BNNTs

BNNTs, or boron nitride nanotubes, are cylindrical nanostructures formed from a hexagonal lattice of alternating boron and nitrogen atoms. They are structurally analogous to carbon nanotubes but consist of hexagonal boron nitride sheets rolled into tubes, with single-walled (SWBNNTs) and multiwalled (MWBNNTs) forms reported. BNNTs share the high aspect ratio of CNTs but exhibit a wide electronic bandgap of about 5 eV, rendering them electrically insulating. They are valued for thermal stability, chemical inertness, and mechanical strength, making them candidates for high-temperature and harsh-environment applications. The insulating electronic character coupled with good mechanical properties distinguishes BNNTs from many other nanotube systems.

Key properties include high thermal stability with oxidation resistance at elevated temperatures and a high Young's modulus in the gigapascal range, along with notable tensile strength. The thermal conductivity is substantial but varies with quality and structure. BNNTs are chemically inert and resistant to many acids and bases, contributing to durability as fillers in composites and coatings. Their wide bandgap also makes them attractive as dielectric components in nanoscale devices.

BNNTs are synthesized primarily by catalytic chemical vapor deposition, using BN-containing precursors such as borazine or ammonia borane and transition‑metal catalysts on substrates at temperatures around 800–1200 C. Other routes include arc discharge, laser ablation, and ball milling followed by annealing. Controlling diameter, chirality, and yield remains challenging, as does scalable production and dispersion in matrices. In applications, BNNTs are studied as reinforcement in polymers and ceramics, as thermal management fillers in electronics, and in research on hydrogen storage and biocompatible materials. Widespread use is limited by production cost, process variability, and handling considerations.