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Microstructural Investigation and On-Site Repair of Thin Pd-Ag Alloy Membranes

Pd membranes act in an important role in H2 purification and H2 production in membrane reactors. Pd-Ag alloy membranes fabricated by consecutive electroless- and electroplating process on alumina tubes exhibited good stability under stringent heating/cooling cycles at a ramp rate of 10 K/min, imitat...

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Autores principales: Ma, Yuyu, Tang, Chunhua, Bao, Feng, Shao, Wei, Xu, Tianying, Li, Hui, Xu, Hengyong
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7760571/
https://www.ncbi.nlm.nih.gov/pubmed/33266176
http://dx.doi.org/10.3390/membranes10120384
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author Ma, Yuyu
Tang, Chunhua
Bao, Feng
Shao, Wei
Xu, Tianying
Li, Hui
Xu, Hengyong
author_facet Ma, Yuyu
Tang, Chunhua
Bao, Feng
Shao, Wei
Xu, Tianying
Li, Hui
Xu, Hengyong
author_sort Ma, Yuyu
collection PubMed
description Pd membranes act in an important role in H2 purification and H2 production in membrane reactors. Pd-Ag alloy membranes fabricated by consecutive electroless- and electroplating process on alumina tubes exhibited good stability under stringent heating/cooling cycles at a ramp rate of 10 K/min, imitating practical fast initiation or emergency shutdown conditions. Bilayer Pd-Ag membranes can form dense and uniform alloy after thermal treatment for 24 h at 823 K under H2 atmosphere, despite a porous structure due to the development of liquid-like properties above Tamman temperature to enforce the migrativity. On the contrary, alloying under N2 atmosphere resulted in a Pd-enriched layer. This led to a lower H2 flux but superior thermal stability compared to that alloying under H2 atmosphere. The trilayer approach of electroless-plated Pd, electro-polated Ag and electroless-plated Pd is not suitable to achieve homogeneous Pd-Ag alloys, which, on the other hand, presented the occurrence of a small gap between top Pd layer and middle Ag layer, probably due to insufficient wetting during plating process. An on-site repair treatment in analogous to MOCVD (Metal-organic Chemical Vapor Deposition) process was first proposed to extend the lifetime of Pd-Ag membrane, i.e., by vaporizing, and subsequent decomposition of Ag(OOCC2F5) powders to “preferentially” block the pinholes under vacuum and at working temperature of ca. 473–673 K, which effectively reduced the N2 flux by 57.4% compared to the initial value. The H2 flux, however, declined by 16.7% due to carbon deposition on the membrane surface, which requires further investigation. This approach shows some potential for on-site repair without disassembly or cooling to room temperature.
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spelling pubmed-77605712020-12-26 Microstructural Investigation and On-Site Repair of Thin Pd-Ag Alloy Membranes Ma, Yuyu Tang, Chunhua Bao, Feng Shao, Wei Xu, Tianying Li, Hui Xu, Hengyong Membranes (Basel) Article Pd membranes act in an important role in H2 purification and H2 production in membrane reactors. Pd-Ag alloy membranes fabricated by consecutive electroless- and electroplating process on alumina tubes exhibited good stability under stringent heating/cooling cycles at a ramp rate of 10 K/min, imitating practical fast initiation or emergency shutdown conditions. Bilayer Pd-Ag membranes can form dense and uniform alloy after thermal treatment for 24 h at 823 K under H2 atmosphere, despite a porous structure due to the development of liquid-like properties above Tamman temperature to enforce the migrativity. On the contrary, alloying under N2 atmosphere resulted in a Pd-enriched layer. This led to a lower H2 flux but superior thermal stability compared to that alloying under H2 atmosphere. The trilayer approach of electroless-plated Pd, electro-polated Ag and electroless-plated Pd is not suitable to achieve homogeneous Pd-Ag alloys, which, on the other hand, presented the occurrence of a small gap between top Pd layer and middle Ag layer, probably due to insufficient wetting during plating process. An on-site repair treatment in analogous to MOCVD (Metal-organic Chemical Vapor Deposition) process was first proposed to extend the lifetime of Pd-Ag membrane, i.e., by vaporizing, and subsequent decomposition of Ag(OOCC2F5) powders to “preferentially” block the pinholes under vacuum and at working temperature of ca. 473–673 K, which effectively reduced the N2 flux by 57.4% compared to the initial value. The H2 flux, however, declined by 16.7% due to carbon deposition on the membrane surface, which requires further investigation. This approach shows some potential for on-site repair without disassembly or cooling to room temperature. MDPI 2020-11-30 /pmc/articles/PMC7760571/ /pubmed/33266176 http://dx.doi.org/10.3390/membranes10120384 Text en © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Ma, Yuyu
Tang, Chunhua
Bao, Feng
Shao, Wei
Xu, Tianying
Li, Hui
Xu, Hengyong
Microstructural Investigation and On-Site Repair of Thin Pd-Ag Alloy Membranes
title Microstructural Investigation and On-Site Repair of Thin Pd-Ag Alloy Membranes
title_full Microstructural Investigation and On-Site Repair of Thin Pd-Ag Alloy Membranes
title_fullStr Microstructural Investigation and On-Site Repair of Thin Pd-Ag Alloy Membranes
title_full_unstemmed Microstructural Investigation and On-Site Repair of Thin Pd-Ag Alloy Membranes
title_short Microstructural Investigation and On-Site Repair of Thin Pd-Ag Alloy Membranes
title_sort microstructural investigation and on-site repair of thin pd-ag alloy membranes
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7760571/
https://www.ncbi.nlm.nih.gov/pubmed/33266176
http://dx.doi.org/10.3390/membranes10120384
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