Large-scale silicon carbide nanowires covered with a silicon oxide sheath (SiC/SiO₂) have been synthesized by microwave sintering technique. The SiC core typically has diameters of 10-90 nm and is covered by a uniform layer of 5-20 nm thin amorphous SiO₂. A combination reaction driven growth process is proposed for the formation of this one-dimensional (1D) structure based on detailed structural characterizations. The 1D nanostructures may find applications as building blocks in nanoelectronic or nanomechanical devices. The combination reaction driven growth process suggests that similar 1D nanostructures of a wide range of materials may be synthesized by microwave sintering technique.