| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 107 === In this study, nanoporous copper with ligament sizes ranging from 29 to 174 nm was successfully synthesized by dealloying Cu18Al82, Cu30Al70, Cu33Al67, and Cu37Al63 alloys. The purpose of this study is to investigate the effect of the intermetallic compound on the synthesis of nanoporous structure, and the θ and η phases of copper-aluminum alloy are focused.
Nanoporous copper has the advantages of light in weight, high surface area, good electrical and thermal conductivity, and wonderful electrochemical stability. It can be applied in sensing, catalyst, lithium battery, surface-enhanced Raman scattering, and carbon dioxide reduction, which is being more and more important nowadays.
Firstly, four kinds of compositional copper-aluminum precursor alloys were fabricated by vacuum arc melting: Cu18Al82, Cu30Al70, Cu33Al67, and Cu37Al63. Each of the four alloys contains different ratios of solid solution phase (α phase) and intermetallic compound (θ phase and η phase), thus creating a different microstructure.
Then, the precursor is dealloyed using different kinds of electrolytes and under different temperatures. Aluminum, which is the more electrochemically active element of the two in the precursor alloy, is selectively removed to form nanoporous copper structures (Nanoporous Cu). The effect of concentrations of electrolyte on the resultant nanoporous structure was also evaluated by the use of Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDS).
The result shows that when two different kinds of θ phase exist at the same time, there is no significant difference between the two. Besides, the η phase can be completely dealloyed in acid but not in alkali. For the carbon dioxide reduction reaction, the current results show that the smaller the ligament of the nanoporous copper, the better the effect of the CO2 reduction, and the micro-nano multi-layer structure produced by the eutectic phase contributes to the improvement of the reduction effect.
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