Microstructural and thermal response evolution of metallic form-stable phase change materials produced from ball-milled powders

Phase change materials (PCMs) can store and release the latent heat associated with a phase transition, so they can be applied in thermal energy management and storage systems. Among them, form-stable (FS) PCMs can consist of two immiscible phases: an active phase, which undergoes the solid–liquid transition, and a matrix, which provides the structural properties and prevents leakage of the active phase when it is liquid. This experimental study focused on the characterization of a metallic FS-PCMs based on an Al–Sn alloy, obtained by powder metallurgy from ball-milled powders, compacted at room temperature and sintered at 200, 250 and 500 °C. The main properties that characterize PCMs are the temperature range over which transition occurs and the associated enthalpy, i.e. the stored energy. Differential scanning calorimetry (DSC) is one of the more suitable characterization techniques to evaluate these properties and so the thermal response of PCMs. To check thermal response and its stability, DSC tests including several thermal cycles were conducted. DSC analyses were performed also before and after several thermal cycles simulating possible operative conditions. Moreover, microstructural analysis, through scanning electron microscopy and X-ray diffraction, allowed to relate the thermal response variations to microstructural and mechanical changes.