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The coating of materials has happened for many years, and the coating industry has become a very large and well-established sector; utilized across a wide range of applications and markets. In recent years, there has been a shift from using bulk materials to using nanomaterials, and this has meant that coating methods have had to change as a result.
Drawbacks of Traditional Coating Methods
Many traditional and well-established coating methods cannot be used on nanomaterials. Nanomaterials are too small for these methods, but to perform like their bulk counterparts (and in some cases predecessors), the nanomaterials still need to be coated.
The ability to coat a material at the nanoscale is known as nanocoating and has not only provided a way to coat the nanomaterials used in everyday products but can also be used to coat a bulkier material with an extremely thin layer coating. This enables the properties of a coating to be achieved without affecting the topography of the surface, unlike conventional thicker coatings.
An Overview of Nanocoatings
Nanocoatings are applied to materials by nanodeposition methods. The method used is often tailored depending on the surface being coated, as well as the composition and thickness of the coating, the geometry of the surface, and the properties that need to be achieved.
These methods can range from nanoscale polymerization reactions to chemical vapor deposition (CVD), physical vapor deposition (PVD), and atomic layer deposition (ALD). All methods have their advantages and disadvantages, so the chosen method is tailored to each scenario, and this is something that is unlikely to change.
Just like conventional coatings, nanocoatings are applied to provide certain or multiple benefits. In a broad sense, these benefits can include anything from increased stability/protection and environmental conditions (barrier effects), to an increase in performance and efficiency, increased lifespan, and increased strength. It can even be made conductive/insulating depending on requirements.
Overall, the most common use is to provide some kind of barrier against the environment that the material is being used in, and nanocoatings are known to provide a barrier against UV radiation, water, harsh chemicals, static, oil, sweat, scratches, bacteria, corrosion, fungus, and friction, to name a few.
Nanocoatings can also come in a range of thicknesses, but to be considered a nanocoating, the coating layer(s) need to be somewhere between a single atomic layer (which is possible) to a few hundreds of nanometers (often up to 100 nm). Nanocoatings can also be made up of a single composition, or they can be layered, where each layer has a different molecular composition. This is how they are often tuned and tailored to a specific application, and the use of multiple layers is often the reason why multiple benefits can be realized.
Applications of Nanocoatings
In terms of where they are used, nanocoatings are used in materials that are present in everyday electronic devices, batteries, catalysis, semiconductors, microelectromechanical systems (MEMS), transistors, fuel cells, solar cells, and various implants, as well across the automotive, medical, marine, pharmaceutical, and telecommunications industries.
Regarding a specific application example, nanocoatings can be applied to batteries to not only increase performance of the battery in terms of its charge and discharge cycles, but they can also be used to simultaneously increase the safety and longevity of the battery by better dissipating any excess heat generated within the battery and protecting the components against environmental factors, including internal gas build-ups (which often happens in batteries and nanocoatings can reduce the production of these gases). This is just one example where nanocoatings yield multiple benefits, and there are many more applications out there that benefit from the use of nanocoatings.
A nanocoating can also be introduced to induce specific effects onto the surface of a material. Two common examples include making surfaces superhydrophobic and superoleophobic, which repels most water and dirt to act as a self-cleaning anti-fouling surface, and to make surfaces antibacterial in nature without increasing the antibiotic resistance of the bacteria that can inhabit the surface.
These are just some of the examples of what happens when materials are nanocoated, but the possibilities are limitless, especially when it is now possible to coat practically any molecular composition in a nanoscale form, on practically any surface geometry (even nanoparticles and other spherical particles) in the desired thickness—all of which enable the properties of the nanocoating to be fine-tuned to achieve a specific effect/effects. As the shift from bulk materials to nanomaterials continues, the use of nanoscale deposition technologies to create functional nanocoatings is only likely to increase.
Sources and Further Reading