Sodium Silicate-Based Aerogels by Ambient Pressure Drying

Silica aerogels are the most commercially relevant aerogel materials. By volume, supercritically dried blanket composites are still leading global sales by a substantial amount; however, particle-based aerogels such as granulate and powder are cost-competitive alternatives. This chapter summarizes the last three decades of research and industrial process development in the field of “low-cost,” sodium silicate-based aerogel preparation by means of ambient pressure drying, illustrating key developments and milestones in both academic research and process engineering fields. Key process steps such as gelation, aging, hydrophobization, and APD drying are analyzed in detail in the context of feasibility, simplicity, product quality, and scalability. The chapter finishes with a brief discussion of key process parameters and their effect on the physical properties of the obtained aerogel materials as well as a current snapshot of the most promising applications for particle-based aerogels.