Effects of thin film Pd deposition on the hydrogen permeability of Pd60Cu40 wt% alloy membranes

AbstractPd60Cu40 wt% (Pd47.3Cu52.7 at%) membranes were surface modified by depositing Pd thin films of three different thicknesses (~100, 800 and 1400nm) on to one side of a range of as-received Pd60Cu40 wt% cold-rolled foils via magnetron sputtering. The hydrogen permeability of the membranes was then measured and compared to the uncoated material. The Pd60Cu40 wt% membrane coated with a 1400nm thick Pd thin film positioned on the feed side (445kPa of hydrogen pressure) during hydrogen permeability measurements and cycled between 50 and 450°C achieved the highest hydrogen permeability of 1.09×10−8molm−1s−1Pa−0.5 at 450°C in the third cycle. This is a 58% increase on the value measured for the as-received Pd60Cu40 wt% membrane under the same conditions.This improvement can be attributed to a Pd-rich Pd–Cu face centred cubic (FCC) phase forming through interdiffusion between the Pd thin film and bulk Pd–Cu membrane as a result of the test conditions used during hydrogen permeability measurements. This introduces a larger hydrogen concentration gradient across the membrane due to the relatively high hydrogen solubility of the Pd-rich Pd–Cu FCC phase resulting in the observed increase in permeability.The Pd60Cu40 wt% membranes coated with a ~1400nm and ~800nm thick Pd thin film retained an almost pure Pd surface throughout cycling between 50 and 450°C with a feed and permeate hydrogen pressure of 445 and 100kPa, respectively. For the deposition technique and test conditions used throughout this work, these surface modified Pd–Cu membranes appear to stabilise the Pd thin films upon cycling across the critical temperature of 295 °;C

Numerical study on a two-stage metal hydride hydrogen compression system

A multistage Metal Hydride Hydrogen Compression (MHHC) system uses a combination of hydride materials in order to increase the total compression ratio, whilst maximizing the hydrogenation rate from the supply pressure at each stage. By solving the coupled heat, mass and momentum conservation equations simultaneously the performance of a MHHC system can be predicted. In the current work a numerical model is proposed to describe the operation of a complete compression cycle. Four different MHHC systems are examined in terms of maximum compression ratio, cycle time and energy consumption and it was found that the maximum compression ratio achieved was 22:1 when operating LaNi5 (AB5-type) and a Zr–V–Mn–Nb (AB2-type intermetallic) as the first and second stage alloys respectively in the temperature range of 20°C (hydrogenation) to 130°C (dehydrogenation)

A novel Pd–Cu–Zr hydrogen separation membrane with a high tolerance to sulphur poisoning

The effects of the addition of small amount of Zr (less than 2 at%) to the fcc phase of the Pd–Cu hydrogen separation alloy were investigated.</p