Carbon Nanotubes

Transcription

Carbon Nanotubes

Carbon Nanotube/Polymer Interface
Ursula Dettlaff
Max-Planck-Institut für Festkörperforschung, Stuttgart
Surfaces and Interfaces – Engineering at the Nanoscale, 7-9 März 2005, DECHEMA – Haus, Frankfurt a. M.
Outline
• What are Carbon Nanotubes?
• Why Carbon Nanotubes are interesting for Nanocomposites
- extraordinary properties
• Examples of CNT composites in polymer matrix:
- PMMA
- Poly Carbonates
• CNT/Polymer interface
- Obstacles in fabrication of CNT composites
Carbon as an Element - from Graphite to Nanotubes
Fullerenes: C60
Diamond
Graphite
Nanotubes
Nanocomposites
Carbon Nanotubes
properties
Polymer
processability
high performance, multifunctional materials
Carbon Nanotubes - Nanocomposites
Goal:
Electrically conductive composites
Electrostatic dissipation
Electromagnetic shielding
Printable circuit wiring
Transparent conductive coatings
Mechanical composites
Polymer reinforcement
Why Carbon Nanotubes ?
Extraordinary properties
1. Chemically very stable, covalent C-C bonding
2. Thermal stable: in the inert atmosphere can be heated up to 2000 °C
3. Mechanical properties: Young‘s modulus 1 Terapascal
– the strongest known materials
4.
Electrically conductive
Carbon Nanotubes/Polymers Composites
SWNTs Aspect ratio
nm
1
=
d
light weight
L/d > 1000
L > 1 µm
Advantage: much lower filler concentration is required
to form conducting network, usually < 1 vol %
spherical particles, like carbon black, require 15 vol %
to reach the percolation
Electrical conductive composites
1. High purity Hipco SWNTs
2. SWNTs with impurities
Carbon Nanotubes/Polymer
Obstacles in fabrication homogeneous composites
1. Smoth nanotube surface is incompatible
with most solvents and polymers
2. SWNTs apper usually in ropes, which are difficult
to disintegrate into individual tubes within the matrix
How to enhance the SWNT/Polymer interaction?
Surface modification of nanotube sidewalls
- effect of a linkage between nanotubes and the
polymer
1. Oxidation in air, HNO3 to introduce defects, polar –COOH
groups
changes the electrical properties of tubes
2. Non-covalent functionalization to form an interface
between nanotubes and polymer
Non-covalent chemical functionalization
+
O
S
Cl
Cl
Sample
Hipco
LA
Arc-disch
Pristine
700
370
240
Modified
3500
1200
960
Increase of electrical conductivity up to factor of 5
1 ,6 x1 0
7
1 ,4 x1 0
7
1 ,2 x1 0
7
1 ,0 x1 0
7
8 ,0 x1 0
6
6 ,0 x1 0
6
4 ,0 x1 0
6
2 ,0 x1 0
6
pristine
15 m in
30 m in
1 h
2 h
22 h
1000
Young modulus (MPa)
Stress (Pa)
Mechanical properties
0 ,0
800
Young‘s modulus of
SWNT network
600
400
0
-1
0
1
2
3
4 5 6 7
S train (% )
8
200
600
800
1000
T im e (m in .)
9 10
Toughness
(MJ/cm3)
400
Strain at
break (%)
SWNTs
Young‘s
Modulus
(Mpa)
pristine
660
90
11
1.7
modified
950
830
37
4.3
Tensile
strength
(Mpa)
1200
1400
10000
1000
100
10
1
0,1
0,01
1E-3
1E-4
1E-5
1E-6
1E-7
1E-8
1E-9
1E-10
1E-11
-10
Composite of pristine SWNT in PMMA
NT-Buckypaper
fc = 0.17 wt %
Composite of SOCl2 functionalized SWNT in PMMA
Electrical conductivity (S/cm)
Carbon Nanotubes/PMMA Composites
σmax = 17 S/cm
β = 1,3
fc = 0,17 %
10
1
0,1
0,01
0,1
1
10
100
Concentration SWNT in PMMA (%)
0
10
20
30
40
50
60
70
80
90
100
110
Electrical percolation
100000
10000
1000
100
10
1
0,1
0,01
1E-3
1E-4
1E-5
1E-6
1E-7
1E-8
1E-9
1E-10
NT-Buckypaper
1000
100
10
1
β = 2,2
fc = 0,17 %
fc = 0.17 wt %
0,1
0,01
σmax = 100 S/cm
1E-3
1E-4
1E-5
1E-6
1E-7
1E-8
1E-9
0,01
0,1
1
10
100
0
20
40
60
80
100
Electrical percolation
Composite of PMMA with SWNT
7
2x10
7
1x10
0.11%
3x10
7
0.55%
2x10
7
6.73%
1x10
0%
0.114%
0.55%
1.08%
6.73%
7
2x10
Stress (Pa)
Stress (Pa)
0%
0,1 %
0,6 %
1,0 %
Stress (Pa)
7
3x10
7
1x10
7
1.08%
0
0
0%
0
Strain (%)
0
0
10
20
Strain (%)
30
0
70
140
210
Strain (%)
Toughness
(GPa)
0.30
A
0.25
0.20
6
4
2
0
A
800
Young modulus
(MPa)
600
B
400
200
30
C
25
20
0.0
0.5
1.0
Concentration (%)
1.5
2.0
Tensile srength
(MPa)
Tensile srength Young modulus
(MPa)
(MPa)
Toughness
(GPa)
B
600
400
C
300
200
-1
0
1
2
3
4
5
6
7
Concentration (%)
SEM images
Composite surface
Cross-section of composite film
Ab initio calculations
List of Collaborators
•Siegmar Roth, MPI FKF, Stuttgart, Germany
•Viera Skakalova, MPI FKF, Stuttgart, Germany
•Uwe Vohrer, FGB, Stuttgart, Germany
•David Tomanek, Michigan State University, East Lansing, USA
•FINANCIAL SUPPORT: European Projects: CARDECOM
SPANG

Carbon Nanotubes

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