Nanocoatings andNanofilms

Coatings have been used forcenturies

Coating Uses

UsesOptical propertiesNo light scattering, color can be selected

Adaptable refractive index (light curing adhesives)

Photocatalysis, UV/IR protection with absorbing NP

Electrical propertiesElectrical conductive but transparent coatings

Printable electronics

Magnetic propertiesTemperature increase in magnetic field (bond/disbond control)

Thermo mechanical propertiesScratch, anti/abrasion resistance

Anti friction, corrosion protection

Hydrophobic coatings

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Surface Coatings

Functional Coatings

* Functional coatings, tailored to all types ofrequirements are being developed with the applicationof chemical nanotechnology. This facilitates completelynew product properties, which can be used for anyindustrial application. "Intelligent", environmentallyfriendly and cost effective solutions are aimed atsecuring competitive advantages.* At present nanogate is "on top" in three hi techapplication areas: permanent non stick coatings onglass, ceramics, metals or polymers, non scratchsystems for plastics and anti corrosion systems for lightmetals.

Wood Preservative

* The water droplets rest on the impregnated woodsurface like mysterious blue pearls. But this is noconjuring trick: the wood has been treated with aBASFs nanoparticular surface coating , which has madeits surface extremely water repellent(superhydrophobic). This coating reduces the contactarea between water and wood to a minimum. It alsodecreases the forces of adhesion, making the waterdroplets assume a globular form. Surfaces becomeself cleaning and stay clean for a long time by applyingnanostructures as they can be found on the leaves ofthe lotus plant.

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One Step Paint

• Nanophase's proprietary nanoparticles are nowbeing used in Behr's Premium Plus Ultra paint.Nanophase's nanoparticles not only lend thepaint improved adhesion and anti mildewproperties, but also allow users to forgo thenormal two step priming and coating process.The new paint reportedly does both in a singlestep.

Anti Graffiti Paint

* Deletum 5000's special ingredient is silica. It is loadedwith particles of the stuff that are but a few nanometersacross. These particles have both oil repellent and waterrepellent molecules attached to their surfaces. Both arenecessary, since the materials used by graffiti artists maybe oil based or water based. However, if merely mixedtogether, the two would end up repelling each other, andthus separating. By attaching them to the silica, this mutualloathing can be overcome and, as the paint dries, thechanges that take place force the oil and water proofing tothe surface. The result is that most agents used will notstick to that surface—and what does stick can be washedor brushed off easily.

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Environmentally Safe Epoxy

* Advanced Nano Coatings, Inc ("ANC") is a producer ofhigh performance, VOC compliant epoxy coatings.* ANC's products are based upon unique polymerchemistry combined with cutting edge Nano Technologies.* ANC'S utilization of these technologies produces multifunctional coating systems. These systems exhibit uniquequalities, which now allow a coating system to solve morethan one market need.* Applications for these products include wood, steel andconcrete protection, fire protection and retardency,insulation of building materials and many other structuralprotection applications.

Construction Coatings

* The implementation of Nanotechnologycomponents into wall and facade coatingscreated some products which architects andbuilding owners have been waiting for.* These high tech products make it possible, bysimply replacing conventional wall paints, toachieve better energy ratings for buildings,better indoor air quality and fewer allergyrelated illnesses.

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 potentialcoating/substrate problems

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Possible Coating Structure:

http://www.nanopool.biz/en/

Useful nano coating properties

Doing It!

Chemical andPhysical vapourdepositionCVD & PVD

Evaporation PVD

1. Resistance heating is used tovapourise the metal to be deposited(High T)

2. Vacuum used so little contaminationand collisions

1

2

“LINE OF SIGHT”No surface diffusionEverything sticks where it hits (physical processes only)Poor surface coverage“Line of sight”

SputteringThe poor coverage problem in thermal evaporation was solvedwhen sputtering emerged.

‘Knocking off’ of the metal atoms from the metalmaterial source by gas ions bombards the‘knocked off’ ions on to the wafer.

Collision between the metal ions and the gasmolecules produces more uniform coverage

No longer purely “line of sight”

This grants sputtering a better coverage ofdeposition than thermal evaporation.

Comparison1. Coverage Area

As mentioned, sputtering has a larger coverage area than thermal evaporation because of the nature of their distribution method. The vapoursused 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 otherhand, sputtering controls its rate through gas pressure, temperature, the potential difference between the material, which acts as the cathodeof 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 itsdeployment of metal layers up to one atomic layer per second. Whereas thermal injection can only control it to hundreds or thousands ofatomic 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 precisethermometers; 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.

Chemical Vapour Deposition(CVD)

The substrate is exposed to one or more volatile precursors,which react and/or decompose on the substrate surface to produce thedesired deposit.

Chemical Vapor Deposition

Advantages:high growth rates possible

can deposit materials which are hard to evaporate

good reproducibility

can grow epitaxial films

Can grow nanotubes

Disadvantageshigh temperatures

complex processes

toxic and corrosive gasses

PVDNo surface diffusion

Everything sticks where it hits (physicalprocesses only)

Poor surface coverage

“Line of sight”

CVD

Precursors diffuse on surface

Leads to more uniform coating

Example : Silicon dioxide

Common source gases includesilane and oxygen,dichlorosilane (SiCl2H2) and nitrous oxide (N2O), ortetraethylorthosilicate (TEOS; Si(OC2H5)4). The reactions are as follows:

Example : Silicon dioxideReactions:

SiH4 + O2 SiO2 + 2 H2

SiCl2H2 + 2 N2O SiO2 + 2 N2 + 2 HCl

Si(OC2H5)4 SiO2 + byproducts

Oxide may also be grown with impurities (alloying or "doping")

Metal CVD processes

Mo, Ta, Ti, Ni, and W are widely used.These metals can form useful silicides when deposited ontosilicon.

Mo, Ta and Ti are deposited by LPCVD, from theirpentachlorides.Ni, Mo, and W can be deposited at low temperatures fromtheir carbonyl precursors

In general, for an arbitrary metalM, the reaction is as follows:

2 MCl5 + 5 H2 2 M + 10 HCl

The usual source for tungsten is tungsten hexafluoride, which may bedeposited in two ways:

WF6 W + 3 F2WF6 + 3 H2 W + 6 HF

Testing

Some of the techniques used to measure thephysical properties of PVD/CVD coatings are:Calo tester: coating thickness testScratch tester: coating adhesion testPin on disc tester: wear and friction coefficienttestNano indentation.

Atomic layer deposition (ALD)Coat complex, 3 dimensional objects with precise, conformal layers

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

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

Atomic layer deposition (ALD)

Reaction A, the substrate surface is initiallycovered with hydroxyl (OH) groups. Thehydroxyl groups react with trimethyl aluminum(TMA) to deposit a monolayer of aluminummethyl groups and give off methane (CH4) as abyproduct.

Because TMA is inert to the methyl terminatedsurface, further exposure to TMA yields no additionalgrowth beyond one monolayer.

Atomic layer deposition (ALD)

Reaction B, this new surface is exposed towater regenerating the initial hydroxylterminated surface and again releasingmethane. The net effect of one AB cycle is todeposit one monolayer of Al2O3 on the surface.

Case Study:Development of High Performance“Nanostructured” Ternary NitrideCoatings, and Assessment andModelling of Their Performance

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Strategy: Formation of Nanostructured CoatingsTo Increase Nucleation for Grain Refinement byincreasing the number and energies ofatoms/molecules arriving the substrate

Control Parameters:Bias Voltage

Substrate Temperature

Magnetron Configuration

Nitrogen Deposition Pressure

Magnetron Discharge Power

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Varian Deposition Chamber

37

Coatings were deposited in a Varian 3120 deposition unit

Pirrani gauges and Tylanmass flow controllers were used to monitor pressures and flow rates of reactive gas

Coatings with multiple-layers of Ti/TiAl/TiAlN or Cr/CrAl/CrAlN were produced

Ternary nitride coatings with nanograin size were produced by magnetron co-sputter deposition

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Experimental DetailsProcess Flowchart:

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Effect of Bias Voltage: Case Study TiAlNEffect of substrate bias voltage on elemental composition of thecoatingsNitrogen content almost unchanged

Titanium and aluminium contents slightly changed

40

0 100 200

25

30

35

40

45

Titanium Aluminium Nitrogen

Elem

enta

l Com

posi

tion

(at%

)

Substrate Bias Voltage (-Volts)

Effect of Bias Voltage: TiAlNMicrographs showing surface morphology of coatings producedat 100V, (a) SEM and (b) AFM images

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Effect of Nitrogen Pressure: TiAlNA schematic diagram of the two dimensional structure zone model showingthe effect of nitrogen pressure on the microstructure and morphology of(Ti,Al)N coatings can be established

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Coating Structures

Nitrogen Pressure: 0.2 mTorr

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Coating StructuresNitrogen Pressure: 0.65 mTorr

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Coating StructuresCross sections

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Grain Size DevelopmentGrain size: ~90 nm at 0.2 mTorr; 170 nm at 2.4 mTorr

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0.0 0.5 1.0 1.5 2.0 2.5 3.06080

100120140160180200

Gra

in C

olum

nar D

iam

eter

(nm

)

Nitrogen Pressure (mTorr)

Coating Compositions

As nitrogen pressure increased, nitrogen & titaniumcontents increased, aluminium content decreased

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0.0 0.5 1.0 1.5 2.0 2.5 3.015

20

25

30

35

40

45

Titanium Aluminium Nitrogen

Elem

enta

l Com

posi

tion

(at%

)

Nitrogen Pressure (mTorr)

Phase DevelopmentAs nitrogen pressure increased, TiN/TiAlN (200) and AlN (101)components were weakened; TiN/TiAlN (111) componentsdeveloped

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36 38 40 42 44 460

500

1000

1500

2000

2500

3000

3500(200)(101)(111)

0.2 mTorr

0.4 mTorr

0.65 mTorr

1.5 mTorr

0.5 mTorr

2.4 mTorr

2 Theta (Degrees)

Inte

nsity

(Arb

itary

Cou

nts)

Coating Hardness

Coating Hardness: ~2100 HV at 0.2 mTorr; 1000 HV at 2.4 mTorr

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0.0 0.5 1.0 1.5 2.0 2.5 3.0800

1200

1600

2000

Mic

roha

rdne

ss (H

V)

Nitrogen Pressure (mTorr)

Nanoindentation PropertiesNanoindentation load displacement curves of (Ti,Al)Ncoatings

50

0 40 80 120 160 2000

2

4

6

8

10

0.4 mTorr 0.96 mTorr

(Ti,Al)N

Load

(mN

)

Displacement (nm)

Nanoindentation Properties

Mechanical properties of the coatings determined by nanoindentation

Nitrogen Pressure (mTorr)

0.40 0.96

Hardness, H (GPa)(Approximate Hardness Value, HV)

18.6(1711)

13.6(1251)

Elastic Modulus, E (GPa)

264 196

Plasticity Parameter,

H = p/0.53 0.51

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Coating on Drills

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Sol Gel

limitations

Spin coating

Dip Coating

SiO2 coated with AlOOH

Corrosion Protection

Fracture Toughness ofNanoscale HydroxyapatiteCoatings on TitaniumSubstrates

R. ROEST1, G. HENESS1*, BB LATELLA2 AND B.BEN NISSAN11 UNIVERS ITY OF TECHNOLOGY, SYDNEY, PO BOX 123 BROADWAY,NSW, 2007, AUSTRAL IA2. MATERIALS DIV IS ION, ANSTO, PMB1, MENAI , NSW, 2560,AUSTRAL IA

The MaterialThe titanium samples, commercially pure(CP), were anodised in a mixed H3PO4H2SO4 solution. Three voltages were used,25 volts,50 volts and75 volts

•These voltages were based on the work of previous workers.

The anodization of the titaniumsamples produced

Oxide film thicknesses showing a linear growth of 2nmper volt.Anodised layers thus varied from 50 150nm

dilute anodizing solutiona more porous oxide film

concentrated anodizing solutionrelatively porosity free. at all voltages

Material system in this study

Ti

Anodised TiO2 layer

HAp layer

Anodised TiO2 layer

HAp layer

Ti

Phosphate layer

70 100nm

50 150nm

Sol gel coating flow chart HydroxyapatiteSol-Gel Coating

Process forTitanium

Polish Samples to0.3 micron Finish

Ultrasonic Cleanerwith M.E.K

Anodize (Dilute)25V, 50V, 75V for

30 Minutes

Anodize (Conc)25V, 50V, 75V for

30 Minutes

Rinse DistilledWater (90 -100C)

Coat HApSpincoater2000 RPM

for 20 Seconds

Age Coating70C for 24Hrs

Heat treat300C for 24 Hrs

Heat treat550C for 2 Hrs

Low sinteringtemperature.Avoids phase changein Ti

Specimen Shape and Size

26

12

33

3

3.5R

10

4 dia

All dimension in mm

Test Apparatus

Test Apparatus

30mm

XRD patterns for the three HApcoated films.

75V

50V

25V

TiTi

Ti

HAp

Uniform HAp coating

1 m 10 m

0

0.5

1

1.5

2

2.5

3

Inte

rfac

al F

ract

ure

Ener

gy J

/m2

Anodised

Anodised + Phosphated

25CP 7550

Anodising Voltage (V)

Effect of anodising & phosphating on theinterfacial fracture energy

33%

75%

25V0V

50V

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75V

10 m 10 m

10 m10 m

0.2.4.6.81.2.4.6.8

Anodised

Anodised + Pho

25CP 7550

WHAT IF?…you could have a fish tank which is self cleaning?

WHAT IF?…you could see what was in the fridge without opening it?

HYDROPHILIC = WATER LOVING

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

Hydrophilic surface=wetting

Water spreads

HYDROPHOBIC = WATER HATING

When water hits a hydrophobic surface, it beads.

Hydrophobic surface= beading

Water beads

WETTING & BEADING

Contact angles below 90 indicate good wetting, while contact angles above 90 indicate poor wetting (beading).

Poor wetting (beading)Contact angle > 90

Good wetting Contact angle < 90

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”

Ultra Ever Dry

http://www.spillcontainment.com/everdry

SELF CLEANING GLASSScientists have mimicked nature at the nanoscale to create glass surfaces that are ‘self-cleaning’ like the Lotus leaf.

No more scrubbing of shower screens!

Self cleaning glass Normal glass

No more Spiderman window cleaner!

SELF CLEANING GLASSHOW DOES IT WORK?

Glass is coated with a layer of nanocrystalline titanium dioxide (TiO2).The titanium dioxide reacts to the ultraviolet (UV) component of sunlight causing a gradual break down and loosening of dirt.

This isknown as the ‘photocatalytic’ stage.

SELF CLEANING GLASSHOW DOES IT WORK?

The reaction also causes the glass surface to become super hydrophilic. This forces water to spread across the surface like a sheet, rather than beading, thereby washing away the looseneddebris on the surface of the glass as it falls.

This is the ‘hydrophilic’stage.

Photocatalytic TiO2Nanoparticles

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.

SELF CLEANING GLASSHOW DOES IT WORK?Another type of self cleaning glass uses hydrophobicity, not hydrophilicity.

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

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

Optical nanocoatings

Thin films are used commercially in anti reflection coatings, mirrors, andoptical filters.

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

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

Manufacture of coatings

apply by physical vapour deposition (PVD)

chemical vapour deposition (CVD)

magnetron sputtering

thermal evaporation

need for a vacuum chamber

multiple layers

Application areas

coatings on windowsspectacles and sun glassesnarrowband filters for opticslenses and optical elementsdecorativeelectron conduction plus transmissionpolarization controldichroic beam splitterscold mirrors (transmit IR, reflect visible)

Antireflective CoatingsEliminates reflected light and maximizestransmitted light

A film is designed such that reflected lightproduces destructive interference andtransmitted light produces constructiveinterference for a given wavelength oflight.

dncoating is a quarter wavelength of theincident light and its refractive index isgreater than the index of air and less thanthe index of glass.

nair < ncoating < nglass

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

GLASS NANO-COATINGSANTI-REFLECTIVE GLASSType 1

Glass, is coated with multiple layers of metal oxides such as TiO2 which have a high refractive index, meaning 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.

Reflection and interference

Reflection and interference

ncoating <nsubstrateIf m = 1

Destructive interference for

d= ¼ n

“¼ wavelength coating”

GLASS NANO-COATINGSANTI-REFLECTIVE GLASS

Type 2

Another method of producing anti-reflective glass is to coat it with a single layer of nanoporous SiO2.The refractive index of the porous coating is between that of the glass surface and air, 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 atCoca 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 andfilms\BBC News'Walkie Talkie'skyscraper meltsJaguar car parts.htm

One structure

Doing calculations

• e.g. OpenFilters, by S. Larouche

• www.polymtl.ca/larfis

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

SWITCHABLE GLASSSwitchable glass has applications in car sun roofs, office buildings, and residential apartments.

Skydeck 88 in the Eureka Tower in Melbourne is the only observation deck in the world that can thrill you with 'The Edge' - a glass cube made of switchable glass, which projects 3 metres out from the building and suspended almost 300 metres above the ground, with you in it!

OTHER NANO APPLICATIONS

SWITCHABLE GLASS

Nano Particles in Coatings:Challenges

Dispersion and Dispersant Demand

Rheology

FunctionalizationApplication Specific?

Characterization

Cost/Performance Balance

Health EffectsNanosafe2.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