Gas convection and vertical temperature gradient-regulated aligned growth of boron nitride nanotubes for efficient thermal management

Boron nitride nanotubes (BNNTs) offer remarkable potential for thermal management and optoelectronic applications due to their high aspect ratio, excellent thermal conductivity, electrical insulation, and mechanical strength. However, achieving high-quality, well-aligned BNNTs (ABNNTs) remains a critical challenge, largely due to limited understanding of their growth mechanism. Here, we develop a three-dimensional flow–force–thermal coupling model that reveals how gas convection and vertical temperature gradients synergistically drive the aligned growth of ABNNTs. We elucidate the essential roles of thermophoretic and shear forces in guiding nanotube orientation. Based on this insight, a synthesis strategy integrating computational fluid dynamics and thermo-solid coupling analysis is proposed and experimentally validated. The resulting ABNNTs exhibit high crystallinity, low defect density, and near-ideal BN stoichiometry. When applied as thermal interface materials (TIMs) in LED devices, ABNNTs reduce the core temperature by approximately 17.9 °C and enhance thermal dissipation efficiency by ∼20.7 %, outperforming disordered BNNTs and commercial TIMs. This work not only clarifies the fundamental mechanism underlying ABNNT alignment, but also establishes a rational design strategy for advanced thermally conductive materials and their integration into high-performance electronic systems.