Synthesis and comparative analysis of silica aerogel and single/double-shell hollow microspheres for silicone coatings: thermal stability/insulation and mechanical property

Three silica-based porous materials-silica aerogel (SA), hollow silica microspheres (HS), and double-shell silica-titanium hollow microspheres (HST)-were synthesized via sol-gel and templating methods, and integrated into silicone resin to develop thermal insulation coatings. All three thermal insulation materials demonstrate excellent thermal insulation properties, with reflectance greater than 92 % in the near-infrared wavelength range. The composite coatings exhibit low thermal conductivity and high thermal stability. SA possesses the lowest thermal conductivity (0.0297 W/m·K). However, adding 5 wt% SA results in a reduction of mechanical properties, it's difficult to prepare coatings when exceeding 5 wt% due to excessive coating viscosity. Due to the double-shell structure and higher reflectance, HST exhibits superior thermal insulation performance than HS. When added 8 wt% HST, composite coating SHST4 demonstrates excellent thermal insulation performance (0.129 W/m·K) while maintaining exceptional mechanical properties. This work provides an effective strategy to design high-performance thermal insulation coatings for many fields.