Since the 1980s, functional materials, ecological environment materials, and intelligent materials have played an increasingly important role in the modern civilization and social progress of human society.
Among functional materials, magnetic materials play an important role. A ferromagnetic material that can be used to fabricate a magnetic functional device is called a magnetic material. Magnetic materials include hard magnetic materials, soft magnetic materials, semi-hard magnetic materials, magnetostrictive materials, magnetic films, magnetic micro-powders, magnetic liquids, magnetic refrigerating materials, and magnetic cold storage materials, among which the largest and most widely used are hard. Magnetic materials and soft magnetic materials. The 21st century will be an era of rapid development of the world economy and technology. Rare earth permanent magnets play an important role in promoting the development of high-tech industries (especially electronic information industry), among which NdFeB permanent magnet materials are among the pearls. .
It has the characteristics of light weight, small size and strong magnetic properties. It is the most cost-effective magnet to date, and is known as the magnetic king in the magnetic field.
As the third-generation rare earth permanent magnet material, NdFeB is widely used in electric motors. Compared with traditional motors, it has the characteristics of high efficiency, energy saving, light weight, small volume, good control speed and reliability, and can be widely used in wind power generation. , electric vehicles, industrial motors, household motors and other fields, its high cost performance makes its application field continue to expand, so in recent years in the scientific research and production applications have been sustained high-speed development.
An excellent permanent magnet material should have the following three conditions: high saturation magnetization Ms, high Curie temperature Tc, and high magnetic anisotropy field Ha.
NdFeB manufacturing materials are richer and cheaper than other rare earth permanent magnet materials, which greatly reduce the price. At the same time, it has a record maximum magnetic energy product (in theory, up to 512kJm/3) and high room temperature anisotropy field (Ha =7T) and high saturation magnetic polarization (Js = 1.6T) have received wide attention. The excellent intrinsic magnetic properties of the main phase Nd2Fe14B are the main source of excellent magnetic properties of such magnets. The disadvantage is that its Curie temperature is relatively low (Tc = 312 ° C), the coercive force is not high enough, so the thermal stability and corrosion resistance is poor, which limits its application.