The facts have proved that this coating has outstanding energy-saving effects.
(1) Aerogel High-Temperature Resistant Coatings
Aerogel high-temperature resistant coatings refer to a functional coating that can be used for a long time in a high-temperature environment above 200℃， can protect the substrate， and the physical and chemical properties of the coating itself can still remain relatively stable. Aerogel can maintain a good porous network structure characteristic below 900℃， but when the temperature reaches above 900℃， the Si-O-Si network structure will undergo sintering， the Si-O-Si network structure will shrink and aggregate， the pore structure will be damaged， the specific surface area will drop sharply with the temperature reaching 900℃， and the thermal conductivity will increase with the increase of temperature. To maintain the original nano-pore network structure of aerogel at extremely high temperatures and keep its low thermal conductivity and high porosity， the general method is to prepare high-temperature resistant composite materials by doping other high-temperature resistant materials.
The excellent high-temperature resistance of aerogel is the main reason for preparing high-temperature resistant aerogel coatings. Now， high-temperature resistant aerogel coatings have been prepared. With nano-aerogel， modified potassium hexaammonium titanate whiskers (PTW)， silicon-aluminum-based ceramic hollow microspheres， etc. as the main functional fillers， and high-temperature resistant organic silicone resin emulsion and acrylic emulsion as the film-forming materials， they can be prepared into high-temperature resistant insulation coatings with the cooperation of various functional additives. The prepared high-temperature resistant insulation coatings have a low thermal conductivity， ranging from 0.027 to 0.031， and can withstand a temperature of 600℃. They have good heat resistance.
Aerogel high-temperature resistant coatings have the characteristics of thin thickness， high-temperature resistance， and insulation， and in a high-temperature environment， the thickness of the coating can be selected according to the ambient temperature and the required cooling amplitude， with good adaptability and controllability， and have extremely wide applications. They can be applied to high-temperature steam pipelines， high-temperature furnaces， petroleum cracking equipment， engine parts， and metal high-temperature protection in the metallurgical industry， etc.
(2) Aerogel Fireproof Coatings
Aerogel fireproof coatings are coatings applied to the surface of flammable substrates， which can effectively prevent the transfer of heat， reduce the flammability of the substrate and delay or even prevent the spread of fire. They can increase the fire resistance limit of the coated substrate. Aerogel fireproof coatings mainly work through the fact that aerogel is a non-flammable substance， thus giving the coating a non-flammable property. The pore size of aerogel is between 2 and 50nm， and the average free path of the main components of air， nitrogen and oxygen is about 70nm. If the coating is dense enough， it can effectively prevent the protected substrate from direct contact with air. Aerogel has an extremely low thermal conductivity， which can significantly reduce the flame temperature and prevent the protected substrate from reaching its own ignition point. With aerogel as the functional filler， uniformly dispersed in the stable system of the coating， when the coating is brushed to form a coating， it can effectively play a good insulation protection role， thereby improving its fire resistance and achieving the function of fire prevention.
Fireproof coatings made with aerogel as the main functional filler can be applied in numerous scenarios to protect buildings, equipment, and personnel safety, and their fireproof effect is much better than that of ordinary fireproof coatings and other fireproof materials.
(3) Aerogel Adsorption Coatings
Silicon dioxide (SiO2) aerogel has a nano-porous network structure, along with its huge internal surface area, which endows it with the structural characteristics of an adsorption material. It has an extremely strong adsorption capacity for organic solvents and organic substances, and its adsorption performance is better than that of common adsorbents (activated carbon, silica gel, alumina, molecular sieves, etc.). Additionally, due to the large number of surface atoms on the aerogel, there are no adjacent atoms for them to combine with, resulting in high chemical activity on the aerogel surface and the ability to easily adsorb other atoms, thus having a strong adsorption effect.
Through the comparison of adsorption material tests, it was found that silica aerogel is superior to activated carbon fibers (activated carbon fibre, ACF) and activated carbon granules (granule of activated carbon, GAC). The experiment also revealed that silica aerogel can be desorbed for re-adsorption, and the re-adsorption capacity remains basically unchanged. Silica aerogel has excellent adsorption and desorption properties and can be combined with other substrates to form new adsorption materials. Whether it is the silica aerogel itself or the new material formed by its combination with other substrates, its adsorption performance is enhanced compared to common adsorbents. However, currently, the use of it as the main functional filler to prepare adsorption coatings is relatively rare, and this will be an important direction for the future development of adsorption coatings.
Silica aerogel adsorption coatings can be recycled and are environmentally friendly, possessing excellent development potential. They can be widely applied in air purification, wastewater treatment, water vapor adsorption, medical filtration, seawater desalination, etc., and have broad application prospects.
(4) Aerogel Photocatalytic Coatings
Silica aerogel prepared by sol-gel method has a maximum porosity of up to 99.8% and a maximum specific surface area of nearly 1000 m2/g. These inherent properties have attracted significant attention in the application of catalysts. Aerogel photocatalytic coatings have catalytic reaction functions under certain wavelength light irradiation. This coating has the functions of decomposing toxic substances, sterilization and disinfection, degrading organic substances, and purifying the air. The special properties of aerogel make it possible to establish an efficient catalytic degradation system and achieve high-level utilization of aerogel, providing a theoretical basis for the study of the photocatalytic mechanism of aerogel materials on pollutants and new application prospects.
Bai Lunnan et al. synthesized silica aerogel/WOx-TiO2 composite air purification coatings by adding silica aerogel and WOx-TiO2 composite photocatalytic particles as the main functional inorganic photocatalyst. The experiment showed that when the photocatalyst accounted for 5.0% of the coating's mass fraction, it had a stable and high photocatalytic rate. When used for photocatalytic degradation of formaldehyde gas, the degradation rate of formaldehyde gas within 3 hours was as high as 84.62%. Aerogel photocatalytic coatings not only have the ability to degrade harmful gases in the air but can also be used for catalytic degradation of pollutants in industry. Chen Chen et al. used TiCl4 and industrial water glass as raw materials and prepared TiO2-SiO2 aerogel through sol-gel and atmospheric drying methods, and used ethanol as a dispersant to form TiO2-SiO2 composite aerogel coatings. After 4 hours of visible light irradiation, the efficiency of photocatalytic degradation of rhodamine B (the most commonly used organic dye in industrial production) by this aerogel coating reached 77%.
The photocatalytic degradation performance of TiO2-SiO2 aerogel was also studied. Wang Yudong et al. conducted a comparative experiment by comparing it with TiO2 powder. The results showed that in any acidic or alkaline environment, the photocatalytic effect of TiO2-SiO2 aerogel was far superior to that of TiO2 powder, and at pH = 9 and for 6.5 hours, its degradation rate reached 97%. Currently, the global industrial development is rapid, and people's living standards have been significantly improved. Society increasingly values green, environmental protection, and energy conservation. Pollution control has become a hot issue of concern in the world. Photocatalysis, as an emerging environmental remediation technology, has increasingly attracted people's attention in the application for pollution control.
(5) Aerogel sound insulation and sound absorption coating
Silicon dioxide (SiO2) aerogel has a low sound velocity and can be used as a sound insulation and absorption material. Its mechanism of action lies in that it has a large number of tiny interconnected pores. Sound waves can penetrate these pores and interact with the aerogel, converting sound energy into heat energy, thereby achieving sound insulation effects.
At present, there are few cases of using aerogel alone as an acoustic material. It is usually combined with other materials to form acoustic materials, or aerogel coatings are applied to the surface of other acoustic materials to create more effective sound insulation materials. Aerogel can be used as a sound insulation and absorption material to make various forms of sound absorption bodies, which can be used in various occasions such as households, shopping malls, office buildings, industrial equipment, etc., that require sound insulation and absorption.
Outlook
With the successive introduction of national policies, the acceleration of new industrialization, and the development of new quality productive forces, as a national basic strategic frontier material, the application of aerogel will show a burst-like development. Under the background of dual carbon, new functional aerogel coatings will surely have a broader market and development prospects.