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Title: Cost-Effective Method for Producing Self Supported Palladium Alloy Membranes for Use in Efficient Production of Coal Derived Hydrogen

Abstract

In the past quarter, no technical work has been completed and a ''no cost'' time extension was requested and granted to allow IdaTech time to complete task 5 relating to the testing of prototype membrane modules. The scheduled completion date is now October 31, 2007.

Authors:
Publication Date:
Research Org.:
Southwest Research Institute Inc
Sponsoring Org.:
USDOE
OSTI Identifier:
902895
DOE Contract Number:
FC26-03NT41849
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; 08 HYDROGEN; 36 MATERIALS SCIENCE; COAL; HYDROGEN; MEMBRANES; PALLADIUM ALLOYS; PRODUCTION; TESTING

Citation Formats

K. Coulter. Cost-Effective Method for Producing Self Supported Palladium Alloy Membranes for Use in Efficient Production of Coal Derived Hydrogen. United States: N. p., 2007. Web. doi:10.2172/902895.
K. Coulter. Cost-Effective Method for Producing Self Supported Palladium Alloy Membranes for Use in Efficient Production of Coal Derived Hydrogen. United States. doi:10.2172/902895.
K. Coulter. Sat . "Cost-Effective Method for Producing Self Supported Palladium Alloy Membranes for Use in Efficient Production of Coal Derived Hydrogen". United States. doi:10.2172/902895. https://www.osti.gov/servlets/purl/902895.
@article{osti_902895,
title = {Cost-Effective Method for Producing Self Supported Palladium Alloy Membranes for Use in Efficient Production of Coal Derived Hydrogen},
author = {K. Coulter},
abstractNote = {In the past quarter, no technical work has been completed and a ''no cost'' time extension was requested and granted to allow IdaTech time to complete task 5 relating to the testing of prototype membrane modules. The scheduled completion date is now October 31, 2007.},
doi = {10.2172/902895},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat Mar 31 00:00:00 EDT 2007},
month = {Sat Mar 31 00:00:00 EDT 2007}
}

Technical Report:

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  • Competed fabrication of an initial series of copper and palladium-copper alloy membranes in the range of 1-8 microns in thickness up to 6 inch x 8 inch in area. Films were produced using both e-beam evaporation (with and without ion assist) and magnetron sputtering from a 60%Pd/40%Cu alloy target. Pure copper and palladium-copper alloy films, with essential no intrinsic stress, were produced on both polystyrene and polyvinyl alcohol substrates. Various processing parameters and techniques were investigated in order to minimize defects and maximize uniformity in single layer films. Even though films to date are visually defect free, we are ablemore » to observe sub-micron size defects using a backlighting technique; we are currently investigating a number of methods to create a gas impermeable membrane. At present, the metal films are effectively removed from the polymer backing material by merely immersing the film in an appropriate solvent; chloroform for the polystyrene and water for the PVA. In the future we plan to investigate alternative methods for removing the polymer backing that are more suited to large scale, low-cost manufacturing.« less
  • In continuation of efforts from last quarter, processing parameters, used in the formation of Pd-Cu alloy films, were being optimized in a drum (web) coater system with the goal of producing large-area, contiguous, pinhole-free films for H{sub 2} separation membranes. Since the (pre-treatment) functionality of the surface of the plastic backing material is sub-optimal, they tended to produce films in the drum coater that were either not contiguous (disseminates upon release from the polymer backing material) or contain pinholes. Alternative approaches, such as direct deposition onto thermally oxidized silicon wafers, have been attempted to yield pinhole-free films; i.e., formation ofmore » a poorly adherent Pd-Cu film on silicon will then directly release from the silicon substrate. Permeation characteristics of a 25 {micro}m-thick, Pd{sub 60}Cu{sub 40} alloy foil were conducted. After pre-treating the sample to stabilize the FCC {beta}-phase, the hydrogen permeability was determined to be 5.4 x 10{sup -5} cm{sup 3} cmcm{sup -2}s{sup -1}cm Hg{sup -1/2}. Thin, 1-3 {micro}m-thick Pd-Cu alloy films have been prepared on PS films and samples will be prepared and tested in the next quarter.« less
  • Extending upon development efforts last quarter to produce ''free-standing'', copper and palladium alloy films, the goal this quarter has been to produce pinhole-free, Pd-Cu alloy films up to 5 x 5 inches in area (1-3 microns thick) using both magnetron sputtering and e-beam evaporation on PVA (Solublon) and polystyrene backing materials. A set of experiments were conducted to assess processing methods/solutions chemistry for removing the polymer backing material from the Pd-Cu film. For all of the alloy films produced to this point, we were unable to produce pinhole-free films on plastic although we were able to produce free-standing Pd-Cu filmsmore » at less than 0.5 microns thick with minimal intrinsic stress. Subsequently, to evaluate gas permeation and leakage across the films, two films were sandwiched together on top of a porous Monel support disc (25 mm in diameter) and then tested in a leak test apparatus. Using two Cu films (10 micron thickness total) in the sandwich configuration, leak rates were about 20% of the background leak rate.« less
  • 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 themore » 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.« less
  • Over the last quarter, we developed procedures for producing free-standing, defect free films using rigid silicon and glass substrates over areas up to 12 square inches. Since formation of contiguous Pd-Cu films in the 2-3 {micro}m-thick range is ultimately governed by the size of the particle contamination on the supporting substrate surface, we have adopted techniques utilized by the semiconductor industry to reduce and eventually eliminate particle contamination. We have found these techniques to be much more effective on rigid substrates and have made a down select decision on removal methods (a key milestone) based on these results and themore » performance of membranes fabricated by this technique. The path to fabricating even larger membranes is straightforward and will be demonstrated in the coming months. Hydrogen permeation tests were also conducted this quarter on as-deposited, Pd-Cu membranes, between 6-14 {micro}m-thick. In the case of a 6 {micro}m-thick film, the pure hydrogen flux at 20 psig and {approx}260 C was 36 cm{sup 3}(STP)/cm{sup 2} min. This flux corresponds to a pure hydrogen permeability of 7.4 {center_dot} 10{sup -5} cm{sup 3} cm cm{sup -2} s{sup -1} cm Hg{sup -1/2} at 250 C. This value is within 20% of the pure hydrogen permeability at 250 C reported in the McKinley patent. In the case of a 14 {micro}m-thick membrane tested at 350 C, the pure hydrogen flux, measured before initiating a pinhole-size leak, was 2.1 {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}. This value is considerably lower than the expected permeability of Pd{sub 60}Cu{sub 40} materials at 400 C. To date, essentially all of the sputtered deposited Pd-Cu thin film membranes have had palladium compositions that were as much as 3% greater than the ideal 60 weight percent composition (this is a direct consequence of sputtering from a 60/40, Pd/Cu alloy target). As the concentration of Pd is increased beyond the optimum 60% value, a less desirable two-phase structure forms at the higher temperatures (in this case, above 260-280 C). As we continue development of procedures for producing thinner Pd-Cu films next quarter, we will also be optimizing alloy composition and corresponding hydrogen permeation flux as well.« less