Development of core-shell type microencapsulated phase change material with Zn-30 mass% Al alloy and its shell formation mechanism

Abstract

Latent heat storage (LHS) technology is promising because it can store and release heat at a constant temperature utilizing phase change material (PCM) and is a superior alternative for sensible heat storage (SHS) technology. In this study, we report an improved preparation method for microencapsulated PCM (MEPCM) with Zn–30 mass% Al (melting temperature: 440–512 °C) as the PCM. Conventional MEPCM preparation involves boehmite treatment for 3 h in boiling water to form AlOOH shells on Zn–30 mass% Al alloy particles (average diameter: 35.7 μm) and heat-oxidation treatment to form an oxide shell in oxygen atmosphere at 800 °C. In this study, Al(OH)3 is added to the treatment solution before boehmite treatment; furthermore, precipitation treatment at 75 °C for 16 h is investigated. After heat-oxidation treatment, different Al and Zn oxide shells are formed on the surface of the alloy particles depending on the Al(OH)3 quantity added before boehmite treatment and precipitation treatment. The prepared MEPCM has a heat storage density of 0.48 GJ m−3 and excellent cyclic durability of >100 melting and solidification cycles. In addition to this, investigations related to the fabrication of composite PCM by mixing it with a glass frit was carried out for improving the durability of the MEPCM. Therefore, this material can be utilized in future medium-to-high temperature heat applications such as transportation, chemical processes, and renewable energy.