Interpenetrating double network silicone hybrid aerogels with excellent mechanical properties and thermal stability for high-temperature insulation†

Silica aerogels, promising for high-performance insulation, face challenges in concurrently optimizing mechanical strength and thermal stability. While constructing interpenetrating double networks is a promising strategy, existing methods often suffer from poor chemical integration between the organic and inorganic phases, leading to compromised thermal stability and complex synthesis routes. Herein, we overcome this challenge by developing a robust and thermally stable silicone hybrid aerogel with interpenetrating double network structure via a facile secondary sol–gel process. The key to this synthesis is the initial formation of a high-strength, ‘armor-like’ carbon-rich Si–O–Si skeleton via a temperature-controlled reaction, followed by the in situ growth of a secondary, silica-rich network that ensures excellent thermal stability. This unique approach ensures strong covalent Si–O–Si bonding between the two networks, creating a truly unified architecture that solves the typical issue of phase incompatibility. The resultant aerogels possess low thermal conductivity of 0.051 W m⁻¹ K⁻¹, excellent thermal stability with over 60% residual mass retained in both air and nitrogen, and exceptional compressive strength up to 15.0 ± 0.8 MPa. Furthermore, aerogel composites reinforced with low-density quartz fiber mats exhibit enhanced mechanical strength, achieving tensile strengths of up to 48.4 ± 2.5 MPa, while maintaining extremely low thermal conductivity at room and high temperatures. After heating with a quartz lamp for 600 seconds at 1000 °C, the composite exhibits excellent high-temperature thermal insulation properties and structural stability, evidenced by a final backside temperature of 418 °C. Additionally, it also exhibits superior ablation-resistance with a linear ablation rate of 0.001 mm s⁻¹ at 1000 °C oxy-propane flow for 100 s. These findings are expected to substantially promote the application of silicone aerogels in demanding environments that require high-temperature thermal insulation.