the wondrous world of carbon nanotubes final presentation ifp 2 february 26, 2003
TRANSCRIPT
The wondrous world
of carbon nanotubes
Final Presentation IFP 2
February 26, 2003
Group members:
Client:• Prof. P.H.L. Notten (Philips / TU/e)• ir. R.A.H. Niessen (Philips)
Tutor:• X.E.E. Reynhout
IFP group 2
• M.Daenen (N) • P.G.A.Janssen (ST)
• R. de Fouw (ST) • K. Schouteden (N)
• B. Hamers (ST) • M.A.J. Veld (ST)
Overview
• Introduction
• Synthesis & Purification
• Overview of applications
• Single nanotube measurements
• Energy storage
• Molecular electronics
• Conclusion and future outlook
Introduction: common facts
• Discovered in 1991 by Iijima
• Unique material properties
• Nearly one-dimensional structures
• Single- and multi-walled
Introduction: nanotube structure• Roll a graphene sheet in a certain direction:
• Armchair structure
• Zigzag structure
• Chiral structure
• Defects result in bends and transitions
Introduction: special properties• Difference in chemical reactivity for
end caps and side wall
• High axial mechanical strength
• Special electrical properties:– Metallic– Semi conducting
Synthesis: growth mechanism• Metal catalyst
• Tip growth / extrusion growth
Synthesis: overview• Commonly applied techniques:
– Chemical Vapor Deposition (CVD)– Arc-Discharge– Laser ablation
• Techniques differ in:– Type of nanotubes (SWNT / MWNT / Aligned)– Catalyst used– Yield– Purity
Synthesis: CVD
•Gas phase deposition
•Large scale possible
•Relatively cheap
•SWNTs / MWNTs
•Aligned nanotubes
•Patterned substrates
Synthesis: arc discharge
• MWNTs and SWNTs• Batch process
• Relatively cheap
• Many side-products
Synthesis: laser ablation• Catalyst / no catalyst
• MWNTs / SWNTs
• Yield <70%
• Use of very strong laser
• Expensive (energy costs)
• Commonly applied
Purification• Contaminants:
– Catalyst particles– Carbon clusters
– Smaller fullerenes: C60 / C70
• Impossibilities:– Completely retain nanotube structure– Single-step purification
• Only possible on very small scale:– Isolation of either semi-conducting SWNTs
Purification: techniques• Removal of catalyst:
– Acidic treatment (+ sonication)– Thermal oxidation– Magnetic separation (Fe)
• Removal of small fullerenes– Micro filtration– Extraction with CS2
• Removal of other carbonaceous impurities– Thermal oxidation– Selective functionalisation of nanotubes– Annealing
Overview of potential applications
< Energy storage:
•Li-intercalation
•Hydrogen storage
•Supercaps
> FED devices:
•Displays
< AFM Tip
> Molecular electronics
•Transistor
< Others
• Composites
• Biomedical
• Catalyst support
• Conductive materials
• ???
Overview of potential applications
< Energy storage:
•Li-intercalation
•Hydrogen storage
•Supercaps
> FED devices:
•Displays
< AFM Tip
> Molecular electronics
•Transistor
< Others
• Composites
• Biomedical
• Catalyst support
• Conductive materials
• ???
Overview of potential applications
< Energy storage:
•Li-intercalation
•Hydrogen storage
•Supercaps
> FED devices:
•Displays
< AFM Tip
> Molecular electronics
•Transistor
< Others
• Composites
• Biomedical
• Catalyst support
• Conductive materials
• ???
Energy Storage
Experiments & Modelling
• Electrochemical Storage of Lithium
• Electrochemical Storage of Hydrogen
• Gas Phase Intercalation of Hydrogen
• Supercapacitors
Energy Storage3-electrode cell
- + -2
reduction
oxidationCNT H O e CNT H OHx x x x
+ -
2
reduction
oxidationNi OH NiOOH H e
Work Electrode
Counter Electrode
Lithium Electrochemical Model
•Equilibrium saturation composition for graphite: LiC6
•Purified SWNT bundles: Li1.7C6
•Ball-milled SWNTs: Li2.7C6
20 min
10 min
0 min
Lithium Electro Chemical
Lithium Electro Chemical
Etching•Two types: lengths of 4 and 0.5 μm•Good Crev (Li2.1C6)•Smaller hysteresis
Cut SWNTs have better properties concerning Li intercalation
Vol
tage
[V
]
Hydrogen ElectrochemicalLennard Jones Potential
12 6
H-H H-HLJ H-H4U r
r r
Hydrogen Electrochemicalstorage model
Model of Hydrogen Storage at room temperature for different diameters of SWNTs
Hydrogen Electrochemical Charging & Discharging
Charge Discharge Cycle
Hydrogen Electrochemical
• Many contrasting conclusions:– Positive Ranging from: 0.4 – 2.3 wt% H– Negative: No systematic relationship
between purity and storage storage not due to SWNTs
• More investigations on the mechanism of storage are needed in order to explain this wide range of results
Gas Phase Intercalation of Hydrogen model
Gas Phase Intercalation of Hydrogen
• Contrast in results is very high: range from 0-67 wt%
• Reasonable range: 2-10 wt%
• More modelling needed
• To compare models they have to use the same parameters
Super Capacitor
Electrochemical double layer
Electrode (+) E lectrode (-)
Separator
Molecular electronics
• FEDs
•CNTFETs
•SETs
Field Emitting Devices
Single Emitter
Film Emitter
Field Emitting Devices
Single Emitter
Film Emitter
Field Emitting Devices
Single Emitter
Film Emitter
Patterned Film Field Emitters
•Etching and lithography•Conventional CVD•Soft lithography
Transistor Principle in CNTFETs
Transistor
CNTFET
Doping of CNTs
Single Electron transistor
Conclusions
• Mass production is nowadays too expensive• Many different techniques can be applied for
investigation• Large scale purification is possible• FEDs and CNTFETs have proven to work
and are understood• Positioning of molecular electronics is difficult• Energy storage is still doubtful, fundamental
investigations are needed