Morphological and Elemental Changes of Palladium Immersed in Deuterium under Laser Irradiation

Previous experiments by Nassisi and Biberian exploring the properties and behavior of palladium under local optical excitation in hydrogen and deuterium atmospheres have reported the unexpected emergence of lighter elements such as nickel and silicon on the Pd substrate. While morphological and phase changes of Pd bathed in hydrogen have been studied extensively due to the remarkable ability of Pd to absorb hydrogen into the metal matrix, the effect on Pd from local excitation by laser irradiation under these conditions is less well understood. We investigate the origin and mechanism surrounding the emergence of these lighter elements from this relatively simple experiment. We submerged three separate Pd bars in 3 bar abs. of hydrogen and deuterium while simultaneously exposing them to optical stimulation at three different wavelengths and intensities. We acquired optical and SEM/EDS information from the samples both pre and post experiment in order to study before and after potential elemental changes to/on the Pd lattice. Whereas little to no elemental changes were observed under locations not irradiated, we found significant elemental differences under the locations of laser irradiation including the unexpected emergence of two separate 1 mm² patches of silicon under location irradiated with the green 200 mW laser and the 5mW red laser. We report on our methods and findings and recommend further investigation to explain the phenomena associated with these elemental changes.