Microstructure of Iron Dispersing Al₂O₃ Particle Reduced from (Fe,Al)₂O₃ by CO–CO₂ Gaseous

Abstract

Carbon monoxide reduction of (Fe,Al)₂O₃ was carried out in order to clarify the possibility for ODS to be made by selective reduction of solid solution. The microstructure of reduction product was observed with XRD, SEM and EDS. The results are summarized as follows.
The precipitate particle of about 100 nm was observed in iron reduced by 97%CO–3%CO₂ at 1273–1373 K and was identified as κ′-Al₂O₃. On the other hand, the precipitate particle was Fe(Fe,Al)₂O₄ of spinel structure by using low reducing potential gas of 80%CO–20%CO₂. The size of their particle was more than 200 nm.
And then, the sequential reduction of (Fe,Al)₂O₃ by various CO–CO₂ ratios at 1273 K was carried out to investigate the structure transformation of products during CO reduction.
Solid solution of (Fe,Al)₂O₃ was reduced to solid solution of Fe₃O₄(FeOAl₂O₃). When the iron oxide was reduced to ‘FeO’, the Fe₃O₄(FeOAl₂O₃) was transformed to ‘FeO’ and Fe(Fe,Al)₂O₄ of spinel structure with the irregular shape. The solubility of Al₂O₃ in ‘FeO’ was less than 1%. It seemed that the size of Al₂O₃ particle in reduced iron depends on the that of Fe(Fe,Al)₂O₄ particle in FeO, which was affected by reducing potential.