Fabrication and characterization of electrospun SiO2 nanofibers absorbed with fatty acid eutectics for thermal energy storage/retrieval

Abstract

Electrospun SiO2 nanofibers (in the form of overlaid mat) absorbed with fatty acid eutectics were studied to fabricate form-stable phase change materials (PCMs) for storage and retrieval of thermal energy. The SiO2 nanofibers were made via electrospinning of precursor nanofibers followed by pyrolysis, while four fatty acid eutectics of capric acid–lauric acid (CA–LA), capric acid–myristic acid (CA–MA), capric acid–palmitic acid (CA–PA), and capric acid–stearic acid (CA–SA) were studied as the model PCMs. The morphological structure, absorption capacity, thermal energy storage property, and thermal energy storage/retrieval rates of the developed form-stable composite PCMs were characterized by scanning electron microscopy, differential scanning calorimetry, and measurement of melting/freezing time. The results indicated that the electrospun SiO2 nanofibrous mats were highly porous and capable of absorbing a large amount of PCMs, and the absorption capacities of SiO2 nanofibers for the four fatty acid eutectics (i.e., CA–LA, CA–MA, CA–PA and CA–SA) were 82.0, 83.7, 84.2, and 83.1%, respectively. The experimental values of heat enthalpy for the fabricated composite PCMs were slightly lower than the corresponding theoretical values, whereas there were no appreciable changes on phase transition temperatures. In comparison with fatty acid eutectics (without supporting materials), the melting and freezing time periods of the corresponding CA–LA/SiO2, CA–MA/SiO2, CA–PA/SiO2, CA–SA/SiO2 were shortened by 28.6% and 30.8%, 20.0% and 44.4%, 62.5% and 50.0%, and 50.0% and 33.3%, respectively. This study suggested that the fabricated form-stable composite PCMs possessed appropriate phase transition temperatures and high heat enthalpy values; hence, they would have potential applications for low-temperature thermal energy storage/retrieval.