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

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