Microencapsulation of high temperature metallic phase change materials with SiCN shell

Abstract

Metallic phase change materials (PCMs) have the advantages of large phase change latent heat, high heat storage density and broad application prospects in various high temperature industrial waste heat recovery and utilization. However, due to the strong corrosion of molten metal at high temperature, appropriate packaging technology is the prerequisite for the promotion and application of metallic PCMs. In this research, a high temperature PCM microencapsulating technology with SiCN shell and a new microencapsulation method was proposed. The high temperature microencapsulated phase change materials (MEPCMs) with the core–shell mass ratios of 5:1, 4:1 and 3:1 were prepared by “solvent evaporation-heating curing” method, using SiCN cured by organic polysilazane (OPSZ) as heat resistant shell material and Al-Si particles as core PCMs. The mechanisms of shell formation and coating of OPSZ were studied experimentally, as well as the material properties and thermal performance of MEPCMs. With the increase of temperature, OPSZ gradually formed a dense SiCN shell on the surface of Al-Si particles. The experimental results showed that MEPCMs with the core–shell mass ratio of 4:1 had a high phase change temperature (571.9 °C-573.7 °C) and good heat storage capability (281.2 J/g-282.9 J/g). SiCN shell was conducive to maintain a complete core–shell structure, and exhibited excellent thermal resistance and oxidation resistance to protect inner core materials during thermal cycles. Therefore, the prepared microcapsule was a potential heat storage material, which provided a new idea for developing microencapsulation method of high temperature PCMs.