Abstract: In the field of new materials, "aerogel" has become a hot word with increasing frequency in the past two years. Shandong, Jiangsu, Zhejiang, Hunan, Shaanxi, Henan and other provinces have also listed the development of aerogel materials as the key support areas and development focus of the province. On January 6, 2016, the National Development and Reform Commission listed aerogel materials into the national key energy-saving and low-carbon technology promotion directory.

Our country is in the first tier of the international league

In 2014, the World Materials Conference proposed that aerogel is made up of more than 90% air and less than 10% solid. It can withstand thousands of times its own mass and only melt when the temperature reaches 1200℃. It also has low thermal conductivity and refractive index, and is 39 times more insulating than the best glass fibers. Because of these properties, aerogel has become an irreplaceable material in space exploration, used to insulate the Russian Space station Peace and the U.S. Mars Pathfinder spacecraft.

In addition to aerospace applications, aerogel can also be widely used in military industry, petrochemical, electric power, metallurgy, construction, clothing and many other fields, is a revolutionary alternative to traditional thermal insulation materials.

Shen Jun, an expert in the field of aerogel and a professor at Tongji University, introduced that aerogel material is the lightest solid material known in the world today. Currently, the lightest aerogel is only 0.16 mg/cubic centimeter, slightly lower than the density of air, with a huge specific surface area and very low thermal conductivity. A cold coat made of aerogel material is only 3mm thick but has the same insulation effect as a 40mm duck down coat. The jacket also maintained an internal temperature of about 31.6 ° C in a -196 ° C liquid nitrogen test. Aerogel is a kind of amazing nanomaterial that can change the world. The reason why aerogel has such characteristics is mainly due to its special nanoporous structure.

It is gratifying that, different from other new materials, the industrialization level of Aerogel materials in China is almost synchronized with the world, and shows a good trend of catching up. It is understood that in 2001, the establishment of ASPEN Company, which has a close relationship with NASA, was the beginning of the industrialization of aerogel; The research on aerogel in China started in the 1990s, and the first commercial company was established in 2004.

Shen jun said that the current leading aerogel industry is the United States and China, and China has reached the international advanced level. "The overall level is not lower than the international level, some indicators are higher than the US products, the application market is not less than the US." Tongji University professor Ni Xingyuan so summed up to China Chemical News reporters.

The long March 5, China's new-generation high-capacity carrier rocket, successfully made its maiden flight from wenchang Satellite Launch Center in Hainan province on Nov 3, 2016, according to industry sources. Among them, the high-performance nano-aerogel insulation felt independently developed in China provides heat insulation for the rocket gas pipeline system. Aerogel in China is not only used in the aerospace field, but also used in petrochemical, high-speed railway, oil field and other fields, with a wide range of applications in the market.

The golden age of development has arrived

According to a previous report by Allied Market Research, the global market value of aerogel is expected to reach $1.896.6 billion by 2020, with a cagR of 36.4% from 2014 to 2020. As aerogel materials continue to be explored in new application areas, the market growth momentum will be further strengthened.

With the continuous development of application fields, China's aerogel market is expanding rapidly at a rate higher than the international average. In 2014, the domestic production of aerogel was about 8500 cubic meters, and the imported products were about 1500 cubic meters. The market size was about 182 million yuan. Since last year, the aerogel market ushered in a sudden increase in production and sales scale. Jin Chengli, general manager of Zhejiang Shaoxing Shengluo Energy-saving Technology Co., LTD., introduced to reporters that the industry increased production capacity of about 20,000 cubic meters last year, mainly due to the expansion of the aerogel enterprises that have achieved mass production, so that the market scale reached 330 million yuan.

He introduced that in addition to the expansion of original enterprises this year, new enterprises have also become an important force contributing to production capacity. It is estimated that this year's new capacity is also about 20,000 cubic meters. It is expected that aerogel materials will be widely used in industrial and equipment fields from 2015 to 2020. From 2020 to replace the traditional industrial insulation materials, share the domestic annual industrial insulation materials market of about 50 billion yuan; From 2020, aerogel materials will be widely applied in the field of architecture. In 2025, it will fully replace traditional building insulation materials and share the domestic market of more than 100 billion yuan per year. In addition, by 2020, the number of enterprises in the aerogel industry will increase rapidly, the capacity will expand dramatically, and the whole aerogel industry will enter the stage of explosive growth.

Although the prospects are promising. However, at present, China's aerogel materials are still in the early stage of development, and a number of dominant enterprises have not been formed, and no enterprise has formed a stable leading position.

Jin Chengli believes that the next three to five years will be the golden development period of aerogel materials. Enterprises that master low-cost core technologies and certain market resources will gain huge development space and quickly become the dominant enterprises in the industry.

Cost control marketing applications

With the development of time, building insulation material requirements are higher and higher, requiring low proportion, fire prevention, high thermal conductivity. Compared with the existing thermal insulation materials, aerogel felt has lower thermal conductivity and excellent thermal insulation performance. Aerogel mat is thinner and can cover more area with the same mass; In addition, aerogel composite products also in sound insulation, fire, moisture and other aspects of excellent performance.

A number of industry insiders said that the biggest obstacle restricting the expansion of the aerogel market is the price. Ni Xingyuan told reporters: "In the field of building heat insulation, heat preservation, existing heat preservation materials dozens of yuan a square meter. Although aerogel cost more than 200 yuan per square meter two or three years ago, with the large-scale production of aerogel, now it has dropped to more than 100 yuan. However, there is still a gap between the price of aerogel and market acceptance, and I believe it will get closer and closer in the future."

Aerogel mainly includes silica aerogel, alumina aerogel, zirconia aerogel and carbon aerogel due to different components. At present, silica aerogel technology is the most mature and the most widely applied in the market. The industrial development of aerogel at home and abroad mostly revolves around the application of silica aerogel insulation.

The preparation process of carbon aerogel is relatively mature. Carbon aerogel material has been used as anode material of lithium battery and seawater desalination electrode in China. Carbon aerogel materials have been used as optical films with high laser damage threshold in large laser devices. However, the high production cost of carbon aerogel prevents its application and expansion. Experts suggest that the preparation process of carbon aerogel should be simplified to reduce its production cost.

Kim believes that once the production cost of aerogel materials can be significantly reduced, the market price will also fall, and the size of the market will dramatically expand. For example, silica aerogel will revolutionize the replacement of traditional insulation.

Atmospheric drying is the process direction

At present, the preparation of silica aerogel usually includes two main processes: sol-gel and drying. The nanopores and corresponding gel skeletons are obtained by sol-gel process. Due to the surface tension of the solvent inside the gel skeleton, the skeleton would collapse under normal drying conditions. The core of the preparation technology of aerogel is to avoid the collapse of nano-pore structure caused by capillary force during drying.

"It is similar to making tofu," Shen said. "The raw materials are first made into soymilk and then congealed into tofu. If the water in tofu is squeezed out, it becomes dried bean curd. The preparation of aerogel is similar to squeezing out the water in tofu, but the volume cannot be reduced, and gas needs to be added, so it is difficult.

Aerogel drying can be divided into supercritical drying process and atmospheric drying process according to different processes. Supercritical drying technology is the earliest technology to achieve batch preparation of aerogel, and it is also the technology widely used by aerogel enterprises at home and abroad. Through pressure and temperature control, the solvent can reach its critical point in the drying process. The solvent in supercritical state has no obvious surface tension, so that the gel can keep intact skeleton structure in the drying process, and the aerogel can be prepared by removing a large amount of liquid in the coagulation on the premise of maintaining the original structure.

The principle of atmospheric drying process is to select a solvent with low surface tension to replace the water and alcohol with high surface tension in the hole of wet gel, and then hydrophobic modification is carried out on the gel surface to minimize the gel shrinkage. In addition, the effect of capillary pressure can be reduced by adjusting the uniformity of gel holes and enhancing the strength of network skeleton, so that the structure and properties of aerogel prepared under atmospheric pressure are close to those of aerogel prepared by supercritical drying.

Supercritical drying uses high pressure equipment, the general working pressure is as high as 7MPa~20MPa, early investment is high, operation and maintenance costs are also high; Atmospheric drying technology uses conventional atmospheric pressure equipment, because there is no need for high pressure conditions, early investment is low, but the technical threshold is high, formula design and process combination optimization has higher requirements.

Experts believe that atmospheric drying is a new type of aerogel preparation technology, which is the most active research and has the greatest development potential.

"They're all moving in that direction." Ni Xingyuan so told reporters.

Jin Chengli introduced that if aerogel wants to meet the huge market of building insulation, for example, to reach the annual output of 500,000 cubic meters of medium-sized scale, the equipment investment using supercritical drying technology will be as high as billions of yuan, which is not conducive to the expansion and strengthening of aerogel enterprises. By adopting atmospheric drying technology, enterprises can realize larger production scale with less investment and better adapt to the needs of large-scale production in the future.

In addition, due to the limitation of silicon source, supercritical drying technology has limited room to reduce the raw material cost, so it can only improve the production efficiency by optimizing the system. Atmospheric drying, on the other hand, has strong acceptance of cheap silicon source and more freedom in process optimization, so it has more room for cost reduction.

Jin chengli said that atmospheric drying can realize continuous automatic production of aerogel, the efficiency can be increased by 3 to 5 times, product quality stability and production safety level can also be greatly improved.