مواد نوین (Apr 2023)
Investigating the effect of different sources of magnesium oxide on the structure and final properties of wall tile bodies containing CaO using rapid firing method
Abstract
Abstract Introduction: In this research, the effect of different sources of magnesium oxide and the effect of CaO/MgO ratio, as the main oxides that activate the reactions during wall tile firing, on the path of transformations and the formation of useful phases such as Anorthite, Diopside, and Wollastonite, and the reduction of the destructive phase of Gehlenite and free quartz was studied. Methods: Three groups with 12% wt. of calcium carbonate - as the main source of CaO supply - and different weight percentages (5, 7 and 10%) from local soils supplying MgO in Iran (Zanjan talc, Boroujard talc and Abdol-Abad dolomite) were built. After forming with a press, the mixtures were sintered in a fully industrial process and in a fast firing furnace. By means of X-ray diffraction test and with the help of Rietveld refinement method which was carried out in Maud software, the weight percentage of the forming phases of the final microstructure was quantitatively calculated. Findings: In the samples containing talc, with the increase of the weight percentage of talc and the decrease of CaO/MgO ratio, the weight percentage of Anorthite and Gehlenite phase increased and the Diopside phase decreased. Also, the coefficient of thermal expansion and moisture expansion test decreased by decreasing the ratio of CaO/MgO. In samples containing dolomite, increasing the weight percentage of CaO oxide, despite the acceptable weight percentage of MgO oxide, led the tendency of the structure towards the formation of more calcium aluminosilicates such as Anorthite and Gehlenite. The extreme increase of Gehlenite phase (6% wt.) caused a large increase in thermal expansion coefficient (8.35 x 10-6 units/degree Celsius) and moisture expansion percentage (0.12%) in the sample with 10%wt. dolomite.
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