Magnetic materials of rare-earth permanent magnets

• Main Author: Aw, Charlotte Bixi
• Other Authors: Su Haibin
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Materials::Magnetic materials
• Online Access: http://hdl.handle.net/10356/38625
• Institution: Nanyang Technological University

The report below investigates on magnetic materials mainly on permanent magnets. The number of materials systems used to make magnets on an industrial scale is limited. This has inspired the need to find better magnetic material. They are, in chronological order of appearance, AlNiCo (late 1930s), hard ferrites (1950s), the family of Sm-Co magnets which gave rise to two different magnet groups, SmCo5 (late 1960s) and Sm(CoFeCuZr)7-8 often referred to as the “2-17”type magnets(late 1970s) and the neodymium-iron-boron (NdFeB) family (mid 1980s). This report will focus mainly on the rare earth magnets namely the Sm-Co magnets and the NdFeB magnets. The fabrication of the rare-earth permanent magnets together with the preparation techniques were discussed in the report. The two principal magnets types may be made with Sm and Nd: sintered magnets (dense and oriented) which show the highest performance and bonded magnets (magnetic powders injected into a non-magnetic matrix, often a polymer) which are simpler and cheaper to manufacture, but exhibit poorer magnetic performance than the former. The energy product of hard magnetic materials is an important parameter that relate to the applications for hard magnetic materials. Hence, the derivation of energy product for an ideal and real magnet will be covered in this report. Studies will also be carried out on the various hard magnetic materials with different (B.H)max. Also, to improve the storage energy of a magnet, a high (B.H) is required. The report also investigate on the various factors that will affect Hc and hence introducing various dopants to the magnets so as to improve the (B.H)max value. The results obtained showed that the small percentage addition of dopants such as Gd and Td to NdFeB and SmCo5 magnets respectively was a simple method to improve the (B.H)max of the magnets.