Growth of spiral carbon tubes by a mixed-valent oxide-catalytic carbonization process

The synthesis of carbon tubes is vitally important in carbon research and applications. In this paper, spiral carbon tubes are grown for the first time by a mixed-valent oxide-catalytic carbonization process. The carbon tubes are highly twisted and have many growth-induced nodes. The carbon tubes are nucleated on spherical carbon cores, created by unclosed polyhedron carbon shells containing pentagonal carbon rings. The conical growth of graphitic layers along the tube is the result of a temporary shortage of the supply of pentagons. The pairing of pentagons and heptagons is the key to nucleating the nodes. Our experiments prove that the fraction and nucleation rates of pentagons, hexagons and heptagons determine the surface geometry of the product.