Phase change materials (PCMs) can be used for high-density heat absorption and release during transition in state of matter without fluctuation in working temperature, behaving as good candidates for thermal energy storage in a broad range of applications, like solar energy storage, waste heat harvest, temperature control for electronic devices and catalyst performance, etc. The most studied convention PCMs, such as organic compounds, inorganic salts and salt hydrates, are facing the following problems: (1) low thermal conductivity, resulting in the slow response to the heat source; (2) limited range of working temperature. Metal PCMs show high thermal conductivity and thermal energy storage density by weight, which are good candidates for the rapid heat storage in compact systems. For better use of PCMs, various forms like powder, paste, slurry and nanofluid, need to be designed, in which PCMs are decreased to micro or nano scale in size. To keep the designated form and avoid leakage or sintering of metallic PCMs in nano or micro scale, structure design like creating stable isolation or protection is an effective way to stabilize the PCM structure and morphology during melt-freeze cyclic operation. The purpose of this research is to design the isolation/protection oxide structures for stabilizing low melting point metallic PCM micro/nano particles, thus, to effectively enhance their thermal stability during the melt-freeze cyclic working condition. Silica and alumina as stable oxide materials are chosen for the stabilization of low melting point metal nanoparticle (NP) and microparticle PCM. The Sn NPs@SiO2 particles were prepared by hydrogen reduction process of SnCl2-absorbed porous silica spheres, which had the silica spherical structure with Sn nanoparticles distributed (Figure 1a). The Sn@Al2O3 PCM particles with core-shell structure (Figure 1b) were fabricated in a 3-step method, including hydrothermal synthesis of SnO2 particles, boehmite treatment, air calcination and hydrogen reduction. The as-formed structures as well as formation mechanisms of both Sn NPs@SiO2 and Sn@Al2O3 were investigated. Furthermore, thermal energy storage properties and thermal stability were carefully examined. Both silica matrix and alumina shell act as the key roles for the enhancement of thermal storage stability of metal PCM. Our results show the great potential of Sn-based PCM particles in the high-temperature applications which are not suitable for organic PCMs.

Encapsulation of low melting point metal nano/micro particle phase change materials for thermal energy storage

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.