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Breakthrough development of high performance anisotropic rare earth permanent magnetic materials

Rare earth permanent magnet materials is the best permanent magnet material for magnetic performance. However, the maximum energy of rapidly quenching NdFeB magnetic powder of the commercial product is 12~18MGOe, it is difficult to meet the needs of high-end, especially the current development trend of electric appliance miniaturization, an urgent need to develop an anisotropic bonded magnet with high magnetic energy product; development of new energy vehicles and hybrid electric vehicle requirements, the urgent need to research and development of anisotropic bonded magnets with high coercivity and high temperature. Under the background of this market, Peking University of applied magnetic center high performance anisotropic magnetic powder and magnet research and development carried out a series of research work, has made a breakthrough .

In 1990, Peking University and Trinity University in Ireland discovered the nitridation effect in a rare earth iron alloy, that is, through a gas solid reaction, adding nitrogen atoms to Nd (Fe, M) 12 (M=Ti, V, Mo)... ) or Sm2Fe17, corresponding to the formation of nitrides: Nd-Fe-N and samarium iron nitrogen, so the magnetic rare earth alloy has been fully, greatly improved, the intrinsic magnetic properties are comparable to those of neodymium iron boron nitrogen atom effect. The gap is mainly manifested in two aspects, one is to change the thin crystal field the soil ions, resulting in magnetic anisotropy changes; on the other hand is the effect of iron atom and 3D electron energy The band structure increases the saturation magnetization and Curie temperature, mainly due to the increase of atomic magnetic moment of iron.

Although rare earth nitride has excellent intrinsic magnetic properties, but the existing manufacturing process of NdFeB magnet powder, it is difficult to scale to produce high performance magnetic powders. By optimizing alloy smelting technology in Peking University, using rapid solidification technology and temperature control of nitride, time and particle size, were successfully prepared with high performance NdFe10.5Mo1.5Nx and PrFe10.5V1.5Nx powder, 21MGOe and 17MGOe. and NdFe10.5Mo1.5Nx do not exhibit 3.8T and coercivity 32MGOe in 1.5K low temperature magnetic energy The maximum energy product shows its important application value at low temperature. Peking University has developed a quick setting - sheet alloy grinding ball milling nitriding process, producing high performance Sm-Fe-N powder is stable, the coercivity reaches 13kOe, remanence is 155emu/g, the maximum energy product can reach 41~43MGOe. at the same time, they use the ball milling process of surfactant assisted, in heptane solvent preparation anisotropic milling system Sm-Fe-N submicron particles, realize the anti oxidation coating on the surface of magnetic powder. After corrosion test confirmed that one year, modified powder showed good corrosion resistance of this coating, surfactant assisted ball milling obtained good dispersion The lamellar particles, which tend to be aligned in the direction of the magnetic field, are beneficial to the shaping of the magnetic field orientation of the anisotropic bonded magnets

To build the basic adult production line production of 100 tons of anisotropic Nd-Fe-N powder in the success of the construction of Peking University, 100 tons of anisotropic magnetic Sm-Fe-N demonstration production line. In this line, they will be accelerating the process used in Sm2Fe17 alloy smelting furnace, and to achieve a single two hundred kg single good, stable production Sm2Fe17 quick setting microstructure uniform, 200 kg of quick setting equipment and on the basis of research and development can be applied to Sm2Fe17 alloy melting.

Based on the above research results, in 2013 in the National 863 program and Beijing Hengyuan Valley company under the support of 100 ton anisotropic Sm-Fe-N powder production line built in the Beijing District of Pinggu, the production of magnetic properties of more than 40MGOe, China has the independent property rights and innovation characteristics.
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