Nearly stoichiometric BN fiber by curing and thermolysis of a novel poly[(alkylamino)borazine]

Boron nitride (BN) fiber with a composition of BN1.09 was fabricated by curing and thermolysis of a novel poly[(alkylamino)borazine]. The processes have been studied by a combination of gel-content test, TGA, elemental analysis, IR, XPS, XRD, SEM and TEM. The results show that curing made polymer fiber infusible and resulted in a significant improvement of ceramic yield from 53.2 wt% to 73.8 wt% at 1000 °C. Moreover, pyrolysis in NH3 at 1200 °C generated a nearly stoichiometric BN without carbonaceous impurities while in Ar led to a BNC material with carbon content of 6.13 wt%. The obtained amorphous BN fiber with a diameter of 13 μm displayed a tensile strength of approximately 600 MPa. Furthermore, the BN fiber illustrated good oxidation resistance in air.