Silica aerogel is currently the most mature aerogel in industrialization. Due to its brittleness, the application of silica aerogel is greatly limited. To improve its brittleness and enhance its mechanical properties, it is generally achieved by combining it with other materials to improve its mechanical properties.
By compounding silica with other materials to prepare a composite material and applying it in the construction field, while taking into account requirements such as fire resistance and sound insulation, it can meet the new national standards for thermal insulation and insulation materials. Currently, the main method is to enhance the performance of traditional materials by combining aerogel with traditional materials, and the main product forms include coatings, boards, felt materials, etc.
The following will mainly provide detailed introductions in these aspects.
1. Aerogel Glass
Aerogel glass is a new generation of building envelope products developed based on the new material aerogel and traditional hollow glass technology. It can effectively solve the problems of high energy consumption, low safety, and poor comfort of current building glass.
Aerogel glass is a gel core structure formed by filling transparent aerogel in the glass interlayer. The whole is a semi-transparent frosted glass effect, and under sunlight, it appears cyan, white, or blue.
The middle layer of the hollow glass can be filled with transparent aerogel particles or a whole piece of transparent aerogel. Generally, filling the entire piece of aerogel has higher transparency, but the cost of the entire piece of transparent aerogel is high and cannot be widely used. Therefore, currently, the filling of transparent particles is mainly seen in the market.
Fricke et al. prepared a new type of aerogel insulation glass by filling silica aerogel as the interlayer between double-layer glass. The thermal conductivity of this aerogel insulation glass was as low as 0.002 W·m-1·K-1.
Aerogel glass is mainly applied to the lighting roofs of public buildings such as airport terminals, high-speed railway stations, libraries, art galleries, art centers, hospitals, shopping centers, etc., and sunrooms of villas.
Transparent aerogel requires strict control of the sol-gel-drying process and the pore structure of the aerogel to ensure its optical properties. In the actual production process, strictly controlling the above conditions will significantly increase the cost, so currently, aerogel glass is used less in the domestic market and is mainly used for display or demonstration.
While in foreign countries, the desert regions use it more frequently. The Cabot Company in the United States has launched aerogel glass very early. The main and auxiliary halls of the Li Zihian Art Museum project in Xiangjiang New District, with a total area of 1,000 m2 and a height of about 10 m, use aerogel glass for the skylight dome.
It solves the problems of poor indoor light environment in the summer heat and winter cold regions and high energy consumption in summer and winter, and also well meets the comprehensive requirements of buildings for energy efficiency, safety, aesthetics, and comfort.
2. Aerogel Coating System
In recent years, due to the rapid development of nanotechnology and nanotechnology theory, people have become increasingly interested in nano insulation coatings. Zulhelmi-Alif-Abdul A, Shams-Ghah-farokhi F, Jabbari M, Naccm J, et al. conducted extensive research on nano insulation coatings. The application of silica aerogel in the development of insulation coatings has achieved significant research results.
The aerogel insulation coating system is a composite type insulation coating system that integrates barrier-type insulation coatings, reflective-type insulation coatings, and functional primers, with complementary advantages, to form a superior insulation coating system.
According to T/CECS 10126-2021 "Aerogel Insulation Thick Coating System", the thermal conductivity of aerogel coatings is less than or equal to 0.044 W∙m-1∙K-1. Currently, the thermal conductivity of aerogel coatings on the market can be as low as 0.030 W∙m-1∙K-1.
The aerogel coating system is mainly used for building exterior decoration, building walls, roofs, etc., for thermal insulation. The aerogel coating has excellent sound insulation and noise reduction capabilities, with a fire resistance rating of A grade. It has excellent anti-cracking and self-cleaning properties, effectively preventing the cracking and peeling of insulation materials and exterior decorative surfaces caused by thermal expansion and contraction.
Currently, the main producers of aerogel coatings in China include Shanghai Zhongnan Building Materials Co., Ltd., Shenzhen Zhongning Technology Co., Ltd., Jiangsu Chenguang Coating Co., Ltd., and Shenzhen Hengguo Nanotechnology Co., Ltd., etc.
The aerogel coating system has been used in the energy-saving renovation project of 3 million square meters of old buildings. After the exterior walls were coated with a 2 mm aerogel coating system, the actual test results showed good insulation, heat preservation, and waterproofing effects. The average indoor temperature in winter was 5.8 ℃ higher than that of the same orientation buildings that did not undergo energy-saving renovation, and was widely recognized by residents.
The aerogel insulation coating system has also been applied in the insulation and heat preservation project of the four exterior walls of Warehouse 33 and 34 in the Taiyuan Direct Storage Warehouse of China Grain Storage. Through on-site temperature detection and simulation calculation analysis, it was found that after adding the aerogel insulation coating system to Warehouse 33 and 34, the simulated calculation showed that the cold load of the enclosure structure was reduced by 88,338.76 KWh, a decrease of 22.0%. Compared with the unrenovated Warehouse 37, the detection data showed that the average temperature inside the warehouse during the high-temperature period decreased by 3.3 ℃.
3 Aerogel Composite Insulation Board
By combining aerogel, reinforcing fibers, and organic and inorganic adhesives, an aerogel composite insulation board is prepared, which overcomes the weakness of weak strength of aerogel materials, while significantly improving the insulation and heat preservation performance and fire resistance of the board, and reducing the board density, which is used for the insulation of building envelopes.
The preparation process of the aerogel composite insulation board is simple, with low equipment investment, but the molding time is long and the production cycle is long, resulting in high costs. Depending on the type of adhesive, there are four categories: gypsum-based, cement-based, sodium silicate-based, and organic emulsion-based.
The most popular one is the aerogel non-combustible insulation board. It is a type of A2-grade board formed by uniformly mixing cement, polystyrene foam, aerogel powder, and other additives with water and then molding.
The preparation process of the aerogel composite insulation board is simple, with low equipment investment, but the molding time is long and the production cycle is long, resulting in high costs. According to the type of adhesive, there are four categories: gypsum-based, cement-based, sodium silicate-based, and organic emulsion-based.
At present, the most popular is the aerogel composite non-combustible insulation board. It is a type of board formed by uniformly mixing cement, polystyrene foam, aerogel powder, and other additives with water and then molding.
The aerogel composite insulation board has the characteristics of insulation, energy saving, fire resistance, waterproofing, environmental protection, and light self-weight, significantly improving its safety coefficient during use. It has extensive and significant applications in the construction field, especially suitable for the insulation of the exterior walls of prefabricated building concrete structures. The reduction of the thickness of the building envelope can increase the internal usable area of the building, reduce the weight of the wall, and significantly improve the structural safety.
During the epidemic, the aerogel composite non-combustible insulation board was used in the manufacturing of low-carbon nucleic acid sampling rooms. The aerogel low-carbon nucleic acid sampling rooms prepared were purchased in large quantities by the Bao'an District Government of Shenzhen, the Taiyuan Municipal Government, and other authorities for epidemic prevention and control.
Compared with the nucleic acid sampling rooms prepared using rock wool boards of the same thickness, the nucleic acid cabins prepared using the aerogel composite non-combustible insulation board have efficient insulation, reduce carbon emissions, and the carbon reduction rate is 60%. After the epidemic, the nucleic acid cabins were transformed into newsstands, volunteer stations, breakfast vending booths, and traffic police stations, achieving a rapid transition from epidemic to normal.
4 Aerogel composite insulation blanket
The Aerogel composite insulation blanket is currently the most commercially successful aerogel material. According to the base material, the types of aerogel composite insulation blankets include aerogel glass fiber needle-punched blanket, aerogel glass fiber surface blanket, aerogel ceramic fiber blanket, aerogel ceramic surface blanket, aerogel pre-oxygenated fiber blanket, etc. Aerogel composite insulation blankets are mainly used in aerospace and military fields.
In recent years, with the expansion of the industrial scale of silica aerogel, its cost has also significantly decreased, and it has gradually been applied in the construction field. Currently, the main application in the construction field is aerogel glass fiber needle-punched blanket.
Compared with traditional wall insulation materials such as rock wool, concrete blocks, and extruded polystyrene boards, aerogel glass fiber blanket is an inorganic material, with excellent thermal insulation performance. Its thermal conductivity is as low as 0.017 W∙m-1∙K-1, the fire resistance grade can reach A1 level, has good sound insulation performance, is overall water repellent, and can meet the requirements of thermal insulation, sound insulation and fire protection for wall insulation. Even more, silica aerogel blankets are made into sandwich structures, enabling them to be directly applied to external wall insulation.
The owners of a certain residential community in Shenzhen used aerogel blankets for the entire ceiling and walls for sound insulation and thermal insulation protection. Compared with the same type of layout， the electricity consumption of air conditioners in summer decreased by 40%， the sound insulation between upstairs and downstairs was 20 decibels， the thickness of the wall insulation layer was reduced to within 20mm， and the performance indicators reached the 75% energy-saving requirements of the country.