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 arc-discharging 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-range-hopping (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.