Toward a Molecular Model of SiC Nanoporous Membrane: Application of Reactive Molecular Dynamics Simulation to the Study of the Pyrolysis of Hpcs Polymeric Precursor

Molecular dynamics (MD) simulations were carried out using a reactive force field, ReaxFF, that we have developed for pyrolysis of liquid HPCS polymer, in order to develop a new molecular-scale model of solid amorphous silicon carbide that is used in the fabrication of SiC nanoporous membranes.

The amorphous structure of SiC was generated by carrying out extensive MD simulations in the NVT ensemble at 2000 K, using ReaxFF. During the simulations the hydrogen radicals, which bond together to generate H₂ over the time, were removed from the simulation box. Long NVT-MD simulations at 2000 K were utilized afterward to equilibrate the structure and make the crosslinking of Si and C atoms more likely. Then, MD simulations in the NPT ensemble and at 2000 K were carried out to attain the density of the ceramic. The system was then gradually cooled down back to ambient temperature. It was then annealed between 300 K and 3000 K to rearrange the atoms to their equilibrium state. Eventually, long NPT-MD simulations were carried to arrive at the amorphous structure of SiC, which is essential to the development of a molecular model of SiC nanoporous membranes. To test the validity of the model, in addition to calculating the radial distribution function, we also computed X-ray diffraction pattern and the mechanical properties of the material. The results are compared with the experimental data.