Study On The Properties Of Fe-Si-Al Soft Magnetic Composite With Confined Insulation Coating

In recent years,with the development of electronic components towards miniaturization,lightweight and high-frequency,higher requirements have been put forward for the properties of soft magnetic composite（SMCs）,which requires not only high magnetic permeability,but also low loss.In the preparation process of SMCs,insulation coating is the most critical step,and the selection of insulation coating process and insulation coating material is the key to improve the properties of SMCs.In this paper,a uniform and dense aluminum oxide insulating coating layer is in situ formed on the surface of Fe Si Al by using the confined insulation coating process,and Fe Si Al SMCs with high effective permeability and low loss is obtained.The influence of different insulating coating processes on the properties of SMCs is investigated,and the difference in properties prepared by confined insulation coating and the traditional coating process is compared,The relationship between microstructure and properties was established through a series of characterization methods,and the physical mechanism of improving the performance of the confined insulation coating was explored.It was found that:（1）Using sodium metaaluminate as catalyst,the double alumina insulating layer was obtained on the surface of Fe Si Al by the method of confined catalysis.The magnetic permeability of the Fe Si Al SMCs was 100,the loss was 120 m W/cm³（50m T,100 k Hz）,and the comprehensive performance was better than the traditional phosphoric acid passivated Fe Si Al SMCs.The thin and uniform double alumina insulating layer can be observed in the high resolution transmission electron microscope.The inner layer is obtained by the aluminum atom on the surface of Fe Si Al through the confined catalytic,with a thickness of 4 nanometers.The outer layer is produced by the hydrolysis of sodium metaaluminate,with a thickness of more than 10 nanometers.（2）The oxygen storage material-Ti O₂ is coated on the surface of Fe Si Al by the sol gel method.During the annealing process,aluminum and oxygen atoms are thermally diffused,and the oxygen atoms in titanium dioxide and aluminum atoms on the surface of Fe Si Al react in a confined solid state at the interface.The aluminum oxide insulation layer is in-situ prepared on the surface of Fe Si Al,which has a good lattice matching with the matrix to achieve effective electrical isolation,The pinning of domain wall displacement is weakened.At the same time,titanium dioxide containing a large number of oxygen vacancies has ferromagnetism,thus reducing the magnetic dilution effect.The Fe Si Al SMCs has a permeability of 143 and a loss of only 130m W/cm³（50m T,100k Hz）,showing excellent magnetoelectric properties.（3）In order to improve the DC bias performance of the Fe Si Al SMCs,we applied the titanium dioxide confined coating system to the aerosol Fe Si Al,and realized the Fe Si Al SMCs with the permeability of 65.12,the loss of 126.3 m W/cm³（50m T,100k Hz）,and the DC bias of 4%.In this system,we studied the corrosion resistance of the Fe Si Al SMCs,and found that the corrosion resistance of the Fe Si Al SMCs was also significantly improved compared with the SMCs coated by only silicone resin.