Characterization of composite materials based on Fe powder (core) and phenol-formaldehyde resin (shell) modified with nanometer-sized SiO_2

摘要

Soft magnetic composites based on Fe powder and phenol-formaldehyde resin (PFR) modified with tetraethylorthosilicate are investigated in detail. The chemical synthesis of PFR, its modification with nanometer-sized SiO_2 particles created by sol-gel method and subsequent coating, enables a preparation of insulating PFR-SiO_2 (PFRT) layer on the surface of Fe particles. Thermal degradation and FTIR analysis of PFR and PFRT with different amount of SiO_2 was examined. Mechanical hardness and flexural strength of FePFRT composites was studied depending on the amount of nanosized-SiO_2 in the coating. SEM serves in evidence of a defectless microstruc-ture if the coating contains at least 2% of silica particles. The morphology of Fe particles implies uniform coating without any visible exfoliation. A presence of fine SiO_2 particles was verified by TEM. The best magnetic properties were found in Fe-PFRT composite with 2% of SiO_2 in the insulating layer on behalf of its uniform arrangement and homogeneity.