Hydrothermal treatment of spark plasma sintered FeSiBCCr/Ni0.5Co0.5Fe2O4 soft magnetic composites for enhanced magnetic performance

Soft magnetic composites (SMCs) have broad applications in power electronics and automotive engineering fields. As the demand for high efficiency and environmentally friendly technologies grows, research and development of these materials have become increasingly important. This study involves coating FeSiBCCr powders with a layer of Fe(OH) 3 -Ni(OH) 2 -Co(OH) 2 , followed by spark plasma sintering and hydrothermal treatment to transform the insulating layer into Ni 0.5 Co 0.5 Fe 2 O 4 , thereby fabricating FeSiBCCr/Ni 0.5 Co 0.5 Fe 2 O 4 SMCs. The SMCs were characterized in terms of surface morphology, microstructure, composition, and magnetic properties before and after hydrothermal treatment. Results demonstrate that even sintered samples can undergo structural modifications in the insulating layer via hydrothermal treatment. This process oxidizes Fe 2+ produced during sintering to Fe 3+ , converting the insulating layer to spinel ferrite, thereby increasing the SMCs' resistivity, reducing coercivity, and significantly lowering core loss. The sintered SMCs containing 4 % ferrite after 12 hours of hydrothermal treatment, the resistivity increased 15.7 times to 109.1 mΩ·cm, core loss decreased from 3929.6 mW/cm 3 to 1152 mW/cm 3 (100 mT, 100 kHz), effective permeability reached 77. • First proposal for hydrothermal treatment of SMCs prepared by spark plasma sintering. • Hydrothermal treatment changes the structure of the insulation layer of SMCs. • Hydrothermal treatment increases the resistivity of SMCs, reduces coercivity, and lowers core loss.