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UNIVERSITI PUTRA MALAYSIA
SITI HAJAR BINTI OTHMAN
FK 2011 147
CHARACTERIZATION AND DISPERSION BEHAVIOR OF TITANIUM DIOXIDE AS PHOTOCATALYTIC NANOPARTICLES USING METAL
ORGANIC CHEMICAL VAPOUR DEPOSITION SYSTEM
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CHARACTERIZATION AND DISPERSION
BEHAVIOR OF TITANIUM DIOXIDE AS
PHOTOCATALYTIC NANOPARTICLES USING
METAL ORGANIC CHEMICAL VAPOUR
DEPOSITION SYSTEM
SITI HAJAR BINTI OTHMAN
DOCTOR OF PHILOSOPHY
UNIVERSITI PUTRA MALAYSIA
2011
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CHARACTERIZATION AND DISPERSION BEHAVIOR OF TITANIUM
DIOXIDE AS PHOTOCATALYTIC NANOPARTICLES USING METAL
ORGANIC CHEMICAL VAPOUR DEPOSITION SYSTEM
By
SITI HAJAR BINTI OTHMAN
Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia,
in Fulfilment of the Requirements for the Degree of Doctor Philosophy
December 2011
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To my beloved parents for their great sacrifice..
To my dear husband and son for completing my
life..
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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment
of the requirement for the degree of Doctor Philosophy
CHARACTERIZATION AND DISPERSION BEHAVIOR OF TITANIUM
DIOXIDE AS PHOTOCATALYTIC NANOPARTICLES USING METAL
ORGANIC CHEMICAL VAPOUR DEPOSITION SYSTEM
By
SITI HAJAR BINTI OTHMAN
December 2011
Chair: Suraya Abdul Rashid, PhD
Faculty: Faculty of Engineering
Metal organic chemical vapour deposition (MOCVD) is a favourable technique to
synthesize nanoparticles owing to the relative ease and simplicity of the process. In
the MOCVD system, the presence of heat decomposes gaseous reactants to form a
stable solid product. The motivation of the present work was to study the synthesis,
doping, characterization, dispersion, and photocatalytic properties of TiO2
nanoparticles synthesized via MOCVD. Computational fluid dynamics (CFD)
simulation was utilized to provide better understanding on the MOCVD synthesis
system as well as fluid dynamics inside the reactor.
It was found that deposition temperature plays an important role in determining the
properties of the synthesized TiO2 nanoparticles such as particle size and
crystallinity. Crystallinity was determined to have significant influence on
photocatalytic activity compared to particle size. The nanoparticles heat treated at
temperatures higher than or equal to the deposition temperature had improved
photocatalytic activity. Thus, it was deduced that the choice of heat treatment
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temperature should be made in view of the deposition temperature. Fe doping was
found to promote the phase transition, slightly decrease the particle size, and enhance
the absorption of TiO2 nanoparticles in the visible spectrum. However, the
photocatalytic activity decreased due to the unfavourable location of Fe ion inside
the interior matrix of the TiO2 nanoparticles rather than on the exterior surface.
For the dispersion study, rupture followed by erosion was determined to be the main
break up mechanisms when ultrasonication was employed. 3 weight% of polyacrylic
acid with average molecular weight of 2000 g/mol was determined to produce the
best dispersion and most stable suspension. The coatings were confirmed to be
photocatalytically active.
Finally, the CFD simulation results indicate that increasing deposition temperature
and reducing carrier gas flowrate increases the surface deposition rate and the
amount of TiO2 nanoparticles produced. Temperature plays remarkable part in
determining the rate of surface deposition of TiO2 nanoparticles compared to carrier
gas flowrate. Flow recirculations were found to occur in the reactor due to protrusion
and large temperature gradient. Good mixing of N2 and O2 gases is important to
ensure the deposition uniformity. Good agreement between experimental and
simulation results lends support to the reliability of the simulations work.
In conclusion, this work opens the window towards improving and optimizing the
synthesis process of nanoparticles via MOCVD method as well as offers knowledge
on the dispersion and stabilization of nanoparticles towards advancement for
industrial applications.
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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai
memenuhi keperluan untuk ijazah Doktor Falsafah
PENCIRIAN DAN SIFAT PENYERAKAN TITANIUM DIOKSIDA SEBAGAI
NANOPARTIKEL FOTOKATALITIK MENGGUNAKAN SISTEM
PENGENAPAN WAP KIMIA LOGAM ORGANIK
Oleh
SITI HAJAR BINTI OTHMAN
Disember 2011
Pengerusi: Suraya Abdul Rashid, PhD
Fakulti: Fakulti Kejuruteraan
Pengenapan wap kimia logam organik (MOCVD) adalah teknik yang digemari untuk
mensintesis nanopartikel relatif dengan kemudahan dan kesederhanaan proses
tersebut. Dalam proses MOCVD, kehadiran haba menguraikan gas bahan tindak
balas untuk membentuk produk pepejal yang stabil. Motivasi kerja ini adalah untuk
mengkaji sintesis, pengedopan, pencirian, penyebaran, dan sifat-sifat fotokatalitik
nanopartikel TiO2 yang disintesis menggunakan MOCVD. Simulasi pengiraan
dinamik bendalir (CFD) digunakan untuk memberikan pemahaman yang lebih baik
mengenai sistem sintesis MOCVD serta dinamik bendalir di dalam reaktor.
Suhu pengenapan didapati memainkan peranan penting dalam menentukan sifat-sifat
nanopartikel TiO2 yang disintesis seperti saiz partikel dan kristaliniti. Kristaliniti
didapati mempunyai pengaruh yang besar ke atas aktiviti fotokatalitik berbanding
saiz partikel. Terdapat peningkatan dalam aktiviti fotokatalitik nanopartikel yang
dirawat pada suhu yang lebih tinggi daripada atau sama dengan suhu pengenapan.
Kesimpulannya, pemilihan suhu rawatan haba perlu dibuat berpandukan suhu
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pengenapan. Pengedopan Fe didapati menggalakkan peralihan fasa, mengurangkan
sedikit saiz partikel, dan meningkatkan penyerapan nanopartikel TiO2 ke spektrum
boleh lihat. Walau bagaimanapun, aktiviti fotokatalitik berkurangan kerana lokasi ion
Fe
yang tidak diingini iaitu di dalam matriks dalaman nanopartikel TiO2 dan
bukannya pada permukaan luaran.
Untuk kajian penyerakan, didapati bahawa pemecahan diikuti oleh hakisan adalah
mekanisme utama penggunaan ultrasonik. 3% berat asid poliakrilik dengan purata
berat molekular 2000 g/mol didapati dapat menghasilkan penyerakan yang terbaik
dan ampaian yang paling stabil. Saduran telah disahkan aktif fotokatalitik.
Akhir sekali, keputusan simulasi CFD menunjukkan bahawa kadar permukaan
pengenapan dan jumlah nanopartikel TiO2 yang dihasilkan meningkat dengan
peningkatan suhu pengenapan dan pengurangan kadar aliran gas pembawa. Suhu
memainkan peranan yang penting dalam menentukan kadar permukaan pengenapan
nanopartikel TiO2 berbanding kadar aliran gas pembawa. Aliran edaran semula
didapati berlaku di dalam reaktor kerana jorokan dan perbezaan suhu yang besar.
Percampuran yang baik antara gas N2 dan O2 adalah penting untuk memastikan
keseragaman pengenapan. Persamaan yang baik antara keputusan ujikaji dan
simulasi menyokong kredibiliti kerja simulasi.
Kesimpulannya, kerja ini membuka peluang ke arah memperbaiki dan
mengoptimumkan proses sintesis nanopartikel menerusi kaedah MOCVD serta
menawarkan pengetahuan mengenai penyerakan dan kestabilan nanopartikel ke arah
kemajuan untuk aplikasi perindustrian.
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ACKNOWLEDGEMENTS
I would like to extend my deepest gratitude and appreciation to my supervisor Assoc.
Prof. Dr. Suraya Abdul Rashid for her excellence supervision, continuous support,
invaluable advice, encouragement, motivation, and patience. Her guidance has
helped me throughout my research and writing up of this thesis. My special thanks
and appreciation also goes to the rest of my supervisory committee members, Dr.
Tinia Idaty Mohd Ghazi and Assoc. Prof. Dr. Norhafizah Abdullah for their
constructive suggestions, insightful comments, helps, and encouragement. Without
my supervisory committee, this research work would not have been possible.
My sincere thanks also goes to all my friends and colleagues especially Zi Kang,
David, Kak Azian, Kak Sharifah, Kak Ferra, Kak Zila, Kak Shanti, Mai, Pak
Darmadi, Pak Azhari, Pak Muhammad, Chong, and others for their helps, constant
support, encouragement, joy, and laughter. Deep thanks to the staff members of
Department of Chemical and Environmental Engineering Laboratories, Institute of
Bioscience Laboratories, and Institute of Advanced Technology Laboratories for
their continuous assistance and technical expertise. I am also grateful to the
Universiti Putra Malaysia for giving me the opportunity to pursue my PhD study and
for providing financial support under the Fundamental Research Grant Scheme (Vote
No.: 5523426 and 5523767). Big thanks to Higher Minister Education of Malaysia
for offering me the scholarship in pursuing my PhD study. Also, sincere thanks to
Mr. Zamir Abdul Rashid for his precious advices, expertise, and helps on simulations
work.
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My heartfelt and sincere appreciation also goes to my family; Mak, Abah, Kakak,
Lin, Min, parents in law, sisters in law, brothers in law, niece, nephews, and relatives
for their love, support, patience, and prayers for me to reach this stage. Not to forget,
Al-Fatihah for Allahyarhamah Sharifah Alawiyah Binti Syed Mahmood, my much-
loved Emak. She will be remembered dearly. Last but not least, my undivided love
and warmest gratitude goes to my loving, caring, understanding, and wonderful
husband, Mohammad Hilmi Bin Kassim for his patience, comforting support,
encouragement, and prayers throughout my study. To my dear son, Hafiy Imaan,
thank you for being such a good baby throughout my thesis writing journey. His
presence has made my thesis writing journey more pleasurable.
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I certify that a Thesis Examination Committee has met on 2 December 2011 to
conduct the final examination of Siti Hajar binti Othman on her thesis entitled
“Characterization and Dispersion Behavior of Titanium Dioxide as Photocatalytic
Nanoparticles Using Metal Organic Chemical Vapour Deposition System” in
accordance with the Universities and University Colleges Act 1971 and the
Constitution of the Universiti Putra Malaysia [P.U.(A) 106] 15 March 1998. The
committee recommends that the student be awarded the Doctor of Philosophy.
Members of the Thesis Examination Committee were as follows:
Luqman Chuah Abdullah, PhD
Professor
Faculty of Engineering
Universiti Putra Malaysia
(Chairman)
Zulkarnain bin Zainal, PhD
Professor
Faculty of Science
Universiti Putra Malaysia
(Internal Examiner)
Dayang Radiah binti Awang Biak, PhD
Senior Lecturer
Faculty of Engineering
Universiti Putra Malaysia
(Internal Examiner)
Ng Ka Ming, PhD
Professor
The Hong Kong University of Science and Technology
China
(External Examiner)
________________________________________
BUJANG KIM HUAT, PhD
Professor and Deputy Dean
School of Graduate Studies
Universiti Putra Malaysia
Date:
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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been
accepted as fulfilment of the requirement for the degree of Doctor of Philosophy.
The members of the Supervisory Committee were as follows:
Suraya Abdul Rashid, PhD
Associate Professor
Faculty of Engineering
Universiti Putra Malaysia
(Chairman)
Norhafizah Abdullah, PhD
Associate Professor
Faculty of Engineering
Universiti Putra Malaysia
(Member)
Tinia Idaty Mohd Ghazi, PhD
Senior Lecturer
Faculty of Engineering
Universiti Putra Malaysia
(Member)
________________________________
BUJANG BIN KIM HUAT, PhD
Professor and Dean
School of Graduate Studies
Universiti Putra Malaysia
Date:
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DECLARATION
I declare that the thesis is my original work except for quotations and citations which
have been duly acknowledged. I also declare that it has not been previously, and is
not concurrently, submitted for any other degree at Universiti Putra Malaysia or at
any other institution.
___________________________
SITI HAJAR BINTI OTHMAN
Date: 2 December 2011
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LIST OF TABLES
Table
2.1 Detail properties of Degussa P25
(Source: Evonik Industries)
2.2 Brief literature review on the synthesis, characterization, and
photocatalytic properties of TiO2 nanoparticles
2.3 Relationship between zeta potential value and stability
behaviour of the dispersion
(Source: Shimadzu UV-1650 PC Spectrophotometer User
Guide)
3.1 Molecular structure, molecular formula, molecular weight,
and boiling point of both the TBOT and TTIP precursors
(Source: Sigma-Aldrich)
3.2 Reactions considered in the model along with the activation
energy and pre-exponential factors values of TTIP
4.1 The rate constant values of TiO2 nanoparticle samples
with and without heat treatment and the mean nanoparticle
diameter determined from SEM, TEM, and XRD
4.2 The surface area, mean nanoparticle diameter, and rate
constant values of TiO2 nanoparticle samples deposited at
different temperatures and different carrier gas flowrates
including the commercial Degussa P25
4.3 Effect of amount of Fe dopant on the surface area, mean
nanoparticle diameter, percentage of anatase and rutile
crystal structure, bandgap energy, and rate constant values of
TiO2 nanoparticle samples deposited at 700°C including the
commercial Degussa P25
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LIST OF FIGURES
Figure
2.1 Simplified Reaction Scheme of the Photocatalytic Reaction
of TiO2 Nanoparticles
(Source: Adapted from Benedix et al., 2000)
2.2 Diagram of the Anatase and Rutile Crystal Structure
(Source: Farrell, 2001)
2.3 Production Process of the Main Commercial TiO2
Nanoparticles, Degussa P25
(Source: Evonik Industries)
2.4 Simplified Reaction Scheme of the Photocatalytic Reaction
of Fe-doped TiO2 Under UV and Visible Light
(Source: Adapted from Tong et al., 2008)
2.5 Crystal Structure of Fe-doped TiO2 with a Ti Atom
Displaced by a Fe Impurity Atom
(Source: Zhang et al., 2006)
2.6 MOCVD Reactor Setup (MFC - Mass Flow
Controller)
(Source: Backman et al., 2005)
2.7 A Schematic Illustration of the Key CVD Steps During
Deposition
(Source: Choy, 2003)
2.8 Schematic of Deposition Process
(Source: Adapted from Backman et al., 2005)
2.9 Schematic Illustration of Particle Generation Process by Gas-
Phase Reaction
(Source: Nakaso et al., 2001)
2.10 Schematic Presentation of Break Up Mechanism
(Source: Padron et al., 2008)
2.11 Particle Size Distributions for Different Break Up Modes
(Source: Özcan-Taşkin et al., 2009)
2.12 Electrical Double Layer Surround a Negatively Charged
Particle
(Adapted from: Stanford Microfluidics Laboratory)
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2.13 The Relationship Between Zeta Potential and Surface
Potential
(Source: Zeta-Meter)
2.14 Dispersant Attachments on Particle in Aqueous Suspension
(Source: Vernardakis, 2007)
2.15 Dissociation of Polyacrylic Acid in Aqueous Solution
2.16 Illustration of Dispersion Mechanism of TiO2 Particles in
PAA Aqueous Suspension
(Source: Ran et al., 2007)
3.1 Summary of Methodology
3.2 Experimental Setup of MOCVD Reactor
3.3 Experimental Setup of Photocatalytic Reactor
3.4 Summary of Methodology for Photocatalytic Activity of
Coatings Study
3.5 Geometry of the Simplified MOCVD Reactor and its
Schematic Representation. All the Measurements are in
Metre (m)
4.1 SEM Micrographs (Left) and Corresponding Particle Size
Distribution Histograms (Right) of TiO2 Nanoparticle
Samples Deposited at (a) 400°C, (b) 500°C, (c) 600°C, and
(d) 700°C without Postdeposition Heat Treatment
4.2 XRD Patterns of TiO2 Nanoparticle Samples Deposited at
Various Deposition Temperatures without Postdeposition
Heat Treatment
4.3 TGA Curve of TiO2 Nanoparticle Sample Deposited at
700°C without Postdeposition Heat Treatment and the
Presence of O2 Feed
4.4 TEM Micrographs (Left) and Corresponding Particle Size
Distribution Histograms (Right) of TiO2 Nanoparticle
Samples Deposited at (a) 700°C, (b) 700°C Heat Treated at
400°C, and (c) 700°C Heat Treated at 700°C
4.5 XRD Patterns of TiO2 Nanoparticle Samples Deposited at
Different Deposition Temperatures with and without Heat
Treatment - (a) 300°C (b) 400°C (c) 500°C (d) 600°C (e)
700°C, and (f) XRD Patterns for All Samples Deposited at
Different Temperatures, Heat Treated at 400°C
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4.6 Photocataytic Activity of TiO2 Nanoparticle Samples
Deposited at Different Deposition Temperatures with and
without Heat Treatment - (a) 300°C (b) 400°C (c) 500°C (d)
600°C (e) 700°C, and (f) Photocatalytic Activity of Samples
Deposited at Different Deposition Temperatures and Heat
Treated at 400°C. Graphs Fitted with Linear Trendline from
Which the Rate Constants Were Determined. TiO2 Loading:
0.02 g, Concentration of Methylene Blue: 6 ppm
4.7. TGA Curve of TiO2 Nanoparticle Sample Deposited at
700°C with the Presence of O2 Feed
4.8 Spectras of (a) EDX and (b) XPS of TiO2 Nanoparticle
Sample
4.9 TEM Micrographs (Left) and Corresponding Particle Size
Distribution Histograms (Right) of TiO2 Nanoparticle
Samples Deposited at (a) 400°C, (b) 500°C, (c) 600°C, (d)
700°C, (e) 800°C, and (f) 900°C
4.10 XRD Patterns of TiO2 Nanoparticle Samples Deposited at
Different Temperatures - (a) 400°C, (b) 500°C, (c) 600°C,
(d) 700°C, (e) 800°C, and (f) 900°C
4.11 Photocatalytic Activity of TiO2 Nanoparticle Samples
Deposited at Different Deposition Temperatures - (a) 400°C
(b) 500°C (c) 600°C (d) 700°C (e) 800°C, and (f) 900°C.
Graph Fitted with Linear Trendline from Which the Rate
Constants Were Determined. TiO2 Loading: 0.02 g,
Concentration of Methylene Blue: 6 ppm
4.12 TEM Micrographs (Left) and Corresponding Particle Size
Distribution Histograms (Right) of TiO2 Nanoparticle
Samples Deposited at 700°C with Carrier Gas Flowrate of (a)
200 mL/min, (b) 400 mL/min, and (c) 600 mL/min
4.13 XRD Patterns of TiO2 Nanoparticle Samples Deposited at
700°C with Different Carrier Gas Flowrates - (a) 200
mL/min, (b) 400 mL/min, and (c) 600 mL/min
4.14 Photocatalytic Activity of TiO2 Nanoparticle Samples
Deposited at 700°C with Different Carrier Gas Flowrates -
(a) 200 mL/min (b) 400 mL/min, and (c) 600 mL/min. Graph
Fitted with Linear Trendline from Which the Rate Constants
Were Determined. TiO2 Loading: 0.02 g, Concentration of
Methylene Blue: 6 ppm
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4.15 TEM Micrograph (Left) and Corresponding Particle Size
Distribution Histogram (Right) of TiO2 Nanoparticle
Samples Deposited at 700°C with Carrier Gas Flowrate of
400 mL/min Using TTIP Precursor
4.16 XRD Pattern of TiO2 Nanoparticle Sample Deposited at
700°C with Carrier Gas Flowrate of 400 mL/min using TTIP
Precursor
4.17 Photocatalytic Activity of TiO2 Nanoparticle Samples
Deposited at 700°C with Carrier Gas Flowrate of 400
mL/min Using TBOT and TTIP Precursors. Graph Fitted
with Linear Trendline from Which the Rate Constants Were
Determined. TiO2 Loading: 0.02 g, Concentration of
Methylene Blue: 6 ppm
4.18 EDX Spectras of Undoped and Fe-doped TiO2 Nanoparticle
Samples
4.19 XPS Spectras of Undoped and Fe-doped TiO2 Nanoparticle
Samples
4.20 TEM Micrographs (Left) and Corresponding Particle Size
Distribution Histograms (Right) of TiO2 Nanoparticle
Samples Deposited at (a) 400°C - 0.01 g Fe Dopant, (b)
400°C - 0.05 g Fe Dopant, (c) 700°C - 0.01 g Fe Dopant, and
(d) 700°C - 0.05 g Fe Dopant
4.21 XRD Patterns of Undoped and Fe-Doped TiO2 Nanoparticle
Samples Deposited at (a) 400°C and (b) 700°C. (i) Undoped,
(ii) 0.005 g Fe Dopant, (iii) 0.01 g Fe Dopant, (iv) 0.03 g Fe
Dopant, and (v) 0.05 g Fe Dopant
4.22 Diffuse Reflectance Spectra of Undoped and Fe-doped TiO2
Nanoparticle Samples Deposited at 700°C Including Degussa
P25
4.23 Photocatalytic Activity of Undoped and Fe-Doped TiO2
Nanoparticle Samples Including Degussa P25 Under (a) UV
Light Illumination and (b) Fluorescent Lamp. Graphs Were
Fitted With Linear Trendlines from Which the Rate
Constants Were Determined. TiO2 Loading: 0.02 g,
Concentration of Methylene Blue: 6 ppm
4.24 (a) Particle Size Distribution and (b) Zeta Potential Plot for
Different Ultrasonication Amplitude Values
4.25 Effect of Type and Amount of Dispersant on the Average
Cluster Size of TiO2 Suspensions
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4.26 Effect of Optimum Dispersant Addition on the Particle Size
Distribution of TiO2 Suspensions
4.27 Effect of Type of Dispersant and Amount of Dispersant on
the Zeta Potential of TiO2 Suspensions
4.28 TEM Micrographs of TiO2 Nanoparticles Extracted from the
Suspensions Prepared (a) without Ultrasonication, (b) with
the Aid of Ultrasonication, and (c) with Dispersant Addition
4.29 Photos of TiO2 Nanoparticle Suspensions on (a) Day 1, (b)
Week 1, (c) Week 2, (d) Week 3, (e) Week 4, (f) Week 5, (g)
Week 6, and (h) Week 8
4.30 FTIR Spectra of TiO2 Nanoparticles Before and After
Adsorption of PAA2000
4.31 EDX Spectra of TiO2 Coatings Prepared (a) without
Dispersant and (b) with PAA 2000 Dispersant Addition
4.32 Percentage Degradation of Formaldehyde Gas of TiO2
Coatings Produced from the Suspensions Prepared without
Dispersant and with Optimum Dispersant Addition Under
UV Light Irradiation. TiO2 Loading: 0.05 g TiO2 in 100 mL
Distilled Water, Initial Concentration of Formaldehyde Gas:
2 ppm
4.33 Temperature Profiles Along the Reactor for M-R, S-R, and
S+R
4.34 (a) Temperature Contours from Isometric, Top, Bottom,
Right, Left, and Middle Plane Point of View and (b) Radial
Temperature Contours at z = 0.890, 0.178, 0.280, 0.478, and
0.640 mm
4.35 Velocity Profiles Along the Reactor for S-R and S+R. Each
Hump in the Velocity Profiles of S-R is Matched with a
Recirculation Loop in the Velocity Vector Profile (Middle
Plane of View) and Radial Velocity Vector Profiles of S-R at
z = 0.060, 0.190, 0.280, 0.460, and 0.720 m (z Points of Five
Humps)
4.36 Figure 4.36. Velocity Contour and Velocity Vector from
Middle Plane Point of View (a) Inlet Region, (b) Heated
Region, and (c) Outlet Region as well as (d) Radial Velocity
Vector at z = 0.089, 0.178, 0.280, 0.478, and 0.640 m
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4.37 (a) Contours of Mass Fractions of N2 and O2 Chemical
Species from Middle Plane Point of View and (b)
Streamlines of N2 and O2 Gases from Isometric, Top,
Bottom, Right and Left Point of View
4.38 Mass Fraction Contours of TBOT, TiO2(g), C4H8, and
C4H9OH from the Middle Plane Point of View
4.39 (a) Kinetic Rates of Reactions 1 and 2, and (b) Surface
Deposition Rate of TiO2(s)
4.40 (a) Temperature and (b) Velocity Profiles Along the Centre
Line of the Reactor and from the Middle Plane Point of View
with Varying Deposition Temperatures
4.41 Mass Fraction Profiles of a) TBOT, (b) TiO2(g), (c) C4H8,
and (d) C4H9OH from the Centre Line of the Reactor with
Varying Deposition Temperatures
4.42 (a) Kinetic Rates of Volumetric Reaction 1, (b) Kinetic Rates
of Volumetric Reaction 2, (c) Maximum Kinetic Rate of
Surface Reactions 3 and 4, and (d) Maximum Surface
Deposition Rate Along with the Surface Deposition Rate
Contours of TiO2(s) with Varying Temperature
4.43 Velocity Profiles Along the Centre Line of the Reactor and
from the Middle Plane Point of View with Varying Carrier
Gas Flowrate
4.44 (a) Maximum Kinetic Rate of Volumetric Reactions 1 and 2,
(b) Maximum Kinetic Rate of Surface Reactions 3 and 4, and
(c) Maximum Surface Deposition Rate Along with the
Contours of Surface Deposition Rate of TiO2(s) with Varying
Carrier Gas Flowrate
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LIST OF SYMBOLS
𝑎 Absorbance
A Pre-exponential factor
cp Specific heat capacity
C Concentration
Co Initial concentration
D Diameter
E Thermodynamic internal energy
Ea Activation energy
fA Fraction of anatase crystal structure
G Gibbs free energy
ΔG Gibbs free energy difference
h Enthalpy
ℎ𝑣 Photon energy
I Unit tensor
IA X-ray intensities of the anatase (1 0 1) diffraction peak
IR X-ray intensities of the rutile (1 1 0) diffraction peak
J Diffusion flux of species
k Rate constant
kH Heat conduction coefficient
K Constant
M Results obtained manually
Mw Average molecular weight
P Pressure
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R Gas constant
Re Reynold numbers
-R Without chemical reaction
+R With chemical reaction
S Results obtained from CFD simulation
SA Surface area
T Temperature
v Vector velocity
Vavg Average velocity
Y Mass fraction
β Corrected band broadening
θ Diffraction angle
λ Wavelength
μ Viscosity
ρ Density
ρg Gravitional body force
Stress tensor
Subscript j Species j
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LIST OF ABBREVIATIONS
fwhm Full width at half-maximum
i.e.p. Isoelectric point
BET Brunauer-Emmett-Teller
CFD Computational fluid dynamics
CVD Chemical vapour deposition
DDL Diacetyldihydrolutidine
DRS UV-vis diffuse reflectance spectrophotometer
EDX Energy x-ray dispersive spectroscopy
EELS Electron energy loss spectroscopy
FTIR Fourier transform infrared
GRAS Generally regarded as a safe material
HTC Heat transfer coefficient
MOCVD Metal organic chemical vapour deposition
PAA Polyacrylic acid
SAXS Small angle X-ray scattering
SEM Scanning electron microscope
STEL Short term exposure limit
TBOT Titanium (IV) butoxide
TEM Transmission electron microscope
TGA Thermogravimetry
TTIP Titanium isopropoxide
UV Ultraviolet
XPS X-ray photoelectron spectroscopy
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XRD X-ray diffraction
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TABLE OF CONTENTS
ABSTRACT
ABSTRAK
ACKNOWLEDGEMENTS
APPROVAL
DECLARATION
LIST OF TABLES
LIST OF FIGURES
LIST OF SYMBOLS
LIST OF ABBREVIATIONS
CHAPTER
1 INTRODUCTION
1.1 Background
1.2 Problem Statement
1.3 Objectives and Scope of Work
1.4 Research Contributions
1.5 Thesis Outline
2 LITERATURE REVIEW
2.1 Titanium Dioxide
2.1.1 Photocatalytic Reaction of TiO2 Nanoparticles
2.1.2 Photocatalytic Properties of TiO2
Nanoparticles
2.1.3 Commercial TiO2 Nanoparticle (Degussa P25)
2.2 Fe-doped TiO2
2.2.1 Photocatalytic Reaction of Fe-doped TiO2
2.2.2 Fe Doping Mechanism
2.3 Metal Organic Chemical Vapour Deposition
2.3.1 MOCVD Reactor System
2.3.2 MOCVD Processes
2.4 Dispersion and Stabilization for Coating Applications
2.4.1 Dispersion Mechanism
2.4.2 Stabilization Mechanism
2.5 Computational Fluid Dynamics Simulation
2.5.1 Governing Equations in Fluid Dynamics
2.5.2 Boundary Conditions in CVD Processes
2.5.3 CVD Simulation Study on TiO2 Synthesis
3 MATERIALS AND METHODS
3.1 Custom-Built MOCVD Reactor
3.2 Synthesis, Characterization, and Photocatalytic
Activity of Undoped and Fe-doped TiO2
Nanoparticles
3.2.1 Synthesis of Undoped and Fe-doped TiO2
Nanoparticles
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3.2.2 Characterization of Undoped and Fe-doped
TiO2 Nanoparticles
3.2.3 Photocatalytic Activity of Undoped and Fe-
doped TiO2 Nanoparticles
3.3 Dispersion and Coatings of TiO2 Nanoparticles
3.3.1 Starting TiO2 Nanoparticles
3.3.2 Aqueous Suspensions and Coatings
Preparation
3.3.3 Characterization of Aqueous Suspensions and
Coatings
3.3.4 Photocatalytic Activity of Coatings
3.4 Computational Fluid Dynamics Simulations
3.4.1 Reactor Configuration and Parameters
3.4.2 Reactions
3.4.3 Simulation Procedure
3.4.4 Methodology
4 RESULTS AND DISCUSSION
4.1 Synthesis, Characterization, and Photocatalytic
Activity of Undoped and Fe-doped TiO2
Nanoparticles
4.1.1 Undoped TiO2 Nanoparticles without the
Presence of O2 feed
4.1.2 Undoped TiO2 Nanoparticles with the
Presence of O2 feed
4.1.3 Fe-doped TiO2 Nanoparticles
4.2 Dispersion and Coatings of TiO2 Nanoparticles
4.2.1 Dispersion of TiO2 Nanoparticles
4.2.2 Coatings of TiO2 Nanoparticles
4.3 Computational Fluid Dynamics Simulations
4.3.1 Temperature Profiles
4.3.2 Velocity Profiles
4.3.3 Mass Fraction and Gas Streamline Profiles
4.3.4 Kinetic Rate of Reaction and Surface
Deposition Profiles
4.3.5 Effect of Deposition Temperature
4.3.6 Effect of Carrier Gas Flowrate
5 CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions
5.1.1 Synthesis, Characterization, and
Photocatalytic Activity of Undoped and Fe-
doped TiO2 Nanoparticles
5.1.2 Dispersion and Coatings of TiO2
Nanoparticles
5.1.3 Computational Fluid Dynamics Simulations
5.2 Recommendations
REFERENCES
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APPENDICES
A Equations Used by ANSYS Fluent 12.0 to Calculate the
Results for Volumetric and Wall Surface Reactions
B1 Isoelectric Point of TiO2 Nanoparticles
B2 Transmission Spectra of TiO2 Coatings for Various Amount
of Loading
B3 Effect of Activation Energy
B4 Temperature Profiles with Varying HTC Value (W/m2K)
B5 Adsorption and Photocatalytic Activity of TiO2 Nanoparticle
Samples Deposited at Different Deposition Temperatures
with and without Heat Treatment
B6 Quantitative Evaluation of the Bandgap Energy of Undoped
and Fe-doped TiO2 Samples Including the Commercial
Degussa P25
B7 Adsorption and Degradation of Formaldehyde Gas of TiO2
Coatings Produced from the Suspensions Prepared without
Dispersant and with Optimum Dispersant Addition
C Flow of Results and Discussion Chapter
BIODATA OF STUDENT
LIST OF PUBLICATIONS
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