New coating technology enables a broad spectrum of colours
Coatings have become ubiquitous, whether to impart aesthetic properties such as brilliant colours or shine or functional properties such as increased hardness or corrosion resistance. Physical vapour deposition (PVD) is an important plasma coating technology that relies on vaporising materials under vacuum conditions. It is one of the most promising processes as it delivers brilliant and decorative finishes with superior hardness and wear resistance and minimal environmental impact. Excessive cost and limited process reliability have prevented more widespread use in less-expensive items for areas including construction, cars, appliances, and micro- and optoelectronics. EU-funded scientists developed affordable PVD coating technology for improved coatings with work on the project NANO4COLOR (Design and develop a new generation of color PVD coatings for decorative applications). The colour palette includes green and red tones overcoming the barrier associated with use of PVD coatings with a restricted composition. New coating hardware, a cluster gun and coating processes were developed and successfully used to deposit different colours such as red, green, pink and orange in 3D objects with different substrate composition, surface finishing and size. In particular, scientists employed different PVD approaches for depositing nanocomposite coatings made of dielectric matrices (aluminium oxide or titanium dioxide) with embedded metallic nanoclusters (silver, gold, nickel or copper). Coating consistency and reproducibility was achieved in tens of produced demonstrators. Results demonstrated that it is possible to tailor optical properties and achieve a wide range of different colours by controlling the nanocluster size, shape and distribution. Optical properties were also found to depend on the properties of the dielectric medium in which nanoclusters are dispersed. In addition, the team used optical simulation tools to develop models that were able to predict and define coating characteristics. Affordable, durable and environmentally friendly coloured PVD coatings for a variety of everyday products will have important positive impact on producers of decorative coatings and end-products. As for consumers, they can look forward to a wide variety of beautiful metallic colours in numerous products.
Keywords
Coating technology, colours, physical vapour deposition, NANO4COLOR, nanoclusters
