Microreaction mechanism in reduction of magnetite to wustite

Abstract

In order to understand the microreaction mechanism of the reduction of magnetite to wustite, hydrogen ions were implanted into magnetite at room temperature by an ion accelerator. The crystalloid transformation during the reduction process was investigated by using selected-area electron diffraction patterns. The experimental results showed that {220} planes on the surface of magnetite were changed first because the concentration of oxygen ions on the {220} planes is higher than other planes to follow the reaction of oxygen ions with hydrogen ions, leaving the {220} planes and resulting in rearrangement of ions. On the other hand, oxygen ions migrate more difficultly than iron ions in magnetite; therefore, {220} planes in the bulk are more stable than other planes. Based on the experimental facts, two kinds of microreaction mechanisms in reduction of magnetite to wustite are suggested. It was found that (1) wustite with [001] direction was formed on the magnetite with [001] direction, (2) (220) and (200) planes of wustite were parallel with (220) and (400) planes of magnetite, respectively, in crystal structure between parent phase and new phase, (3) some {220} planes were formed earlier than other ones in wustite during the reduction process. These results can be considered as due to the similar geometric distribution of oxygen ions between magnetite and wustite.

Density Functional Theory Study on the Carbon-Adhering Reaction on Fe3O4(111) Surface

“…It was proved that the reduction rate of iron oxides was very dependent on the microstructure of the reaction product, and the pore diffusion of gases through a porous reactant or product was even the rate-controlling step in the process of iron oxide reduction. [27,28] Hence, it was important to analyze the microstructure of the Fe 3 O 4 (111) surface after carbon adsorption. Figure 13 showed the comparison of the carbon-adhering and clean-optimized Fe oct2 -terminated Fe 3 O 4 (111) surface.…”

The Materials Science behind Sustainable Metals and Alloys

“…Important examples for future research directions in that context are the direct reduction of iron oxides by using green hydrogen and green ammonia, Figure (see section ). ,,− Also, it seems worth studying how different reductants would interact with each other and possibly influence the reduction kinetics and also the compounds that are created when jointly used in the same reactor (some reductants would most likely not only produce pure metal during the reduction but also other compounds). , …”

Hierarchical Nature of Hydrogen-Based Direct Reduction of Iron Oxides

“…At the magnetite/wüstite interface, a cubeon-cube OR ( i.e. , ( 1 1 0 ) mag // ( 1 1 0 ) wüs and [ 110 ] mag // [ 110 ] wüs ) was observed [23] . This OR indicates that reduced iron ions ( e.g.…”

“…This OR indicates that reduced iron ions ( e.g. , on the external solid/gas interface) migrate towards ferrous vacancies on oxygen ion planes to form wüstite, while the oxygen lattice is maintained [23] . There is still a lack of direct microscopic and spectroscopic evidence as well as atomistic understanding of these diffusion and reaction mechanisms across the interfaces.…”