Abstract:

Silica/zirconia（SiO₂/ZrO₂）core-shell composite microspheres were synthesized by depositing ZrO₂ on silica microspheres through the hydrolysis of zirconium precursor. The composites were characterized by scanning electronic microscope（SEM），energy dispersive spectroscope（EDX）and X-ray diffraction（XRD）. The infrared emissivity values of the particles in 8—14 μm wave band were measured by IR-1 infrared radiometer. Experimental results indicated that the composites represent obvious core-shell structure，and the zirconia content on the surface of silica particles is increased with the increase in deposition cycles. The ZrO₂ layer could form monoclinic and tetragonal crystals after thermal treatment. The SiO₂/ZrO₂ composite particles showed lower infrared emissivity value than pure SiO₂. In addition，the infrared emissivity properties of the composites were affected by the crystalline form of ZrO₂. ZrO₂ coating with monoclinic crystalline structure showed lower infrared emissivity value than that with tetragonal crystalline structure. The remarkable decrease in infrared emissivity value of the composites was attributed to the interfacial interactions between the ZrO₂ layer and the SiO₂ spheres.