3D Nanocomposites of Covalently Interconnected Multiwalled Carbon Nanotubes with SiC with Enhanced Thermal and Electrical Properties

Synthesizing 3D carbon nanotube (CNT) networks with multifunctional characteristics has stimulated the interest from the scientific community since the 1990s. Here, the fabrication of a novel composite material consisting of 3D covalently interconnected multiwalled CNT with silicon carbide (SiC) nano and microparticles is reported. The material is synthesized by a two-step process involving the coating of CNT with silicon oxide (SiO_x) via chemical routes, followed by spark plasma sintering (SPS). SPS enables carbothermal reduction of SiO_x and subsequent densification of the material into 3D composite blocks. Covalent interconnections of CNT are facilitated by a carbon diffusion process resulting in SiC formation as SiO_x coated CNT are subjected to high temperatures. The presence of SiC in the sintered composite has been confirmed by Raman spectroscopy, as well as through energy filtered transmission electron microscopy maps. Interestingly, the 3D CNT composite exhibits high thermal conductivity (16.72 W m^-1 K^-1); and also a semiconducting behavior with an electron hopping mechanism associated to a 3D variable range hopping model. These findings demonstrate that it is indeed possible to fabricate SiC-CNT composites with enhanced physical properties that can be used as multifunctional materials.