Boron containing polymers as precursors to ceramic materials

A set of six reaction schemes was investigated for the formation of telomeric precursors that could be processed through a liquid crystalline state and subsequently pyrolyzed into a ceramic material, namely Boron Nitride, (BN). Of these six schemes, the reactions of Boric Acid with Melamine (BAM), Biuret (BAB) and Urea (BAU), gave products of the most merit. Upon synthesis, the chemical structures of the reaction products were established by Fourier Transform Infrared (FTIR) and ¹¹B, ¹³C, and ¹HNuclear Magnetic Resonance (NMR) spectroscopy. Differential Scanning Calorimetry (DSC), Polarized Light Microscopy (PLM), and Radiometry were used to study the thermal behavior and to provide insight into the possible formation of a liquid crystalline state. Of the three materials studied, BAB was the only compound which exhibited liquid crystalline behavior in the melt. An effort at producing continuous filaments by melt extrusion was attempted. However, continuous filaments were not produced. The pyrolytic behavior of the materials was established via Thermogravimetric Analysis (TGA), which provided knowledge of the pyrolytic products and elimination species. Upon the completion of the thermal studies, the materials were subjected to large scale pyrolysis in a tubular furnace. The pyrolytic products were characterized by Wide Angle X- Ray Scattering (WAXS), which established the identity of the products as a mixture of turbostratic BN and B₈C. Finally, graphite composites were fabricated by the coating of graphite fibers with molten BAB and BAU. Upon subjection to pyrolysis followed by characterization by WAXS and Scanning Electron Microscopy (SEM), a coating consisting of a mixture of turbostratic BN and B₈C was found adhering to the graphite fibers. These results offer evidence toward the ability of achieving new advanced composite materials by the utilization of boron containing telomers.