Effects of palladium thin films on the hydrogen permeability of Pd-Cu alloy membranes

Al-Mufachi, Naser Azzat (2015). Effects of palladium thin films on the hydrogen permeability of Pd-Cu alloy membranes. University of Birmingham. Ph.D.

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Abstract

The hydrogen permeability of surface modified Pd\(_6\)\(_0\) Cu\(_4\)\(_0\) wt% (Pd\(_4\)\(_7\)\(.\)\(_3\)Cu\(_5\)\(_2\)\(_.\)\(_7\)at%) membranes have been determined for the first time. Surface modification was accomplished through the deposition of Pd thin films of three different thicknesses (95.5 ± 0.1, 797.4 ± 0.2 and 1,409.6 ± 0.2 nm) on to one side of a range of as-received Pd\(_6\)\(_0\) Cu\(_4\)\(_0\) wt% membrane coated with a 1,409.6 ± 0.2 nm thick Pd thin film positioned on the feed side (445 kPa of hydrogen pressure) and cycled between 50 and 450 °C achieved the highest hydrogen permeability of 1.09 x 10\(^-\)\(^8\) mol m\(^-\)\(^1\) s\(^-\)\(^1\) Pa\(^-\)\(^0\)\(^.\)\(^5\) at 450 °C during the third cycle. This is a 58% increase on the value measured for the as-received Pd\(_6\)\(_0\) Cu\(_4\)\(_0\) wt% 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.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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