Disordering and the electronic transport behaviors of NbC–Al4C3–C composite

A composite nanomaterial composed of NbC nanocrystals, Al4C3 nanorods and carbon nanofibers as well as amorphous carbon was fabricated by arcdischarging a Nb3Al block as an anode in CH4 gas. The growth process of the NbC–Al4C3–C composite was deduced according to the microstructures of its components and the experimental conditions. NbC nanocrystals with non-stoichiometric chemical composition were in a cubic shape. As the decomposition product of the precursor of CH4 gas, carbon nanofibers were thought to be as templates, reacting with Al atoms, to form Al4C3 nanorods with a diameter of 15–40 nm. A thin layer of aluminum carbide oxide covered the surface of Al4C3 nanorods. The temperature dependence of the resistivity for the NbC– Al4C3–C composite was described by the variable-rangehopping (VRH) model between about 100 K and 300 K because of the strong localization of electrons by disorder in the carbon matrix. Below 100 K, the transport behaviors of the pellet deviated from the VRH model due to the conduction competition between the semi-conducting carbon matrix and metallic NbC nanocrystals