This thesis covers the analysis of catalytic growth of

carbon nanotubes (CNTs) under well-defined conditions,

the optimization of the catalyst and introduces model

for the growth mechanism based on the experimental

results. Experimental investigations are presented to

obtain a comprehensive picture on the catalytic growth

of CNTs. The overall aim of this thesis is to deposit CNTs

by the seeded catalyst method and the modified fluidized

floating catalyst method by Chemical Vapour Deposition

(CVD) and to investigate the effects of starting material

and catalysts on the morphology and structure of the

deposited CNTs. Camphor (C10H16O, crystalline state) and

camphor oil (liquid state) are the precursor materials used

as the source of CNTs. Transition metal (Fe, Ni, Co, Mn,

Al, Mg) catalysts were prepared and the effect on their

catalytic behavior were studied. Metal catalysts have

been prepared by sol-gel method with or without support

catalyst. Correlation between the catalyst particle size

and CNT diameter has been the motivation to reduce the

catalyst particle size down to nanoparticle size

Abd Aziz, Azira

Universiti Teknologi MARA Institutional Repository


10 I n s t i t u t e  o f  G r a d u a t e  S t u d i e s  ( I G S )
* (MS) = Main Supervisor
   (CS) = Co Supervisor
Name : Azira Binti Abd Aziz, PhD 
Title : Carbon Nanotubes Growth From 
  Camphoric Carbon Sources Using 
  Transition Metal Catalysts 
Faculty :  Applied Sciences
Supervisor : Associate Prof. Dr. Mohamad Rusop 
   Mahmood  (MS)
   Prof. Dr. Saifollah Bin Abdullah (CS)
14
This thesis covers the analysis of catalytic growth of 
carbon nanotubes (CNTs) under well-defined conditions, 
the optimization of the catalyst and introduces model 
for the growth mechanism based on the experimental 
results. Experimental investigations are presented to 
obtain a comprehensive picture on the catalytic growth 
of CNTs. The overall aim of this thesis is to deposit CNTs 
by the seeded catalyst method and the modified fluidized 
floating catalyst method by Chemical Vapour Deposition 
(CVD) and to investigate the effects of starting material 
and catalysts on the morphology and structure of the 
deposited CNTs. Camphor (C10H16O, crystalline state) and 
camphor oil (liquid state) are the precursor materials used 
as the source of CNTs. Transition metal (Fe, Ni, Co, Mn, 
Al, Mg) catalysts were prepared and the effect on their 
catalytic behavior were studied. Metal catalysts have 
been prepared by sol-gel method with or without support 
catalyst. Correlation between the catalyst particle size 
and CNT diameter has been the motivation to reduce the 
catalyst particle size down to nanoparticle size. Evolution 
of the catalyst particle size distribution during CNT synthesis 
is inevitable due to collision and evaporation of metal 
particles at high temperatures. In CVD the physical and 
chemical interactions between catalyst particle and 
support surface groups may be utilized in controlling the 
evolution of the particle size distribution. Physico-chemical 
properties of nanoparticles differ from the bulk values due 
to the high ratio of surface atoms to internal atoms. With 
varying catalyst loading with/without the catalyst support, 
the catalyst can form alloy and prevent the nanoparticles 
from segregating at high temperature. However, high 
fraction of the catalyst will form an isolated catalytic 
phase in the reduced catalyst. By controlling the mixture 
of catalyst can affect active catalyst particle, and also 
on the diameter of the CNTs. Catalytic carbon deposition 
reactions using camphor and camphor oil as the carbon 
containing feedstock have also been investigated over 
different type of transition metal catalyst with or without 
addition of support catalyst using seeded catalyst method 
and floating catalyst method. The CVD temperatures 
are varied between 650oC, 750oC and 850oC. Samples 
were characterized using a number of complementary 
techniques including, field emission scanning electron 
microscope (FESEM), Fourier Transmission Infrared (FTIR), 
X-ray diffraction (XRD) and Raman Spectroscopy. The 
findings from these techniques were used to explain the 
observed type and amount of carbon deposited.   The 
subsequent studies of the morphology of the carbon 
structures grown by CVD revealed a significant influence 
of the deposition temperature and the catalyst material 
on the quality of the carbon structures. Fe/Ni/Mn was 
Name : Mohd Zahid Bin Abidin, PhD
Title : Optimisation Of Emulsion-Based Edible 
  Coating And Development Of Coating 
  Applicator Machine For Postharvest Life 
  Study Of Guavas (Psidium Guajava L.)
Faculty :  Applied Sciences
Supervisor :  Associate Prof. Dr. Cheow Chong Seng (MS)
   Associate Prof. Dr. Norizzah Binti Abd 
   Rashid (CS)
13 Application of edible coating represents a method that 
can extend the shelf life of picked guava by minimising 
the weight loss mainly due to natural migration process of 
moisture and gases. Response surface methodology (RSM) 
was employed to search for best composition of edible 
coating comprised of three variables namely palm stearin, 
palm kernel olein and beeswax. The RSM was also used to 
investigate the influence of temperature of coating emulsion 
and dipping time on the coating pickup for the optimisation 
of coating process condition. From the RSM-generated 
model, optimum coating composition for minimising guava 
weight loss was 4.5% (w/v) palm stearin, 1% (w/v) palm kernel olein and 1% (w/v) beeswax. The RSM predicted and 
experimental weight loss (7%) were not significantly different from each other. The weight loss of uncoated guava was 
19% or 2.7 times higher than the coated guava as measured on the 7th day at ambient storage (25-27oC, RH 80-90%). 
The optimised process condition for coating application was at 63oC temperature of coating emulsion and 15 s dipping 
time in minimising the coating pickup to 0.15% by the coated guava. A coating applicator was designed, fabricated 
and evaluated based on dipping technique. It was built as a model to meet the functional requirement of coating 
application on guava fruits based on the optimised coating emulsion and process condition. The machine comprises 
of 7 major components, namely conveyor chain, motor, dipping tank, heater, blower, controller and receptacle. The 
coating applicator had an estimated coating capacity of at least 270 fruits/h and coating emulsion usage of 1 kg/1740 
guava fruits. Delay in senescence and metabolic activities of coated guava were indicated by lower changes in weight 
loss, firmness, surface colour development, titratable acidity, total soluble solid as well as CO2 concentration compared 
to uncoated guava. In terms of sensory evaluation, the panellists significantly (P<0.05) preferred the colour and texture 
of the coated guava and the sweetness and taste of the uncoated guava. However, the overall acceptability of the 
coated and uncoated guavas was comparable to each other evaluated on the 7th and 12th days at cold storage (12-
13oC, RH 80-90%). Coated guavas could be stored for up to 10 days at ambient condition and 30 days in cold storage. 
Application of emulsion-based edible coating developed in this study, in combination with coating applicator machine 
and cold storage seems to be a promising way to extend the storage life and marketability of the guava cultivar 
Vietnam/Cambodia; however, further work needs to be carried out on large scale trials prior to its commercial use.
Doctoral Research
Abstract
11L e a d i n g  Y o u  T o  G r e a t e r  H e i g h t ,  D e g r e e  b y  D e g r e e
* (MS) = Main Supervisor
   (CS) = Co Supervisor
Name : Suriani Binti Abu Bakar, PhD
Title : Controlled Growth Of Vertically Aligned 
  Carbon Nanotubes From Palm Oil Precursor 
  Using Thermal Chemical Vapour 
  Deposition Method And Its Field Electron 
  Emission Properties
Faculty :  Applied Sciences
Supervisor :  Associate Prof. Dr. Mohamad Rusop 
   Mahmood (MS)
   Prof. Dr. Saifollah Bin Abdullah (CS)
   Associate Prof. Dr. Roslan Bin Md Nor  
   (CS)
15
Vertically aligned carbon nanotubes (VACNT) were 
synthesized using palm oil as an environmentally friendly 
starting material. The synthesis was carried out in a thermal 
chemical vapour deposition reactor. Parametric studies 
were done to determine the optimum parameters to 
obtain VACNT with favourable properties at high volume. 
The parameters included seeded and floated catalyst 
preparation method, stacking substrate configuration 
(lower and upper growth), synthesis temperature (700- 
900°C), palm oil vaporization temperature (300-600°C), 
synthesis time (5-90 min), different carbon precursor (palm 
oil and waste cooking palm oil), substrate positioning 
(position 1-6), ferrocene concentration (0.67-5.33 wt%) 
and different carrier gas (argon and nitrogen). The carbon 
nanotubes (CNT) products were then characterized 
using several analytical techniques which were electron 
microscopy, energy dispersive x-ray analysis, micro-
Raman and Fourier transform infrared (FTIR) spectroscopy, 
thermogravimetry analysis (TGA) and CHNS-O analysis. 
Prior to the synthesis process, several analyses such as 
TGA, gas chromatography–mass spectrometry and FTIR 
characterizations were done on the carbon precursor 
namely palm oil and waste cooking palm oil in order to 
facilitate the optimization procedures of VACNT. For every 
synthesis parameter, the nanotubes growth rates were 
measured and the nucleation as well as termination factor 
were investigated. CNT diameter, degree of alignment, 
crystallinity and purity were extensively studied as they were 
found to be greatly affected by the synthesis parameters. 
Based on the inspection of the morphology and crystallinity 
of CNT it was found that the following parameters can be 
considered as the optimized parameter to produce higher 
quality of bulk VACNT in our reactor; the floated catalyst 
and lower growth approach at the synthesis temperature 
in range of 750-800oC, precursor vaporization temperature 
in the range of 400-500°C, the synthesis temperature of 15 
to 35 mins, sample position at P2 and P3, and ferrocene 
concentration of 1.33 - 5.33 wt%. Synthesizing VACNT 
within nitrogen ambient produces higher VACNT growth 
rate with considerably more bamboo-liked structure as 
compared to argon ambient. In this study, we have also 
demonstrated that waste cooking palm oil from domestic 
frying can be utilized as an efficient, economical and 
environmentally friendly carbon source for VACNT and bulk 
CNT synthesis. A mixed bottom-tip growth model has been 
proposed for the floated catalytic CVD synthesis with the 
bottom growth mechanism was believed to take place 
in the early stage of the synthesis. The VACNT growth can 
also be initiated by the yarmulke growth mechanism. The 
yarmulke growth has been used to explain the presence 
of tubes with bamboo-type structure. By examining CNT 
synthesized under different conditions, it was found that 
an amorphous carbon coating of roughly 8 nm within 6 
min synthesis time was sufficient to completely terminate 
the growth. However in a controlled condition, the growth 
was not expected (not) to terminate even though for 
1 hour synthesis time. We also assessed the potential of 
palm oil based VACNT as field emitter by measuring its 
field electron emission (FEE) properties. Field emission from 
the VACNT synthesized within nitrogen ambient at 2.5 
wt% ferrocene concentration indicated the lowest turn-
on field at 2.95 Vµm-1 which corresponded to the current 
density of 10 µAcm-2. The threshold field was observed to 
be about 3.55 Vµm-1 at 1 mAcm-2. The maximum current 
density of 7.30 mAcm-2 measured was obtained for 4.30 
Vµm-1 and good emission stability with low degradation. 
Electrode separation of 200 µm gave the best FEE 
performance and smaller or larger electrode separations 
gave inferior results. It can be concluded that the VACNT 
from the bio-hydrocarbon precursor palm oil was stable 
for applications in field emission devices such as flat panel 
displays and flat lamps.
found to be the most active catalyst to deposit CNTs by using camphor while Fe/Co/Al with ratio (1:2:1) was found to 
be the most active catalyst for camphor oil using seeded catalyst method with the deposition temperature of 850oC. 
However, high quality CNTs have been produced by fluidized floating catalyst method in which the precursor (camphor 
oil) and the catalyst Fe/Ni/Mg are placed in the same boat at moderate temperature of 650oC. The activity of metal 
catalyst was found to be dependent on a number of factors; mass of the catalyst, deposition temperature and type of 
precursor. It was found, in all cases that increasing deposition temperature resulted in higher deposition rates. Based on 
those experimental results a mechanism for the growth of CNTs is suggested. Carbon precursor dissociated catalytically 
on the catalyst nanoparticles spread on the catalyst boat. In the first stage, the carbon material reduces the metal oxide 
nanoparticles to pure metal. The further catalytic dissociation of carbon material presumably takes place at facets of 
well-defined crystallographic orientation and the carbon diffuses into the particle. The resulting density gradient of carbon 
dissolved in the particle drives the diffusion of carbon through the particle. In order to avoid dangling bonds, the carbon 
atoms assemble at a less reactive facet of the particle, which leads to the formation of a nanotube. Thicker nanotubes 
at higher temperatures are generated due to the dissociation of carbon material in the gas phase, which leads to the 
formation of carbon molecules that condense on the catalytically grown structures. Strong catalyst interaction between 
the catalysts is thought to be the dominant factor in improving the nanotube growth. In addition, the formation of a 
catalyst alloy is also possible in enhancing reactivity of the catalyst for the optimum growth of CNTs.


Carbon nanotubes growth from camphoric carbon sources using transition metal catalysts / Azira  Abd Aziz

http://ir.uitm.edu.my/19077/1/ABS_AZIRA%20ABD%20AZIZ%20TDRA%20VOL%201%20IGS%2012.pdf

Carbon nanotubes growth from camphoric carbon sources using transition metal catalysts / Azira Abd Aziz

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