Composition of Periclase and Calcium-Silicate Phases in Magnesia Refractories Derived from Natural Microcrystalline Magnesite
Mineralogical and microstructural properties of sintered and fused magnesia grains and refractory bricks derived from natural magnesite were examined. Although their CaO/SiO2 ratios can be used to approximate their mineralogical compositions, detailed X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies revealed significant deviations from the expected phase assemblages. Their microstructures vary widely in terms of proportions of direct periclase bonding, amounts and phase constitution of the siliceous bonding, and the size and composition of the periclase crystals. An exceptionally high solid solubility of CaO in periclase crystals was detected. Most of the phases of the siliceous bond exhibit nearly stoichiometric compositions and show intriguing substitutions.
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