Preparation of low-temperature composite phase change materials (C-PCMs) from modified blast furnace slag (MBFS)

Abstract As widely used in building materials, blast furnace slag (BFS) has the potential to prepare composite phase change materials (C-PCMs), which can be applied in thermal energy storage field. However, the defects of insufficient porosity and small pore volume of the BFS have severely limited the PCMs adsorption capacity. In this study, the BFS was modified by Ca(OH)2 to improve the PCMs adsorption capacity. The results showed that the porous structure of BFS was significantly improved after modification. And the apertures of BFS were distinctly enlarged and vast irregular slit-shaped pores emerged, which significantly increased the paraffin adsorption capacity. The MBFS could hold about 26.4% paraffin when 10% Ca(OH)2 was added as modifier, which was almost double compared with the BFS. The melting temperature and latent heat of paraffin/MBFS C-PCMs were determined as 51.9 °C and 36.4 J/g. And the prepared C-PCMs could maintain good thermal reliability even after 100 thermal cycles, which presented a potential application in the thermal energy storage fields like building energy conservation and solar energy storage.