Coating Techniques
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Coating techniques
Spin coating
Spin coating is a method used to apply a thin uniform layer onto flat surfaces. In spin coating, only a small amount of coating material is applied at the centre as it spins at a significantly low speed or does not spin at all. The spin coating method helps make polycrystalline inorganic coatings and amorphous films (Kelso et al., 2019). While controlling the thickness of the spreading liquid, it is possible to achieve epitaxial growth using single-crystal substrates. This technique is simple and easy to master. Additionally, it is more pocket-friendly for creating individual films.
Dip coating
Dip coating is when a substrate is immersed into a tank with the coating material. After immersing the substrate, you remove it from the tank and then allow it to drain, after which you can apply any technique of drying, for example, baking or force-drying it. Dip coating is applicable in making highly-conductive glass fibre using graphene as a multifunctional coating (Fang et al., 2019). This process involves partially reducing Graphene Oxide to graphene hydrosol, then dipping the glass fibres into the reduced graphene oxide (rGO). This method produces glass fibres with high electrical conductivity (24.9 S/cm). To regulate the glass fibre’s wettability and conductivity, we control the number of dipping times and the coating material’s thickness. Dip coating is effective for creating uniform coating, and it is very pocket-friendly.
Spray Coating
Spray coating is a technique in which particles or droplets are sprayed into a substrate. In thermal spraying, a technique commonly applied in spray coating, solid material such as a rod or wire is melted, then sprayed into the substrate in that nature. To reduce energy loss by radiation in windows, spraying a coating material produces a highly transparent window with radiation reduced by up to 32.8% (Lin et al., 2019). The coated product exhibits high light transmittance (83.0%), significantly reduced emissivity and prolonged durability. Spray coating helps create a higher density, which brings tougher coatings due to the high impact velocity.
Pour Coating
Pour coating is a technique of mixing paint such as acrylic paint with a pouring medium, then using several ways to pour the resultant liquid into a surface. In pour coating, it is important to ensure that the substances mixed have the archival quality, which implies that they meet the intended product’s performance standards. In an investigation of silver-titanium dioxide nanocomposite materials’ properties, the pour plate technique was used to synthesize nanoparticles, nanospheres, and nanorods (Muflikhun, 2019). Combining this technique with McFarland standards showed that the nanocomposite material was suitable for effective coating and eradicated bacteria. Pour coating is easier to take and requires no pre-dying on the substrate, making it cost-effective.
Bar Coating
The bar coating technique places an excess solution on the substrate, then spreading it all over using a bar. The bar used for spreading is long and cylindrical. It has a spiral wire around it. The film thickness is dependent on the amount of solution that passes through the gaps between the wires. An investigation to demonstrate the optical and electrical anisotropies of a bar coated film reveals that the coating speed affects the polymeric aggregation (Yabuuchi et al., 2019). This investigation implies that to determine the quality of product resulting from bar coating, the spreading bar’s speed is important. Bar coating is suitable for large-scale use and creating thicker films from viscous solutions.
References
Fang, M., Xiong, X., Hao, Y., Zhang, T., Wang, H., Cheng, H. M., & Zeng, Y. (2019). Preparation of highly conductive graphene-coated glass fibres by sol-gel and a dip-coating method. Journal of Materials Science & Technology, 35(9), 1989-1995.
Kelso, M. V., Mahenderkar, N. K., Chen, Q., Tubbesing, J. Z., & Switzer, J. A. (2019). Spin coating epitaxial films. Science, 364(6436), 166-169.
Lin, S., Wang, H., Zhang, X., Wang, D., Zu, D., Song, J., … & Wu, H. (2019). Direct spray-coating of highly robust and transparent Ag nanowires for energy-saving windows. Nano Energy, 62, 111-116.
Muflikhun, M. A., Frommelt, M. C., Farman, M., Chua, A. Y., & Santos, G. N. C. (2019). Structures, mechanical properties and antibacterial activity of Ag/TiO2 nanocomposite materials synthesized via HVPG technique for coating application. Heliyon, 5(4), e01475.
Yabuuchi, Y., Uzurano, G., Ishiura, R., Nakatani, M., Nagano, S., Fujii, A., & Ozaki, M. (2019). Coating speed dependence of main chain orientation and aggregation of PBTTT-C16 in the bar-coated thin film. Japanese Journal of Applied Physics, 59(SD), SDDA04.