|학술대회||2006년 가을 (11/03 ~ 11/03, 수원대학교)|
|발표분야||제11회 신소재 심포지엄|
|제목||Synthesis of Ultra Low-density Nanoporous Silica Aerogel Monolith by Ambient Drying|
|초록||Aerogels are highly porous materials where the pore sizes are less than a few tens nanometers in diameter. This gives a material with the highest surface area per unit weight, a high porosity (80~99.8 %), a low density (~0.003 g/cm3), a high thermal insulation value (0.005 W/m•K), an ultra low dielectric constant (k’=1.0~2.0) and a low index of refraction (~1.05). Because of these unique properties, the silica aerogel has been extensively studied, not only for use as transparent thermal insulators but also as inter-metal dielectric materials (IMDs), optical and acoustic applications, and the space industry.
The usual production of silica aerogels includes supercritical drying and raw materials like tetraethoxysilane which prohibit a commercialization. To avoid the high costs we produced water glass based aerogel by ambient pressure drying method. This requires at least one solvent exchange from water for the surface modification. In our previous study, we have successfully fabricated a crack-free silica aerogel monolith (20 mm in diameter and 10 mm in thickness) by ambient drying method using solvents with low surface tension like hexane or xylene and TMCS/hexane mixture as a surface modification agent. The obtained aerogel monolith was sufficiently porous and had hydrophobic surfaces. However, the reproducibility of the aerogel production was dramatically reduced with increasing the diameter of the aerogel monolith.
In this study we have concentrated with improving reproducibility of water glass-based silica aerogel monolith production. The water glass-based wet gel was aged in water or TEOS/ethanol solution before exchanging the pore liquid (water) for solvent with low surface tension. Effects of the aging conditions on microstructure and density of the aerogel were investigated. Aged aerogels show a higher density and lower transmittance than non-aged aerogels, however, it is expected that the large particle size and hence pore size of the aged aerogel reduces the capillary pressure during ambient drying.
|저자||Hae Jin Hwang1, Chul Eui Kim2, Yong Chul Cha3, Ji-Woong Moon1, Sub Han2, Sang-Kuk Woo3|
|소속||1School of Materials Science and Engineering, 2Inha Univ., 3Korea|
|키워드||sol-gel; hydrophobic silica aerogel; nano structure; ambient drying; water glass|