COST-EFFECTIVE METHOD FOR PRODUCING SELF SUPPORTED PALLADIUM ALLOY MEMBRANES FOR USE IN EFFICIENT PRODUCTION OF COAL DERIVED HYDROGEN

To overcome the issue of pinhole (defect) formation in membrane films over large areas, a process was developed and implemented for producing 6-12 {micro}m-thick, Pd-Cu alloy films on thermally oxidized silicon wafer substrates. The processing parameters on silicon are such that adhesion is poor and as-deposited Pd-Cu alloy films easily release from the oxidized silicon surface. Hydrogen permeation tests were conducted on 9 and 12 {micro}m-thick Pd-Cu alloy films and the hydrogen flux for 9 and 12 {micro}m-thick films were 16.8 and 8 cm{sup 3}(STP)/cm{sup 2} {center_dot} min respectively. The hydrogen permeability (corrected using data in McKinnley patent) of the 9 {micro}m-thick membrane is 7.4 {center_dot} 10{sup -5} cm{sup 3}(STP) {center_dot} cm/cm{sup 2} {center_dot} s {center_dot} cm Hg{sup 0.5} at 350 C and compares very well to permeability reported by McKinnley for a 62.5% Pd membrane; this permeability is {approx}56% of the value reported for a Pd-Cu alloy membrane with optimum 60% Pd composition. Using XRD, we confirmed the presence of a two-phase, {alpha}/{beta}, structure and that the composition of our membrane was slightly higher than the optimum composition. We are making adjustments to the compositions of the Pd-Cu alloy target in order to produce films next quarter that match the ideal Pd{sub 60}Cu{sub 40} composition