Summary
Successful fabrication of high-performance functional coatings strongly depends on the quality of the substrate surface. This module focuses on the analysis of different types of technological substrates such as plastics, glass and ceramics, and metals, and gives an overview of interface engineering and surface treatment and modification approaches in order to assure good adhesion, coating stability, suppression of defect formation, and to further enhance performance of the coating-substrate systems in different areas of application.
Topics
Introduction and General Concepts
-
- Real life problems related to substrate surface characteristics: delamination, cracking, stress accumulation, defect formation, surface contamination, near-surface inhomogeneity, surface roughness statistical parameters, surface energy, surface chemistry, morphology and microstructure. Examples of coating failure;
- Guidelines for substrate surface preparation: mechanical polishing, wet chemical cleaning, plasma- and ion-assisted surface treatment, modification and activation;
- Main techniques for the assessment of substrate surface quality – optical and electron microscopies, surface spectroscopies, atomic force microscopy, surface wettability and others.
Plastic Substrates:
-
- Characteristics of as received substrates – effect of contaminants, molecular weight distribution, additives, thermo-mechanical (thermal expansion coefficient) and elastoplastic properties;
- Surface treatment: Wet chemical, flame, and corona surface cleaning, plasma modification, activation and stabilization – formation and control of “interphase” due to VUV photons and ion-induced intermixing, formation of strong covalent bonds; adhesion testing and interphase analysis;
- Case studies: Antireflective coatings on optical plastics with “interphase-enhanced” design (e.g., ophthalmic lenses), gas and vapor permeation barriers for packaging and encapsulation.
Glass Substrates:
-
- Characteristics of as received substrates – contaminants, defects;
- Glass cleaning procedures, defect inspection;
- Case studies: Antireflective coatings, hydrophobic, antifog and smudge-resistant coatings, hard optical coatings on glass, and ion-induced interface broadening.
Metal Substrates
-
- Nature of as-received metal or hard ceramic substrates – near-surface structure and composition, contaminants, surface roughness (statistical parameters);
- Surface preparation: polishing, wet chemical cleaning, plasma cleaning including ion or bias cleaning, ion mixing and ion implantation, surface hardening, surface inspection approaches, adhesion testing;
- Case studies – designing the interface: Interlayers (adhesion-promoting layers), graded and duplex structures; effect of surface preparation on residual stress depth profiles, effect of surface roughness on wear, corrosion and tribo-corrosion.
Wrap-up, Discussion and Sharing Experience
-
- Recap: interface design = the “foundation” of a successful coating
- Share your specific problem – discussion
Instructor
Ludvik Martinu
Professor, Department of Engineering and Physics
Polytechnique Montreal
