Designing of passive cooling silicon oxynitride composite cement

Si₂N₂O, which shows high radiative cooling ability, was mixed and hardened with ordinary Portland cement to prepare cement specimens having radiative cooling abilities. The bulk cement specimens were prepared with diameters of 50 mm and two different thicknesses of 3 and 10 mm, and Si₂N₂O powder were mixed with 2 and 10 wt%. The temperatures of the blank specimen (without radiative cooling Si₂N₂O powder) and the cement composite specimens were measured in a thermostatic chamber maintained at ambient temperature, and the radiative cooling abilities of the specimens were evaluated. The obtained specimens showed a radiative cooling ability in the range 0.077–0.92 W/m²; thus, the results of this study suggested the possibility of a cement composite with passive cooling property.