Novel PEG/SiO2/SiO2–modified expanded graphite composite phase change materials for enhanced thermal energy storage performance
摘要
A binary porous material of SiO2 and SiO2–modified expanded graphite (MEGR) was simultaneously prepared based on a low-cost and template-free approach in which a commercially abundant sodium silicate was used as a SiO2 precursor in the presence of expanded graphite (EGR). The polycondensation and excessive aggregation of SiO2 on the surfaces of EGR enabled the formation of highly interconnected porous networks. Besides, the hydrophilicity of MEGR was improved due to the presence of multiple silanol groups from anchored SiO2. The SiO2/MEGR was then used as a binary porous support for the adsorption and stabilization of polyethylene glycol (PEG), forming composite phase change materials (CPCMs) for thermal energy storage. The prepared PEG/SiO2/MEGR CPCMs were investigated for thermal properties with varying PEG content (50–90%) and a fixed SiO2:MEGR ratio of 75:25. The presence of MEGR with desirable porous structure and improved hydrophilicity contributed to the PEG adsorption capacity of SiO2/MEGR. Indeed, the loading of PEG was improved from 60% of pristine SiO2 to 80% of SiO2/MEGR. In addition, the thermal conductivity of the 80% PEG/SiO2/MEGR composite was enhanced to 2.865 W/m K, which was 11.2 times greater than that of pure PEG. Furthermore, the PEG/SiO2/MEGR composite retained high thermal stability and excellent thermal reliability after 500 melting/crystallization cycles. The facile preparation and high thermal performance make the PEG/SiO2/MEGR composite competitive for thermal energy storage applications.