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 a mixture of a preceramic polymer (polyvinylsilazane) and tetrabutyl orthotitanate precursors by crosslinking at 300 oC and pyrolysis in the temperature range of 900 oC - 1400 oC in flowing nitrogen atmosphere. Crosslinked precursor was studied through DSC-TG 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. Ti-doped SiCN ceramic systems appeared as single-phase SiTiCNO amorphous ceramics up to 1100 oC. The phase separation of SiTiCNO ceramics started at 1200 oC and exhibited TiO2 nanocrystals in the 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 samples as compared to the undoped SiCN of equivalent thermal history. At 1400 oC, 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 matrix. A uniform distribution of these nanocrystals in the SiCN matrix at 1400 oC were observed through TEM/HRTEM analysis. 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.