Porous SiO₂ Hollow Spheres as a Solar Reflective Pigment for Coatings

Abstract

This study starts with the synthesis of silica hollow spheres (HSs) by utilizing in situ synthesized polystyrene (PS) microspheres as the template for the deposition of a silica (SiO) shell, followed by a slow gasification step in air to remove the PS core. The size of HS and the thickness of the porous SiO shell are tuned by varying the synthesis conditions of the PS latex and those of the sol-gel deposition, respectively. Various HS powder samples are characterized by ultraviolet-visible-near infrared (UV-vis-NIR) spectroscopy to determine their diffuse reflectance. Furthermore, they are used as the filler in an acrylic polymer matrix for the measurement of solar reflectivity on a solar spectrum reflectometer. It turns out that both cavity size and the structure of the SiO shell are influential in the reflection of NIR and UV-vis light, respectively. In addition, this study examines the effect on solar reflectivity of a selected metal oxide with a SiO HS. In conclusion, the cavity size of the HS has a strong impact on the reflectivity to NIR light whereas the shell itself affects the reflection of UV-blue light.

Uniform Fabrication of Hollow Titania Using Anionic Modified Acrylated Polymer Template for Phase Composition Effect as Photocatalyst and Infrared Reflective Coating

“…However, because the reflectance of the hollow titania particle was measured higher, it is an result of the hollow structure. Zxing et al [45] studied the effect of hollow silica particles on reflectance with different particle sizes, surface areas, and shell structures. An investigation on the effect of the hollow cavity size on solar reflectivity confirms that an increase in the HS size favors more reflection of longer λ light.…”

Recent progress in the preparation, properties and applications of superhydrophobic nano-based coatings and surfaces: A review

“…Today, the nano-based coatings not only serve as protection layers against mechanical aggressors or decorative purposes, but also act as smart materials that are multifunctional. According to the literature, smart coatings can be applied for anti-corrosion, 1, 2 anti-wearing, 3 anti-bacterial, [4][5][6][7] anti-fungal, 8,9 self-cleaning, 10,11 superhydrophobic, 12,13 solar reflective, 14,15 photocatalytic, [16][17][18][19] and radar absorbing 20 and electrically conducting polymeric 21 applications. For example, lotus leaf 22 with naturally attained superhydrophobic and self-cleaning effects has garnered great interest among the researchers due to its potential biomimicking in coatings for self-cleaning, 23 anti-icing, 12,24 anti-fog, 12,25,26 anti-wetting, 27 and anti-fouling.…”

Silicon‐Based Photonic Architectures from Hierarchically Porous Carbon Opals

“…13,14 Hollow spheres have also been proposed in the last years in the photonic field for applications such as colloidal lithography, 15 whispering gallery mode resonators, 16 and coating materials for tuning surface reflectivity. 17 Research on colloidal spherical particles has mainly focused on silica, polystyrene or polymethylmethacrylate as building blocks, due to their straightforward fabrication, large availability and good control of their physicochemical properties. 12 However, the increasing polydispersity of silica spherical particles larger than about 0.5 μm and the lack of thermal, mechanical stability or solvent compatibility of polymeric particles have boosted the exploration of colloidal systems based on different materials.…”