Tamplate Synthesis And Characterization Of Low Thermal Conductivity Hollow Microspheres With Multi-Layer Structure

Inorganic hollow microspheres with its unique hollow structure, can significantly improve the thermal insulation property of the material, which can help alleviate the increasingly serious energy crisis. The hollow structure can change the heat conduction into the convective heat transfer, while increasing the gas-solid interface and extended heat transfer passages. In this paper,we synthesized the SiO2、SiO2/TiO2、TiO2 and TiO2/SiO2 hollow microspheres with low thermal conductivity by template method, then characterized the synthetic products.The results indicated that the SiO2 hollow microspheres, synthesized using hydrolysis-condensation reaction of TEOS, had spherical diameter of 468 nm, shell thickness of about 60 nm and specific surface area of 68.742m2/g. The powder’s reflectance remained at around 95% in 400~1100nm wavelength, the lowest solar absorptance of 0.081, and the thermal conductivity of 0.0384W/(m·K). The TiO2 hollow microspheres, synthesized by 220 nm PS spheres template have spherical diameter of 210 nm, the lowest solar absorptance of 0.095, the thermal conductivity of 0.0727W/(m·K).We synthesized the SiO2/TiO2 and TiO2/SiO2 double-layer hollow microspheres under 50℃,using the 2000 nm PS as template. The SiO2/TiO2 double-layer hollow microspheres had spherical diameter of 2000~2380nm, shell thickness of about 30 nm, the biggest specific surface area of 141.08m2/g and pore diameter of 3.8nm. The reflectance in the near infrared increased compared to SiO2, and it’s lowest solar absorptance is 0.102, while thermal conductivity is 0.0532W/(m·K). The TiO2/SiO2 double-layer hollow microspheres synthesized in this research had spherical diameter of 2400~2500nm, shell thickness of about 35 nm, the biggest specific surface area of 88.450m2/g, pore diameter of 3.75 nm and the lowest solar absorptance of 0.094, while thermal conductivity is 0.0578W/(m·K).