Silica aerogel obtained from MS51 transparent with slightly blue coloration as shown in Fig. 6. Density and thermal conductivity of the silica aerogel obtained from MS51 were 0.16 g/ cm3 and 0.016 W/Km, respectively. And density and thermal conductivity of TMOS were 0.18 g/ cm3 and 0.018 W/Km, respectively. The shrinkage ratio

W ave length (nm)

Fig. 5 UV-VIS spectrum of selectively solar-absorbing coatings.

of silica aerogels obtained from MS 51 and TMOS, after supercritical drying, was 4.1 and 1.4%, respectively.

Fig. 7 shows transmittance of the silica aerogels obtained from MS 51 and TMOS. Transmittance of both them was about 80 % at 550 nm. Silica aerogel has pores of several nm, visible light was not scattered in the silica aerogel. Therefore, the transparency of the silica aerogel is good and its thermal conductivity is lower than general insulation. Employing silica aerogel as a transparent insulator for the selectively solar-absorbing coatings may control.