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Cost-Effective Method for Producing Self Supported Palladium Alloy Membranes for Use in Efficient Production of Coal Derived Hydrogen Quarterly Technical Progress Report: September 2003-January 2006

Description: In the past quarter, significant progress has been made in optimize the deposition and release characteristics of ultrathin (less than 4 micron) membranes from rigid silicon substrates. Specifically, we have conducted a series of statistically designed experiments to examine the effects of plasma cleaning and compliant layer deposition conditions on the stress, release and pinhole density of membranes deposited on 4 inch and 6 inch round substrates. With this information we have progressed to the deposition and release of ultra-thin membranes from 12-inch diameter (113 sq. in.) rigid substrates, achieving a key milestone for large-area membrane fabrication. Idatech received and is beginning preparations to test the Pd alloy membranes fabricated at SwRI the previous quarter. They are currently evaluating alternate gasketing methods and support materials that will allow for effective sealing and mounting of such thin membranes. David Edlund has also recently left Idatech and Bill Pledger (Chief Engineer) has replaced him as the primary technical point of contact. At Idetech's request a small number of additional 16 sq. in, samples were provided in a 2 in. by 8 in. geometry for use in a new module design currently under development. Recent work at the Colorado School of Mines has focused on developing preconditioning methods for thin Pd alloy membranes (6 microns or less) and continuing tests of thin membranes produced at SwRI. Of particular note, a 300-hour short-term durability study was completed over a range of temperatures from 300-450 C on a foil that showed perfect hydrogen selectivity throughout the entire test. With a 20 psi driving force, pure hydrogen flow rates ranged from 500 to 700 cc/min. Calculated at DOE specified conditions, the H{sub 2} flux of this membrane exceeded the 2010 Fossil target value of 200 SCFH/ft{sup 2}.
Date: January 1, 2006
Creator: Arps, J.

Cost-Effective Method for Producing Self Supported Palladium Alloy Membranes for Use in Efficient Production of Coal Derived Hydrogen Quarterly Technical Progress Report: September 2003-July 2005, Revised

Description: Efforts in this quarter were concentrated on developing vacuum processing procedures to produce thinner (<4 {micro}m-thick), defect-free films over larger areas (>100 cm{sup 2}). We continued to test three different types of rigid supporting substrates, thermally oxidized silicon (10 cm diameter), polished borosilicate glass (10 cm diameter), and soda-lime glass (>100 cm{sup 2} areas), each representing a different cost, surface roughness, and chemistry. Mechanical integrity, defect density, and release characteristics of the films, though similar for the oxidized silicon and borosilicate glass, were distinctly different for the inexpensive soda-lime (float) glass; i.e., more sensitive to surface impurities. In general, films less than 4 {micro}m-thick were shown to be very sensitive to surface condition of the supporting substrate, particularly in the case of the soda-lime glass, to the point where surface strain overrode and dominated the intrinsic bulk stresses that are produced during the growth process. Therefore, in the near term (over the next quarter), large area films (>100 cm{sup 2}) will be produced at a minimum thickness of 5 {micro}m while further development will be conducted in subsequent quarters to reduce membrane thickness in large area films. Continued hydrogen permeation experiments and characterization of 5 and 10 {micro}m-thick, Pd-Cu films, with compositions near the 60/40 (Pd/Cu phase boundary) in combination with air oxidation treatments to improve performance. Pure hydrogen permeability for an as-received, 5 {micro}m film at 400 C was determined to be 1.3 x 10{sup -4} cm{sup 3}(STP) {center_dot} cm/cm{sup 2} {center_dot} s {center_dot} cmHg{sup 0.5} at steady state. Even a membrane {approx} 10 {micro}m-thick, exhibited a steady state hydrogen flux of 32 cm{sup 3}(STP)/cm{sup 2}min after air exposure, which, when normalized for DOE's Office of Fossil Energy's specified hydrogen flux with a {Delta}P of 100 psi and a permeate pressure of 50 psia, results in a flux of …
Date: August 31, 2005
Creator: Lanning, B. & Arps, J.

Cost-Effective Method for Producing Self Supported Palladium Alloy Membranes for Use in Efficient Production of Coal Derived Hydrogen Quarterly Technical Progress Report: September 2003-September 2005

Description: During the last quarter, new procedures were developed and implemented to improve reliability and repeatability of release characteristics from the temporary substrate (i.e., silicon wafer) and to minimize through-thickness defects in a 6-inch diameter film, 3 microns in thickness. With the new procedures, we have been able to consistently produce essentially stress free films, with zero or minimal defects (less than 5) across a 6-inch diameter area. (It is important to note that for those films containing pinholes, a procedure has been developed to repair the pinholes to form a gas tight seal). The films are all within the identified tolerance range for composition (i.e., 60 {+-} 0.2 % Pd). A number of these films have subsequently been shipped to IdaTech for evaluation and integration into their test module. Colorado School of Mines continued their high temperature evaluation of 6 micron thick, sputtered Pd-Cu films. Pure hydrogen permeability increased up to 400 C while the membrane was in the {beta}-phase and dropped once the temperature increased to over 450 C. Above this temperature, as confirmed by the binary phase diagram, the film transforms into either a mixed {alpha}/{beta} or pure {alpha} phase. The same trend was observed for a baseline 25 micron-thick foil (from Wilkinson) where the pure hydrogen permeability increased with temperature while the membrane was in the {beta}-phase and then decreased upon transformation to the {alpha} phase.
Date: October 28, 2005
Creator: Lanning, B. & Arps, J.
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