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Floating Catalyst CVD Methodfor Controllable Synthesis offor Controllable Synthesis of
Single- and Double-walled Carbon Nanotubes
Hui-Ming Cheng
Shenyang National Laboratory for Materials ScienceInstitute of Metal Research, Chinese Academy of Sciences
1
Institute of Metal Research, Chinese Academy of Sciences
Where am I from?Where am I from?
2
Main Directions at my Divisiony
• Synthesis Properties and Applications of Carbon• Synthesis, Properties and Applications of Carbon Nanotubes and Non-Carbon Nanostructures
C b N t b– Carbon Nanotubes– Non-Carbon Nanostructures
• New Materials for Clean Energy Applications– Energy storage materialsgy g– Solar energy materials
• Exploration of Hydrogen Storage Materials• Exploration of Hydrogen Storage Materials• Fabrication and Applications of High-performance
3
Carbon Materials
Main Directions at my Divisiony
• Synthesis Properties and Applications of Carbon• Synthesis, Properties and Applications of Carbon Nanotubes and Non-Carbon Nanostructures
C b N t b– Carbon Nanotubes– Non-Carbon Nanostructures
• New Materials for Clean Energy Applications– Energy storage materialsgy g– Solar energy materials
• Exploration of Hydrogen Storage Materials• Exploration of Hydrogen Storage Materials• Fabrication and Applications of High-performance
4
Carbon Materials
Outline
• Synthesis of CNTs by Floating Catalyst CVD
(SWNT DWNT MWNT )(SWNTs, DWNTs, MWNTs)
• Structural Control of SWNTs and DWNTs
– The effect of sulfur, carrier gas, and carbon feeding rate
S th i f CNT ith di t di t ib ti– Synthesis of CNTs with narrow diameter distribution
• Growth mechanism of SWNTs/DWNTs by FCCVD
• Concluding remarks
5
Potential Applications of CNTs
Large ScaleField emittersField emittersEnergy storageCompositesComposites
IndividualTransistorElectronic devices
STM/AFM tipsSensors
6D Tomànek, NT06 Presentation
Electronic Structure --- Structural Control
torsemiconducmetal
133
⎩⎨⎧
±=−
pp
mn rEgap /1∝
7R Saito et al., Appl. Phys. Lett. 60(1992) 2204 .R Saito et al, Phys. Rev. B 61(2000) 2981.
Challenges for CNT Synthesis
D l t f l t l l f• Development of low-cost, large-scale processes for the synthesis of high-quality CNTs
• Control over the structure and electronic properties of CNTs
• Control over the location and orientation of CNTs on a flat substratea flat substrate
• Development of a thorough understanding of the growth mechanism of CNTs
8J Liu, SS Fan and HJ Dai, MRS Bulletin, 2004.
Pioneered Methods for SWNT Synthesis
Arc Discharge Method Laser Ablation MethodArc Discharge Method Laser Ablation Method
Developed by RE Smalley group(A Thess et al, Science 1996)
9
Developed by S Iijima(Nature 1993)
Growth of SWNTs by CVD methody
SWNTsSWNTs
H.J. Dai, et al., Chem. Phys. Lett. 1996
Large scale:• Carbon supply• Catalyst supply• Reaction time
Ferrocene
10
• Reaction time• …
Floating Catalyst CVD Method (FCCVD)
19981998
FerroceneSWNTs
H2 (Ar or their mixture)CH (C H CO C H Alcohol)CH4 (C2H2, CO, C6H6, Alcohol)
Thiophene
Potential for continuous preparation Possibility of structural control
11
HM Cheng et al., Appl. Phys. Lett. 72 (1998) 3282.
HM Cheng et al., Chem. Phys. Lett. 289 (1998) 602.Low cost, high puritySimple post-treatment
SWNTs by FCCVD
12HM Cheng et al., Chem. Phys. Lett.289 (1998) 602.
TEM Images of the SWNTs by FCCVD
13
Synthesis of DWNTs by FCCVD
20Gaussian fit
10
15
Gaussian fit
Mean diameter: 1.52 nm
er o
f DW
NTs
0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.80
5
Num
be
I di t f DWNT ( )Inner diameter of DWNTs (nm)
30
35
15
20
25
30 Gaussian fit
Mean diameter: 2.26 nm
er o
f DW
NTs
1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.60
5
10
Num
be
O t di t f DWNT ( )
14> 70%
Outer diameter of DWNTs (nm)
WC Ren, HM Cheng et al., Chem. Phys. Lett. 359 (2002) 196.
CNFs/MWNTs with Different Diameter and Wall Thicknesswith Different Diameter and Wall Thickness
150 nm< 10 nm 50-70nm 70-100 nm20-40 nm
Carbon feeding rate
YY Fan, HM Cheng et al., Carbon 38 (2000)789.
Catalyst particle sizeSulfur concentration
15
YY Fan, HM Cheng et al., Carbon 38 (2000) 921.YY Fan, HM Cheng et al., J. Mater. Res. 13 (1998) 2342.
Sulfur concentration
Outline
• Synthesis of CNTs by Floating Catalyst CVD
(SWNT DWNT MWNT )(SWNTs, DWNTs, MWNTs)
• Structural Control of SWNTs and DWNTs
– The effect of sulfur, carrier gas, and carbon feeding rate
S th i f SWNT ith di t di t ib ti– Synthesis of SWNTs with narrow diameter distribution
• Growth mechanism of SWNTs/DWNTs by FCCVD
• Concluding remarks
16
The Effect of Sulfur-- Necessary?
F & A
Without the addition of sulfur
Ferrocene & Argon
Without additional carbon
L d ti it17
• Low productivity
The effect of Sulfuron the Purity and Quality of SWNTson the Purity and Quality of SWNTs
with sulfur without sulfur
18
• Higher purity• Higher quality and narrower distribution
The Effect of Sulfur on the Diameter Distribution of SWNTson the Diameter Distribution of SWNTs
Without sulfur With sulfur
• Broad diameter distribution!
19
The Effect of Sulfur on Diameter and Shell Numberon Diameter and Shell Number
20WC Ren, HM Cheng et al., J. Nanosci. Nanotech. 6 (2006) 1339.
The Effect of Sulfur on the Diameter and Shell NumberSulfur is necessary for the synthesis of SWNTs and DWNTs with a high productivitySulfur plays an important role in the structural control (diameter and shell number ) of CNTson the Diameter and Shell Number
ω = A1/dt+A2
and DWNTs with a high productivitycontrol (diameter and shell number ) of CNTs
1 t 2
21WC Ren, HM Cheng et al., J. Nanosci. Nanotech. 6 (2006) 1339.
The Effect of Carrier GasHydrogen is beneficial to the synthesis of Diameter Narrowly-distributed SWNTs
159170
Diameter Narrowly distributed SWNTs
258220197
1591Ar
40
50
60 Gaussian fit Mean diameter: d= 1.15 nm
of S
WN
Ts
159141284 1554
2613
10
20
30
40
Num
ber o
100 200 300 400 500Raman Shift ( cm-1) 500 1000 1500 2000 2500
1311
Raman Shift ( cm-1)
0.4 0.8 1.2 1.6 2.0 2.4 2.80
10
Diameters of SWNTs (nm)90
139H2
1589
60
70
80
9085% SWNTs with diameters of 1.7±0.2 nm
Gaussian fit Mean diameter: d= 1.72 nmSW
NTs
20
30
40
50N
umbe
r of S
22100 200 300 400 500
Raman shift ( cm-1) 500 1000 1500 2000 2500
2631
Raman shift ( cm-1)
1315
0.4 0.8 1.2 1.6 2.0 2.4 2.80
10
20
Diameters of SWNTs (nm)
The Effect of Carbon Feeding RateLow carbon feeding rate is beneficial to the synthesis of Narrowly-distributed SWNTsthe synthesis of Narrowly distributed SWNTs
Carbon source: Methaney
150 15866ml/min
Inte
nsity
Inte
nsity
145 193
13222634
158910ml/min
nten
sity
168 tens
ity
In Int
1317
2634
23
100 200 300 400 500Raman Shift ( cm-1)
500 1000 1500 2000 2500Raman Shift ( cm-1)
Aligned DWNT ropes by FCCVD
> 10 cm
24WC Ren, HM Cheng et al., J. Phys. Chem. B 109 (2005) 7169.
Typical HRTEM Images of DWNTs
Outer diameter: 1.7-2.0 nm Inner diameter: 1.0-1.3 nm
> 90%
25
RBM Mapping of DWNT Ropes
Raman shift cm-1
26Narrow diameter distribution
Outline
• Synthesis of CNTs by Floating Catalyst CVD
(SWNT DWNT MWNT )(SWNTs, DWNTs, MWNTs)
• Structural Control of SWNTs
– The effect of sulfur, carrier gas, and carbon feeding rate
S th i f SWNT ith di t di t ib ti– Synthesis of SWNTs with narrow diameter distribution
• Growth mechanism of SWNTs/DWNTs by FCCVD
• Concluding remarks
27
Structural Correlation between SWNTs and the Attached Catalyst Particlesy
200
50
60
70 (a)
SWN
Ts
120
140
160
180 (b)
Fe-N
Ps
20
30
40
Num
ber o
f S
60
80
100
Num
ber o
f F
0.44 nm2 nm
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.00
10
Diameters of SWNTs (nm)2 3 4 5 6 7 8 9 10 11 12 13
0
20
40
Diameter of Fe-NPs (nm)
• The size of catalyst particles : > 5nm
2 nm
• The diameters of SWNTs or DWNTs: < 3 nm (in general)• SWNTs growth on the localized region of the surface of catalyst
28
Localized nucleation on big catalyst particlesWC Ren, HM Cheng et al., J. Phys. Chem. B 110 (2006) 16941.
Structural Correlation between SWNTsBundles and the Attached Catalyst ParticlesBundles and the Attached Catalyst Particles
2 nm
Localized nucleation on big catalyst particles
29
Tip Structure of SWNTs at the Initial Nucleation Stageat the Initial Nucleation Stage
CapsCaps
F ti f th t tFormation of the cap structure ― Bending of graphite islands on the localized zone
30of the surface of catalyst particles
Role of Sulfur on the Formation of the Small CapsSmall Caps
VLS growth mechanism― Precipitation of carbon from the localized liquid zone
The role of sulfur• Decreasing melting point of localized zone• Decreasing melting point of localized zone
– Key point for the localized nucleation (the diameter of CNTs is closely correlated with the addition amount of sulfur)
• Enhancing the decomposition of carbon sources– Inhibit the continuous extending of graphite– Inhibit the continuous extending of graphite
islands• Introduction of defects in the graphite islands
E h th b di f hit i l d d
31
– Enhance the bending of graphite islands and consequently nucleation
Proposed Growth Model
Sulfur-assisted localized nucleation at low temperatureSulfur assisted localized nucleation at low temperature
a
b
c
I II III
c
Fe atoms
Fe-C-S phase
Temperature gradient
32
The liquid catalyst
WC Ren, HM Cheng et al., J. Phys. Chem. B 110 (2006) 16941.
Concluding Remarks g
• Developed a floating catalyst CVD method for the synthesis of SWNTs and DWNTsy
• Attempted the diameter and shell number control of CNTCNTs
• Obtained SWNTs and DWNTs with narrow diameter distribution
P d l li d l ti d l f th• Proposed a localized nucleation model for the growth of SWNTs and DWNTs by FCCVD
33
Acknowledgment
• Dr. Wencai Ren• Dr. Feng Li• Mr. Qingfeng Liu• Mr. Bilu Liu
• Prof. M Dresselhaus at MIT
• NSFC, MOST, and CAS for financial support
34
• JSPS for supporting this visit
Thank you very muchThank you very much for your attention!for your attention!
35