Monolithic nanoporous copper (NPC) ribbons can be fabricated through chemical dealloying of melt-spun Al-Cu alloys with 33-50 at % Cu under free corrosion conditions. The microstructure of these NPC ribbons was characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, and transmission electron microscopy. The experimental results show that the melt-spun Al-Cu alloys with 33-50 at % Cu are composed of one or a combination of Al 2 Cu and AlCu intermetallic compounds. Both Al 2 Cu and AlCu can be fully dealloyed, and the synergetic dealloying of Al 2 Cu and AlCu in the two-phase Al-Cu alloys results in the formation of NPC with a homogeneous porous structure. The NPC ribbons exhibit an open, bicontinuous interpenetrating ligament-channel structure. NPC is a promising high strength/low density material due to its high porosity and yield strength of 86 ( 10 MPa. In addition, bulk NPC rods and slices can also be synthesized using the same strategy. These NPC ribbons, rods, and slices can serve as model materials to investigate the mechanical, physical (for example, electrical resistivity), and chemical properties associated with random porous structure of nanoporous solids.

We present a facile and effective route to fabricate monolithic nanoporous silver (NPS) ribbons through chemical dealloying of melt-spun Al-Ag alloys comprising R-Al(Ag) and Ag 2 Al under free corrosion conditions. The microstructure of the NPS ribbons was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray analysis (EDX). The experimental results show that alloy composition and dealloying solution have a significant influence on the dealloying process and the formation of NPS. The Al-Ag alloys with 15-40 atom % Ag can be fully dealloyed in the 5 wt % HCl solution, but a minor amount of undealloyed Ag 2 Al can be detected in the as-dealloyed ribbons from the Al-45 and 50 Ag alloys. The existence of R-Al(Ag) can supply penetration paths for the solution and promote the dealloying of Ag 2 Al in the two-phase Al-Ag alloys. Moreover, the synergetic dealloying of R-Al(Ag) and Ag 2 Al in the two-phase Al-Ag alloys and fast surface diffusion of Ag result in the formation of NPS with a homogeneous porous structure. The Al-Ag alloys with 15-50 atom % Ag cannot be fully dealloyed in the 20 wt % NaOH solution, leading to the formation of NPS/Ag 2 Al composites. In addition, the Al-60 Ag alloy containing a single Ag 2 Al phase does not react with the 5 wt % HCl or 20 wt % NaOH solution even at high temperatures (90 ( 5°C). IntroductionNanoporous materials have attracted great interest for their wide applications in catalysis, 1-3 gas sensors, 4-6 heat exchangers, 7 supercapacitors, 8 and so on, because of their novel physical, chemical, and mechanical properties associated with their high surface-to-volume ratio and low densities.Nanoporous metal materials can be prepared by metal organic deposition and liquid crystal template technique, 9,10 but they are generally technically difficult and time-consuming to be implemented. Recently, chemical and electrochemical dealloying is usually used to fabricate nanoporous metals by selective dissolution of less noble elements from an alloy because of its high productivity and controllability. Taking the dealloying of a binary A x B 1-x alloy (here, A is a less noble element, and B is a more noble element) in the electrolyte as an example, A will be dissolved from the alloy while B remains. Following the dissolution process of A, the residual B will gradually agglomerate and form a nanoporous structure throughout the dimensions of the sample.Although different alloy systems such as Ni-Al, 11 Cu-Au, 12 Pt-Cu, 13 and Pt-Si 14 have been used to study the dealloying process and the formation of nanoporous metals, most attention has been paid to the prototypical Ag-Au system. [15][16][17][18] In contrast, little information is available on the synthesis of monolithic nanoporous silver (NPS) through dealloying. To date, the research on the preparation of NPS has merely focused on the electrochemical alloying/dealloying process. Jia et al. 19 and Yeh et al. 20 independently succeeded in the fabric...

No abstract

No abstract

In this paper, the influence of alloy composition, dealloying solution and elemental doping on the dealloying process of rapidly solidified Mg-Ag based alloys and the formation of nanoporous silver (NPS) has been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and transmission electron microscopy (TEM). The results show that NPS and nanoporous silver-palladium (NPS-Pd) alloys can be fabricated by dealloying the Mg-Ag based alloys in acid media under free corrosion conditions. The NPS and NPS-Pd exhibit an open, three-dimensional bicontinuous interpenetrating ligament-channel structure. Furthermore, alloy composition and phase constitution of the Mg-Ag precursors have a significant influence on the ligament/channel size and the formation of cracks in NPS. The length scales of ligaments/channels in NPS can be tuned by simply changing the dealloying solution. Crack-free NPS with good mechanical integrity and small ligament/channel sizes can be obtained by dealloying the Mg-Ag alloys in suitable acid solutions. Moreover, the addition of Pd into Mg-Ag has a significant influence on the dealloying process and results in the formation of ultrafine bimodal NPS-Pd with ligaments/channels of $5 nm. The NPS-Pd alloy shows excellent hydrogen sensing properties with stable sensitivity, fast response and low detection limit. Our present findings provide implications for control and functionalization of nanoporous metals or alloys by alloy design, selection of dealloying media and elemental doping.