Formation and structure of boron nitride conical nanotubes

Nanotubes exhibiting a novel structure - boron nitride (BN) conical nanotubes whose walls consist of conical layers with their cone axis parallel to the tube axis, as opposed to ordinary nanotubes, composed of concentric cylindrical layers with their normal perpendicular to the tube axis - were synthesized simultaneously with BN nanotubes by using carbon nanotubes (CNTs) as templates. The diameters of the BN conical nanotubes are typically about 15 nm, which is similar to those of the starting CNTs. Apex angles and inner diameters of most BN conical nanotubes are about 40° and 1 nm, respectively. The lengths of the BN conical nanotubes range from 50 nm to up to several micrometers.