gas analysis

　　aerogel, English aerogel also known as dry gel. When the gel removes most of the solvent, the liquid content of the gel is much less than the solid content, or the medium filled in the spatial network structure of the gel is a gas, and the appearance is solid, which is a dry gel, also known as aerogel。

　　Aerogel can be divided into single component aerogel according to its composition, such as SiO2, Al2O3, TiO2, carbon aerogel (organic aerogel obtained after carbonization), etc. Multi-component aerogel, such as SiO2/Al2O3, SiO2/TiO2, etc. The most typical and most studied aerogels are single-component SiO2 aerogels and carbon aerogels (organic aerogels).。

　　At present, the preparation methods of SiO2 aerogel mainly include supercritical drying and atmospheric pressure drying。

　　1、supercritical drying

　　SiO2 aerogel prepared by supercritical method has excellent performance, complex and expensive equipment, and high energy consumption in drying process. With the improvement of the manufacturing level of domestic equipment in recent years, the cost of preparing aerogel by supercritical method is gradually reduced, and the reliability of equipment is greatly improved, which greatly increases the practicability of this method。

　　2、ambient drying method

　　The preparation of SiO2 aerogels by atmospheric drying does not require a large amount of equipment, and has strong operability, safety and environmental protection, which provides the possibility for large-scale industrial production of SiO2 aerogels. However, the current reported atmospheric pressure preparation process is complicated. Taking water glass as the precursor for example, it involves ion replacement, sol-gel process, surface hydrophobic modification, multi-gradient solvent replacement, drying and other processes in sequence. The production and preparation cycle is time-consuming, and a large amount of solvents are consumed in production, and a variety of solvents are mixed, so recovery and separation are difficult, increasing the cost of the product. Therefore, the industrial large-scale preparation and wide application of aerogel are limited。