Size-dependent photonic and radiative properties of CaO, SiO2, Al 2 O 3 and Fe 2 O 3 cementitious oxides

The photonic properties of the cement-forming oxides CaO, SiO 2 , Al 2 O 3 , and Fe 2 O 3 are presented in the context of photonic metaconcrete (PMC) and radiative cooling applications. The design of an efficient PMC with novel optical properties is based on the size dependence of the light–matter interaction. We use Mie theory to study the scattering properties, and Hapke model is used to study the emissivity of nano- and microparticles from the infrared (IR) to the ultraviolet and visible (UV–Vis) spectra. The IR and UV–Vis responses of the cement-forming oxides were obtained using the density functional theory and many-body perturbation theory. We model the size-dependent reflectance and emissivity in both air and C-S-H gel-like media. Nanoparticles of the wide band gap insulators CaO, SiO 2 and Al 2 O 3 exhibit efficient scattering of UV–Vis light within a radius range of 120–450 nm. Additionally, CaO nanoparticles effectively scatter NIR light, which makes them a promising material for reflecting solar radiation. Our results provide key tips for the engineering of highly reflective and selectively radiating photonic composites.