Mechanically Robust and Flame-Retardant Silicon Aerogel\nElastomers for Thermal Insulation and Efficient Solar Steam Generation

Abstract

In this work, we report the synthesis\nof silicon aerogel elastomers\n(SAEs) by one-pot hydrolytic condensation of silanes, followed by\ndrying at room temperature. The as-synthesized SAE features excellent\nflexibility and mechanical robustness, for example, a high compressive\nstrength of up to 40 kPa at 75% strain was achieved. Combined with\ntheir thermal insulation properties (a low thermal conductivity of <i>ca</i>. 0.02 W m ^–1 K ^–1 in air), for the first time, such SAEs were used as a porous platform\nfor both flame-retardant measurement and solar steam generation. By\ncoating with Mg­(OH)₂ via a facile coprecipitation method,\nthe treated SAEs show excellent flame retardancy with a peak heat\nrelease rate of 25.61 kW m^–2, in addition to high\nfire resistance and excellent smoke suppression. When used as a solar\nsteam generator, their evaporation efficiency was measured to be 82.7%\n(1 kW m^–2), which could compete with that of other\nhigh-performance bilayered photothermal materials reported so far.\nTaking advantage of their simple and cost-efficient manufacture and\nsuperior mechanical robustness and flexibility, such SAEs with multifunctionalities\nmay have great potential for a wide variety of energy-saving applications,\nfor example, especially for thermal insulation coatings with better\nflame retardancy and efficient solar steam generation for desalination\nor freshwater production.