Reactive Dynamics Simulation Study on the Pyrolysis of Polymer Precursors to Generate Amorphous Silicon Oxycarbide Structures

Amorphous silicon oxycarbide (SiOC) ceramics have extensive applications as structural and functional materials because of their unique properties. Preparation of SiOC from the pyrolysis of polymer precursors involves a complicated process of chemical reactions, various bond redistributions, and so on. With the aim to gain more insights into this and obtain a SiOC structure model, a series of molecular dynamics (MD) simulations integrated with a shell programming of gas removal scheme were implemented. Here, we chose hydridopolycarbosilane and polymethylhydrosiloxane as polymer precursors and constructed a rational polymer atomic model by using a reactive force field ReaxFF derived from elsewhere, which has been tested and verified to be applicable to our C/Si/H/O system. MD simulations of pyrolysis of the polymers indicated that H₂ and CH₄ were the major gas products, which were deleted through NVT-MD simulations along with the script code mimicking the experimental process. The atomic model of the dense SiOC was obtained after compression and further equilibration of the solid structure. The final SiOC structure was analyzed by computing its radial distribution function. It contains C-C, Si-O, Si-C, and Si-Si bonds, which agrees well with the experimental data. These results confirm the accuracy of the MD simulations and the atomic model of SiOC ceramics.