Chemical Stability of Carbon Nanotubes in Aluminum Matrix for Casting Process

Abstract

Recently, carbon nanotubes (CNTs) reinforced Al matrix nanocomposites, fabricated by powder metallurgy, show a possibility of high strength structural applications due to their exceptional mechanical properties. However, it is hard to fabricated CNT/Al nanocomposites by casting process, because CNTs are oxidated over 400 degrees C in atmosphere and react with molten Al to form Al carbide phases. In this study, chemical stability of SiO2 coated CNTs in molten Al was analyzed. The SiO2 coated CNTs, with SiO2 layer thickness of 20 nm, were fabricated by sol-gel process to increase chemical stability in molten Al matrix. The SiO2 coated CNTs show a microstructure with homogeneous coating of SiO2 on the surface of CNTs. After heat treatment of SiO2 coated CNT/Al composite at 1000 degrees C, CNTs survived without reaction with Al to form Al carbides. From the microstructure, calorimetric, and XRD analyses, it is considered that SiO2 layer acts as reaction barrier between CNTs and Al