Aerogel is a new type of inorganic functional material with a three-dimensional nanoporous network structure, known as the lightest solid material and super thermal insulation material in the industry. Its framework is formed by interconnection of silica nanoparticles to build a continuous network, filled with a large number of nano-scale open pores. The porosity reaches 90%～99%, and the specific surface area is as high as 600–1200㎡/g. Its unique micro structure breaks through the performance limit of traditional thermal insulation materials and becomes an irreplaceable key raw material in thermal insulation, adsorption, catalysis and precision electronics fields.
The mainstream preparation of aerogel follows two core processes: sol-gel reaction and drying shaping. Firstly, silicon source materials undergo hydrolysis and polycondensation to form silica sol, which gradually crosslinks into a three-dimensional wet gel framework. Then solvent replacement is adopted to replace the water in pores and avoid pore collapse during drying. Finally, supercritical drying or atmospheric drying is used for shaping. Supercritical drying eliminates gas-liquid interfacial tension under high temperature and pressure, completely retaining the original nanopore structure with optimal performance, yet it requires large equipment investment and high production cost. Atmospheric drying simplifies the process through surface hydrophobic modification and gradient temperature drying with lower energy consumption, suitable for large-scale industrial mass production and has become the mainstream route for civil and industrial fields.
Benefiting from the special porous structure, aerogel possesses outstanding comprehensive properties. Its thermal conductivity is as low as 0.012～0.023W/(m·K), much better than traditional thermal insulation materials such as rock wool, glass wool and polyurethane. Under the same thermal insulation effect, its thickness is only one-third of traditional materials or even thinner. Its ultra-low density realizes lightweight application and greatly reduces structural load. After hydrophobic modification, it shows excellent water repellency with extremely low water absorption, maintaining stable thermal insulation performance for a long time in high humidity, open-air and underground humid conditions. Meanwhile, it features Class A non-combustibility, wide temperature resistance, aging resistance and low dielectric property, working stably from -196℃ to 650℃, suitable for cold chain, high-temperature pipelines, aerospace and other extreme working conditions.
Current technological upgrading focuses on green production, cost reduction and controllable structure. By optimizing catalyst system, recycling organic solvents and improving hydrophobic modification formula, VOC emission and energy consumption are effectively reduced. Precise regulation of pore size distribution and framework particle size improves mechanical strength and anti-pulverization performance, solving the brittleness and fragility of traditional aerogel. With the maturity of atmospheric drying technology, aerogel is rapidly transforming from high-end military special materials to large-scale popularization, providing strong support for carbon reduction and high-end material upgrading.