8/8/2019 Seminar on Cnt
1/54
CarbonCarbon
NanotubesNanotubesByShaweta Mutneja
M.Tech Nanotechnology
A1202810007
http://en.wikipedia.org/wiki/Image:Louie_nanotube.jpg8/8/2019 Seminar on Cnt
2/54
What are CarbonWhat are Carbon
Nanotubes ?Nanotubes ?
Carbon nanotubes are fullerene-Carbon nanotubes are fullerene-
related structures which consist ofrelated structures which consist of
graphene cylinders closed at eithergraphene cylinders closed at eitherend with capsend with caps containing pentagonalcontaining pentagonal
ringsrings
8/8/2019 Seminar on Cnt
3/54
CapsCaps
** Typical high resolution TEM image of aTypical high resolution TEM image of ananotube capnanotube cap
8/8/2019 Seminar on Cnt
4/54
DiscoveryDiscovery
They were discovered in 1991 byThey were discovered in 1991 bythe Japanese electronthe Japanese electronmicroscopist Sumio Iijima whomicroscopist Sumio Iijima whowas studying the materialwas studying the materialdeposited on the cathode duringdeposited on the cathode duringthe arc-evaporation synthesis ofthe arc-evaporation synthesis of
fullerenes. He found that thefullerenes. He found that thecentral core of the cathodiccentral core of the cathodicdeposit contained a variety ofdeposit contained a variety ofclosed graphitic structuresclosed graphitic structuresincluding nanoparticles andincluding nanoparticles andnanotubes, of a type which hadnanotubes, of a type which hadnever previously beennever previously been
observed.observed.
8/8/2019 Seminar on Cnt
5/54
Why do Carbon Nanotubes form?
CarbonCarbon Graphite (Ambient conditions)Graphite (Ambient conditions)
spsp22 hybridization: planarhybridization: planar
Diamond (High temperature and pressure)Diamond (High temperature and pressure)
spsp33 hybridization: cubichybridization: cubic
Nanotube/Fullerene (certain growth conditions)Nanotube/Fullerene (certain growth conditions)
spsp22 + sp+ sp33 character: cylindricalcharacter: cylindrical
Finite size of graphene layer has dangling bonds. These danglingFinite size of graphene layer has dangling bonds. These dangling
bonds correspond to high energy states.bonds correspond to high energy states.
Eliminates dangling bondsEliminates dangling bonds
Nanotube formationNanotube formation ++ Total EnergyTotal Energy
Increases Strain Energy decreasesIncreases Strain Energy decreases
8/8/2019 Seminar on Cnt
6/54
Types of CNTsTypes of CNTs
Single Wall CNT (SWCNT)Single Wall CNT (SWCNT)
Multiple Wall CNT (MWCNT)Multiple Wall CNT (MWCNT)
Can be metallic or semiconductingCan be metallic or semiconductingdepending on their geometry.depending on their geometry.
8/8/2019 Seminar on Cnt
7/54
8/8/2019 Seminar on Cnt
8/54
8/8/2019 Seminar on Cnt
9/54
8/8/2019 Seminar on Cnt
10/54
8/8/2019 Seminar on Cnt
11/54
8/8/2019 Seminar on Cnt
12/54
8/8/2019 Seminar on Cnt
13/54
8/8/2019 Seminar on Cnt
14/54
8/8/2019 Seminar on Cnt
15/54
Nanotubes are formed byNanotubes are formed byrolling up a graphenerolling up a graphene
sheet into a cylinder andsheet into a cylinder and
capping each end withcapping each end with
half of a fullerenehalf of a fullerene
molecule. Shown here is amolecule. Shown here is a
(5, 5) armchair nanotube(5, 5) armchair nanotube
(top), a (9, 0) zigzag(top), a (9, 0) zigzag
nanotube (middle) and ananotube (middle) and a
(10, 5) chiral nanotube.(10, 5) chiral nanotube.
The diameter of theThe diameter of the
nanotubes depends onnanotubes depends onthe values ofthe values ofnn andand mm..
8/8/2019 Seminar on Cnt
16/54
(Definition of(Definition of
Vectors)Vectors)Chiral vector
21 aaC mnh +=a1
a2
O
(4,-5)
Ch
T
x
y
(6,3)
)23,
23(
)2
3,
2
3(
2
1
cccc
cccc
aa
aa
=
=
a
a
aacc
== 321 aa
a
a
)2
1,
2
3(
)2
1
,2
3
(
2
1
=
=
a
a
8/8/2019 Seminar on Cnt
17/54
(0,0)Ch = (10,0)
(10,0) SWNT(10,0) SWNT
(zigzag)(zigzag)
a1a2
x
y
8/8/2019 Seminar on Cnt
18/54
(0,0)Ch = (10,0)
(10,0) SWNT(10,0) SWNT
(Animation)(Animation)
a1a2
x
y
8/8/2019 Seminar on Cnt
19/54
(0,0)
Ch = (10,10)
(10,10) SWNT(10,10) SWNT
(armchair)(armchair)
a1a2
x
y
http://opt/scribd/conversion/tmp/scratch2328/wrapping.exe8/8/2019 Seminar on Cnt
20/54
(0,0)
Ch = (10,10)
(10,10) SWNT(10,10) SWNT
(Animation)(Animation)
a1a2
x
y
http://opt/scribd/conversion/tmp/scratch2328/wrapping.exe8/8/2019 Seminar on Cnt
21/54
(0,0)
Ch = (10,5)
(10,5) SWNT(10,5) SWNT
(chiral)(chiral)
a1a2
x
y
http://opt/scribd/conversion/tmp/scratch2328/wrapping.exe8/8/2019 Seminar on Cnt
22/54
(0,0)
Ch = (10,5)
(10,5) SWNT(10,5) SWNT
(Animation)(Animation)
a1a2
x
y
H l L ttiH l L tti
http://opt/scribd/conversion/tmp/scratch2328/wrapping.exe8/8/2019 Seminar on Cnt
23/54
Hexagonal LatticeHexagonal Lattice
(n,m) nanotubes(n,m) nanotubes
a1
a2x
y
(0,0) (1,0) (2,0) (3,0)
(1,1) (2,1)
Zigzag
Armchair
(2,2)
(4,0) (5,0) (6,0)
(3,1) (4,1) (5,1)
(3,2) (4,2) (5,2)
(7,0) (8,0) (9,0)
(6,1) (7,1) (8,1)
(6,2) (7,2) (8,2)
(10,0) (11,0)
(9,1) (10,1)
(9,2) (10,2)
(3,3) (4,3) (5,3) (6,3) (7,3) (8,3) (9,3)
(4,4) (5,4) (6,4) (7,4) (8,4) (9,4)
(5,5) (6,5) (7,5) (8,5)
(6,6) (7,6) (8,6)
(7,7)
n - m = 3q (q: integer): metallic
n - m 3q (q: integer): semiconductor
8/8/2019 Seminar on Cnt
24/54
Synthesis: overviewSynthesis: overview Commonly applied techniques:Commonly applied techniques:
Chemical Vapor Deposition (CVD)Chemical Vapor Deposition (CVD)
Arc-DischargeArc-Discharge
Laser ablationLaser ablation
Techniques differ in:Techniques differ in: Type of nanotubes (SWNT / MWNT / Aligned)Type of nanotubes (SWNT / MWNT / Aligned)
Catalyst usedCatalyst used
YieldYield
PurityPurity
8/8/2019 Seminar on Cnt
25/54
Synthesis: CVDSynthesis: CVD
Gas phase deposition
Large scale possible
Relatively cheap
SWNTs / MWNTs
Aligned nanotubes
Patterned substrates
Synthesis: arcSynthesis: arc
8/8/2019 Seminar on Cnt
26/54
Synthesis: arcSynthesis: arc
dischargedischarge
MWNTs and SWNTsMWNTs and SWNTs Batch processBatch process
Relatively cheap Many side-products
Synthesis: laserSynthesis: laser
8/8/2019 Seminar on Cnt
27/54
Synthesis: laserSynthesis: laser
ablationablation Catalyst / no catalyst
MWNTs / SWNTs
Yield
8/8/2019 Seminar on Cnt
28/54
Arc dischargemethod
Chemical vapordeposition
Laser ablation(vaporization)
Connect two graphite rods toa power supply, place them
millimeters apart, and throwswitch. At 100 amps, carbonvaporizes in a hot plasma.
Place substrate in oven, heatto 600 C, and slowly add a
carbon-bearing gas such asmethane. As gasdecomposes it frees upcarbon atoms, which
recombine in the form of NTs
Blast graphite with intenselaser pulses; use the laser
pulses rather than electricityto generate carbon gas fromwhich the NTs form; try
various conditions until hiton one that producesprodigious amounts of
SWNTs
Can produce SWNT andMWNTs with few structural
defects
Easiest to scale to industrialproduction; long length
Primarily SWNTs, with alarge diameter range that
can be controlled by varyingthe reaction temperature
Tubes tend to be short withrandom sizes and directions
NTs are usually MWNTs andoften riddled with defects
By far the most costly,because requires expensive
lasers
Overview of potentialOverview of potential
8/8/2019 Seminar on Cnt
29/54
Overview of potentialOverview of potentialapplicationsapplications
< Energy storage:
Li-intercalation
Hydrogen storage
Supercaps
> FED devices:
Displays
< AFM Tip
> Molecular electronics
Transistor
< Others
Composites
Biomedical
Catalyst support
Conductive materials
???
Overview of potentialOverview of potential
8/8/2019 Seminar on Cnt
30/54
Overview of potentialOverview of potentialapplicationsapplications
< Energy storage:
Li-intercalation
Hydrogen storage
Supercaps
> FED devices:
Displays
< AFM Tip
> Molecular electronics
Transistor
< Others
Composites
Biomedical
Catalyst support
Conductive materials
???
8/8/2019 Seminar on Cnt
31/54
Energy StorageEnergy Storage
Experiments & ModellingExperiments & Modelling
Electrochemical Storage of LithiumElectrochemical Storage of Lithium
Electrochemical Storage of HydrogenElectrochemical Storage of Hydrogen Gas Phase Intercalation of HydrogenGas Phase Intercalation of Hydrogen
SupercapacitorsSupercapacitors
8/8/2019 Seminar on Cnt
32/54
Energy StorageEnergy Storage
3-electrode cell3-electrode cell- + -
2
reduction
oxidationCNT H O e CNT H OH x x x x+ + + +
( ) + -2
reduction
oxidation Ni OH NiOOH H e + +
Work Electrode
Counter Electrode
Lithi El t h i lLithium Electrochemical
8/8/2019 Seminar on Cnt
33/54
Lithium ElectrochemicalLithium Electrochemical
ModelModel
i hi lLithi El t
8/8/2019 Seminar on Cnt
34/54
Equilibrium saturation
composition for graphite:LiC6
Purified SWNT bundles:
Li1.7 C6
Ball-milled SWNTs:
Li2.7 C6
20 min
10 min
0 min
Lithium ElectroLithium Electro
ChemicalChemical
Li hi ElLithi El t
8/8/2019 Seminar on Cnt
35/54
Lithium ElectroLithium Electro
ChemicalChemical
EtchingTwo types: lengths of 4 and
0.5 mGood Crev (Li2.1 C6)
Smaller hysteresis
Cut SWNTs have betterproperties concerning Li
intercalation
Voltag
e
[V]
y rogeny rogen
8/8/2019 Seminar on Cnt
36/54
y rogeny rogenElectrochemicalElectrochemical
Lennard Jones PotentialLennard Jones Potential
( )12 6
H-H H-H
LJ H-H4U r
r r
=
y rogeny rogen
8/8/2019 Seminar on Cnt
37/54
y rogeny rogenElectrochemicalElectrochemical
storage modelstorage model
Model of Hydrogen Storage at
room temperature for different
diameters of SWNTs
y rogeny rogen
8/8/2019 Seminar on Cnt
38/54
y rogeny rogenElectrochemicalElectrochemical
Charging & DischargingCharging & DischargingCharge Discharge Cycle
H dH d
8/8/2019 Seminar on Cnt
39/54
HydrogenHydrogen
ElectrochemicalElectrochemical Many contrasting conclusions:Many contrasting conclusions: Positive Ranging from: 0.4 2.3 wt% HPositive Ranging from: 0.4 2.3 wt% H
Negative: No systematic relationshipNegative: No systematic relationship
between purity and storagebetween purity and storage storagestoragenot due to SWNTsnot due to SWNTs
More investigations on theMore investigations on the
mechanism of storage are needed inmechanism of storage are needed inorder to explain this wide range oforder to explain this wide range of
resultsresults
G Ph I t l tiG Ph I t l ti
8/8/2019 Seminar on Cnt
40/54
Gas Phase IntercalationGas Phase Intercalation
of Hydrogen modelof Hydrogen model
G Ph I t l tiG Ph I t l ti
8/8/2019 Seminar on Cnt
41/54
Gas Phase IntercalationGas Phase Intercalation
of Hydrogenof Hydrogen Contrast in results is very high: rangeContrast in results is very high: range
from 0-67 wt%from 0-67 wt%
Reasonable range: 2-10 wt%Reasonable range: 2-10 wt%
More modelling neededMore modelling needed
To compare models they have to useTo compare models they have to use
the same parametersthe same parameters
8/8/2019 Seminar on Cnt
42/54
Super CapacitorSuper Capacitor
Electrochemical double layer
E l e c t r o d e ( + )E l e c t r o d e ( - )
S e p a r a t o r
8/8/2019 Seminar on Cnt
43/54
Molecular electronicsMolecular electronics
FEDsFEDs
CNTFETs
SETs
8/8/2019 Seminar on Cnt
44/54
Field Emitting DevicesField Emitting Devices
Single Emitter
Film Emitter
8/8/2019 Seminar on Cnt
45/54
Field Emitting DevicesField Emitting Devices
Single Emitter
Film Emitter
8/8/2019 Seminar on Cnt
46/54
Field Emitting DevicesField Emitting Devices
Single Emitter
Film Emitter
Patterned Film FieldPatterned Film Field
8/8/2019 Seminar on Cnt
47/54
Patterned Film FieldPatterned Film Field
EmittersEmitters
Etching andlithographyConventional CVD
Soft lithography
T i t P i i l iT i t P i i l i
8/8/2019 Seminar on Cnt
48/54
Transistor Principle inTransistor Principle in
CNTFETsCNTFETs
Transistor
CNTFET
8/8/2019 Seminar on Cnt
49/54
Doping of CNTsDoping of CNTs
SingleSingle ElectronElectron
8/8/2019 Seminar on Cnt
50/54
SingleSingle ElectronElectrontransistortransistor
8/8/2019 Seminar on Cnt
51/54
Future Uses of CNTsFuture Uses of CNTs
Nano-ElectronicsNano-Electronics Nanotubes can be conducting orNanotubes can be conducting or
insulating depending on their propertiesinsulating depending on their properties
Diameter, length, chirality/twist,Diameter, length, chirality/twist,
and number of wallsand number of wallsJoining multiple nanotubes together toJoining multiple nanotubes together to
make nanoscale diodesmake nanoscale diodes Max Current Density: 10^13 A/cm^2Max Current Density: 10^13 A/cm^2
8/8/2019 Seminar on Cnt
52/54
The Space Elevator
The Idea To create a tether from earth to some object
in a geosynchronous orbit. Objects can then
crawl up the tether into space. Saves time and money
The Problem 62,000-miles (100,000-kilometers)
20+ tons
8/8/2019 Seminar on Cnt
53/54
Pictures from
http://www.space.com/businesstechnology/technology/space_elevator_020327-1.html
The Space Elevator
http://www.space.com/businesstechnology/technology/space_elevator_020327-1.htmlhttp://www.space.com/businesstechnology/technology/space_elevator_020327-1.html8/8/2019 Seminar on Cnt
54/54
The Space ElevatorThe Space Elevator
The Solution: Carbon NanotubesThe Solution: Carbon Nanotubes 10x the tensile strengh (30GPa)10x the tensile strengh (30GPa)
1 atm = 101.325kPA1 atm = 101.325kPA
10-30% fracture strain10-30% fracture strain
Further ObstaclesFurther Obstacles Production of NanofibersProduction of Nanofibers
Record length 4cmRecord length 4cm Investment Capital: $10 billionInvestment Capital: $10 billion