Abstract
Nepheline syenite is used instead of feldspars as fluxing in ceramics. In this study, three ceramic bodies were prepared. Nepheline syenite was substituted by Na feldspar in the ratio of maximum 30 wt.%. The pyroplastic deformation was evaluated together with technological properties, including linear shrinkage, water absorption and strength. Phase and microstructural characteristics were also investigated. Results showed that the addition of nepheline syenite provided a decrease in viscosity. The decrease in viscosity caused an increase in the tendency for pyroplastic deformation in bodies containing nepheline syenite; however, this result shows that bodies containing nepheline syenite can be sintered at a lower temperature than the standard body. The addition of nepheline syenite also decreased water absorption and increased strength.
Highlights
Sanitaryware produced using quartz, clay and sodium feldspar are fired at a temperature between 1200 oC and 1300 oC [1]
The present study investigates the effect of the addition of nepheline syenite on the pyroclastic deformation of sanitaryware porcelain
Samples were characterized by water absorption, shrinkage, XRD, flexural strength and microstructure
Summary
Sanitaryware produced using quartz, clay and sodium feldspar are fired at a temperature between 1200 oC and 1300 oC [1]. Nepheline syenite is a light-colored, silica-deficient, and feldspathic It contains nepheline, sodium feldspar (albite), and alkali feldspar (orthoclase, microcline); it does not contain quartz. The. higher alkali oxides content ( ≥14%) and the melting temperature is generally lower than the melting point of sodium and potassium feldspars containing quartz that shifts the melting point to a higher temperature are the advantages of the using of nepheline syenite in the production of ceramic bodies [7]. The increase in densification rate and amount of mullite crystals are important in terms of technological properties of the ceramic body. The increase in densification rate and amount of mullite crystals provides a high crystalline to glass phase ratio. Three ceramic sanitaryware compositions were prepared to examine hightemperature deformation properties, such as the tendency for pyroplastic deformation and pyroplastic index, using an optical fleximeter
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