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Nanocoatings are the nanoscale thin film coatings which are used to protect the surface of various construction materials like glass, marble, concrete, sand limestone, steel and many others. These coatings help protect them from corrosion, friction reduction, heat resistance and environmental influences like moss, algae, water and oil stains.
Nanomaterials have gained a lot of interest in the building industry because of their thermal properties, energy efficiency, air quality improvement, self-cleaning, self-assembly, and anti-bacterial effect. Self-assembly is a process where the components assemble themselves on their own by interacting in a system and forms a larger functional unit.
Different Types of Nanocoatings
There are various kinds of coatings: hydrophobic, hydrophilic, flame-retardant, anti-graffiti, wear resistant, corrosion resistant, and photovoltaic coatings. According to the application and requirement, these coatings are used in the construction industry on surfaces like walls, doors, windows, etc. These nanocoatings also provide a protective layer to the base material.
Hydrophobic and Hydrophilic Coatings
These coatings are mainly used on flat building surfaces and materials like stones, tiles, wood, etc. Hydrophobic coatings repel water i.e., the contact angle of water is greater than 90°. For instance silicon oxide nanoparticle coatings are hydrophobic in nature. They are mainly used to make the surfaces water and corrosion resistant.
On the other hand, hydrophilic coatings attract water and wash away the dirt from the surfaces. Hydrophilic coatings are also known as self-cleaning coatings. These coatings contain photocatalyst nanoparticles which create an oxidising effect on the organic dirt and contaminants when the glass is exposed to sunlight. The oxidation effect loosens the dirt and when it rains, it washes away the dirt from the hydrophilic surfaces. For example thin film of titanium oxide coating on glass acts as a self-cleaning system.
Wear and Corrosion Resistant Coatings
Wear resistant coatings are used to prevent wear, maintain performance level and extend the lifespan of the component. Wear arises due to the increased friction between two interacting surfaces. These coatings protect the surface from damage. Researchers have incorporated nanoparticles of silicon dioxide, aluminium oxide, titanium oxide, and Zirconium oxide to increase the mechanical properties and hardness of the component.
These nanoparticles improve the wear resistance and do not change the transparency of the coatings due to their small size. Therefore nanocoatings can be used to retain the durability and surface appearance of the components like windowpanes and parquet floorings.
Corrosion resistant coatings are used to prevent rust and protect metal components from moisture, mist, salt spray, oxidation and exposure to various industrial or environmental chemicals. These coatings act as a barrier and protect the metal surfaces from chemical compounds and corrosive materials, to increase their possible life span. Few coatings provide both wear and corrosion protection.
Some of the materials which can be used as coatings are fluropolymer for excellent corrosion protection; Polytetrafluroethylene, PTFE, a non-sticky coating which can withstand high temperatures; ceramic epoxy coating as an abrasion resistant coating to protect ceramic particles by binding them to a resin system; nano-alumina particles (Al2O3) for corrosion and oxidation resistance; tungsten oxide (WO3), titanium oxide (TiO2), nickel oxide (NiO2) and vanadium oxide (V2O5) can be applied as the energy efficient coatings as a thin film layer on the window glasses.
Flame Retardant Coatings
Flame retardant coatings are used to protect the materials from fire. These coatings do not modify the substrate chemically but rather forms a protective layer to inhibit combustion, ignition or thermal degradation. The degree of fire retardation primarily depends on the substrates, coating thickness and efficiency of formulations.
These coatings inhibit the combustion of flammable materials like wood, foam, electric cables, textile fabrics, etc. To assess the flammable materials, different test parameters are considered such as flame spread rate, ignition time, heat intensity, oxygen index, smoke generation, and release of toxic gases.
Researchers have prepared flame-retardant coatings by adding magnesium nanoparticles to aluminium-layered double hydroxides, titanium oxide and silicon oxide. They have prepared an emulsion type paint containing nanoparticles of silica and polyacrylate, which has high flame resistance and excellent antipollution properties.
Researchers from Royal Melbourne Institute of Technology, Australia, have developed a paint that can generate clean energy like hydrogen fuel from sunlight and moist air. The paint consists of titanium oxide and molybdenum-sulphide, which absorbs solar energy as well as moisture from the surrounding air. It then splits the water in hydrogen and oxygen and the hydrogen is collected for use in fuel cells or to power a vehicle.
The researchers claim that the paint would be effective in a variety of climates from damp to dry environments near large bodies of water, even remote areas far away from water bodies can produce fuel from the water vapour in the air.
- Boostani, Haleh, and Sama Modirrousta. "Review of nanocoatings for building application." Procedia Engineering145 (2016): 1541-1548.
- Mariappan, Thirumal. "Fire Retardant Coatings." In New Technologies in Protective Coatings. InTech, 2017.