Embed Size (px)
Citation preview
ENHANCEMENT OF CORROSION RESISTANCE OF MAGNESIUM BY
ALLOYING, FLUORIDE TREATMENT AND NANO-HYDROXY APATITE
COATING FOR BIOMEDICAL APPLICATIONS
HAMID REZA BAKHSHESHI RAD
A thesis submitted in fulfilment of the
requirements for the award of the degree of
Doctor of Philosophy (Mechanical Engineering)
Faculty of Mechanical Engineering,
Universiti Teknologi Malaysia
JUNE 2013
ABSTRACT
Compared to the traditional metallic implant materials such as stainless steels, titanium alloys and cobalt chromium alloys, magnesium (Mg) has received great attention as biodegradable medical implants as it does not require second surgical procedure for removal. Mg and its alloys also possess suitable mechanical properties for orthopaedic and cardiovascular applications. However, clinical applications of Mg have been limited due to its relatively poor corrosion resistance, rapid degradation rate and hydrogen gas evolution in human body fluid. This research is aimed at decreasing the Mg degradation and corrosion rate by alloying with calcium (Ca) and zinc (Zn), surface treatment by hydrofluoric acid and coating with nanosized hydroxyapatite (HA) and brushite (DCPD) using electrodeposition method. The first stage of the research is to enhance the corrosion resistance of pure Mg by the addition of Ca (0.5 to 10 wt.%). In the second stage, Zn at different percentages (0.5 to 9 wt.%) was added to the binary Mg-Ca alloy to further enhance the corrosion properties. Both strategies were found to enhance the corrosion resistance of the alloy, however, the effect was not significant. To further enhance the corrosion resistance fluoride treatment by using different concentrations of hydrofluoric acid (35 and 40%) for the duration of 6 to 24 hrs were employed on binary Mg-Ca and ternary Mg-Ca-Zn alloys. Finally, nano-HA and Brushite were coated on the fluoride-treated specimens via electrochemical deposition (ED) method at different voltages (0.15 to 0.8 mA/cm2) and deposition times (10 to 60 min). Microstructural evolutions were characterized by XRD, AFM, FTIR, SEM, and TEM. Corrosion resistance was examined by potentiodynamic polarization and immersion test in Kokubo solution at room temperature. The results revealed that the grain size and dendrite cell size decreased with the addition of Ca and Zn contents into the binary and ternary alloys respectively. The addition of 0.5 wt.% Ca content was found to produce the lowest dissolution rate and the highest corrosion resistance. However, further addition of Ca led to an increased dissolution rate and pH value. The corrosion resistance of Mg-0.5Ca alloy was enhanced with the addition of up to1 wt.% Zn, but further addition produced the reverse effect. Mg-0.5Ca-lZn alloy, which has a-Mg+Ca2Mg6Zn3+Mg2Ca phases showed lower corrosion rate than those alloys with Zn/Ca atomic ratio higher than 1.23. After fluoride treatment the degradation rates of the alloys were significantly reduced compared to the untreated alloys. Electrochemical tests showed a significant decline in corrosion current density from 365.2 to 5.23 |xA/cm2 on Mg-0.5Ca-lZn alloys coated with composite nano-HA/MgF2. The application of composite coating of nano-HA/MgF2 on Mg-Ca- Zn alloys could be used to reduce the corrosion rates of Mg alloys for biodegradable medical applications.
ABSTRAK
Berbanding dengan implan tradisional yang dibuat dari bahan logam seperti keluli tahan karat, aloi titanium dan aloi kromium kobalt, magnesium (Mg) telah mendapat perhatian besar sebagai bahan biodegradasi implan perubatan kerana tidak memerlukan prosedur pembedahan kedua untuk penyingkiran implan. Mg dan aloinya memiliki sifat mekanikal yang juga sesuai untuk aplikasi ortopedik dan kardiovaskular. Walau bagaimanapun, aplikasi klinikal Mg adalah terhad disebabkan oleh mutu rintangan kakisan yang rendah, kadar degradasi yang tinggi dan evolusi gas hidrogen yang pantas dalam cecair badan manusia. Kajian ini bertujuan untuk mengurangkan kadar degradasi dan kakisan Mg secara pengaloian menggunakan unsur kalsium (Ca) dan zink (Zn), rawatan permukaan oleh asid hidrofluorik, dan salutan hydroxyapatite (HA) bersaiz nano dan brushite (DCPD) dengan kaedah elektroenapan. Peringkat pertama kajian adalah untuk meningkatkan rintangan kakisan Mg tulen dengan penambahan unsur Ca (0.5-10 wt.%). Pada peringkat kedua, unsur Zn pada peratusan yang berbeza (0.5-9 wt.%) ditambah kepada aloi binari Mg-Ca untuk menambah baik sifat kakisan. Kedua-dua strategi ini didapati beijaya menambah baik rintangan kakisan aloi, tetapi kesannya tidak ketara. Untuk mempertingkatkan lagi sifat rintangan kakisan, rawatan fluorida menggunakan kepekatan asid hidrofluorik yang berbeza (35 dan 40%) untuk tempoh 6 hingga 24 jam telah digunakan ke atas aloi binari Mg-Ca dan aloi pertigaan Mg-Ca-Zn. Akhimya, HA dan Brushite telah disalut pada spesimen yang telah menjalani rawatan fluorida dengan kaedah pemendapan elektrokimia (ED) pada voltan (0.15- 0.8 mA/cm2) dan masa pemendapan (10-60 min) yang berbeza. Evolusi mikrostruktur telah dilakukan menggunakan XRD, AFM, FTIR, SEM, dan TEM. Kerintangan kakisan telah diteliti menggunakan polarisasi potentiodynamic dan ujian rendaman dalam larutan Kokubo pada suhu bilik. Keputusan menunjukkan bahawa saiz bijian dan saiz sel dendrit menurun dengan penambahan kandungan Ca dan Zn ke atas aloi binari dan aloi pertigaan masing-masing. Penambahan 0.5 wt.% Ca dikenalpasti menghasilkan kadar keterlarutan terendah dan rintangan kakisan tertinggi. Walau bagaimanapun, penambahan Ca yang seterusnya membawa kepada peningkatan kadar keterlarutan dan nilai pH. Rintangan kakisan aloi Mg-0.5Ca telah dipertingkatkan dengan penambahan sehingga 1 wt.% Zn, tetapi penambahan seterusnya menghasilkan kesan yang sebaliknya. Aloi Mg-0.5Ca-lZn yang mempunyai fasa a-Mg+Ca2Mg6Zn3+Mg2Ca menunjukkan kadar kakisan lebih rendah berbanding dengan aloi lain yang mempunyai nisbah atom Zn/Ca lebih daripada 1.23. Selepas rawatan fluorida kadar degradasi aloi dikurangkan dengan ketara berbanding dengan aloi yang tidak dirawat. Ujian elektrokimia menunjukkan penurunan yang ketara dalam ketumpatan arus kakisan; 365.2-5.23 (iA/cm2 bagi aloi Mg-0.5Ca-lZn yang disalut dengan komposit nano-HA/MgF2. Salutan komposit nano-HA/MgF2 aloi pada Mg-Ca-Zn boleh digunakan untuk mengurangkan kadar kakisan aloi Mg untuk aplikasi perubatan biodegradasi.
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xii
LIST OF FIGURES xiv
LIST OF ABBREVIATIONS xxiv
LIST OF SYMBOLS xxvi
LIST OF APPENDICES xxviii
1 INTRODUCTION 1
1.1 Background 1
1.2 Problem Statement 4
1.3 Purpose of the Study 4
1.4 Objectives of the Research 5
1.5 Significance of the Research 5
1.6 Scope of the Research 6
2 LITERATURE REVIEW 7
2.1 Introduction 7
2.2 Biodegradable Materials 7
2.2.1 New Biodegradable Materials 8
2.3 Biodegradable Magnesium 10
2.3.1 History of Biodegradable Magnesium 10
2.3.2 Magnesium Properties 11
2.3.3 Magnesium and its Alloys for Biomedical
Applications 14
2.4 Magnesium and Its Alloys 15
2.4.1 Mg-Ca Binary Alloys 18
2.4.2 Mg-Zn Binary Alloys 21
2.4.3 Mg-Ca-Zn Ternary Alloys 24
2.5. Solidification of Magnesium Alloys 26
2.5.1 Thermal Analysis Method 27
2.6. Corrosion Characteristics of Mg and Its Alloys 28
2.6.1 Degradation Rate of Magnesium 31
2.6.2 Corrosion Types 33
2.6.3 Corrosion Products 37
2.7. Current Modification Methods 40
2.7.1 Conversion Coatings by Hydrofluoric Acid
(HF) 42
2.8 Calcium Phosphates 43
2.8.1 Dicalcium Phosphate Dihydrate - brushite 45
2.8.2 Hydroxyapatite 46
2.9 Coating for Magnesium Alloys 47
2.9.1 Biomimetic 59
2.9.2 Sol-gel Coating 50
2.9.3 Plasma Spraying 50
2.9.4 Dip Coating 51
2.9.5 Electrodeposition 52
3 RESEARCH METHODOLOGY 55
3.1 Introduction 55
3.2 Alloy Fabrication 59
3.3 Samples Preparation 61
3.4 Microstructural Characterization 63
3.4.1 SEM and TEM Studies 63
3.4.2 XRD Analysis 64
3.4.3 FTIR Analysis 64
3.4.4 AFM Analysis 65
3.5 Hardness Analysis 66
3.6 Thermal Analysis 66
3.7 Electrochemical Measurements 67
3.8 Immersion Test 68
3.8.1 Hydrogen Evolution 70
3.9 Fluoride Treatment 71
3.10 Electrodeposition of Calcium Phosphate Coatings 72
4 RESULTS AND DISCUSSION 74
4.1 Introduction 74
4.2 Evolution of the Microstructural Characteristics and
Corrosion Behaviour of Mg-xCa Alloys 74
4.2.1 Microstructure Characteristics 75
4.2.1.1 XRD Analysis 79
4.2.2 Hardness Analysis 80
4.2.3 Thermal Analysis 81
4.2.4 Electrochemical Measurements 89
4.2.5 Immersion Test 93
4.2.5.1 XRD Analysis of Corrosion Products 97
4.2.5.2 FTIR Analysis of Corrosion Products 98
4.2.5.3 pH Evaluation 101
4.3 Evolution of the Microstructural Characteristics and
Corrosion Behaviour of Mg-0.5Ca-xZn Alloy 102
4.3.1 Microstructure Analysis 102
4.3.1.1 XRD Analysis 108
4.3.2 Hardness Analysis 109
4.3.3 Thermal Analysis 111
4.3.4 Electrochemical Measurements 120
4.3.5 Immersion Test 126
4.3.5.1 XRD Analysis of Corrosion Products 131
4.3.5.2 FTIR Analysis of Corrosion Products 132
4.3.5.3 pH Evaluation 135
4.3.5.4 Hydrogen Evolution 136
4.3.6 In Vitro Degradation Behavior 137
4.4 Surface Modification of Mg-Ca and Mg-Ca-Zn
Alloys via Fluoride Treatment 140
4.4.1 Microstructure and Coating Characterization 143
4.4.1.1 XRD Analysis 148
4.4.1.2 AFM Analysis 150
4.4.2 Electrochemical Measurements 152
4.4.3 Immersion Test 156
4.4.3.1 XRD Analysis of Corrosion Products 162
4.4.3.2 FTER Analysis of Corrosion Products 165
4.4.3.3 pH Evaluation 167
4.4.4 In Vitro Degradation Mechanism 169
4.5 Hydroxyapatite and Brushite Coatings on Fluoride
Treated Mg-Ca-Zn Alloy 175
4.5.1 Electrodeposition of the Brushite Coatings 175
4.5.1.1 XRD Analysis of the Brushite 178
4.5.1.2 AFM Analysis of the Brushite 180
4.5.1.3 Surface Morphology Evaluation 181
4.5.2 Microstructure and Coating Characterization
of Composite Coated Alloys 185
4.5.2.1 XRD Analysis 190
4.5.2.2 FTIR Analysis 192
4.5.2.3 AFM Analysis 194
4.5.3 Electrochemical Measurements 196
4.5.4 Immersion Test 200
4.5.4.1 XRD Analysis of Corrosion Products 202
4.5.4.2 FTIR Analysis of Corrosion Products 203
4.5.4.3 pH Evaluation 205
4.5.4.4 Hydrogen Evolution 206
5 CONCLUSIONS AND RECOMMENDATIONS 209
5.1 Introduction 209
5.2 Conclusions 209
5.3 Recommendations for Future Work 212
REFERENCES
Appendices A-D
213
230-233
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Mechanical properties and degradation rate of biodegradablepolymers as a comparison with bone, ceramics and metals
2.2 Mechanical properties of different type of magnesium alloys compared with tissue and traditional biomaterials
2.3 Influence of alloying elements on properties of Mg alloys at ambient temperatures
2.4 Corrosion types of various magnesium alloys in MEM solution
2.5 Example of calcium phosphate phases and their major properties
13
16
34
44
2.6 Different techniques to deposit HA coatings 48
3.1 Overall experimental details procedure of the research 58
3.2 Nominal and actual chemical compositions of Mg-xCa alloys 60
3.3 Actual chemical compositions of the Mg-0.5Ca and Mg-0.5Ca-xZn alloys 61
3.4 Etchants used for characterisation of Mg alloys 62
3.5 Chemical composition of the Kokubo simulated body fluid (SBF) compared to the human blood plasma 69
3.6 Amounts and formula weights of reagents for preparing 1000ml of SBF 69
4.1 Cooling curve parameters for the pure Mg and Mg-xCa alloys 85
4.2 Electrochemical parameters of specimens in Kokubo solution attained from the polarization test 90
4.3 The characteristic parameters identified for Mg-0.5Ca and
Mg-0.5Ca-xZn alloys during solidification by thermal analysis
4.4 Electrochemical parameters of Mg-0.5Ca and Mg-0.5Ca- xZn specimens in Kokubo solution attained from the polarization test
4.5 Electrochemical parameters of untreated and fluoride coated specimens in Kokubo solution attained from the polarization test
4.6 Hydrogen and corrosion observation of untreated and fluoride treated after immersed in Kokubo solution for 10 days
4.7 Effect of current density and deposition time on deposit weight of brushite
4.8 Electrochemical parameters of untreated, fluoride treated and composite coated specimens in Kokubo solution attained from the polarization test
4.9 pH value, Hydrogen and degradation observation of untreated, fluoride treated and composite coated specimens after immersed in Kokubo solution for 10 days
123
156
173
176
199
LIST OF FIGURES
FIGURE NO. TITLE
2.1 Potential applications of magnesium-based materials to:(a) osteosynthesis, (b) cardiovascular stents, and (c) wound-closing devices for stomach trauma
2.2 Mechanical properties of as-cast pure Mg and M g-lX alloy ( X= Al, Ag, In, Mn, Si, Sn, Y, Zn and Zr) specimens s at room temperature. Extracted from reference [49]
2.3 Mechanical properties of as-cast, as-rolled and as-extruded Mg-ICa alloy as well as as-cast Mg-2Ca alloy and as- cast Mg-3Ca alloy at room temperature
2.4 Mg-Ca binary phase diagram
2.5 Potentodynamic polarization curves of pure Mg and Mg- Zn alloys
2.6 Mg-Zn binary phase diagram
2.7 Typical stress -strain curve of as cast Mg-xZn-ICa alloys
2.8 The ternary phase diagram of as-cast Mg-Ca-Zn alloy
2.9 Free corrosion potentials of some construction metals in neutral sodium chloride solution
2.10 Pourbaix diagram of magnesium in water at 25C
2.11 The hydrogen evolution volumes of as-cast pure Mg and M g-lX alloys ( X = Al, Ag, In, Mn, Si, Sn, Y, Zn and Zr) specimens immersed in SBF and Hank’s solution for 500 h
2.12 Localized corrosion morphology of AM50 magnesium alloy
PAGE
14
18
20
21
22
23
25
26
30
31
32
34
2.13 SEM micrographs of AZ80 magnesium alloy after immersion in 0.5 wt.% NaCl solution: (a) 4 h immersion
shows large pits and (b) 24 h immersion shows coalescence of pits forming trenches 36
2.14 Effects of impurities concentrations on the corrosion rateof AZ91 magnesium alloy 3 6
2.15 Mechanism of micro-galvanic corrosion proposed for the WEXX alloys: (a) formation of magnesium hydroxide layer on the surface of the a-Mg matrix and (b) localised micro-galvanic corrosion at preferential areas 37
2.16 Build-up of very voluminous Ca-rich oxide product that forms as a result of corrosion in SBF at 37 °C. The productis insoluble 38
2.17 Corroded surface after immersion in Hank’s solution for(a) HP Mg, (b) Mg2Zn0.2Mn, (c) ZE41 and (d) AZ91 39
2.18 SEM images of (a) phosphate coating, (b) cerium coatingand (c) stannate coating 41
2.19 SEM images of the fluoride-coated Mg-Zn (a, b) the embedded image in Figure, lb is the magnified morphology of the pore within the white rectangle 43
2.20 Crystal structure of brushite DCPD with orientation of monoclinic crystal in b-plane 45
2.21 The super cell of hydroxyapatite in PI space group after removing excess OH groups 47
2.22 Schematic of biomimetic coating: (a) simple biomimeticcoating of an amorphous calcium deficient carbonated apatite from SBF (usually the SBF ion concentration for biomimetic coating is 5 to 10 times higher than the normal SBF ion concentration); (b) biomimetic co-precipitation ofdrug/growth factor 49
2.23 Schematic set up of arc plasma spray 51
2.24 Schematic of dip coating technique 52
2.25 Electrophoretic deposition cell showing positively charged particles in suspension migrating towards the negative electrode 54
3.1 Overall experimental activities flowchart of the research 57
3.2 The process of preparing Mg-xCa alloy specimens 59
3.3 The process of preparing Mg-0.5Ca-xZn alloy specimens 59
3.4
3.5
3.6
3.7
3.8
3.9
3.10
3.11
3.12
3.13
4.1
4.2
4.3
Casting produced from two different moulds for preparation of specimen. Specimen produced from casting a) plate and b) cylindrical rod 60
Schematic drawing of specimens cut from Mg alloys the castings: a, b) cylindrical rod and c) rectangular plate 62
Equipment used for analysing the specimens microstructure a) Field emission scanning electron microscope and b) Transmission electron microscope 63
Fourier transform infrared spectroscopy used to determine the surface functional groups of the specimens 64
Atomic-force microscopy spectroscopy used to evaluate the surface topography of the composite coated, fluoride coated and untreated specimens 65
Schematic illustration of thermal analysis set up with stainless steel mould and thermocouples 67
a) The electrochemical experiment set up, b) Schematic of three-electrode electrochemical testing cell and c) Prepared specimen for corrosion test 68
Exterior views of the specimens immersed in Kokubo solution a) Mg-Ca alloy and b) Mg-Ca-Zn alloy 69
Schematic illustration of the experimental setup for hydrogen gas evolution measurement 71
Schematic arrangement of the electrodeposition cell for the deposition of nano-HA on Mg-Ca-Zn alloy 73
Optical micrographs of specimens (a) Mg pure, (b) with different calcium content: 0.5, (c) 1.25, (d) 2.5, (e) 5, (f)10 wt.%, (g) high magnification of Mg-5Ca alloy and(h) high magnification of Mg-1 OCa alloy 76
SEM micrographs of (a) Mg-0.5Ca, (b) Mg-1.25Ca, (c)EDS analyses of area 1, (d) EDS analyses of area 2, (e) Mg-2.5Ca, (f) Mg-5Ca, (g) EDS analyses of area 3, (f)EDS analyses of area 4 (i) Mg-1 OCa, (j) high magnification of framed region indicated in Figure 4.2i 78
X-ray diffraction patterns of (a) pure Mg, (b) various Mg-Ca alloys with different calcium content: 0.5, (c)1.25, (d) 2.5, (e) 5, (f) 10 wt.% 80
4.4 Effect of calcium content on the hardness value of M g- Ca alloys 81
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.13
4.14
4.15
Cooling curves for the Mg-xCa alloys (x = 0, 1.25, 2.5 and 5) with two phase reactions 82
Thermal analysis results of (a) pure Mg and Mg-Ca alloys with different calcium content; (b) 0.5, (c) 1.25,(d) 2.5, (e) 5 and (f) 10 wt.% 84
Cooling curves of the center and wall of the specimen with its corresponding equivalent temperature difference (AT=TW-TC) for Mg-Ca alloys with different calcium content (a) 1.25, (b) 2.5, (c) 5 and (d) 10 wt.% 86
The effect of Ca content on solid fraction at dendrite coherency point and T n -T Dcp 88
Potentiodynamic polarization curves of Mg and Mg-Ca alloy in Kokubo solution 90
SEM micrographs after polarization test in Kokubo solution (a) pure Mg, and b) Mg-xCa alloys with various Ca content; 0.5 (c) 1.25, (d) 2.5, (e) 5 and (f) 10 wt.% 92
SEM micrographs showing the occurrence of pitting and peeling in pure Mg and Mg-xCa after being immersed in Kokubo solution for 84 h. Mg-1 OCa was immersed in Kokubo solution for 6 h. (a) pure Mg, (b) Mg-0.5Ca, (c) Mg-1.25Ca, (d) Mg-2.5Ca, (e) EDS analyses of area 1,(f) EDS analyses of area 2, (g) Mg-5Ca, (h) Mg-lOCa,(i) EDS analyses of area 3 and (j) EDS analyses of area 4. 96
X-ray diffraction patterns of (a) pure Mg, and Mg-xCa alloys with various Ca additions (b) 0.5, (c) 1.25, (d)2.5, (e) 5 and (f) 10 wt.% immersed in Kokubo solution for 144 h 98
FTER absorption spectra of (a) pure Mg and Mg-xCa alloys with various Ca content: (b) 0.5, (c) 1.25, (d) 2.5,(e) 5 and (f) 10 wt.% with immersion duration of 144 h 100
The variation of the pH value in a Kokubo solution as a function of immersion time for pure Mg and Mg-xCa alloys with different calcium content 101
Optical micrographs of specimens (a) Mg-0.5Ca and Mg-0.5Ca-xZn alloys with various Zn content: (b) 0.5,(c) 1, (d) 3, (e) 6, (f) 9 wt.% 104
4.16
4.17
4.18
4.19
4.20
4.21
4.22
4.23
4.24
4.25
4.26
4.27
SEM micrographs of a) Mg-0.5Ca, (b) Mg-0.5Ca- 0.5Zn, (c) Mg-0.5Ca-lZn, (d) Mg-0.5Ca-3Zn, (e) EDS analysis of point 1, (f) EDS analysis of point 2, (g) M g- 0.5Ca-4.5Zn, (h) Mg-0.5Ca-6Zn, (i) EDS analysis of point 3 and (j,k) Mg-0.5Ca-9Zn alloys 107
X-ray diffraction patterns of (a) Mg-0.5Ca and M g- 0.5Ca-xZn alloys with various Zn content: (b) 0.5, (c) 1,(d) 3, (e) 4.5, (f) 6 and (g) 9 wt.% 109
Effect of Zn amount on the hardness value of Mg- 0.5Ca-xZn alloys 110
Cooling curves of the Mg-0.5Ca-xZn alloys (x = 0.5, 1,6 and 9 wt.%) with four solidification reactions 111
Cooling curve from the thermal analysis (a) Mg-0.5Ca,(b) Mg-0.5Ca-0.5Zn, (c) Mg-0.5Ca-lZn, (d) M g- 0.5Ca-6Zn and (e) Mg-0.5Ca-9Zn alloys 113
Schematic plots of solidification stage of Mg-0.5Ca- xZn alloy with Zn solute distribution 114
The changes of (AT/At) versus time for (a) Mg-0.5Ca and Mg-0.5Ca-xZn alloys with various Zn content: (b)0.5, (c) 1, (d) 3, (e) 4.5, (f) 6 and (g) 9 wt.% 117
Cooling curves at the center and wall of the specimen and the equivalent temperature difference of Mg-0.5Ca- xZn for (a) 3, (b) 4.5, (c) 6 and (d) 9 wt.% Zn 118
The effect of Zn contents on solid fraction at dendrite coherency point 119
Potentiodynamic polarization curves of Mg-0.5Ca-xZn alloys specimens immersed in Kokubo solution 122
SEM micrographs showing surface morphology characteristics of Mg-0.5Ca-xZn alloys with various Zn content (a) 0.5, (b) 1, (c) 3, (d) 4.5, (e) 6 and (f) 9 wt.% after polarization in Kokubo solution 125
SEM micrographs of (a) Mg-0.5Ca (b) Mg-0.5Ca- 0.5Zn, (c) Mg-0.5Ca-lZn, (d) EDS analysis of point 1,(e) Mg-0.5Ca-3Zn, (f) Mg-0.5Ca-4.5Zn, (g) M g- 0.5Ca-6Zn, (h,i) Mg-0.5Ca-9Zn alloys, (j) EDS analysis of point 2, and (k) EDS analysis of point 3 after samples immersed for duration of 144 h in Kokubo solution 129
4.28
4.29
4.30
4.31
4.32
4.33
4.34
4.35
4.36
4.37
4.38
4.39
Schematic illustration of corrosion mechanism for M g- Ca-Zn alloys (a) the galvanic corrosion between Mg and secondary phases, (b) formation of the thin protective film of Mg(OH)2, (c) formation of hydroxyapatite layer and (d) formation of needle shape hydroxyapatite layer on M g-0.5Ca-l Zn alloys 131
X-ray diffraction patterns of Mg-0.5Ca-xZn alloys with various Zn content: a) 0.5 (b) 1, (c) 3, (d) 4.5, (e) 6, (f) 9 wt.% immersed in Kokubo solution for 144 h 132
FTIR absorption spectra of (a) Mg-0.5Ca and M g- 0.5Ca-xZn alloys with various Zn content: (b) 0.5, (c) 1,(d) 3, (e) 4.5, (f) 6 and (g) 9 wt.% with immersion duration of 144 h in Kokubo solution 134
The variation of the pH value in Kokubo solution as a function of immersion time for Mg-0.5Ca-xZn alloys with different Zn content 136
Hydrogen evolutions of the Mg-0.5Ca-xZn alloys immersed in Kokubo solution for duration of 240 h 137
Corrosion rate obtained by weight loss of Mg-0.5Ca- xZn alloys as a function of Zn content in Kokubo solution for duration of 3, 7 and 14 days 139
The variation of mass gain of Mg-0.5Ca and Mg-0.5Ca- lZn treated specimens in HF solution as a function of soaking time 142
Image of (a) 35% HF and (b) 40% HF specimens after fluoride treatment 142
SEM micrographs of (a) untreated Mg-0.5Ca alloy, (b)35% HF, (c) 40% HF and (d) EDS spectrum of point 1 144
SEM micrographs of (a) untreated Mg-0.5Ca-lZn alloy,(b) 35% HF, (c) 40% HF and (d) EDS spectrum of point 2 145
Element mapping of Mg, Ca, O, C and F on Mg-0.5Ca specimens after fluoride treatment (a) 35% HF, (b) 40%HF, (c) EDS of point 1, (d) EDS of point 2 (red—>Mg;Ca—>blue; O—>-green; C—>violent; F—>yellow) 146
Element mapping of Mg, Ca, O, C and F on Mg-0.5Ca- lZn specimens after fluoride treatment (a) 40% HF, (b)35% HF, and (c) EDS of point 1 147
4.40
4.41
4.42
4.43
4.44
4.45
4.46
4.47
4.48
4.49
4.50
X-ray diffraction patterns of Mg-0.5Ca fluoride treated(a) 40% HF, (b) 35% HF and (c) untreated specimen 149
X-ray diffraction patterns of Mg-0.5Ca-lZn fluoride treated (a) 40% HF, (b) 35% HF and (c) untreated specimen 149
AFM images of (a) untreated Mg-0.5Ca, (b) untreated Mg-0.5Ca-lZn, (c) treated Mg-0.5Ca with 35% HF, (d) treated Mg-0.5Ca-lZn with 35% HF and e) treated Mg- 0.5Ca with 40% HF and (f) treated Mg-0.5Ca-lZn with 40% HF 151
Potentiodynamic polarization curves of untreated, 35%HF and 40% HF treated Mg-0.5Ca alloy in Kokubo solution 154
Potentiodynamic polarization curves of untreated, 35%HF and 40% HF treated Mg-0.5Ca-lZn alloy in Kokubo solution 154
SEM micrographs of the Mg-0.5Ca and Mg-0.5Ca-lZn alloys after the potentiodynamic polarization tests: (a,b)35% HF, (c,d) 40% HF and (e,f) EDS spectrum of point l an d 2 155
SEM micrograph indicates surface morphology of Mg- 0.5Ca alloy after being immersed in Kokubo solution for 168h; (a,b) untreated Mg-0.5Ca, (c,d) treated with 35% HF, (e,f) EDS analysis of point 1 and 2, (g,h) treated with 40% HF and (j,k) EDS analysis of point 3 and 4 159
SEM micrograph indicates surface morphology of Mg-0.5Ca-lZn alloy after being immersed in Kokubo solution for 168h; (a,b) untreated Mg-0.5Ca-lZn, (c,d) treated with 35% HF, (e,f) EDS analysis of point 5 and6, (g,h) treated with 40% HF and (j,k) EDS analysis of point 7 and 8 162
X-ray diffraction patterns of (a) untreated Mg-0.5Ca specimen (b) fluoride treated alloy with 35% HF and (c)40% HF after immersion in Kokubo solution for 196 h 164
X-ray diffraction patterns of (a) untreated Mg-0.5Ca- lZn specimen (b) fluoride treated alloy with 35% HF and (c) 40% HF after immersion in Kokubo solution for 196 h 164
FTIR absorption spectra of (a) untreated Mg-0.5Ca
4.51
4.52
4.53
4.54
4.55
4.56
4.57
4.58
4.59
4.60
4.61
4.62
4.63
specimen (b) fluoride treated alloy with 35% HF and (c)40% HF after immersion in Kokubo solution for 196 h 166
FTIR absorption spectra of (a) untreated Mg-0.5Ca-lZn specimen (b) fluoride treated alloy with 35% HF and (c)40% HF after immersion in Kokubo solution for 196 h 166
The variation of the pH value in Kokubo solution as a function of immersion time for untreated Mg-0.5Ca and treated specimen 168
The variation of the pH value in Kokubo solution as a function of immersion time for untreated Mg-0.5Ca-lZn and treated specimen 168
The mass loss of untreated Mg-0.5Ca alloy and treated specimens versus immersion time in Kokubo solution 171
The mass loss of untreated Mg-0.5Ca-lZn alloy and treated specimens versus immersion time in Kokubo solution 171
Images of untreated and fluoride treated Mg-0.5Ca alloys (Dark color: HF treated; Light color: untreated alloy) after immersed in Kokubo solution at 37°C for (a)3 days, (b) 7 days and (c) 10 days 174
Images of untreated and fluoride treated Mg-0.5Ca-lZn alloys (Dark color: HF treated; Light color: untreated alloy) after immersed in Kokubo solution at 37°C for (a)3 days, (b) 7 days and (c) 10 days 174
Effect of current density on deposit weight of brushite at constant deposition time of 60 min 177
Effect of electrodeposition time on deposit weight of brushite at constant current density of 0.4 mA/cm2 177
XRD pattern of brushite coating on Mg alloy at different current density (a) 0.15 mA/cm2, (b) 0.25 mA/cm2, (c) 0.4 mA/cm2 and (d) 0.8 mA/cm2 179
XRD pattern of brushite coating on Mg alloy at different electrodeposition time (a) 10 min, (b) 20 min,(c) 40 min and (d) 60 min 179
AFM image of brushite coating on Mg alloy at different current density (a) 0.15 mA/cm2, (b) 0.25 mA/cm2, (c)0.4 mA/cm2 and (d) 0.8 mA/cm2 181
SEM image of DCPD coating on Mg alloy at different
4.64
4.65
4.66
4.67
4.68
4.69
4.70
4.71
4.72
4.73
4.74
current density and corresponding EDS (a,b) 0.15 mA/cm2, (c,d) 0.25 mA/cm2, (e,f) EDS analysis of point A and B (g,h) 0.4 mA/cm2 and (j,k) 0.8 mA/cm2 and (m,n) EDS analysis of point C and D
TEM micrographs of the powder scraped from the brushite coating on Mg alloy at different current density (a) 0.15 mA/cm2 and (b) 0.8 mA/cm2
SEM images of the surface of (a) untreated Mg-0.5Ca- 6Zn alloy, (b) fluoride coating, (c) EDS analysis of point 1, (d) DCPD/MgF2 composite coating,(e) nano-HA/MgF2 composite coating specimen, (g) EDS analysis of point 2 and (h) EDS analysis of point 3
The cross-sectional SEM image of (a) DCPD/MgF2 composite coating, (b) HA/MgF2 composite coating and(c) fluoride coated specimen
The cross-sectional SEM images of the top layer of (a) HA coating and (b) DCPD coating
TEM micrographs of the powder scraped from the (a) DCPD coating, and (b) HA coating on Mg-Ca-Zn alloy
X-ray diffraction patterns of (a) untreated alloy, (b) fluoride coating, (c) DCPD/MgF2 composite coating and(d) nano-HA/MgF2 composite coating specimen
The FTIR characteristic bands of (a) DCPD/MgF2 composite coating and (b) nano-HA/MgF2 composite coating specimen
AFM topography of (a) untreated alloy, (b) fluoride coating, (c) DCPD/MgF2 composite coating, (d) nano- HA/MgF2 composite coating specimen
Potentiodynamic polarization curves of untreated alloys and three coated specimens in Kokubo solution
SEM images of specimens immersed in Kokubo for 192 h (a) untreated, (b) fluoride coating, (c) EDS analysis of point 1, (d) DCPD/MgF2 composite coating, (e) nano- HA/MgF2 composite coating, (f) EDS analysis of point2, (g) EDS analysis of point 3
X-ray diffraction patterns attained from the corrosion products of (a) untreated alloy, (b) fluoride coating, (c) DCPD/MgF2 composite coating and (d) nano-HA/MgF2 composite coating specimen after full immersion
183
185
187
189
190
190
191
194
195
197
4.75
4.76
4.77
exposure to Kokubo solution for 192 h duration 203
FTIR absorption spectra attained from the corrosion products of (a) untreated alloy, (b) fluoride coating, (c) DCPD/MgF2 composite coating, and (d) nano-HA/MgF2 composite coating specimen after full immersion exposure to Kokubo solution for 192 h duration 204
Change in pH of the Kokubo solution during immersion of untreated, fluoride coated, DCPD/MgF2 and nano- HA/MgF2 composite coated specimens for duration of 192 h 206
Hydrogen evolution of the untreated, fluoride coated, DCPD/MgF2 and nano-HA/MgF2 composite coated specimens immersed in Kokubo solution for duration of 240 h 208
LIST OF ABBREVIATIONS
CA-CCTA Computer Aided Cooling Curve Thermal Analysis
CCA Cooling Curve Analysis
DCP Dendrite Coherency Point
EDX Energy Dispersive X-ray
FESEM Field Emission Scanning Electron Microscopy
OM Optical Microscopy
FTIR Fourier-Transformed Infrared Spectroscopy
SEM Scanning Electron Microscopy
TA Thermal Analysis
TEM Transmission Electron Microscopy
AFM Atomic-Force Microscopy
UTS Ultimate Tensile Strength
UCS Ultimate Compressive Stress
XRD X-ray Diffraction
SBF Simulated body fluid
HA Hydroxyapatite
DCPD Dicalcium Phosphate Dihydrate (Brushite)
ED Electrodeposition
SiC Silicon Carbide
VHN Vickers Microhardness
SCE Saturated Calomel Electrode
HF Hydrofluoric Acid
PBR Pilling-Bedworth Ratio
Ca-P Calcium Phosphates
MgF2 Magnesium Fluoride
Mg(OH)2 Magnesium Hydroxide (Brucite)
DMEM Dulbecco’s Modified Eagle Medium
MEM Minimum Essential Medium
PBS phosphate buffered saline
ACP Amorphous Calcium Phosphate
OCP Octacalcium Phosphate
TCP Tricalcium phosphate
CDHA Calcium-Deficient Hydroxyapatite
PLLA Poly L-Lactic Acid
PGA Polyglycolic Acid
PEO Polyethylene Oxide
mpy Mils Per Year
P 0 43 Phosphate
OH" Hydroxide
C032- Carbonate
LIST OF SYMBOLS
Zre - Impedance
Cp - Specific heat
foe? - Solid fraction at dendrite coherency point
/s - Solid fraction
/ l - Liquid fraction
T - Temperature
Ts - Start of solidification temperature
Te - End of solidification temperature
Teu - Eutectic temperature
ts - Start of solidification time
te - End of solidification time
AT - Solidification range
At - Total solidification time
Tn - Nucleation temperature
tx - Nucleation time
T dcp - Coherency temperatures
a-Mg - Primary magnesium dendrite
p - Density
°C - Centigrade degree
/? - Diffraction peak width at mid-height,
t - Average crystallite size (mn)
6 - Bragg diffraction angle
A - X-ray wave length
Ra - Average roughness
R ms - Mean spacing roughness
icorr - Corrosion current density
Ecorr - Corrosion potential
fie - Cathodic Tafel slops
Pa - Anodic Tafel slopes
RP - Polarization resistance
Pi - Corrosion rate
Epit - Pitting potential
Q - Growth restricted factor
m - Gradient of the liquidus line of a binary alloy
Co - Bulk concentration of the solute
k - Equilibrium partition coefficient of the solute
Qs - Rate of heat released
Tf - Final temperature
Cp - Specific heat of the alloy
Tw - Temperature at wall thermocouple
Tc - Temperature at centeral thermocouple
LIST OF APPENDICES
APPENDIX TITLE
A Screen view of DEWESoft 7.5 Data acquisitionsoftware during recording
B Screen view of Autolab software for fitting andextracting results from the Tafel slopes
C SEM micrographs of porous Mg(OH)2 on thespecimen surface immersion in SBF
D List of publications
PAGE
230
231
232
233
INTRODUCTION
1.1 Background
Metallic materials have fundamental roles for repair or replacement of bone
tissue particularly for load-bearing applications due to their good fracture toughness
and high mechanical strength [1]. However, the release of toxic metallic ions during
corrosion has limited their applications as implant materials [2]. This released ion
can result in inflammatory, which in turn decrease biocompatibility [3]. Compared to
the traditional metallic implant materials such as titanium alloys, stainless steel and
cobalt-chromium alloys, biodegradable implant materials do not require second
surgical procedure to remove them once the bone healed and they are replaced by
natural tissue. In addition, second surgical procedures always have risk and cost
involved [4]. Furthermore, the presence of permanent implants in the human body
may cause allergy and sensitization.
Recently, polymeric-based biodegradable materials, mostly polylactic have
shown a feasible approach to the development of completely degradable devices for
biomedical applications. However, polymers can create significant adverse reactions
and have inadequate mechanical strength, thus their applications are limited to low
load-bearing applications [5]. In addition, polymeric implants are more expensive
compared to the typical metallic implants [4,5], As an alternative to biodegradable
polymer implants is the biodegradable metallic implants which received great
attention owing to the high load-bearing capacity [4], Magnesium and its alloys have
shown great potential in cardiovascular applications where temporary stents are
required. They have also been used as bone substitute materials owing to their
biocompatibility and biodegradability and have similar mechanical properties with
natural bone. Mg is one of the fundamental elements in the human body and the
fourth most dominant component in the human serum [6], According to Song [5] a2+
normal adult consumes about 300-400 mg of Mg every day and an excess of Mg is
not harmful since it excretes through urine. Mg as biodegradable material is
lightweight (1.74 g/cm3), which is 1.6 and 4.5 times lighter than that of aluminum
and steel respectively.
Magnesium fracture toughness is higher compared to bio-ceramics such as
hydroxyapatite, and has close elastic modulus and compressive yield strength to
natural bone [3, 5], However, applications of Mg alloys are limited due to the
relatively poor corrosion resistance, the release of hydrogen gas and a relatively high
degradation rate when exposed to human body fluid [7, 8]. These characteristics lead
to a decline in the mechanical properties of pure Mg before new tissues are properly
and adequately healed. Mg alloy as implant can maintain the mechanical stability for
around 6 to 8 weeks, while implant need to maintain its mechanical integrity in the
body for about 12 weeks [9]. Thus, various approaches have been employed to
enhance corrosion resistance of pure Mg such as alloying, surface treatment and
coating.
Most of the research reported on biodegradable magnesium alloys for
biomedical application contains aluminium (Al) and/or rare earth (RE) elements.
However, Al could cause nerve toxicity and RE could lead to hepatotoxicity [10, 11].
Other alloying elements such as zirconium (Zr) may lead to lung, liver,
nasopharyngeal and breast cancers [5]. The addition of neodymium (Nd) and yttria
(Y) into Mg alloys resulted in a disturbance at the implantation site [10, 11]. Clearly,
to guarantee the biosafety of biodegradable materials, the constitutional elements of
magnesium-based alloys should be toxic free [7,10]. To address this point, Ca and Zn
were found to be toxic free.
Calcium is one of the main elements in the human bone and release of Mg
and Ca ions may improve the bone healing process [12]. Calcium, with a density of
1.55g/cm3, is also lightweight material similar to magnesium (1.74 g/cm3) and will
maintain its specific properties. The relatively reasonable cost of Ca should also
attract its use as alloying element in medical applications [13]. Previous research also
has shown that the corrosion resistance of Mg-Ca alloys increased significantly with
the addition of 1 wt.% Ca [14]. Besides, the addition of Zn into magnesium alloys is
very effective in increasing their mechanical strength [15, 16]. Zinc is also generally
known to increase age hardening response, produce intermetallic compounds, refine
grain size and improve castability and mechanical properties such as tensile and
hardness of Mg-Ca [17-19], The effect of Zn on corrosion resistance of Mg-Ca was
not known for biomedical applications. Thus, there is a need to investigate the effect
of Zn addition on Mg-Ca corrosion rate.
Since ensuring the implant remains its function until after the bone heals,
corrosion resistance of Mg-Ca and Mg-Ca-Zn alloys should be enhanced further by
double protective film composed of inner-layer. Several reports have shown that
decreasing the corrosion rate of Mg in simulated body fluids is possible by surface
treatment methods [20-23]. Surface treatment by hydrofluoric acid (HF) was found
to be effective in increasing corrosion resistance at 48% concentration [4]. However,
protection provided by the MgF2 layer at that concentration was high at the initial
phase, but stabilized with time and became less effective. Other HF concentrations
and immersion time was not known to affect corrosion rate of Mg-Ca and Mg-Ca-Zn
alloys. Micro sized hydroxyapatite (HA) as the top layer coat by electrodeposition
was used without inter-layer on Mg-Ca substrates with the intention to prolong
protection. It was found effective in increasing the corrosion resistance, however the
hydrogen gas evolution was beyond the tolerance limit of human body [24, 25].
Therefore, this research is aimed at addressing a comprehensive use of
alloying, fluoride treatment and nano-calcium phosphate coating in the form of nano-
HA/MgF2 and DCPD/MgF2 composite coating to increase the corrosion resistance
and minimize hydrogen production of Mg alloys for use in biomedical implant.
1.2 Problem Statement
Magnesium alloys as biodegradable materials possess several advantages
compared to the current metallic materials and biodegradable plastics and ceramics.
Magnesium benefits include higher fracture toughness over ceramic biomaterials,
higher strength them biodegradable plastics, and higher elastic modulus compared to
other biomedical metals. However, the use of pure magnesium is hindered by its
relatively poor corrosion resistance which causes the mechanical properties of the
implant to significantly decrease resulting in the tissues being unable to heal.
Furthermore, Mg corrosion process involves evolution of hydrogen gas which
accumulates in vivo adjacent to the implant. The H2 gas and subsequent formation of
hydrogen bubbles can noticeably impair other clinical applications of Mg.
Alkalization of the surroundings by the H2 gas evolution during the corrosion process
of Mg is another drawback. Thus, it is essential to increase the corrosion resistance
of Mg and its alloys to meet the requirements of the synchronization between implant
biodegradation and the new bone formation.
1.3 Purpose of the Study
The purpose of this study addresses the problem described above, namely to
develop a new biodegradable magnesium alloy with adequate degradation rate for
use as an implant material. To investigate the potential of fluoride treatment for the
corrosion protection of magnesium alloys. The influence of parameters such as HF
concentration, duration and coating performance will be investigated. To determine
the developed process for synthesis a novel bi-layered coating composed of nano-HA
and brushite as top layer and MgF2 as interlayer that will demonstrate enhancement
of corrosion resistance of magnesium alloy. The optimal coating conditions for
deposition of nano-hydroxyapatite and brushite on fluoride treated magnesium alloy
will be determined.
1.4 Objectives of the Research
The principal objective of the research is increasing corrosion resistance of
magnesium alloys by alloying accompanied with surface treatment and nano-
hydroxyaptite coating by electrodeposition (ED) method on Mg-Ca and Mg-Ca-Zn
alloys. The specific objectives include:
1. To investigate the effects of calcium and zinc additions on the microstructure,
degradation rate and corrosion properties as well as solidification behavior
using thermal analysis of magnesium alloys.
2. To determine the effect of surface modification by hydrofluoric acid (HF) on
microstructure, in-vitro degradation behavior and corrosion properties of Mg-
Ca and Mg-Ca-Zn alloys.
3. To determine the effect of nano-HA/MgF2 and DCPD/MgF2 composite coating
on microstructure and corrosion behavior of Mg-Ca-Zn alloys.
1.5 Significance of the Research
In recent years, the study of magnesium alloys as degradable biomaterials has
become one of the most revolutionary research topics at the forefront of biomaterials
research. However, its application has been limited due to the relatively poor
corrosion resistance. Hence, it is expected that the outcome of the research will
eliminate the need of secondary surgery for current implant materials eliminated.
Using magnesium alloys as biodegradable implants resulted in reducing time, cost,
risk and morbidity of the patients.
1.6 Scope of the Research
The research was conducted in the following limits:
1- Calcium and zinc additions to Mg were limited to between (0.5 and 10 wt.%)
and (0.5 and 9 wt%) respectively.
2- The responses on the effect of calcium and zinc additions were limited to the
microstructure, degradation rate, corrosion properties and solidification
behavior of Mg-xCa and Mg-Ca-xZn alloys.
3- Hydrofluoric acid with concentrations between 35 and 40% as well as
immersion duration of 6 to 24 hours was used for surface treatment of Mg-Ca
and Mg-Ca-Zn alloys.
4- The current density used in electrodeposition of nano-HA and brushite
coatings on magnesium alloys was regulated between 0.15 to 0.8 mA/cm2 for
durations of 10 to 60 min.
5- The specimens were subjected to microstructural characterization using
optical microscopy, X-ray diffraction, atomic-force microscopy, Fourier-
transformed infrared spectroscopy, scanning electron microscopy and energy
dispersive X-ray spectroscopy and transmission electron microscopy.
6- The corrosion resistance was examined in vitro by potentiodynamic
polarization test, immersion test and hydrogen evolution test in Kokubo
solution at room temperature.
7- Solidification behavior of Mg-Ca and Mg-Ca-Zn alloys were examined via
two thermocouple thermal analysis method.
REFERENCES
1. Niinomi M., Recent Metallic Materials for Biomedical Applications.
Metallurgical and Materials Transaction A, 2002. 33: 477.
2. Jacobs J.J., Hallab N.J., and Skipor A.K., Metal degradation products: a cause
for concern in metal-metal bearings? Clin Orthop Relat Res, 2003. 417: 139
47.
3. Staigera P.M., Pietaka M.A., and Huadmai J., Magnesium and its alloys as
orthopedic biomaterials: A review. Biomaterials, 2006. 27: 1728-1734.
4. Chiu K.Y., Wong M.H., Cheng F.T., and Man H.C., Characterization and
corrosion studies of fluoride conversion coating on degradable Mg implants.
Surface & Coatings Technology , 2007. 202: 590-598.
5. Song G., Control of biodegradation of biocompatable magnesium alloys.
Corrosion Science, 2007. 49: 1696-1701.
6. Song G.L. and Song S.Z., A possible biodegradable magnesium implant
material. Advanced Engineering Materials, 2007. 94: 298-302.
7. Witte F., Feyerabend F., and Maier P., Biodegradable magnesium-
hydroxyapatite metal matrix composites. Biomaterials, 2007. 28: 2163-2174.
8. Xu L., Pan F., and Yu G., In vitro and in vivo evaluation of the surface
bioactivity of a calcium phosphate coated magnesium alloy. Biomaterials,
2009. 30:1512-1523.
9. Witte F., Fischer J., and Nellesen J., In vivo corrosion and corrosion
protection of magnesium alloy LAE442. Acta Biomaterialia, 2010. 6: 1792
1799.
10. Li N., Zheng Y., Novel Magnesium Alloys Developed for Biomedical
Application: A Review., J. Mater. Sci. Technol., 2013, 1-14.
11. Zhanga E. and Yang L., Microstructure, mechanical properties and bio
corrosion properties of M g-Zn-M n-Ca alloy for biomedical application.
Materials Science and Engineering A, 2008. 497: 111-118.
12. Li Z., Gu X., Lou S., and Zheng Y., The development of binary Mg-Ca alloys
for use as biodegradable materials within bone. Biomaterials, 2008. 29: 1329
1344.
13. Oh-ishi K, Watanabeb R., Mendisa C.L, Hono K, Age-hardening response of
Mg-0.3 at.%Ca alloys with different Zn contents. Materials Science and
Engineering A, 2009. 526: 177-184.
14. Tong L. B., Zheng M.Y., Cheng L. R., Kamado S., Zhang H. J. Effect of
extrusion ratio on microstructure, texture and mechanical properties of
indirectly extruded M g-Zn-Ca alloy. Materials Science and Engineering: A,
569, 2013:48-53.
15. Zhang E., Yang L., Xu J., and Chen H., Microstructure, mechanical
properties and biocorrosion properties of M g-Si(-Ca, Zn) alloy for
biomedical application. J Acta Biomater, 2010. 6: 1756-1762.
16. Levi G., Avraham S., Zilberov A., and Bamberger M., Solidification, solution
treatment and age hardening of a M g-1.6 wt.% Ca-3.2 wt.% Zn alloy. Acta
Materialia, 2006. 54: 523-530.
17. Du H., Wei Z., Liu X., and Zhang E., Effects of Zn on the microstructure,
mechanical property and bio-corrosion property of Mg-3Ca alloys for
biomedical application. Materials Chemistry and Physics, 2011 125: 568
575.
18. Zhou T., Chen D., and Chen Z. h., Microstructures and properties of rapidly
solidified Mg-Zn-Ca alloys. Transactions o f Nonferrous Metals Society o f
China, 2008. 18: 101-106.
19. Du H., Wei Z., Liu X., and Zhang E., Effects of Zn on the microstructure,
mechanical property and bio-corrosion property of Mg-3Ca alloys for
biomedical application. Materials Chemistry and Physics, 2011 125: p. 568
575.
20. Conceicao T.F.D., Scharnagl N., Blawert C., Dietzel W., and Kainer K.U.,
Surface modification of magnesium alloy AZ31 by hydrofluoric acid
treatment and its effect on the corrosion behaviour. Thin Solid Films, 2010.
518: 5209-5218.
21. Gu X.N., Zheng W., Cheng Y., and Zheng Y.F., A study on alkaline heat
treated M g-Ca alloy for the control of the biocorrosion rate. Acta
Biomaterialia, 2009. 5: 2790-2799.
22. Li W., Li.Y., Zhua L., and Zhao B., Growth characterization of anodic film
on AZ91D magnesium alloy in an electrolyte of Na2SiO3 and KF. Journal o f
University o f Science and Technology Beijing, 2006. 13: 450-455.
23. Zhou W., Shan D., Han E.H., and Ke W., Structure and formation mechanism
of phosphate conversion coating on die-cast AZ91D magnesium alloy.
Corrosion Science, 2008. 50: 329-337.
24. Chun-Yan Z., Rong-Chang Z., Cheng-Long L., and Jia-Cheng Gao.,
Comparison o f calcium phosphate coatings on M g-Al and M g-Ca alloys and
their corrosion behavior in Hank's solution. Surface & Coatings Technology,
2010 204: p. 3636-3640.
25. Wan Y., Xiong G., and Luo H., Preparation and characterization of a new
biomedical magnesium-calcium alloy. Materials & Design, 2008. 29: 2034
2037.
26. Lorenz C., Brunner G.J, and Kollmannsberger P., Effect of surface pre
treatments on biocompatibility of magnesium. Acta Biomaterialia, 2009. 5:
2783-2789.
27. Kim W.C., Kim J.G., and Lee J.Y., Influence of Ca on the corrosion
properties of magnesium for biomaterials. Materials Letters, 2008. 62: 4146
4148.
28. Hermawan H., Dube D, Mantovani D., Developments in metallic
biodegradable stents. Acta Biomaterialia, 2010. 6: 1693-1697.
29. Zheng Y.F., Gu X.N., Xi Y.L., and Chai D.L., In vitro degradation and
cytotoxicity of Mg/Ca composites produced by powder metallurgy. Acta
Biomaterialia, 2010. 6: 1783-1791.
30. Harandi S.E., Idris M.H., and Jafari H., Effect of forging process on
microstructure, mechanical and corrosion properties of biodegradable Mg-
1Ca alloy. Materials & Design, 2011. 32: 2596-2603.
31. Peter B. and Maurus M.D., Bioabsorbable Implant Material Review.
Operative Techniques in Sports Medicine, 2004. 12(3): 158-160.
32. Gu X.N. and Zheng Y.F., A review on magnesium alloys as biodegradable
materials. Front. Mater. Sci. China, 2010. 4(2): 111-115.
33. Guo K.W., A Review of Magnesium/Magnesium Alloys Corrosion and its
Protection. Recent Patents on Corrosion Science, 2010. 2: 13-21.
34. Manivasagam G., Dhinasekaran D., and Rajamanickam A., Biomedical
Implants: Corrosion and its Prevention - A Review. Recent Patents on
Corrosion Science, 2010. 2: 40-54.
35. Witte F. and Hort N., Degradable Biomaterials Based on Magnesium
Corrosion. Current Opinion in Solid State and Materials Science, 2008. 12:
63-72.
36. Eglin D. and Alini M., Degradable polymeric materials for osteosynthesis:
tutorial. European Cells and Materials, 2008. 16: 80-91.
37. Kammer C., Magnesium Taschenbuch. Dusseldorf: Aluminium-Verlag, 2000.
38. Witte F., The history of biodegradable magnesium implants: A review. Acta
Biomaterialia, 2010. 6: 1680-1692.
39. Edgar R.L., Global overview on demand and applications for magnesium
alloys. Proceedings of the international congress on “Magnesium alloys and
their applications” . Munchen, Weinheim: WILEY-VCH-Verlag GmbH 2000:
3-8.
40. Witte F., Eliezer A., and Cohen S., The history, challenges and the future of
biodegradable metal implants. Advanced Materials Research, 2010. 95: 3-7.
41. Mueller W.D. and Lucia Nascimento M., Critical discussion of the results
from different corrosion studies of Mg and Mg alloys for biomaterial
applications. Acta Biomaterialia, 2010. 6: 1749-1755.
42. Jayaraj J., Mendis C. L., and Ohkubo T., Enhanced precipitation hardening of
M g-Ca alloy by Al addition. Scripta Materialia, 2010. 63: 831-834.
43. Cai S., Lei T., and Li N., Effects of Zn on microstructure, mechanical
properties and corrosion behavior of M g-Zn alloys. Materials Science and
Engineering C, 2012. 32: 2570-2577.
44. Witte F., Kaese V., and Haferkamp H., In vivo corrosion of four magnesium
alloys and the associated bone response. Biomaterials, 2005. 26: 3557-3563.
45. Xu L.P., Yu G.N., Zhang E.L., Pan F., and Yang K., In vivo corrosion
behavior of Mg-Mn-Zn alloy for bone implant application. J Biomed Mater
Res, 2007. 83A(3): 703-11.
46. Li Q.F., Weng H. R., and Suo Z.Y., Microstructure and mechanical properties
of bulk Mg-Zn-Ca amorphous alloys and amorphous matrix composites.
Materials Science and Engineering A , 2008. 487: 301-308.
47. Wu G., Ibrahim J.M., and Chu P.K., Surface design of biodegradable
magnesium alloys - A review. Surface & Coatings Technology, 2012.
doi.org/10.1016/j.surfcoat.2012.10.009.
48. Xin Y., Hub T., and Chu P. K., In vitro studies of biomedical magnesium
alloys in a simulated physiological environment: A review. Acta
Biomaterialia, 2011 7: 1452-1459.
49. Gu X., Zheng Y., and Cheng Y., In vitro corrosion and biocompatibility of
binary magnesium alloys. Biomaterials, 2009. 30: 484-498.
50. Kutz M., Standard Handbook of Biomedical Engineering and Design.
McGraw-Hill Professional Publishing, 2002.
51. Aghion E. and Levyb G., The effect of Ca on the in vitro corrosion
performance of biodegradable Mg-Nd-Y-Zr alloy. J Mater Sci: Mater Med,
2010. 45: 3096-3101.
52. Zhang E., Yang L., Xu J., and Chen H., Microstructure, mechanical
properties and bio-corrosion properties of M g-Si(-Ca, Zn) alloy for
biomedical application. Acta Biomaterialia, 2010. 6: 1756-1762.
53. Sudholz A.D., Gusieva K., Chen X.B., Electrochemical behaviour and
corrosion of Mg-Y alloys. Corrosion Science, 2011. 53: 2277-2282.
54. Wasiur-Rahman S and Medraj M., Critical assessment and thermodynamic
modeling of the binary Mg-Zn, Ca-Zn and ternary M g-Ca-Zn systems.
Intermetallics, 2009. 17: 847-864.
55. Nayeb-Hashemi A.A. and Clark J.B., Phase diagrams of binary magnesium
alloy. ASM International, 1988.
56. Aljarrah M. and Medraj M, Thermodynamic modelling of the Mg-Ca, M g-
Sr, Ca-Sr and M g-Ca-Sr systems using the modified quasichemical model.
Computer Coupling o f Phase Diagrams and Thermochemistry, 2008. 32:
240-251.
57. Zhang S., Zhang X., and Zhao C., Research on an M g-Zn alloy as a
degradable biomaterial. Acta Biomaterialia, 2010. 6: 626-640.
58. Song Y., Hana E.H., Shan D., Yimb C. D., and Youb B. S., The effect of Zn
concentration on the corrosion behavior of Mg-xZn alloys. Corrosion
Science, 2012. 65: 322-330.
59. Xu Z., Smith C., and Chen S., Development and microstructural
characterizations of Mg-Zn-Ca alloys for biomedical applications. Materials
Science and Engineering B, 2011 176(20): 1660-1665.
60. Nayeb-Hashemi A.A. and Clark J.B., Phase diagram of binary magnesium
alloys, ASM International. Materials Park, OH, 1988: 293-304.
61. Grube G., Alloys of magnesium with cadmium, zinc, bismuth and antimony.
Zeitschrift fu r Anorganische Chemie, 1906. 49: 72-92.
62. Takei T., The equilibrium diagram of the system magnesium-zinc. Kinzoku-
no Kenkyu, Japan Institute o f Metals, 1929. 6: 177-183.
63. Clark J.B., The solid constitution in the Mg-rich region of the Mg-Ca-Zn
phase diagram. Transactions o f the Metallurgical Society o f AIME, 1961.
221: 644-645.
64. Rosalbino F., De Negri S., and Saccone A., Bio-corrosion characterization of
Mg-Zn-X (X 5 Ca, Mn, Si) alloys for biomedical applications. J Mater Sci:
Mater Med, 2010 21: 1091-1098.
65. Dong-song Y., Er-lin Z., and Song-yan Z., Effect of Zn on mechanical
property and corrosion property of extruded Mg-Zn-Mn alloy. Trans.
Nonferrous Met. Soc. China 2008. 18. 763-768
66. Zhang B., Hou Y., and Wang X., Mechanical properties, degradation
performance and cytotoxicity of M g-Zn-Ca biomedical alloys with different
compositions. Materials Science and Engineering C, 2011. 31: 1667-1673.
67. Geng L, Zhang B.P, Li A.B, Dong C.C, Microstructure and mechanical
properties of M g-4.0Zn-0.5Ca alloy. Materials Letters, 2009. 63: 557-559.
68. Oh-ishia K., Watanabeb R., and Mendisa C.L., Age-hardening response of
Mg-0.3 at.%Ca alloys with different Zn contents. Materials Science and
Engineering A, 2009. 526: 177-184.
69. Paris R., Publications Scientifiques et Techniques du minist’ere de L ’Air.
Ministe re de L ’Air, 1934. 45: 1-86.
70. Levi G, Zilberov A.S, and Bamberger A.M, Solidification, solution treatment
and age hardening of a M g-1.6 wt.% Ca-3.2 wt.% Zn alloy. Acta Materialia,
2006. 54: 523-530.
71. Malekan M,. and Shabestari S.G, Effect of grain refinement on the dendrite
coherency point during solidification of the A319 aluminium alloy.
Metallurgical and Materials Transactions, 2009. 40A: 3196-3203.
72. Zhou T., Chen D., Chen Z.H., and Chen J.H., Investigation on
microstructures and properties of rapidly solidified Mg-6wt.% Zn-5 wt.%
Ca-3 wt.% Ce alloy. Journal o f Alloys and Compounds, 2009. 475: L1-L4.
73. Dobrzanski L.A., Krol M, Tanski T., Maniara R., Thermal analysis of the
MCMgAl9Zn1 magnesium alloy. Archives o f Materials Science and
Engineering, 2008. 34: 113-116.
74. Emadi D, Whiting L.V, Nafisi S, and Ghomashchi R, Application of thermal
analysis in quality control of solidification process. Journal o f Thermal
Analysis and Calorimetry, 2005. 81: 235-242.
75. Liang S. M, Chen R.S, Blandin J.J, Suery M, and Han E.H, Thermal analysis
and solidification pathways of Mg-Al-Ca system alloys. Materials Science
and Engineering A, 2008. 480: 365-372.
76. Riddle Y.W. and Makhlouf M.M, Characterizing solidification by non
equilibrium thermal analysis. Magnesium Technology, The Minerals, Metals
& Materials Society, San Diego, 2003: 101-106.
77. Apelian D, Sigworth G.K, and Whaler K.R, Assessment of grain refinement
and modification of Al-Si foundry alloys by thermal analysis. AFS
Transactions, 1984. 92: 297-307.
78. Mahfoud M, Emadi D, and Prasada Rao A. K, The role of thermal analysis in
detecting impurity levels during aluminum recycling. Journal o f Thermal
Analysis and Calorimetry, 2010. 100: 847-851.
79. Lu L., and Dahle A. K, Effects of combined additions of Sr and AlTiB grain
refiners in hypoeutectic Al-Si foundry alloys. Materials Science and
Engineering A, 2006. 435-436: 288-296.
80. Huang Z.H, Liang S.M, Chen R.S, and Han E.H, Solidification pathways and
constituent phase of Mg-Zn-Y-Zr alloys. Journal o f Alloys and Compounds,
2009. 468: 170-178.
81. Kainer K.U., Srinivasan P.B., Blawert C., and Dietzel W., Corrosion of
Magnesium and its alloys. Shreir’s Corrosion, 2010: 2011-2041.
82. Shi Z. and Atrens A., An innovative specimen configuration for the study of
Mg corrosion. Corrosion Science, 2011. 53: 226-246.
83. Zhang S., Li J., and Song Y., In vitro degradation, hemolysis and MC3T3-E1
cell adhesion of biodegradable M g-Zn alloy. Materials Science and
Engineering C, 2009. 29: 1907-1912.
84. Wang Y., Wei M., and Gao J., Corrosion process of pure magnesium in
simulated body fluid. Materials Letters, 2008. 62: 2181-2184.
85. Atrens A., Liu M., and Zainal A.N., Corrosion mechanism applicable to
biodegradable magnesium implants. Materials Science and Engineering B ,
2011. 176: 1609-1636.
86. Virtanen S, Biodegradable Mg and Mg alloys: Corrosion and
biocompatibility. Materials Science and Engineering B, 2011 176: 1600-1608
87. Kirkland N.T., Birbilis N., and Staiger M.P., Assessing the corrosion of
biodegradable magnesium implants: A critical review of current
methodologies and their limitations. Acta Biomaterialia, 2012. 8: 925-936.
88. Neil W.C, Forsyth M, and Howlett P.C, Corrosion of heat treated magnesium
alloy ZE41. Corrosion Science, 2011. 53: 3299-3308.
89. Hanzi A.C., Gerber I., and Schinhammer M., On the in vitro and in vivo
degradation performance and biological response of new biodegradable M g-
Y-Zn alloys. Acta Biomaterialia, 2010. 6: 1824-1833.
90. Erdmann N, Angrisani N, and Reifenrath J, Biomechanical testing and
degradation analysis of MgCa0.8 alloy screws: A comparative in vivo study
in rabbits. Acta Biomaterialia, 2011. 7: 1421-1428.
91. Matsubara H., Ichige Y., Fujita K., Nishiyama H., Hodouchi K., Effect of
impurity Fe on corrosion behavior of AM50 and AM60 magnesium alloys
Corrosion Science, 2013. 66: 203-210.
92. Kannan M.B. and Dietzel W., Pitting-induced hydrogen embrittlement of
magnesium-aluminium alloy. Materials and Design 2012. 42: 321-326.
93. Mudali U. K, Sridhar T. M, and Baldev. RAJ., Corrosion of bio implants,
Sadhana, 2003. 28: 601-637.
94. Coy A. E., Viejo F., Skeldon P., and Thompson G.E., Susceptibility of rare-
earth-magnesium alloys to micro-galvanic corrosion. Corrosion Science,
2010. 52: 3896-3906.
95. Yang L. and Zhang E.L., Biocorrosion behavior of magnesium alloy in
different simulated fluids for biomedical application. Mater Sci Eng C, 2009.
29: 1691-1696.
96. Kirkland N.T., Lespagnol J., Birbilis N., and Staiger M. P., A survey of bio
corrosion rates of magnesium alloys. Corrosion Science, 2010. 52: 287-291.
97. Zainal-Abidin N.I., Atrens A.D., Martin D., Corrosion of high purity Mg,
Mg2Zn0.2Mn, ZE41 and AZ91 in Hank’s solution at 37°C. Corrosion
Science, 2011. 53: 3542-3556.
98. Zhang M., Huang X., and Jiang X., Phytic acid conversion coating on M g-Li
alloy Lili Gao, Chunhong Zhang. Journal o f Alloys and Compounds, 2009.
485:789-793.
99. Gray J.E., and Luan B., Protective coatings on magnesium and its alloys-a
critical review. Journal o f Alloys and Compounds, 2002. 336: 88-113.
100. Elsentriecy H.H., Azumi K., and Konno H., Effect of surface pretreatment by
acid pickling on the density of stannate conversion coatings formed on AZ91
D magnesium alloy. Surface & Coatings Technology, 2007. 202: 532-537.
101. Nwaogu U.C, Blawert C, and Scharnagl N, Effects of organic acid pickling
on the corrosion resistance of magnesium alloy AZ31 sheet. Corrosion
Science, 2010. 52: 2143-2154.
102. Gray J.E. and Luan B., Protective coatings on magnesium and its alloys — a
critical review. Journal o f Alloys and Compounds, 2002. 336: 88-113.
103. Hornberger H., Virtanen S., and Boccaccini A. R., Biomedical coatings on
magnesium alloys - A review. Acta Biomaterialia, 2012. 8: 2442-2455.
104. Brunelli K., Dabala M., and Calliari I., Effect of HCl pre-treatment on
corrosion resistance of cerium-based conversion coatings on magnesium and
magnesium alloys. Corrosion Science, 2005. 47: 989-1000.
105. Yang L., Zhang M., and Li J., Stannate conversion coatings on
Mg-8Li alloy. Journal o f Alloys and Compounds, 2009. 471: 197-200.
106. Chiu L.H., Chen C.C., and Yang C.F., Improvement of corrosion properties
in an aluminum-sprayed AZ31 magnesium alloy by a post-hot pressing and
anodizing treatment. Surface & Coatings Technology, 2005. 191: 181-187.
107. Thomann M., Krause C., Angrisani N., Bormann D., and Hassel T., Influence
of a magnesium-fluoride coating of magnesium-based implants (MgCa0.8) on
degradation in a rabbit model. Journal o f Biomedical Materials Research
Part A, 2010. 93: 1609-1619.
108. Drynda A., Hassel T., Hoehn R., Perz A., Bach F.W., and Peuster M.,
Development and biocompatibility of a novel corrodible fluoride-coated
magnesium-calcium alloy with improved degradation kinetics and adequate
mechanical properties for ardiovascular applications. Journal o f Biomedical
Materials Research Part A, 2009: 763-775.
109. Chen Y., Song Y., and Zhang S., Effect of fluoride coating on in vitro
dynamic degradation of Mg-Zn alloy. Materials Letters, 2011. 65: 2568
2571.
110. Yan T., Tan L., and Xiong D, Fluoride treatment and in vitro corrosion
behavior of an AZ31B magnesium alloy. Materials Science and Engineering
C, 2010. 30: 740-748.
111. Shadanbaz S. and Dias G. J., Calcium phosphate coatings on magnesium
alloys fo r biomedical applications: A review. Acta Biomaterialia 2012. 8: p.
20-30.
112. Bose S. and Tarafde S., Calcium phosphate ceramic systems in growth factor
and drug delivery for bone tissue engineering: A review Acta Biomaterialia,
2012. 8: 1401-1421.
113. Dorozhkin S.V, Calcium Orthophosphates in Nature, Biology and Medicine.
Materials and Design, 2009. 2: 399-498.
114. Dorozhkin S. V., Calcium Orthophosphates as Bioceramics: State o f the Art
J. Funct. Biomater, 2010. 1: 22-107.
115. Yanovska A., Kuznetsov V., and Stanislavov A., A study of brushite
crystallization from calcium-phosphate solution in the presence of
magnesium under the action of a low magnetic field. Materials Science and
Engineering C, 2012. 32: 1883-1887.
116. Shi Y., Qi M., Chen Y, and Shi P, MAO-DCPD composite coating on Mg
alloy for degradable implant applications. Materials Letters, 2011. 65: 2201
2204.
117. Dorozhkin, S.V., Amorphous calcium (ortho) phosphates. Acta
Biomaterialia, 2010. 6: 4457-4475.
118. Jiao M. J. and Wang X.X., Electrolytic deposition of magnesium-substituted
hydroxyapatite crystals on titanium substrate. Materials Letters, 2009. 63:
2286-2289.
119. Javidi M., Javadpour S., and Bahrololoom M.E., Electrophoretic deposition
of natural hydroxyapatite on medical grade 316L stainless steel. Mater Sci
Eng C, 2008. 28: 1509-15.
120. Abdel-Aal E.A, Dietrich D, Steinhaeuser S, and Wielage B,
Electrocrystallization of nanocrystallite calcium phosphate coatings on
titanium substrate at different current densities. Surface & Coatings
Technology, 2008. 202: 5895-5900.
121. Ergun C., Webster T., and Bizios R., Hydroxylapatite with substituted
magnesium, zinc, cadmium, and yttrium. I. Structure and microstructure.
Journal o f Biomedical Materials Research, 2002. 59(2): 305-311.
122. Geng F., Tan L.L., and Jin X.X., The preparation, cytocompatibility, and in
vitro biodegradation study of pure b-TCP on magnesium. J Mater Sci: Mater
Med, 2009. 20: 1149-1157.
123. Jamesh M, Kumar S, and Sankara Narayanan T.S.N, Corrosion behavior of
commercially pure Mg and ZM21 Mg alloy in Ringer’s solution - Long term
evaluation by EIS. Corrosion Science, 2011. 53: 645-654.
124. Mostafa N.Y. and Brown P.W., Computer simulation of stoichiometric
hydroxyapatite: Structure and substitutions. Journal o f Physics and Chemistry
o f Solids, 2007. 68: 431-437.
125. Gu X.N., Zheng Y.F., and Lan Q.X., Surface modification of an Mg-1Ca
alloy to slow down its biocorrosion by chitosan. Biomed. Mater, 2009. 4: 1-4.
126. Gao J.H, Guan S.K, Chen J, Wang L. G, Zhu S.J, Hu J.H., and Ren Z.W,
Fabrication and characterization of rod-like nano-hydroxyapatite on MAO
coating supported on M g-Zn-Ca alloy. Applied Surface Science, 2011. 257:
2231-2237.
127. Zhang E.L., Zou C.M., and Zeng S.Y., Preparation and characterization of
siliconsubstituted hydroxyapatite coating by a biomimetic process on
titanium substrate. Surface & Coatings Technology, 2009. 203: 1075-80.
128. Boccaccini A.R., Keim S., Ma R., Li Y., and Zhitomirsky I., Electrophoretic
deposition of biomaterials. Journal o f The Royal Society Interface, 2010: 1
33.
129. Conceicao T.F.D., Scharnagl N., Blawert C., Dietzel W., and Kainer K.U.,
Surface modification of magnesium alloy AZ31 by hydrofluoric acid
treatment and its effect on the corrosion behaviour. Thin Solid Films, 2010.
518: 5209-5218.
130. Yang Y., Kim K. H., and Ong J. L., A review on calcium phosphate coatings
produced using a sputtering process an alternative to plasma spraying.
Biomaterials, 2005. 26: 327-337.
131. Cui F., Yang J., and Jiao Y., Calcium phosphate coating on magnesium alloy
for modification of degradation behavior. Front Mater Sci Chin, 2008. 2:
143-148.
132. Combes C. and Rey C, Amorphous calcium phosphates: Synthesis, properties
and uses in biomaterials. Acta Biomaterialia, 2010. 6: 3362-3378.
133. Fellah B.H. and Layrolle P., Sol-gel synthesis and characterization of
macroporous calcium phosphate bioceramics containing microporosity. Acta
Biomaterialia, 2009. 5: 735-742.
134. Yang Y.Z., Kim K.H., and Joo L.O., A review on calcium phosphate coatings
produced using a sputtering process - an alternative to plasma spraying.
Biomaterials, 2005. 26: 327-37.
135. Paital S.R. and Dahotre N.B., Calcium phosphate coatings for bio-implant
applications: Materials, performance factors, and methodologies. Materials
Science and Engineering R, 2009. 66: 1-70.
136. Song Y., Wang H.X., Guan S.K., and Wang X., In vitro degradation and
mechanical integrity of Mg-Zn-Ca alloy coated with Ca-deficient
hydroxyapatite by the pulse electrodeposition process. Acta Biomaterialia,
2010. 6: 1743-1748.
137. Wei M., Ruys A.J., and Milthorpe B.K., Electrophoretic Deposition of
Hydroxyapatite Coatings on Metal Substrates: A Nanoparticulate Dual
Coating Approach. Journal o f Sol-Gel Science and Technology, 2001 21: 39
48.
138. Narayanan V. and Driessche I.V., Aqueous chemical solution deposition of
lanthanum zirconate and related lattice- matched single buffer layers suitable
for YBCO coated conductors: A review Progress in Solid State Chemistry,
2012. 40: 57-77.
139. Wen C, Guan S., Peng L., Ren C., Wang X., and Hu Z., Characterization and
degradation behavior of AZ31 alloy surface modified by bone-like
hydroxyapatite for implant applications. Applied Surface Science, 2009. 225:
6433-6438.
140. Meng E.C., Guan S.K., Wang H.X., and Wang L.G., Effect of
electrodeposition modes on surface characteristics and corrosion properties of
fluorine-doped hydroxyapatite coatings on Mg-Zn-Ca alloy. Applied Surface
Science, 2011. 257: 4811-4816.
141. Song Y.W., Shan D.Y., and Han E.H., Electrodeposition of hydroxyapatite
coating on AZ91D magnesium alloy for biomaterial application. Materials
Letters, 2008 62: 3276-3279.
142. Wanga H., Guana S, and Wang Y, In vivo degradation behavior of Ca-
deficient hydroxyapatite coated M g-Zn-Ca alloy for bone implant
application. Colloids and Surfaces B: Biointerfaces, 2011. 88: 254-259.
143. ASTM G31-72., Standard practice for laboratory immersion corrosion testing
of 369 metals. 2004.
144. Kirkland N.T., Birbilis N., and Walker J., In-vitro dissolution of magnesium-
calcium binary alloys: Clarifying the unique role of calcium additions in
bioresorbable magnesium implant alloys. Journal o f Biomedical Materials
Research Part B: Applied Biomaterials, 2010. 95B: 91-100.
145. Alloy phase diagram. In: ASM handbook, V.A.I., The Materials Information
Company; 1992.
146. Arnberg L., Chai G. , and Backerud L., Determination of dendritic coherency
in solidifying melts by rheological measurements. Materials Science and
Engineering, 1993. 173 A: 101-103.
147. Liang S.M. , Chen R.S., Blandin J.J., Suery M. , and Han E.H. , Thermal
analysis and solidification pathways of M g-A l-C a system alloys. Materials
Science and Engineering, 2008. 480A: 365-372.
148. Chai G., Backerud L., Rolland T., and Arnberg L., Dendrite Coherency
during Equiaxed Solidification in Binary Aluminum Alloys. Metallurgical
and Materials Transactions A, 1995. 26A: 965-970.
149. ASM International, ASM handbook:Alloy Phase Diagrams, ed. B. Hugh. 3.
1992, Ohio: ASM International.
150. Kirkland N.T, Lespagnol J., Birbilis N., and Staiger M.P, A survey of bio
corrosion rates of magnesium alloys. Corrosion Science, 2010. 52: 287-291.
151. Mao L, Yuan G, Niu J, Zong Y, and Ding W, In vitro degradation behavior
and biocompatibility of M g-N d-Zn-Zr alloy by hydrofluoric acid treatment.
Materials Science and Engineering: C, 2013. 33: 242-250.
152. Xin F., Jian C., Jian-peng Z., Wan Q., Zhou Z.C., Ruan J.N., Bone-like
apatite formation on HA/316L stainless steel composite surface in simulated
body fluid. Trans Nonferrous M et Soc China, 2009. 19: 347-52.
153. Fahamin A, Tabrizi B, and Ebrahimi-Kahrizsangi R, Synthesis of
calciumphosphate-based composite nanopowders by mechanochemical
process and subsequent thermal treatment. Ceramics International, 2012. 38:
6729-6738.
154. Zhang E., Yin D., Xu L., Lei Y., and Yang K., Microstructure, mechanical
and corrosion properties and biocompatibility of M g-Zn-M n alloys for
biomedical application. Mater Sci Eng C, 2009. 29: 987-993.
155. Lu L., Dahle A.K., Taylor J.A., and Stjohn D.H., Theoretical and Practical
Considerations of Grain Refinement of Mg-Al Alloys. Materials Science
Forum , 2005. 488-489: 299-302.
156. Bamberger M., Levi G., and Sande J.B., Precipitation Hardening in Mg-Ca-
Zn Alloys. Metallurgical and Materials Transactions A, 2006. 37: 481-488.
157. Shao G., Varsani V., and Fan Z., Thermodynamic modelling of the Y-Zn and
Mg-Zn-Y systems. Computer Coupling o f Phase Diagrams and
Thermochemistry, 2006. 30: 286-295.
158. Kumar G., Hegde S., and Narayan Prabhu K., Heat transfer and solidification
behaviour of modified A357 alloy. Journal o f Materials Processing
Technology, 2007. 182: 152-156.
159. Malekan M. and Shabestari S. G., Effect of grain refinement on the dendrite
coherency point during solidification of the A319 aluminium alloy.
Metallurgical and Materials Transactions A, 2009. 40 A(13): 3196-3203.
160. Argade G.R, Kandasamy K.S, Panigrahi K, and Mishra R. S, Corrosion
behavior of a friction stir processed rare-earth added magnesium alloy.
Corrosion Science, 2012. 58: 321-326.
161. Shi Z., Liu M., and Atrens A., Measurement of the corrosion rate of
magnesium alloys using Tafel extrapolation. Corros. Sci., 2010. 52: 579-588.
162. Lei T., Tang W., and Cai S.H., On the corrosion behaviour of newly
developed biodegradable Mg-based metal matrix composites produced by in
situ reaction. Corrosion Science, 2012. 54: 270-277.
163. Jamesh M, Kumar S, and Sankara Narayanan T.S.N, Corrosion behavior of
commercially pure Mg and ZM21 Mg alloy in Ringer’s solution - Long term
evaluation by EIS. Corrosion Science, 2011. 53: 645-654.
164. Vojte'ch D., Kubasek J., Serak J., and Novak P., Mechanical and corrosion
properties of newly developed biodegradable Zn-based alloys for bone
fixation. Acta Biomaterialia, 2011. 7: 3515-3522.
165. Wang H., Estrin Y., and Zuberovac. Z., Bio-corrosion of a magnesium alloy
with different processing histories. Mater Lett, 2008. 62: 2476-2479.
166. Verdierc S., Laaka N.V.D., and Delalandea S., The surface reactivity of a
magnesium-aluminium alloy in acidic fluoride solutions studied by
electrochemical techniques and XPS. Applied Surface Science, 2004. 253:
513-524.
167. Vasilescu C., Drob P, Vasilescu E, and Ionitab D., Prodanab M., Drob S.I,
Characterisation and corrosion resistance of the electrodeposited
hydroxyapatite and bovine serum albumin/hydroxyapatite films on T i-6A l-
4V-1Zr alloy surface. Corrosion Science, 2011. 53: 992-999.
168. Budke E., Krempel-Hesse J., Maidhof H., and Schu" ssler H., Decorative
hard coatings with improved corrosion resistance. Surf Coat Technol, 1999.
112:108-113.
169. Gu X.N., Li N., Zhou W. R., Zheng Y.F., and Zhao X., Corrosion resistance
and surface biocompatibility of a microarc oxidation coating on a M g-Ca
alloy. Acta Biomaterialia, 2011. 7: 1880-1889.
170. Pereda M.D., Alonso C, and Gamero M, Comparative study of fluoride
conversion coatings formed on biodegradable powder metallurgy Mg: The
effect of chlorides at physiological level. Materials Science and Engineering,
C 2011. 31: 858-865.
171. Wang Y., Zhang S., and Zeng X., Osteoblastic cell response on fluoridated
hydroxyapatite coatings. Acta Biomaterialia, 2007. 3: 191-197.
172. Koleini Sh., Idris M.H., and Jafari H., Influence of hot rolling parameters on
microstructure and biodegradability of M g-1Ca alloy in simulated body fluid.
Materials and Design, 2012. 33: 20-25.
173. Chen Y., Song Y, and Zhang S, Effect of fluoride coating on in vitro dynamic
degradation of Mg-Zn alloy. Materials Letters, 2011. 65: 2568-2571.
174. Djosic M.S, Panic.V., Stojanovi J.C., Mitric M., and Mi'skovic-Stankovic
V.B, The effect of applied current density on the surface morphology of
deposited calcium phosphate coatings on titanium. Colloids and Surfaces A:
Physicochem. Eng. Aspects, 2012. 400: 36-43.
175. Wang S.H, Shihb W. J., Li W.L, Hon M.H, Wang M.C., Morphology of
calcium phosphate coatings deposited on a Ti-6Al-4V substrate by an
electrolytic method under 80 Torr. Journal o f the European Ceramic Society,
2005. 25: 3287-3292.
176. Wang M.C, Shihb W.J, Chang K.M, Wang S.H., Li W. L., Huang H.H.,
Effect of process parameters on the crystallization and morphology of
calcium phosphate at a constant pressure of 80 Torr. Journal o f Non
Crystalline Solids, 2010. 356: 1546-1553.
177. Eliaz, N. and Sridhar T.M., Electrocrystallization of Hydroxyapatite and Its
Dependence on Solution Conditions. Crystal Growth & Design, 2008. 8:
3965-3977.
178. Zhitomirsky I., Electrophoretic hydroxyapatite coatings and fibers. Materials
Letters, 2000. 42: 262-271.
179. Bose S, Dasgupta S, Tarafder S, and Bandyopadhyay A, Microwave-
processed nanocrystalline hydroxyapatite: Simultaneous enhancement of
mechanical and biological properties. Acta Biomaterialia, 2010. 6: 3782
3790.
180. Lu Y.P, Chen Y. M, Li S.T, and Wang J.H, Surface nanocrystallization of
hydroxyapatite coating. Acta Biomaterialia, 2008. 4: 1865-1872.
181. Wen C, Guan S, Peng L, Ren C, Wang X, and Hu Z, Characterization and
degradation behavior of AZ31 alloy surface modified by bone-like
hydroxyapatite for implant applications. Applied Surface Science, 2009. 255:
6433-6438.
182. Zhang J.M., Lin C.J., Feng Z.D., and Tian Z.W., Mechanistic studies of
electrodeposition for bioceramic coatings of calcium phosphates by an in situ
pH-microsensor technique. Journal o f Electroanalytical Chemistry, 1998.
452 235-240.
183. Dumelie N., Benhayoune H., Rousse-Bertrand C., Bouthors S., and Perchet
A., Characterization of electrodeposited calcium phosphate coatings by
complementary scanning electron microscopy and scanning-transmission
electron microscopy associated to X-ray microanalysis. Thin Solid Films,
2005. 492: 13 -139.
184. Yen S.K. and Lin C.M., Cathodic reactions of electrolytic hydroxyapatite
coating on pure titanium. Materials Chemistry and Physics, 2002. 77: 70-76.
185. Rossler S., Sewing A., Stolzel M., Born R., Electrochemically assisted
deposition of thin calcium phosphate coatings at near-physiological pH and
temperature. JBiom ed Mater Res A, 2003. 64: 655-663.
186. Xu J., Butler I.S., and Gilson D.F.R., FT-Raman and high-pressure infrared
spectroscopic studies of dicalcium phosphate dihydrate (CaHPO4 2H2O) and
anhydrous dicalcium phosphate (CaHPO4). Spectrochimica Acta Part A,
1999. 55: 2801-2809.
187. Park J. H., Lee D. Y., Oh K. T., and Lee Y. K., Bioactivity of calcium
phosphate coatings prepared by electrodeposition in a modified simulated
body fluid. Materials Letters, 2006. 60: 2573-2577.
188. Fahami A., Ebrahimi-Kahrizsangi R., and Nasiri-Tabrizi B.,
Mechanochemical synthesis of hydroxyapatite/titanium nanocomposite. Solid
State Sciences, 2011. 13: 135-141.
189. Fathi M. H. and Zahrani E. M., Mechanical alloying synthesis and bioactivity
evaluation of nanocrystalline fluoridated hydroxyapatite. Journal o f Crystal
Growth, 2009. 311: 1392-1403.
190. Yang J. X., Cui F. Z., Lee I. S., Jiao Y. P., Yin Q. S., and Zhang Y., Ion-beam
assisted deposited C-N coating on magnesium alloys. Surface & Coatings
Technology, 2008. 202: 5737-5741.
191. Fathi M. H., Zahrani E. M., and Zomorodian A., Novel fluorapatite/niobium
composite coating for metallic human body implants. Materials Letters,
2009. 63: 1195-1198.
192. Yan T, Tan L., and Xiong D, Fluoride treatment and in vitro corrosion
behavior of an AZ31B magnesium alloy. Materials Science and Engineering
C, 2010. 30: 740-748.
