Introduction to the characteristics of nanocrystalline cores1

On the one hand, the characteristics of the nanocrystalline magnetic core can isolate the eddy current, and the data is suitable for higher frequencies; on the other hand, the data has low permeability and constant permeability due to the gap effect between the particles; due to the small particle size, there is basically no skinning phenomenon, the change of permeability with frequency is relatively stable; in addition, the powder core can be made into special-shaped parts of various shapes for use in different fields; finally, the industrial damaged strip is crushed into magnetic powder, and then made into magnetic powder core, which can reduce the loss , improve the use value of data. The magnetoelectric properties of the magnetic powder core mainly depend on the magnetic permeability of the powder material, the size and shape of the powder, the filling factor, the content of the insulating medium, the molding pressure and the heat treatment process. In the future, soft magnetic powder cores will continue to follow high Bs, high μ, high Tc, and low Pc. The magnetic powder core is a soft magnetic material mixed with ferromagnetic powder and insulating medium. Because the ferromagnetic particles are very small (0.55 μm is used for high frequencies), they are separated by a non-magnetic electrical insulating film. Low Hc, high frequency, miniaturization and thinning are developing to meet the increasing trend of thinning, miniaturization and even integration of magnetic components.​​

Characteristics and applications of nanocrystalline cores Nanocrystalline alloys have high saturation magnetic induction. Good stability, the material becomes brittle after heat treatment, and it is easy to process into alloy powder. It is possible to make a new type of ultra-microcrystalline magnetic powder core with this alloy powder. The magnetic permeability of the nanocrystalline magnetic powder core is still low compared with that of the tape-wound nanocrystalline magnetic core, and the soft magnetic performance is unstable. Problems to be solved at present: 1. Effective control of the growth of nanocrystals during heat treatment; 2. Forming of magnetic powder cores; 3. Influence of heat treatment specifications on the soft magnetic properties of magnetic powder cores.​​

Application areas of nanomagnetic cores In many power electronic devices, noise is the main source of interference in circuits. Various filters are required to reduce noise. As the main component of differential mode inductors, magnetic powder cores play a key role in filters. In order to obtain better filtering effect, the magnetic powder core material is required to have the following performance characteristics: high saturation magnetic induction, wide constant permeability, good frequency characteristics, good AC/DC superposition characteristics and low loss characteristics. In response to the above requirements, soft magnetic materials for inductors, such as iron powder cores, notched amorphous alloy cores, and iron-nickel-aluminum powder cores (MPP powder cores) have been successively developed. These materials play their respective advantages and roles under different application conditions. At present, UP powder core occupies a major share in the high-end market. However, due to the complex manufacturing process of M powder core, the high price of raw materials, and the high price of powder core, its scope of application is limited. In recent years, iron-based nanocrystalline soft magnetic powder cores have attracted much attention because of their low price, simple preparation process, and excellent performance. Their research is quite active, and it is expected to replace the local use of UP powder cores and be applied in high-frequency fields.