Phase change materials (PCMs) using metals/alloys have been concerned for medium temperature solar thermal storage and waste heat recovery. However, the PCMs may leak due to the solid-liquid phase change, which greatly limits the use of metallic PCMs. In this study, we report the synthesis of microencapsulated PCMs (MEPCMs) using metallic Sn as PCM core and a sol-gel coated SiO 2 as shell. The as-coated microcapsules are further undergone a high temperature heat treatment at oxygen/nitrogen atmosphere. Due to the self-repairing effect, the cracked microcapsules can be sealed and stabilized, thereby forming high stabilized MEPCMs over 100 cycles. The melting point and latent heat of the Sn@SiO 2 –O 2 microcapsules were around 233 °C and 56 J g -1 respectively, while the values were around 233 °C and 58 J g -1 for Sn@SiO 2 –N 2 microcapsules, similar to the theoretical values of metallic Sn. The successfully prepared Sn@SiO 2 MEPCMs could find wide applications in medium temperature thermal energy storage .
Zhenyou Li,Shiqi Zhang,Zijian Li,Haodong Tang,Zongjian Liu
Conventional synthesis of stable metal oxide-encapsulated metal particles typically requires two-stage processing: metal particle formation and oxide coating via a sol-gel method. However, this biphasic protocol is often time-consuming and environmentally unfriendly. Herein, a novel, one-step approach that enables concurrent metal particle formation and oxide encapsulation is proposed to synthesize TiO₂-encapsulated Sn-based particles. The proposed method involves ultrasonic emulsification of molten Sn or Sn alloys (e.g. Sn-Zn-Cu) within a LiCl-KCl-CsCl eutectic melt containing TiO₂ nanoparticles, followed by rapid emulsion solidification and salt matrix dissolution in water. Our results demonstrate that Sn-based capsules with diameters ranging from hundreds of nanometers to several micrometers and TiO₂ shell thicknesses typically in the range of 80–120 nm were successfully synthesized via such emulsion-based system, where the capsule size decreases with the concentration of TiO₂ nanoparticles. The as-prepared Sn-2.0Zn-1.5Cu (in wt%) phase change capsules exhibit significantly reduced undercooling (∼7 °C vs. ∼88 °C for Sn capsules of comparable size) and their phase change properties remain stable after 300 thermal cycles, thereby showing great potential for thermal energy storage applications. With short emulsification durations (<10 min) and recyclable chloride salts, this Pickering-type metal-in-salt emulsion methodology might serve as a new pathway for rapid and environmentally friendly synthesis of metal-based micro/submicro-capsules across diverse material systems by varying metal alloy compositions and selecting suitable nanoparticle stabilizers.
危险品化学品经营许可证（带存储）