Annealing-Induced Changes in the Microstructure and Mechanical Response of a Cu Nanofoam Processed by Dealloying

Abstract

Cu nanoporous foams are promising candidates for use as an anode material for advanced lithium ion batteries. In this study, Cu nanofoam was processed from pack-cemented bulk material via dealloying. In the as-processed Cu nanofoam, the average ligament size was ~105 nm. The hardness in this initial state was ~2 MPa, and numerous cracks were observed in the indentation pattern obtained after hardness testing, thus indicating the low mechanical strength of the material. Annealing for 6 h under an Ar atmosphere at 400 °C was shown to result in crystalline coarsening and a reduction in the probability of twin faulting in the ligaments. Simultaneously, the junctions of the ligaments became stronger and hence more difficult to crack. This study demonstrates that moderate heat treatment under Ar can improve the resistance against crack propagation in Cu nanofoam without a large change in the ligament size and the surface oxide content, which can thus influence the electrochemical performance of the material in battery applications.