H Diffusion through Partially Internally Oxidized Pd-alloy Membranes (U)
In 1998 Kirchheim et al remarked that ''to their knowledge, experimental results on the diffusion of hydrogen through multi-layers have not yet been reported'' [1]. Their research dealt with diffusion through ultra-thin multi-layers of Nb/Pd which they followed electrochemically using a time-lag method. Their results were somewhat uncertain in that no final conclusion about any effect of the internal interfaces could be reached. Very recently Yamakawa et al [2] investigated Pd/Fe and Pd/Ni multilayers at 378-625 K and found no strong influence of the interfaces, however, there was grain boundary diffusion for the Pd/Ni layers and retardation, possibly due to dislocation trapping. Takano et al [3] studied H diffusion through thin layers of Pd, Ni, or Cu deposited electrochemically on Fe and concluded that complications are introduced by thin films perhaps H trapping at vacancies as the thickness of the layer decreases to very small values. Holleck [4] measured H diffusion through mm thick Pd{sub 0.75}Ag{sub 0.25}/Ta/Pd{sub 0.75}Ag{sub 0.25} layers in the gas phase from 540-873 K and determined D{sub H,Ta} from the overall diffusion constant and the known D{sub H,alloy}; he concluded that the interface did not play a significant role at these temperatures. As in Holleck's, the present research does not concern very thin multi-layers but macroscopic ones, in this case, prepared by internal oxidation. The measurements will be carried out at a lower temperature than Holleck's and with a variety of layer thicknesses. Most previous investigations have employed electrochemical time-lag methods [1,3,5,6] at ambient temperature and have assumed that the solubilities at the interfaces are in the ideal range. To our knowledge, an investigation of diffusion through layers prepared by internal oxidation has not been carried out. Partial internal oxidation of Pd-M alloys leads to outer layers of Pd containing M oxide precipitates while the inner layer remains unoxidized Pd-M alloy. The alloy employed in this research is Pd{sub 0.96}Al{sub 0.04} which was chosen because the authors have had extensive experience with its internal oxidation [7,8] and it has been shown that internally oxidized Pd-Al alloys are more resistant to poisoning by CO than pure Pd [9]. The specific Al content was chosen in order for it to be large enough for the alloy to have a significantly lower permeability than Pd but small enough to internally oxidize. The diffusion results may give some information about internal oxidation.
- Research Organization:
- Savannah River Site (SRS), Aiken, SC
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- DE-AC09-96SR18500
- OSTI ID:
- 881474
- Report Number(s):
- WSRC-MS-2005-00593; JMESDO; TRN: US200613%%465
- Journal Information:
- Journal of Membrane Science, Journal Name: Journal of Membrane Science; ISSN 0376-7388
- Country of Publication:
- United States
- Language:
- English
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Low-temperature diffusion of hydrogen in Pd-Ni solutions
NUCLEAR ENGINEERING DEPARTMENT, PROGRESS REPORT, SEPTEMBER 1-DECEMBER 31, 1960