Controllable SiO2 coating layer of FeSiBPNb amorphous powder cores with excellent soft magnetic properties

Amorphous powder cores based on spherical (Fe 0.76 Si 0.09 B 0.1 P 0.05 ) 99 Nb 1 amorphous powder and their SiO 2 layer prepared by in situ coating insulation process were investigated in detail. These cores were characterized by scanning electron microscopy and X-ray diffraction analyses, and the results revealed that the surface layer of the amorphous powder was composed of SiO 2 with uniform surface coverage. The thickness of the SiO 2 insulating layer could be controlled by adjusting the tetraethyl orthosilicate (TEOS) content. By cold-pressing with epoxy resin under a pressure of 1800 MPa, a ring powder core with an outer diameter of 20.3 mm, inner diameter of 12.7 mm, and height of 5.3 mm was prepared. The FeSiBPNb composite core showed its best properties when the TEOS content was 2 mL/g (the volume of TEOS for each gram of (Fe 0.76 Si 0.09 B 0.1 P 0.05 ) 99 Nb 1 amorphous powder, mL/g), which showed good relative permeability in the high-frequency range of up to 10 MHz and a low core loss of 320 W/kg under the maximum magnetic flux density of 0.1 T and frequency of 100 kHz.