Influence of temperature and pressure on surface modified Pd-Cu alloy foils for hydrogen purification applications

The surface of as-received Pd60Cu40 wt% foil samples was modified by depositing a Pd thin film onto one side. X-ray diffraction analysis revealed that the as-received Pd60Cu40 wt% foil contained only the disordered face centred cubic (FCC) phase. Three different Pd thin film thicknesses (100, 800 and 1400 nm) were deposited using magnetron sputtering onto the as-received Pd60Cu40 wt% foil to produce the surface modified foil samples. X-ray diffraction and X-ray photoelectron spectroscopy analysis of these samples showed a strong indication that Cu interdiffusion occurred between the bulk Pd-Cu foil and Pd thin film during the deposition process.
For the first time, variable temperature X-ray diffraction analysis has been performed on the surface modified foil samples between 30 and 700 °C under 100 and 445 kPa of hydrogen pressure in order to investigate the effects of these conditions on Cu interdiffusion. In general, it was found that under 445 kPa of hydrogen pressure the palladium hydride (β-PdH) phase present in the thin film is stable up to higher temperatures (225 °C) than under 100 kPa of hydrogen pressure (150 to 175 °C). In all cases, it was observed that the interstitial solid solution (α-PdH) phase present within the thin film is stable under a significantly narrower temperature range under 445 kPa of hydrogen pressure when compared to 100 kPa.