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Nanocoatings
Noraiham Mohamad, PhD
Faculty of Manufacturing Engineering,
Universiti Teknikal Malaysia Melaka
What is coating?
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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.
Coating
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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
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.)
Inorganic Coating
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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, dimerized silanes, silane hydrozylates, silaceous
materials, leveling agents, 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.
Inorganic Coating
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Polysiloxane coatings are applicable to many
substrates, but the majority of applications are on
nonmetallic surfaces, 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.
Inorganic Coating
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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.
Organic Coating
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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.
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.
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:
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Decorative Coating
Functional coating
Self-Assembled Nanophase Coating
Functional coating
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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:
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self-cleaning
easy-to clean (anti-graffiti)
antifouling
soft feel
antibacterial
Functional coating
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expectations of functional
coatings include:
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durability
reproducibility
easy application and cost effectiveness
tailored surface morphology
environmental friendliness
Functional coating
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Functional coatings perform by means of
physical, chemical, mechanical, thermal and
properties.
Chemically active functional coatings
perform their activities either at
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film–substrate interfaces (anticorrosive
coatings),
in the bulk of the film (fire-retardant or
intumescent coatings), or
at air–film interfaces (antibacterial, selfcleaning)
Coating Techniques
Processing for Inorganic
Coating & Hard Coating
Processing for Organic
Coating
Sol-Gel Coating (Organic or
Inorganic)
Nanoparticles in Sol-Gel
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Possible to increase the coating thickness, without
increasing the sintering temperature.
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Eg. Electrophoreticdeposition of commercial SiO
sol on AISI 304 stainless steel substrates leads to
coatings as thick as 5 mm with good corrosion
resistance
Incorporation of 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
pretreatments with controlled release properties
Example of Nanoparticles in
Sol-Gel
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Studies showed that sol–gel films containing
zirconia nanoparticles present improved barrier
properties.
Doping this hybrid nanostructured sol–gel coating
with cerium nitrate brings additional improvement
to corrosion protection.
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Zirconia particles present 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
Coating Applications