Molecular dynamics investigation of Si–B–N ceramics: effects of boron content

Silicon boron nitride (SiBN) has the advantages of Si3N4 at high temperatures and also advantageous anti-oxidation and mechanical properties. While the synthesis methods of this new material are limited to the sol–gel route, understanding the structural and mechanical properties of SiBN becomes essential in order to control the properties under fabrication. In this study, atomistic models of SiBN ceramics with different boron content were built by melt-quench technologies. Pair distribution function and angular distribution function were applied to study the structural properties, and tensile loading was applied in order to obtain the stress–strain curves and mechanical properties of SiBN. Phase separation of SiN-rich region and BN-rich region was observed for SiBN with different B content. With B content increasing, the BN-rich region tended to be larger and the SiN-rich region became smaller. Si3B3N7 showed sharper and narrower peaks on distribution functions and larger Young's modulus than Si3BN5 and Si3B5N9.