Thickness of the GB region is more directly controlled by the total number of atoms in the silicate. In all the samples, calcium ions are preferentially segregated into the cages of the interface regions. However, there is also a saturation for that effect. The number of Ca in the cages does not increase above a certain value and many of the Ca ions remain inside the silicate glass. Dependence of the calcium silicate - alumina interface energy on the grain boundary thickness and CaO content.
Circles show locations of the simulated samples.
Atoms as in Fig. While samples are elongated, two distinctive modes of fracture are observed. In the first one, the column oxygen bonds are broken and crack propagates along the alumina surface, similarly to a delamination process. In the other mode, bonds inside the silicate are broken and crack propagates in a chaotic way inside the glass. Both modes can appear even in a set of samples with the same size and CaO content.