The preparation and characterization of polymer-derived Fe/Si/C magnetoceramics

In this work, the preparation of polymer-derived Fe/Si/C ceramics was achieved by synthesis and pyrolysis of the preceramic hyperbranched polyferrocenylsilane. The Fe/Si/C ceramics obtained under various experimental conditions such as different pyrolytic temperatures, atmospheres and heating rates, were investigated by TG–MS, XRD, and XPS. Moreover, the magnetic properties of the ceramics were investigated by the vibrating sample magnetometer (VSM). Experimental results indicated that the pyrolysis of the preceramic polymer started above 250 °C and completed among 800–1000 °C. The crystallization of the pyrolytic product started at 500 °C. Besides the heat treatment temperature, the atmosphere and heating rate also played important roles in the composition and magnetic properties of the corresponding Fe/Si/C ceramics. Fe existed as α-Fe in ceramics sintered at 900 °C under N2 and NH3 atmospheres. However, the main components in ceramic product sintered under air were γ-Fe2O3 and carbon. Although all of the three ceramic products sintered under different atmosphere were ferromagnetic with low remanent magnetization and coercivity, the ceramics sintered under NH3 had the largest saturation magnetization. The saturation magnetization of the Fe/Si/C ceramics further ascended when fabricated under NH3 with a slower heating rate, in which Fe existed as α-Fe, Fe3O4 and γ′-Fe4N.