Preparation and properties of hollow BN fibers derived from polymeric precursors

Boron nitride (BN) complex precursors were synthesized from a mixture of 2,4,6-tri(methylamino)borazine ([CH3(H)N]3B3N3H3) and tris(methylamino)borane ([B(NHCH3)3]). The reactions between the two mixtures aimed at producing polymeric green fibers via a melt-spinning process and producing novel hollow BN ceramic fibers with various shell thicknesses by curing and pyrolysis. The properties and pyrolytic process of the complex precursors were characterized by TG-DSC-FTIR-MS online coupling analysis. The microstructure, solid phase, and morphologies of hollow BN fibers were investigated using XRD, SEM, TEM, and elementary analysis. Results showed that the synthesized fibers were highly pure and uniform with a mean diameter of 9 μm. The dielectric properties of the BN fibers were excellent with a dielectric constant of 2.90 and a dielectric loss factor of 0.00064. These results confirm that the ceramic fibers synthesized using the novel complex polymeric precursors indicate their adequate properties as micro-wave transparence reinforcements.