Microscopy and Microanalysis

Microstructure of polycrystalline MgO penetrated by a silicate liquid

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Dense, polycrystalline MgO was infiltrated with monticellite (CaMgSiO 4) liquid to study the penetration of liquid along the grain boundaries of MgO. Grain growth was found to be restricted with increasing amounts of liquid. The inter-granular regions were generally found to be comprised of a two-phase mixture: crystalline monticellite and a glassy phase rich in the impurities present in the starting MgO material. MgO grains act as seeding agents for the crystallization of monticellite. The location and composition of the glassy phase with respect to the MgO grains emphasizes the role of intergranular liquid during the devitrification process in "snowplowing" impurities present in the matrix. Copyright © 1996 by the Microscopy Society of America.