Abstract
Nanostructured Fe2O3/TiO2 composite pigments with improved NIR reflectance were prepared by a homogeneous precipitation method using urea and NH4OH. The optical and morphological properties of the resulting pigment were investigated by varying the weight ratio of Fe2O3 to TiO2 and the calcination temperature. The resulting composite pigment has a nanostructure in which Fe2O3 nanoparticles of 20-30 nm size are well coated on the surface of TiO2 (∼100 nm) and the reflectance is greatly improved in the wavelength range of 620-1350 nm. The ratio of Fe2O3 to TiO2 and the calcination temperature were optimized to provide both high NIR reflectance and red color, which were 0.1 and 700 °C. As a result, compared with pure Fe2O3 (E g = 2.06 eV, a* = 22.6), the optimized Fe2O3/TiO2 composite pigment (E g = 2.09 eV, a* = 24.8) showed similar color properties and improved NIR reflectance by about 23.8%. In addition, the Fe2O3/TiO2 composite pigment showed about 62.7% larger reflectance at 905 nm than Fe2O3. According to a temperature rise test under IR illumination, the Fe2O3/TiO2 composite pigment was confirmed to have improved heat shielding properties. Therefore, the nanostructured Fe2O3/TiO2 powder could be potentially applied as a LiDAR detectable cool red pigment for autonomous vehicles.