High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Illia Dobryden

Raman and AFM characterization of carbon nanotube – polymer composites

High pressure spectroscopy labDivision of Physics,TFM

Luleå University of Technology

This project is conducted in

High Pressure Spectroscopy Laboratory(Materials Physics group)

Supervisor: Professor Alexander Soldatov

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

OutlineIntroduction

– General Introduction to carbon nanotubes.– Raman spectroscopy of CNTs.– Introduction to carbon nanotube composites.– Functionalization of carbon nanotubes.

Marerials and methods

Results

– Distribution of CNTs in the composite.– Interaction between CNTs and the composite matrix.– The qualitative estimation of CNTs amount in the polymer matrix.– FIB polishing and AFM experiments.

Conclusions and Future Work

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Diameter: < 1 nm up to tens of nm Lenght: < 1 μm up to even several mm High aspect ratio (Lenght/diameter) up to > 10000 Considered as „1D“ material Extraordinary mechanical, electrical, thermal properties

roll-up

Carbon Nanotube (CNT)

Graphene layer

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Single-wall CNT → only one atomic layer in radial direction

- Metallic and semi – conducting- Tend to agglomerate in bundles- Entangled

Double-wall CNT → two atomic layers in radial direction

- Good model system to study intertube interactions- Pressure screening of inner tubes by outer tubes- Reinforcement of outer tubes by inner tubes- Much more resistant to high pressures

Multi-wall CNT→ several atomic layers in radial direction

- Always electrically conductive (metallic behavior)- Entangled- Much bigger diameters than SWNTs

Types of carbon nanotubes

Single-wall CNT

Double-wall CNT

Multi-wall CNT

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Property MWNT Carbon fibre Steel KevlarYoung‘s

Modulus [Gpa] 1060 150 - 950 190 - 210 130

Tensilestrenght [GPa] 63 4-7 0,5 - 2 3 - 4

Physical properties

Individual orbundled CNTs

CNT films orfibres

Silver Copper

El. Conductivity

[S/m]106 104 - 105 59.6 × 106 63.01 × 106

SWNT MWNT Carbonfibres

Silver Copper

Thermal conductivity

[W/mK]6600 3000 8 - 1100 419 401

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Resonance Raman Spectroscopy

Radial breathingmode (RBM)

G - band

BdAt

RBM CNT diameter:

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Composites

CNTs are the good candidates as the filler material because they have great mechanical, electric properties.

Possible problems in using CNTs as the filler material:1. CNTs exist in bundle state.2. Bad interaction between CNTs and the composite matrix. 3. It is difficult to get a good dispersion in the composite.

The Main idea: combine good properties of two or more materials.

Composite

Matrix (Metal, Ceramic, polymer) Filler material (particles, fibers etc)

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Possible Solutions:1. - Good dispersion by ultrasonication.2. - Functionalization of CNTs.

Main idea behind functionalization: Covalent attachment of molecules which will has a good link with the matrix material to CNT surface.

CNTs in our composite: three-step chemical approach to functionalize SWNTs(performed at Henri Pointcaré Univeristy, Nancy)

In situ polymerization has been done with CNTs in the polymer matrix

Composites

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Project motivation

Synthesis and Characterization of the new composite material based on functionalized carbon nanotubes

Raman spectroscopy → proved to give various information aboutCNT systems

Atomic Force Microscopy (AFM) → For direct microstructural study

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Materials and Methods

Materials: - Arc-discharge three step functionalized CNTs (performed at Henri Pointcaré University, Nancy (France)

- PMMA (Polymethylmetacrylate)

We have investigated the PMMA composites with CNTs concentrations: 0,013wt%, 0,023wt%, 0,032wt%, 0,048wt%, 0,08wt%, 0,097wt%and 0,6wt%.

Methods: - The Confocal Raman SpectroscopyRaman spectrometer CRM-200,

- a green NdYVO4 diode laser (532 nm, 2,33 eV)- a red He-Ne laser (633 nm, 1,96 eV )

- Focused Ion Beam (FIB)

- Atomic Force Microscopy (AFM)

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Results

Distribution of CNTs in the composite

Sample surface

laser laserlaserlaser

Raman spectrum at every scanning point

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Results

Distribution of CNTs in the composite

Sample surface

laser laserlaserlaser

The Cluster

The Matrix

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

0 10 00 20 000

50

100

150

200

250

300

350

400

450 C N T C lu s te r In te rp h ase M a tr ix P M M A

R a m a n sh ift (re l. cm -1)

Nor

mal

ized

to h

ighe

st p

eak

Inte

nsity

(a.u

.)

Raman spectra of composite and source materials

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Image : G+ - intensity maps for a) 0.013wt%, b) 0.023wt%, c) 0.048wt%, d) 0,097wt% and e) 0,6wt% CNT – PMMA composites, 2.33eV laser excitation

b)a)

e)

c)

d)

Distribution of CNTs in the composite

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Interaction between CNTs and the composite matrixThe Idea:

- The good composite sample must has quite good interaction between the filler material and the composite matrix.

- We expect that the CNT G-band shifts for Functionalized CNTs(FCNTs) the polymer matrix comparing to pure FCNTs due to interaction between the matrix and FCNTs.

G Shift gives information about:Pressure on CNTs → (upshift)Tensile stress of CNTs → (downshift)Temperature of CNTs → (downshift)Intensity proportional to CNT concentration

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Dependence of the CNT G-band shift in the PMMA matrixvs CNT concentration

→ There is G UpShift on the graph. It indicates that the PMMA matrix applies pressure on FCNTs.

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

FIB polishing for AFM experiments

a)

b)

Pt

Polishing of surface for AFM studies

SEM – images

835 nm

300 nm

13.5 ±0.3 μm

untreatedsurface

untreatedsurface

FIB polishedsurface

AFM image

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

AFM experiment

Height view

19nm

19nm

22nm

10nm

Crossection ImageWhite dot diameters: 10 – 40nmAFM image

SEM image

20 nm

19 nm

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Conclusions

Distribution of CNTs in PMMA composite is inhomogenious.

There is an indication that the matrix molecules surrounding theCNTs exert pressure on the nanotubes.

The CNT bundle size in the polymer matrix is ~ 20 nm.

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Future work

Further AFM experiments (nano-indentation) to determine mechanical properties of the composites

Spectroscopic study of thermal effects in CNT-PMMA composites exposed to high power laser irradiation

Increase of CNT dispersion in polymer matrix via purification offunctionalized CNT (from non-functionalized)

High pressure spectroscopy labDivision of Physics,TFMLuleå University of Technology

Collaboration/Acknowledgements

International Graduate School “PhD Polis“(TFN LTU)

in collaboration with Prof. Edward McRae and Prof. Brigitte VigoloCarbon Materials group, Nancy University:

Associate Prof. Nils Almqvist (AFM experiments)

Andreas Müller, former group member (now at MPI Stuttgart)Guillaume Chevennement (EEIGM project student)