Synthesis of window glazing coated with silica aerogel films via ambient drying

An ambient drying process (1 atm, 270 degreesC) has been developed in order to synthesize window glazing coated with silica aerogel films. The aerogel film could be manufactured by this process of wet gel films obtained via a dip-/spin-coating of the silica sol on a glass slide. Before drying, the isoproponol solvent in wet gels was exchanged with n-heptane to minimize the drying shrinkage. The thickness. refractive index, and porosity of silica films were 0.16-10 mum, 1.08-1.09, and 80-84%, respectively. The transmittance of window glazing was over 90% and we could predict that the optimal thermal conductivity (0.2 W/(m K)) of the window glazing would be obtained at the aerogel thickness of 100 mum (0.016 W/(mK)). (C) 2003 Elsevier Science B.V. All rights reserved.