Synthesis of Me Doped Mg(OH)2 Materials for Thermochemical Heat Storage

Abstract

In order to investigate the influence of metal (Me) doping in Mg(OH)2 synthesis on its thermochemical behavior, Ca2+, Co2+ and Ni2+ ions were inserted in Mg(OH)2 matrix and the resulting materials were investigated for structural, morphological and thermochemical characterization. The densification of the material accompanied by the loss in porosity significantly influenced the hydration process, diminishing the conversion percentage and the kinetics. On the other hand, it increased the volumetric stored/released heat capacity (between 400 and 725 MJ/m3), reaching almost three times the un-doped Mg(OH)2 value.

Tuning Mg(OH)2 Structural, Physical, and Morphological Characteristics for Its Optimal Behavior in a Thermochemical Heat-Storage Application

“…For consistency with prior studies [ 22 , 28 , 32 , 35 , 37 ], the examined samples were compared with regard to the reacted fraction ( )) defined by Equation (5): where was named the instantaneous real mass change and was named the theoretical mass change owing to the dehydration of 1 mol Mg(OH) 2 , correspondingly indicated by Equations (6) and (7): where and were correspondingly named the initial sample mass and the instantaneous mass in thermogravimetric (TG) analysis; whereas, and were named correspondingly the molecular weight of Mg(OH) 2 and MgO.…”

“…Shkatulov et al recently worked on doped magnesium hydroxide, with the best results using LiNO 3 doping to tune its thermogravimetric performance [ 31 ]. In our previous studies, we investigated the influence of metal doping in Mg(OH) 2 synthesis, examining the thermochemical comportment, depending on different structural, morphological as well as thermochemical characteristics [ 32 ]. To determine if the thermochemical behavior of Mg(OH) 2 may be improved without chemical doping, Müller and co-workers systematically studied the dehydration conditions’ effects on the subsequent rehydration reaction [ 33 ].…”

Effect of Lithium Compound Addition on the Dehydration and Hydration of Calcium Hydroxide as a Chemical Heat Storage Material

“…They also inserted Ca 2+ , Co 2+ , and Ni 2+ ions into the Mg­(OH) 2 matrix to investigate the influence of metal doping in Mg­(OH) 2 synthesis on its thermochemical behavior. It increased the volumetric stored/released heat capacity (between 400 and 725 MJ/m 3 ), reaching almost three times the undoped Mg­(OH) 2 value . Haruki et al .…”

“…It increased the volumetric stored/released heat capacity (between 400 and 725 MJ/m 3 ), reaching almost three times the undoped Mg(OH) 2 value. 20 Haruki et al measured the effective thermal conductivities of pelletized magnesium hydroxide/expanded graphite (EG) and magnesium oxide/EG composite heat storage materials with high packing densities. 21 Mejia et al encapsulated CaO as a chemical heat storage material to address the low thermal conductivity and cohesiveness of the powder bulk material.…”

“…Chemical heat storage technology uses endothermic/exothermic reactions associated with reversible chemical reactions, particularly gas–solid reactions . Several reaction systems including CaCO 3 /CaO, − MgSO 4 ·7H 2 O/MgSO 4 , − and Mg­(OH) 2 /MgO, − have been studied as chemical heat storage systems. Material modifications aimed at improving the performance of chemical heat storage systems have been reported in a number of publications.…”