Mullite-glass and mullite-mullite interfaces: Analysis by molecular dynamics (MD) simulation and high-resolution TEM
The properties of mullite-glass and mullite-mullite interfaces have been investigated at 1800 K by molecular dynamics (MD) simulation and high-resolution TEM. The simulation showed that mullite-glass interfaces typically have much lower interfacial energies than mullite-mullite interfaces, which results from the structural flexibility of the glass and associated accommodation of interfacial mismatch. The (110)-glass interface has the lowest energy of all interfaces studied, which is consistent with the observed dominance of this interface in experimental mullite-glass samples examined by TEM. The simulation shows that the interfacial energies of the (100)-glass and (010)-glass interfaces are higher than that those of the (001)-glass interface, so  and  would be expected to be the dominant growth directions. However, the growth of mullite in glass occurs predominantly in the  direction. This apparent discrepancy can be explained by the fact that growth in the  and  directions is limited by the slow growth of (110) plane (i.e.,  direction), which facilitates  growth, which is confirmed by the TEM data.