Investigating the effect of CaO/MgO ratio on the structure and final properties of wall tile bodies in rapid firing using Zanjan talc and Abbas Abad calcium carbonate as primary sources

Abstract

Abstract Introduction: In this research, the simultaneous effect of CaO and MgO as the main oxides that activate the reactions during rapid firing of ceramic tiles on the path of transformations and the formation of the beneficial phase of Anorthite and the reduction of the harmful phase of Gehlenite was studied. Methods: Calcium carbonate was chosen as a source of CaO oxide and talc powder as a source of MgO. After forming with a press, the mixtures were heat treated and the bodies were sintered. XRD, Dilatometery and SEM/FESEM analysis methods were used to evaluate the mechanism of product formation. The phases of the manufactured bodies were identified by X-ray diffraction test. The weight percentage of constituent phases was calculated through Maud software. Findings: Investigations showed that with decreasing CaO/MgO ratio, the weight percentage of Anorthite phase increased. Similarly, with the decrease of CaO/MgO ratio, the coefficient of thermal expansion decreased. So that the lowest coefficient of thermal expansion (7.75 x 10-6 units per degree Celsius) was reported. Microstructural investigations showed that by fine-granulating the primary sources of calcium carbonate and talc, the harmful Gehlenite phase was removed from the final microstructure and the Anorthite phase increased (up to 10% by weight). Likewise, the crystals of Anorthite phase have grown more.

Keywords

• wall tiles
• dilatometry
• water absorption
• thermal expansion
• firing shrinkage
• flexural strength