ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Novel PEG/SiO₂/SiO₂–modified expanded graphite composite phase change materials for enhanced thermal energy storage performance

Giang Tien Nguyen, Nhung Thi Tran, and Le Minh Tam

Faculty of Chemical and Food Technology, Ho Chi Minh City University of Technology and Education (HCMUTE), Ho Chi Minh City, Vietnam

E-mail: ntgiang@hcmute.edu.vn

Received: 26 October 2023  Accepted: 10 April 2024

Abstract:

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.

Keywords: Silica; Expanded graphite; Polyethylene glycol; Thermal energy storage; Phase change material

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-024-03460-z

Chemical Papers 78 (9) 5219–5231 (2024)