Structural transformations preparing the dehydration of Ca(OH)₂

Review on thermal properties and reaction kinetics of Ca(OH)2/CaO thermochemical energy storage materials

“…The structural diagram of Ca(OH) 2 is shown in Figure 1. 2 Ca atoms are located at the origin, while O and H atoms are located at fixed positions in space. Galwey et al 3 pointed out that in the decomposition process of calcium hydroxide, there are only two states: calcium hydroxide and calcium oxide, as well as the intermediate [CaO ⋅ H 2 O] inferred based on thermodynamics.…”

“…Dehydration reaction is the process that ultimately forms an interconnected network, opening up a fast diffusion channel for water molecules to migrate to the surface. Desgranges et al 2 achieved local characterisation of crystal surfaces perpendicular to the a and c directions using high-resolution X-ray diffraction at room temperature. The results indicate that there are two types of domains on the surface parallel to the hexagonal cleavage plane, which may lead to temperature-dependent changes in the coefficient of thermal expansion.…”

“…In particular, the calcium oxide hydration/dehydration reaction was proposed by Ervin et al in the late 70s [10][11][12][13] as the basis of some thermochemical energy storage systems. [10][11][12][13][14][15][16][17][18][19][20][21] The main advantages of this reversible reaction couple are its high reversibility and fast reaction rates, 22 high reaction enthalpy (ΔH = 1400 kJ/kg), which allows large energy storage densities and appropriate charge and discharge temperatures (400-550°C…”

“…The crystal structure of calcium hydroxide in the reaction equation is CdI2 type, belonging to the hexagonal crystal system. The structural diagram of Ca(OH) 2 is shown in Figure 1 2 . Ca atoms are located at the origin, while O and H atoms are located at fixed positions in space.…”

“…Dehydration reaction is the process that ultimately forms an interconnected network, opening up a fast diffusion channel for water molecules to migrate to the surface. Desgranges et al 2 . achieved local characterisation of crystal surfaces perpendicular to the a and c directions using high‐resolution X‐ray diffraction at room temperature.…”