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Comparison between wet deposition and plasma deposition of silane coatings on metals for surface
passivation
I. De Graeve, F. Brusciotti, A. Batan, M.Wenkin, F. Reniers, J.J. Pireaux, M. Piens, J.Vereecken, H. Terryn
VUB-ULB-FUNDP-CoRIi-SUP2008
FOMOS project
Functional properties by Mixed Nano Organic/Metal Oxide Systems
Acknowledgment for funding: Belgian Science Policy – Belspo“Programme to stimulate knowledge transfer in areas of strategic
importance”
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Consortium
VUBFUNDP ULB
CoRI
Fundamentals
Applied
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Users committee
• Bekaert Technology Center• Aleris Aluminium• R&D Umicore• OCAS-Arcelor Zelzate• Arcelor Research Industry Liège• Coil Landen• Chemetall GmbH • Akzo Nobel Decorative Coatings• SIGMAKALON• IWT
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Main question in the project
Starting point: concept of organic coating of metals
System 1: layered system of metal with native oxide and organic pretreatment coating (< 1µm)
System 1
Metal
Organic layer
Native oxide
Main question in FOMOS :How to improve properties and/or create innovative properties?
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What properties ?
• Mechanical– Hardness– Tribological: friction, wear…– Thermomechanical
• Functional !!! >>> main focus of FOMOS– Corrosion: barrier, inhibitors, self-healing…– Adherence, interfacial bonding…– Optical: appearance, reflectance, colour...– Ageing and chemical stability…– Wettability, hydrophobic/hydrophilic…– Other innovative properties….
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Approach in the project =Investigation of innovative systems (1)
System 2: layered system with tailored metal oxide layer
Metal
Organic layer
Native oxide
System 2
Oxide
Metal
Organic layer
System 1
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Approach in the project =Investigation of innovative systems (2)
System 3: hybrid system of mixed organic / metal oxide nanoparticle coating
System 3
Metal
oxide
Metal
Organic layer
Native oxide
System 2
Oxide
Metal
Organic layer
System 1
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Variables
System 1
Metal
Organic layer
Native oxide
System 2
Oxide
Metal
Organic layer
System 3
Metal
oxide
Organic medium: silanes (multimetal ! hybrid organic- inorganic chemistry)
Metal oxide: Si-oxide, Ce-oxide
Coating deposition method !!! - Wet deposition from solutions (water-based)- Solvent free plasma deposition: vacuum and atmospheric
Substrate and pre - and post-treatments:- Aluminium, steel- Precleaning method (chemical or plasma)- Curing of the organic system (thermally induced or during plasma deposition)
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Critical focus points
System 1
Metal
Organic layer
Native oxide
System 2
Oxide
Metal
Organic layer
System 3
Metal
oxide
• Compatibility between inherently very different media>>> Organic molecules versus inorganic metal oxide: interfacial bonding?
• Film formation mechanisms using the various deposition methods? …resulting properties?
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Characterisation Tools
Organic solution characterisation>>> DLS, NMR
Coating characterisation>>> FEG-SEM, FEG-AES, XPS, Tof-SIMS, GDOES, FIB TEM... Vis & IR-SE, Raman,…
Properties characterisation>>> Corrosion standard tests, EIS,… thermomechanical DSC,
TGA, DMA…adherence…optical TIS … wettability contact angle...
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What are silanes ?
Alternative to CrVI+ surface treatments for corrosion protection
Multimetal process on aluminium, steel, magnesium, zinc …
Silanes = hybrid organic-inorganic molecules
H5C
2O Si
OC2H
5
OC2H
5
(CH2)
2Si
OC2H
5
OC2H
5
OC2H
5 H O Si
OH
OH
(CH2)
2Si
OH
OH
OHhydrolysis
= Very reactive towards metal-film bonding and crosslinking
BTSE = bis-1,2-(triethoxysilyl)ethane
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Part 1: Wet deposition of silane
Metal
Organic layer
Native oxide
System 1
FEG-SEM secondary electron images roll-coated layers on aluminium
0.5 wt% BTSE 2.5 wt% BTSE
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⇒ Film morphology depending on solution concentration and wet deposition method (roll-coating vs dipcoating)
Part 1: Wet deposition of silane
Metal
Organic layer
Native oxide
System 1
Formation of hydrogen bonds
Interfacial bond formation
⇒ Strong covalent metal-film bonding; good adhesion
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Part 1: Wet deposition of silane + nanoparticles
Metal
MeOx
System 3
• CeO2 nanoparticles (10-20nm) for barrier properties and as nano-carriers for corrosion inhibitors
• Ce(NO3)3 for self-healing properties
In collaboration with: - Instituto Superior Técnico, ICEMS, Lisboa (Fatima Montemor)- Centre de Recherche Public Henri Tudor (CRP-HT), Luxembourg- Umicore
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FEG-SEM / EDX
Al 99.99% electropolishedSpin/dip Coated with BTSE 5 wt% + 250ppm CeO2+ 250ppm Ce(NO3)3
Metal
MeOx
Thickness is in agreement with VISSE results!
System 3
⇒ Agglomeration of nanoparticles
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FEG-SEM / EDX
Metal
MeOx
System 3
⇒ Agglomeration should be avoided by improved solution preparation
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XPS: bonding between silane and MeOxnanoparticle?
0712030015.SPE: na sputteren: Company Name2007 Dec 3 Mg std 350.0 W 0.0 µ 0.0° 23.50 eV 5.5438e+004 max 3.67 minCe3d/Area1/1 (Shft)
8808858908959009059109159209259303
3.5
4
4.5
5
5.5
6x 104 0712030015.SPE
Binding Energy (eV)
c/s
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Metal
MeOx
System 3Experiment: XPS on CeO2 powder pellet
Ce XPS signals
XPS: bonding between silane and MeOxnanoparticle?
Metal
MeOx
System 30803040024.SPE: CeO2: Company Name2008 Mar 4 Mg std 200.0 W 0.0 µ 0.0° 23.50 eV 2.8903e+004 max 25.94 minCe3d/Area1/1 (Shft)
8808909009109209302
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9x 104 0803040024.SPE
Binding Energy (eV)
c/s
Experiment: XPS on CeO2 powder pellet + drop of BTSE
Ce XPS signals
⇒ Indication of additional type of Ce environment⇒ Possible evidence of silane bond formation on Ce-oxide pellet
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Wet deposition of silane + nanoparticles
Metal
MeOx
System 3
Film properties ? Effect of wet deposition process conditions on properties ?
Ongoing work….
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Part 2: Plasma deposition
Differences with wet deposition?
- Silane vapour is carried by argon gas into the plasma
- Silane is (partially?) decomposed by collision with plasma components
- What is being deposited???
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Part 2 .1: Atmospheric plasma deposition
Thermostat
Chemical bubblerPlasma source
Sample support
Precursor Inlet
Showerhead25 mm of diameter
Coating material BTSE vapour at 100°C (from concentrated solution)
Gas discharge Argon
Substrate to showerhead distance 5 mm
Power 40 to 80 W
Argon flow 23.9 l/min
Deposition time 30 to 300 s
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Part 2.1: Atmospheric plasma deposition
1390 C-H symmetric bending (-CH3)1154 Si-O-C (-SiOCH2CH3)912 Si-O-C symmetric stretching (-SiOCH2CH3)712 C-H rocking
Peak position (cm-1) Assignement
Wavenumber (cm-1)
1000200030004000
Abs
orpt
ion
-0.01
0.00
0.01
0.02
0.03
0.04
0.05
0.06
1390 11
54
912
712
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IR analysis of atmosphericplasma polymerised BTSE at 50W, 10 min
Metal
Organic layer
Native oxide
System 1
⇒ Film contains organic groups
Part 2.1: Atmospheric plasma deposition
Wavenumber (cm-1)
800100012001400
Abs
orpt
ion
-0,01
0,00
0,01
0,02
0,03
0,04
0,05
0,06
10 min 5min15 min
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Influence of deposition time
⇒ Increasing deposition time results in thicker layers
(50 W)
1154 Si-O-C (-SiOCH2CH3)912 Si-O-C symmetric stretching (-SiOCH2CH3)712 C-H rocking
Peak position (cm-1) Assignement
Metal
Organic layer
Native oxide
System 1
Part 2.1: Atmospheric plasma deposition
Wavenumber (cm-1)
7008009001000110012001300
Abso
rptio
n
0,00
0,01
0,02
0,03
0,04
0,0540 W 50 W 70 W80 W
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Influence of input power
⇒ Input power changes the amount of bonds and the chemical environment in the film
(10 min)
1154 Si-O-C (-SiOCH2CH3)912 Si-O-C symmetric stretching (-SiOCH2CH3)712 C-H rocking
Peak position (cm-1) Assignement
Metal
Organic layer
Native oxide
System 1
Part 2.1: Atmospheric plasma deposition
Wavenumber (cm-1)
7008009001000110012001300
Abso
rptio
n
0,00
0,01
0,02
0,03
0,04
0,0540 W 50 W 70 W80 W
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Influence of input power
⇒ Input power changes the amount of bonds and the chemical environment in the film
(10 min)
1154 Si-O-C (-SiOCH2CH3)912 Si-O-C symmetric stretching (-SiOCH2CH3)712 C-H rocking
Peak position (cm-1) Assignement
Film properties ? Effect of plasma conditions on properties ?
Ongoing work….
Metal
Organic layer
Native oxide
System 1
Part 2.2: Vacuum plasma deposition
Aim:
- Step 1: Deposition of Si-oxide from hexamethyldisiloxane HMDSO
- Step 2: Deposition of organic layer of BTSE (similar to atmospheric plasma results; not shown)
System 2
Oxide
Metal
Organic layer
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Part 2.2: Vacuum plasma deposition
System 2
Oxide
Metal
Organic layer
Coating material Hexamethyldisiloxane (HMDSO) solution
Gas discharge HMDSO or HMDSO+O2
Power 50 to 300 W
Deposition time 300 s, 600 s
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Part 2.2: Vacuum plasma deposition
System 2
Oxide
Metal
Organic layer
Wavenumber (cm-1)
1000200030004000
Abs
orpt
ion
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
0.12
1260
1100
800-
712
2960
-290
0
IR analysis of vacuum plasma polymerized coatingfrom HMDSO (300 W, 300 mT, 10 min)
Peak position (cm-1) Assignement
2900-2960 C-H symmetric and asymmetric stretching (-CH3-)1260 CH3 symmetric bending ( -Si(CH3)x)1100 Si-O/-Si-O-Si- stretching790-800 -Si(CH3)n rocking
⇒ ‘oxide’ layer contains carbon groups
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Part 2.2: Vacuum plasma deposition
System 2
Oxide
Metal
Organic layer
Wavenumber (cm-1)
800100012001400
Abso
rptio
n
0,00
0,02
0,04
0,06
0,08
0,10
0,1250 W100 W150 W200 W300 W
1260
1100
800-712
Wavenumber (cm-1)
280028502900295030003050
Abs
orpt
ion
0,00
0,01
0,02
0,03
0,04
0,05
50 W100 W150 W200 W300 W
2960-2900
Influence of input power
⇒ Increased input power results in thicker deposition
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Part 2.2: Vacuum plasma deposition
System 2
Oxide
Metal
Organic layer
Influence of oxygen addition to HMDSO plasma : 20% HMDSO / 80% O2(200 W, 300 mT, 10 min)
⇒ Less carbon groups; more Si-O formation
Wavenumber (cm-1)
1000200030004000A
bsor
ptio
n
0
1
2
3
4
5
6
1260
1100
800-7122960-2900
Peak position (cm-1) Assignement
2900-2960 C-H symmetric and asymmetric stretching (-CH3-)1260 CH3 symmetric bending ( -Si(CH3)x)1100 Si-O/-Si-O-Si- stretching790-800 -Si(CH3)n rocking
⇒ Confirmed with XPS
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Part 2.2: Vacuum plasma deposition
System 2
Oxide
Metal
Organic layer
⇒ Oxygen addition favours decomposition of the HMDSO in the plasma and the deposition of a purer, inorganic layer of Si-oxide
⇒ x% HMDSO / 100-x % O2 mixture
= variable for film property variations !
= formation of layers with variable level of carbon groups and inorganicspecies resulting in different (???) film properties
Film properties ? Effect of plasma conditions on properties ?
Ongoing work….
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Conclusions
⇒ different deposition methods and deposition conditions result in different types of films in terms of morphology and composition (organic, inorganic or mixed)
Film properties ?
Effect of processing conditions on properties ?
Ongoing work….
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