•Nanometer titanium dioxide (TiO2) was deposited on hollow fly ash beads.•Hollow fly ash beads were modified by Ca(OH)2 saturated solution.•The surface modification favored the formation of a smooth and uniform TiO2 coating.•The NIR solar reflectance of the composite pigment is as high as 0.68.Nanometer titanium dioxide was deposited on hollow fly ash beads using a chemical liquid deposition method. Surface modification of hollow fly ash beads with Ca(OH)2 saturated solution resulted in the presence of calcium silicate hydrate. The surface modification had a great influence on the growth and micro-morphology of TiO2 nanoparticles on the surfaces of hollow beads. Electrostatic repulsive forces between the modified hollow bead surfaces and hydrated TiO2 were significantly reduced after the surface modification, favoring the formation of a homogeneous and uniform TiO2 film with high TiO2 loading. A possible growth mechanism of TiO2 coatings was proposed. Moreover, the near-infrared solar reflectance of hollow bead/TiO2 composite pigment reached 0.68, which was approximately 1.8 times as high as that of hollow beads. An approximately 28.1 °C decrease in temperature was obtained for the inner surface of a calcium silicate board coated with composite pigments. Therefore, hollow fly ash bead/TiO2 composite pigments are excellent candidates for near-infrared reflective pigments used in solar reflective coatings.

•The mica/Fe2TiO5 composite pigments exhibit brilliant yellow colors.•Different sized Fe2TiO5 nanorods were coated on the surface of mica particles.•The NIR solar reflectance of the composites was as high as 80.3%.•The composite pigments exhibit strong UV shielding property.To obtain cool yellow pigments with high near-infrared reflectance, mica/Fe2TiO5 composite pigments were synthesized by a chemical liquid deposition method. The developed composite pigment powders were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–vis–NIR diffuse reflectance spectra, and CIEL*a*b* color scales. Different sized Fe2TiO5 nanorods were coated on the surface of mica particles. The particle size of the nanorods increased with increasing molar ratio of Fe3+ to Ti4+. The obtained composite pigments showed strong ultraviolet shielding ability and high near-infrared reflectance property. What's more, the Fe2TiO5 coating with smaller particle size possessed higher reflectance in the region of 700–1500 nm in accordance with the Kubelka-Munk theory. The near-infrared solar reflectance of mica/Fe2TiO5 composites was as high as 80.3%. An approximately 3 °C decrease in interior temperature was obtained for the heat box coated with the composite pigments. Furthermore, the composite pigments exhibit brilliant yellow colors. Therefore, mica/Fe2TiO5 composites are excellent near infrared reflective yellow pigments for efficient solar reflective coatings.

Rutile TiO2-coated mica–titania pigments were prepared by hydrolysis of TiCl4 ethanolic solution in water at 70 °C. MnO2 as a rutile promoting additive was deposited onto mica prior to TiO2. X-ray diffraction and Raman spectra analysis verified that use of only 2.07 wt% MnO2 with respect to mica weight began to provide a complete rutile TiO2 coating without calcination. The rutile promoting effects of MnO2 could be ascribed to the structural similarity of rutile and pyrolusite. Scanning electron microscopy analysis showed that MnO2 also had a pronounced effect on the morphology of TiO2 coatings. The prior deposition of MnO2 onto mica lead to the formation of rutile TiO2 films composed of highly oriented fine needles on the mica surface and nanoflower structures on the needle structures. The as-obtained rutile-TiO2 coated mica–titanium pigments are shown to exhibit a high photostability under UV illumination.Graphical abstractHighlights► Rutile TiO2-coated mica–titania pigments were prepared at 70 °C. ► MnO2 as a rutile promoting additive was deposited onto mica prior to TiO2. ► Rutile TiO2 films were composed of fine needles and nanoflower structures. ► Rutile-TiO2 coated mica–titanium pigments exhibit a high photostability.

Rutile TiO2-coated mica–titania pigments were prepared by hydrolysis of titanium tetrachloride in the presence of Fe3+. After calcination at 700 °C for 2 h, TiO2 nanolayers in rutile phase were formed on the mica surfaces. The morphology and the anatase–rutile transformation were probed by scanning electronic microscopy (SEM) and X-ray diffraction (XRD) respectively. SEM micrographs show that the dopants enhance the growth of particles of TiO2 thin layers. The change of lattice parameters confirms that Fe3+ enter anatase structure and affect the anatase–rutile transformation. For the iron loading regime studied here, the anatase–rutile transformation is inhibited at low dopant levels with respect to undoped titania. While the anatase–rutile transformation is promoted as iron loading is increased. Moreover, synthesized pH value also has a pronounced effect on the anatase–rutile transformation and a highly acidic environment favors the formation of rutile.Highlights► Rutile TiO2-coated mica–titania pigments were prepared by Fe3+ doping. ► The anatase–rutile transformation is inhibited at low dopant levels. ► The inhibition becomes less pronounced as iron loading is increased. ► A highly acidic environment favors the formation of rutile.