Microstructural insight into the thermal decomposition of MgCl2·6H2O examined by in-situ high-temperature X-ray powder diffraction

Karunadasa, Kohobhange S. P.; Rajapakse, R.M.G.; Pitawala, H.M.T.G.A.; Manoratne, C.H.

doi:10.1016/j.jssc.2023.123965

Cited by 7 publications

(3 citation statements)

References 26 publications

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“…To facilitate the evaluation of these alterations, the graphs have been subtracted (graph of the freeze-dried sample minus the graph of the raw sample) and the subtracted graph is also presented in Figure 2 . Most of the peaks are related to MgCl 2 ·6H 2 O and in Figure 2 , suggestively, the main peak (with the highest intensity at 21.64° corresponding to the (111) plane [ 19 ]) is highlighted. The peak at 15.35°, however, is not a diffraction peak of the crystal lattice of MgCl 2 ·6H 2 O.…”

Section: Resultsmentioning

confidence: 99%

“…The peak at 15.35°, however, is not a diffraction peak of the crystal lattice of MgCl 2 ·6H 2 O. This peak is the peak with the highest intensity of MgOHCl [ 19 ] corresponding to the (003) plane (also highlighted in Figure 2 ). The peak of MgOHCl with the second highest intensity is a double peak at around 31° corresponding to the (101) and (012) planes [ 19 ].…”

Section: Resultsmentioning

confidence: 99%

“…This peak is the peak with the highest intensity of MgOHCl [ 19 ] corresponding to the (003) plane (also highlighted in Figure 2 ). The peak of MgOHCl with the second highest intensity is a double peak at around 31° corresponding to the (101) and (012) planes [ 19 ]. These peaks overlap with the peaks of MgCl 2 ·6H 2 O (highlighted in Figure 2 ).…”

Section: Resultsmentioning

confidence: 99%

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Desolvation Inability of Solid Hydrates, an Alternative Expression for the Gibbs Free Energy of Solvation, and the Myth of Freeze-Drying

Tsioptsias

2024

Materials

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The term “desolvation inability” is proposed in order to describe the alteration of the original chemical structure of a solute (“decomposition”) prior to the solvent’s full removal upon the heating of the solvate. This behavior has been sporadically reported; however, it is much more frequent, and it is the basis of various, seemingly unrelated, effects/processes, e.g., the vinegar syndrome of cellulose acetate cinematographic films, in thermal energy storage. An explanation and a criterion/index for the prediction of this behavior are provided based on the comparison of the Gibbs free energies of decomposition and desolvation. A new approach for the expression of the Gibbs free energy of desolvation is proposed by reversing the roles of the solute and solvent and by regarding water as the solute rather than as the solvent, while the solute is treated as a solid solvent. This approach results in lower solvation/desolvation Gibbs free energy values. Based on the above, the experimentally observed thermal behavior of three inorganic hydrates is predicted and explained. Theoretically and experimentally, it is supported that decomposition is possible at sub-zero (°C) temperatures and the regarded simultaneous drying and protection of heat-sensitive substances by freeze-drying, at least in some cases, e.g., for the case of gallic acid, is an unverified myth.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%