A comprehensive XPS investigation of the effect of aqueous corrosion on the surface of glass-zirconolite composite material (Fe–Al–BG–CaZrTi₂O₇)

Abstract

Extensive XPS analyses of iron-aluminum borosilicate glass (Fe-Al-BG), zirconolite (CaZrTi2O7), and Fe-Al-BG-CaZrTi2O7 composite material have demonstrated that a hydrated layer has been formed on the surface of these materials after exposure to water. The surface chemistry of Fe-Al-BG-CaZrTi2O7 composite material as a potential nuclear wasteform candidate was observed to change in a similar fashion to the borosilicate glass as a current wasteform material after these materials are exposed to water. The XPS measurements suggest that the aqueous corrosion of the Fe-Al-BG-CaZrTi2O7 composite material is a result of ion exchange, hydrolysis, and redox reactions of metal-oxygen bonds with water at the surface of the Fe-Al-BG-CaZrTi2O7 composite material. Moreover, the XPS results proved that the composition and chemical environment of the precipitated layer on the surface of the Fe-Al-BG-CaZrTi2O7 composite material after exposure to water remained unchanged between 270 and 365 days of exposure to water. The stability of the surface layer during this time frame could potentially protect the surface of the Fe-Al-BG-CaZrTi2O7 composite material from further corrosion.