Mechanism of Magnesium Oxide Hydration Based on the Multi-Rate Model

Abstract

The hydration of different active MgO under an unforced and ultrasonic condition was conducted in this paper to investigate the chemical kinetics model of the apparent reaction and discuss the mechanism combined with the product morphology. The dynamics fitting result shows that both the first-order and multi-rate model describe the hydration process under ultrasound well, while only the multi-rate model was right for the hydration process under an unforced condition. It indicated that the rate order of hydration was different in the hydration process under an unforced condition. The XRD and SEM show that the MgO hydration was a process of dissolution and crystallization. Part of the magnesium ions produced by dissolution of MgO did not diffuse into the solution in time, and adhered to the magnesium oxide surface and grew in situ instead. As a result, the difference in the hydration rate of the remaining MgO particles becomes wider and not in the same order (order of magnitude). The ultrasonic cavitation could prevent the in-situ growth of Mg(OH)2 crystal nuclei on the surface of MgO. It not only greatly improved the hydration rate of MgO and produced monodisperse Mg(OH)2 particles, but also made the first-order kinetics model fit the hydration process of MgO well.

Prolonging Bacterial Viability in Biological Concrete: Coated Expanded Clay Particles

“…6 (MgO) was produced of a moderately reactive MgO (5 g) and water (10 g) mixture. This suspension was stirred for 10 min at room temperature, which possibly led to a partial hydration rate of MgO of about 10–30% [ 23 ]. The short exposure to water ensured that MgO constituted the largest part of coating No.…”

Metal–Organic Framework-Derived MgO/Mg(OH)2@Nanoporous Carbon for High Thermal Energy Release

“…In the hydration process, the MgO nanoparticles are converted to Mg(OH) 2 with a sheetlike morphology, which corresponds to the brucite structure as confirmed by the SAED pattern (Figure 3e−g). As reported in the literature, 37,38 water dissociates into OH − and H + during hydration, and then H + reacts with MgO to generate Mg 2+ ions on the surface of the crystals. Then, the Mg 2+ ions readily complex with six OH-ions, forming the Mg(OH) 6 4− growth units.…”

Effect of the MgO/Silica Fume Ratio on the Reaction Process of the MgO–SiO2–H2O System

“…The laws of thermodynamics can predict the probability of a reaction, as well as the final state achieved when the reaction is completed. These laws are often used in analyzing cement-based materials [27,28,29]. Consequently, they were employed in the analysis of the reaction of the MgO–SiO 2 –H 2 O system in this study.…”