Formation of (BN)(x)C-y and BN nanotubes filled with boron carbide nanowires

Boron carbide-filled (BN)(x)C-y nanotubes with outer layers of pure carbon and inner layers of pure boron nitride (BN) have been synthesized for the f irst time in high yield by using pure carbon nanotubes (CNTs) as templates. The (BN)(x)C-y nanotubes form by capillary filling of boron oxide vapor co ndensed into the inner cavity and a subsequent substitution reaction of the boron oxide with the inner carbon layers of the CNTs in the presence of ni trogen gas. Through a CNT-confined reaction, boron oxide reacts simultaneou sly with gaseous carbon monoxide or the carbon layers in the interior of th e nanotubes to form a boron carbide filling. The diameters of the filled na nowires typically range from 7 to 20 nm, and the thickness of BN and C tubu lar layers is about 5 nm. The length of the filling can be up to the entire length of the nanotubes. Boron carbide-filled pure BN-NTs also form in the product.