Hybrid BN/BNNT fibers from solution spinning of polyborazine

Ceramics such as boron nitride (BN) are attractive materials considering their high oxidation resistance and good thermal conductivity, particularly for BN. However, BN’s mechanical properties can be limited on the bulk scale, so some attention has been focused on improving the strength and modulus of this material through fiber-based approaches. This work describes the production, for the first time, of a hybrid BN/BNNT fiber. Using a solution-based approach poly [B-(methylamino) borazine] and boron nitride nanotubes (BNNTs) are combined, along with a sacrificial polymer (polyacrylonitrile), and spun into fibers using a dry-jet wet spinning system. These fibers are converted to the hybrid BN fiber by treatment in an ammonia environment up to 1100 °C. These BN/BNNT fibers are characterized structurally and elementally to confirm the BN structure. The maximum strength obtained is 340 MPa and maximum modulus is 146 GPa. This adaptable solution-based approach to creating hybrid BN/BNNT fibers is versatile and can be further optimized to create high strength BN fibers.