Abstract
Preparation of microcomposite materials based on Fe powder and the modified phenol-formaldehyde resin (PFR) was investigated with the aim to design a new class of prospective soft magnetic materials. Undesirable evolution of water and other volatile by-products during curing process was eliminated by modification of resol prepolymer coating with two different inorganic additives – SiO 2 and ZnSO 4. The structure of synthesized PFR was confirmed by 13C-NMR spectroscopy. The effect of both additives on thermal degradation, structure and morphology was studied by employing TG, DSC, IR and SEM analysis. The addition of ZnSO 4 into PFR caused a significant change in the polymer structure, which is constituted by nano-fibers linking Fe particles. The observed unusual structure of PFR–ZnSO 4 coating on Fe particles results in a higher mechanical hardness and flexural strength compared to the Fe particles coated by the pure PFR or PFR–SiO 2. It is shown that the microcomposites with a few percentages of PFR coatings exhibit a substantial increase of the specific resistivity and they still belong to soft magnetic materials with low enough coercivity.
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