coatings - unipd.it · pdf filepreparation of lead zirconate titanate ... bressanone sept....

1

Bressanone Sept. 2006 Coatings 1

Coatings


• Requirements to the coating material (chemical composition, purity, crystallinity, materials properties)

• Thermal stability of the substrate material• Adhesion of the coating under certain conditions

(temperature, humidity, sunlight, etc.)• Throughput• Costs for investments, running costs• Environmental aspects

Choice of a Suitable Coating Method

2


• non-oxidic materials can also be deposited

• larger variety of precursors

• simple coating techniques

• low thermal stress of the substrat

• better control of film growth• generation of complex micro- and nanostructures (incl. porosity) possible

• epitactic growth and selective deposition possible

• preparation of inorganic-organic hybrid materials possible

• no shrinkage during annealing• many processing options

CVDSol-Gel Processing

Comparison Sol-Gel Processing / CVD


Solid state reaction Sol-gel processing

PbO + TiO2 + ZrO2 Pb(OAc)2 · 3 H2O + Ti(OPr)4 +

Zr(OPr)4 + acetylacetone

PZT Sol

Pb(Zr0.53Ti0.47)O3

750 - 1100 °Cseveral h

700 °C / 2 min

Preparation of Lead Zirconate Titanate (PZT) – A Comparison

3


Xerogel Film

Powders

Dense Ceramic Film

Heat

Sol

GelationEvaporation

Gel

SolventEvaporation

Supercritical Extraction

Xerogel Aerogel

Dense Glass

Dry Heat

Materials costs no big issueShinkage can be controlled (< ca. 5 μm)

Sol-Gel Processing Scheme


Precursors Metal AlkoxidesMetal Salts

Sol

Wet film

+ water (ev. catalyst or additives)- alcohol

HydrolysisCondensation

Coating

substrateCoating

Drying,Hardening (thermal or uv)

Application of Sol-Gel Coatings

4


Coating materials

inorganic (ceramic materials)inorganic-organic hybrid materialsnanoparticles

Variation of the film properties

Chemical compositionPorosityMicro-/Nanostructure (texture)

Coating techniques

DippingSprayingDoctor bladingPaintingRollingFlow coating…..

Curing methods

ThermalPhotochemical

Which materialscan be coated

GlassesCeramicsMetalsPolymers


Application of thecoating solution

Spreading of the film Solvent evaporation

Spray coating

Spin coating

Coating Techniques

5


Industrial dip coating plant(up to 1.15 x 1.60 m2)(Prinz Optics GmbH)

Dip coating

Flow coating

Dipping Coating of Solventthe substrat evaporation

Coating Techniques


O(RO)3SiO

Formation of a dual inorganic-organic network

(ButO)3Al Hardness

Reduction of brittleness(MeO)3SiCH2CH2CH3

Sol

Addition of solvents (alcohol) and lacquer additives

Scratch-resistant and corrosion-protecting coating for brass

1) Conventional coating techniques2) Curing (130°C, 45 min)

An example for a deliberate tailoring of the materials properties

Tailoring of Sol-Gel Coatings

6


Crackability• stresses develop during drying due to shrinkage• thermal expansion mismatches• plastic deformation of substrate

Thickness limits(Thick films required for thermal barriers, and abrasion and wear protection)

Reasons:Cracks develop during drying more likely in thicker films

Possible solutions:• multilayer deposition• use of fillers to reduce shrinkage

Limits of Sol-Gel Coatings


Protection of sensitive surfacesScratch- and abrasion-resistant coatingsImprovement of wear

Coatings with optical propertiesCoatings with barrier propertiesModification of surface polarityElectroactive layersSensor layers

7


polycarbonate disk with scratch-resistant coating

Scratch-resistant coatings for polycarbonate lenses

Most successful material for optical lenses: CR39® (PPG Industries). nD 1.498, Abbé number 59, density 1.31 g/cm3, luminous transmittance 91%.

Rupp & Hubrach

High scratch and abrasion resistance due to the formation of titanium oxo clusters and high degree of organic crosslinking (polymerization of the epoxy groups)

Scratch-resistant coating:1. Sol-gel processing of Si(OMe)4, Ti(OEt)4 and

2. Spin coating on CR39 lenses3. Thermal curing at 110°C for several h

O(RO)3SiO

Surface Protection


Subsequent improvements of scratch resistant coatings on polycarbonate

by replacement of Ti(OEt)4 for Zr(OR)4 or Al(OR)3, or by addition of boehmite (AlOOH) nanoparticles

Increase of haze during abrasive treatment (Tumble test): × noncoated CR39, + titanium containing coating, □ coating containing AlOOH nanoparticles.

Surface Protection

8


scratch-resistant and easy-to-clean coating for PMMA earmoulds

UV curable hard coatings

based on SHSiO

OO Si

O

OO+ SSi

O

OO

SiO

OO

magnifying PMMA lenses with scratch-resistant sol-gel coating

high throughput and short processing times

Increase of nD (1.49 to 1.52) by addition of 12 mol% methacrylate-substituted Zr(OPr)4

Surface Protection


Optical fibers coatings for protection against scratching

Tailoring the organic spacer between the inorganic species allows tailoring both the refractive index and Young’s modulus in a wide range

Me

MeO

X

X

X

X

O

OO

O

S(RO)2MeSi

X = Br or H

O

O

S(RO)2MeSiEt

O

O

O

O

Refractive Young’s index modulus

1.56 – 1.60 0 – 20 MPa

1.52 1400 MPa

Surface Protection

9


wear and hydrophobicity of coated and uncoated leather

Thin (≤ 4 μm) inorganic-organic hybrid coating:

• natural, optical and haptic properties are preserved• high hydrophobicity• high water vapour permeability and water vapor up-take• very good scratch resistancy and improved wear properties• good temperature- and light-proof

Wear-improving coating

Surface Protection


Protection of sensitive surfacesCoatings with optical properties

Decorative (colored) coatingsPhotochromic coatingsInterference layersAntireflective coatingsReflective coatingsOptoelectronic componentsPhotocatalysis

Coatings with barrier propertiesModification of surface polarityElectroactive layersSensor layers

10


• wide variety of colours• improved mechanical properties of the

glass• as easy to recycle as uncoloured glass• dishwasher-safe

Si(OMe)4 + Ti(OEt)4 + (EtO)3Si-CH=CH2 +addition of organic dyeUV and/or thermal curing

O(RO)3Si

ODecorative coatings

Research Laboratory for Packaging, Japan

Coatings with Optical Properties


Decorative coatings on glass


11


O NEt2+Et2N

SO3-

SO

ONH

Si(OEt)3

Wavelength-selective absorption films

to raise the color purity of luminiscence and improve contrast in high-performance cathode ray glass tubes

Rhodamine B is soluble in water and alcohols⇒ dye seeps out when film is wiped

⇒ chemical bonding of the dye to the SiO2 network



Photochromism: fast for optical switches, for eye protection, privacy shieldsslow for optical data storage, energy conserving coatings, etc...

Example: Spirooxazine derivative

Embedding in sol-gel coatings:For sufficient photochromism: dye concentration > 25 wt% → mechanical stability of sol-gel film is deteriorated.

Grafting of the dye to thesol-gel matrix → higher chromophoreconcentrations can be achievedwithout affecting the mechanical integrityof the sol-gel matrix

O

N

N

O

O

HN

Si(OEt)3

O

N

N O

N

N

hν1

Δ or hν2

Photochromic coating on paper


12


Requirementsimproved transmissionhigh band widthlow angle dependence

colorless residual reflexionhigh mechanical stability

Materials and microstructuresgradient layers (index)interference layers (λ/4 single layers)interference multiple layers (SiO2-TiO2)

AnwendungenArchitectural glass, displays, solar cells, optical components

Bildquelle:Fa. Schott AG

Antireflexion Layers on Glass


Material:

Band width:Angle

dependence:Residual

reflections:Mechanical.

stability:

porous, glassy

mediummedium

colored

low - good

dense, alternating refractive index

niedrighigh

colored

very good

dense, glassy, nano-structured (< λ/4)

highlow

colorless

good

λ/4 single layer

effectivenLuft = 1,00

nSchicht= 1,26

nGlas = 1,52

multilayers(interference)

Glas

SiOTiOSiO

2

2

2

gradient layerseffective:

Antireflexion Layers on Glass

13


Porous anti-reflection sol-gel coatings on glass

92%

100%

8%

nglass, glass

n0, air

n0, air

Uncoated glass

nglass, glass

nfilm, coating

n0, air

n0, air

100%

100% 0%

Coated glass

No reflexions for a given λ, if optical thickness = λ /4nfilm = √n0·nglass ≈ 1.22



Hydrolysis/Condensation

Si(OR)4(TMOS, TEOS)

EtOH, MeOHH2ONH3

Nanoporous SiO2 layerMERCK, FLABEGStöber particles

Thermal toughening (400-550°C ⇒ wipe-proof, weather-resistance porous SiO2 layer

Antireflective coating: Structuring by deposition of small particles


14


Interference Filter

Alternating SiO2 and TiO2 layers

Increasing withdrawal speed during dip coating:increasing film thickness (60 nm → 120 nm)change of optical propertiescolor effect filter


50 nm 80 nm


OO

OO

OSSi

OMe

OO

Structuring by embossing (gradient layers)

Antireflective coating1. Polysiloxane chains from

2. Embossing3. UV curing = fixing the imprinted structure


Optoelectronic components

15


Reflective coatings

SiO2 from Si(OEt)4; nD 1.22

substrate

210 nm SiO2

ZrO2 / PVP210 nm SiO2

ZrO2 / PVP....

15 nm ZrO2 particles (from ZrOCl2) in PVP binder (15 wt%); nD 1.70

20 layers SiO2 / ZrO2a: theoretical, b:experimental

Pohl Institute of Solid State Physics, Shanghai



buffer layer(lower refractive index)

photopatternable core layer(high refractive index) cladding

(lower refractive index)

Optical WaveguidesHybrid materials from Ph2Si(OH)2 and CH2=C(Me)OC(O)(CH2)3Si(OMe)3


16



TiO2 photocatalysis

UV irradiation (λ< 388 nm)promotes degradation of organic compounds alters the polarity of the surface („photoinduced super-hydrophilicity“)

Creation of porosity (high surface area) by embossing or by deposition of particles

SEM and AFM micrograph of a porous TiO2 sol-gel thin film



A TiO2-coated surface is rendered more hydrophilic by UV irradiation (right).

Anti-fogging

Self-cleaning

17


Protection of sensitive surfacesCoatings with optical propertiesCoatings with barrier properties

Corrosion protection (water and oxygen barriers)Barrier against diffusion of organic compounds

Modification of surface polarityElectroactive layersSensor layers


Uncoated Al pigments After sol-gel hybrid coating

Immediate reaction2Al + 6H2O 2Al(OH)3 + 3H2

☺ Neutral water test: <1ml H2 from 3gAl in 3 days

☺ Boiling test (time to react 50% of the Al in boiling water): 13h Not stable at pH 9

Al

SiO2

RSiO3/2

Corrosion Protection of Aluminum Pigment

Barrier Coatings

18


Coatings on Metals

Corrosion protectionAbrasion resistanceAdhesion promotion for paints

Barrier Coatings


Replacement of conversion coatings (especially chromating)

AIMg1 alloy

Top: wet coating system (poxyprimer and polyurethane top layer) after 1000 h ESS test.

Bottom: sol-gel inorganic-organic hybrid coating

CEA

Corrosion protection for aluminum sheets

Barrier Coatings

19


Corrosion protection of silver reflector in laser cavities• Protection against oxidation to preserve the high reflectivity • Protection against mechanical and chemical attack during handling, cleaning or weathering

10-50 nm dense, hydrophobic or hydrophilic films from Si(OEt)4 / RSi(OR)3 at pH 2. nD 1.445-1.449

CEA / Le Ripault

Specular reflectance variation with oxidative medium timeexposure

Barrier Coatings


1. One or two silanes with epoxy and methacrylate groups → adhesion to polymeric substrates, curing at low temperatures or by UV.

2. Tri- or tetraethoxysilane for high inorganic crosslinking → reduction of water vapor permeation, adhesion to metallic substrates.

3. Diorganosilane (e.g. Ph2Si(OH)2) → modification of Young’s modulus, improvement of dielectric properties, influence on hydrophobicity and solubility of water in the material.

days

rela

tive

capa

city

(%)

(I) uncoated, (iI) encapsulated, (IiI) ORMOCER-coated thin-film capacitor(95 °C/100 % rel. humidity)

Passivation layers in electronic devices

Barrier Coatings

20


food packaging foilspackaging of technical products

encapsulation of solar cells

flexible LCDs

100100

10-1 10-1

10-6

10-2

10-6

10-2

State-of-the art with ORMOCER® coatings

High- and ultra-barrier coatings

Requirements

oxygenpermeability[cm3/m2dbar]

water vaporpermeability

[g/m2d]

barrier properties

flexibleOLEDs

organicsolar cells

Barrier Coatings


3

3

7

1(MeO)3Si(CH2)3NMe3+ Cl-

1211N(CH2CH2OH)3

1CH2=C(Me)COOH

121Al(OsBu)3

11Zr(OPr)4

23444

Type 3Type 2

a b cType 1

a b

O(RO)3Si

O

Barrier layers on plastics

Barrier Coatings

21


PET

hybrid polymer

PET / SiOx / hybrid polymer / PET

I

Barrier layers on plasticsBarrier properties of the barrier systems produced by roll-to-roll processes (OR: ORMOCER®, OTR = Oxygen Transmission Rate, WTR = Water Vapor Transmission Rate)

10 µm

PETPEThybrid polymer

II

SiOx

Barrier Coatings


Hybrid polymer on SiOx-coated foils for food packaging

Oxygen permeability

reg. cellulose (30 µm) BOPP (30 µm) PET (30 µm)

Foil + SiOx(PVD) (30 nm)

Foil + SiOx(PVD) + hybrid polymer (5 µm)

1.78

1600

25

110

1.01

< 0.

05

< 0.

05

< 0.

05

0.11

[cm³/m²⋅d⋅bar]

regeneratedcellulose

BOPP PET

140.

510.

16

611

25 0.81

[g/m²⋅d]

regeneratedcellulose PE

T

Water vapor permeability

Barrier Coatings

22


Aroma barrierproperties

43 47

83

230

0.3 120

BOPP 30 µm,uncoated

[µg/m²⋅d]

BOPP 30 µm +coating (9 µm)

O

Diphenyloxid

H3C O CH3

O CH3 CH3CH2

OHH3C

CH3

OH

H3C CH3

CH3

H3C CH2

Linalylacetat

cis-3-Hexenol

Menthol (+)-Limonen

Hybrid polymer on SiOx-coated foils for food packaging

Barrier Coatings


Flexible polymer barrier films for the encapsulation of solar cells

Encapsulation system for solar modules: a) the front side, b) the rear side of the solar cell

Barrier Coatings

23


Protection of sensitive surfacesCoatings with optical propertiesCoatings with barrier propertiesModification of surface polarity

Antigrafiti / antisoiling coatingsHydrophilic / hydrophobic coatings

Electroactive layersSensor layers


hydrophilic

hydrophobic

Wetting of inorganic-organichybrid coatings of varyingpolarity by water droplets

Modification of Surface Polarity

“superhydrophobic”: θ > 150°; „superhydrphilic“: θ = 0°

24


(RO)3Si NH

O

O

C8F16H

C6F13(RO)3Si

While alkyl chains provide hydrophobicity, fluoroalkyl chains also provide oleophobicity

Examples for fluorinated silanes

(Super-)Hydrophobic Surfaces

Superhydrophobicity: + nanostructured surface

Lotus effect


Superhydrophobic Coatings

drop diameter 0.2 mm

Gel from Si(OMe)4

Silicone mould

G. M. Whitesides et al. , 1998

Hydrophobization by a monolayer of Cl3SiCH2CH2(CF2)9CF3contact angle before: 118°, after: 170°)

J. Bico et al. , 1999


25


Hydrophobic or Oleophobic Coatings

• less adhesion of dust particles• easier to clean• anti-wetting behavior of paints = anti-graffiti coatings

Easy-to-clean coating

Anti-grafiti coating Anti-soiling coating

Antiadhesive coating


black paint

glass slidenot coated

glass slidecoated


Protection of sensitive surfacesCoatings with optical propertiesCoatings with barrier propertiesModification of surface polarityElectroactive layers

Antistatic coatingsTransparent conducting coatingsDielectric layersPiezoelectric layersElectrochromic layers

Sensor layers

26


Best results for:

Polar goups

Ionic groups

Partially coated polycarbonate tile (ash test)

Antistatic properties can be obtained by• increasing the proportion of polar groups• incorporating ionic compounds

Antistatic Coatings

OSiO

OSiCH2OH

OH

+ H2O

OSi OSiCOOH

+ H2O

OOO

COOH

NMe3+Si

Electroactive Layers


Transparent conducting coatings on glass

Sheet resistance vs. sintering temperature of dip-coated SnO2:Sb (ATO, 10 layers), In2O3(ITO, 2 layers) and ZnO:Al (AZO, 10 layers) on silica glass → adjustable sheet resistance

Transmission (— ) and reflectance spectra (- -) of dip-coated ATO and AZO (layer on both sides) and ITO coatings (layer on one side)


27


Inorganic-organic hybrid materials as dielectric layers in microelectronics

Good adhesion to various substratesPatternable by direct laser-writing or laser ablation

Test structure by direct laser writing

5. Pentrium® chip set4. I.-O. layer with 2nd

signal plane3. I.-O. layer with 1st signal

plane2. I.-O. layer with power

plane1. Ground plane

Manufacturing stages (bottom to top) for one of the smallest Pentium® Multichip Moduls (MCM-L/D, 40 x 40 x 1.2 mm) by multilayers of inorganic-organic hybrid materials



Piezoelectric Layers

Pb(OAc)2 · 3 H2O + Ti(OPr)4 + Zr(OPr)4 + acetylacetone

Pb(Zr0.53Ti0.47)O3

Film thickness on a metal substrate about 0.8 μm. Piezoelectric charge:

piezoelectricsensor actuator


28


Electrochromic Devices

Applications • "Smart Windows" • Automotive glazing and sunroofs • Active and passive displays

ITO = indium tin oxideFTO = fluorine-doped tin oxide

tungsten trioxide

inorganic-organic hybrid polymer

CeO2/TiO2



Protection of sensitive surfacesCoatings with optical propertiesCoatings with barrier propertiesModification of surface polarityElectroactive layersSensor layers

29


Fiber-optical sensors

Sensor fiber in a CFK-composite (photo: DaimlerChrysler AG)

signal of an optical sensors with CO2-sensitive ORMOCER® layer at different humidities

Ormocer®sensor layer

optical fiber

hours

Phase shift [deg]

Sensors

coatings - unipd.it · pdf filepreparation of lead zirconate titanate ... bressanone sept....

Documents