The interaction between SiO_2 (vitreous/fused silica and quartz) and Mg powder at 450-640 deg C was investigated employing a combination of X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. The interaction resulted in the formation of a periodic layered structure, consisting of alternating MgO and Mg_2Si-rich layers, with typical thickness of 0.5-3 mu m. The reaction zone was found to grow by a parabolic law with activation energy of about 76 and 90 kJ/mol for fused silica/Mg and quartz/Mg interactions, respectively. The growth process is controlled by Mg diffusion to SiO_2 substrate. A qualitative model describing the formation of such a layered structure in the SiO_2/Mg system is presented.
展开▼
