Fabrication Of Soft Magnetic Alloy Powder Cores With Inorganic Oxide Coating And Their Physical Properties

As a new kind of soft magnetic composite materials, soft magnetic alloy powdercores have effectively compensated for the conventional soft magnetic metallicmaterials and soft ferrites due to their high resistivity and saturation induction. Up tonow, the soft magnetic alloy powder cores have been widely used inelectrommunication, radar, switching power supply and so on. In recent years, with thedevelopment of power electronic devices such as photovoltaic inverter andhigh-frequency switching power supply, the industry of soft magnetic alloy powdercores develops more and more rapidly and their market demands grow greatly.Inorganic oxide insulation is beneficial to improve the soft magnetic properties of softmagnetic alloy powder cores, which has become a focus of modern soft magnetic alloypowder cores development.In this paper, Fe-6.5wt.%Si soft magnetic powder cores with silica coating weresuccessfully fabricated by using gas-atomized Fe-6.5wt.%Si alloy powder modifiedwith nano-silica solution. The effects of processing parameters, including the content ofnano-silica solution and the compaction pressure on the microstructure and physicalproperties of Fe-6.5wt.%Si soft magnetic powder cores were investigated. It was foundthat a homogeneous and stable silica insulating layer was formed on the surface of thealloy powder. With increasing the content of nano-silica solution, the core’s inductance,effective permeability and saturation induction decreased, and the DC-bias property ofthe cores improved, the quality factor increased firstly and then decreased, and the coreloss decreased firstly and then increased. With increasing the compaction pressure, thecore’s inductance, effective permeability and quality factor increased, and the core lossdecreased, while the DC-bias property of the core only showed a slight change. Thissuggests that the effective insulation of Fe-Si alloy powder is very significant for thegood performance of Fe-Si alloy powder cores and suitable content of nano-silicasolution and relatively higher compaction pressure are beneficial to improve thephysical properties of Fe-Si alloy powder cores. The relatively best performance ofFe-Si alloy powder cores achieved in this study is shown as follows: the stable effectivepermeability of31.9, the maximum quality factor of98.6, the core loss of520.4mW/cm3at100kHz for Bm=50mT, and a percentage permeability of95%at50Oe.