Composite material “Mg(OH)2/vermiculite”: A promising new candidate for storage of middle temperature heat

• Published in: Energy (Oxford) 2012-08, Vol.44 (1), p.1028-1034
• Main Authors: Shkatulov, Alexandr, Ryu, Junichi, Kato, Yukitaka, Aristov, Yury
• Format: Article
• Language: English
• Subjects: Composite materials; Decomposition reactions; Differential scanning calorimetry; heat; Heat storage; Heat storage capacity; Hydroxides; magnesium; Magnesium hydroxide; melting; Middle temperature heat; Porosity; Precipitation; temperature; Thermal decomposition; Transformations; Vermiculite
• ISSN: 0360-5442
• DOI: 10.1016/j.energy.2012.04.045

New composite material for storage and transformation of heat of a temperature range of 250–350 °C has been synthesized by precipitation of magnesium hydroxide Mg(OH)2 in the pores of expanded vermiculite. The hydroxide is stabilized inside the pores as irregular sticks of 1–3 μm in size across flats of the base and about 30 μm in length. The temperature of decomposition of the confined hydroxide is found to be by some 50 °C lower than that of the bulk one as revealed by both TG and DSC techniques. One possible reason of this finding is a significant acceleration of the decomposition reaction of the confined hydroxide as revealed from comparative kinetic tests in the temperature range of 260–300 °C. The maximal heat storage capacity is 540 kJ per kg of the composite with the hydroxide content of 67.4 mass. % that is larger than the heat of melting for promising phase change materials. Further study of the new composite material for storage of middle temperature heat could be of high interest to find out reasons of the decomposition temperature reduction in order to use this effect for harmonizing the reaction temperature with the temperature level of heat to be stored. ► New heat storing material is obtained by precipitating Mg(OH)2 in vermiculite pores. ► The material structure and properties are studied by TG, DSC, SEM, XRD, and BET. ► The decomposition temperature of the confined Mg(OH)2 is by 50 °C lower than in bulk. ► The storage density (540 J/g-composite) is larger than this value for promising PCMs.