Tailoring the carbon nanostructures grown on the surface of Ni-Al bimetallic nanoparticles in the gas phase

► Gas-phase growth of straight, coiled, and sea urchin carbon nanostructures is made. ► The size of Ni-Al nanoparticles and temperature determine the carbon nanostructures. ► Straight carbon nanotubes are grown on Ni-Al nanoparticles <100 nm at 650-800 °C. ► Coiled carbon nanotubes are grown on Ni-Al nanoparticles <100 nm at 500-650 °C. ► Sea urchin carbon nanotubes are grown on Ni-Al nanoparticles >100 nm at 500-800 °C.