Characterization and Functional Applications of Nanoporous Ag Foams Prepared by Chemical Dealloying
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INTRODUCTION
NANOPOROUS foams have been developed in many areas due to their high specific surface area as well as disordered pore structure.[1–3] Nanoporous foams can be fabricated in a variety of materials such as polymers, ceramics, and metals.[4–7] Because it is more expensive to fabricate the nanoporous metal foams since the noble Au, Pt, and Pd elements are usually used, more studies have been performed on the polymer and ceramic-based nanoporous foams.[5–8] Though nanoporous metals foams have high electric and thermal conductivity, corrosion resistance, sufficient strength, fatigue resistance, etc., the developments are still in the early stages, such as the investigations of the catalyst and electrode.[9–11] Selective removal of one or two components from a composite involving several process methods such as chemical dealloying, electrochemical dealloying, and powder sintering has become a routine technique of rapid and direct generation of nanoporous metals foams.[12–15] Many studies have reported the ways to control the ligament size of nanoporous metals, such as adding surfactants to the etching solution, controlling the applied potential of low-temperature dealloying, electrochemical dealloying, post-dealloying annealing, and adding a third element to affect the T.Y. WU and Y.Y. CHU, MS Students, J.C. HUANG, National Chair Professor, W.Y. TSAI and S.Y. CHEN, Ph.D Students, are with the Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, ROC. Contact e-mail: [email protected] X. WANG, Joint Visiting Professor, is with the Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, and also with the School of Mechanical Engineering, Liaoning Shihua University, Fushun 113001, P. R. China. X. H. DU, Joint Visiting Professor, is with the Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, and also with the School of Materials Science and Engineering, Shenyang Aerospace University, Shenyang 110034, P. R. China. Manuscript submitted February 22, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
surface diffusion of the more noble element.[16–18] Among these methods, chemical dealloying is generally regarded as the cheapest and simplest method, which proceeds through the preferential etching of one of the constituents in a parent alloy. The remaining element may form a uniform and an open channel porous structure. Because the release of silver ions are also known as activate-systems of alkenes, alkynes and allenes, Ag is economically more attractive and better catalytic agent than other noble metals such as Au and Pt.[19] In addition, Ag and Ag alloys have shown excellent and unique properties, thus replacing the noble metals of nanoporous foams. Accordingly, in this study, we try to fabricate nanoporous Ag foams by simple chemical dealloying from the Al-Ag precursor ribbons. The emphasis of this study is to investigate the mechanical properties and to explore the functional applications of the r
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