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

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.