This study compares the optical and radiative cooling performance of single-layer films embedded with TiO2 or Al2O3 nanoparticles dispersed in a polymer matrix and backed with an aluminum reflector. Optical constants of both materials were obtained from literature, and wavelength-dependent scattering efficiencies were calculated using Mie theory. A Monte Carlo ray-tracing simulation was performed to evaluate the spectral reflectance, absorptance, and emissivity of each film across the solar and thermal-infrared regions. The TiO2-based film exhibited strong visible-light scattering but suffered significant ultraviolet (UV) absorption, resulting in an average solar reflectance of ~0.90. In contrast, the Al2O3-based film showed negligible UV absorption and maintained high reflectance (> 0.95) throughout the 0.3-2.5 μm solar band, leading to a higher net cooling power of approximately 105 W/m² compared to 85 W/m² for TiO2. These results demonstrate that UV reflectance is a key determinant of effective radiative cooling and indicate that Al2O3-based coatings offer strong potential for passive cooling applications in buildings and agricultural environments.

This study examines the role of the nano- and micro-particle ratio in dispersion stability and mechanical properties of composite resins for SLA(stereolithography) 3D printing technology. VTES(vinyltriethoxysilane)-coated ZrO2 ceramic particles with different nano- and micro-particle ratios are prepared by a hydrolysis and condensation reaction and then dispersed in commercial photopolymer (High-temp) based on interpenetrating networks(IPNs). The coating characteristics of VTES-coated ZrO2 particles are observed by FE-TEM and FT-IR. The rheological properties of VTEScoated ZrO2/High-temp composite solution with different particle ratios are investigated by rheometer, and the dispersion properties of the composite solution are confirmed by relaxation NMR and Turbiscan. The mechanical properties of 3Dprinted objects are measured by a tensile test and nanoindenter. To investigate the aggregation and dispersion properties of VTES-coated ZrO2 ceramic particles with different particle ratios, we observe the cross-sectional images of 3D printed objects using FE-SEM. The 3D printed objects of the composite solution with nano-particles of 80 % demonstrate improved mechanical characteristics.