Measuring Hydrogen Induced Palladium Expansion through Diffraction Phase Microscopy

Abstract

Our research aims to use diffraction phase microscopy (DPM) to measure palladium lattice expansion caused by the adsorption of hydrogen in real time. We need to be able to accurately model the Pd-H system because it is critical to designing hydrogen sensors, which are important because they can monitor hydrogen. They can be used to watch the lower explosive level (LEL) of hydrogen or other processes utilizing hydrogen like burning hydrogen and various industrial settings. Patterned palladium ridges and pillars are fabricated and exposed to pulses of hydrogen at various concentrations and imaged with DPM to measure the change in height due to lattice expansion. We control the hydrogen concentrations through LabVIEW with mass flow controllers and control the pulse shapes of hydrogen with solenoid switches. This enables us to solve for the expansion coefficients as a function of hydrogen concentration and the ability to solve for the complex optical refractive coefficients, n and kappa. Diffraction phase microscopy is used because it allows for measurements on a much smaller scale (nanometer resolution) than past measurements and opens up the possibility of examining the expansion in real time.