Small-Scale Processing of High-Performance BNNT Fiber for Space and Electronics Applications

A method to process boron nitride nanotube (BNNT) fibers with a high degree of alignment, high modulus, and good tensile strength is presented. This has been achieved by dispersing BNNTs in a polymer solution, spinning the resulting polymer/BNNT dispersion into fibers, and removing the polymer. Significant alignment is imparted to the BNNTs within the fiber during drawing and heat treatment under tension. These BNNT fibers are characterized structurally and elementally to confirm the BNNT structure. This work has resulted in a highly oriented BNNT fiber with a modulus as high as 396 GPa and a tensile strength as high as 500 MPa. These tensile values represent the current state of the art for BNNT fibers, and the alignment of BNNTs in the fiber is the highest ever achieved for nanotubes-based fibers. Significant porosity is observed from the TEM images of the BNNT fibers' cross section, indicating that further processing optimization can be expected to further increase these properties. A knot can be made in some of the resulting BNNT fibers, suggesting that some of these BNNT fibers are suitable for typical textile processing techniques. BNNT fibers, their textile preforms, and BNNT fiber containing composites will be suitable for applications requiring high thermal conductivity without electrical conductivity, high temperature oxidative resistance, and low dielectric constant, particularly in aerospace and electronics areas.