Study on the thermal treatment conditions for fabricating open-cell structure Cu–Sn alloy foams

Abstract

Cu–Sn alloy foams, with an open-cell structure, were fabricated by Cu/Sn coelectrodeposition onto a polyurethane (PU) template in an alkaline electrolyte with a citrate complexing agent before undergoing a subsequent thermal treatment for PU removal in a N2 gas environment. These foams were predominantly comprised of a Cu matrix along with Cu6Sn5 and Cu3Sn intermetallic compounds, which are known as active materials in Cu–Sn alloy electrodes used in rechargeable batteries. The chemical phase change of Cu–Sn alloy foams and its influence on the electrical resistance were studied according to the heating temperature and N2 gas flow rate. Assuming the thermal degradation of PU as a first-order reaction, the dependence of the PU removal process on the heating temperature was also theoretically investigated. In addition, a postannealing process of the Cu–Sn alloy foams was employed to reduce their electrical resistance by promoting grain growth.