MWBNNTs

MWBNNTs, or multi-walled boron nitride nanotubes, are cylindrical nanostructures composed of several concentric walls made from hexagonal boron nitride. They are the boron nitride counterparts to multi-walled carbon nanotubes, sharing a tubular morphology but exhibiting distinct electronic and chemical properties. MWBNNTs typically have outer diameters ranging from tens to hundreds of nanometers, with multiple concentric BN sheets and lengths that can extend to micrometers.

In terms of properties, MWBNNTs are electrically insulating due to a wide bandgap of about 5 eV, which makes them attractive for dielectric and insulating applications. They exhibit high mechanical stiffness and strength, along with good thermal stability and thermal conductivity along the tube axis. The material is chemically inert and resistant to oxidation at moderate temperatures, contributing to durability in harsh environments. The combination of strength, light weight, and insulation differentiates MWBNNTs from many other nanomaterials.

Synthesis methods include chemical vapor deposition, arc-discharge, and laser ablation, using boron-containing precursors and nitrogen sources such as ammonia or nitrogen gas. Production often yields mixtures of single- and multi-walled BNNTs and requires purification to remove catalyst residues; achieving precise control over wall number and dimensions remains an area of development.

Applications focus on reinforcing polymers or ceramics to improve mechanical performance while preserving electrical insulation, and on thermal management or dielectric components in electronics. The high neutron capture cross-section of boron also motivates interest in BNNT-containing composites for radiation shielding. Challenges include scalable production, cost, purity, and dispersion within matrices, as well as reliable property control for device integration.

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