Superhydrophobic hybrid aerogel powders from waterglass with distinctive applications

• We prepare superhydrophobic hybrid aerogel powders by a fast process at atmospheric conditions.
• The co-precursors are waterglass and the minimum amount of hexamethyldisilazane to lower the cost.
• The process conditions are tuned in order to optimize the total yield (∼80%).
• High lipophilic/hydrophilic ratios are achieved, with tapping densities as low as 0.120 g cm−3.
• Distinctive applications are proposed, such as water transport at a microscale level.

Hybrid silica aerogel powders with enhanced superhydrophobicity and very high reaction yield were prepared by a fast co-precursor method at ambient pressure. An inexpensive aqueous sodium silicate solution was used as starting material (waterglass or WG), with hexamethyldisilazane (HMDZ) as organic co-precursor.The key for successfully achieving such high yields and superhydrophobicity was a systematic tuning of the synthesis parameters (co-precursors and acid catalyst molar ratios) and process conditions (stirring speed, stirring period, aging, washing and drying steps), in close correlation with the reaction mechanism. Using a minimum amount of organic co-precursor, a total yield of ∼80% in hybrid aerogels with high lipophilic/hydrophilic ratio, very high water contact angles (∼152 ± 2°) and very low densities (∼0.120 g cm−3) were obtained. The optimized synthesis conditions consist in HNO3:WG:HMDZ molar ratios of 1.5:1.0:1.5, stirring speed of 120 rpm, only during addition of the catalyst and co-precursor, aging for 5 min and washing with water before drying at atmospheric pressure.The minimization of the only costly precursor allows envisaging a low-cost large scale production and, moreover, the encapsulation of water droplets within aerogel powder allows proposing distinctive applications, such as water transport at a microscale level.

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