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- Title
Kinetic study of the magnesium oxychloride cement cure reaction.
- Authors
Góchez, Roque; Wambaugh, Jim; Rochner, Brett; Kitchens, Christopher
- Abstract
Magnesium oxychloride (MOC) is a ceramic material with significant fire-resistant properties and growing potential as an alternative building material for passive fire protection systems. The present study examined the magnesium oxychloride 5-phase cure reaction at temperatures from 35 to 55 °C using time-resolved quantitative X-ray diffraction and differential scanning calorimetry to monitor kinetics. The reaction was characterized as a two-step process: dissolution of magnesium oxide followed by crystallization of magnesium oxychloride from the solvated state. With stoichiometric proportions, 37% of the MgO dissolves before the onset of crystallization at a critical amorphous concentration. A maximum crystallinity of 82-84% was achieved for each temperature. Assuming first-order kinetics for both MgO dissolution and MOC crystallization, a kinetic model predicts 42.4 and 26.1 kJ/mol for dissolution and crystallization activation energies, respectively. This model was applied to pilot-scale production and accurately predicts the cure reaction time as a function of cure temperature. In an alternative approach to modeling the cure reaction, the Avrami nucleation and growth model was fit to calorimetric measurements. This model predicts diffusion-controlled, one-dimensional growth with an activation energy of 72.4 kJ/mol, which accounts for both dissolution and crystallization.
- Publication
Journal of Materials Science, 2017, Vol 52, Issue 13, p7637
- ISSN
0022-2461
- Publication type
Academic Journal
- DOI
10.1007/s10853-017-1013-x