Self-assembled BN fiber aerogels with tunable structure, thermal insulation and compressive elasticity via precursor engineering

The preparation of BN fiber aerogels through precursor pyrolysis still faces challenges, especially in fiber diameter control and high crystallinity with little defects. Through self-assembly and natural drying processes, C₃N₆H₆(H₃BO₃)₂ precursor was synthesized in this work. Large-sized BN aerogel with ideal morphology was fabricated via pyrolysis. Regulation of fiber diameter and aerogel structure was achieved through kinetics of crystal nucleation and growth. The mechanism of nucleation and growth, the process of pyrolysis and reconstructed microstructure of BN aerogel have also been studied. The BN aerogel has ultralow density (<52 mg cm⁻³), exceptional thermal insulation properties (∼0.052 W m⁻¹ K⁻¹), superior elasticity and energy dissipation efficiency. These properties enable it as a promising candidate for advanced thermal insulation materials and high-performance composite reinforcements.