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Nanocoatings and NanofilmsA COATING OR FILM WHOSE THICKNESS IS MEASURED IN THE NANOSCALE

Coatings have been used for centuries

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Application areas

coatings on windows

spectacles and sun glasses

narrowband filters for optics

lenses and optical elements

decorativeelectron conduction plus transmission

polarization control

dichroic beam splitters

cold mirrors (transmit IR, reflect 

visible)

Uses

Optical properties 

No light scattering, colour can be selected 

Adaptable refractive index (light curing adhesives) 

Photocatalysis, UV/IR protection with absorbing NP

Electrical properties 

Electrical conductive but transparent coatings 

Printable electronics 

Magnetic properties 

Temperature increase in magnetic field (bond/disbondcontrol) 

Thermo‐mechanical properties 

Scratch, anti/abrasion resistance 

Anti‐friction, corrosion protection 

Hydrophobic coatings 

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Market Growth of Thin Film Enabled Technologies Nanofilms in Cars (at least Audi!)

Surface coatings

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Functional Coatings

Permanent non‐stick coatings on glass, ceramics, metals or polymers, non‐scratch systems for plastics and anti‐corrosion systems for light metals.

Wood Preservative

*  This coating reduces the contact area between water and wood to a minimum. It also decreases the forces of adhesion. Surfaces become self‐cleaning and stay clean for a long time by applying nanostructures as they can be found on the leaves of the lotus plant.

One Step Paint

•Nnanoparticles not only lend the paint improved adhesion and anti‐mildew properties, no two‐step priming and coating process.

Anti‐Graffiti Paint

*  Nano silica particles have both oil‐repellent and water‐repellent molecules attached to their surfaces.. The result is that most agents used will not stick to that surface—and what does stick can be washed or brushed off easily.

Environmentally Safe Epoxy

*   Applications for these products include wood, steel and concrete protection, fire protection and retardency, insulation of building materials and many other structural protection applications.

Construction Coatings

*  These high‐tech products make it possible, by simply replacing conventional wall paints, to achieve better energy ratings for buildings, better indoor air quality and fewer allergy‐related illnesses.

Nano Smart Coatings™ Characteristics

Smart Coatings ™ Functions:

Preserve items from corrosion

Incorporate nanomachines

Self‐heal

Permit easy removal when giventhe proper “orders”

Protect items from harsh environmentsendured because of mission requirements

Alert sustainment community of potential coating/substrate problems

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Non‐chromate inhibitor

TBD

Sensing

Nanocrystalline cladding

Substrate

Possible Coating Structure:

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Putting Coatings on Things

Application by Vapour

CVD/PVD Comparison

1. Coverage Area

As mentioned, sputtering has a larger coverage area than thermal evaporation because of the nature of their distribution method. The vapours used in thermal evaporation are directional; while the ion bombardment of the sputtering is ‘rain‐like’.

2. Deposition Rate Control Factors

In thermal evaporation, deposition rate can be controlled by the amount of heat supplied on the material (vaporization point). On the other hand, sputtering controls its rate through gas pressure, temperature, the potential difference between the material, which acts as the cathode of system and the wafers placed on the system’s anode.

3. Deposition Rate

When talking about deposition rate, the more controlled the rate is (lower number of layers/second), the better. Sputtering can trim down its deployment of metal layers up to one atomic layer per second. Whereas thermal injection can only control it to hundreds or thousands of atomic layers per second.

4. Choice of Material

Sputtering has a wider range of choices for material than thermal evaporation.

5. Decomposition of Material

The uniformity of decomposition and erosion of the material in sputtering makes it more efficient than thermal evaporation.

6. Equipment Cost

Operating using sputtering will cost more than thermal evaporation because the latter only needs a vacuum chamber with precise thermometers; while the former requires twice or thrice of the energy used in thermal deposition to excite the ion of the material.

7. Surface Damage

Surface damage has higher possibility in sputtering. Its ion particle bombardment can induce damage in the substrate.

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ALDAtomic layer deposition (ALD)

ALD uses alternating, saturating reactions between gaseous precursor molecules and a substrate to deposit films in a layer‐by‐layer fashion. 

By repeating this reaction sequence in an ABAB… fashion, films of virtually any thickness, from atomic monolayers to micrometer dimensions, can be deposited with atomic layer precision.

Atomic layer deposition (ALD)Reaction A

Atomic layer deposition (ALD)Reaction B, 

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Application by Solution

Aerosol Coatings

Properties & Benefits• Atmospheric coating• Sub micron liquid precursor atomization• Large area off‐line and continuous in‐line coating• Thin films (nAERO® ) and surface doping (nHALO ® )

Source: Beneq

nFOG Spray Deposition Aerosol Coating

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Sol Gel

How are they used?

Transparent Conductive Oxides (TCO’s)

They are an important component in a number of electronic devices including liquid-crystal displays, OLEDs, touchscreens and photovoltaics

Increased efficiency c‐Si solar cells

1 percentage point better cell efficiency

e.g., from 18 to 19 %

10 nm of Al2O3

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Increased efficiency CIGS solar cells

1 percentage point better cell efficiency

No cadmium in the cell\

C = CopperI = Indium G = GalliumS = Diselenide

ZnO:AlALD‐ZnOSCIGS

Mo

Glass

WHAT IF?…WE COULD  HAVE  WINDOWS THAT  ARE  SELF  CLEANING?

WHAT IF?…YOU  COU LD   S E E  WHAT  WAS   I N   T H E   F R I DGE  W I T HOUT  O P EN I NG   I T ?

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WHAT IF?…YOU COULD  HAVE  A  F I SH  TANK  WHICH   I S     SELF  CLEANING?

Self cleaning glass

Based on hydrophobicity

Based on hydrophilicity

HYDROPHOBIC

When water hits a hydrophobic surface, it beads.

HYDROPHILIC

When water hits a hydrophilic surface, it flattens and spreads out to form a thin sheet.

WETTING & BEADING

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Ultra Ever Dry

http://www.spillcontainment.com/everdry THE LOTUS LEAF EFFECT

The leaves of Lotus plants have the unique ability to avoid getting dirty.They are coated with wax crystals around 1 nanometre in diameter and have a special rough surface.

Droplets falling onto the leaves form beads and roll off taking dirt with them, meaning the leaves are self-cleaning.

Sometimes referred to as

“The Lotus Leaf Effect”

HydrophobicityMimmick nature at the nanoscale to create glass surfaces that are ‘self-cleaning’ like the Lotus leaf.

Self cleaning glass

Normal glass

No more scrubbing of shower screens!

No more Spiderman window cleaner! Hydrophobic Self 

Cleaning GlassThis type of glass is given a coating which makes it super hydrophobic, meaning water forms beads and runs of the glass.

Good for indoors, such as in shower screens, where there is no sunlight enable use of the other type of glass.

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Hydrophilicity

Hydrophilic Self Cleaning Glass

Nanocrystalline TiO2

Reacts with UV causing a gradual breakdown and loosening of dirt

PHOTOCATALYTIC STAGE

Hydrophilic Self Cleaning Glass

Causes surface to become hydrophilic

Water spreads across surface like a sheet rather than beading

washing away the looseneddebris on the surface of the glass

HYDROPHILIC STAGE

SO CAN A FISH TANK BE SELF-CLEANING?

Australian company Diamond Shell has made self cleaning aquarium glass called ‘Barracouta Glass’ based on the photocatalytic and hydrophilic process.

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Optical nanocoatings

Thin films are used commercially in anti‐reflection coatings, mirrors, and optical filters. 

They can be engineered to control the amount of light reflected or transmitted at a surface for a given wavelength. 

Takes advantage of thin film interference to selectively choose which wavelengths of light are allowed to transmit through the device

Anti‐reflective Glass

multiple layers of metal oxides’ such as TiO2’ which have a high refractive index

coat with a single layer of nanoporous SiO2.

Antireflective CoatingsEliminates reflected light and maximizes transmitted light

Reflected light produces destructive interference and 

transmitted light produces constructive interference for a given wavelength of light.◦ dncoating is a quarter‐wavelength of the incident light and its refractive index is greater than the index of air and less than the index of glass.

nair < ncoating < nglass

d = λ / (4ncoating) OptiView Anti-reflective glass made by Australian company Pilkington

High RI Coatings

Light passes through them very quickly.

The thickness of the layers is related to the wavelength of light, resulting in destructive interference of light reflected off the surfaces, making the glass non‐reflective.

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Reflection and interferencencoating <nsubstrateIf m = 1

Destructive interference for 

d= ¼ n

“¼ wavelength coating”

Porous coatingsnsurface > n porous coating > nair

Thereby reducing the reflectivity and increasing the transmission of light at the glass surface.

What about heat?Cutting out infrared Umisol installs Infrared 

Blocking window filters at Coca‐Cola

Cost: €99k

Saving p.a. : €14/m2/year

Area: 510 windows x 1.66m2

= €11.9k

Oh Dear!Reflect the heat (IR), right?

08 Nanocoatings and films\BBC News ‐ 'Walkie‐Talkie' skyscraper melts Jaguar car parts.htm

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Low‐emissivity (Low‐E) is a thin film deposited on glass that reduces the U‐value by suppressing radiative heat flow, which is the principal mechanism of heat transfer in multilayer glazing.

Low‐e reflects a significant amount of this radiant heat (IR energy), thus lowering the total heat flow through the window.

Image courtesy of www.welshwindows.co.uk

The U-value of a window is a measurement of the rate of heat loss indicating how well your windows are keeping valuable heat in. It is expressed as Watts per square metre Kelvin W/m2 K. The lower the U-value the better the thermal performance of the glass

Nano films

40% better insulationno effect on transparencyno effect on appearance

30% better insulationno effect on appearanceno effect on transparency

Ref.: PPG Industries Inc.

Doing calculations

• e.g. OpenFilters, by S. Larouche

• www.polymtl.ca/larfis

http://larfis.polymtl.ca/index.php/en/links/openfilters

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While we are talking about glass, other nano applications

SWITCHABLE GLASS

Nano‐Particles in Coatings:

Challenges

Dispersion and Dispersant Demand

Rheology

Functionalization◦ Application Specific?

Characterization

Cost/Performance Balance

Health Effects◦ Nanosafe2.org◦ “Nanoparticles: health impacts?”, David Warheit(DuPont), Materials Today, Feb. 2004, p32

◦ “Nanoscience and nanotechnologies: opportunities and uncertainties”,

◦ http://www.nanotec.org.uk/finalReport.htm, July 2004 Testing

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Some of the techniques used to measure the physical properties of PVD/CVD coatings are:

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Calo tester: coating thickness test

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Scratch tester: coating adhesion test

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Pin on disc tester: wear and friction coefficient test

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Nano‐indentation.

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