Synthesis, characterization and infrared emissivity study of SiO2/Ag/TiO2 “sandwich” core-shell composites

Abstract

SiO2/Ag/TiO2 “sandwich” core-shell composites were successfully synthesized by combing three individual synthesis steps with calcination. The as-obtained composite was composed of a SiO2 core with an average diameter of ~500nm, full-covered Ag shell with the face-centered cubic (fcc) structure on the surface of SiO2 sphere, and an outer thin layer of TiO2 with variable crystal phases from amorphous to anatase. The effects of the composition and crystal form on infrared radiation properties were investigated. The results revealed that the infrared emissivity value of the SiO2/Ag core-shell composites was remarkably decreased after the deposition of Ag shell on the surface of SiO2 core. Moreover, the SiO2/Ag/TiO2 core-shell composites with anatase TiO2 coating owned the lower infrared emissivity value than that with amorphous TiO2. Such “sandwich” core-shell structures had a relatively low infrared emissivity value, with the lowest value down to 0.557.