UNIVERSITI PUTRA MALAYSIA CHARACTERIZATION AND …psasir.upm.edu.my/id/eprint/41807/1/FK 2011 147R.pdf · Akhir sekali, keputusan simulasi CFD menunjukkan bahawa kadar permukaan pengenapan

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

© CO

PYRI

GHT U

PM

CHARACTERIZATION AND DISPERSION

BEHAVIOR OF TITANIUM DIOXIDE AS

PHOTOCATALYTIC NANOPARTICLES USING

METAL ORGANIC CHEMICAL VAPOUR

DEPOSITION SYSTEM


DOCTOR OF PHILOSOPHY

UNIVERSITI PUTRA MALAYSIA

2011

© CO

PYRI

GHT U

PM

CHARACTERIZATION AND DISPERSION BEHAVIOR OF TITANIUM

DIOXIDE AS PHOTOCATALYTIC NANOPARTICLES USING METAL


By


Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia,

in Fulfilment of the Requirements for the Degree of Doctor Philosophy

December 2011

© CO

PYRI

GHT U

PM

To my beloved parents for their great sacrifice..

To my dear husband and son for completing my

life..

© CO

PYRI

GHT U

PM

ii

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


By


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

© CO

PYRI

GHT U

PM

iii

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.

© CO

PYRI

GHT U

PM

iv

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


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

© CO

PYRI

GHT U

PM

v

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.

© CO

PYRI

GHT U

PM

vi

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.

© CO

PYRI

GHT U

PM

vii

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.

© CO

PYRI

GHT U

PM

viii

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


(Internal Examiner)

Dayang Radiah binti Awang Biak, PhD

Senior Lecturer



(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


Date:

© CO

PYRI

GHT U

PM

ix

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



(Chairman)

Norhafizah Abdullah, PhD

Associate Professor



(Member)

Tinia Idaty Mohd Ghazi, PhD

Senior Lecturer



(Member)

________________________________

BUJANG BIN KIM HUAT, PhD

Professor and Dean

School of Graduate Studies


Date:

© CO

PYRI

GHT U

PM

x

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.

___________________________


Date: 2 December 2011

© CO

PYRI

GHT U

PM

xi

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

Page

23

33

59

90

91

103

128

148

© CO

PYRI

GHT U

PM

xii

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)

Page

15

19

24

29

31

37

41

45

46

52

55

57

© CO

PYRI

GHT U

PM

xiii

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


Samples Deposited at (a) 700°C, (b) 700°C Heat Treated at

400°C, and (c) 700°C Heat Treated at 700°C


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

58

60

61

62

74

75

81

88

89

100

101

106

108

110

© CO

PYRI

GHT U

PM

xiv

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



Samples Deposited at (a) 400°C, (b) 500°C, (c) 600°C, (d)

700°C, (e) 800°C, and (f) 900°C


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



Samples Deposited at 700°C with Carrier Gas Flowrate of (a)

200 mL/min, (b) 400 mL/min, and (c) 600 mL/min


700°C with Different Carrier Gas Flowrates - (a) 200

mL/min, (b) 400 mL/min, and (c) 600 mL/min


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

114

120

121

124

130

133

136

138

140

© CO

PYRI

GHT U

PM

xv

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


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



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

142

143

145

149

151

153

155

159

162

169

171

© CO

PYRI

GHT U

PM

xvi

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

173

174

176

177

179

180

181

183

185

187

189

© CO

PYRI

GHT U

PM

xvii

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

191

194

197

199

202

204

208

210

© CO

PYRI

GHT U

PM

xviii

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

© CO

PYRI

GHT U

PM

xix

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

© CO

PYRI

GHT U

PM

xx

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

© CO

PYRI

GHT U

PM

xxii

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

Page

ii

iv

vi

viii

x

xi

xii

xviii

xx

1

1

5

6

8

9

11

11

13

16

22

24

26

29

31

36

40

48

51

55

62

64

67

69

73

75

76

76

© CO

PYRI

GHT U

PM

xxiii

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

78

81

83

83

83

85

86

89

89

90

92

95

97

97

98

119

146

168

168

180

182

182

186

190

195

198

207

211

211

211

215

216

217

220

© CO

PYRI

GHT U

PM

xxiv

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

234

235

239

240

241

244

245

248

249

250

251

252

1-Cover Page2-Title Page3-Dedication4-Abstract5-Abstrak6-Acknowledgements7-Approval8-Declaration9-List of Tables10-List of Figures11-List of Symbols and List of Abbreviations12-Table of Contents13-CHAPTER 1-Introduction14-CHAPTER 2-Literature Review15-CHAPTER 3-Materials and Methods16-CHAPTER 4-Results and Discussion17-CHAPTER 5-Conclusions and Recommendations18-References19-Appendices20-Biodata of Student21-List of Publications

Documents

UNIVERSITI PUTRA MALAYSIA CHARACTERIZATION AND …psasir.upm.edu.my/id/eprint/41807/1/FK 2011 147R.pdf · Akhir sekali, keputusan simulasi CFD menunjukkan bahawa kadar permukaan pengenapan