MetalOxide Heterophase Structures Formed at Low Temperature Activation of Iron. 2. IR Spectroscopy

V. A. Kotenev, N. P. Sokolova, A. M. Gorbunov, and A. Yu. Tsivadze

Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia

Received April 20, 2007

Abstract — Low-temperature activation of iron is observed during its isothermal oxidation at a temperature of 300 and an oxygen pressure of 10² Torr. A 1-h treatment provides the maximum gain in the oxide layer thickness for this oxygen pressure. According to IR spectroscopic data, the amount of F₃O₄ in the oxide reaches the maximum in the oxygen pressure interval from 10³ to 10² Torr and decreases with a further increase in the oxygen pressure. In contrast, the haematite content increases with an increase in the oxygen pressure. In the latter case, first, the content of the -F₂₃ phase increases to reach its maximum at pressures from  5 10³ to 10² Torr, while the phase of haematite -F₂₃ appears at 0.1 Torr. This confirms the earlier assumption that the haematite islets layer plays the decisive roles in the low-temperature activation and the active–passive transition of iron.

PACS numbers: 81.07.-b