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601405 
Journal Article 
Superhydrophobic silica aerogel powders with simultaneous surface modification, solvent exchange and sodium ion removal from hydrogels 
Bhagat, SD; Kim, YH; Suh, KH; Ahn, YS; Yeo, JG; Han, JH 
2008 
1 
Microporous and Mesoporous Materials
ISSN: 1387-1811 
ELSEVIER 
AMSTERDAM 
112 
1-3 
504-509 
English 
WOS:000256713300056 
Abstract: We report a novel method for the rapid synthesis of superhydrophobic silica aerogel powders based on an inexpensive precursor such as sodium silicate via ambient pressure drying. The sodium silicate was directly polymerized without prior ion exchange by the addition of nitric acid and hexamethyldisilazane (HMDS) to yield silylated hydrogels. The indispensable steps such as surface modification, solvent exchange and sodium ion removal were simultaneously accomplished in one-step by immersing the silylated hydrogel in a non-polar solvent such as n-hexane. The organic modification in the aqueous phase, i.e. in the hydrogel essentially led to the displacement of pore water and simultaneous intrusion of n-hexane transformed the hydrogel into an organo-gel. During this process, sodium ions present in the hydrogel were removed with the displaced pore water. Using this process, it was possible to produce superhydrophobic silica aerogel powders with contact angle as high as 150°, very low tapping density of 0.08g/cm3, high specific surface area (778m2/g) and cumulative pore volume of 2.34cm3/g. The total processing time of the aerogel powders could be restricted to 5h. The textural properties of the aerogel powders have been investigated and discussed. [Copyright 2008 Elsevier] Copyright of Microporous & Mesoporous Materials is the property of Elsevier Science Publishing Company, Inc. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts) 
COLLOIDS; AMORPHOUS substances; CHEMISTRY, Physical & theoretical; DIFFUSION