Formation and control of nanoporous Ag through electrochemical dealloying of the melt-spun Cu-Ag-Ce alloys
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s work, the ultrafine nanoporous Ag ribbons were achieved through addition of 2 at.%–6 at.% Ce into the melt-spun Cu-Ag alloys and applying different electrochemical dealloying potentials. The dendritic morphology of the ligaments in the dealloyed Cu80Ag20 alloy varied to be equiaxial due to the addition of Ce, and the pore size reduced from 200 nm to less than 60 nm. The nanoporous Ag with an average pore size of ;15 nm was obtained from the Cu74Ag20Ce6 alloy. The pore and ligament sizes of the nanoporous Ag prepared from the Cu76Ag20Ce4 alloy exhibited an increasing tendency with the increase of applied potentials, while the dealloyed Cu78Ag20Ce2 had an opposite variation. Moreover, the addition of Ce into the Cu-Ag alloys also promoted the dealloying. Nanoporous Ag exhibited the stronger enhancement of the surface enhanced Raman scattering effects with the increase of Ce contents in the precursory alloys. I. INTRODUCTION
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.121
alloy composition and dealloying conditions. Yeh et al.26 prepared nanoporous Ag with different morphology by dealloying Ag–Zn films. The precursory alloys were adjusted through manipulating the composition, deposition potential, deposition current and deposition stripping temperature. Qian27 tailored the pore size of nanoporous Au from 33 nm to 5 nm by dealloying of Ag-Au leaf at low temperature. It is generally recognized that the fast diffusion of noble atoms along alloy/electrolyte interfaces could inevitably cause the ligament coarsening.28 Therefore, it is still a great challenge to control nanoporous metals by inhibiting the ligament coarsening under mild dealloying conditions. Recently, Snyder et al.29 reported that the addition of small amounts of noble metals to precursory alloys could stabilize the morphology of nanoporous metals. Ji et al.30 prepared the nanoporous Ag with pore size of about 5 nm by adding a certain amount of Pd into the Mg-Ag precursory alloys. However, to the best of our knowledge, the preparation and control of nanoporous Ag through adding the sacrificial base metals into precursory alloys has not been reported. Our previous work31 prepared nanoporous Ag by electrochemical corrosion of the melt-spun Cu-Ag alloys at a low voltage. The ligaments of nanoporous Ag evolved from the Ag-rich phase. However, the ligament/pore sizes were dependant on the morphology of the Ag-rich phase in the precursory alloys. As a result, it is difficult to control nanoporous Ag by adjusting the corrosion parameters. The present investigation reported a novel approach to control the morphology of nanoporous Ag through adding the third element Ce into the precursory alloys combined with applied potentials. The ultrafine nanoporous Ag ribbons with granular ligaments were successfully prepared by electrochemical dealloying of the melt-spun Cu-Ag-Ce
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Ó Materials Research Society 2012
As a kind of new unsupported nanomaterials, nanoporous metals and alloys have attracted great attention in a wi
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