Carbon nanoshells obtained from leaching carbonyl nickel metal powders

Certain carbonyl nickel powders manufactured by the Mond chemical vapour deposition process are coated with a nanometric layer of defected graphitic carbon. Through a simple chemical process of acid leaching of the nickel metal a dry filtrate is obtained, which consists of carbon nanopowder. As imaged in a transmission electron microscope, the powder consists of nanostructured hollow carbon shells, termed carbon nanoshells, that are positive replicas of the nickel particulates. The carbon shells can have thicknesses that range from a few nanometers to tens of nanometers. They are composed of layered nanocrystals of turbostratic graphite, the average thickness of which is 9 ± 0.5 nm, as determined by X-ray diffraction. In all cases, the basal planes follow the curvature of the original Ni metal core. Measurements using electron energy-loss spectroscopy show that the energy of the bulk low-loss plasmon in the nanoshells is significantly higher than that of amorphous carbon, lying just below that for annealed graphite. This shows that the electronic character of the carbon nanoshells is closer to that of graphite than to amorphous carbon. Carbon nanoshells of this type can be produced cheaply and in large quantities by recycling the Ni.