Morphology and microstructure of spring-like carbon micro-coils/nano-coils prepared by catalytic pyrolysis of acetylene using Fe-containing alloy catalysts

Three-dimensional (3D) spring-like carbon nano-coils were obtained in high purity (nearly 100%) and high yield (20%) by the catalytic pyrolysis of acetylene at 750-790 °C using an Fe-based catalyst; 54Fe-38Cr-4Mn-4Mo or 71Fe-18Cr-8Ni-3Mo (SUS513). The morphologies and microstructure were examined in detail, and the growth mechanism is also discussed. The diameter of carbon fiber, from which the carbon nano-coils was formed, was 50-200 nm, the coil diameter 100-1000 nm, and the coil pitch 10-500 nm. The nano-coils were generally grown by a mono-directional growth mode, and laces with various morphologies were very commonly observed on the surface. It was observed that the spring-like carbon nano-coils are actually composed of two fused nano-coils.