Aerogel Coatings: Classification, Core Applications, and Safety Protection in Future Life

I. Understanding Silica Aerogel: The "Super Filler" for Functional Coatings

Silica aerogel is mainly composed of air and a silica framework. Its three-dimensional nano-network structure endows it with many unique properties: an apparent density of only 0.003-0.35g/cm³ (lighter than air), a specific surface area of up to 800-1000m²/g, a porosity as high as 80.0%-99.8%, and a thermal conductivity as low as 0.008-0.043W/(m·K). These characteristics make it an ideal "super filler" for enhancing coating functions. When aerogel is added to coatings, it can give them special capabilities such as heat insulation, fire resistance, and high-temperature resistance without increasing the weight of the coating or affecting its basic film-forming effect.

In the past, aerogels were mostly used in aerospace, high-end industry, and other fields; now, with the advancement of preparation technology, they are gradually extending to civil fields, and aerogel coatings are an important carrier for their "integration into daily life".

II. Preparation of Silica Aerogel Coatings: From Nanoparticles to Usable Coatings

The preparation of aerogel coatings centers on silica aerogel and goes through three key stages, each directly affecting the performance of the final coating.

1. Step 1: Preparation of Silica Aerogel

First, a wet gel is prepared by the "sol-gel method" — the silicon source (such as tetraethyl orthosilicate) is mixed with a solvent, and after adding a catalyst, the silicon source gradually hydrolyzes and condenses to form a gel containing a large amount of water (wet gel). Then, the wet gel needs to be dried:

• Supercritical drying method: It can retain the nano-pores and three-dimensional framework of the wet gel to the greatest extent, and the prepared aerogel has the best performance. However, it requires high-pressure equipment, has a long production cycle and high cost, and is suitable for high-end industrial coatings.

• Atmospheric pressure drying method: By controlling temperature and humidity, the moisture in the wet gel volatilizes slowly. It has lower cost and simpler operation, and has now become the mainstream drying method for civil aerogel coatings, but additives need to be added to prevent the framework from collapsing.

2. Step 2: Preparation of Aerogel Slurry (the Most Critical Link)

The dried aerogel is a nano-sized powder that is prone to agglomeration (particles stick together to form large lumps). If directly added to the coating, it will lead to uneven performance. Therefore, it is necessary to first make aerogel slurry:

• Add dispersants (such as polycarboxylate dispersants) and stabilizers, and break the powder agglomeration through high-speed stirring or ultrasonic dispersion technology.

• Ensure that the aerogel nanoparticles are uniformly dispersed in the solvent to form a stable slurry — this step determines whether the functions of the final coating are stable. For example, the thermal conductivity of thermal insulation coatings and the flame retardant effect of fire-resistant coatings are directly related to the dispersion degree of the slurry.

3. Step 3: Mixing into the Final Coating

Mix the aerogel slurry with film-forming resins (such as silicone resin, acrylic resin), pigments and fillers (such as titanium dioxide, ceramic beads), and other additives (such as defoamers, leveling agents), then stir evenly with a high-speed disperser to make aerogel coatings. According to different application scenarios, the proportion of each component will be adjusted. For example, thermal insulation coatings for exterior walls will add weather-resistant additives, and fire-resistant coatings for kitchens will increase the flame-retardant proportion of pigments and fillers.

III. 6 Major Functional Classifications of Aerogel Coatings: Application Scenarios from Industry to Daily Life

The core value of aerogel coatings lies in "functional customization" — depending on the added aerogel characteristics, pigments, fillers, and additives, 6 core functions can be achieved, covering multiple scenarios from industrial equipment to family life.

1. Aerogel Thermal Insulation Coatings: Making "Cooling" More Energy-Efficient

The nano-pores of aerogel (with an average size of 20nm) can disrupt the heat transfer path: on the one hand, the air in the pores cannot flow freely, inhibiting convective heat transfer; on the other hand, countless pore walls will reflect and refract thermal radiation, forming an "infinite heat insulation board effect". Therefore, the thermal insulation effect of coatings added with aerogel is far better than that of traditional coatings.

• Transparent thermal insulation coatings: Applied to the glass of homes or office buildings, they can block near-infrared light of 760-2500nm (the main source of heat in sunlight) while allowing visible light of 400-760nm to pass through (without affecting lighting). In summer, they can reduce air conditioning power consumption, and in winter, they can reduce indoor heat loss.

• Wall thermal insulation coatings: Applied to the inner and outer walls of buildings, cold storage walls, or warehouses, they only need 1/3 the thickness of traditional insulation materials, are more convenient to construct, and have better fire resistance (traditional organic insulation materials are flammable). For example, the Zero Carbon Pavilion at the 2010 Shanghai World Expo used such coatings, and it was measured that the indoor temperature could be 3-5℃ lower than the outdoor temperature, with significant energy-saving effects.

2. Aerogel High-Temperature Resistant Coatings: Safeguarding Safety in High-Temperature Environments

Aerogels can maintain a stable porous structure below 900℃. To withstand higher temperatures (such as 600-1200℃), high-temperature resistant pigments and fillers (such as modified potassium hexatitanate whiskers, silicon-aluminum-based ceramic beads) are added to the coating to work synergistically with the aerogel.

• Industrial scenarios: Applied to the surface of high-temperature steam pipelines, petroleum cracking furnaces, and metallurgical equipment, they can reduce heat loss, protect equipment from high-temperature corrosion, and extend service life.

• Life-related scenarios: Applied to the surface of components in the automobile engine compartment, they can insulate the high temperature of the engine and prevent surrounding lines from aging due to high temperature; in the future, they may also be used on the inner walls of household ovens to reduce the temperature of the outer wall of the oven and avoid accidental scalds.

3. Aerogel Fire-Resistant Coatings: Adding a Line of Defense for "Flame Retardancy"

Aerogel itself is a flame-retardant material, and its pore size (2-50nm) is smaller than air molecules (the mean free path of nitrogen and oxygen is 70nm). If the coating film is dense enough, it can prevent air from contacting the substrate. At the same time, the extremely low thermal conductivity can reduce the flame temperature, making the substrate unable to reach the ignition point.

• Construction scenarios: Applied to the surface of wooden furniture, ceilings, and steel structures, they can delay the spread of fire in case of a fire and buy time for escape.

• Household scenarios: In the future, they can be used on kitchen walls and countertops around gas stoves. In case of sparks or cooking oil fires, the coating can prevent the spread of flames and reduce the risk of fire; applying such coatings to the walls of children's rooms can also reduce the danger when children come into contact with fire sources.

4. Aerogel Adsorbent Coatings: Making "Purification" More Efficient

The ultra-large specific surface area (up to 1000m²/g) and high surface activity of silica aerogel make its adsorption capacity for organic solvents, harmful gases, and impurities far exceed that of traditional adsorbents such as activated carbon and silica gel, and it can be reused after desorption (the adsorption capacity can be restored by heating or ventilation after adsorption saturation).

• Industrial scenarios: Applied to the inner walls of sewage treatment equipment, they can adsorb organic matter and heavy metal ions in water; applied to the exhaust gas treatment pipelines of factories, they can adsorb volatile organic compounds (VOCs).

• Future life scenarios: They may be used in the filter coating of household water purifiers to improve water purification effects; they can also be applied to the inner walls of wardrobes in newly decorated houses to adsorb harmful gases such as formaldehyde and benzene, making indoor air safer.

5. Aerogel Photocatalytic Coatings: "Cleaning" the Air

The high porosity of aerogel allows photocatalysts (such as TiO₂, WOₓ-TiO₂) to be uniformly dispersed, and the ultra-large specific surface area can increase the contact area between the catalyst and pollutants, improving photocatalytic efficiency — under visible or ultraviolet light irradiation, such coatings can decompose harmful gases and sterilize.

• Experimental data shows that aerogel coatings containing 5% WOₓ-TiO₂ photocatalyst can achieve a formaldehyde degradation rate of 84.62% within 3 hours; coatings containing TiO₂-SiO₂ aerogel can achieve a degradation rate of 77% for industrial dyes (rhodamine B) within 4 hours.

• Life applications: Applied to indoor walls and ceilings, they can continuously decompose formaldehyde and TVOC in the air and kill bacteria (such as Escherichia coli), which is especially suitable for newly decorated houses, hospital wards, children's rooms, and other scenarios; applied to outdoor walls, they can also decompose organic matter attached to PM2.5, helping to improve air quality.

6. Aerogel Sound Insulation and Absorption Coatings: Making the Environment Quieter

The low sound velocity characteristics and connected pores of aerogel allow sound waves to friction with the pore walls after entering the coating, converting sound energy into heat energy, thereby reducing noise. At present, such coatings are mostly used in combination with other sound-absorbing materials (such as sound insulation cotton) to improve the overall sound insulation effect.

• Construction scenarios: Applied to the walls or ceilings of shopping malls and office buildings, they reduce the transmission of crowd noise and equipment noise.

• Life scenarios: Applied to the walls of family bedrooms or under the floor, they can insulate outdoor traffic noise and the footsteps of neighbors upstairs; applied to the surface of automobile interiors, they can reduce engine noise and wind noise, making the car quieter.

IV. The Future of Aerogel Coatings: Safety Protection from "High-End Industry" to "Daily Life"

With the advancement of the country's "dual carbon" policy and the development of new industrialization, aerogel, as a strategic frontier material, is ushering in an outbreak period of applications — and aerogel coatings will be one of the first forms to enter ordinary people's lives. In the future, they will protect our safety in three aspects:

1. Home safety: Home walls will use "multi-functional coatings" combining aerogel thermal insulation + fire resistance + photocatalysis, which save energy in summer, keep warm in winter, decompose formaldehyde, and prevent small fires from spreading; window glass will be coated with transparent thermal insulation coatings, kitchen walls with fire-resistant coatings, and wardrobe inner walls with adsorbent coatings, making the home environment safer and more comfortable.

2. Traffic safety: Automobile engine compartments will use high-temperature resistant coatings to protect components, interiors will use sound insulation coatings to reduce noise, and car bodies will use thermal insulation coatings to reduce high temperatures in the car in summer; the inner walls of high-speed rail and subway carriages will be coated with photocatalytic + sound insulation coatings, which can purify the air inside the carriages and reduce driving noise.

3. Construction safety: Exterior walls and ceilings of new residential buildings will be standardly equipped with aerogel thermal insulation + fire-resistant coatings to reduce fire risks and air conditioning energy consumption; walls of public places such as schools and hospitals will use higher-spec photocatalytic + fire-resistant coatings to ensure safety in crowded scenarios.

In the future, we may not pay special attention to the existence of "aerogel", but it will quietly integrate into every corner of life in the form of coatings, providing invisible protection for energy conservation, safety, and health.

V. Conclusion

Silica aerogel coatings, with their unique functional advantages, are breaking the application boundaries of traditional coatings — from high-temperature protection of industrial equipment to energy conservation and safety in family life, each classification corresponds to the needs of actual scenarios. With the reduction of preparation costs and the maturity of technology, aerogel coatings will not only become a "popular functional coating keyword" in Google searches but also a "visible and usable" safety partner in ordinary people's lives.