Synthesis of boron nitride and carbon nanomaterials through a solid phase reduction process

Boron nitride nanotubes with 100–150 nm in diameter were synthesized by annealing a mixture of iron oxide and boron powders at 1373 K in nitrogen atmosphere. By adding carbon powders to the mixture, boron nitride nanotubes grew into distinctive structures, which are cup-stacked and bamboo-like structure. Carbon nanotubes and nanowires with 100 nm and 200–300 nm in diameter were also synthesized by annealing a mixture of iron oxide and carbon powders at 1273 K in nitrogen atmosphere. A transmission electron microscope observation showed that boron nitride nanotubes with the cup-stacked and bamboo-like structure did not support metallic iron particles, while the ordinary boron nitride nanotubes, carbon nanotubes and nanowires supported metallic iron particles at their edge. Reaction process between iron oxide and boron or carbon was studied by using thermogravimetry/differential thermal analysis. Considering the observed morphology and analysis results, chemical reactions for the production of these boron nitride and carbon nanomaterials (nanotubes and nanowires) were proposed. Validity of the proposed reactions was investigated thermodynamically. Growth mechanism of the nanomaterials was also discussed.