A n-octadecane/hierarchically porous TiO2 form-stable PCM for thermal energy storage

• Published in: Renewable energy Vol. 145; pp. 1465 - 1473
• Main Authors: Li, Chaoen, Yu, Hang, Song, Yuan, Wang, Meng, Liu, Zhiyuan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2020
• Subjects: adsorption; chemical bonding; crystallization; desorption; enthalpy; Fourier transform infrared spectroscopy; Hierarchically porous; Interfacial interaction; latent heat; melting; nanopores; Phase change materials (PCM); renewable energy sources; scanning electron microscopy; surface tension; thermal conductivity; thermal energy; Thermal energy storage; TiO2; titanium dioxide; transmission electron microscopes; X-ray diffraction; Hierarchically porous; Thermal energy storage; Phase change materials (PCM); Interfacial interaction; TiO2
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2019.06.070

For a phase-change material (PCM) confined in a porous structure, the interfacial interactions between the PCM and the porous skeleton are the decisive factors in latent heat storage performance. In this work, a novel composite PCM based on hierarchically porous TiO2 and n-octadecane was successfully synthesized. The porous TiO2 was prepared by a soft-template method, and the composite PCM was fabricated by introducing n-octadecane under vacuum. Transmission electron microscope and X-ray diffraction (XRD) results revealed that the as-prepared supporting matrix was crystalline TiO2, and N2 adsorption/desorption isotherms indicated that TiO2 has a hierarchically porous structure. For composite PCMs, Fourier transform infrared spectroscopy and XRD spectra revealed that no chemical bonds were formed between n-octadecane and TiO2. Scanning electron microscopy results showed abundant n-octadecane enclosed within the nanopores and closely bound on the surfaces of the hierarchically porous TiO2, as a result of capillary forces and interfacial tension. Porous TiO2 exhibited high adsorption for n-octadecane (50 wt%), and the relative enthalpy of the composite PCM was as high as 85.8 J/g. Compared with pure n-octadecane, the thermal conductivity of the as-prepared composite PCMs (e.g., 50 wt% n-octadecane sample) was improved by 138% with the addition of porous TiO2. After 800 melting/solidifying cycles, the composite PCMs exhibited excellent thermal reliability and high enthalpy. The influence of the TiO2 pore structure on n-octadecane crystallization behavior is shown in the results. •Hierarchically porous TiO2 nanomaterial provided an ideal skeleton.•A novel n-octadecane/hierarchically porous TiO2 composite PCMs was synthesized.•The effect of the nanoporous structure on crystallization is demonstrated.