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: C 60 / C 70 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 CS 2 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 Storage 3-electrode cell Work Electrode Counter Electrode

Lithium Electrochemical Model

Equilibrium saturation composition for graphite: LiC 6 Purified SWNT bundles: Li 1.7 C 6 Ball-milled SWNTs: Li 2.7 C 6 20 min 10 min 0 min Lithium Electro Chemical

Etching Two types: lengths of 4 and 0.5 μm Good C rev (Li 2.1 C 6 ) Smaller hysteresis Cut SWNTs have better properties concerning Li intercalation Voltage [V]

Hydrogen Electrochemical Lennard Jones Potential

Hydrogen Electrochemical storage 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

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