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 behavior, 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, a capacitive-based measurement system is developed to monitor hydrogenation-induced areal expansion, which allows us to control and evaluate the magnitude of the substrate constraint. By using the measurement technique, the influence of substrate constraint intensity on the thermodynamic behavior of the Pd-H system is investigated. Through experiments with different constraint intensities, it is found that the diffefrence in the constraint intensity minimally affects the phase-transition pressure when the Pd-H system allows the release of constraint stress through plastic deformation. These 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. The substrate constraint effect on the metal-hydrogen system can result in significant mechanical stress during hydrogenation-induced expansion. However, a quantitative study of this effect is challenging due to the limitations in measurement techniques. In this study, a capacitive-based measurement system is employed to reveal the influence of substrate constraint on the thermodynamic behavior of the Pd-H system.image