Effect of Metal Impurities on the Tensile Strength of Carbon Nanotubes: A Theoretical Study

Metal catalysts used in the synthesis of carbon nanotubes (CNTs) are one of the main impurities in CNT fibers. Using quantum mechanical computations, we show that these metal impurities have a large impact on the mechanical performance of CNTs and CNT fibers. One single Ni atom adsorption on the wall of a single-walled CNT (SWCNT) can decrease the tube's critical strain about 40% by weakening the C–C bond on the wall of a tube. Further systematic calculations and theoretical analysis showed that the reduction of tube strength is nearly independent of the tube's diameter. Thus, the tensile strength of the CNT fiber is expected to be greatly improved by washing away these metal impurities.