Composition of Periclase and Calcium‐Silicate Phases in Magnesia Refractories Derived from Natural Microcrystalline Magnesite

Abstract

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.

Synthesis of cordieritic materials using raw kaolin, bauxite, serpentinite/olivinite and magnesite

“…Olivinite and serpentinite, containing relative low iron content, were taken from the Vourinos area (Kozani district, West Macedonian). Magnesite of high quality, used mainly for the production of magnesia refractories, was taken from the Mantoudi area (Euboea island) [26].…”

Microstructural and densification study of natural Indian magnesite in presence of zirconia additive

“…High temperature flexural strength and corrosion resistance property are markedly improved with the increase in direct bonding of magnesia crystals (Lampropoulou et al 2005).…”

Improvement in thermomechanical properties of off‐grade natural magnesite by addition of Y2O3

“…Various processes have been developed for the beneficiation of low‐grade magnesites like physicochemical process, bioleaching, hydrometallurgy, reverse flotation technique, etc., to reduce the lime and/or silica content in magnesite to improve their refractoriness. Alternatively, thermomechanical properties of sintered magnesite can be improved by modifying the phase assemblage or by altering the geometric distribution of low melting phases . Other effective approach to enrichment in properties of lean‐grade magnesite is to incorporate some kind of additive, which could react with the impurities and convert them into some other high melting phases, thereby reduce the formation of low melting compounds and subsequently improve the refractoriness of the sintered magnesite specimens .…”

“…Alternatively, thermomechanical properties of sintered magnesite can be improved by modifying the phase assemblage or by altering the geometric distribution of low melting phases. [16][17][18] Other effective approach to enrichment in properties of lean-grade magnesite is to incorporate some kind of additive, which could react with the impurities and convert them into some other high melting phases, thereby reduce the formation of low melting compounds and subsequently improve the refractoriness of the sintered magnesite specimens. 19,20 It was reported that presence of titania (anatase phase) increased the hot strength of sintered magnesite samples by forming high melting phases CaTiO 3 and magnesium titanate 19 , and thus reduce the availability of CaO to form Ca-containing low melting compounds.…”