Large‐scale synthesis and growth mechanism of boron nitride nanocomposite assembled by nanosheets and nanotubes

Boron nitride nanocomposites assembled by nanosheets and nanotubes can exert multi‐dimensional synergistic toughening and strengthening effects. This material is expected to be a high‐efficiency reinforcement additive in advanced structural ceramics. In this study, we designed a universal method for synthesizing gram‐scale boron nitride nanocomposites by annealing the precursor containing catalyst in chemical vapor deposition equipment under flowing ammonia, and a combined growth mechanism of surface‐diffusion and solid‐liquid‐solid is proposed. The boron nitride nanosheets were initially formed by a surface‐diffusion reaction between boron trioxide and ammonia at 1300°C. At elevated temperatures (1400°C‐1500°C), the boron nitride nanotubes grew in‐situ from the nanosheets in the presence of catalysts through a solid‐liquid‐solid mechanism, forming the desired boron nitride nanocomposite.