skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: DIFFUSION OF H THROUGH PD MEMBRANES EFFECTS OF NON-IDEALITY ON DH AND ED

Abstract

H diffusion constants, D{sub H}, have been obtained from steady-state fluxes across Pd membranes with the downstream side maintained at p{sub H2} {approx} 0. Good linearity of plots of H flux versus (1/d), where d is the thickness, attests to the H permeation being bulk diffusion controlled in this temperature (423 to 523K) and p{sub H2} range ({le} 0.2 MPa). D{sub H} values have been determined at constant p{sub up} and also at constant (H/Pd)=r conditions. H fluxes through Pd membranes with three different surface treatments have been investigated (polished (un-oxidized), oxidized, and palladized) in order to determine the effects of these pretreatments. The palladized and oxidized membranes give similar D{sub H} values but the polished membranes give values about 12% lower. For diffusion in a concentration gradient D{sub H}*(c{sub H}/RT)(d{mu}{sub H}/dx) is the more proper description, where c{sub H} is the H concentration, rather than D{sub H}(dc{sub H}/dx) where D{sub H} and D{sub H}* are the concentration-dependent and independent diffusion constants. D{sub H}* can be obtained from D{sub H} using the thermodynamic factor, D{sub H}(r) = D{sub H}*({partial_derivative}lnp{sub H2}{sup 1/2}/{partial_derivative}lnr){sub T} = D{sub H}*f(r). In the commonly employed situation where there is a large difference in concentrations between themore » upstream and downstream sides of a membrane, the thermodynamic factor varies with distance through the membrane and this should be allowed for in obtaining D{sub H}*. Procedures are given and utilized for using D{sub H}(c{sub H}) to determine D{sub H}* values when there is a large concentration gradient through the membrane. Activation energies for diffusion, E{sub D}(c{sub H}), have been determined. E{sub D} is found to increase with c{sub H} which can be attributed to the thermodynamic factor. D{sub H}* values have been found to increase with H content.« less

Authors:
Publication Date:
Research Org.:
SRS
Sponsoring Org.:
USDOE
OSTI Identifier:
901095
Report Number(s):
WSRC-STI-2007-00125
Journal ID: ISSN 0925-8388; JALCEU; TRN: US200713%%62
DOE Contract Number:  
DE-AC09-96SR18500
Resource Type:
Journal Article
Resource Relation:
Journal Name: J. of Alloys and Compounds or J. of Membrane Science
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; DIFFUSION; MEMBRANES; SURFACE TREATMENTS; THERMODYNAMICS; THICKNESS; HYDROGEN; MEMBRANE TRANSPORT; PALLADIUM

Citation Formats

Shanahan, K. DIFFUSION OF H THROUGH PD MEMBRANES EFFECTS OF NON-IDEALITY ON DH AND ED. United States: N. p., 2007. Web.
Shanahan, K. DIFFUSION OF H THROUGH PD MEMBRANES EFFECTS OF NON-IDEALITY ON DH AND ED. United States.
Shanahan, K. Fri . "DIFFUSION OF H THROUGH PD MEMBRANES EFFECTS OF NON-IDEALITY ON DH AND ED". United States. doi:. https://www.osti.gov/servlets/purl/901095.
@article{osti_901095,
title = {DIFFUSION OF H THROUGH PD MEMBRANES EFFECTS OF NON-IDEALITY ON DH AND ED},
author = {Shanahan, K},
abstractNote = {H diffusion constants, D{sub H}, have been obtained from steady-state fluxes across Pd membranes with the downstream side maintained at p{sub H2} {approx} 0. Good linearity of plots of H flux versus (1/d), where d is the thickness, attests to the H permeation being bulk diffusion controlled in this temperature (423 to 523K) and p{sub H2} range ({le} 0.2 MPa). D{sub H} values have been determined at constant p{sub up} and also at constant (H/Pd)=r conditions. H fluxes through Pd membranes with three different surface treatments have been investigated (polished (un-oxidized), oxidized, and palladized) in order to determine the effects of these pretreatments. The palladized and oxidized membranes give similar D{sub H} values but the polished membranes give values about 12% lower. For diffusion in a concentration gradient D{sub H}*(c{sub H}/RT)(d{mu}{sub H}/dx) is the more proper description, where c{sub H} is the H concentration, rather than D{sub H}(dc{sub H}/dx) where D{sub H} and D{sub H}* are the concentration-dependent and independent diffusion constants. D{sub H}* can be obtained from D{sub H} using the thermodynamic factor, D{sub H}(r) = D{sub H}*({partial_derivative}lnp{sub H2}{sup 1/2}/{partial_derivative}lnr){sub T} = D{sub H}*f(r). In the commonly employed situation where there is a large difference in concentrations between the upstream and downstream sides of a membrane, the thermodynamic factor varies with distance through the membrane and this should be allowed for in obtaining D{sub H}*. Procedures are given and utilized for using D{sub H}(c{sub H}) to determine D{sub H}* values when there is a large concentration gradient through the membrane. Activation energies for diffusion, E{sub D}(c{sub H}), have been determined. E{sub D} is found to increase with c{sub H} which can be attributed to the thermodynamic factor. D{sub H}* values have been found to increase with H content.},
doi = {},
journal = {J. of Alloys and Compounds or J. of Membrane Science},
number = ,
volume = ,
place = {United States},
year = {Fri Mar 09 00:00:00 EST 2007},
month = {Fri Mar 09 00:00:00 EST 2007}
}