Study of ReaxFF molecular dynamics simulation about chemical reactions mechanisms of magnesium-aluminium spinel polishing

Chemical mechanical polishing (CMP) is the predominant method for finishing hard and brittle materials that are challenging to machine. We proposed replacing the soft polishing pads used in traditional CMP with hard ceramic plate to offer rigid support for polishing magnesia-alumina spinel (MgAl2O4) and to achieve better flatness. However, the chemical reaction mechanisms occurring during the process remain unclear. In this study, we employed ReaxFF molecular dynamics (MD) simulations to investigate the chemical reaction mechanisms between MgAl2O4 and the polishing slurries (ethylene glycol, ethylenediamine, hydrogen peroxide, water) during the polishing process. We found that reactions mostly involved -OH chemisorption. Ethylenediamine (C2H8N2) slurries had the lowest bond order of reactant cations (Ct) with -O and the highest ethylene glycol ((CH2OH)2) Ct-O bonds. Al-O bonds were more common than Mg-O bonds in all slurries. C2H8N2 slurry had the lowest bond energies, aiding material removal. Higher slurry concentrations increased reactant bonding and lowered bond energy, with polishing pressure having minimal effect. Our results clarify the atomic-level chemical mechanisms of MgAl2O4 polishing. This provides a valuable approach for designing chemically reactive polishing slurries and offers theoretical support for the efficient removal of MgAl2O4 materials.