Self-generated reactor strategy enabling combustion synthesis of ultra-long AlN whiskers for superior thermal management

Conventional aluminum nitride (AlN) whisker synthesis faces inherent limitations, including high reaction temperature, prolonged processing time, high cost and restricted whisker length. Herein, we proposed a novel self-generated reactor strategy that enables the efficient combustion synthesis of ultra-long AlN whiskers. This strategy was realized in the Al/NH₄Cl/PTFE system, where an eggshell-like reactor formed in-situ, establishing a thermodynamically stable and confined environment. This unique architecture was crucial for the controlled growth of uniform and high-aspect-ratio whiskers. Under optimized conditions (7% (in mass) NH₄Cl and PTFE/Al molar ratio of 0.015), AlN whiskers with an average diameter of 0.52 μm and a length exceeding 1 mm (aspect ratio >1900) were successfully obtained. Based on thermal reactivity and thermo-kinetic analyses, a possible mechanism for the formation of the self-generated reactor and the subsequent growth of ultra-long AlN whiskers within it was proposed. Furthermore, the synthesized whiskers were incorporated into nanofibrillated cellulose to fabricate composite films, which demonstrated a high in-plane thermal conductivity of 13.16 W·m⁻¹·K⁻¹. This work not only provides a novel and efficient pathway for AlN whiskers synthesis but also highlights their potential for practical thermal management applications.