PREPARATION AND CHARACTERIZATION OF CNTs ON Co-Mo SUBSTRATE USING

CVD METHODNAME: SITI ROHAYU BINTI RUBAIDIMATRIC. NO: 1117322SUPERVISOR: DR. MA’AN FAHMI AL-KHATIBCO.SUPERVISOR: DR. SOUAD A.M. ALBAT’HI

Discovered : S. Iijima - MWNT (1991), SWNT (1993).

A tube-shaped material, made of carbon, having a diameter measuring on

the nanometer scale 1-100nm.

Perfection!!

Strongest and toughest

Stiffest

The best conductor

INTRODUCTION

PROBLEM STATEMENTSynthesis of CNTs have many methods and parameters such as the preparation of catalyst,

selecting the substrate and manipulating the process conditions of CNTs growth.

Despite there are many number of studies on CNTs, there are still unsolved issues regarding the

control of process for production of SWCNT.

In preparing CNTs, CVD equipment was used to obtain high yield and high purity of nanotubes.

Certain parameter such as concentration ratio of catalysts and reaction temperature during CNTs

growth were varied in order to get optimum growth of CNTs.

OBJECTIVES

The objectives of this research are:

To prepare bimetallic catalyst on silica substrate.

To optimize the growth of CNTs on indium tin oxide (ITO) by

varying process parameters such as concentration ratio of

bimetallic catalyst, reaction temperature and gas flow rate.

METHODOLOGYGeneral flow of the project

Preparation of bimetallic catalyst with substrate by dip coated method. The precursors of catalyst was mixed with ethanol solution

The CVD was set up and calcined catalyst was introduced in the middle of quartz tubular reactor.

Reduction step:Hydrogen was heated up to desired temperature (400◦C, 500◦C and 600◦C). The process took almost 20 to 35 minutes. For CNTs Growth, Argon was introduced up to 800◦C. At 800◦C, Carbon dioxide was introduced subsequently for 1 hour.

The process was cooled in Argon flow up to room temperature.

The CNTs were collected and characterized by SEM

The substrate was dried in drying oven or flowing air and calcined

Modification of CVD reactor.

The process was repeated until desired temperature was obtained

The project was divided into two parts:Preparation of catalyst on substrate• Process of cleaning substrate• Preparation of catalyst solutions on substrate

CNTs growth

Preparation of catalyst

A) Process of cleaning substrate

The glass of ITO was cleaned by using detergents, ethanol, acetone and distilled water.

The glass was dried in drying oven before proceeding to next step.

The glass was tested with multi meter to identify the surface that covered with ITO

The ITO glass was baked at 500◦C for 5 minutes

B) Preparation of catalyst solutions on substrate

Catalyst powder of Cobalt II Nitrate and Ammonium Heptamolybdate were weight based on desired ratio of catalyst concentration.

The catalyst solution dissolved in ethanol solution were mixed homogenously using magnetic stirrer

Different solution concentrations were tested and evaluated in the dip-coating process.

Coated catalyst of ITO glass substrate were placed in the crucible and dried in room temperature.

The glass substrates were baked in electrical furnace at 400◦C in 5 minutes.

CNTs growthThe tube was purged with Argon gas in 5 minutes.

Argon gas was switched off and hydrogen gas was introduced at flow rate 0.3 L/min. At the same time the reactor was heated from room temperature up to 400◦C/ 500◦C /600◦C .

Hydrogen gas was switched off and argon gas was again introduced at flow rate of 0.7 L/min and the reactor temperature was raised until 800◦C.

Consequently, carbon source which is carbon dioxide was introduced with flow rate 0.75 L/min n 1 hour.

Carbon dioxide flow was stopped and argon was introduced to cool down the sample until room temperature.

The sample was collected and kept in the desiccator.

RESULTS

Sample after calcination and reduction process using CVD machine

Weighed the sample Stored the sample in crucible and kept in the desiccator

Catalyst and substrates after calcination and reduction

400C 500C 600C0

0.2

0.4

0.6

0.8

1

1.2

2:01 3:04 1:03 3:02

Concentration ratio of catalyst

Yie

ld (m

g/m

g)

Yield = ( Weight of sample collected from CVD – Weight of calcined catalyst )

A) Carbon deposited in terms of increase of yield versus the concentration ratio of bimetallic catalyst

Weight of calcined catalyst

B) Decreasing weight of samples after collected from CVD reactor according to their respective temperature

350 400 450 500 550 600 6500

50

100

150

200

250

300

350

400

2:01

Linear (2:01)

3:04

1:03

3:02

Temperature (◦c)

WEI

GH

T O

F SA

MPL

ES C

OLL

ECTE

D F

RO

M C

VD

(MG

)

CHARACTERIZATION• Morphology of CNTs produced were studied using SEM analysis.

• Shown that CNTs grown were varied according their

concentration ratio of bimetallic catalyst with their respective

temperature

• SEM images revealed the sizes of tube diameter and length of

the tubes

Concentration of Co: Mo with ratio 1:3 at temperature 400◦C

Concentration of Co: Mo with ratio 1:3 at temperature 600 ◦C

• No growth of CNTs• Samples look like

accumulation of graphene flakes

• Formation long aligned Nano rods growth on the sample

• Diameter range 273.7 nm• Length range 12.4 µm

Concentration of Co: Mo with ratio 2:1 at temperature 400 ◦C

Concentration of Co: Mo with ratio 2:1 at temperature 600 ◦C

• Growth of disorder CNTs.• Diameter range 64.2 nm• Length range 13.5µm

• Formation long aligned Nano rods growth on the sample

• Diameter range 364.25 nm• Length range 14.7µm

Concentration of Co: Mo with ratio 3:4 at temperature 400 ◦C

• Formation long aligned Nano rods growth on the sample

• Diameter range 197.7 nm

• Length range 10.6 µm

No. Co : Mo Temperature reduction (◦C) Average diameter (nm) Average length

(µm)

1 1:3 400 416.3 12.7

2 1:3 600 273.7 12.4

3 2:1 400 64.2 13.5

4 2:1 600 364.25 14.7

5 3:4 400 197.7 10.6

Table 2. Average diameter of CNTs from the selected samples

Temperature (◦C) Co : Mo CNT characteristics

400 1:3 No CNTs growth

600 1:3 Non-uniform, long aligned

400 2:1 Agglomeration “spaghetti’ like

600 2:1 Non-uniform, long aligned

400 3:4 Non-uniform, long aligned

Table 1. CNTs growth characteristics on substrate with various catalyst ratio and temperature

CONCLUSION

Curly and entangled CNTs were formed from the process. The best result

shown during the concentration ratio of bimetallic catalyst with 2:1 of Co and

Mo respectively at 400◦C. Average diameter of CNTs ranges from 43.0 nm to

78.6 nm.

RECOMENDATIONS

Through the observation of this study, the following recommendation is made for further works:

Cooling of furnace after reaction by using electrical fan with round flexible duct. The time for cooling

may reduce from 14 hours to 10 hours.

Leaking of gas reactors can be overcome by using keck clamp that apply on the external surface

between quartz tube and caps.

Use variety of characterization for analysis sample such as XRD, FESEM and Uv-visible.

Use design expert software to analyze the result.