| Abstract Scope |
Transparent silicon oxycarbide (SiOC) aerogels were produced from hybrid silica aerogels through pyrolysis in an Ar–H₂ atmosphere at 800°C and 1000°C. Structural, microstructural and thermal properties were investigated using N₂ physisorption, SEM, FTIR, XRD and LFA. The SiOC aerogels demonstrated excellent thermal stability up to 1000°C, maintaining high porosity of 72-88% at 800°C and 62-81% at 1000°C, as well as specific surface areas of 1120–1300 m²/g and 565–855 m²/g at 800 and 1000°C, respectively. Most notably, the aerogels pyrolyzed at 800°C exhibited ultralow thermal conductivity of 15–60 mW/m·K and high optical transparency, achieving up to 91% transmittance at 780 nm for 1 mm thick samples. These results confirm that the SiOC aerogels possess a unique combination of high porosity, thermal stability, ultra-low thermal conductivity, and optical transparency while exhibiting absorption (i.e., opacity) at 3 μm. This makes them promising candidates for advanced high-temperature thermal insulation applications, such as in solar towers. |