Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1504145 | Solid State Sciences | 2015 | 8 Pages |
•Silica aerogel balls were prepared using different MTES/TEOS molar ratio.•Aerogels at I of 0.8 and 1.0 had maximum contact angle (152°).•Aerogel at I of 0.8 had lowest density (0.103 g cm−3).•Silica aerogels transform hydrophobic to hydrophilic at around 450 °C.•The surface chemical modification of aerogels were tested by FT-IR.
In the present paper, silica aerogel balls were prepared using methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) co-precursor with different MTES/TEOS molar ratio (I) by two-step acid-base catalyzed sol–gel process and molding technology followed by the carbon dioxide supercritical drying. The physical properties of various silica aerogels whose I varied from 0 to 1.0 were studied by BET and SEM. Approving aerogel ball was obtained by using acetone as exchanging solvent at I of 0.8. Better properties are less crack, little shrinking percentage (17%), low apparent density (0.103 g/cm3), large surface area (996.35 m2/g) and high pore volume (3.32 cm3/g). Characterized by contact angle measurements and thermal stability, the characterizations of aerogel spheres were strongly affected by the MTES/TEOS molar ratio. Hydrophobic property increased with the increase in I value, and silica aerogels at I = 0.8 and 1.0 have a superhydrophobic characterization with the highest contact angle (152°). The TG-DTA analysis shows that the silica aerogel spheres transform hydrophobic to hydrophilic at around 450 °C, which is due to oxidation of Si–CH3 to Si–OH groups. The surface chemical modification was confirmed by FT-IR spectrums, which demonstrated that Si–CH3 groups be beneficial to molding of silica aerogels.
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