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CNT Synthesis by Thermal CVD method
&
its’ Characterization
Jamia Millia IslamiaCentral University India
Presentad by-Mohd.Ghulam.Moinuddin
M.Sc Electronics(2015)
Points aimed in this presentation
• Physics of CNT.
• Synthesis of Carbon nanotubes.
• Role of catalyst in growth.
• Catalyst and their role for synthesis
• Result analysis
Carbon nanotubesA 1D structures
• Carbon nanotubes (CNTs) are allotropes of carbon.
• CNT can be described as a sheet of graphite rolled into a cylinder
• Constructed from hexagonal rings of carbon.
• Can have one layer or multiple layers-
SINGLE WALL NANOTUBE(SWNT), MULTIWALL NANOTUBE(MWNT)
Great applications in nanotechnology, electronics, optics.
Physical structure of CNT
Armchair (n,m) = (5,5)
= 30
Zig Zag (n,m) = (9,0)
= 0
Chiral (n,m) = (10,5)
0 < < 30
Physical properties of CNTs-
Conductivity and strength
- “current-carrying capacity is 1000 times higher than that of copper...” due to more electron than and metallic surface
- As hard as the diamond in fact twice harder than pure diamond.
100 times stronger than stainless steel and six times lighter.
Thermal stability & reliability
CNT is thermally stable up to 4000K.
Smart Sensors
Sensitive to make – sensor
Chemically active, highly sensitive towards light
Chemical Vapour Deposition
• Commercial method for production of carbon nanotubes
• Substrate is prepared with a layer of metal catalyst particles(mostly
nickel, cobalt, iron, or a combination)
• Diameters of the nanotubes depends on the size of the metal particles
• Two gases are flown into the reactor:
– a process gas (such as ammonia, argon nitrogen or hydrogen) and
– a precursor gas (such as acetylene, e thylene, ethanol or methane)
• Substrate is now heated to ~ 800°C
which initiate the growth of nanotubes
Chemical Vapour Deposition
Growth mechanism of CNT
Tip growth
Bottom growth
Growth Duration-
Experimental ApproachTo control the growth density of
cnt at constant temperature we
change the catalytic ratio for best
output. Ratio of catalysts-
Fe: Co 2:1
1:1
2:3
3:2
Role of catayst
• Surface to volume ratio
- A 30 nm particle only 5% on the surface
- A 10 nm particle 20% on the surface
- A 3 nm iron particle has 50% atoms on the surface
Redius of the range of 1.2 Ao
Crystalline arrangement With 30nm range
Chemical and physical structure of
CATALYST
Growth approach of CNT
MWCNTs grown at low temperatures and atmospheric pressure
, M. Kumar and Y. Ando, Carbon 43, 533
High quality TEM analysis at the time of experiment occur reported by –
reference cited
Solubility of catalyst with precursors-
Annealing
Oxidisation
at 600 oC
After C2H2
Ref - J. Phys. Chem. C 2009, 113, 1648–1656
• Formation of cnt depends over
temp as well as catalytic
solubility .
• A binding energy analysis xps
is shown here
Fe3C
Experimental approach during synthesis -
We analysed different parameter like ratio
and concentration of catalyst solution.
Independent catalytic conc.
i) Fe:Co 6:1 .12 : .02 gram/100ml.14g/100ml
ii) Fe:Co 3:1 .12:.04 gram/100ml .16g/100ml
iii) Fe:Co 2:1 .12:.06 gram/100ml .18g/100ml
iv) Fe:Co 2:3 .12:.08 gram/100ml .20g/100ml
v) Fe:Co 1:1 .
12:.12 gram/100ml .24g/100ml
Constant catalytic
i) Fe:Co 6:1
.1350 :026gram/100ml.16g/100ml
ii) Fe:Co 3:1 .12:04gram/100ml.16g/100ml
iii) Fe:Co 1:2..10:06gram/100ml.16g/100ml
iv) Fe:Co 1:1 .08:08gram/100ml.16g/100ml
v) Fe:Co 1:2
.05 :10gram/100ml.16g/100ml
Ratio of catalyst Fe:Co concentration
Experimental Result analysis
FeSEM (Field effect
scan electron microscopy)Raman Spectroscopy
Sem Result experiment 1-
Fig1Fe:Co: 3:1: Fig2Fe:Co: :2:1:
Fig3 Fe:Co 3:2
SEM images of CNT grown at .16/100 g/ml
catalytic concentration. a) 1um b) 500nm
Fig3 Fe:Co 3:2
sem image of highly dense
MWCNT from Sigma
Aldrich China
SEM images of CNT grown at .16/100 g/ml
catalytic concentration. a) 1um b) 500nm
Experiment 2-
Fig4 SEM image taken at a) 10um b) 2um resolutions CNT growth Fe:Co 1:1 with
.016/100 g/ml
.32mm
Analysis the length of differently grown CNT
-Reported as 0.32 mm
Raman analysis of catalytic environment CNT
growth.
Raman spectra of CNT
grown by exp. 1Raman spectra of CNT
grown by exp. 2
Result
• A complete SEM and Raman analysis show that the with
changing the concentration the diameter as well as quality
changes its.
• For prior concentration the diameter dicreses till a idealized
value (.16g/100) then due to diffusion hindrance the dia meter
of CNT drastically increase and quality goes down .
• SEM Analysis is used
for morphological analysis
and Raman is used for
Qualitative analysis (G and
D band.
Conclusion-
By the physical characterization of grown CNT
we can conclude that- CNT Synthesis not only depends upon catalyst, but orientation
of catalyst promoter also.
The quality of CNT (density, alignment , length, diameter ) are
better in condition with catalyst promoter.
This is only myth that catalyst are unaffected after reaction .
Post synthesis report shows that the iron particle reacts with
carbon and a certain part of carbon is made as Fe3C.
The high temperature converts metal oxide to metal which are
best for high quality CNT synthesis.
References• Topics in Applied Physics-
Carbon Nanotubes: Synthesis, Structure, Properties and Applications
M.S. Dresselhaus, G. Dresselhaus, Ph. Avouris
• Iijima S 1991- Nature 354-
• Effect of catalyst film thickness on carbon nanotube growth by
selective area chemical vapor deposition; Y. Y. Wei, Gyula Eres, V. I.
Merkulov, and D. H. Lowndes Citation: Applied Physics Letters 78, 1394
(2001); doi:10.1063/1.135465.
• N. Tripathi, P. Mishra, Harsh and S.S Islam, Physics of Semiconductor
Devices (Environmental Science and Engineering ), ;645 (2014).
• N. Tripathi, P. Mishra, Harsh and S.S Islam, Applied Nanoscience,; DOI
10.1007/s13204-013-0288-8(2014)
• review paper -Carbon Nanotube Synthesis and Growth Mechanism , Mukul
Kumar
Special thanks to fppt.com for ppt temples.
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