Formation of nanoporous copper through dealloying of dual-phase Cu-Mn-Al alloy: The evolution of microstructure and comp
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eestanding bulk nanoporous copper with ultralow density has been fabricated through dealloying of as-cast dual-phase Cu1Mn1Al8 alloy, and the dealloying behavior was investigated systematically. The experimental results show that due to different electrochemical activities, the Al11Cu5Mn3 phase of the dual-phase precursor alloy dissolved before AlCu2Mn, which corresponds to the dramatical evolutions of microstructure and composition. Additionally, a formation pattern based upon a mechanism combined “dissolution–redeposition” pattern, “phase-separation” pattern, and “coarsening” process has been built to describe the evolution process, which includes four stages, sequentially defined as “dissolution of Al11Cu5Mn3,” “redeposition of Cu atoms,” “dealloying of AlCu2Mn,” and “coarsening.”
I. INTRODUCTION
Nanoporous metals (NPMs), with high surface area, low density, and high strength,1–3 have received considerable attention on the applications of catalysis, biotechnology, sensors, actuators, fuel cells, surface enhanced Raman scattering (SERS), etc.4–7 Since dealloying was a simple, spontaneous, and effective way to prepare NPMs,8 a great deal of efforts have been devoted to this method. For a long time, lots of attention have been drawn on the dealloying behavior of single-phase solid solution alloys with solubility across all composition such as Au–Ag,9–13 Au–Cu,14 Cu–Mn,15 Cu–Ni,16,17 Cu–Pt,18 Au–Ag–Pt,19 and so on, which could generally yield ideal three-dimensional (3D) bicontinuous nanoporous structures. However, the main challenge of this approach is the difficulty to prepare single-phase solid solution due to the existence of miscibility gap in most alloy systems. Simultaneously, a few works on dealloying of amorphous alloys have also been reported, such as Pd–Ni–P,20 Al–Cu–Mg,21 and Cu–Cr–Ti.22 However, this approach has also been largely limited due to the difficulty of preparing amorphous precursor alloys. Therefore, the preparation of NPMs from the alloy systems with common components and multiple phases needs to be investigated urgently. Up to date, a lot of literatures on dealloying behavior of multiphase alloys have been published and most of which are binary alloys. For example, Lu et al.23 have reported that NPC can be successfully fabricated through electrochemical dealloying of nanocrystalline two-phase Cu–Zr film. Wang et al.24 have claimed successful preparation
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.307 J. Mater. Res., Vol. 27, No. 21, Nov 14, 2012
of nanoporous silver from dual-phase Al–Ag alloy. Many other multiphase alloy systems were also reported, such as Al–Cu,25–28 Mg–Cu,29,30 Al–Au,31 and so forth. It has been claimed that different from the dealloying of single-phase solid solution and amorphous alloys, the divergence between different phases leads to markedly complicated structure evolution processes during the dealloying of dual-phase Al–Cu alloys.28 Furthermore, multiphase Pt–Au–Cu ternary alloy has also been chosen as precursor
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