Large-scale molecular dynamics modeling of boron-doped amorphous SiCO ceramics.

At high temperature, silicon oxycarbide (SiCO) exhibits excellent mechanical properties and thermal stability. The incorporation of boron in SiCO results in improved performance in creep temperatures. In this work, large-scale molecular dynamics calculations were applied to obtain amorphous SiCO structures containing boron. Phase separation of C-C, B-C and Si-O was achieved for three compositions, and silicon-centered mixed-bond tetrahedrons were reproduced successfully. As the boron content increases, the boron atoms tend to form B-C and B-Si bonds in the voids, which stretches the free carbon network in some instances, causing a increase in C-C distance. Young's modulus remains stable at high temperature for the high-carbon case, which indicates that the free carbon network plays a critical role in the structural and thermal stability of SiBCO. Graphical Abstract Three major typical structures in the cooling down process for silicon boron oxycarbide (Si5BC2O8). Bonds: red Si-O, blue Si-C, black C-C, green B-C, purple Si-B.