laporan kemajuan morphological analyses of tio …

LAPORAN KEMAJUAN

MORPHOLOGICAL ANALYSES OF TiOTITANIUM ALLOY PLATE

Tahun 1 dari rencana 2 tahun

PROF. DR. IR.

IR. NGAKAN PUTU GEDE SUARDANA, MT., Ph.D

I MADE GATOT KAROHIKA, ST.,MT.

UDAYANA UNIVERSITY

LAPORAN KEMAJUAN

MORPHOLOGICAL ANALYSES OF TiO2 ANODIZED ON TITANIUM ALLOY PLATE

Tahun 1 dari rencana 2 tahun

PROF. DR. IR. I NYOMAN GDE ANTARA, M. ENG.NIDN: 0008076412

NGAKAN PUTU GEDE SUARDANA, MT., Ph.DNIDN: 0017096401

I MADE GATOT KAROHIKA, ST.,MT.NIDN: 0031127020

UDAYANA UNIVERSITYMARCH, 2013

ANODIZED ON

ENG.

NGAKAN PUTU GEDE SUARDANA, MT., Ph.D

• •

Kesehatan dan obat-obatan(Biomaterial)445/Teknik materialobatan(Biomaterial)445/Teknik material

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• •

CONTENTS

COVER …………………………………………………………………………………… 1VALIDATION SHEET ………………..…………………………………………………. 2CONTENTS ……………………………………………………………………………...… 3ABSTRACT …………………………………………………………..…………...…….… 4CHAPTER I INTRODUCTION ………………………………………...… 5CHAPTER II STUDY OF REFERENCES …………………………………………... 10CHAPTER III EXPERIMENTAL METHOD ……………………………………….… 14CHAPTER IV BUDGET AND SCHEDULE ………………………………………..... 23REFERENCES …………………………………………………………………………. 25APPENDIXES …………………………………………………………………………. 27

1. BUDGET JUSTIFICATION ……………………………………….… 272. RESEARCH EQUIPMENTS AND SUPPORTING FACILITIES… ……………. 303. ORGANIZATION AND JOB DISCRIPTION ……………………………….. 324. MEMORANDUM OF UNDERSTANDING AND LOA ……………………… 335. CURICULUM VITAE …………………………………………………………. 346. STATEMENT LETTER OF RESEARCHER …………………………………. 487. A COPY ON COVER AND EDITOR BOARD OF THE PLANNED INTERNATIONAL PUBLISHER …………………………………. 49

• •

ABSTRACT

The superior properties of Titanium and its alloys are proven to be potentially very excellent metallic alloys for load bearing bioimplant plications. Unfortunately, these alloys have some disadvantages. Like most metals, Titanium and its alloys exhibit poor osteoinductive properties because of their bioinert fe . They do not bond to bone at early stage of implantation and these materials undergo electrochemical exchange and release metallic ions in the physiological environment which is believed to the cause of implant failure. Therefore, surface modification of titanium and its alloys is essential preconditions for the success of Titanium alloy as biomaterial implants.

Among various conventional methods for surface modific ion such as physical and chemical vapor deposition, as well as sol–gel processes, anodic oxidation treatment is attracting interest of fabricating oxide coating on Ti um and its alloys. It is a novel modifying method that also called by micro-arc oxidation (MAO), plasma electrolytic oxidation (PEO), micro plasma oxidation (MPO) or anodic spark deposition (ASD).

This study will be aimed at evaluating morphological and crystalline structures of anodic and hydrothermal Titanium oxide TiO2 thin films formed on Ti6Al4V alloy in a mixture of glycerophosphate disodium salt (GP) and calcium acetate (CA) solution at various forming environments such as CA molarities (0.15, 0.30 and 0.45M), applied voltage (240~340 V) and processing time (5 and 10 min).

The Anodic oxide films TiO2 then will be hydrothermally treated using an autoclave (ILSHIN Autoclave, Korea) at temperature of 300 C and pressure of 9 MPa for 2 hours. Morphological surface will be observed using a scanning electron microscope (JSM-5900, JEOL, Japan) and the crystal structure will also be characterized using an X-ray diffractometer (Dmax III-A type, Rigaku Co., Japan) wi scanning rate 4 /min. While chemical composition will be analyzed using energy disp e spectroscopy (EDS) in conjunction with the scanning electron microscope.

Keywords: anodic titanium thin film, surface morphology, crystalline structure, micropores number and size, anodizing voltage, glycerophosphate disodium salt, calciu acetate molarity

• •

CHAPTER I

INTRODUCTION

a. Reinstatement of the role of the natural joint

Biomaterial is a nonviable material used in medical de intended to interact with

biological systems for the purpose of improving health. A more recent consensus definition of a

biomaterial excludes the words “nonviable” due to the d lopment of tissue-engineered

scaffolds and hybrid prosthetics in which living cell are combined with nonorganic material [1].

The characteristic of a biomaterial must be controlled under very tight conditions to ensure

its mechanical, chemical and bioactivity integrities to avoid any post implantation failures. As

shown in Figure 1.1, the failure of biomaterials made o a stainless steel 316L. The human body

is a hostile environment, any foreign object including mplant device will be attacked and

attempted to be isolated. An implanted biomaterial in he human body is also must be subjected

to a continuous flexural and torsion stresses associated with cardiac activity, body movement and

patient anatomy which directly affect its integrity. As a result, few biomaterials are accepted

clinically including ceramic, polymer and metal. Although a material exhibits an excellent

mechanical property, the device often is negated by its incompatibility with the tissue with which

it will be in contact. The compatibility is the first consideration of material scientists who always

consider for a new candidate biomaterial.

Therefore, to be used as an implant, a biomaterial must exhibit excellent properties. For an

artificial hip implant as an example, many researchers have identified some basic required

properties including;

The mobility of the joint and the capability of load transferring must be returned, as

closed as possible, to that of healthy. The prosthesis must be able to withstand the large and

variable stresses that occur in situ, ensuring that the stress distribution and load transfer through

the implant material, and cement mantle, are predictable and surgeon independent.

• •

a)

b)

Fig. 1.1. a) Photograph of the failed section of a stainless steel 316L on the femur orthopedic plateimplant b) A Supracondylarperiprosthetic fracture then it was internal fixated by retrograde locking nail,

G.K. Triantafyllidis et al. Aristotle University of Thessaloniki, Greece [2].D. Backstein et al.

Mount Sinai Hospital, University of Toronto, Canada [3].

• •

b. Biocompatibility

c. Sufficient mechanical properties

d. Ease of fabrication

e. Ease of implantation and explantation

f. Economic advantages

Biocompatibility has been defined as “the ability of a aterial to perform with an

appropriate host response in a specific application” [4,5]. In other words, it means that the

material or any leachable products from it, must not c cell death, chronic, inflammation, or

other impairment of cellular functions.

High fatigue strength and toughness are important for moral stems as the shafts are

stressed in cyclic bending and torsion. Hence fatigue s the most likely form of failure in these

components. The implant must be resistant to fatigue i aggressive environments, preventing

stress corrosion cracking as well as corrosion fatigue.

Although production costs should not be an issue in th maintenance of human life, high

production costs or difficult manufacture routes would price the implant components

unacceptably high, and thus suitable materials with correspondingly suitable manufacturing

routes are necessary.

A wide variety of intricate component shapes and sizes be readily implantable and

explantable. This last requirement is the subject of some debates as there are two schools of

thought on whether the prostheses should be cemented o cementless, with fashion or surgeon

preference often dictating the type f joint implanted.

Economic advantage and issue are the last property required in artificial hip implants.

On the titanium alloys, there are seven possible types oxide film formed. They include

amorphous oxide, cubic titanium oxide (TiO), hexagonal titanium sesquioxide (Ti2O3), tetragonal

titanium dioxide (anatase), orthorhombic TiO2 (brookite), tetragonal TiO2 (rutile) and non-

• •

stoichiometric oxides (TixOy).

TiO2 thin film is very important to be used in titanium and its alloys for biomaterial

implants because of its excellent mechanical and chemi al stability as well as good insulating

properties. It demonstrates promising in vivo corrosion behavior acting as chemical barrier in

ambient conditions against release of metal ions from t implant. The surface titanium oxide

determines the diffusion rate calcium and phosphate on the implant-tissue interface. Generally,

its corrosion resistance increases with increasing the ide coating. Thus, biocompatibility of

titanium and its alloys depends on their corrosion resistance. The TiO2 film also improves wear

resistant which is suitable for load-bearing application of the metal.

Among various conventional methods such as physical an chemical vapor deposition,

as well as sol–gel processes, anodic oxidation treatment is attracting interest of fabricating oxide

coating on titanium and its alloys. It is a novel modi ying method that also called by micro-arc

oxidation (MAO), plasma electrolytic oxidation (PEO), microplasma oxidation (MPO) or anodic

spark deposition (ASD).

In this method, when a positive voltage is applied to Ti specimen immersed in an

electrolyte, anodic oxidation of Ti occurs to form a TiO2 layer on the surface. When the applied

voltage is increased to a certain point, a micro-arc o urs because of the dielectric breakdown of

the TiO2 layer. At that moment, the Ti ions in the substrate an the OH ions in the electrolyte

move in opposite directions very fast to again form TiO2.

The anodic oxidation method has some advantages, such s its capability of fabricating

porous, changeable of crystalline structure and chemic composition of oxide films depending

on the fabrication environment [6,7]. The formed oxide lm has a relatively high interfacial

bonding strength because of momentary anodic spark gene ed during anodic oxidation

treatment. This method is also suitable for coating various substrates with complex geometries.

In addition, it is the simplest and cost effectively am ng the different methods [8,9].

The characteristic of the oxide coating mostly is affe ed by the fabrication parameters,

such as electrolyte solution, applied electrical potential and current density. A basic requirement

• •

for electrolyte is that is should not be aggressive towards the growing oxide and not generate any

dissolution during the process. The electrolyte must e the oxide growth rate is higher than

the dissolution one. The most commonly used electrolyte in titanium anodizing are phosphoric

and sulphuric acid, ammonium sulphate or sodium bicarbonate and solution containing fluoride

ions [10].

There are a few studies that reported the effect of a her applied voltages as well as the

individual role of calcium acetate on the morphology a crystalline structure of anodic oxide

film. Moreover, the characteristics of the precipitated apatite crystals, such as the size, shape,

number and the distribution during hydrothermal treatme ave not been fully understood.

This research focuses on the investigation of the anodic and hydrothermal TiO2 thin film

characteristics formed on the Ti6Al4V alloy surface in a phosphate and calcium containing

electrolyte under different voltage and calcium molarity. The morphology and the crystalline

structure both on the anodic and thermally treated surfaces oxide film were evaluated.

• • • •

CHAPTER II

STUDY OF REFERENCES

Metallic implant material for artificial hip has been wn and applied for a long time

ago. In 1923, Marius Smith-Petersen attempted to produ a cup arthroplasty using material such

as glass, celluloid resin and a Co-Cr alloy [11]. Co-Cr alloy then was chosen for half joint

arthroplasty since it provided a stiffer and harder material than methylmethacrylate. Stainless

steel then was discovered by Philip Wiles in 1938 as a useful metallic implant for total hip

replacement components. In the late 1980s, Ti-6Al-7Nb oy that improves clearance, metal

hardness and reproducible surface was introduced by Sulzer Brothers [12,13]. Then, the

development and the utilization of these metallic impl nts have grown sharply. However, Ti-6Al-

4V has been adopted as an implant biomaterial. It is preferred to stainless steel and Co-alloys

because of its lower modulus, superior biocompatibility nd corrosion resistance.

Recently, new titanium alloy compositions, specificall tailored for biomedical

applications, have been developed. The first generatio orthopedic alloys include Ti-6Al-7Nb,

Ti-5Al-2.5Fe and Ti-34Nb-7Zr-5Ta were developed in response to concerns relating to potential

cytotoxicity and adverse reaction with body tissues [14-15].

Table 1.1 shows the comparison between the three main o metallic biomaterials for

utilizing in othopaedic implants [16]. Biocompatibilit , mechanical properties and corrosion

resistance are the main requirements of their applications. Interestingly, the cost is not an

important issue of the cobalt and titanium base alloys hose in the stainless steel.

The superior properties of titanium and its alloys are proven to be potentially very

excellent metallic alloys for load bearing bioimplant pplications. Unfortunately, these alloys

have some disadvantages. Like most metals, titanium and its alloys exhibit poor osteoinductive

properties because of their bioinert feature [17]. They do not bond to bone at early stage of

implantation [18] and these materials undergo electroc l exchange and release metallic

ions in the physiological environment which is believe to the cause of implant failure [19].

• • • •

Therefore, surface modification of titanium and its al is essential preconditions for the

success of titanium alloy as biomaterial implants.

Table 1.2. shows further comparison of the three alloy in term of their mechanical

properties required in British standards for biomateri ls [20]. Although the porous parts are

mainly in compression, the orthopedic industry appears accept the capacity of the

wrought/cast materials to withstand the generated stre es, and hence all the material

recommendations specify the tensile requirements.

Table1.3. shows the strength levels and elastic moduli for orthopedic alloys, retained at

room temperature, in a standard tensile test [21]. The has been concern about the high elastic

modulus of the alloys as compared to bone, and the variable fatigue resistance of the metallic

implant. Both properties, if not optimized, may eventu y lead to prosthesis failure through

loosening of the implant in the vicinity of the implant m [22].

ASTM F-138(316 LDVM)

ASTM F-75ASTM F-799ASTM F-1537

(cast and wrought)

ASTM F-67 (ISO 5832/II)ASTM F-136(ISO 5832/II)

ASTM F-1295(Cast and wrought)

Fe(bal.), Cr(17-20)Ni(12-14), Mo(2-4)

Co(bal.), Cr(19-30)Mo(0-10), Ni (0-37)

Ti(bal.), Al(6)V(4), Nb(7)

Advantages Cost, availability processing

Wear resistance, Corrosion resistance,

Fatigue strength

Biocompatibility, corrosion minimum

Modulus, fatigue strength

Long term behavior high modulus

High modulusBiocompatibility

Power wear resistanceLow shear strength.

Temporary devices(fracture plates,

screws, hip nails)Used for THRs stems in UK (high Nitrogen)

Dentistry castingsProstheses stems

Load-bearingcomponents in TJR

(wrought alloys)

Used I THRs with modular

(Co-Cr-Mo or ceramic) femoral

headsLong-term, permanent

devices(nails, pacemakers)

Table 1.1. Characteristics of orthopedic metallic implant materials [23].

Stainless steel Cobalt-base alloys Ti and Ti-base alloys

Designation

Principal alloyingElements (wt%)

Disadvantages

Primary utilizations

• • • •

Table 1.2. Mechanical properties as listed in British standards [24].

Material Tensile Strength(MPa)

0.2% Proof Stress(MPa)

Elongation(%)

Table 1.3. Orthopedic alloys developed and/or utilized orthopedic implants and their mechanical properties [25].

Alloy designation YS (MPa) UTS (MPa) E (GPa)

316L Wrought316LN WroughtTi-6Al-4V**Unalloyed Ti***Ti-5Al-2.5FeCo-Cr-Mo castingCo-Cr-W-Ni WroughtCo-Ni-Cr-Mo WroughtCo-Ni-Cr-Mo-W-Fe-WroughtCo-Cr-Ni-Mo Forging

a) 90-800* b) 860-1100740

825-860240-680

900695860

a) 800 c) 1000-1200a) 600 d) 1000-1580

950

a) 190-285* b) 690430

76-780170-520

800450310

a) 300 c) 650-1000a) 276 d) 827-1310

450

a) 40* b) 1235

8-1010-30

108

10a) 40 c) 10-20a) 50 d) 5-18

65

All above minimum values are for bar stock only. Diffe t values are quoted for wire and strip products.a) Fully annealed, b) cold worked, c) hardened, d) col worked and aged.*Dependent on composition (i.e. higher values associated with increased N2 contents)**Values dependent on the grade of titanium chosen (1-4), each grade having an increasing amount of O2

***Dependent o bar thickness where the lower values are for bar <75nun in diameter.

Cp-TiTi-6Al-4VTi-6Al-7Nb (protasul-100)Ti-5Al-2.5FeTi-12Mo-6Zr-2FeTi-15Mo-5Zr-3AlTi-15Mo-2.8Nb-3AlTi-0/20Zr-0/20Sn-4/8Nb-2/4Ta+(Pd, N,O)Ti-ZrTi-13Nb-13ZrTi-15Mo-3Nb-0.3O (21SRx)Ti-35Nb-5Ta-7ZrTi-35Nb-5Ta-7Zr-0.4)Bone

692850-900

921914

1000-1060870-968

771726-990

Not available9001020530976

-

785960-970

10241033

1060-1100882-975

812750-1200

90010301020590

101090-140

105110105110

74-857582

Not availableNot available

79825566

10-40

(E=elastic modulus, YS=yield strength, UTS= ultimate strength

Calcium and phosphate containing electrolytes have received much attention in anodic

oxidation process for fabricating oxide film on the surface of titanium and its alloys. Izhizawa et

al. recognized a precipitation of phosphoric and calcium ions, which are the main elements of

bone, on the anodic and hydrothermal oxide titanium surface [26-28]. Zhu et al. developed

• • • •

anodic oxide film that has a crystalline structure. [2 Sun et al. reported that applied voltage

and time processing are important factors to prepare hydroxyapatite at a higher voltage of the

anodic process (micro-arc-oxidation) [30]. Park et al udied that the oxide film characteristics

related to the calcium acetate concentration in the el ctrolyte [31]. J. Baszkiewicza et al. studied

that Ca and P enriched oxide layers on titanium increased their in vitro corrosion resistances

[32].

Electrolyte concentration associates to the break down voltage during anodization process

which affects the film morphologies and its crystalline cture [31,33]. Generally, phosphate

and calcium ions in the electrolyte precipitate as an atite crystals to form a thin film on the

anodic oxide on the surface of Ti alloys that can improve their biocompatibilities and could be

possibly act as a further barrier against ion diffusion. The appearance of these apatite crystals can

be generated and accelerated by hydrothermal treatment Therefore, a study on optimizing the

electrolytes that containing calcium and phosphate is very important in order to obtain a coating

with specific morphologies and crystalline phases.

• • • •

••

••

CHAPTER III

AIM OF RESEARCH AND UTILIZATION

This study will be aimed at evaluating morphological and crystalline structures of anodic

and hydrothermal Titanium oxide TiO2 thin films formed on Ti6Al4V alloy in a mixture of

glycerophosphate disodium salt (GP) and calcium acetate (CA) solution at various forming

environments such as CA molarities (0.15, 0.30 and 0.45M), applied voltage (240~340 V) and

processing time (5 and 10 min). The Anodic oxide films TiO2 then will be hydrothermally treated

using an autoclave (ILSHIN Autoclave, Korea) at temper ure of 300 C and pressure of 9 MPa

for 2 hours. Morphological surface will be observed usi a scanning electron microscope (JSM-

5900, JEOL, Japan) and the crystal structure will also e characterized using an X-ray

diffractometer (Dmax III-A type, Rigaku Co., Japan) with scanning rate 4 /min. While chemical

composition will be analyzed using energy dispersive spectroscopy (EDS) in conjunction with

the scanning electron microscope. This research is to be used as an implant material where

excellent properties are required.

• • • •

CHAPTER IV

EXPERIMENTAL METHOD

4.1 Specimen preparation

4.2. Electrolyte preparation

Commercial Ti6Al4V plates with a dimension of 15x10x2 m3 is cut from a 60 mm

in diameter and 6 mm thickness disc and used as substrate. All plate surfaces are grounded with

successive finer SiC abrasive papers from 400, 600, 1000, 1200, 1500 and 2000# to remove

macro-level surface defects and contamination. These mirror finish surface samples then are

ultrasonically cleaned in ethanol and rinsed in distil water to expose a fresh surface just before

the anodization process. The samples then are dried usi a hair dryer for about two minutes.

The schematic illustration of as received commercial T 6Al4V alloy disc and its extraction to

obtain the plates are shown in Fig. 3.1.

The plate substrates are used as anode that rtially immersed in the electrolyte and

connected using a crocodile clip. In order to prevent ntact between electrode and electrolyte,

within 3 mm from the top of the plates are covered with eflon sealing tape and 12 mm are

exposed in the electrolyte. Here after, the total immersed surface area of the samples in the

electrolyte was about 254 mm2.

A commercial and pure titanium plate with a dimension of 20x10x1 mm3, is

connected with a cable and used as cathode in an electrolyte bath. One surface of this plate, 200

mm2, could be exposed in the electrolyte while other is covered with acrylic. The photograph of

the titanium cathode with its connecting cable is shown in Fig. 3.2.

Electrolyte containing Ca and P is reported to de a titanium oxide film that improves

biocompatibility of titanium with bone [34]. An electrolytic solution used in this study is a

mixture of Glycerol phosphate disodium salt hydrate (GP) and Calcium acetate hydrate (CA),

SIGMA-ALDRICH USA. The photograph of these electrolyte aterials is shown in Fig. 3.3.

• • • •

Fig. 3.1 Schematic illustration of as-received Ti6Al4V mmercial disc and the extracted plates

Fig. 3.2. The photograph of titanium cathode

Fig. 3.3. The photograph of the electrolyte materials.

• • • •

••

• • ••

•• ••

The electrolytes are prepared base on the study reporte by Park et al.[35]. The

electrolyte molarities and the anodizing conditions in detail are given in Table 3.1. During anodic

oxidation process, the electrolyte is maintained at room temperature and a magnetic stirrer is

used to eliminate the bubbles generated in the electrolytes.

A DC power supply device (Unicorn UP-1500, KOREA) is used in this experiment. Each

anodization process is carried out both in a constant c ent mode and in a constant voltage

mode. This device provides an automatic transition from the constant current to the constant

voltage when a preset maximum voltage is reached. The photograph of the DC power supply

used in this study is shown in Fig. 3.4.

Hydrothermal treatment is carried out to precipitate hydroxyapatite on the titanium oxide

film through a partial conversion of the amorphous laye of Ca and P [36]. After the anodizing,

the specimen is ultrasonically cleaned in distilled wate for 30 s and then dried at room

temperature. Hydrothermal treatment is conducted using n autoclave device (ILSHIN

Autoclave, KOREA), at a temperature of 300 C for 2 hours and at a pressure of 9 MPa. The

photograph of the hydrothermal device used in this study is shown in Fig. 3.5.

Surface micro-morphology of the titanium oxide films formed by anodic oxidation

treatment was observed using a scanning electron microscope (JSM-5900, JEOL, JAPAN).

X-ray diffractometer (Dmax III-A type, Rigaku Co., JAP will be used to analyze the

crystal structure of the anodized layer on the titanium surface. The scan range (2 ) is from 20 to

60 with the scanning rate 4 /min.

4.3. Equipments

4.3.1. DC power supply

4.3.2. Hydrothermal treatment

4.3.3. Microstructure characterization

4.3.4. Phase composition

• • • •

Fig. 3.4. The photograph of the DC power supply used in this study

Fig. 3.5. The photograph of the hydrothermal device.

4.4. Experimental set up

.

The schematic illustration of the experimental set up is shown in Fig.3.6. A glass picker

contains of electrolyte solution is put on an electrical stirring and heating plate. Ti6Al4V plate

• • • •

(+)(-)

samples will be used as working electrode (anode), sealed by Teflon tape and partially immersed

in electrolyte using the crocodile clip. The samples a connected to a positive pole of the DC

power supply. On the other side, the pure platinum plate is used as a counter electrode (cathode)

and connected to a negative pole.

During the anodization process, electrolyte is magnetically stirred at a speed of 50

rev/min and maintained at room temperature. Prior to the process, applied voltage, current

density and anodic holding time are set up according to e experimental parameter as it is shown

in detail in Table 3.1.

Fig. 3.6. Schematic illustration of the experimental set up.

(Crocodile clip)

(Working electrode)(Counter electrode)(Electrolyte)

(Magnetic stirrer)

(Heating plate)

(Temperature controller)

(Stirring controller)

(Glass picker)

(Teflon sealing tape)

• • • •

Table 3.1. Experimental parameters of anodic oxidation processes

GROUPELECTROLYTE

(Mol) VOLTAGE(Vol)

TIME(Min)

CURRENTDENSITY(mA/cm2)

CA GP

I 0.15 0.03

240

5 30

300

340

380

420

440

240

300

340

380

420

440

240

300

340

380

420

440

240

300

340

380

420

440

II 0.3 0.03 5 30

III 0.45 0.03 5 30

IV 0.15 0.03 10 30

5.1. Anodic titanium oxide film

5.1.1. Surface morphology

Fig. 3.1 SEM micrographs of Ti6Al4V

CHAPTER V

RESEARCH RESULT

.1. Anodic titanium oxide film

Fig. 3.1 SEM micrographs of Ti6Al4V surface alloy substrate at different magnificationalloy substrate at different magnification

The substrates surface were grounded with successive finer SiC abrasive papers up to

#2000 and ultrasonically cleaned in ethanol, rinsed in distilled water then dried for about two

minutes. SEM micrographs of surface morphology on the i6Al4V alloy plate b

oxidation was carried out is shown in Fig. 3.1.

grounding the surface are still exist. This surface images, was used as control surface

morphology.



minutes. SEM micrographs of surface morphology on the i6Al4V alloy plate b

oxidation was carried out is shown in Fig. 3.1. It can be seen that some grooves produced during




minutes. SEM micrographs of surface morphology on the i6Al4V alloy plate before anodic

t can be seen that some grooves produced during


• • • •

• • • •

SEM micrographs of anodized titanium oxide films on the surface of Ti6Al4V alloy substrate of

all specimens are shown in Fig. 3.2 to Fig. 3.24. These results show that TiO2 film was formed

by anodic oxidation process of all specimens. The oxide film surface morphologies are porous

like volcanic vents and rough. A porous structure of titanium biomaterial implant has been

widely reported elsewhere to have a beneficial for cel attachment, propagation and bone growth

[44]. While those a roughness surface was positively c lated to extent the contact with the

bone [55]. Process parameters such as electrolyte conc ration, applied voltage and processing

time affect the morphologies and crystalline structure he oxide films.

SEM micrographs of the specimens in Group I are shown Fig. 3.2 to Fig. 3.7,

respectively. The morphologies on the surface oxide films formed in this electrolyte

concentration are changed according to potential. When the anodization was carried out at 240 V,

titanium oxide films started to form slightly on the surface of the substrate. However, because of

the potential between anode and cathode was weak, the formation occurred locally and most of

the substrate surface has not been covered by the film. The microporous number and size on the

film were very few with irregular shaped. When the applied voltage was increased to 300 V, film

formation increased where rough oxide region expanded. The microporous in a more uniform

shape and distance were distributed to form a network long the substrate surface. When the

anodizations were conducted at 340 and 380 V, the films surface became rough and porous

where the microporous number and size increased steadily. Just above the surface film that

formed previously, a newer formation of surface film in a larger scaled of porosity occurred. This

gradual film formation made the morphology consisted of a multi level surface and caused the

increase of the roughness. Further increasing of potential to 420 and 440 V, the number of

microporous tends to be stable but the size slightly de reased. In higher magnification images,

shown in Fig.3.6 and Fig. 3.7, it can be seen that the microporous were distributed in a more

various sizes compared to those earlier formed at a lower voltages.

SEM micrographs of specimens in Group II are shown in Fig. 3.8 to Fig. 3.13. Doubling

CA concentration in the electrolyte to 0.30M changed the morphologies of the oxide film.

• • • •

Compared to the morphologies appeared earlier of the specimens in Group I, the morphologies

of the films were denser although it was formed at 240 V as it is shown in Fig. 3.8. Increasing

voltages up to 380 V, the microporous number and size increased steadily. However, above this

voltage, the morphologies did not change.

Further increasing in CA concentration to 0.45M did not change morphologies of the oxide

film. It can be seen on the SEM micrographs shown in Fig. 3.14 to Fig. 3.19 where the

morphologies are similar to those shown in Fig. 3.8 to Fig. 3.13 which are the morphologies of

oxide films formed in 0.30M-CA concentration. Interestingly, the morphologies did not change

although forming voltages was increased.

Prolong anodization processing time from 5 to 10 minut changed film morphologies as

SEM micrographs of the specimens in Group IV shown in . 3.20 to Fig. 3.25. Compared to

the morphologies obtained in Group I which anodized for 5 minutes, oxide films anodized for 10

minutes are denser with a slight larger size of porosi . These improvement possibly caused by

film formation occurred in longer time. Therefore, prolongation of anodization time is one of

important factor to obtain titanium oxide film with increased density and porosity. This process

was well known as thickening and densification during anodic oxidation. To confirm the effect of

anodization time to oxide film characteristic, further study in more various duration of time

should be carried out.

The above results demonstrated that morphologies of anodic titanium oxide films changed

when CA molarity increased from 0.15 to 0.30M, but further increasing to 0.45M, it did not

change. The increase of CA molarity decreased dielectric breakdown voltage. Within dielectric

breakdown range, the anodization voltage instabilities due to anodic spark deposition. The

decrease of electric breakdown voltages was more prono ed where CA molariy increased from

0.15 to 0.30M than from 0.30 to 0.45M. The difference the anodic forming voltages and

dielectric break down voltages demonstrated that the characteristics of the oxide films formed by

anodic oxidation differ greatly according to the electrolyte molarity that is used.

Fig. 3.2. SEM micrographs of the anodic titanium oxide filmand 0.15M-CA for 5 min and 240 V

3.2. SEM micrographs of the anodic titanium oxide film in electrolyte containing0 V.

containing 0.03M-GP

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SEM micrographs of the anodic titanium oxide film in electrolyte containing0 V.

containing 0.03M-GP

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