Research Article Preparation and Characterization of Hydroxyapatite...

Hindawi Publishing CorporationBioinorganic Chemistry and ApplicationsVolume 2013 Article ID 175756 6 pageshttpdxdoiorg1011552013175756

Research ArticlePreparation and Characterization of Hydroxyapatite Coating onAZ31 Mg Alloy for Implant Applications

S A Salman12 K Kuroda1 and M Okido1

1 EcoTopia Science Institute Nagoya University Furo-cho Chikusa Nagoya 464-8603 Japan2Graduate School of Engineering Al-Azhar University Nasr City Cairo 11371 Egypt

Correspondence should be addressed to S A Salman sasalmanyahoocom

Received 2 November 2012 Revised 19 January 2013 Accepted 21 January 2013

Academic Editor Giovanni Natile

Copyright copy 2013 S A Salman et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Magnesium alloys as biodegradable metal implants in orthopaedic research received a lot of interest in recent years They haveattractive biological properties including being essential to human metabolism biocompatibility and biodegradability Howevermagnesium can corrode too rapidly in the high-chloride environment of the physiological system loosing mechanical integritybefore the tissue has sufficiently healed Hydroxyapatite (HAp) coating was proposed to decrease the corrosion rate and improve thebioactivity of magnesium alloy Apatite has been cathodically deposited on the surface of Mg alloy from solution that composed of3mMCa(H

2PO4)2and 7mMCaCl

2at various applied potentialsThe growing of HApwas confirmed on the surface of the coatings

after immersion in SBF solution for 7 days The coating obtained at minus14 V showed higher corrosion resistance with bioactivebehaviors

1 Introduction

Metal materials including stainless steels titanium andcobalt-chromium-based alloys are commonly used forimplant devices due to their high strength ductility andgood anticorrosion properties [1] It is more suitable for load-bearing applications compared with ceramics or polymericmaterials due to their combination of high mechanicalstrength and fracture toughness [2] The release of toxicmetallic ions or particles by corrosion or wear processes leadsto undesirable effects on cell and bone tissues [3] Moreoverthese metallic materials are not biodegradable in the humanbody and can cause long-term complication (infection) [4]The elastic modules of current metallic biomaterials are notwell matched with that of natural bone tissue resulting instress shielding effects that can lead to reduced stimulation ofnew bone growth and remodeling which decreases implantstability [5] Comparing to commonly approvedmetallic bio-materials magnesium alloys have many outstanding advan-tages due to their attractive biological property includingbeing essential to human metabolism biocompatibility andbiodegradability [6]

The mechanical properties of magnesium alloys are sim-ilar to those of natural bone (40ndash57GPa) [7] Moreovermagnesium is one of the most important bivalent ionsassociated with the formation of biological appetites andplays an important role in the changes in the bonematrix thatdetermines bone fragility [8] On the other hand implantsmade of magnesium alloys were degraded in vivo eliminat-ing the need for a second operation for implant removalGood biocompatibility was observed in clinical studies [9]Unfortunately magnesium can corrode too rapidly in thephysiological pH (74ndash76) and high-chloride environment ofthe physiological system loosing mechanical integrity beforethe tissue has sufficiently healed and producing hydrogen gasin the corrosion process at a rate that is too fast to be dealtwith by the host tissue [10]

Recently some researches have been done to slow downthe biodegradation rate of magnesium alloys including flu-oride conversion coating [11] alkali-heat treatment [12] andplasma immersion ion implantation [13] Besides improvingthe biodegradation rate of magnesium alloys the biocom-patibility should also be considered The hydroxyapatite[Ca10(PO4)6(OH)2] hereafter (HAp) coating can satisfy

2 Bioinorganic Chemistry and Applications

Table 1 Chemical composition (mass) of AZ31 Mg alloy

Al Zn Mn Si Cu Ni Fe Mg30 10 043 001 lt001 lt0001 0003 Bal

minus14 V

minus18 V

minus16 V

0

minus05

minus1

minus15

0 500 1000 1500Time 119905 (s)

Curr

ent d

ensit

y119894

(mA

middotcmminus2)

Figure 1 Current change during cathodic electrodeposition onAZ31 Mg alloy in 3mM Ca(H

2PO4)2 7mM CaCl

2for 30min

the dual properties Synthetic HAp ceramics was routinelyused as porous implants powders and coatings on metallicprostheses to provide bioactive fixation The presence ofsparingly soluble HAp coatings led to bone tissue response(osteoconduction) in which bone grew along the coating andformed a mechanically strong interface [14] Therefore HApcoating was deposited on the surface of metallic implants toimprove the biocompatibility property and to decrease thedegradation rate in the physiological environment Depo-sition of HAp coatings has been achieved by a number ofmethods including plasma spraying [15] ion implantation[16] sputtering [17] sol-gel coating [18] biomimeticmethods[19] electrophoretic deposition (EPD) [20] electrochemicaldeposition [21] and electrospray deposition (ESD) [22 23]

Among these methods electrochemical deposition isknown to be simple flexible and inexpensive techniquefor fabricating the metallic thin films and does not requirecomplex and expensive vacuum apparatus In addition thedeposition processing can be conducted at room temper-ature and the morphology of coating can be controlledeasily by varying the electrochemical potential and electrolyteconcentration [24]

In this study electrodeposition method was employedto produce HAp coating on AZ31 magnesium alloy in orderto improve the anticorrosion properties and to enhance itsbioactivity The electrodeposition process was performedin calcium phosphate electrolyte with other additives atoptimized pH and temperature The effect of applied poten-tial on the structure and the anticorrosion properties wasinvestigated The anticorrosion properties of the developedcoatings were evaluated by the anodic polarization and elec-trochemical impedance spectroscopy techniquesThe surfacemorphology and phase structure of coated films were also

examined using scanning electron microscope (SEM) X-ray diffraction (XRD) and Energy Dispersive Spectroscopy(EDS) The HAp coating could enhance the anticorrosionproperty and effectively improved in vitro bioactivity insimulated body fluid

2 Materials and Methods

21 Specimens Preparation Commercially available AZ31Mgalloy (3 mass Al 1 mass Zn) was used as the substrateThe chemical composition of the alloy is listed in Table 1Thesurface of the alloys was polished up to no 2000 emery paperfollowed by 005 120583m alumina powders The specimens werecarefully cleaned with water rinsed with acetone and driedunder air All of the experiment specimens were mountedusing polytetrafluoroethylene (PTFE) resin tape leaving andexposed surface area of 1 cm2

22 The Film Formation The specimens were immersed in3mM Ca(H

2PO4)2+ 7mM CaCl

2solution at 37∘C and pH

6 for 30min The electrodeposition was performed at minus14minus16 and minus18 V applied potentials using a conventional elec-trochemical cell equipped with three electrodes PlatinumAgAgCl sat KCl and magnesium alloy specimen servedas the counter the reference and the working electroderespectively

23 Characterization Methods The morphology andmicrostructure of the films were observed with HitachiS-800 scanning electron microscope (SEM) The crystalstructure of the coated films was identified using thin film X-ray diffraction (XRD) analysis using a Shimadzu XRD-6000X-ray diffractometer with Cu K120572 radiation with scan step002∘ and scan speed 2∘min from diffraction angle of 10 to60 at 30 kV and 20mA The elemental composition of thecoating was identified using Energy Dispersive Spectroscopy(EDS)

24 Anticorrosion Measurements The anodic polarizationand electrochemical impedance spectroscopy tests were car-ried out using a Solartron 1285 Potentiostat from SolartronAnalytical Farnborough United Kingdom The measure-ments were controlled by Scribner Associates Corrware andZ polt electrochemical experiment software respectivelyThepolarization curves were measured in phosphate bufferedsaline PBS(minus) solutions with a scanning rate of 1mVs

25 Bioactivity Experiment in Simulated Body Fluid Thecoating was immersed for 7 days in the SBF (Kokubosolution) with ion concentrations nearly the same as thoseof the body blood plasma The pH of the SBF solution wasadjusted to 74 The phase structure surface morphologyand the anticorrosion property were examined every dayby removing the specimens from SBF solution rinsed withdistilled water and air-dried

Bioinorganic Chemistry and Applications 3

10120583m

1120583m

minus14 V minus18 Vminus16 V

Figure 2 SEM images of coating films formed on AZ31 Mg alloy in 3mMCa(H2PO4)2 7mM CaCl

2for 30min at minus14 V minus16 V and minus18 V

10

8

6

4

2

0minus13 minus12 minus11minus15minus16 minus14

Potential (119864119881 versus AgAgCl sat KCl)

minus14 V minus18 Vminus16 VNontreated

Curr

ent d

ensit

y119894

(mA

middotcmminus2)

Figure 3 Anodic polarization test in PBS(minus) for AZ31 magnesiumalloys before and after treatment at minus14 V minus16 V and minus18 V

3 Results and Discussion

High bioactivity can be achieved by performing the coating inthe condition that is near to the human internal environmentSome research groups have applied various ranges of temper-atures (room temperature 45 50 and 80∘C) and initial pH(58 65 and neutral) [25]

To achieve pure apatite coating on magnesium alloy theinitial pH and temperature should be carefully chosen In ourprevious work the optimum solution pH and temperaturewere defined [26] The HAp peaks could be observed only atthe temperature of 37∘C or higher It has been reported thatthe growth rate of apatite layer increased with the increasing

104

103

102

10000 2000 3000

Nontreated

Cor

rosio

n re

sista

nce119877

ct(W

middotcm2)

Immersion time 119905 (s)

minus14 V

minus18 V

minus16 V

Figure 4 Change in Rct in PBS(minus) for AZ31 magnesium alloysbefore and after treatment at minus14 V minus16 V and minus18 V

temperature due to the decreasing in the solubility product ofHAp [27]

HAp coating was deposited on the AZ31 alloy using theelectrodeposition method Fixed potential was set to minus14minus16 and minus18 V so that the Mg alloy substrate becamenegatively charged (as a cathode) Magnesium dissolutiontakes place immediately after immersion of the specimenin 3mM Ca(H

2PO4)2and 7mM CaCl

2solution for 30min

at pH 6 according to reaction (1) Water is reduced at thecathode surface to produce hydrogen gas and hydroxide ions


(a) (b)

1 120583m

(c)

Figure 5 SEM images of coating obtained at minus14 V before and after immersion in SBF solution for 1 day and 7 days

(a) (b)

10 20 30 40 50 60

MgMg(OH)2

HApDCPD

2120579 Cu K 120572

(c)

Figure 6 xrd patterns of coatings obtained at minus14 V before and after immersion in SBF solution for 1 day and 7 days

AlAl

(a)

Ca

PO

(b)

Mg

(c)

CaCl

0 1 2 3 4 5Binding energy (keV)

(d)

Figure 7 EDS patterns of coatings obtained at minus14 V before and after immersion in SBF solution for 1 day and 7 days


which will lead to an increase in the solution pH according toreaction (2)

Mg = Mg2+ + 2eminus (1)

2H2O + 2eminus = 2OHminus +H (2)

Figure 1 shows the current-time curves during the elec-trodeposition treatment at various potentials At minus18 Vthe current density sharply decreased indicating the earlyformation of the coating film On the other hand the currentdensity has a slight decrease at minus16 V and has nearly a stablerate at minus14The local increase in the pH value and availabilityof Ca and P ions in the solution are expected to encouragethe deposition of HAp and dicalcium phosphate dihydrate[CaHPO

4sdot2H2O] hereafter (DCPD) on themagnesium alloy

surface as shown in reactions (3) and (4)

5Ca2+ + 3PO4+OHminus 997888rarr 1

2

(Ca10(PO4)

6(OH)2)

(3)

Ca2+ +HPO4+ 2H2O 997888rarr CaHPO

4sdot 2H2O (4)

Figure 2 shows the SEM images of coating films formed atminus14 V minus16 V and minus18 V Flake-like particles were observedon all surfaces after cathodic deposition while the sizeof crystallites becomes finer with increasing the cathodicpotential to more negative side

The corrosion resistance of the coating films formed atminus14 minus16 and minus18 V was examined in PBS(minus) solution usinganodic polarization tests as shown in Figure 3 The resultsshow that the corrosion reaction does not take place easilyas it indicated by the decrease of corrosion currents and theincrease of polarization resistances The pitting potential ofall Hap-coated specimens shifted toward the noble directionin comparison to the nontreated specimenThis indicates thatthe coating films offered a corrosion protection andMg alloywas able to be prevented from being dissolved Moreover thecoating obtained at minus14 V has the nobler pitting potential

EIS test was performed to ensure the best corrosionresistance film Corrosion rate determination is associatedwith the charge transfer resistance (Rct) by using EIS tech-nique The charge transfer resistance is equal to the diameterof the semicircle in the complex plane graph (Nyquistdiagram) Figure 4 shows the time dependence of the chargetransfer resistance which corresponds to corrosion rate Thecharge transfer resistance increases by the treatment in 3mMCa(H2PO4)2and 7mM CaCl

2solution at various applied

potentials The film formed at minus14 V has much higher Rctvalue than those formed at minus18 and minus16 V This result isin agreement with anodic polarization test which indicatesthat the film formed at minus14 V has the best anticorrosionproperties

Improving corrosion resistance and decreasing disso-lution rate of implant materials are highly recommendedto allow the bone to heal Therefore we performed thebioactivity experiments on the coating obtained atminus14 VThein vitro examination was carried out at 37∘C for 7 days inorder to evaluate the bioactive behaviors of HAp coating inSBF solution which has the ion element equal to or close tothat of blood plasma

Figure 5 shows the surface morphologies of the coatingobtained at minus14 before and after immersion in SBF solutionfor 1 day and 7 days The growing of HAp was confirmed onthe surface of the coating after immersion for 1 day in SBFsolution The particles sizes were finer upon immersion inSBF solution The growing rate of HAp on the surface of thecoating is notably increased with increasing the immersiontime to 7 days

Figure 6 shows the XRD results of the coating obtainedat minus14 before and after immersion in SBF solution for 1 dayand 7 days The DCPD and HAp peaks were seen beforeimmersion in SBF solution

With immersion in SBF solution DCPD was convertedinto more stable HAp With increasing of immersion time to7 days HAp peaks have increased which confirms the growthof HAp

Figure 7 shows the EDS results of the coating obtainedat minus14 before and after immersion in SBF solution for 1day and 7 days Strong peaks of calcium (Ca) phosphorous(P) oxygen (O) magnesium (Mg) aluminum (Al) andseveral small peakswere observed before and after immersionin SBF solution Figure 6(a) shows that the coating filmcomposed of Mg Al and calcium phosphate compoundswhich are identified as HAp and DCPD from previous XRDtest With immersion in SBF solution for 1 day the peaksof Ca and P were increased and Mg peaks were decreasedwhich indicate growing ofHAp as shown in Figure 6(b)Withincreasing of immersion time to 7 days the peaks of Ca and Pcontinued to increase andMg peaks continued to decrease asshown in Figure 6(b) This continuous growing of HAp withimmersion for 7 days obviously confirms the bioactivity ofthis coating

4 Conclusions

The hydroxyapatite coating was successfully electrode-posited on magnesium alloy surface by immersing in 3mMCa(H2PO4)2and 7mM CaCl

2solution for 30min and at

temperature of 37∘C The anticorrosion property of AZ31magnesium alloy was improved with hydroxyapatite coatingand the best anticorrosion properties were obtained at minus14 VHydroxyapatite was grown on the coating with immersion inSBF solution for 7 days which proves its bioactivity

Acknowledgments

The authors gratefully acknowledge the Ministry of theEducation Culture Sports Science and Technology Japanand the Ministry of Higher Education Egypt They wish alsoto acknowledge Professor Ryoichi Ichino of EcoTopia ScienceInstitute Nagoya University Japan for valuable discussionduring this research

References

[1] S Ono A Kodama and H Asoh ldquoElectrodeposition behaviorof hydroxyapatite on porous electrode composed of sinteredtitanium spheresrdquo Journal of Japan Institute of Light Metals vol58 no 11 pp 593ndash598 2008


[2] M Sumita T Hanawa and S H Teoh ldquoDevelopment ofnitrogen-containing nickel-free austenitic stainless steels formetallic biomaterialsmdashreviewrdquoMaterials Science and Engineer-ing C vol 24 no 6ndash8 pp 753ndash760 2004

[3] B D Hahn D S Park J J Choi et al ldquoAerosol deposition ofhydroxyapatite-chitosan composite coatings on biodegradablemagnesium alloyrdquo Surface andCoatings Technology vol 205 no8-9 pp 3112ndash3118 2011

[4] C Lhotka T Szekeres I Steffan K Zhuber and K ZweymullerldquoFour-year study of cobalt and chromium blood levels inpatients managed with two different metal-on-metal total hipreplacementsrdquo Journal of Orthopaedic Research vol 21 no 2pp 189ndash195 2003

[5] J Nagels M Stokdijk and P M Rozing ldquoStress shielding andbone resorption in shoulder arthroplastyrdquo Journal of Shoulderand Elbow Surgery vol 12 no 1 pp 35ndash39 2003

[6] P Staiger A Pietak J Huadmai and G Dias ldquoMagnesium andits alloys as orthopedic biomaterials a reviewrdquoBiomaterials vol27 no 9 pp 1728ndash1734 2006

[7] J Vormann ldquoMagnesium nutrition and metabolismrdquo Molecu-lar Aspects of Medicine vol 24 no 1ndash3 pp 27ndash37 2003

[8] C R Howlett H Zreiqat R OrsquoDell et al ldquoThe effect ofmagnesium ion implantation into alumina upon the adhesionof human bone derived cellsrdquo Journal of Materials Science vol5 no 9-10 pp 715ndash722 1994

[9] F Witte V Kaese H Haferkamp et al ldquoIn vivo corrosionof four magnesium alloys and the associated bone responserdquoBiomaterials vol 26 no 17 pp 3557ndash3563 2005

[10] C EWenMMabuchi Y Yamada K Shimojima Y Chino andT Asahina ldquoProcessing of biocompatible porous Ti and MgrdquoScripta Materialia vol 45 no 10 pp 1147ndash1153 2001

[11] K Y Chiu M H Wong F T Cheng and H C ManldquoCharacterization and corrosion studies of fluoride conversioncoating on degradable Mg implantsrdquo Surface and CoatingsTechnology vol 202 no 3 pp 590ndash598 2007

[12] X N Gu W Zheng Y Cheng and Y F Zheng ldquoA studyon alkaline heat treated Mg-Ca alloy for the control of thebiocorrosion raterdquo Acta Biomaterialia vol 5 no 7 pp 2790ndash2799 2009

[13] C Liu Y Xin X Tian and P K Chu ldquoCorrosion behaviorof AZ91 magnesium alloy treated by plasma immersion ionimplantation and deposition in artificial physiological fluidsrdquoThin Solid Films vol 516 no 2ndash4 pp 422ndash427 2007

[14] L L Hench and J M Polak ldquoThird-generation biomedicalmaterialsrdquo Science vol 295 no 5557 pp 1014ndash1017 2002

[15] L Yan Y Leng and L T Weng ldquoCharacterization of chemicalinhomogeneity in plasma-sprayed hydroxyapatite coatingsrdquoBiomaterials vol 24 no 15 pp 2585ndash2592 2003

[16] M Hamdi and A Ide-Ektessabi ldquoPreparation of hydroxyapatitelayer by ion beam assisted simultaneous vapor depositionrdquoSurface and Coatings Technology vol 163-164 pp 362ndash3672003

[17] S J Ding ldquoProperties and immersion behavior of magnetron-sputtered multi-layered hydroxyapatitetitanium compositecoatingsrdquo Biomaterials vol 24 no 23 pp 4233ndash4238 2003

[18] W Weng S Zhang K Cheng et al ldquoSol-gel preparation ofbioactive apatite filmsrdquo Surface and Coatings Technology vol167 no 2-3 pp 292ndash296 2003

[19] W H Song Y K Jun Y Han and S H Hong ldquoBiomimeticapatite coatings on micro-arc oxidized titaniardquo Biomaterialsvol 25 no 17 pp 3341ndash3349 2004

[20] X Meng T Y Kwon and K H Kim ldquoHydroxyapatite coatingby electrophoretic deposition at dynamic voltagerdquoDentalMate-rials Journal vol 27 no 5 pp 666ndash671 2008

[21] R Chiesa E Sandrini M Santin G Rondelli and A CigadaldquoOsteointegration of titanium and its alloys by anodic sparkdeposition and other electrochemical techniques a reviewrdquoTheJournal of Applied Biomaterials amp Biomechanics vol 1 no 2 pp91ndash107 2003

[22] W Siefert ldquoCorona spray pyrolysis a new coating techniquewith an extremely enhanced deposition efficiencyrdquo Thin SolidFilms vol 120 no 4 pp 267ndash274 1984

[23] M Iafisco R Bosco S C G Leeuwenburgh et al ldquoElectrostaticspray deposition of biomimetic nanocrystalline apatite coatingsonto titaniumrdquo Advanced Engineering Materials vol 14 ppB13ndashB20 2012

[24] M C Kuo and S K Yen ldquoThe process of electrochemicaldeposited hydroxyapatite coatings on biomedical titanium atroom temperaturerdquoMaterials Science andEngineeringC vol 20no 1-2 pp 153ndash160 2002

[25] H Qu and M Wei ldquoThe effect of temperature and initial pHon biomimetic apatite coatingrdquo Journal of Biomedical Materialsvol 87 no 1 pp 204ndash212 2008

[26] S A Salman Corrosion protection of magnesium alloys withanodizing and conversion coating [PhD thesis] Nagoya Univer-sity 2010

[27] T Kokubo and H Takadama ldquoHow useful is SBF in predictingin vivo bone bioactivityrdquo Biomaterials vol 27 no 15 pp 2907ndash2915 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


Table 1 Chemical composition (mass) of AZ31 Mg alloy

Al Zn Mn Si Cu Ni Fe Mg30 10 043 001 lt001 lt0001 0003 Bal

minus14 V

minus18 V

minus16 V

0

minus05

minus1

minus15

0 500 1000 1500Time 119905 (s)

Curr

ent d

ensit

y119894

(mA

middotcmminus2)

Figure 1 Current change during cathodic electrodeposition onAZ31 Mg alloy in 3mM Ca(H

2PO4)2 7mM CaCl

2for 30min

the dual properties Synthetic HAp ceramics was routinelyused as porous implants powders and coatings on metallicprostheses to provide bioactive fixation The presence ofsparingly soluble HAp coatings led to bone tissue response(osteoconduction) in which bone grew along the coating andformed a mechanically strong interface [14] Therefore HApcoating was deposited on the surface of metallic implants toimprove the biocompatibility property and to decrease thedegradation rate in the physiological environment Depo-sition of HAp coatings has been achieved by a number ofmethods including plasma spraying [15] ion implantation[16] sputtering [17] sol-gel coating [18] biomimeticmethods[19] electrophoretic deposition (EPD) [20] electrochemicaldeposition [21] and electrospray deposition (ESD) [22 23]

Among these methods electrochemical deposition isknown to be simple flexible and inexpensive techniquefor fabricating the metallic thin films and does not requirecomplex and expensive vacuum apparatus In addition thedeposition processing can be conducted at room temper-ature and the morphology of coating can be controlledeasily by varying the electrochemical potential and electrolyteconcentration [24]

In this study electrodeposition method was employedto produce HAp coating on AZ31 magnesium alloy in orderto improve the anticorrosion properties and to enhance itsbioactivity The electrodeposition process was performedin calcium phosphate electrolyte with other additives atoptimized pH and temperature The effect of applied poten-tial on the structure and the anticorrosion properties wasinvestigated The anticorrosion properties of the developedcoatings were evaluated by the anodic polarization and elec-trochemical impedance spectroscopy techniquesThe surfacemorphology and phase structure of coated films were also

examined using scanning electron microscope (SEM) X-ray diffraction (XRD) and Energy Dispersive Spectroscopy(EDS) The HAp coating could enhance the anticorrosionproperty and effectively improved in vitro bioactivity insimulated body fluid

2 Materials and Methods

21 Specimens Preparation Commercially available AZ31Mgalloy (3 mass Al 1 mass Zn) was used as the substrateThe chemical composition of the alloy is listed in Table 1Thesurface of the alloys was polished up to no 2000 emery paperfollowed by 005 120583m alumina powders The specimens werecarefully cleaned with water rinsed with acetone and driedunder air All of the experiment specimens were mountedusing polytetrafluoroethylene (PTFE) resin tape leaving andexposed surface area of 1 cm2

22 The Film Formation The specimens were immersed in3mM Ca(H

2PO4)2+ 7mM CaCl

2solution at 37∘C and pH

6 for 30min The electrodeposition was performed at minus14minus16 and minus18 V applied potentials using a conventional elec-trochemical cell equipped with three electrodes PlatinumAgAgCl sat KCl and magnesium alloy specimen servedas the counter the reference and the working electroderespectively

23 Characterization Methods The morphology andmicrostructure of the films were observed with HitachiS-800 scanning electron microscope (SEM) The crystalstructure of the coated films was identified using thin film X-ray diffraction (XRD) analysis using a Shimadzu XRD-6000X-ray diffractometer with Cu K120572 radiation with scan step002∘ and scan speed 2∘min from diffraction angle of 10 to60 at 30 kV and 20mA The elemental composition of thecoating was identified using Energy Dispersive Spectroscopy(EDS)

24 Anticorrosion Measurements The anodic polarizationand electrochemical impedance spectroscopy tests were car-ried out using a Solartron 1285 Potentiostat from SolartronAnalytical Farnborough United Kingdom The measure-ments were controlled by Scribner Associates Corrware andZ polt electrochemical experiment software respectivelyThepolarization curves were measured in phosphate bufferedsaline PBS(minus) solutions with a scanning rate of 1mVs

25 Bioactivity Experiment in Simulated Body Fluid Thecoating was immersed for 7 days in the SBF (Kokubosolution) with ion concentrations nearly the same as thoseof the body blood plasma The pH of the SBF solution wasadjusted to 74 The phase structure surface morphologyand the anticorrosion property were examined every dayby removing the specimens from SBF solution rinsed withdistilled water and air-dried


10120583m

1120583m




10

8

6

4

2




Curr

ent d

ensit

y119894

(mA

middotcmminus2)





104

103

102

10000 2000 3000

Nontreated

Cor

rosio

n re

sista

nce119877

ct(W

middotcm2)


minus14 V

minus18 V

minus16 V




2PO4)2and 7mM CaCl

2solution for 30min



(a) (b)

1 120583m

(c)


(a) (b)

10 20 30 40 50 60

MgMg(OH)2

HApDCPD

2120579 Cu K 120572

(c)


AlAl

(a)

Ca

PO

(b)

Mg

(c)

CaCl


(d)










2

(Ca10(PO4)

6(OH)2)

(3)


4sdot 2H2O (4)











4 Conclusions




Acknowledgments


References






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


10120583m

1120583m




10

8

6

4

2




Curr

ent d

ensit

y119894

(mA

middotcmminus2)





104

103

102

10000 2000 3000

Nontreated

Cor

rosio

n re

sista

nce119877

ct(W

middotcm2)


minus14 V

minus18 V

minus16 V




2PO4)2and 7mM CaCl

2solution for 30min



(a) (b)

1 120583m

(c)


(a) (b)

10 20 30 40 50 60

MgMg(OH)2

HApDCPD

2120579 Cu K 120572

(c)


AlAl

(a)

Ca

PO

(b)

Mg

(c)

CaCl


(d)










2

(Ca10(PO4)

6(OH)2)

(3)


4sdot 2H2O (4)











4 Conclusions




Acknowledgments


References






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


(a) (b)

1 120583m

(c)


(a) (b)

10 20 30 40 50 60

MgMg(OH)2

HApDCPD

2120579 Cu K 120572

(c)


AlAl

(a)

Ca

PO

(b)

Mg

(c)

CaCl


(d)










2

(Ca10(PO4)

6(OH)2)

(3)


4sdot 2H2O (4)











4 Conclusions




Acknowledgments


References






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of









2

(Ca10(PO4)

6(OH)2)

(3)


4sdot 2H2O (4)











4 Conclusions




Acknowledgments


References






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Research Article Preparation and Characterization of Hydroxyapatite...

Documents

Transcript of Research Article Preparation and Characterization of Hydroxyapatite...