Dealloying Behavior of Dual-Phase Al 40 atom % Cu Alloy in an Alkaline Solution

Abstract

To further understand the underlying physical mechanisms of dealloying of multiphase alloys and control dissolution processes among different phases, the dealloying behavior of melt-spun Al 40 atom % Cu alloy comprising Al 2 Cu and AlCu intermetallic compounds in a 10 wt % sodium hydroxide ͑NaOH͒ aqueous solution was studied. The microstructure of as-dealloyed samples was characterized using x-ray diffraction, scanning electron microscopy, and energy dispersive x-ray analysis. The experimental results show that the alloy with the amount of Al 2 Cu comparable to that of AlCu can be partially dealloyed, which eventually results in the formation of a unique kind of nanoporous copper/AlCu composite. Additionally, the formation mechanism has been well established to describe the morphology and composition evolutions during the dealloying process based upon kinetic competitions between dissolution of Al atoms and diffusion-rearrangement of Cu atoms, which includes three stages, sequentially, defined as "Al 2 Cu dealloying," "AlCu dealloying," and "coarsening accompanying underlying AlCu re-dealloying." © 2010 The Electrochemical Society. ͓DOI: 10.1149/1.3511771͔ All rights reserved.Manuscript submitted September 13, 2010; revised manuscript received October 13, 2010. Published December 16, 2010 Nanoporous metals with large surface area have recently attracted considerable interest in a wide variety of applications including catalysis, sensors, actuators, fuel cells, microfluidic flow controllers, and so forth.1-4 For a long time, template methods are commonly used to fabricate these materials through the replication of porous alumina or liquid-crystal templates. [5][6][7] Because it has been found that dealloying can be used to yield a broad range of porous metals, during recent decades, a great deal of effort has been directed toward the investigation of nanoporous metals prepared through dealloying. [8][9][10][11] However, most of the previously reported porous metals were fabricated by dealloying from binary/ternary alloy systems with a single-phase solid solubility across all compositions, which refer to selective dissolution of one or more active components out of an alloy, such as Cu-Pt, Ag-Au, Cu-Au, and Au-Ag-Pt. [12][13][14][15] In view of their industrial applications, widespread uses of a dealloying technique to make nanoporous metals are frequently hindered by the high cost of these noble metals and limited alloy systems. Thus, the fabrication of nanoporous materials from alloy families based on common metals with multiple phases urgently needs to be investigated.However, a few substantial researches have so far focused on this topic using an electrochemical/chemical dealloying technique because of the difficulties in clarifying dealloying behavior and controlling the dissolution process among different phases in multiphase alloys. 16 Recently, Qi et al. 17 reported that the uniform nanoporous copper ͑NPC͒ with a pore size of several hundred nanometers can be synthesized from dual-phase Al-Cu alloys with a ...

Dealloying solution dependence of fabrication, microstructure and porosity of hierarchical structured nanoporous copper ribbons

“…It is known that surface diffusion of more noble (MN) element along alloy/solution interfaces plays a key role in the formation of NPMs and has a significant influence on the length scales of ligaments/channels [5,25]. It has been found that during the dealloying of Al-based alloys in alkali solution, surface diffusivity of the MN atoms is much slower than that in acid media due to the formation of MN-hydroxy species, the interaction of MN atoms and OH À , and the low solubility of AlO 2 À [29][30][31][32]. On the other hand, the adsorption of chloride ion (Cl À ) in acidic solution can greatly enhance the surface diffusion of MN atoms along alloy/solution interfaces during dealloying due to modification of adsorbed bonds between neighboring sites via electron transfer reactions [10,18,33,34].…”

Elaboration of nanoporous copper by modifying surface diffusivity by the minor addition of gold

“…Generally, the dominant length scale of the final porous structure depends on the initial microstructure [11][12][13][14][15][16]. The nature of the amorphous alloys is in short range order and is not periodic [35].…”

“…Dealloying is a process which originated from the phenomenon of selective corrosion, and it has been attracting attention recently as an effective method to fabricate nanoporous metals with a three-dimensional (3D) bi-continuous interpenetrating pore-toligament structure at the nanometer scale [5][6][7][8]. Dealloying has been observed in numerous binary alloy systems including the systems: Zn-Cu [7,9], Mg-Cu [10], Al-Cu [7,[11][12][13][14][15][16], Ni-Cu [7], Mn-Cu [17,18], Zr-Cu [19] and Ti-Cu [20].…”

“…The presence of intermetallics or second phases has been shown to facilitate the formation of a bimodal nanoporous structure from crystallized Al-Cu alloys systems [11][12][13][14][15][16]. As has been reported, nanoporous Cu was fabricated from amorphous Ti-Cu alloy systems [20] in HF solutions.…”

Preparation and characterization of nanoporous Cu6Sn5/Cu composite by chemical dealloying of Al–Cu–Sn ternary alloy

“…Lu et al [16] reported that porous copper can be synthesized from nanocrystalline two phases Cu-Zr films by electrochemical dealloying. Liu et al [17] reported the synthesis of monolithic nanoporous copper by chemical dealloying Al-Cu alloy composed of Al 2 Cu and AlCu intermetallic compounds. It has also been reported that nanoporous Pt thin film on Si can be obtained by electrochemical dealloying of amorphous Pt x Si 1-x alloy in aqueous HF solutions [18].…”