Synthesis and high-temperature evolution of polysilylcarbodiimide-derived SiCN ceramic coatings

Herein we report on the preparation and high-temperature evolution of polysilylcarbodiimides-derived SiCN ceramic coatings. Two polysilylcarbodiimide-based preceramic polymers with different molecular structures (i.e., a rather linear and a highly-branched polymer) were synthesized and their use for the preparation of sub-μm-thick SiCN ceramic coatings was assessed. The different molecular architecture of the polysilylcarbodiimide has been shown to significantly affect the composition (e.g., the content of segregated carbon) and properties of the resulting ceramic coatings. Thus, the high-temperature crystallization behavior and the ordering of the segregated carbon phase depend on the carbon content and consequently on the preceramic polymer structure. Moreover, the content of the segregated carbon phase present within the microstructure of the prepared SiCN coatings determines their hardness and elastic properties. The low-carbon-content coating has been shown to be stiffer and have higher hardness than the carbon-rich SiCN sample.