy serving as the driving force. The reaction progress during milling was examined by hydrogen absorption measurement, and the corresponding microstructure change was characterized by X-ray diffraction (XRD). The mechanism of mechanically activated hydrogenation–disproportionation reaction of NdFeB alloy was investigated. The disproportionation kinetics of an as-cast Nd₁₆Fe₇₆B₈ (atomic ratio) alloy during reaction milling was experimentally studied by in-situ monitoring of the hydrogen absorbed by the alloy in the vial. On the assumption that the impact energy to activate the reaction plays a role analogous to that of the thermal energy for the conventional thermally activated process, a theoretical model for the kinetics of the mechanically assisted disproportionation was proposed. By fitting the experimental data with the theoretical model, the kinetic equation and the energy utilization efficiency under different milling conditions were obtained. The effect of milling parameters and hydrogen pressure on the disproportionation kinetics was evaluated and the underlying mechanisms were discussed by referring to the mechanical energy input intensity and the Gibbs free energy change for the reaction.     

NdFeB永磁薄膜的制备方法及其研究进展

综述了NdFeB永磁薄膜的制备方法和原理;介绍了NdFeB永磁薄膜的研究进展;指出了NdFeB永磁薄膜存在的问题;并对NdFeB永磁薄膜未来的发展方向及应用前景进行了展望。     

NdFeB永磁材料的分类及其应用

论述了NdFeB永磁材料的分类,介绍了NdFeB永磁材料的应用,并对永磁材料的应用前景进行了展望。     

纳米复合NdFeB永磁材料研究的新进展

综述了NdFeB纳米晶双相复合永磁材料的最新研究进展,介绍了其磁性能的研究现状,分析了其研究的发展趋势。     

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.     

钕铁硼磁体磁性的近似普适规律的研究

为了探讨钕铁硼磁体磁性的近似普适规律,把不同性能钕铁硼磁体在各温度下的退磁曲线加以归一化,这使退磁曲线显示出近似的普适性,而且其内禀矫顽力及剩磁随温度变化的规律也相似,据此导出钕铁硼磁体在各温度下退磁曲线的近似普适数学表达式,由该公式计算得到的各温度下的退磁曲线与实测曲线基本吻合.