The Fe-Incorporation Effects on the Structural Evolution of SiOC Ceramics

Fe-modified SiOC ceramic microspheres with different Fe/Si ratio were synthesized by solvothermal method with vinyltriethoxysilane and ferrous acetylacetonate as precursors. Effects of Fe/Si molar ratio and pyrolysis temperature on structure of SiOC ceramics were investigated. The carbothermal reduction results in the transformation of Fe₂O₃ into Fe₃O₄ as elevation of temperature from 600 ^oC to 800 ^oC, and Fe and Fe₃C are formed with further increase the temperature to 1000 ^oC. Fe reacts firstly with free carbon (C_free) to form Fe₃C, and which preferentially reacts with SiC to form Fe₃Si as the Fe/Si ratio is below (0.1) Only Fe₃C phase retains with the Fe/Si ratio increases to (0.2) The transformation from Fe₃C to Fe₃Si takes precedence over conversion from Fe to Fe₃Si. The Fe-incorporation reduces the phase separation temperature to 1000 ^oC. The graphitic carbon appears when the Fe/Si ratio is above 0.1, which is produced by the catalytic graphitization of Fe and conversion of Fe₃C to Fe₃Si. However, the C_free content decreases as increase of pyrolysis temperature, structural transformation of Fe₃C to Fe₃Si is dominant for the formation of graphitic carbon.