Nano-structured carbon obtained by chlorination of NbC

New carbon materials have been synthesized by chlorinating niobium carbide at different temperatures. During the reaction, the volatile niobium chloride, mainly NbCl5, is formed and eliminated leaving the carbon in the shape of spherical particles. TEM examination of the remaining particles revealed that at 400 °C and 700 °C they are composed of a NbC core with an amorphous carbon shell outside. The NbC cores are very small (∼20 nm) at 700 °C and they are not observed at 900 °C. Carbon particles without the NbC core present a more ordered structure composed of concentric wavy graphene layers. This structure seems intermediate between carbon onions and carbon blacks. The 900 °C sample presents a very high BET surface area (1292 m2 g−1) and the lower temperature samples exhibit a hysteresis phenomenon that can be attributed to the existence of large pores in the interspace between the NbC core and the carbon shell.