Boron nitride nanotube
Polymorph of boron nitride / From Wikipedia, the free encyclopedia
Boron nitride nanotubes (BNNTs) are a polymorph of boron nitride. They were predicted in 1994[2] and experimentally discovered in 1995.[3] Structurally they are similar to carbon nanotubes, which are cylinders with sub-micrometer diameters and micrometer lengths, except that carbon atoms are alternately substituted by nitrogen and boron atoms. However, the properties of BN nanotubes are very different: whereas carbon nanotubes can be metallic or semiconducting depending on the rolling direction and radius, a BN nanotube is an electrical insulator with a bandgap of ~5.5 eV, basically independent of tube chirality and morphology.[4] In addition, a layered BN structure is much more thermally and chemically stable than a graphitic carbon structure.[5][6] BNNTs have unique physical and chemical properties, when compared to Carbon Nanotubes (CNTs) providing a very wide range of commercial and scientific applications.[7] Although BNNTs and CNTs share similar tensile strength properties of circa 100 times stronger than steel and 50 times stronger than industrial-grade carbon fibre,[8] BNNTs can withstand high temperatures of up to 900 °C.[9] as opposed to CNTs which remain stable up to temperatures of 400 °C,[10] and are also capable of absorbing radiation.[11] BNNTS are packed with physicochemical features including high hydrophobicity and considerable hydrogen storage capacity and they are being investigated for possible medical and biomedical applications, including gene delivery, drug delivery, neutron capture therapy, and more generally as biomaterials [12] BNNTs are also superior to CNTs in the way they bond to polymers giving rise to many new applications and composite materials.[11]