Enhancing the Thermal Characteristics of Shape-Stabilized Phase Change Nanocomposite Nanofibers by Incorporation of Multiwalled Carbon Nanotubes within the Nanofibrous Structure

Thermo-active Smart Electrospun Nanofibers

The recent burst of research on smart materials is a clear evidence of the growing interest of the scientific community, industry, and society in the field. The exploitation of the great potential of stimuli-responsive materials for sensing, actuation, logic, and control applications is favored and supported by new manufacturing technologies, such as electrospinning, that allows to endow smart materials with micro- and nano-structuration, thus opening up additional and unprecedented prospects. In this wide and lively scenario, this article systematically reviews the current advances in the development of thermo-active electrospun fibers and textiles, sorting them, according to their response to the thermal stimulus. Hence, several platforms including thermo-responsive systems, shape memory polymers, thermo-optically responsive systems, phase change materials, thermoelectric materials, and pyroelectric materials, have been described and critically discussed. The difference in active species and outputs of the aforementioned categories has been highlighted, evidencing the transversal nature of temperature stimulus. Moreover, the potential of novel thermo-active materials has been pointed out, revealing how their development could take to utmost interesting achievements. This article is protected by copyright. All rights reserved.

Nanoencapsulation of phase change materials (PCMs) and their applications in various fields for energy storage and management

Today, the use of phase change materials (PCMs) with remarkable properties for energy storage and development of engineering systems is an extremely important topic, due to enhanced demand for energy consumption. PCMs could be generally subdivided into solid-liquid, liquid-gas, solid-gas, and solid-solid groups. It should be noted that since there is no single excellent PCM that comprises all the suitable physical, chemical, kinetic, thermal, and economic properties, PCMs could be improved by incorporating some additives, modifying PCM structures, and optimizing the storage systems. Nanoencapsulation of PCMs, as an effective technique, can increase their thermal conductivity, barricades their leak during the melting operation, and their possible interactions with the surrounding matrix. Furthermore, there are several methods for fabricating nanocapsules loaded with PCMs including chemical (i.e., emulsion polymerization, mini-emulsion polymerization, in situ polymerization, and interfacial polymerization), physicochemical (sol-gel entrapment), and physicomechanical techniques (electrohydrodynamic processes). Accordingly, the energy storage and release of nanoencapsulated PCMs has been become an important field in many applications such as electronic devices, food industry, buildings, solar energy storage, heat exchangers, packed bed designs, space systems, textiles, etc. This study has been focused on various PCMs, their nanoencapsulation methods, phase change fibers, as well as their potential applications in energy storing and management goals in various fields.

Preparation of Anisotropic Aerogels with Pristine Graphene by Heat Flow and Study of Their Effects on Heat Transfer in Paraffin

In this study, anisotropic graphene/graphene oxide (GO) aerogels (AGAs) were obtained by freeze-drying after direct participation of pristine graphene in the self-assembly of anisotropic gel by the heat flow method. After vacuum microwave treatment, the physical, chemical and structural characteristics of the AGAs were investigated. The results show that AGAs, in which the internal graphene sheets are parallel to the heat flow direction, are successfully prepared. After microwave treatment, the amount of oxygen and nitrogen reduces significantly and the sp2 domain increases. However, at the same time, many fragments and holes are generated in the graphene sheets. The effects of AGAs on the phase transition of paraffin is studied, and the results show that the melting enthalpy, solidification enthalpy and initial melting temperature of AGA/paraffin composites decreases as the GO content in the AGAs increases, whereas the melting range, solidifying range and subcooling degree increases. The highest axial thermal conductivity of the AGA/paraffin composite is 1.45 W/(mK), and the thermal conductivity enhancement efficiency is 884% (AGA content was 0.53 vol %). Compared with previously investigated, similar AGA/paraffin composites, the aerogels fabricated in this study have the obvious advantages of a simple fabrication process, a low cost and a high thermal conductivity enhancement efficiency. These aerogels possess the potential for application in phase-change energy storage (PES), thermal energy management and other fields.