Eberbach Michaela C, Shkatulov Aleksandr I, Tinnemans Paul, Huinink Hendrik P, Fischer Hartmut R, Adan Olaf C G
Eindhoven University of Technology, Den Dolech 2, 5600 MB Eindhoven, The Netherlands.
EIRES, Horsten 1, 5612 AX Eindhoven, The Netherlands.
Cryst Growth Des. 2025 Mar 27;25(8):2409-2417. doi: 10.1021/acs.cgd.4c01522. eCollection 2025 Apr 16.
Due to climate change and the energy transition, energy storage applications are being studied and developed. One energy storage application is a heat storage battery, which needs materials that can store and release heat with high energy storage capacity. One such material is a salt hydrate. The hydration pathways of salt hydrates can have different numbers of steps. There are salts with single-hydrate steps like for CuCl (0-2) and LiBr (0-1) and multihydrate steps like for MgCl (0-2-4-6) and SrCl (0-1-2-6). Additionally, there are also salts with complex hydration-dehydration pathways like for CaCl (0-1/3-2-1-0). Little is known about the hydrate steps of CaBr. The crystal structures of the CaBr nona-, hexa-, and anhydrate are known, but there are no intermediate steps and conditions for these transitions. The hexahydrate and anhydrate have the same structure as CaCl except for the unit cell size due to the different anions. Additionally, the equilibria were determined for the hexa-, tetra-, and dihydrate transitions. However, the intermediate steps are debated. The hydrates 3, 1.5, 1, and 0.5 were all proposed but are disputed and not verified. Therefore, the hydration and dehydration pathways of CaBr from the anhydrate to the dihydrate and back were examined in this study for both the bulk salt and the confinement of mesoporous silica gels. The kinetic phase transition onsets and equilibrium lines were measured for the bulk salt. Powder X-ray diffractograms were used to ensure that the same structures were formed every time during hydration and dehydration. Single-crystal analysis was used to determine the crystal structures of the hydrates. These experiments showed only a stable monohydrate phase between the anhydrate and dihydrate during hydration and dehydration. Furthermore, the dihydrate has the same crystal structure as the dihydrate of CaCl except for the size, while the monohydrate differs from the CaCl monohydrate. Additionally, the composites' kinetic onsets and powder diffractograms were measured, which showed that CaBr performs the same hydrate steps in confinement as in bulk form.
由于气候变化和能源转型，储能应用正在被研究和开发。一种储能应用是蓄热电池，它需要能够以高储能容量储存和释放热量的材料。一种这样的材料是水合盐。水合盐的水合途径可以有不同数量的步骤。有像CuCl（0 - 2）和LiBr（0 - 1）这样具有单水合步骤的盐，以及像MgCl（0 - 2 - 4 - 6）和SrCl（0 - 1 - 2 - 6）这样具有多水合步骤的盐。此外，还有像CaCl（0 - 1/3 - 2 - 1 - 0）这样具有复杂水合 - 脱水途径的盐。关于CaBr的水合步骤知之甚少。CaBr九水合物、六水合物和无水物的晶体结构是已知的，但这些转变没有中间步骤和条件。六水合物和无水物除了由于阴离子不同导致晶胞尺寸不同外，与CaCl具有相同的结构。此外，还确定了六水合物、四水合物和二水合物转变的平衡。然而，中间步骤存在争议。水合物3、1.5、1和0.5都被提出过，但存在争议且未得到验证。因此，本研究针对块状盐以及介孔硅胶的受限情况，研究了CaBr从无水物到二水合物再返回的水合和脱水途径。测量了块状盐的动力学相变起始点和平衡线。使用粉末X射线衍射图来确保在水合和脱水过程中每次都形成相同的结构。使用单晶分析来确定水合物的晶体结构。这些实验表明，在水合和脱水过程中，无水物和二水合物之间仅存在稳定的一水合物相。此外，二水合物除了尺寸外，与CaCl的二水合物具有相同的晶体结构，而一水合物与CaCl的一水合物不同。此外，还测量了复合材料的动力学起始点和粉末衍射图，结果表明CaBr在受限情况下与块状形式执行相同的水合步骤。
