Free-standing silver/carbon nanotube metal matrix composite thin films

Abstract

Advanced metal matrix composite (MMC) thin-film electrodes were fabricated utilizing single-wall carbon nanotubes (SWCNTs) as a reinforcement material. The MMCs were embedded with SWCNT thin films of 10, 20, and 50 nm thicknesses between thermally evaporated 1.5 µm Ag layers. A method has been developed to release the MMCs as free-standing films, and tensile testing was performed to evaluate the mechanical properties. The MMC containing a 20-nm SWCNT layer achieved a ~30 % increase in ultimate tensile strength, and a ~100 % increase in strain-to-failure, resulting in a ~150 % increase in toughness compared to Ag control samples. Scanning electron microscopy (SEM) analysis of the MMC microstructure revealed a decrease in Ag grain size with increased SWCNT loading, which correlated with the mechanical performance to identify the critical range of SWCNT layer thicknesses to achieve reinforcement. SEM also revealed SWCNTs protruding more than 1 μm from the fracture edges, indicating the potential of the MMCs to bridge micro-cracks in electrodes. The collective results show promise for SWCNT MMCs as an advanced electrode material capable of bridging micro-cracks in solar cells and flexible electronics.