Tailoring carbon phase for the enhanced mechanical performance of polymer-derived SiOC ceramics

Polymer-derived SiOC ceramics have demonstrated significant potential across various applications, including structure materials, energy, extreme thermal environments, and semiconductors. It is well-established that the carbon phase in SiOC plays a crucial role in determining the material's properties. However, the relationship between carbon phases and the mechanical properties of SiOC ceramics remains inadequately explored. In this study, a series of SiOC nanosphere powders with varying carbon content were successfully fabricated, and bulk samples were obtained using the spark plasma sintering (SPS) technique. The results demonstrate that both carbon content and sintering temperature play a synergistic role in determining the phase composition—such as the formation of SiC through carbothermal reduction—and the microstructural features, including densification and the distribution of free carbon in SiOC ceramics. These structural modifications significantly enhance the mechanical properties through multiple mechanisms. Among all the samples, the SiOC-C ceramics fabricated at 1600°C possess optimized mechanical properties, with a flexural strength of 38.48 MPa. These findings elucidate the potential mechanism for improving the mechanical properties of SiOC ceramics by introducing the carbon phase, which holds significant implications for the development of high-performance ceramic materials.