Controlled TiO2 coating on hollow glass microspheres and their reflective thermal insulation properties

Abstract

Hollow glass microspheres (HGMs) have great potential in building energy-saving and industrial insulation. Anatase TiO2-modified HGMs were prepared by a sol‒gel method in acetic acid-ethanol solution. Scanning electron microscopy, X-ray diffraction, zeta-potential measurements, nitrogen-sorption measurements, and Fourier-transform infrared and ultraviolet-visible-near-infrared diffuse reflectance spectroscopies showed that the alkali modification of the HGMs greatly influenced the loading and microstructure of the TiO2 film. The TiO2 loading could be accurately controlled by ethanol addition and the TiO2 coating time. A mechanism for the TiO2 coating of the HGM surface is proposed. The synergistic action of hydrogen bonding and electrostatic forces resulted in close contact between the HGMs and TiO2 sol at pH 3.5. The effects of different TiO2 loading rates on the reflective and thermal insulation properties were studied. The near-infrared reflectance of 15.9% TiO2 coated on HGMs was 96.27%, and the inner surface temperature of the composite pigment coated on aluminum board was reduced by 22.4°C. The TiO2/HGM composite pigments exhibited excellent solar reflective and thermal insulation properties, so have potential in the construction of exterior walls and roofs.