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Synthesis of hollow TiO2@SiO2 spheres via a recycling template method for solar heat protection coating

Li Li,Xinhong Chen,Xia Xiong,Xiaoping Wu,Zinan Xie,Zuohua Liu

The development of a simple and environmentally friendly method to synthesize hollow TiO 2 structures is urgent for realizing high NIR reflectance and low thermal conductivity . Hollow TiO 2 @SiO 2 structures have been successfully synthesized by a recycling template method. The synthesis process involves four steps as follows: 1) preparation of SiO 2 spheres, 2) synthesis of SiO 2 @TiO 2 core-shell structure by coating mesoporous TiO 2 shell on SiO 2 and crystallization by calcination , 3) etching the SiO 2 @TiO 2 to form the hollow TiO 2 spheres, and 4) coating the hollow TiO 2 spheres with a SiO 2 protection layer to produce hollow TiO 2 @SiO 2 structures. The SiO 2 serves as a template to support and synthesize hollow TiO 2 shell, and then after being etched, to form a Na 2 SiO 3 solution as a coating agent to protect TiO 2 shell from photocatalytic activity. The as-synthesized hollow TiO 2 @SiO 2 structures not only have high NIR reflectance, but also have a high thermal barrier performance due to the hollow structure. Moreover, the NIR reflectance of the coating made from hollow TiO 2 @SiO 2 reached 94.9%, and the temperature of the inner surface of the coating board is reduced about 16 °C, compared with the surface without coating. The weather resistance studies reveal that the hollow TiO 2 @SiO 2 sample is very stable under the UV irradiation. In particular, the hollow TiO 2 @SiO 2 structures synthesized by using this method shows multifunctional responses towards solar heat.