Radiation-Induced Chemical Changes to Iron Oxides

Area of Science:

• Materials Science
• Radiation Chemistry
• Surface Chemistry

Background:

• Iron oxides are crucial in various industrial and environmental processes.
• Understanding their behavior under radiation is vital for applications involving ionizing radiation.
• The role of adsorbed water on iron oxide surfaces during radiolysis is not fully understood.

Purpose of the Study:

• To investigate the radiolysis of different iron oxide powders with varying amounts of adsorbed water.
• To determine the influence of radiation type (gamma rays, helium ions) on hydrogen production.
• To characterize the surface properties and structural changes of iron oxides post-irradiation.

Main Methods:

• Radiolysis experiments using gamma rays and 5 MeV (4)He ions.
• Surface characterization via temperature-programmed desorption (TPD) and diffuse reflection infrared Fourier transform spectroscopy (DRIFTS).
• Post-irradiation analysis using X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS).

Main Results:

• Molecular hydrogen (H2) production was observed exclusively from water adsorbed on Fe2O3, with yields orders of magnitude higher than bulk water.
• Different iron oxides (FeO, Fe3O4, Fe2O3) in aqueous slurries showed varying H2 yields dependent on oxide type and water content.
• No changes in crystal structure were detected by XRD, but Raman and XPS indicated surface modifications, including Fe2O3 formation on FeO and Fe3O4 surfaces and general oxygen species formation.

Conclusions:

• Adsorbed water on iron oxide surfaces, particularly Fe2O3, is highly susceptible to radiolysis, leading to significant H2 production.
• The radiolysis process can induce surface transformations on iron oxides without altering their bulk crystal structure.
• These findings have implications for understanding radiation-induced processes in iron oxide-based materials and systems.