Comparative studies on the surface chemical modification of silica aerogels based on various organosilane compounds of the type RnSiX4−n
| Autor: | Gerard Pajonk, A. Venkateswara Rao, Philippe Barboux, Sharad D. Bhagat |
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| Rok vydání: | 2004 |
| Předmět: |
chemistry.chemical_classification
Materials science Methyltrimethoxysilane Silica gel Aryl Aerogel Condensed Matter Physics Electronic Optical and Magnetic Materials Contact angle chemistry.chemical_compound chemistry Chemical engineering Materials Chemistry Ceramics and Composites Alkoxy group Organic chemistry Laplace pressure Inorganic compound |
| Zdroj: | Journal of Non-Crystalline Solids. 350:216-223 |
| ISSN: | 0022-3093 |
| DOI: | 10.1016/j.jnoncrysol.2004.06.034 |
| Popis: | We report the experimental results dealing with the surface chemical modification of silica aerogels using various precursors and co-precursors based on mono-, di-, tri- and tetrafunctional organosilane compounds of the type RnSiX4−n (where R = alkyl or aryl groups, X = Cl or alkoxy groups, n = 0–4). The precursors exhibit either tetrafunctional or trifunctional chemical functions while the co-precursors have a number of functional groups varying from 1 to 3. The organosilane based on the methyltrimethoxysilane (MTMS) can be used as a precursor as well as co-precursor. The chemically modified aerogels have been produced by (i) co-precursor, and (ii) derivatization methods. The co-precursor method results in aerogels with higher contact angle (θ ≈ 136°) but the aerogels are opaque, whereas transparent (>80% optical transmission in the visible range) aerogels with lower contact angle (θ ≈ 120°) are obtained using the derivatization method. The hydrophobicity of the phenyl-modified aerogels has been found to be thermally stable up to a temperature of 520 °C. Using the MTMS precursor, aerogels with contact angles as high as 175° have been obtained, but the aerogels are opaque. The aerogels obtained using TEOS precursor along with the trimethylethoxysilane (TMES) co-precursor, show negligible volume shrinkage. Water intrusion into the MTMS-modified aerogels at pressures greater than the Laplace pressure exhibits hysteresis, as shown in the pressure-volume curves. Water droplets placed on surfaces coated with superhydrophobic aerogel powder with 8° of inclination showed velocities as high as 0.4 ms−1. The results are discussed with respect to the ratios of organic and inorganic components of the organosilane compounds. |
| Databáze: | OpenAIRE |
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