Nanocomposites

INM – Leibniz Institute of New Materials

Stefan Brück

1.7.2014 Webinar

Nanoparticles, The Key Element

Nanoparticles + Matrix + ??? = Nanocomposite

2D Nanocomposites: Coatings

Examples of Applications

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Agenda

3

Particles with diameter up to 100 nm

d < 1/20 λ rule of thumb

No light scattering in transparent matrix

when diameter smaller then 1/20 of wavelength

Which nanoparticles?

Chemical composition: SiO2, Al2O3, ZrO2, TiO2, Metals, ...

Morphology: spheres, needles, flakes/platelets

„Third“ or „functional“ property:

Passive e.g. refractive index

Active e.g. non linear optical properties NLO

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Why nanoparticles?

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Properties by nanoparticles

Optical properties

No light scattering by NP, color can be selected

Adaptable refractive index e.g. for light guide adhesives

UV / IR protection with absorbing nanoparticles

Electrical properties

Electical conductive but transparent coatings

Printable electronics

Magnetic properties (superparamagnetic iron oxide < 30 nm)

Temperature increase in magnetic field for bond/disbond-on-command

Rheological properties

Adapting viscosity of reactive mixtures

Thermo-/mechanical properties

Reduction of thermal expansion

Scratch and/or abrasion resistance

Anti-Friction, corrosion protection…

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Elements of polymer matrix nanocomposites

Free linear polymer chains, loops, net connections

Particles and particle-particle contacts

Polymer-particle contacts: Interface layer

Nanocomposite is combination of matrix and nanoparticle

„reinforcement“

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Nanocomposite Basics

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Interface layer – the third compound

in nanocomposites!

Attachment of polymer chains on particles with high specific surface area

Formation of interface layer (phase) with higher degree of order

Interface layer is substancial part of composite!

Low degree of

order

High degree of

order

Particle diameter / nm

7

NANO-

MER

organo silane

based sol-gel

type structures:

hybrid

structures

glasses

polymer type

structures

polymeric chains

nano scale particles

e.g. ZrO2, Al2O3, TiO2

Cu, Ag, Pt, CdS, FeOx,....

ceramics,

metals,

semiconductors

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INMs Nanomer materials

8

Inorganic network

O S i

O

O

Inorganic network [M] = Ti, Zr, Al, ...

O [ M ]

Mixed inorganic-organic network

O

O

O

O S i S i O

O

O O

O

O

Surface

modified

nanoparticles

Organic network (Silsesquioxanes, Silicones)

C F 3

( C F 2 ) n

( C H 2 ) 2

O S i O S i O

O O

C H 3

S i O

H 3 C

C H 3

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Chemistry

9

Curing

Heat

Light

D T, IR, Laser

Room temperature - 350°C

NIR,UV, VIS, Laser

Electron beam

e -

Coating (wet processing)

Dip coating

Spin coating

Spray coating

Roller coating

Screen printing

flooding

and many more including

powder coating ….

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Processing

Wet chemical deposited TCO

coatings

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TCO (e.g. ITO) applications:

Nanosized Indium tin oxide (10-15 nm)

Transparent electrodes for:

- Displays

- Touch screen panels

- Solar cells

- Smart windows

- Printed electronics

IR reflecting materials: energy saving glass

Antistatic coatings

Advantages of wet chemical deposited TCO coatings:

Cost-effective processing: roll to roll, printing, spraying

high speed, low material consumption

direct patterning by printing, no additional etching [1] S. Heusing et al., Proc. SPIE,

Vol. 6999 (2008) 69992I

[2] M. Tuomikoski et al., Proc.

SPIE, Vol. 6192 (2006) 619204

Printed and patterned ITO coatings

of the INM on PET foil

Organic photodiode (OPD)** with

printed ITO coating of INM

as bottom electrode [1]

** OPD was fabricated in Joanneum

Research-NMP, Weiz, Austria

Properties of TCO coatings

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CB

conduction band

forbidden zone /

Band gap 3.2 eV

valence band

VB

UV-Light

<388 nm

O2

.O2-+H+ HO2

.

H2O

.OH + H+

Photocatalytic Coatings

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Principle:

TiO2 is a semiconductor (bandgap 3.2 eV)

Irradiation with UV-A

electrons are promoted to CB

formation of electron/hole-pairs.

Migration of e- and h+ to the surface.

With water (e.g. moisture)

aggressive radicals are formed

Wet film

Film with gradient

in TiO2-concentration

Drying

Curing

matrix sol (hydrolysed silianes, solvents etc.)

F-modified nano TiO2 particles

particulate silica

Substrate

Shrinkagedue to curing

Substrate

Synthesis of Photocatalytic Coatings

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State of the Art: Multi layer systems

prevent catalyst poisoning by Na+ ions

prevent degradation of substrate

INM approach:

Nanosized anatase titania (9-12 nm)

Unique single layer system based on

modified nanoparticles with fluoro

organic silanes

Single Layer Coating:

One step coating application

Transparent coatings

Thin coatings (1-1.5 µm)

High photocatalytic activity

Color, look and feel substrate is

preserved

Photocatalytic Coating Applications

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Self-cleaning surfaces

• Photocatalytic degradation of dirt, soot

on surfaces: tent textiles, fassades, roof

tiles, outdoors equipment etc.

Antimicrobial effect:

Photocatalytic degradation of microbes

on sanitary surfaces, in medical

installations etc.

Anti growth effect:

No growth of algae, lichens etc. on

outdoor equipment

Pigmented, fine-textured tribological composite materials

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high friction force perpendicular to layered structure

low friction force parallel to layers

Principle I: Low friction by solid state lubricants: example boron nitride BN

scheme of hexagonal BN structure SEM micrograph of a sub-µm BN

shear stress

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Principle II: Gas diffusion barrier by inorganic platelets/ Hartstoffe in Polymermatrix

Platelets Nano-Particles Matrix

Substrate

Pathways

Metall-Substrat

longer diffusion pathways for gas molecules

platelets: e.g. micro glass flakes

hard particles: e.g. Si3N4

hard particles platelets

Principle III: Wear resistance by hard particles

21

f

p

p

c

W

LP

P

ratioAspect

filler offraction Volume

polymer offraction Volume

polymer unfilled ofty Permeabili

polymer filled ofty Permeabili

W

L

P

P

f

p

p

c

matrix

permeability

diffusion coeff.

solubility coeff.

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Principle IV: Composite with fine-textured morphology

hard particles

polymer matrix

coat

ing

lubricant

substrate

tortuous path O2, H2O, SO2

platelets (“inactive“ in lubrication effect) in a roof-tile arrangement WO 002013092835 A1, INM gGmbH

Composite with fine-textured morphology

Combination of lubricants / platelets / hard particles in a polymer matrix

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coat

ing

metal substrate

controlled transfer film formation

relative movement

stabilising hard particles

The friction process: low friction with controlled wear

friction counterpart

New unexpected effects by introduction of “inactive“ platelets in low friction coatings?

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Optimisation of the hard filler content: example Si3N4

Reihe Si3N4 E05 mit 30% BN 110 / 5% LS / 10% FL

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,4

0 2000 4000 6000 8000 10000 12000

Runden

Reib

un

gsko

eff

izie

nt

µ

A 200 / 0% Si3N4 E05

A 233 / 1,25% Si3N4 E05

A 234 / 2,5% Si3N4 E05

A 235 / 5,0% Si3N4 E05

A 236 / 10% Si3N4 E05

A 237 / 15% Si3N4 E05

2,5 wt.-% Si3N4

coef

fici

ent

of

fric

tio

n µ

rounds

0 wt.-% 1.25 wt.-% 2.5 wt.-% 5.0 wt.-% 10 wt.-% 15 wt.-%

Introduction of hard particles with moderate hardness (HU = 1500 MPa) gives possibility for further improvement

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600 h SST 600 h SST

coating partially scratched off

Corrosion resistance of fine-textured low friction coating in neutral salt spray test (SST)

low friction coating on mild steel coating thickness 25 µm

no delamination no blistering no subsurface migration

Highly structured barrier layers

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Influence on the platelet arrangement to improve barrier effect

high degree of platelet alignment with orienting additive

(sample L)

low degree of platelet alignment without orienting additive

(sample F)

SEM analysis on cross-sections of foils after brittle fracture

WO 002013092841 A1, INM gGmbH Highly structured composite material for protection

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Measurement set-up for O2-permeation

Oxtran Permeation Device from MOCON

(Mineapolis, USA) sweep gas: N2 testing gas: O2

According to ASTM D3985

20-50 µm thick coating layer prepared as a foil

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A D E W F L X0

1

2

3

4

5

6

7

1,4

3,2

2,2

2,62,5

3,6

6,5

Perm

eatio

nsk

oeff

izie

nt

[cm

3m

m/m

2d]

Beschichtungsnummer

0 wt.-% 10 wt.-% platelets

20 wt.-% platelets

Influence of platelet alignment on barrier properties: O2- gas permeation measurement

permeation coefficient = O2 volume · layer thickness

time · area

[cm3] · [mm]

[d] · [m2]

per

mea

tio

n c

oef

fici

ent

sample platelets = aligned optimised matrix

SEM- analysis

matrix with higher cross-linking density

INM - Leibniz Institut für Neue Materialien gGmbH

Campus D2 2

66123 Saarbrücken

www.inm-gmbh.de

Dr. Cenk Aktas

Cenk.Aktas@inm-gmbh.de

Stefan Brück

Stefan.Brueck@inm-gmbh.de

+Composites Webseite

www.pluscomposites.eu

29 7/1/2014

Contacts Germany