Mössbauer Spectral Observation of α-Fe2O3 Supported on Silica Gel during Activation

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Abstract
Mössbauer spectral studies were made of samples of α-Fe2O3 highly dispersed on silica gel before and after activation, which consisted of evacuated heating at 475°C. The spectra gave Ividence that Fe2+ ions were produced from α-Fe2O3 during the activation process. Reduction was impossible after the activation and oxidation had been repeated three times. However, the inactivated sample came to be again reduced by activation after having been exposed to water vapor at room temperature. In order to explain these facts, a working hypothesis was advanced that the hydroxyl groups near the surface of the particles play a principal role in reacting with organic contamination from the vacuum system, as a result bringing about the partial reduction of α-Fe2O3.