AVS 50th International Symposium
    Advanced Surface Engineering Tuesday Sessions
       Session SE-TuM

Paper SE-TuM6
Design of Functional Coatings

Tuesday, November 4, 2003, 10:00 am, Room 323

Session: Nanostructured, Nanocomposite, and Functionally Gradient Coatings
Presenter: D. Hegemann, Swiss Federal Laboratories for Materials Testing and Research EMPA, Switzerland
Authors: D. Hegemann, Swiss Federal Laboratories for Materials Testing and Research EMPA, Switzerland
A. Fischer, Swiss Federal Laboratories for Materials Testing and Research EMPA, Switzerland
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Since materials are commonly chosen with respect to their bulk characteristics, availability, mechanical properties, and costs, their surface characteristics often do not meet the demands for special applications. The plasma technology is an appropriate method to tailor surface properties selectively and offers a convenient way to design even functionally gradient surface coatings. Using low pressure plasmas, various materials and geometries can be treated in batch or reel-to-reel reactors. When long-term stable surface properties such as wettability are of great interest, well-adherent, stable coatings can be provided minimizing aging effects. Using low power inputs in the course of chemical vapour deposition (CVD) processes, monomer structures can be retained in the gas phase yielding dense and homogeneous functional gradient films. The evaluation of the deposition rate of these radical-dominated plasmas was proven to be an appropriate way to design functionally gradient coatings, since also hints for the optimum deposition conditions are given. Chemicals containing functional groups such as amino, carboxy or epoxy are used to mediate the adhesion between substrate and coating. Siloxane-based plasma coatings enable the deposition of hydrophobic, polymer-like layers or hydrophilic, quartz-like films. Gradient layers are suitable to enhance the adhesion of the functional coatings e.g. by adaptation of the mechanical properties, when an inorganic coating is deposited on a polymeric substrate or an organic coating on a non-polymeric material. These gradient layers can be designed considering the reaction parameters power per gas flow and plasma potentials, which control deposition rate, chemical composition, and mechanical properties. Finally, an example of a physical vapour deposition (PVD) process is given, in which a nm-thin silver film has been coated continuously onto the surface of multifilament yarns to enhance the dischargement of a textile surface.