Synthesis and characterization of polyvinylsilazane as a precursor for Si₃N₄ based ceramic materials

This investigation focused on the synthesis and characterization of a polyvinylsilazane (PVSZ) polymer. This material shows promise as a precursor for silicon nitride/silicon carbide based ceramic materials. The polymer was synthesized via the ammonolysis of vinyltrichlorosilane (VTS) in tetrahydrofuran (THF). The polymer was characterized using Fourier Transform Infrared (FT-IR) spectroscopy, ¹H/¹³C nuclear magnetic resonance (NMR) spectroscopy, and gel permeation chromatography (GPC). This polymer was found to have a molecular weight of around 880 g/mol, as determined by GPC. Thermal cross-linking, up to 1500 °C in an inert atmosphere, produced a ceramic material with a char yield of around 85%. The gas by-products from the partial decomposition of the polymer to a ceramic material were characterized using residual gas analysis (RGA). The crystallite phases of the ceramic char, pyrolyzed in different atmospheres, were determined by X-ray powder diffraction (XRD). Lastly, the ability of the polymer to form a free standing monolithic structure as well as the ability to be drawn into fibers was evaluated.