【作者】 张志军；

【导师】 邵忠宝；

【作者基本信息】 东北大学 ， 物理化学， 2008， 硕士

【摘要】 第三代永磁材料钕铁硼,具有优异的磁性能和较高的磁能积,广泛的应用于微波技术,小型马达,磁盘驱动器,汽车音响,核磁共振技术等方面。由于磁体的构成是由铁和在稀土矿藏中丰度列第三位的钕组成,价格低廉,具有较高的性价比。但作为稀土元素的钕,标准氧化还原电位为-2.431V,是极度不稳定的非放射性元素之一,烧结NdFeB永磁体是多相粉末冶金材料,磁体表面和内部存在大量、细微的毛细孔,因此钕铁硼永磁体的耐蚀性很差,在材料应用方面受到了很大的限制。本实验采用磷化、钝化方法对钕铁硼表面进行处理以增强其耐蚀性,以铁系磷化和钝化方法为基础,对钕铁硼材料进行磷化、钝化处理。点滴实验、浸泡实验、失重率实验等方法检测磷化膜、钝化膜的耐腐蚀性,滤纸法检测膜层的孔隙率,采用扫描电子显微镜(SEM)和能谱分析对膜的形貌及元素分布进行研究。研究了磷酸二氢钠、磷酸、钼酸钠、硝酸锌、十二烷基硫酸钠、pH、温度、时间等对磷化膜质量的影响,确定了磷化液各成分的含量,采用正交实验设计方法优化出磷化液的组成及最佳实验条件：磷酸二氢钠50g/L、85%磷酸3mol/L、钼酸钠0.02g/L、pH=3、温度30℃、硝酸锌0.03g/L、十二烷基硫酸钠0.02g/L、时间为5min。制备出膜层均匀、致密、耐蚀性好的磷化膜,磷化膜中含有Mo、Zn、P、O等元素。对磷化后钕铁硼表面进行钝化处理,研究六价铬、三价铬及无铬钝化膜的耐蚀性,综合考虑环保及钝化膜性能确定钝化液的成分,正交实验优化出钝化液的组成及操作条件：钼酸钠20g/L,乙醇胺3.5g/L,pH=5,温度70℃,时间40s。经钝化处理后,膜层的表面的更加致密均匀,其耐蚀性比磷化膜的点滴时间增加一倍左右,孔隙率也明显下降。更多还原

【Abstract】 Due to its excellent performance of magnetism and comparatively high magnetic energy, the neodymium iron boron magnets, the third generation of permanent-magnet material developed in the early 1980s, have been widely used in many areas like microwave techniques, miniature motors, disc drives, car sound equipments and nuclear magnetic resonance. In terms of the richness in mineral resources, neodymium ranks at the third place as a rare earth metal. Therefore, magnet, composed of iron and neodymium, can be regarded as the ideal material low at price but good at quality. However, as a rare earth element neodymium’s standard redox potential was-2.431V and it was one of the most unstable non-radioactive elements. Polyphase powder metallurgical materials are used in sintering NdFeB permanent magnets. Lots of minute capillary bores do exist in the surface as well as inside the magnets. As a result, NdFeB performs poor corrosion resistance and has great limitation in its application.This experiment improved the corrosion resistance of neodymium iron boron magnets by means of phosphatization and passivation. The effects of solution-composing, processing con-dition on the phosphate layer and passivation layrer were also studied. The quality of phosphate layer and passivation layrer was tested by taking the experiments of dropping, porosity test, immerging experiment and weight-losing test. The best formulation of phosphatizing decided by orthogonal experiments were as following:50g/L Na2H2PO4·2H2O, 3mol/L85%H3PO4,0.02g/LNa2MoO4,0.03g/LZn(NO3)2·6H2O,0.02g/LCH3(CH2)10CH2OSO3N a. The paper compares the effects of three different passivation processes of Cr6+, Cr3+and none Cr on the performances of the layer. A conclusion that the corrosion resistance of none Cr processing was close to that of the passivation processing of Cr6+ was drawn. A deeper study of none Cr processing for passivation was done and the corresponding formulation was gained by orthogonal experiments:20g/L Na2MoO4·2H2O,3.5g/L NH2CH2CH2OH, pH=5.The shape and the distribution of the layer was observed through SEM and EDX. The results were as following:the phosphate layer and the passivation layer were symmetrical, without any obvious cracks. The composition of the layer are some elements such as Mo、P、Zn、O and so on.更多还原