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

Abstract

In this work, we report the synthesis of silicon aerogel elastomers (SAEs) by one-pot hydrolytic condensation of silanes, followed by drying at room temperature. The as-synthesized SAE features excellent flexibility and mechanical robustness, for example, a high compressive strength of up to 40 kPa at 75% strain was achieved. Combined with their thermal insulation properties (a low thermal conductivity of ca. 0.02 W m -1 K -1 in air), for the first time, such SAEs were used as a porous platform for both flame-retardant measurement and solar steam generation. By coating with Mg(OH)2 via a facile coprecipitation method, the treated SAEs show excellent flame retardancy with a peak heat release rate of 25.61 kW m-2, in addition to high fire resistance and excellent smoke suppression. When used as a solar steam generator, their evaporation efficiency was measured to be 82.7% (1 kW m-2), which could compete with that of other high-performance bilayered photothermal materials reported so far. Taking advantage of their simple and cost-efficient manufacture and superior mechanical robustness and flexibility, such SAEs with multifunctionalities may have great potential for a wide variety of energy-saving applications, for example, especially for thermal insulation coatings with better flame retardancy and efficient solar steam generation for desalination or freshwater production.