High-purity and high-yield boron nitride nanotubes with large aspect ratio were prepared by a facile two-step process, including the synthesis of boron/nickel containing precursors by precipitation reactions and subsequent thermally catalytic chemical vapor deposition reactions. The influence of catalyst content and annealing temperature on the phase composition and microstructure of the products were investigated. The results show that it is difficult to exert the catalytic effect of nickel-based catalyst at low temperatures (<1 400 °C). At appropriate temperatures (1 400–1 500 °C), highly crystalline boron nitride nanotubes with a length of more than 50 μm and a diameter of 50 nm are formed. The content of catalyst in the precursor mainly affects the morphology of the boron nitride product. If the content is too low, it is easy to form boron nitride particles; while high catalyst content can easily lead to catalyst aggregation and form a submicron one-dimensional boron nitride with unregular structure. Based on microstructural evolutions, phase changes, and thermodynamic analysis, the vapor-liquid-solid (V-L-S) growth mechanism of the tip growth mode dominates the formation of boron nitride nanotubes has also been verified.

通过简单的两步工艺制备了高纯度和高产率的大纵横比氮化硼纳米管，包括通过沉淀反应和随后的热催化化学气相沉积反应合成含硼/镍的前体。研究了催化剂含量和退火温度对产物相组成和微观结构的影响。结果表明，镍基催化剂在低温（<1 400 ℃）下难以发挥催化作用。在适当的温度（1 400~1 500 ℃）下，形成长度超过50 μm、直径50 nm的高结晶氮化硼纳米管。前驱体中催化剂的含量主要影响氮化硼产物的形貌。如果含量太低，容易形成氮化硼颗粒；而高催化剂含量容易导致催化剂聚集，形成结构不规则的亚微米一维氮化硼。基于微观结构演化、相变和热力学分析，也验证了尖端生长模式主导氮化硼纳米管形成的气-液-固（VLS）生长机制。