Introduction to the characteristics of nanocrystalline magnetic core

Introduction to the characteristics of nanocrystalline magnetic cores

On the one hand, eddy currents can be isolated, and the data is suitable for higher frequencies; on the other hand, due to the gap effect between particles, the data has low permeability and constant permeability; due to the small particle size, there is basically no crusting phenomenon, and the permeability changes with frequency are relatively stable; in addition, the powder core can be made into various shapes of special-shaped parts for use in different fields; finally, the industrial broken strip is crushed into magnetic powder and then made into magnetic powder cores, which can reduce losses and improve the use value of data. The magnetic and electrical properties of magnetic powder cores 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. Magnetic powder cores are soft magnetic materials mixed with ferromagnetic powder and insulating medium. Because the ferromagnetic particles are very small (0.55μm is used for high frequency), they are separated by non-magnetic electrical insulating films. Low Hc, high frequency, miniaturization and thinness are developing to meet the growing trend of thin film, miniaturization and even integration of magnetic components.

Characteristics and Applications of Nanocrystalline Magnetic Cores

Nanocrystalline alloys have high saturation magnetic induction intensity. Good stability, the material becomes brittle after heat treatment, and is easy to process into alloy powder. It is possible to make new ultra-fine crystal magnetic powder cores with this alloy powder. The magnetic permeability of nanocrystalline magnetic powder cores is still very low compared with nanocrystalline magnetic cores wrapped with tape, and the soft magnetic properties are unstable. Problems currently waiting to be solved:

1. Effectively control the growth of nanocrystals during heat treatment;

2. The molding problem of magnetic powder cores;

3. The influence of heat treatment specifications on the soft magnetic properties of magnetic powder cores.

Application fields of nano-magnetic cores

In many power electronic devices, noise is the main source of interference in the circuit. Various filters are needed 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 effects, the magnetic powder core material is required to have the following performance characteristics: high saturation magnetic induction intensity, wide constant magnetic 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 core, notched amorphous alloy core and iron-nickel-aluminum powder core (MPP powder core), have been developed one after another. These materials have their own advantages and functions 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, high raw material prices, and high powder core prices, its scope of application is subject to certain restrictions. In recent years, iron-based nanocrystalline soft magnetic powder cores have attracted much attention due to their low price, simple preparation process and excellent performance. Its research is quite active and is expected to replace the local use of UP powder cores and be applied in high-frequency fields.