A Novel TiO2–TiC–TiC0.3N0.7–C–SiCN Multiphase Ceramic Nanocomposite from Preceramic Polymer Pyrolysis

Abstract

The current investigation describes the synthesis of SiTiCNO ceramics derived from the mixture of a preceramic polymer (polyvinylsilazane) and tetrabutyl orthotitanate precursors by crosslinking at 300 °C and pyrolysis in the temperature range of 900–1400 °C in flowing nitrogen atmosphere. Crosslinked precursor was studied by thermogravimetry to estimate ceramization temperature as well as ceramic yield. Further, the evolution of phase and nanostructure with temperature in the composite SiTiCNO ceramics was analyzed by the help of different characterization techniques, such as XRD, Raman, and electron microscopy. The Ti-doped SiCN ceramic system appeared as single-phase SiTiCNO amorphous up to 1100 °C. The phase separation of SiTiCNO ceramics started at 1200 °C and exhibited TiO2 nanocrystals distributed in the amorphous SiCN matrix. Ti-doping was found to accelerate the separation of the free carbon phase from the SiCN matrix, and the said carbon had better graphitic order in the Ti-doped SiCN samples as compared to the undoped SiCN of equivalent thermal history. At 1400 °C, high temperature stable phases such as TiC and TiC0.3N0.7 were formed along with predominant rutile-TiO2 phase within the Si–Ti–O–C–N composite. A uniform distribution of these nanocrystals in the SiCN matrix at 1400 °C was observed by high resolution transmission electron microscopy. The current work exhibits the formation of a unique multiphase composite with the co-existence of nanocrystalline phases uniformly distributed within a polymer derived ceramic matrix.