Flame synthesis of hybrid nanowires with carbon shells and tungsten-oxide cores Original Research Article

We report the flame synthesis of hybrid nanowires composed of tungsten-oxide cores covered with uniform carbon shells. The synthesis is performed using 1-mm diameter tungsten probes inserted in an opposed-flow methane oxy-flame. The unique thermal and chemical composition of the generated flame tends to convert pure (99.9%) bulk tungsten into 1-D structures of unique morphology. The physical characteristics of the nanowires grown on the 1-mm diameter tungsten probe include lengths of up to 50 μm and diameters ranging from 20 to 50 nm. A two step hybrid nanowire synthesis mechanism is proposed. The initial step forms tungsten-oxide nanorods in the oxygen-rich flame region. The second step involves rapid formation of carbon shells from hydrocarbons transferred from the carbon-rich zone of the flame during the probe removal.