Molecular dynamics investigation of structure and high-temperature mechanical properties of SiBCO ceramics

Highlights: • The nano-domain structure of SiBCO is reproduced by large-scale atomistic simulations. • Calculated pair and angular distribution functions consist with experiments and DFT calculation. • Silicon atoms form mixed bonds tetrahedron with carbon and oxygen at domains interfaces. • Change in slope of temperature-dependent Young's moduli indicates glass transition temperature. - Abstract: SiCO ceramics present excellent properties at high temperatures, the addition of boron for SiCO leads to enhanced performance on thermal stability and creep temperature. Investigating atomic structure and its influence on material property are essential for further study. In this study, large-scale molecular dynamics simulations were used to study amorphous SiBCO structures with different carbon contents. Phase separation and free carbon structures were successfully reproduced by melt-quench simulation. The calculated pair distribution functions of SiBCO are comparable to those of SiCO in experiments, the C–C–C angular distribution indicates strong sp² carbon character together with a sp³ character. Si-centered tetrahedrons present in amorphous SiBCO and the most popular case is Si–C/O tetrahedron. Si₃BC₇O₃ presents the largest Young's modulus for all the temperatures due to the network structure of free carbon. A change in the slope of temperature-dependent Young's moduli at 1300 K–1700 K for Si₃BC₃O₃ indicates the glass transition temperature