Superhydrophobic silica aerogels based on methyltrimethoxysilane precursor
Superhydrophobic silica aerogels based on methyltrimethoxysilane precursor
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DOI：
10.1016/j.jnoncrysol.2003.08.048
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发表时间：
2003-11-15
影响因子：
3.5
通讯作者：
Seth, T
中科院分区：
文献类型：
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作者：
Rao, AV;Kulkarni, MM;Seth, T
报道了使用甲基三甲氧基硅烷（MTMS）前驱体、甲醇（MeOH）溶剂和氢氧化铵（NH4OH）催化剂合成具有最高接触角（-173度）的超疏水二氧化硅气凝胶及其物理化学性质的实验结果。 NH4OH/MTMS (N)、H2O/MTMS (H)和MeOH/MTMS (M)的摩尔比分别为4.25 x 10(-2)至3.5 x 10(-1)、2至10和1.75至17。发现凝胶化时间随着N和H值的增加而缩短，并且随着M值的增加而增加。发现气凝胶的堆积密度随着 N、H 和 M 值的增加而降低。据观察，体积收缩率随着 N 和 H 值的降低而增加，并随着 M 值的增加而增加。在催化剂浓度变化的情况下，随着N值的增加，接触角(theta)从159稍微增加到167。另一方面，在 H2O 和 MeOH 变化的情况下，随着 H 和 M 值的增加，theta 首先从 162 和 160 增加到 173 和 167，然后分别减少到 160 和 159。所有 MTMS 气凝胶对可见光都是不透明的。气凝胶在高达 480 摄氏度的温度下仍能保持其疏水性。发现气凝胶的热导率约为 0.095 W/m K，除了具有较高堆积密度（>0.3 g/cm(3)，在较低的 H 值为 2 时）的气凝胶，其热导率约为 0.109 W/m K。通过傅里叶变换红外光谱（FTIR）、热重和差热分析（TGA-DTA）以及扫描电子显微镜（SEM）技术对气凝胶进行了表征。通过考虑水解和缩合反应以及 SEM 观察，对结果进行了讨论。 (C) 2003 Elsevier B.V. 保留所有权利。
The experimental results on the synthesis and physicochemical properties of superhydrophobic silica aerogels, with the highest ever obtained contact angle (-173degrees), using methyltrimethoxysilane (MTMS) precursor, methanol (MeOH) solvent and ammonium hydroxide (NH4OH) catalyst, are reported. The molar ratios of NH4OH/MTMS (N), H2O/ MTMS (H) and MeOH/MTMS (M) were varied from 4.25 x 10(-2) to 3.5 x 10(-1), 2 to 10 and 1.75 to 17, respectively. It has been found that the gelation time decreases with increase in N and H values and it increases with increase in M values. The bulk density of the aerogels was found to decrease with increase in N, H and M values. It has been observed that the volume shrinkage increases with decrease in N and H values and increases with M values. In the case of catalyst concentration variation, the contact angle (theta) increases slightly from 159 to 167 with increase in N values. On the other hand, in the case of H2O and MeOH variations, the theta first increases from 162 and 160 up to the values of 173 and 167 and then decreases to 160 and 159 with increase in H and M values, respectively. All the MTMS aerogels are opaque to the visible light. The aerogels retain their hydrophobicity up to a temperature of similar to480 degreesC. The thermal conductivity of the aerogels was found to be around 0.095 W/m K except for the aerogels with higher bulk density (>0.3 g/cm(3), at a lower H value of 2) whose thermal conductivity was around 0.109 W/m K. The aerogels have been characterized by Fourier transform infrared spectra (FTIR), thermogravimetric and differential thermal analyses (TGA-DTA) and scanning electron microscopy (SEM) techniques. The results have been discussed by taking into account the hydrolysis and condensation reactions and SEM observations. (C) 2003 Elsevier B.V. All rights reserved.