Preparation And Properties Of Corrosion Resistant Films Coated On NdFeB Magnet

SiC monolayer thin films, SiC/Al bilayer thin films, SiC/AlN bilayer thin films and (SiC/AlN)2 multilayer thin films were deposited on the sintered NdFeB magnet by magnetron sputtering method. Samples coated with films were characterized by XRD, AFM, FESEM, electrochemical workstation and ultra-high coercivity permanent magnet pulse tester for structures and properties. At the same time, the corrosion resistance of NdFeB sample deposited different films was researched in three types of corrosion solutions such as acid, alkali and salt solutions. What has mainly investigated in this paper is present as follows:The first chapter discusses the history, processing technology, composition structure, three types of corrosion mechanism as well as the method to improve the corrosion resistance of NdFeB permanent magnet materials. In addition, the research status, main content and innovation point are also introduced.The second chapter lists the experiment equipment and materials, working principle of magnetron sputtering equipment and formation processes of films. At the same time there are some simple introductions to all kinds of characterization testing instruments such as X-ray diffractometer (XRD), atomic force microscope (AFM), field emission scanning electron microscopy (FESEM), and Shanghai Chenhua electrochemica workstation and other testing instruments.The third chapter studies the surface of NdFeB magnets that deposited different thickness of SiC films, which morphology and structure of the films are analyzed by FESEM. In addition, we compare the anti-corrosion properties of sintered NdFeB samples coated with different thickness films in 0.62 mol/L NaCl,6.25 mol/L NaOH and 0.10 mol/L H2SO4 solutions respectively. The results show that the corrosion resistance of coated NdFeB sample is better than that uncoatde NdFeB, moreover the anti-corrosion properties of NdFeB coated with 510 nm SiC thin film are better than that with 410 nm SiC thin film.The fourth chapter mainly studies that Al film deposited on the NdFeB magnet as a buffer layer to improve the adhesive strength between SiC thin film and NdFeB substrate. Structure, morphology, magnetic properties as well as the corrosion resistance of uncoated and coated NdFeB samples in 0.62 mol/L NaCl,6.25 mol/L NaOH and 0.10 mol/L H2SO4 solutions were tested respectively. The results show that Al buffer layer can obviously improve the roughness of SiC thin film which has small and uniform particles, at the same time SiC/Al double layers can effectively improve the corrosion resistance of NdFeB magnet.The fifth chapter mainly studies the SiC/AIN thin films deposited on NdFeB magnet with different periods. Structures and morphologies of coated NdFeB are characterized by XRD and FESEM, and the corrosion resistance of SiC/AlN thin films with different periods were test in 0.62 mol/L NaCl,6.25 mol/L NaOH and 0.10 mol/L H2SO4 solutions respectively. The results show that the (SiC/AlN)2 multilayer thin films can successfully interrupte the columnar growth of SiC thin film, and the crystallization of main phase is improved after coating. Moreover the anti-corrosion properties of NdFeB samples coated with thin films are better than uncoated NdFeB, while the corrosion resistance of NdFeB samples coated (SiC/AlN)2 multilayers are better than that coated SiC/AIN double films. In three kinds of acid and alkali and salt solutions, the corrosion resistance of NdFeB coated (SiC/AlN)2 multilayer films sample is the best in acid solution.The sixth chapter mainly summarizes the full text and prospects for the future research directions of NdFeB.