Aerogel is a kind of solid material with excellent thermal insulation performance. It has special microstructures such as high specific surface area, nanoscale pores, low density, etc. Based on these structures, it shows excellent thermal performance. Its thermal conductivity is~0.012mw/mk, density is~0.16mg/cm3, specific surface area is 400-1000m2/g, porosity is 90-99.8%, its chemical performance is stable, its internal volume is 99% composed of gas, and it is the smallest known density solid.

Since its discovery, aerogel has gone through three times of industrialization, and is currently in the rapid development of the fourth wave of industrialization. Aerogel was born in 1931. Steven S. Kistler published Copolymerization Diffusion Aerogel and Jelly in Nature magazine, marking the discovery of aerogel. It was also Kistler who first prepared the world's first aerogel - SiO2 aerogel through ethanol supercritical drying technology. The first industrialization took place in the early 1940s, but due to the high cost, the first industrialization finally failed. Monsanto Corp. of the United States cooperates with Kistler to produce the aerogel powder named Santocel, which is used as cosmetics, silicone rubber additives, napalm thickener, etc. However, Monsanto terminated its aerogel project in the 1970s due to high manufacturing costs and lagging application development. In the second wave of industrialization, typical representatives of different technical directions appeared. (1) In 1984, the Swedish Airglass Company used methanol supercritical technology, which was used in the Cherenkov detector; (2) In 1989, Thermalux Company of the United States used CO ∈ supercritical technology. Due to poor management, the project was terminated; (3) In 1992, Hoechst Company in Germany produced aerogel powder with atmospheric pressure drying technology, promoting its application in many fields such as thermal insulation coatings and matting agents; (4) In 2003, Tongji University began to publish research papers on atmospheric drying, and Chinese technicians gradually increased their investment in the field of atmospheric drying. The third industrialization took place at the beginning of the 21st century, in which the famous AspenAerogel and Cabot companies were born. In 1999, Aspen Systems of the United States successfully prepared fiber composite aerogel super thermal insulation material under the project of NASA. In 2001, Aspen Aerogel was formally established to carry out the commercial operation of aerogel, and began to promote the application of aerogel insulation felt to aerospace, military and petrochemical fields. This started the third wave of industrialization of aerogel materials, and aerogel gel finally found a good commercial product model. In 2003, Cabot, the world's leading special chemicals and high-performance materials company, acquired the production technology of preparing SiO2 aerogel materials by atmospheric drying through the merger of Hoechst, Germany, and established a professional aerogel company. Its main products are aerogel powder particles, which are used as coating additives or filler layers in daylighting glass. In 2004, domestic enterprises engaged in the industrialization research of aerogel materials began to appear. The fourth industrialization mainly took place in China. With the reduction of the cost of gel process and the continuous expansion of the industrial scale, some new applications have been developed, and the aerogel market has become increasingly mature. Since 2010, the first batch of domestic aerogel production enterprises have successfully developed the application market for energy saving of industrial equipment and pipelines, safety protection of new energy vehicles, fire protection, heat insulation and insulation of rail transit cars and hulls. In 2017, China issued the national standard of Nanoporous Aerogel Composite Thermal Insulation Products (GB/T34336-2017); In the same year, aerogel was listed in the national key energy-saving low-carbon technology promotion directory. In 2019, the output of aerogel in China was 78200 cubic meters, and the market size of aerogel in China was about 1.123 billion yuan in 2019.

The aerogel industry has risen in adversity, and has been continuously valued and developed rapidly in China. In 2016, Aspen Aerogels filed a 337 investigation application to the International Trade Commission (ITC) of the United States, claiming that the products of two Chinese enterprises infringed their patent rights related to composite aerogel insulation materials and manufacturing methods, and requested ITC to issue general exclusion orders (or limited exclusion orders) and injunctions. In 2018, ITC made a partial final judgment of 337 investigations on aerogel thermal insulation composite and its manufacturing process: two Chinese companies were found to have infringed intellectual property rights. This investigation event has caused the domestic aerogel industry and researchers to attach great importance to the patent rights of aerogel gel. Aerogels can be divided into inorganic gel, organic gel, mixed gel and composite gel. The common aerogels are mainly silicon gel, carbon gel and silica gel. The newly developed aerogels are mainly graphene oxide aerogels, fullerene aerogels and fiber/silica aerogels.

At present, the common and more studied materials in the market can be divided into oxide aerogel materials, carbon aerogel materials (high temperature resistance up to 3000 ° C) and carbide aerogel materials.

The aerogel can be compounded with glass fiber, ceramic fiber or carbon fiber to improve the adhesion of the system and prevent the surface from being brittle and powdery. Common products such as air gel glass fiber felt, air gel ceramic fiber felt, pre oxidized fiber, etc. These products are mainly used for thermal insulation of pipe furnace body, etc. They can replace traditional flexible thermal insulation materials with poor environmental protection and thermal insulation performance, such as polyurethane foam, asbestos insulation pad, silicate fiber, etc.

Aerogel materials can also be used as coating materials to add thermal insulation protection on the surface of the substrate. The air gel particles, adhesive, flame retardant and foaming agent are mixed to prepare the air gel adhesive composition, and the heat reflection layer is coated on the surface of the air gel coating, which can greatly improve the heat resistance of the raw materials.

Aerogel materials can also be used together with flame retardants to obtain better flame retardancy and improve the strength and toughness of materials. There is a Sb2O3-SiO2 composite aerogel inorganic flame retardant, which has a large specific surface area. It has a strong interface adhesion with the polymer matrix such as plastics and rubber, improves the dispersibility and fluidity of the composite aerogel flame retardant in the polymer melt, improves the flame retardant effect, and reduces the loss of mechanical properties of the polymer matrix caused by the addition of inorganic flame retardant. Aerogel materials can also be used with textile fibers such as non-woven fabrics, polyester staple fibers, nylon, etc. to make clothing fabrics, which can be used in down jackets, cotton padded jackets, outdoor supplies, fireproof clothing, aerospace clothing, special work clothes and other fields. This material has good thermal insulation, heat insulation, wear resistance, water resistance and wind resistance, and its thermal conductivity is lower than 0.05W/(m ″ K), which is lower than that of down wool. As a whole, it is in the growth period of the life cycle, with vigorous development in many fields. According to IDTechEX Research, as aerogel technology has gradually improved in recent years, most application fields are still in the early and growing stages of aerogel promotion, and regional energy, building construction, clothing, daily chemicals, LNG pipelines and other fields have developed rapidly. At present, the relatively mature fields are mainly oil and gas pipelines (excluding LNG pipelines), refining projects, industrial insulation, etc.

Building construction and transportation will enjoy faster growth. In 2019, most of the downstream applications of aerogel were concentrated in oil and gas projects (56%) and industrial insulation (26%), which accounted for 82% of the market, 6% of building construction and 3% of transportation projects. According to the analysis of IDTechEX Research, the proportion of building construction will increase in 2024. The proportion of applications is expected to double from the original, accounting for nearly 12%. By 2029, the proportion of building construction will reach nearly 18%, the proportion of transportation will also increase to 5%, while the proportion of traditional oil and gas fields will decrease to 41%. Building construction and emerging fields will become the main consumption drivers.

Gas gel materials are mainly used as external insulation materials for energy infrastructure in the energy and chemical field, including insulation materials for distillation towers, reaction pipelines, storage tanks, pumps, valves, natural gas and LNG liquefied gas pipelines, deep-sea pipeline insulation materials, power plant equipment insulation materials, etc. Although the initial investment of aerogel insulation is higher than that of traditional materials, its many excellent properties, lasting energy saving benefits, and significant green environmental advantages make it a cost-effective energy-saving product. High temperature steam, heat transfer oil and process fluid medium pipelines are crucial equipment in the fields of thermoelectricity, oil refining, chemical industry, etc. The pipelines are exposed to the air all the year round, and their heat loss accounts for the vast majority of the natural heat loss in the whole plant area, and the energy retention rate of the conveyed medium is directly related to the quality and quantity of products, so it is important to select excellent thermal insulation materials. At present, the refineries of global large-scale petrochemical enterprises, such as ExxonMobil, Shell, Chevron, PetroChina, Huachang Chemical, etc., use a large number of aerogel materials as thermal insulation materials. Aerogel materials can not only solve the safety problems of current ternary battery systems and other battery systems, but also play a role in flame retardancy in automotive interior materials. The high temperature tolerance of aerogel can solve the safety pain of ternary battery. When the on-board battery outputs electric energy for a long time, the chemical reaction in the battery for a long time will make the battery body obviously heat up, with the risk of combustion and explosion. The traditional core modules use plastic partitions to separate the batteries from each other, which is of no practical use. This is not only heavy but also can not protect the batteries, and it is easy to cause problems such as the dissolution and ignition of partitions due to excessive battery temperature. The existing protective felt has a simple structure and is easy to deform, which makes it unable to fully contact with the battery pack, and it can not play a very good heat insulation effect when the battery heats seriously. The emergence of aerogel composite materials is expected to solve this problem. As a flame retardant material, aerogel composites have the advantages of light weight, excellent flame retardancy and good environmental protection compared with traditional flame retardant materials. At present, there are mainly two kinds of heat insulation and flame retardant materials used for battery core modules of new energy vehicles: 1) plastic PP, ABS, PVC, etc., in which ABS engineering plastics are mainly used. Flame retardant is usually added to PP, ABS and other plastics to make flame retardant plastics; 2) Fireproof felt made of glass fiber, ceramic fiber cotton and other fireproof materials. As a new material, gel has excellent thermal insulation and flame retardancy. The aerogel composite made of gel and engineering materials has excellent flame retardancy. The SiO2 aerogel glass fiber felt composite developed by Pan Asia Micro Permeation can have a thermal conductivity of less than 0.017W/(m ″ k) at room temperature of 25 ° C, and a thermal conductivity of 0.047~0.066W/(m ″ k) at 600 ° C, which can improve the high temperature resistance of the battery pack to more than 800 ° C.