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

Al-Mufachi, Naser Azzat (2015)
Ph.D. thesis, University of Birmingham.

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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: Ph.D. thesis. Steinberger-Wilckens, Robert and Rees, Neil Colleges (2008 onwards) > College of Engineering & Physical Sciences School of Chemical Engineering TP Chemical technology University of Birmingham 6028
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