Nanocoatings

1. Nanocoatings NoraihamMohamad, PhD Faculty of Manufacturing Engineering, UniversitiTeknikal Malaysia Melaka

3. What is coating? • A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. • In many cases coatings are applied to improve surface properties of the substrate, such as appearance, adhesion, wettability, corrosion resistance, wear resistance, and scratch resistance. • In other cases, in particular in printing processes and semiconductor device fabrication (where the substrate is a wafer), the coating forms an essential part of the finished product.

4. Coating • Coatings are usually applied as multi-layered systems that are composed of primer and topcoat. However, in some cases – for example automotive coating systems, this may vary from four to six layers. • Each coating layer is applied to perform certain specific functions, though its activities are influenced by the other layers in the system. • The interactions among different layers and the interfacial phenomenon play an important role in the overall performance of the multi-coat systems

5. Type of coating • Inorganic Coating- Coating with silicate based materials (eg.- zinc silicate based coating) or metal/ceramic based coating (hard coating of Chromium, TiN, Si3N4, alumina etc.) • Organic Coating- Coating with organic binders (organic based materials- eg. Zinc epoxy based coating, zinc rich phenoxy, etc.)

6. Inorganic Coating • Silicone (polysiloxane) hard coatings are finishes of superior abrasion resistance and inertness to hostile chemical and environmental conditions. • They consist of several monomers and other ingredients, and the makeup of the formulations varies from manufacturer to manufacturer. • Among the highly varied components are monomeric silanes, dimerizedsilanes, silanehydrozylates, silaceous materials, levelingagents, flow control agents, cross-linking agents, and catalysts of various types. • Silicone coatings are solvent-borne coatings. Some of the possible solvents are alcohols and glycol ethers. This includes such alcohols as isopropanol, propanol, ethanol, n-butanol, isobutanol, and methanol.

7. Inorganic Coating • Polysiloxane coatings are applicable to many substrates, but the majority of applications are on nonmetallicsurfaces, especially plastics. • Silicone coatings can be dyed or pigmented, but for the most part these coatings are used as clear top coatings. • They have excellent light transmission and actually improve the optical properties of the material that is coated. • Some of the plastics that are used with polysiloxane coatings are polycarbonate, acrylic, polyarylate, polysulfone, vinyls, nylons, polyester, cellulose acetate, cellulose acetate-butyrate, and polyolefins, etc.

8. Inorganic Coating • Hard silicone coatings are useful as antifog, antistatic photochromic, color-dyed, pigmented, UV absorbing, UV stabilized for exterior exposure, chemical resistance, 5-min curing, and tinted coatings. • Many of these properties can be combined in one coating. • The coatings are used in such diverse areas as the automotive, electronic, computer hardware, architectural and architectural glazing, recreation, sporting goods, protective eyewear, safety, and optical industries.

9. Organic Coating • Organic coatings are essentially pigment dispersed in a solution of a binding medium. • Binding medium or resin - decide the basic physical and chemical properties of the coating but these will be modified by the nature and proportion of pigments present. • Sole function of volatile component -to control the viscosity of the paint for ease of manufacture and for subsequent application. • Not possible to forecast -what combination of properties a particular formulation will possess and the formulation of paints for specific purpose remain very much a technological art.

10. Nanomaterials in Coating • The appearance and appliance of nanomaterials brings new opportunities to the coating industry. • Addition of nano-materials to the coatings improves the properties of the conventional coatings and produces new multi-functional coating due to their tiny particle size.

11. Category of Coating • Coatings are mainly applied on surfaces for decorative, protective or functional purposes, but in most cases it is a combination of these. • 3 category: • Decorative Coating • Functional coating • Self-Assembled Nanophase Coating

12. Functional coating • Functional coatings- systems which possess, besides the classical properties of a coating (i.e., decoration and protection), an additional functionality • This additional functionality may be diverse, and depend upon the actual application of a coated substrate. • Typical examples of functional coatings are: • self-cleaning • easy-to clean (anti-graffiti) • antifouling • soft feel • antibacterial

13. Functional coating • Typical expectations of functional coatings include: • durability • reproducibility • easy application and cost effectiveness • tailored surface morphology • environmental friendliness

14. Functional coating • Functional coatings perform by means of physical, chemical, mechanical, thermal and properties. • Chemically active functional coatings perform their activities either at • film–substrate interfaces (anticorrosive coatings), • in the bulk of the film (fire-retardant or intumescent coatings), or • at air–film interfaces (antibacterial, self-cleaning)

15. Coating Techniques

18. Processing for Inorganic Coating & Hard Coating

28. Processing for Organic Coating

31. Sol-Gel Coating (Organic or Inorganic)

38. Nanoparticles in Sol-Gel • Possible to increase the coating thickness, without increasing the sintering temperature. • Eg. Electrophoreticdepositionof commercial SiOsol on AISI 304 stainless steel substrates leads to coatings as thick as 5 mm with good corrosion resistance • Incorporationof nanoparticles in the hybrid sol–gel systems increases the corrosion protection properties due to lower porosity and lower cracking potential • Can be a way to insert corrosion inhibitors, preparing inhibitor nano reservoirs for self repairing pretreatmentswithcontrolledrelease properties

39. Example of Nanoparticles in Sol-Gel • Studies showed that sol–gel films containing zirconia nanoparticles present improved barrier properties. • Dopingthis hybrid nanostructured sol–gel coating with cerium nitrate brings additional improvement to corrosion protection. • Zirconiaparticlespresent in the sol–gel matrix act as nano reservoirs providing a prolonged release of the cerium ions • The recent discovery of a method of forming functionalized silica nanoparticles in situ in an aqueous sol–gel process, and then cross linking the nanoparticles to form a thin film

40. Coating Applications