Synthesis of precursor for BN fibers

The process for synthesizing the precursor of boron nitride (BN) fibers was studied. The precursor was prepared by a wet chemical approach using melamine (C₃N₆H₆) and boric acid (H₃BO₃) as starting materials. A better precursor was synthesized by using the molar ratio of 1:1 for the melamine and boric acid and the solution concentration of 0.5321 mol/L for the reactants. The synthesized product was analyzed by means of TG-DSC, IR, XRD, SEM, etc. The results show that the precursor consists of elements of B, C, N, O, H, which mainly form the structural units of C₃N₃, B-O, C=N, N-H, C-H, B-N, -OH. The synthesized precursor is long-pillared fibers with the cross section dimension of 2-20 μm and the length/diameter ratio of 20-100. BN fibers prepared by nitridation at 1700°C for 3 h have diameter of 2-10 μm and length/diameter ratio of 30-40.