Intelligent PECVD Coatings

Coatings with enhanced functional or mechanical properties are widely requested by industry in key applications such as protective and antibacterial coatings. For example, antiscratch coatings are used to protect a soft material from the abrading effect of external agents; UV-filtering properties are needed to protect plastics or on sunglasses and containers; antibacterial coatings find applications on kitchenware and surgery blades.
Nanoparticles can impart functional properties to coatings and ultimately give added value to industrial products. In particular, the presence of nanoparticles offers improvements with respect to traditional materials, such as better efficiency, stability in time, no need for thermal treatments. The used of pre-formed particles, which are commercially available from a number of nanomaterials suppliers, makes the fabrication of nanostructured objects more simple. For example, alumina and silica nanoparticles are used as fillers in varnishes and lacquers, returning them less prone to scratching. Titania, ceria and zinc oxide are used as UV filters due to their tuneable absorption in the UV range of light. Titania nanoparticles are also used in self-cleaning and antibacterial coatings . The introduction of the nanoparticles can also allow the control of the morphology in the nanometre scale, in order to increase the surface area or to obtain super-hydrophobic coatings.

In all of these applications, a key issue is how to anchor the nanoparticles on the substrate in a stable way on a wide range of substrates. A way around this is to embed nanoparticles in the solgel or polymeric coatings. These kind of coatings in some cases can show drawbacks such as aging, low adhesion, low hardness or curing processes.
An alternative method, which we illustrate in the present work, is to deposit a monolayer of nanoparticles on the substrate and subsequently cover them with a film, which forms a layer around the nanoparticles, fixing them on the substrate. A technique suitable for the deposition of such fixing films is the plasma enhanced chemical vapour deposition (PECVD). In fact this technique allows the deposition of thin uniform coatings on wide surfaces covering surface morphology features also in the nanometre scale. The technique furthermore offers the possibility to coat surface with hard coating at low processing temperature, therefore widening its application field also to temperature sensitive substrates as plastics. This work presents a preliminary study of an approach to anchor nanoparticles to a surface, in order to impart specific properties. In particular, coatings with improved antiscratch properties have been obtained and a nanostructure design is suggested.

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