Papers by Keyword: Fe Oxides

Abstract: χThe nanostructure of Fischer-Tropsch (FT) Fe carbides are investigated using aberration-corrected high-resolution transmission electron microscopy (TEM). The plasma-generated Fe carbides are analyzed just after synthesis, following reduction via a H2 treatment step and once used as FT catalyst and deactivated. The as-produced nanoparticles (NPs) are seen to be abundantly covered with graphitic and amorphous carbon. Using the extended information limit from the spherical aberration-corrected TEM, the NPs could be indexed as a mixture of NPs in the θ-Fe3C and χ–Fe₅C₂ phases. The reduction treatment exposed the NPs by removing most of the carbonaceous spe_{Subscript text}cies while retaining the χ–Fe₅C₂. Fe-carbides NPs submitted to conditions typical to FT synthesis develop a Fe₃O4 shell which eventually consumes the NPs up to a point where 3-4 nm residual carbide is left at the center of the particle. _{Subscript text}Various mechanisms explaining the formation of such a microstructure are discussed.

Abstract: Hardness of oxide scales on Fe-(0, 0.5, 1.5, 3.0)Si alloys was studied at room temperature after oxidation at 1273 K for 18 ks in oxygen, and at 1073 and 1273 K for 180 and 1080 ks in dry air, by micro-Vickers hardness measurements. After oxidation at 1273 K for 18 ks, high-temperature hardness of oxide scales on Fe-(0, 1.5, 3.0)Si alloys was also measured at 1273 K. Oxide scales on Fe-Si alloys were mainly Fe2O3, Fe3O4, FeO and Fe2SiO4. Hardness of Fe2O3, Fe3O4 and FeO on Fe was 6.7, 4.0 and 3.5 (GPa), respectively, and hardness of Fe2O3 on Fe-Si alloys slightly increased with increasing silicon content at room temperature. At 1273 K, hardness of Fe3O4 and FeO on Fe was 0.08 and 0.05 (GPa), respectively, and hardness of Fe2O3 on Fe-1.5Si alloy was 0.32 (GPa), and that of Fe2O3 and Fe2SiO4 on Fe-3.0Si alloy was 0.53 and 0.63 (GPa), respectively.