Effect Of Substrate On The Microstructure And Morphology Of Ag-TiO2 Sol Gel Coating.

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UNIVERSITI TEKNIKAL MALAYSIA MELAKA

EFFECT OF SUBSTRATE ON THE MICROSTRUCTURE AND

MORPHOLOGY OF Ag-TiO

SOL GEL COATING

This report submitted in accordance with requirement of the Universiti Teknikal Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering

(Engineering Materials) (Hons.)

SIM VOON YEE B051110161 911111-14-6510

FACULTY OF MANUFACTURING ENGINEERING 2015

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UNIVERSITI TEKNIKAL MALAYSIA MELAKA

BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA

TAJUK: Effect of Substrate on the Microstructure and Morphology of Ag-TiO2 Sol Gel Coating

SESI PENGAJIAN: 2014/15 Semester 2

Saya SIM VOON YEE

mengaku membenarkan Laporan PSM ini disimpan di Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut: 1. Laporan PSM adalah hak milik Universiti Teknikal Malaysia Melaka dan penulis. 2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan

untuk tujuan pengajian sahaja dengan izin penulis.

3. Perpustakaan dibenarkan membuat salinan laporan PSM ini sebagai bahan pertukaran antara institusi pengajian tinggi.

4. **Sila tandakan ( )

SULIT

TERHAD

TIDAK TERHAD

(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia sebagaimana yang termaktub dalam AKTA RAHSIA RASMI 1972)

(Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)

Alamat Tetap:

169, Jalan Jambu Berasa, Jinjang Selatan,

52000, Kuala Lumpur.

Tarikh: ________________________

Disahkan oleh:

Cop Rasmi:

Tarikh: _______________________

** Jika Laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh laporan PSM ini perlu dikelaskan sebagai

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DECLARATION

I hereby, declared this report entitled “Effect of Substrate on the Microstructure and Morphology of Ag-TiO2 Sol Gel Coating” is the results of my own study except as cited

in references.

Signature : ………

Author’s Name : Sim Voon Yee

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APPROVAL

This report is submitted to the Faculty of Manufacturing Engineering of UTeM as a partial fulfillment to the requirements for the degree of Bachelor of Manufacturing Engineering (Engineering Materials) (Hons.). The member of the supervisory committee is as follow:

……….. (Prof Madya Dr. Zulkifli Bin Mohd Rosli)

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ABSTRAK

Salutan perak titanium dioksida (Ag-TiO2) telah didepositkan ke atas tiga jenis substrat

yang mempunyai kehabluran berbeza iaitu kaca amorfus, wafer silikon kristal tunggal dan polikristal indium tin oksida (ITO) kaca dengan kaedah sol gel. Cecair titanium dioksida (TiO2) disintesis pada suha bilik melalui proses pencampuran titanium

tetraisopropoxide (TTiP) ke dalam etanol, asid hidroklorik (HCL) dan air suling. Sebanyak lima lapisan TiO2 telah didepositkan atas setiap substrat melalui process

celupan. Kemudian, substrat yang bersalut degan TiO2 dicelup ke dalam cecair

nanopartikel perak untuk memperkenalkan kesan antimikrobial. Suhu pensinteran pula ditetapkan pada 500°C untuk mendapat Kristal yang saiz kecil dan lebih fasa anatase. Pemerhatian fizikal dan morfologi salutan telah dijalankan dengan mikroskop imbasan electron (SEM). Penyelidikan SEM menunjukkan bahawa salutan TiO2 yang deposit atas

kaca amorfus dan kaca ITO tidak homogen manakala wafer silikon boleh membentuk lapisan yang telus dan padat. Sebaliknya, salutan Ag-TiO2 tidak telus kepada ketiga-tiga

substrat kerana nanopartikel perak telah teroksida. Lapian Ag-TiO2 adalah tidak seragam.

Nanopartikel perak tidak tertanam ke dalam lapisan TiO2 tetapi membentuk satu lapisan

di atasnya. Nanopartikel perak yang halus dan tidak teratur didapati atas kaca amorfus manakala kepingan perak diagragatkan di permukaan lapis kaca ITO dan wafer silikon. Kaedah pencirian tambahan perlu menjalankan dalam kajian masa depan untuk menjelaskan korelasi antara penghabluran substrat dan transformasi kristal salutan Ag-TiO2.

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ABSTRACT

Silver titanium dioxide (Ag-TiO2) coatings obtained by a sol gel method were deposited

on three substrates with different crystallinity : amorphous glass, single crystal silicon wafer (100) and polycrystal indium tin oxide (ITO) glass. First, titanium dioxide (TiO2)

sol was synthesized in room temperature and acidic condition by hydrolysis of titanium tetraisopropoxide (TTiP) in ethanol, hydrochloric acid (HCL) and deionized (DI) water. Five layers of TiO2 coatings were deposited on all substrates using TiO2 sol by a dip

coating process. Then, TiO2 coated substrate was dipped into pure silver nanoparticles

solution to introduce antimicrobial effect. Sintering temperature was set at 500°C to produce small crystal size and more anatase phases. Physical observation and morphology of coating using scanning electron microscopy (SEM) had been conducted. SEM investigation revealed that the TiO2 coating deposited on amorphous glass and ITO

glass substrates was not homogenous whilst silicon wafer substrate can formed a transparent and dense coating. On the other hand, Ag-TiO2 coating on three substrates

was not transparent due to the presence of oxidized silver nanoparticles. The coatings were non homogenous. Silver nanoparticles did not embed into TiO2 coating and forming a layer on top of it. Fine and irregular shape of silver particles had found on the coating of glass substrate while silver flakes aggregated on coating surface of ITO glass and silicon wafer substrates. Additional characterization method should be conducted in future study to clarify the correlation between crystallinity of substrate and crystallite transformation of Ag-TiO2 coating.

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DEDICATION

I would like to dedicate this research to my beloved family, my supervisor and friend that has been supporting during the study of this research.

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ACKNOWLEDGEMENT

I would like express my deepest gratitude to my supervisor, Prof Madya Dr. Zulkifli Bin Mohd Rosli for his excellent guidance and friendly advice during the research of this project. Without his patient guidance, I would not able to complete this research report.

Besides that, I would like to thank my research team members. They were always supporting me and sharing information with me to accomplish this project. And also thanks for everybody who has helped me out during my report preparation.

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TABLE OF CONTENT

Abstrak i

Abstract ii

Dedication iii

Acknowledgement iv

Table of Content v

List of Tables viii

List of Figures ix

List of Abbreviation, Symbols and Nomenclatures xi

CHAPTER 1: INTRODUCTION 1

1.1 Background study 1

1.2 Problem Statement 2

1.3 Objectives 3

1.4 Scope 3

CHAPTER 2: LITERATURE REVIEW 5

2.1 Surface and coating technology 5

2.1.1 Self cleaning properties of titanium dioxide (TiO2) coating 5

2.1.2 Antimicrobial silver titanium dioxide (AgTiO2) coating 6

2.1.3 Factors influence the coating performance 7

2.2 Substrate properties and applications 10

2.2.1 Selection of substrate 10

2.2.2 Glass 12

2.2.3 Silicon wafer 12

2.2.4 Indium tin oxide (ITO) glass 13

2.2.5 Impact of substrate on TiO2-PEG coating 14

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2.3.1 Chemical vapor deposition (CVD) 16

2.3.2 Physical vapor deposition (PVD) 16

2.3.3 Sol-gel method 17

2.3.4 Selection of coating deposition technique 17

2.4 Methods for preparing Ag-TiO2 sol gel coating 18

2.4.1 Sol gel coating 18

2.4.2 Selection of sol gel coating deposition technique 20

2.4.3 Parameter for dip coating process 21

2.4.4 Coating with silver nanoparticles solution 22

2.5 Characterization Method 23

CHAPTER 3: METHODOLOGY 26

3.1 Experiment flow chart 27

3.2 Substrates preparation 27

3.3 TiO2 sol preparation procedure 29

3.4 AgTiO2 coating forming by sol-gel dip coating technique 31

3.5 Coating characterization technique 34

CHAPTER 4: RESULT AND DISCUSSION 35

4.1 TiO2 sol gel observation 35

4.2 Physical Observation 36

4.2.1 Physical Observation on TiO2 coating 36

4.2.2 Physical Observation on Ag-TiO2 coating 39

4.3 SEM surface morphology of coating 41

4.4 Adhesion and thickness of coating 48

CHAPTER 5: CONCLUSION AND RECOMMENDATION 51

5.1 Conclusion 51

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REFERENCES 54

APPENDICES

Appendix A: Gantt chart PSM 1

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LIST OF TABLES

2.1 Comparison table of coating deposition method 7

2.2 Comparison of microstructure and morphology of TiO2 coating. 10

2.3 Differences of properties between ITO and FTO coating 14 2.4 Advantages and disadvantages of CVD, PVD and sol gel method 17 2.5 Advantages and disadvantages of spin coating and dip coating 21

2.6 Comparison table of characterization method 23

3.1 Volume of chemical require to prepare AgTiO2 sol-gel 30

4.1 Physical observation of Ag-TiO2 coated substrates (Glass, Silicon 40

Wafer, ITO glass)

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LIST OF FIGURES

2.1 XRD results for coating derived from different solutions 9 (Alzamani et al., 2013)

2.2 SEM micrograph of TiO2-PEG films deposited on (a) glass, (b) FTO 15

and (c) Si. (Anastasescu et al., 2014)

2.3 SEM micrographs of anatase TiO2 particles (a) without acid catalyst 19

and (b) with acid catalyst (Sayilkan, et al., 2005).

2.4 Effect of withdrawal speed on thickness of TiO2 coating. 22

(Barati et al., 2009)

2.5 SEM (A, B) and FESEM (C,D) images of Agnanowires. 25

(Bi, Y. and Lu, G., 2008)

3.1 Experiment flow chart 27

3.2 Flow chart of substrate preparation 28

3.3 Dimension of substrate 28

3.4 Flow chart of TiO2 sol preparation 29

3.5 Sol gel dip coater machine 31

3.6 Flow chart of dip coating process 32

3.7 The graph of sintering cycle at 500°C 33

3.8 Silver nanoparticle solution with concentration of 1000ppm 33

4.1 Final TiO2 solution (a) after 3 hour stirring (b) after 1 days 36

4.2 Physical observation of the TiO2 coated substrates (a) Glass 36

(b) Silicon Wafer (c) ITO glass

4.3 Glass substrate after coated with TiO2 sol gel at (left) day 1 (right) day 5 37

4.4 ITO glass substrate after coated with TiO2 sol gel at (left) day 1 38

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4.5 Silicon wafer substrate after coated with TiO2 sol gel at (left) day 1 38

(right) day 5

4.6 Physical observation of Ag-TiO2 coated substrates (a) Glass (b) Silicon 39

Wafer (c) ITO glass

4.7 SEM surface morphology of bare (a) glass, (b) ITO glass and 41 (c) silicon wafer substrates

4.8 SEM surface morphology of TiO2 coating on glass substrate 42

4.9 Contrast between surface of silicon wafer substrate with and without 43 coating

4.10 SEM surface morphologies of Ag-TiO2 coating on different substrates 44

at 150, 1000, 300 and 5000 magnification

4.11 SEM image of Ag-TiO2 coating on glass substrate. 45

4.12 SEM image of Ag-TiO2 coating on ITO glass substrate. 46

4.13 SEM image of Ag-TiO2 coating on silicon wafer substrate. 46

4.14 SEM surface morphologies of bare substrate, 5 layers TiO2 coating and 47

Ag-TiO2 coating

4.15 Cross section of TiO2 coating on glass substrate under SEM 48

4.16 Cross section of TiO2 coating on silicon wafer substrate under SEM 49

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LIST OF ABBREVIATIONS, SYMBOLS AND

NOMENCLATURE

AFM - Atomic Force Microscopy

Ag - Silver

AgNO3 - Silver Nitrate

Ag-TiO2 - Silver Doped Titanium Dioxide

Al2O3 - Aluminium Oxide

CaO - Lime

CVD - Chemical Vapor Deposition

DI - Deionized Water

EDX/EDS - Energy-dispersive X-ray spectroscopy

F - Fluorine

FESEM - Field Emission Scanning Electron Microsopy

FTO - Fluoride doped Tin Oxide

H2O2 - Hydrogen Peroxide

H2SO4 - Sulfuric Acid

HCL - Hydrochloric Acid

HNO3 - Nitric Acid

In2O3 - Indium (III) Oxide

ITO - Indium Tin Oxide

Na2O - Sodium Oxide

PEG - Polyethylene Glycol

PET - Polyethylene Terephthalate

Pt - Platinum

PVD - Physical Vapor Deposition

SEM - Scanning Electron Microscopy

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SiO2 - Silicon Dioxide

SnO2 - Tin Dioxide

TEM - Transmission Electron Microscopy

Ti - Titanium

TiO2 - Titanium Dioxide

TTiP/TIP - Titanium (IV) Isopropoxide

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CHAPTER 1 INTRODUCTION

This chapter explains the background study of this research and problem statement had been justified. Objectives and scope also included in this chapter.

1.1 Background study

Importance of maintaining personal hygiene is taught from an early age. Hygiene in daily life settings is needed to prevent spread of infection diseases when human come in contact with other substrates. Thus, people had introduced a coating on substrate surface to provide self cleaning effect. Titanium dioxide (TiO2) had become the best

choice for self-cleaning material due to its high photocatalytic properties, inexpensive and easy to deposit as a coating. This coating can choose to deposit on variety type of substrates such as ceramic, fiber glass, stainless steel and silica according to the substrate properties and its application.

However, self cleaning effect is not enough for maintain cleanliness particularly in medical industry. Since TiO2 has high photocatalytic activity, some researcher doped

TiO2 coating with silver (Ag) nanoparticles to prepare a photocatalytic antimicrobial

coating. Antimicrobial coating is a surface coated by antimicrobial agent that able to diminish the ability of microorganisms to grow. Ag has good antibacterial properties. Low concentration of Ag nanoparticles is harmless to human body but able to kill microorganisms such as bacterial. (Kumar et al., 2013)

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According to Yu et al.(2011), Ag-TiO2 coating had successfully deposited on

silicon wafer using sol gel method and exhibiting a strong antimicrobial behavior. This Ag-TiO2 solution can be coated on the medical device using different coating techniques.

Other than medical device, Ag-TiO2 solution also can be coated on other substrates

surface such as windshield and wall tiles to obtain the antimicrobial and self cleaning effect.

There is numerous coating techniques have been used to coat the Ag-TiO2 sol gel

on the substrates surface for example sputtering, electron beam evaporation as well as sol gel process. According to Alzamani et al. (2013), sol gel dip coating is preferred due to its advantages like low operation temperature, low equipment cost and able to control microstructure of coating in order to achieve high homogeneity.

1.2 Problem statement

Generally, properties of coating deposited using sol gel technique are strongly influence by the type of precursor, solvent, catalyst and additive. Changing in the molar ratio of materials or heat treatment temperature definitely bring different results. From the literature studies, substrate type used will also affect the coating properties as well as the adhesive between substrate and coating.

Study found that the surface roughness of substrate affects the surface roughness of coating. For example, glass, FTO and silicon substrates had different surface roughness. Smooth surface of glass and silicon substrate produce thinner coating surface where the rough surface such as FTO substrate produces thicker coating surface (Anastasescu, 2014). Coating deposited on FTO also consists of larger pore size compare with glass. Hence, by comparing the bare surface roughness and coating surface roughness, the relation between substrate and coating can be justifying.

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Some of the researches state that the crystallinity of substrate affects the final microstructure and surface morphology of the coating. Phase composition of coating depends on the crystallinity substrate. Crystalline substrate consists of higher phase transformation rate. With the same heat treatment temperature, TiO2 coating on the

silicon single crystal consists of both anatase and rutile phases where TiO2 coating on

amorphous glass does not undergo any phase transformation.

However, those studies were not conducted systematically on the how the substrates bring effects on the Ag-TiO2 coating properties. Therefore, the aim of this

study is to provide a systematic study on the effect of different substrates (soda lime glass slide, indium tin oxide (ITO) glass and silicon wafer) with different crystallinity and surface roughness towards the morphology of the Ag-TiO2 coating via sol gel

technique.

1.3 Objectives

1. To deposit Ag-TiO2 coating on various substrates with different crystallinity via

sol gel process.

2. To analyses the effect of substrates’ crystallinity on the morphology of Ag-TiO2

coatings

1.4 Scope

The scope of this research will focus on the effect of three types of substrates on the microstructure and morphology of the Ag-TiO2 .The three substrates are soda lime

glass, Indium Tin Oxide (ITO) glass and silicon wafer. The significant of this research is to ensure the effect of crystallinity of substrate toward morphology of Ag-TiO2 coating

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future. Coating method chosen in this research is sol gel technique with constant chemical composition and deposit parameter. Different characterization methods will use to analyze the properties of Ag-TiO2 coating.

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CHAPTER 2 LITERATURE REVIEW

This chapter explains about the surface and coating technology, application of TiO2 and the advantage after doped with silver nanoparticles. Factors that affect the

coating properties will discuss in this section based on the result of previous researches’ report. The function and properties of substrate as well as the coating deposition technique also compare to make the selection.

2.1 Surface and coating technology

Coating can be defines as a thin layer or covering of something. When the coating thickness is less than few micrometers, it can be describe as thin film. Coating can be use for various applications. For example, colour coating was used to enhance the appearance of object where functional coating use to manipulate the surface properties such as improve the corrosion resistance or wear resistance. Currently, the technology of coating still undergoes intense development to achieve the better coating properties in different application.

2.1.1 Self cleaning properties of titanium dioxide (TiO2) coating

One of the popular engineering materials in our daily life is titanium dioxide (TiO2). Titanium dioxide (TiO2) as known as titania is a high chemical stability,

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non-toxicity and low cost material. TiO2 exists in three main crystal structure namely

brookite, anatase and rutile. When TiO2 coating undergoes heat treatment process, it will

transform from amorphous phase into crystalline anatase. Further heating will produce pure rutile phases. However, anatase phase is the most photoactivity among the rest.

A thin layer of TiO2 coating can deposited on the glass surface to introduce self

cleaning properties. The first self-cleaning window announced by the Pikington Glass. Photocatalytic behavior of TiO2 allow dirt chemically break down when the TiO2 coating

exposed to light. Then the dirt is washes away by rain during a hydrophilic process which the dirt molecule is tend to attracted and dissolved by rain. Thus, it brings a significant effect on the self-cleaning properties. At the present, TiO2 coating is broadly

use in medical, food, and paint and coatings industry.

According to Alzamani et al. (2013), a transparent TiO2 coating that prepared by

sol gel method can deposited on glass substrate using dip coating technique. High photocatalytic activity and superhydrophilic behavior cause TiO2 coating become

competent in self cleaning application.

2.1.2 Antimicrobial silver doped titanium dioxide (Ag-TiO2) coating

Since TiO2 has high photocatalytic activity, some researchers combine TiO2 with

silver nanoparticles to prepare a photocatalytic antimicrobial coating. According to Yu et al. (2011), Ag-TiO2 coating had successfully deposited on silicon wafer using sol gel

method and exhibiting a strong antimicrobial behavior. Silver (Ag) nanoparticlel is well known antimicrobial agents that have strong antibacterial effect. Ag ions can cause the inactivation of bacteria and virus. Ag mixed with titanium dioxide (TiO2)in a solvent

and then the mixed solution use to forms a coating on substrate surface for self-cleaning and antimicrobial purpose. High reactivity and low raw material cost makes silver doped titanium dioxide (Ag-TiO2) become the most preferred antimicrobial coating used.

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Antibacterial coating plays an important role in hygiene protection and prevention of bacterial diseases. The application of antimicrobial coating is infinite as it can apply at any surface that requires hygienic protection, for example healthcare industry, food industry, and household product. Antimicrobial flooring system is the antimicrobial coating applies on the floor. It successfully offer protection against bacteria, virus as well as fungi comes into contact with the floor.

2.1.3 Coating deposition method and factors influence the coating performance

There are many techniques can be use to deposit coating on the substrate surface. Based on the Table 2.1, sol gel dip coating technique is the most preferred technique use in preparing TiO2 or Ag-TiO2 coating. Preparation condition has effect on the

performance of coating that prepares using sol gel process. Those factors was summarise as precursor, solvent, additive, catalyst, annealing temperature and substrate.

Table 2.1: Comparison table of coating deposition method

References Coating Deposit method Variable Substrate

Guo et al. (2013) TiO2 Laser chemical vapor _deposition Deposition _parameter Pt/Ti/SiO_substrate2/Si Giolli et al. (2007) TiO2 Physical vapour

deposition system Substrate Copper , stainless steel, glass Bazmara and

Mohammadnejad (2014)

TiO2 Sol gel spin coating Additives and

precursor Glass Kaewwiset et al.

(2008) TiO2 Sol gel dip coating Annealed temperature glass

Nikolic et al. (2005)

TiO2 Sol gel dip coating Annealed

temperature, substrate Quartz glass, quarts single crystal, silicon single crystal, polycrystalline alumina Alzamani et al. (2013) TiO2 Sol gel dip coating Catalyst Glass

Wang et al. (2013) TiO2 Sol gel dip/spin _coating Coating technique α-Al2O3 substrate

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Golobostanfard and

Abdizadeh (2012) TiO2 Sol gel spin coating Solvent glass Anastasescu et al

(2014) TiO2 Sol gel dip coating Substrate Glass, FTO, Silicon Wafer Baglio et al.(2011) TiO2 Spray coating Coating Thickness FTO

Adochite et al. (2011) Ag-TiO2 Magnetron sputtering Present of silver, Annealed temperature

Silicon and quartz substrate

Wodka et al. (2010) Ag-TiO2 Photoreduction _treatment Concentration of _silver - Amin et al. (2009) Ag-TiO2 Sol gel Calcined

temperature - Kadziola et al. (2014) Ag-TiO2 Sol gel dip coating , reactive magnetron

sputtering

Coating method Silicon wafer

Kumar et al. (2013) Ag-TiO2 Sol gel, electron beam physical vapour deposition

Coating method glass

Peerakiatkhajohn et

al. (2011) Ag-TiO2 Sol gel dip coating Concentration of silver PET Yu et al.(2011) Ag-TiO2 Sol gel spin coating Concentration of

silver Silicon wafer Piwonski et al. (2011) Ag-TiO2 Sol gel dip coating Deposition parameter Silicon Wafer

He et al. (2002) Ag-TiO2 Sol gel Dip coating Present of silver glass

Zhao, B. and Chen, Y.

(2011) Ag-TiO2 Sol gel dip coating Present of silver Glass Ubonchonlakate et al.

(2012) Ag-TiO2 Sol gel dip coating Present of silver, additive glass

Prasad et al. (2011) Ag-TiO2 Sol gel spin coating Present of silver Glass, quartz, _{silicon substrate}

Alzamani et al. (2013) claimed that coating using sol containing acidic catalyst can form no defects, transparent and smooth surface. Besides that, to obtain a self-cleaning surface with high photocatalytic activity, the particles size has to be as small as possible and high anatase phase percent. He found that when the coated substrate undergo heat treatment temperature at 500°C produce smaller particle size and more anatase phases compared to 700°C as shown in figure 2.1. This is because in a sol gel process of transition metal alkoxides, hydrolysis and condensation happen rapidly in high temperature lead to larger crystalline size and non uniform particle form.

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silicon single crystal consists of both anatase and rutile phases where TiO2 coating on

amorphous glass does not undergo any phase transformation.

However, those studies were not conducted systematically on the how the substrates bring effects on the Ag-TiO2 coating properties. Therefore, the aim of this

technique.

1.3 Objectives

1. To deposit Ag-TiO2 coating on various substrates with different crystallinity via

sol gel process.

2. To analyses the effect of substrates’ crystallinity on the morphology of Ag-TiO2

coatings

1.4 Scope

The scope of this research will focus on the effect of three types of substrates on the microstructure and morphology of the Ag-TiO2 .The three substrates are soda lime

glass, Indium Tin Oxide (ITO) glass and silicon wafer. The significant of this research is to ensure the effect of crystallinity of substrate toward morphology of Ag-TiO2 coating

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CHAPTER 2

LITERATURE REVIEW

This chapter explains about the surface and coating technology, application of TiO2 and the advantage after doped with silver nanoparticles. Factors that affect the

2.1 Surface and coating technology

2.1.1 Self cleaning properties of titanium dioxide (TiO2) coating

One of the popular engineering materials in our daily life is titanium dioxide (TiO2). Titanium dioxide (TiO2) as known as titania is a high chemical stability,

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non-toxicity and low cost material. TiO2 exists in three main crystal structure namely

brookite, anatase and rutile. When TiO2 coating undergoes heat treatment process, it will

transform from amorphous phase into crystalline anatase. Further heating will produce pure rutile phases. However, anatase phase is the most photoactivity among the rest.

A thin layer of TiO2 coating can deposited on the glass surface to introduce self

cleaning properties. The first self-cleaning window announced by the Pikington Glass. Photocatalytic behavior of TiO2 allow dirt chemically break down when the TiO2 coating

use in medical, food, and paint and coatings industry.

According to Alzamani et al. (2013), a transparent TiO2 coating that prepared by

sol gel method can deposited on glass substrate using dip coating technique. High photocatalytic activity and superhydrophilic behavior cause TiO2 coating become

competent in self cleaning application.

2.1.2 Antimicrobial silver doped titanium dioxide (Ag-TiO2) coating

Since TiO2 has high photocatalytic activity, some researchers combine TiO2 with

silver nanoparticles to prepare a photocatalytic antimicrobial coating. According to Yu et al. (2011), Ag-TiO2 coating had successfully deposited on silicon wafer using sol gel

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2.1.3 Coating deposition method and factors influence the coating performance

performance of coating that prepares using sol gel process. Those factors was summarise as precursor, solvent, additive, catalyst, annealing temperature and substrate.

Table 2.1: Comparison table of coating deposition method

References Coating Deposit method Variable Substrate

Guo et al. (2013) TiO2 Laser chemical vapor _deposition Deposition _parameter Pt/Ti/SiO2/Si _substrate Giolli et al. (2007) TiO2 Physical vapour _{deposition system} Substrate Copper , stainless _{steel, glass}

Bazmara and Mohammadnejad

(2014)

TiO2 Sol gel spin coating Additives and

precursor Glass

Kaewwiset et al.

(2008) TiO2 Sol gel dip coating Annealed temperature glass

Nikolic et al. (2005)

TiO2 Sol gel dip coating Annealed

temperature, substrate Quartz glass, quarts single crystal, silicon single crystal, polycrystalline alumina

Alzamani et al. (2013) TiO2 Sol gel dip coating Catalyst Glass

Wang et al. (2013) TiO2 Sol gel dip/spin _coating Coating technique α-Al2O3 substrate

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Golobostanfard and

Abdizadeh (2012) TiO2 Sol gel spin coating Solvent glass

Anastasescu et al

(2014) TiO2 Sol gel dip coating Substrate Glass, FTO, Silicon Wafer

Baglio et al.(2011) TiO2 Spray coating Coating Thickness FTO

Adochite et al. (2011) Ag-TiO2 Magnetron sputtering Present of silver, Annealed temperature

Silicon and quartz substrate

Wodka et al. (2010) Ag-TiO2 Photoreduction _treatment Concentration of _silver -

Amin et al. (2009) Ag-TiO2 Sol gel Calcined _temperature -

Kadziola et al. (2014) Ag-TiO2 Sol gel dip coating , reactive magnetron sputtering

Coating method Silicon wafer

Kumar et al. (2013) Ag-TiO2 Sol gel, electron beam physical vapour deposition

Coating method glass

Peerakiatkhajohn et

al. (2011) Ag-TiO2 Sol gel dip coating Concentration of silver PET Yu et al.(2011) Ag-TiO2 Sol gel spin coating Concentration of

silver Silicon wafer

Piwonski et al. (2011) Ag-TiO2 Sol gel dip coating Deposition parameter Silicon Wafer He et al. (2002) Ag-TiO2 Sol gel Dip coating Present of silver glass

Zhao, B. and Chen, Y.

(2011) Ag-TiO2 Sol gel dip coating Present of silver Glass

Ubonchonlakate et al.

(2012) Ag-TiO2 Sol gel dip coating Present of silver, additive glass

Prasad et al. (2011) Ag-TiO2 Sol gel spin coating Present of silver Glass, quartz, _{silicon substrate}

Effect Of Substrate On The Microstructure And Morphology Of Ag-TiO2 Sol Gel Coating.

UNIVERSITI TEKNIKAL MALAYSIA MELAKA