Neodymium magnet is a permanent magnet material based on the intermetallic compound Nd2Fe14B. NdFeB permanent magnets have been widely used in modern industry and electronic technology due to their high magnetic energy product and coercivity, and high energy density, which makes it possible to make instruments, electroacoustic motors, and magnetic separation, and magnetization equipment small, lightweight and thin.
Neodymium has the advantages of high-cost performance and good mechanical properties; the disadvantages are low Curie temperature point, poor temperature characteristics, and ease to pulverize and corrode. It must be improved by adjusting its chemical composition and adopting surface treatment methods to meet the requirements of the practical application.
The sintered NdFeB permanent magnets are made of powder metallurgy. The melted alloy is made into powder and pressed into compacted embryos in the magnetic field. The compacted embryos are sintered in inert gas or vacuum to achieve densification. In order to improve the coercivity of magnets, aging heat treatment is usually needed.
Applications of neodymium magnets
At present, the main application fields are permanent magnet rotor, generator, nuclear magnetic resonance imager, magnetic separator, acoustic loudspeaker, magnetic levitation system, magnetic drive, magnetic lifting, instruments and meters, liquid magnetization, special-shaped magnet magnetotherapy equipment, and so on. It has become automobile manufacturing, general machinery, petrochemical, and electronic information industry.
Comparison between NdFeB and other permanent magnets
NdFeB permanent magnet is the strongest permanent magnet in the world at present. The magnetic energy product of a special-shaped magnet is ten times higher than that of ferrite, about twice as high as that of the first and second-generation rare earth magnets (samarium-cobalt permanent magnet), and is known as “the king of permanent magnets”. Instead of other permanent magnets, It can double the volume and weight of the device. Because of the abundant neodymium resources, compared with the samarium-cobalt permanent magnet, the special-shaped magnet replaces the expensive cobalt with iron, which makes the products cheap in price and good in quality, so it has been widely used.
The principle of ferromagnetic NdFeB
1. Ferromagnetic materials such as iron, cobalt, nickel, or ferrite are different. The electron spins in them can be arranged spontaneously in a small range to form a spontaneous magnetization region, which is called a magnetic domain. In ferromagnetic materials after magnetization, the internal magnetic domains are neatly arranged in the same direction, so that the magnetism is strengthened, constituting a magnet. The magnet’s absorption process is the magnetization process of the iron block. The magnetized iron block and the magnet produce attraction between different polarities, and the iron block is firmly attached to the magnet.
2. Matter is mostly made up of molecules, molecules are made up of atoms, and atoms are made up of nuclei and electrons. Inside the atom, electrons spin and revolve around the nucleus. These two motions of electrons generate magnetism. But in most substances, electrons move in different directions, in disorder, and the magnetic effects cancel each other out. Therefore, most substances do not exhibit magnetism in normal conditions.
3. Determined by the characteristics of the magnet, if interpreted by the atomic current, it is the magnetic field generated by the current magnetizing other objects, magnetizing objects produce an electric field, then the electric field has interaction force.