Brilliant colours for everyday products

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 are developing affordable PVD coating technology for improved coatings with work on the project 'Design and develop a new generation of colour PVD coatings for decorative applications' (NANO4COLOR).

Technology focuses on nanocomposite thin-film coatings (less than two microns) in a wide palette of colours. They are made of a dielectric matrix with embedded metallic nanoclusters. Hybrid processing technology will enhance reliability and decrease costs and toxic emissions. Reactive magnetron sputtering (RMS) is being combined with either high-power impulse magnetron sputtering (HIPIMS) or a cluster gun.

Scientists have selected three applications to ensure compatibility with large and complex geometries, transparent and opaque colours, and high coating uniformity of large areas with fine 3D details. The team has now developed the cluster gun prototype and a simulation of nanocluster formation. The gun was used in combination with the original two process technologies as well as a third, combined RMS and annealing, with very promising results.

The nanocomposite design as a route to tailor-made colours was validated showing that control of nanocluster size and distribution produced similar colours with all three coating techniques. Coloured nanocomposite coatings deposited using the cluster gun and HIPIMS have been fully characterised and product prototypes can be seen on the project website.

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 of end-products. As for consumers, they can look forward to a wide variety of beautiful metallic colours in numerous products.