The Use of the Electrochemical Quartz Crystal Microbalance (EQCM) in Corrosion Studies of UO2 Thin Film Models

Abstract

The sputtering of actinide targets in Ar atmosphere with a controlled partial pressure of reactive gas (e.g. O2, N2) allows actinide compound thin films on various substrates to be produced. Pure UO2 thin films have been deposited on piezoelectric quartz crystal electrodes and characterised by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The films were then examined by electrochemical techniques with a calibrated EQCM system. First cyclovoltammetric studies show the comparability of the thin film model systems with bulk UO2 and the reliability of the EQCM method as tool for fuel corrosion studies. Thanks to the real-time mass and electrochemical information from the EQCM, the charge over mass ratios (Q/m) could be calculated from the electrochemical experiments. These ratios are then compared to theoretical values for certain corrosion reactions so the observed anodic and cathodic processes in the typical cyclovoltammograms of UO2 electrodes can be assigned to these corrosion processes. This helps to verify corrosion mechanisms, propose alternative reactions and gain a deeper insight into the reactions involved in the corrosion processes of the fuel matrix.