Liquid Crystals and Macroscopically Aligned Fibers from Boron-Nitride Nanotubes

Abstract

Boron Nitride Nanotubes (BNNTs) are cylindrical structures with a morphology similar to a rolled hexagonal boron nitride sheet, reminiscent of carbon nanotubes (CNTs). BNNTs have some properties in common with CNTs, such as high strength and heat conduction, but also some different ones, such as electric insulation and thermal stability. These properties are mainly seen at the nanoscale level, but they can also be used at a larger scale by controlling how the BNNTs are aligned in the material. To uncover the incredible properties of BNNTs we have studied their dispersion, functionalization, alignment, and materials made from these building blocks. We found that BNNTs can be dispersed in chlorosulfonic acid, forming liquid crystals at high concentrations. The order in the liquid crystals can be imparted to the materials (e.g. fibers) by extrusion and coagulation. This allowed the formation of aligned fibers with neat BNNTs. These materials can be of great importance for applications in extreme environments where, thermal stability, heat conductivity, and high tensile strength are of importance.