The Fabrication Of The Nanoporous Copper By Dealloying

In recent years, nanoporous metals （NPMs） have been extensively studied in the field ofnanotechnology and porous materials. Preparation of NPMs are mainly two ways: the templatemethod and the dealloying method. The template method is commonly used to fabricate NPMsthrough the replication of porous alumina or liquid–crystal templates. The dealloying method,also known as selective corrosion, is a corrosion process during which one or more activecomponents （also called poor components） are removed from an alloy, and the activecomponents （also called noble components） can be either an element in single-phase solidsolution alloys or a phase in multiphase alloys. Compared with the template, dealloying issimple, and can dynamic control of the pore size and arrangement, therefor, this paper givepriority to the use of dealloying method. At last, the chief research contents of this paperconcentrate on the fabrication of nanoporous copper （NPC） and it’s electrochemical activity,which is summarized as follows:（1） By controlling the corrosion time, porous copper and porous alloys were successfullysynthesized by free dealloying of Mn₇₀Cu₃₀alloy ribbons. Combining the microstructures ofas-dealloyed samples and the surface diffusion dynamics model, which was put forward byErlebacher et. al, the formation and evolution process of porous structure were put forward indealloying. And the corrosion time dependence of fractal dimension （Df） was obtained throughthe characterization of the porous structure using the fractal theory. According to the trend ofDf, the dealloying process of Mn₇₀Cu₃₀was divided into three stages.（2） NPC ribbons with nano-scale pore size were synthesized by a free corrosion method ofAl-Cu alloy ribbons prepared by rapid solidification. Moreover, the microstructures of NPCwere bimodal channel size distributions. The effects of alloy composition, etching solutionand annealing process on the dealloying process and morphology of nanoporous coppercatalysts have been investigated, moreover, these effects were further explained from theviewpionts of phase composition and copper’ surface diffusion. For as-dealloyed Al65Cu35alloy ribbons with AlCu phase, there are some island-like structure in elliptical shape amongthe porous structure. And the reason is Al in the AlCu phase can hardly be eroded. ForAl85Cu15alloy ribbons, the optimal annealing temperature is200℃. When annealed at a lower temperature, the components can not be homogeneous, which makes the porous structure wasnot uniform, while a higher temperature, the pore size was larged.（3） When the Al-Cu amorphous films fabricated by the magnetron sputtering method wasdeallyed, Al atoms were selective eroded, leaving the rest of the Cu atoms form Cu’groupthrough surface diffusion. The nanoporous structure was formed between Cu’group, but wasnot similar as the skeleton porous structure.（4） The electro-catalytic activity of NPC was tested on nitrite using the method of cyclicvoltammetry. At ambient temperature, the current-voltage graph （CV） was measured in boricacid buffer solution with the PH is2.5. The CV curve showed that, in the acidic conditions, acouple redox peak of appeared, and oxidation/reduction peak appeared in-0.9/0.9V, in whichthe peak current density obviously increased, suggesting that a big electronic transfer rate wasgenerated on nanoporous copper, so NPC have a very good oxidative activity to NO₂-. Thisfinding helps to expand the application of NPC in the field of electro catalytic, and promote thedevelopment of superior catalytic properties of nanoporous metal.