Polyethylene Glycol Confined in SiO<sub>2</sub>–Modified Expanded Graphite as Novel Form–Stable Phase Change Materials for Thermal Energy Storage
Giang Tien Nguyen, Thi Ai Nhi Truong, Nguyen Duy Dat, Thi Anh Dao Phan, Trung Huu Bui
Abstract
High Resolution Image Download MS PowerPoint Slide Form–stable phase change materials (FSPCMs) composed of poly(ethylene glycol) (PEG) encapsulated in SiO 2 -modified expanded graphite (EG@SiO 2 ) were prepared and investigated for thermal energy storage behaviors. The modification of SiO 2 on EG was done using a simple sol–gel method, and then the resulting EG@SiO 2 was introduced to confine PEG at varying content (60–90 wt %). Surface properties (including microstructure, morphology, and functional groups), PEG adsorptivity, leakage-proof ability, and thermal energy storage of the prepared materials were thoroughly characterized and discussed. The EG@SiO 2 with 15 wt % SiO 2 outstandingly adsorbed PEG as compared to the pristine EG, showing up >80 wt % of PEG. As a result, PEG was well stabilized in EG@SiO 2 porous network without leakage, owing to capillary force, surface tension, and hydrogen bonding interactions. The optimal 80 wt % PEG/EG@SiO 2 composite possessed high crystallinity (93.5%), high thermal energy storage capacity (132.5 J/g), and excellent thermal conductivity (4.086 W/m·K). In addition, it exhibited good cycling durability after 500 repeated melting/crystallization cycles. The high thermal efficacy and inexpensiveness would make the PEG/EG@SiO 2 FSPCMs suitable for scale–up applications in thermal energy storage.