Silika aerojellerin büyük ölçekli üretimi için sol-jel parametrelerinin, termal ve optik özelliklerinin incelenmesi

Transparency in thermal insulation systems provides new practical opportunities for insulation industry since transparent insulation materials can replace conventional window glazing. Silica aerogels are promising candidates to be used in such insulation systems because they are transparent and have very low thermal conductivity (10-15 mW/m.K). Silica alcogels are synthesized by sol-gel chemistry, gelled in a mold and dried by supercritical extraction with CO2 to get highly porous (porosity > 90%), low density (0.1-0.4 g/cm3) aerogels. The purpose of this study is to investigate the effects of synthesis parameters such as types and compositions of solvents on properties of silica aerogel to produce large scale silica aerogels with optimum thermal conductivity and transparency values and to use these large scale silica aerogels in a transparent vacuum insulation panel. Pore diameters, surface areas, and pore size distributions of the synthesized silica aerogels were measured with N2 adsorption-desorption technique. Optical properties were determined with using UV-VIS spectrophotometer. Transient Hot-Disk plane source and steady-state Guarded Hot Plate methods were used for analyses of thermal transport properties. It was found that decreasing the molar ratios of the solvents to precursor in the sol mixture increases transparency of resulting silica aerogel. Theoretical calculations on thermal conductivity showed that the lowest values can be reached when the density of the aerogel is between 100-200 kg/m3. Based on this information, a large scale (30x30x2.0 cm3) and transparent silica aerogel panel was produced with density of 180 kg/m3. Transparency ratio and thermal conductivity of the aerogel were measured as 88% (at 600 nm) and 16 mW/m.K, respectively.