LAUSR

The coated insulation layer on the surface of FeSiAl particle was prepared by an in situ generation method involving the combination of coating (utilizing a NaOH solution and NaHCO3) and high-temperature calcination for 60 min at 1250 °C. The microstructures, and magnetic and electrical properties of the coated powders, which were prepared with different concentrations of NaOH (2, 5, 10, and 15 wt%) and reaction times (10, 20, 40, and 60 min), were systematically investigated. The insulation layer of the coated powder was homogeneous and dense and contained Fe3O4, Al(OH)3, and H2SiO3 before the calcination. However, it was dominated by Al2O3 after the calcination. Al(OH)3 and H2SiO3 decomposed after the calcination into Al2O3 and SiO2 (or mixed oxide Al2SiO5), respectively, and the Al atom in the FeSiAl matrix reacted with Fe3O4 to produce Al2O3. As the NaOH concentration or reaction time increased, the layer thickness increased, and the saturation magnetic induction (Ms) and electrical resistivity (ρ) of the coated FeSiAl that had lost some Al atoms from its matrix after calcination increased significantly. The Ms and ρ of the FeSiAl powder coated with 10% NaOH for 60 min reached 161.41 emu/g and 578.6 kΩ.cm at 10 MPa pressure, respectively.