Revealing the Substrate Constraint Effect on the Thermodynamic Behaviour of the Pd-H through Capacitive-based Hydrogen-Sorption Measurement.

Mechanical constraints imposed on the Pd-H system can induce significant strain upon hydrogenation-induced expansion, potentially leading to changes in the thermodynamic behaviour, such as the phase-transition pressure. However, the investigation of the constraint effect is often tricky due to the lack of simple experimental techniques for measuring hydrogenation-induced expansion. In this study, we developed a capacitive-based measurement system to monitor hydrogenation-induced areal expansion, which allows us to control and evaluate the magnitude of the substrate constraint. By using the measurement technique, we investigate the influence of substrate constraint intensity on the thermodynamic behaviour of the Pd-H system. Through experiments with different constraint intensities, we found that the difference in the constraint intensity minimally affects the phase-transition pressure when the Pd-H system allows the release of constraint stress through plastic deformation. Our experiments can improve the understanding of the substrate constraint behaviours of Pd-H systems allowing plastic deformation while demonstrating the potential of capacitive-based measurement systems to study the mechanical-thermodynamic coupling of M-H systems. This article is protected by copyright. All rights reserved.