Synthesis and Physical Properties of Boron Nitride Nanotubes

Uniform shape of boron nitride nanotubes (BNNTs) were successfully synthesized by pulverization of boron powder mixed with Fe catalysts in a stainless steel vessel followed by annealing the powder at 1200 °C for 12 hours with flowing N₂ and NH₃ in a furnace. During the pulverization process, the Fe particles, used as catalysts, were coated on amorphous boron powders. The shape and type of the BNNTs were critically changed by synthesis conditions such as pulverization and annealing time suggesting that ball milling period is an important factor to produce high quality of homogeneous BNNTs. Results of transmission electron microscope measured from the BNNTs produced with 6 hours of ball milling followed by 12 hours of annealing show that the samples have multi-walled tubular shape with a diameter of 30–50 nm. A specific surface area calculated by measuring N₂ adsorption isotherm was 17.65 m²/g. Magnetization values measured by using a superconducting quantum interference device revealed that BNNTs have a typical pattern of paramagnetic property at 2 and 300 K.