The mechanism of periodic layer formation during solid-state reaction between Mg and SiO2

The as yet unresolved microstructure of the periodic layers formed in the reactive diffusion system Mg/SiO2 was clarified by using high-resolution field-emission SEM. The periodic layered structure actually consists of the single-phase layer of Mg2Si and the two-phase layer of (Mg2Si + MgO) alternated within the reaction zone. According to the experimental observations and in line with the diffusion-induced stresses model, the mechanism controlling this phenomenon could be attributed to the stresses induced by the difference in interface growth rates of Mg2Si and MgO phases within the layer. When the elastic deformation of the slow-growing aggregated-MgO phase reaches its elastic maximum, it will be split off from the reaction front by the neighboring Mg2Si phase and a new periodic layer forms. The computer simulation results are coinciding well with the experimental data.