Temperature and common-ion effect on magnesium oxide (MgO) hydration

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• 作者：L.F. Amaral ; I.R. Oliveira ; R. Salomã ; o ; E. Frollini ; V.C. P ; olfelli
• 关键词：A. Suspensions ; C. Chemical properties ; D. MgO ; E. Refractories
• 刊名：Ceramics International
• 出版年：2010
• 出版时间：April 2010
• 年：2010
• 卷：36
• 期：3
• 页码：1047-1054
• 全文大小：453 K

文摘

MgO based refractory castables draw wide technological interest because they have the versatility and installation advantages of monolithic refractories with intrinsic MgO properties, such as high refractoriness and resistance to basic slag corrosion. Nevertheless, MgO easily reacts with water to produce Mg(OH)₂, which is followed by a large volumetric expansion, limiting its application in refractory castables. In order to develop solutions to minimize this effect, a better understanding of the main variables involved in this reaction is required. In this work, the influence of temperature, as well as the impact of the chemical equilibrium shifting (known as the common-ion effect), on MgO hydration was evaluated. Ionic conductivity measurements at different temperatures showed that the MgO hydration reaction is accelerated with increasing temperature. Additionally, different compounds were added to evaluate their influence on the reaction rate. Among them, CaCl₂ delayed the reaction, whereas KOH showed an opposite behavior. MgCl₂ and MgSO₄ presented similar results and two other distinct effects, reaction delay and acceleration, which depended on their concentration in the suspensions. The results were evaluated by considering the kinetics and the thermodynamics of the reaction, and the mechanical damages in the samples that was caused by the hydration reaction.