title: Porous SiO2Hollow 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 (SiO2) shell, followed by a slow gasification step in air to remove the PS core. The size of HS and the thickness of the porous SiO2shell 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 SiO2shell 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 SiO2HS. 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.
authors.affiliation: Department of Chemical & Biomolecular Engineering, National University of Singapore , 10 Kent Ridge Crescent, 119260 Singapore.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Xing
authors.affiliation: Institute of Materials Research and Engineering, Agency for Science, Technology and Research, A*STAR , 3 Research Link, 117602 Singapore.
authors.forename: Siok-Wei
authors.initials: SW
authors.lastname: Tay
authors.affiliation: Department of Chemical & Biomolecular Engineering, National University of Singapore , 10 Kent Ridge Crescent, 119260 Singapore.
authors.forename: Yeap Hung
authors.initials: YH
authors.lastname: Ng
authors.affiliation: Department of Chemical & Biomolecular Engineering, National University of Singapore , 10 Kent Ridge Crescent, 119260 Singapore.
authors.forename: Liang
authors.identifier: http://orcid.org/0000-0001-8955-6694
authors.initials: L
authors.lastname: Hong
keywords: cavity effect; coating; nanoshell; silica hollow spheres; solar light reflectivity