Research Article Magnetron Sputtering a New ... - Hindawi

Research ArticleMagnetron Sputtering a New Fabrication Method ofIron Based Biodegradable Implant Materials

Till Jurgeleit Eckhard Quandt and Christiane Zamponi

Chair for Inorganic Functional Materials Institute for Materials Science Faculty of Engineering University of KielKaiserstrasse 2 24143 Kiel Germany

Correspondence should be addressed to Till Jurgeleit tijutfuni-kielde

Received 17 September 2015 Revised 3 December 2015 Accepted 6 December 2015

Academic Editor Jorg M K Wiezorek

Copyright copy 2015 Till Jurgeleit 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

It was shown in the previous decade that pure-iron has a large potential as a biodegradable medical implant material It isnecessary to tailor the material properties according to the intended use of the device It is of great interest to investigate notonly the influence of processing on the material properties but also alternative fabrication methods In this work for the first timemagnetron sputtering in combination with UV lithography was used to fabricate free standing patterned pure-iron thick filmsFor the intended use as biodegradable implant material free standing thick films were characterized in terms of microstructuredegradation performance and mechanical properties before and after various heat treatments The influence of microstructuralchanges on the degradation behavior was determined by linear polarization measurements The mechanical properties werecharacterized by tensile tests Microstructure surface and composition were investigated by scanning transmission electronmicroscopy (STEM) energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) measurementsThe foils exhibiteda preferential orientation in ⟨110⟩ direction and a fine grained structure Furthermore they showed a higher strength compared tocast iron and corrosion rates in the range of 01 mmyear Their mechanical properties were tuned by grain coarsening resulting ina slight increase of the degradation rate

1 Introduction

The usage of metallic materials as medical implants suchas stents meshes nails plates and screws nowadays is acommon treatment Implants often serve their purpose onlyduring a healing period of 3ndash12 months [1 2] afterwards thepresence of the implants involves the danger of complicationssuch as stent restenosis and chronic inflammation reactions[3] The best way to prevent such complications is the usageof degradable implants therefore metal based biodegradablematerials are subject to intense research in recent years [1 3ndash6]Themost prominent examples of biodegradablemetals aremagnesium and iron as well as some of their alloys [3] Bothmetals are essential elements in the human metabolism Thedegradation of pure-magnesium was reported to occur fastand with a significant amount of hydrogen evolution [7ndash10]while pure-iron degrades rather slow and without hydrogenevolution Iron additionally exhibits a higher mechanical

strength compared to pure-magnesium [1 10 11] In vivostudies by Peuster et al [1 12] with New Zealand rabbits andmini pigs showed that it is possible to implant degradablepure-iron stents in the descending aorta No significantobstructions of the vessel caused by inflammation neointi-mal proliferation or thrombotic events were observed in thestudy Neither local or systemic toxicity nor an enrichmentof corrosion products in the organs was found however theyfound the corrosion rate of pure-iron to be too slow

In the previous decade several attemptswere presented [411 13ndash22] with the aim to tailor the degradation performanceand the mechanical properties of iron by influencing thegrain structure or changing the material composition In thiswork a new method to produce patterned and free standingpure-iron foils by magnetron sputtering in combination withUV-lithography is presentedThe method is most commonlyused in the thin film technology The fabrication of bulkfree standingNiTi thin films via sputtering was demonstrated

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2015 Article ID 294686 9 pageshttpdxdoiorg1011552015294686

2 Advances in Materials Science and Engineering

by Zamponi et al [23 24] Lima de Miranda et al [25 26]showed that by using 3D lithography or micro laser welding3D structures like tubular stents can also be produced bymagnetron sputtering A similar method for the fabricationof biodegradable free standing structured Mg-alloy foils bymagnetron sputtering was presented by Schluter et al [27ndash29] In order to modify corrosion behavior and mechan-ical properties the sputter technology offers not only theopportunity of depositing pure-iron and alloys but also thefabrication of ironmultilayer composites with noncompoundforming elements [30]

Depending on the application sputtering allows a veryprecise control of the layer thickness from submicron scale upto 100 120583m or even more by varying the process parametersAnother important feature for the fabrication of implants isthe freedom of design which is possible by the lithographicpatterning and allows resolutions in the 120583m range

For the intended use as biodegradable implant materialthe free standing foils were characterized with respect to cor-rosion behavior mechanical properties and microstructureFurthermore the influence of ex situ heat treatments on thematerial properties was investigated

2 Materials and Methods

21 Specimen Fabrication and Preparation All films weredeposited using a vonArdenne CS730 cluster sputteringmachine with a base pressure in the 10minus8mbar range

In the first step a 05 120583m thick Cu sacrificial layer wassputtered on a 410158401015840 500120583m thick (100) oriented Si-wafer Thewaferwas structured viaUV-lithography followed by galvanicCu-deposition in order to produce dog-bone shaped foils[18 19] Afterwards iron was deposited on these structuredsubstrates Due to the ferromagnetic nature of 120572-iron RF-sputtering was used to allow depositions at lower working gaspressures A magnetically calibrated 810158401015840 disk made of 999pure cast iron was used as target material To determine thetemperature during the deposition temperature indicatorswere used The sputter parameters are listed in Table 1

After the deposition of the iron selective wet etchingof the sacrificial layer was performed using a solutioncontaining DI-water NH

3

and H2

O2

in order to release thefoils from the substrate Finally the free standing structuredfoils were cleaned in an ultrasonic bath with isopropanol andDI-water In order to alter the microstructure the sampleswere annealed at 400∘C 600∘C and 800∘C for two hoursadditionally samples at 600∘C were annealed for differenttimes of 20min 1 h and 2 h The sputtered free standing Fe-foils (s-Fe) were annealed under reducing atmosphere (95Ar and 5 H

2

VARIGON H5) in order to prevent oxidation

22 Investigations of Microstructure To determine the crys-tallinity and texture of the specimens XRD measurementswere performed with a Seifert XRD-300 PTS X-ray diffrac-tometer employing monochromatic Cu-K

120572

radiationThe 120579-2120579-absolute scans were performed in the range of 35∘ to 90∘with 005∘ step width and 2 sec dwell time per step Scanningtransmission electronmicroscopy (STEM)was used to obtain

further information about the microstructures serving thispurpose cross sections of the foils were prepared by focusedion beam (FIB) using a Helios NanoLab 600 (FEI) STEMimageswere captured using bright field (BF) and high angularannular dark field (HAADF) detectors The determinationof the average grain size was done by evaluating SEMsurface images with a line intersectionmethod [31] Scanningelectronmicroscopy on anUltra Plus device byZeisswas usedto investigate the surface and fracture areas of the samples

23 Mechanical Properties Tensile tests were performed formechanical characterization Therefore ldquodog-bonerdquo shapedsamples (Figure 1) with 05mm strut width and 7mm strutlength were produced as explained previously The thicknesswas homogenous for all samples and varied depending on thebatch between 28 120583m and 32 120583m

The uniaxial tensile tests were performed with a testingmachine of the type BETA 5-56 times 10 (Messphysik) using aspecial sample holder for thin samples A straining rate of04min was applied the fracture criterion was set to 60force reduction relative to the maximum applied force Foreach heat treatment four samples were measured

24 Corrosion Measurements A VersaSTAT 3-300 poten-tiostat connected to a three-electrode cell was used forthe electrochemical corrosion tests Quadratic foils with anedge length of 15mm and 10 120583m thickness were used forthe corrosion measurements Since the foils exhibit mirrorfinish (119877

119886

= 14 nm plusmn 3 nm) after deposition no additionalconditioning or polishing steps were required The sampleswere mounted on a sample holder acting as the workingelectrode (WE)with an exposed area of 0916 cm2 As counterelectrode (CE) a Pt mesh as well as wire was used AnAgAgCl electrode in a 3-molar KCl solution acted as ref-erence electrode (RE) Hankrsquos balanced salt solution (HBSS)(H1387 Sigma Aldrich) modified with sodium bicarbonate(035 gL) was used as electrolyte The temperature was heldconstant at 37∘C Furthermore a regulated CO

2

inlet was usedto keep the pH value at 74 plusmn 005 A schematic sketch of thesetup is given in Figure 2

After determining the corrosion potential119880119888

in an 4000 slong open circuit (OC)measurement themeasurement of the119868(119880) curves was performed for this the WE was polarizedfrom minus400mV to +400mV around 119880

119888

with a potential shiftrate of 1mVs The Tafel extrapolation method was employedto calculate the corrosion rate (CR) from the 119868(119880) curves[32 33] Using the exposed electrode area the current wasconverted into the current density By fitting the linearregimes of the logarithmically plotted 119895(119880) curve followedby extrapolation to 119880

119888

the corrosion current density 119895119888

wasdeterminedThe corrosion ratewas calculated using (1)whichis based on Faradayrsquos law [32 33]

CR =119895119888

119872

119899120588119865 (1)

Here119872 is the molar mass of the corroding species 120588 is thedensity 119899 is the number of transferred elementary chargesper reaction step and 119865 is Faraday constant Under the

Advances in Materials Science and Engineering 3

Table 1 Sputtering parameters

Element Power (W) Pressure (mbar) Ar gas flow (sccm) Sputter rate (nms)Cu 1000 (DC) 23 sdot 10

minus3 25 41Fe 600 (RF) 23 sdot 10

minus3 35 06

6mm

15m

m

7m

m

4m

m 05mm

Figure 1 Dimensions of a ldquodog-bonerdquo sample for tensile testsThe thickness of the different samples varied depending on batchbetween 28 120583m and 32 120583m

assumption based on studies by Zhu et al [34] on thedegradation kinetics of pure-iron in physiological fluids ironis anodic dissolved as follows Feminus2eminus rarr Fe2+ so that 119899 = 2With119872 = 0056 kgmol 120588 = 7874 kgm3 and a conversionfactor of 31536 the CR can be calculated in terms ofmmyearFor each annealing temperature four samples weremeasured

3 Results and Discussions

31 Characterization of Microstructure The XRD measure-ments (Figure 3) and the STEM investigations (Figure 4)of the as-deposited s-Fe showed a fine grained structurewith columnar growth and strongly preferred orientation inthe ⟨110⟩ direction Since the samples were measured ona Si-substrate additionally the Cu (111) reflection from thesacrificial layer and Si (400) reflection from the substrateare visible Only the 120572-Fe (110) reflection is present after allheat treatments independent of the temperature The s-Feshows no sign of film stress since a relaxation of film stressduring annealing would lead to a shift in the XRD peakposition The evaluation of the average grain size is shownin Figure 5 The obtained results are in good agreementwith STEM images (Figure 4) A similar microstructure isobserved for the as-deposited sample and those annealed at400∘C After annealing at 600∘C and two hours the samplesshow an inhomogeneous grain growth whereas some grainsgrow up to diameters of 25 120583m other grains retain the initialsize (05 120583m) After annealing for two hours at 800∘C on the

one hand large grains up to 15120583mandon the other hand smallgrains in the range of 05 120583m to 1 120583m were observed

Thornton and Hoffman [35ndash39] established the structurezone model which explains the dependence of the depositionconditions on themicrostructure of sputtered filmsThe ratioof substrate temperature to melting temperature 119879sub119879melt aswell as the working gas pressure during the deposition has astrong influence on the film growth Considering the mea-sured substrate temperatures (asymp400∘C) the ratio 119879sub119879melt asymp037 results in small columnar defect rich grains (Figure 4as-deposited) As expected annealing at 400∘C shows noinfluence on the microstructure since the temperature is toolow for a recrystallization (119879sub119879melt asymp 04ndash05) or defectrecovery At 600∘C (119879sub119879melt = 048) the recrystallizationstarts By increasing the annealing temperature to 800∘Cthe recrystallization can propagate much faster due to anenhanced generation of thermal vacancies and the increasedself-diffusion Since all samples before and after annealingshow the columnar ⟨110⟩ oriented grains a secondaryrecrystallization mechanism is assumed where large grainsgrow at the expense of smaller ones by shifting their grainboundaries in order to minimize the grain boundary anddislocation energy In a review paper by Thompson [40]dealing with the recrystallization in thin films it is statedthat recrystallization processes in nonbulk samples where thesmallest sample dimension is much larger compared to thegrain size surface and interface energies play an importantrole Particularly if the columnar grains extend over theentire sample thickness usually primary grain growth stopsand secondary recrystallization processes occur Thus theobserved recrystallization behavior is explained by the grainstructure and small sample dimensions of the sputtered ironfoils

32 Mechanical Properties Some exemplary stress-straincurves of s-Fe after annealing with different annealing tem-peratures and annealing times are given in Figure 6 Meanvalues and standard deviation of the measured samples aswell as some literature values for biodegradable metals arelisted in Table 2 In general with increasing annealing tem-perature or time a decrease of strength and an increase of theductility can be observedThe fracture area of an as-depositedtensile test sample is shown in Figure 7(a) A ductile fracturebehavior with a clear necking can be observed The samplesannealed at 600∘C and various times (Figure 6) show that thebiggest change in the mechanical properties occurs betweenone- and two-hour heating time giving an impression aboutthe recrystallization speedThe obtained values are correlatedto the annealing temperature and yield strength in Figure 7According to the Thornton model [35ndash38] and the substratetemperature the as-deposited structure is in the low tempera-ture endof the transition zonewhere a large amount of defects


pH-control-unit

pH 74

rese

rvoi

r

Potentiostat

Heating platemagnetic stirrer

Heat-bathRE

CE

Ther

moc

oupl

e

Sam

ple (

WE)

Hab

er-L

uggi

nca

pilla

ry

HBSSStirrer

Stirrer

pH-e

lect

rode

Cover

37∘C

CO2

CO2

CO2

inle

t

Figure 2 Schematic sketch of the corrosion measurement A standard three-electrode setup is placed in the corrosion cell filled with Hankrsquosbuffered salt solutionThe temperature is held at 37∘C by a heating bath By measuring the pH-value CO

2

inlet regulation the pH value of thesolution is constantly kept at 74

40 50 60 70 80 90

Inte

nsity

(au

)

120572-F

e (110

)

s-Fe 800∘C 2h 120572-F

e (200

)

120572-F

e (211

)

s-Fe 600∘C 2h

s-Fe 400∘C 2h

Cu (1

11)

s-Fe as-deposited Si (4

00)

2120579 angle (∘)

Figure 3 XRD 120579-2120579 scan of as-deposited and annealed s-Fe foilsDue to the preferred (110) orientation before and after annealingonly the corresponding reflection is visible No peak shift due tostress relaxation is noticeable Also the possible120572-Fe (200) reflectionand 120572-Fe (211) reflection are indicated by vertical dash lines

like dislocations vacancies and stacking faults is presentThereason for this is particles of high kinetic energy which hitthe surface and thus enhance the formation of defects Dueto the substrate temperature during the deposition there isnot enough activation energy for significant bulk diffusionwhich would lead to in situ annealing during the depositionSo the high initial strength is explained by the large amountof defects Since the defects act as obstacles for dislocationmovement and plastic deformation respectively the highdefect density results in high internal stresses during thedeformation which leads to an early fracture

The presented results are in good agreement with studieson the mechanical properties of sputtered films reviewedby Bunshah [41] In the review paper it was concludedthat metals sputtered in temperature regions correspondingto the transition zone show a high strength and a lowductility comparable to those of mechanical worked mate-rial (see also Table 2 UDlowast-Fe) Due to the increased graingrowth at high temperatures a decrease of the strength isobserved This behavior is explained by the grain coarseningin agreement with the well-known Hall-Petch relation [42]


As-deposited

2120583m

2120583m 4120583m

4120583m

⟨110⟩

Annealed at 400∘C 2h Annealed at 600∘C 2h

Annealed at 800∘C 2h

Figure 4 STEM images of s-Fe annealed at different temperatures for two hours

Table 2 Measured mechanical properties of s-Fe after different annealing treatments and published literature values

Sample Yield strength (MPa) Ultimate tensile strength (MPa) Strain at fracture ()s-Fe as-deposited 606 plusmn 33 634 plusmn 33 14 plusmn 01s-Fe annealed at 400∘C 2 h 604 plusmn 19 616 plusmn 9 16 plusmn 04s-Fe annealed at 600∘C 20min 612 plusmn 20 638 plusmn 10 13 plusmn 02s-Fe annealed at 600∘C 1 h 568 plusmn 23 584 plusmn 33 20 plusmn 05s-Fe annealed at 600∘C 2 h 381 plusmn 29 413 plusmn 9 13 plusmn 36s-Fe annealed at 800∘C 2 h 267 plusmn 7 343 plusmn 47 20 plusmn 26E-Fe annealed at 550∘C [14] 270 plusmn 6 292 plusmn 14 184 plusmn 4E-Fe annealed at 600∘C [14] 130 plusmn 7 169 plusmn 9 323 plusmn 5Cast iron annealed at 550∘C [14] 140 plusmn 10 205 plusmn 6 255 plusmnmdashFe35Mn [15] 234 plusmn 7 428 plusmn 7 320 plusmn 08Armco Fe annealed [19] 170 plusmnmdash 270 plusmnmdash 493 plusmnmdashFe(X) alloys as cast [18] 100ndash220 200ndash360 10ndash25Fe(X) alloys as rolled [18] 360ndash450 430ndash850 5ndash9UDlowast-Fe [20] 593 plusmn 2 600 plusmn 8 35 plusmn 2UDlowast-Fe annealed [20] 246 plusmn 3 283 plusmn 5 348 plusmn 8WE43 Mg alloy [8] 198 plusmnmdash 277 plusmnmdash 17 plusmnmdash316L SS [3] 190 plusmnmdash 490 plusmnmdash 40 plusmnmdashElectroformedlowastUnidirectional rolled


Table 3 Results of linear polarization corrosion measurements of s-Fe samples compared literature values

SampleCorrosion rate Corrosion potentialCR (mmyear) 119880

119888

(V)

s-Fe as-deposited 006 plusmn 002 minus0487 plusmn 0052s-Fe annealed at400∘C 2 h

007 plusmn 001 minus0579 plusmn 0015

s-Fe annealed at 600∘C 2 h 008 plusmn 004 minus0659 plusmn 0016


E-Fe as-deposited [14] 085 plusmn 005 minus0824 plusmn 0018

E-Fe annealed [14] 051 plusmn 006 minus0776 plusmn 0020

Cast-iron annealed [14] 016 plusmn 004 minus0732 plusmn 0016

Fe35Mn [15] 04 plusmn 01 NA

Pure Fe [18] 010 plusmnmdash minus0748 plusmnmdash

Fe(X) alloys as rolled [18] 010ndash018 minus0680ndash(minus0728)

Armco Fe annealed [19] 021 plusmn 004 minus0735 plusmn 11

UDlowast-Fe annealed [20] 024 plusmn 002 minus0724 plusmn 4

Pure-Fe [10] 010 plusmnmdash minus0748 plusmnmdashElectroformedlowastUnidirectional rolled

Aver

age g

rain

size

(120583m

)

4

3

2

1

0

Annealing temperature (∘C)

As-deposited 400∘C 600∘C 800∘C

Yiel

d str

engt

h (M

Pa)

700

600

500

400

300

200

100

0

Figure 5 Graphical correlation between grain size annealingtemperature and the yield strength of s-Fe annealed for two hours

Due to the discussed recrystallization behavior the graingrowth is nonhomogeneous thus the very small grains whichcoexist with the larger ones act as obstacles for plasticdeformation and therefore counteract the decrease of thestrength explaining the comparably high residual strengthafter annealing Increasing the annealing temperature andtime strongly enhances the ductility of the material at theexpense of its strength This is mainly due to the recoveryof defects which in turn reduces internal stresses necessaryfor dislocation movement Due to patterning process theedges show a higher roughness compared to the surface(Figure 7(b)) which can act as a nucleus for crack initiationTherefore the strain at fracture could be further increased by

improving the quality of the edges by chemical polishing orelectropolishing respectively

A graphical summary of the results and comparison toliterature values for biodegradable materials are given inFigure 8 Compared to theWE43Mg alloy and pure-iron val-ues from the literature [8 14 18ndash20] the presented annealeds-Fe shows a higher strength The values are approachingthose of the 316L SS alloy which acts as gold standard [3]for vascular stents and other iron based biodegradable Fealloys [15 18] With regard to possible applications it has tobe considered the best compromise between strength andductility to tailor the mechanical properties by appropriateheat treatments

33 Corrosion Measurements Some exemplary linear polar-ization curves for s-Fe annealed at different temperaturesare shown in Figure 9 With increasing grain size a shiftof the corrosion potential to more negative values can beobserved This is associated with a slight increase of thecorrosion rate The calculated mean values and standarddeviations are summarized in Table 3 The results of thisstudy are in good agreement with those found by Cheng andLiu [10 18] It is well known [13 19ndash21 43] that changesin the grain size affect the corrosion rate of iron Forbiodegradable Mg-alloys it was shown [42 43] that grainrefinement leads to an improved corrosion resistance AlsoObayi et al [19 20] qualitatively observed the same behaviorfor pure-iron Studies by Ralston et al [44] and Nie etal [21 22] on the degradation kinetics of nanocrystalline(NC) and microcrystalline (MC) pure-iron concluded thatin metals which tend to the formation of passive oxide layerssuch as iron an increase of the grain boundary densitypromotes the formation of a passivation layer However


0 5 10 15

s-Fe as-deposited

0

200

400

600

Stre

ss (M

Pa)

Strain ()

s-Fe annealed at 600∘C 20min

s-Fe annealed at 600∘C 1h


(a)

s-Fe as-deposited

0

200

400

600

Stre

ss (M

Pa)

0 5 10 15 20Strain ()




(b)

Figure 6 Exemplary stress strain curves of s-Fe annealed at 600∘C for different dwell times (a) and at different temperatures for two hours(b)

10120583m10120583m

(a)

3120583m

(b)

Figure 7 SEM image of fracture area (a) with significant necking SEM image of the rough edge surface of an as-deposited dog-bone sample(b) The highlighted ldquofeetrdquo arises due to shadowing effects of the galvanic deposited Cu during sputtering on the substrate side

studies by Moravej et al [14] with electroformed iron (E-Fe)showed a decrease in the CR with increasing grain size thisbehavior was related to the large amount of defects whichare acting as active sites for corrosion Since in general thesputtered microstructure shows similar characteristics alsoa similar corrosion behavior could be expected Howeverthe used target material in this study has a higher puritycompared to those reported for the E-Fe Therefore the highcorrosion rates reported in the study could be related to theimpurities acting as active sites for corrosionThe comparablylow corrosion rate in this study can be explained by thehigh purity and fine-grained microstructure which promotesthe formation of a passive layer The slight increase of thecorrosion rate with increasing grain size is assumed beingattributed to a thinner and less stable passive oxide on largergrains [21 22 44] However counteracting to this effect thereis a decrease in the defect density which might be the reasonfor the rather weak influence of the grain coarsening on thecorrosion rate

4 Conclusion

It is shown that it is possible to produce free standingpatterned pure-iron foils via magnetron sputteringThe foilsshow improved mechanical strength compared to cast Fe Itis possible to adjust the mechanical properties by a postde-position annealing process The samples show a comparablelow degradation rate which is slightly increased by annealingand grain coarsening Due to the higher mechanical strengththinner structures suffice to resist a load in a potential deviceso that less material has to degrade Moreover the presentedmethod offers a large freedom of design which allows thefabrication of filigree structures In combination with thehigh strength suitable designs can increase the surface tovolume ratio and thus offer the potential to relativize therather low corrosion rate

Additionally there are a number of possibilities to accel-erate the rate further by the deposition of more complexiron based systems One possibility is the usage of prealloyed


0 5 10 15 20 25 30 35 40 45 50 55 60

200

400

600s-Fe as-deposited

WE43 Mg alloy [8]Cast iron annealed [14]

SS316L [3]

Fe35Mn [15]

Armco Fe annealed [19]

UD-Fe annealed [20]

Strain at fracture ()

Ulti

mat

e ten

sile s

treng

thRp

(MPa

)

s-Fe annealed at 600∘C


E-Fe annealed at 600∘C [14]


Figure 8Overview of themechanical properties found in this studyfor different annealed samples (as-deposited 600∘C 2 h and 800∘C2 h) compared to literature values for biodegradable materials

|j|

(A m

minus2)

10

1

01

001

1E minus 3

1E minus 4

U (V) versus AgAgClminus08 minus07 minus06 minus05 minus04 minus03

s-Fe

as-d

epos

ited

s-Fe

800∘ C

2h

s-Fe

600

∘ C2

h

s-Fe

400

∘ C2

h

Figure 9 Exemplary Tafel-curves of s-Fe annealed at different tem-peratures for two hours With increasing annealing temperaturesa shift of 119880

119888

to more negative values and slight increase of 119895119888

isobserved

sputter-targets with suitable elements Another approach isthe fabrication of multilayer composites with solvable oreven nonsolvable elements In combination with appropriatepostdeposition heat treatments it is possible to fabricate inthismanner tailoredmicrostructures andmaterial propertiesrespectively

Investigation in terms of foil thickness and patterningresolution limits are subject of current research Furthermoreit has to be proven that the mentioned 3D lithographyor microlaser welding [25 26] can be applied for ironbased sputtered material to allow the production of threedimensional devices like stents Since the in vitro character-ization can just compare different materials in terms of their

properties in further studies in vitro cell tests have to beperformed to assess how the material could behave in vivo

Themagnetron sputtering technique in combinationwithUV-lithography allows the fabrication of in situ patterneddevices Thus magnetron sputter technology offers a largepotential to further improve the mechanical properties andcorrosion behavior Finally the presentedmethod is a promis-ing candidate in the fabrication technology of iron basedbiodegradable devices with filigree designs

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

Funding via DFG is gratefully acknowledged The authorsfurther acknowledge Jan Johansen and Bastian Hirsch forsupporting this work in the tensile tests

References

[1] M Peuster C Hesse T Schloo C Fink P Beerbaum andC von Schnakenburg ldquoLong-term biocompatibility of a cor-rodible peripheral iron stent in the porcine descending aortardquoBiomaterials vol 27 no 28 pp 4955ndash4962 2006

[2] P K Bowen J Drelich and J Goldman ldquoZinc exhibits idealphysiological corrosion behavior for bioabsorbable stentsrdquoAdvanced Materials vol 25 no 18 pp 2577ndash2582 2013

[3] H Hermawan Biodegradable Metals From Concept to Appli-cations Biodegradable Metals for Cardiovascular ApplicationsSpringer Heidelberg Germany 2012

[4] H Hermawan H Alamdari D Mantovani and D DubeldquoIron-manganese new class ofmetallic degradable biomaterialsprepared by powder metallurgyrdquo Powder Metallurgy vol 51 no1 pp 38ndash45 2008

[5] A Colombo and E Karvouni ldquoBiodegradable stents lsquofulfillingthe mission and stepping awayrsquordquo Circulation vol 102 no 4 pp371ndash373 2000

[6] E Wintermantel and S HaMedizintechnik mit BiokompatiblenWerkstoffen und Verfahren Resorbierbare Implantate SpringerHeidelberg Germany 2007

[7] M P Staiger A M Pietak J Huadmai and G Dias ldquoMag-nesium and its alloys as orthopedic biomaterials a reviewrdquoBiomaterials vol 27 no 9 pp 1728ndash1734 2006

[8] F Witte N Hort C Vogt et al ldquoDegradable biomaterials basedon magnesium corrosionrdquo Current Opinion in Solid State andMaterials Science vol 12 no 5-6 pp 63ndash72 2008

[9] F Witte ldquoThe history of biodegradable magnesium implants areviewrdquo Acta Biomaterialia vol 6 no 5 pp 1680ndash1692 2010

[10] J Cheng B Liu Y H Wu and Y F Zheng ldquoComparativein vitro study on pure metals (Fe Mn Mg Zn and W) asbiodegradable metalsrdquo Journal of Materials Science amp Technol-ogy vol 29 no 7 pp 619ndash627 2013

[11] Y F Zheng X N Gu and F Witte ldquoBiodegradable metalsrdquoMaterials Science and Engineering R Reports vol 77 pp 1ndash342014

[12] M Peuster P Wohlsein M Brugmann et al ldquoA novelapproach to temporary stenting degradable cardiovascular


stents produced from corrodible metalmdashresults 6-18 monthsafter implantation into New Zealand white rabbitsrdquo Heart vol86 no 5 pp 563ndash569 2001

[13] K D Ralston and N Birbilis ldquoEffect of grain size on corrosiona reviewrdquo Corrosion vol 66 no 7 2010

[14] M Moravej F Prima M Fiset and D Mantovani ldquoElectro-formed iron as new biomaterial for degradable stents devel-opment process and structure-properties relationshiprdquo ActaBiomaterialia vol 6 no 5 pp 1726ndash1735 2010

[15] H Hermawan D Dube and D Mantovani ldquoDegradablemetallic biomaterials design and development of FendashMn alloysfor stentsrdquo Journal of Biomedical Materials Research Part A vol93 no 1 pp 1ndash11 2010

[16] 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

[17] M Schinhammer P Steiger F Moszner J F Loffler andP J Uggowitzer ldquoDegradation performance of biodegradableFeMnC(Pd) alloysrdquoMaterials Science and Engineering C vol 33no 4 pp 1882ndash1893 2013

[18] B Liu and Y F Zheng ldquoEffects of alloying elements (MnCo Al W Sn B C and S) on biodegradability and in vitrobiocompatibility of pure ironrdquo Acta Biomaterialia vol 7 no 3pp 1407ndash1420 2011

[19] C S Obayi R Tolouei A Mostavan et al ldquoEffect of grain sizeson mechanical properties and biodegradation behavior of pureiron for cardiovascular stent applicationrdquo Biomatter 2014

[20] C S Obayi R Tolouei C Paternoster et al ldquoInfluence ofcross-rolling on the micro-texture and biodegradation of pureiron as biodegradable material for medical implantsrdquo ActaBiomaterialia vol 17 pp 68ndash77 2015

[21] F L Nie Y F Zheng S C Wei C Hu and G Yang ldquoInvitro corrosion cytotoxicity and hemocompatibility of bulknanocrystalline pure ironrdquo Biomedical Materials vol 5 no 6Article ID 065015 2010

[22] F L Nie and Y F Zheng ldquoSurface chemistry of bulk nanocrys-talline pure iron and electrochemistry study in gas-flow physio-logical salinerdquo Journal of Biomedical Materials Research Part BApplied Biomaterials vol 100 no 5 pp 1404ndash1410 2012

[23] C Zamponi H Rumpf C Schmutz and E Quandt ldquoStructur-ing of sputtered superelastic NiTi thin films by photolithogra-phy and etchingrdquoMaterials Science and Engineering A vol 481-482 pp 623ndash625 2008

[24] R Lima de Miranda C Zamponi and E Quandt ldquoMicropat-terned freestanding superelastic TiNi filmsrdquo Advanced Engi-neering Materials vol 15 no 1-2 pp 66ndash69 2013

[25] R Lima de Miranda C Zamponi and E Quandt ldquoFabricationof TiNi thin film stentsrdquo Smart Materials and Structures vol 18no 10 Article ID 104010 2009

[26] G Siekmeyer A Schuszligler R Lima deMiranda and E QuandtldquoComparison of the fatigue performance of commercially pro-duced nitinol samples versus sputter-deposited nitinolrdquo Journalof Materials Engineering and Performance vol 23 no 7 pp2437ndash2445 2014

[27] K Schluter Z Shi C Zamponi F Cao E Quandt and AAtrens ldquoCorrosion performance and mechanical properties ofsputter-deposited MgY and MgGd alloysrdquo Corrosion Sciencevol 78 pp 43ndash54 2014

[28] K Schluter C Zamponi N Hort K U Kainer and E QuandtldquoPolycrystalline and amorphousMgZnCa thin filmsrdquoCorrosionScience vol 63 pp 234ndash238 2012

[29] K Schluter C Zamponi A Piorra and E Quandt ldquoCompari-son of the corrosion behaviour of bulk and thin filmmagnesiumalloysrdquo Corrosion Science vol 52 no 12 pp 3973ndash3977 2010

[30] C Zamponi U Schurmann T Jurgeleit L Kienle and EQuandt ldquoMicrostructures of magnetron sputtered Fe Au thinfilmsrdquo International Journal of Materials Research vol 106 no2 pp 103ndash107 2015

[31] ASTM E-112 ldquoMetal test methods and analytical proceduresrdquoin Annual Book of ASTM Standards vol 0301 section 3 ASTMInternational West Conshohocken Pa USA 2007

[32] M Stern and A L Geary ldquoElectrochemical polarization I atheoretical analysis of the shape of polarization curvesrdquo Journalof the Electrochemical Society vol 104 no 1 pp 56ndash63 1957

[33] D A Jones ldquoElectrochemical kinetics of corrosion polariza-tion methods to measure corrosion raterdquo in Principles andPrevention of Corrosion pp 75ndash162 Pearson-Prentice HallInternational London UK 2005

[34] S Zhu N Huang L Xu et al ldquoBiocompatibility of pure ironin vitro assessment of degradation kinetics and cytotoxicity onendothelial cellsrdquo Materials Science and Engineering C vol 29no 5 pp 1589ndash1592 2009

[35] J A Thornton and D W Hoffman ldquoInternal stresses intitanium nickel molybdenum and tantalumfilms deposited bycylindrical magnetron sputteringrdquo Journal of Vacuum Science ampTechnology vol 14 no 1 pp 164ndash168 1976

[36] J A Thornton ldquoInfluence of apparatus geometry and depo-sition conditions on the structure and topography of thicksputtered coatingsrdquo Journal of Vacuum Science amp Technologyvol 11 no 4 pp 666ndash670 1974

[37] J A Thornton ldquoHigh rate thick film growthrdquo Annual Review ofMaterials Science vol 7 pp 239ndash260 1977

[38] J A Thornton ldquoThe microstructure of sputter deposited coat-ingsrdquo Journal of Vacuum Science amp Technology A vol 4 no 6pp 3059ndash3065 1986

[39] J AThornton andDWHoffman ldquoStress-related effects in thinfilmsrdquoThin Solid Films vol 171 no 1 pp 5ndash31 1989

[40] C V Thompson ldquoGrain growth in thin filmsrdquo Annual Reviewof Materials Science vol 20 no 1 pp 245ndash268 1990

[41] R F Bunshah ldquo31 mechanical properties of PVD filmsrdquoVacuum vol 27 no 4 pp 353ndash362 1977

[42] R W Cahn and P Haasen ldquoRecovery and recrystallizationrdquoin Physical Metallurgy vol 2 chapter 17 42 p 1589 ElsevierScience BV Amsterdam The Netherlands 4th edition 1996

[43] L Jinlong and L Hongyun ldquoThe effects of cold rolling tem-perature on corrosion resistance of pure ironrdquo Applied SurfaceScience vol 317 pp 125ndash130 2014

[44] K D Ralston N Birbilis and C H J Davies ldquoRevealing therelationship between grain size and corrosion rate of metalsrdquoScripta Materialia vol 63 no 12 pp 1201ndash1204 2010

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


by Zamponi et al [23 24] Lima de Miranda et al [25 26]showed that by using 3D lithography or micro laser welding3D structures like tubular stents can also be produced bymagnetron sputtering A similar method for the fabricationof biodegradable free standing structured Mg-alloy foils bymagnetron sputtering was presented by Schluter et al [27ndash29] In order to modify corrosion behavior and mechan-ical properties the sputter technology offers not only theopportunity of depositing pure-iron and alloys but also thefabrication of ironmultilayer composites with noncompoundforming elements [30]

Depending on the application sputtering allows a veryprecise control of the layer thickness from submicron scale upto 100 120583m or even more by varying the process parametersAnother important feature for the fabrication of implants isthe freedom of design which is possible by the lithographicpatterning and allows resolutions in the 120583m range

For the intended use as biodegradable implant materialthe free standing foils were characterized with respect to cor-rosion behavior mechanical properties and microstructureFurthermore the influence of ex situ heat treatments on thematerial properties was investigated

2 Materials and Methods

21 Specimen Fabrication and Preparation All films weredeposited using a vonArdenne CS730 cluster sputteringmachine with a base pressure in the 10minus8mbar range

In the first step a 05 120583m thick Cu sacrificial layer wassputtered on a 410158401015840 500120583m thick (100) oriented Si-wafer Thewaferwas structured viaUV-lithography followed by galvanicCu-deposition in order to produce dog-bone shaped foils[18 19] Afterwards iron was deposited on these structuredsubstrates Due to the ferromagnetic nature of 120572-iron RF-sputtering was used to allow depositions at lower working gaspressures A magnetically calibrated 810158401015840 disk made of 999pure cast iron was used as target material To determine thetemperature during the deposition temperature indicatorswere used The sputter parameters are listed in Table 1

After the deposition of the iron selective wet etchingof the sacrificial layer was performed using a solutioncontaining DI-water NH

3

and H2

O2

in order to release thefoils from the substrate Finally the free standing structuredfoils were cleaned in an ultrasonic bath with isopropanol andDI-water In order to alter the microstructure the sampleswere annealed at 400∘C 600∘C and 800∘C for two hoursadditionally samples at 600∘C were annealed for differenttimes of 20min 1 h and 2 h The sputtered free standing Fe-foils (s-Fe) were annealed under reducing atmosphere (95Ar and 5 H

2

VARIGON H5) in order to prevent oxidation

22 Investigations of Microstructure To determine the crys-tallinity and texture of the specimens XRD measurementswere performed with a Seifert XRD-300 PTS X-ray diffrac-tometer employing monochromatic Cu-K

120572

radiationThe 120579-2120579-absolute scans were performed in the range of 35∘ to 90∘with 005∘ step width and 2 sec dwell time per step Scanningtransmission electronmicroscopy (STEM)was used to obtain

further information about the microstructures serving thispurpose cross sections of the foils were prepared by focusedion beam (FIB) using a Helios NanoLab 600 (FEI) STEMimageswere captured using bright field (BF) and high angularannular dark field (HAADF) detectors The determinationof the average grain size was done by evaluating SEMsurface images with a line intersectionmethod [31] Scanningelectronmicroscopy on anUltra Plus device byZeisswas usedto investigate the surface and fracture areas of the samples

23 Mechanical Properties Tensile tests were performed formechanical characterization Therefore ldquodog-bonerdquo shapedsamples (Figure 1) with 05mm strut width and 7mm strutlength were produced as explained previously The thicknesswas homogenous for all samples and varied depending on thebatch between 28 120583m and 32 120583m

The uniaxial tensile tests were performed with a testingmachine of the type BETA 5-56 times 10 (Messphysik) using aspecial sample holder for thin samples A straining rate of04min was applied the fracture criterion was set to 60force reduction relative to the maximum applied force Foreach heat treatment four samples were measured

24 Corrosion Measurements A VersaSTAT 3-300 poten-tiostat connected to a three-electrode cell was used forthe electrochemical corrosion tests Quadratic foils with anedge length of 15mm and 10 120583m thickness were used forthe corrosion measurements Since the foils exhibit mirrorfinish (119877

119886

= 14 nm plusmn 3 nm) after deposition no additionalconditioning or polishing steps were required The sampleswere mounted on a sample holder acting as the workingelectrode (WE)with an exposed area of 0916 cm2 As counterelectrode (CE) a Pt mesh as well as wire was used AnAgAgCl electrode in a 3-molar KCl solution acted as ref-erence electrode (RE) Hankrsquos balanced salt solution (HBSS)(H1387 Sigma Aldrich) modified with sodium bicarbonate(035 gL) was used as electrolyte The temperature was heldconstant at 37∘C Furthermore a regulated CO

2

inlet was usedto keep the pH value at 74 plusmn 005 A schematic sketch of thesetup is given in Figure 2

After determining the corrosion potential119880119888

in an 4000 slong open circuit (OC)measurement themeasurement of the119868(119880) curves was performed for this the WE was polarizedfrom minus400mV to +400mV around 119880

119888

with a potential shiftrate of 1mVs The Tafel extrapolation method was employedto calculate the corrosion rate (CR) from the 119868(119880) curves[32 33] Using the exposed electrode area the current wasconverted into the current density By fitting the linearregimes of the logarithmically plotted 119895(119880) curve followedby extrapolation to 119880

119888

the corrosion current density 119895119888

wasdeterminedThe corrosion ratewas calculated using (1)whichis based on Faradayrsquos law [32 33]

CR =119895119888

119872

119899120588119865 (1)

Here119872 is the molar mass of the corroding species 120588 is thedensity 119899 is the number of transferred elementary chargesper reaction step and 119865 is Faraday constant Under the




minus3 25 41Fe 600 (RF) 23 sdot 10

minus3 35 06

6mm

15m

m

7m

m

4m

m 05mm









pH-control-unit

pH 74

rese

rvoi

r

Potentiostat


Heat-bathRE

CE

Ther

moc

oupl

e

Sam

ple (

WE)

Hab

er-L

uggi

nca

pilla

ry

HBSSStirrer

Stirrer

pH-e

lect

rode

Cover

37∘C

CO2

CO2

CO2

inle

t


2


40 50 60 70 80 90

Inte

nsity

(au

)

120572-F

e (110

)

s-Fe 800∘C 2h 120572-F

e (200

)

120572-F

e (211

)

s-Fe 600∘C 2h

s-Fe 400∘C 2h

Cu (1

11)


00)

2120579 angle (∘)





As-deposited

2120583m

2120583m 4120583m

4120583m

⟨110⟩









119888

(V)














Aver

age g

rain

size

(120583m

)

4

3

2

1

0



Yiel

d str

engt

h (M

Pa)

700

600

500

400

300

200

100

0







0 5 10 15

s-Fe as-deposited

0

200

400

600

Stre

ss (M

Pa)

Strain ()




(a)

s-Fe as-deposited

0

200

400

600

Stre

ss (M

Pa)

0 5 10 15 20Strain ()




(b)


10120583m10120583m

(a)

3120583m

(b)



4 Conclusion




0 5 10 15 20 25 30 35 40 45 50 55 60

200

400



SS316L [3]

Fe35Mn [15]


UD-Fe annealed [20]


Ulti

mat

e ten

sile s

treng

thRp

(MPa

)






|j|

(A m

minus2)

10

1

01

001

1E minus 3

1E minus 4


s-Fe

as-d

epos

ited

s-Fe

800∘ C

2h

s-Fe

600

∘ C2

h

s-Fe

400

∘ C2

h


119888


isobserved







Acknowledgments


References






















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






minus3 25 41Fe 600 (RF) 23 sdot 10

minus3 35 06

6mm

15m

m

7m

m

4m

m 05mm









pH-control-unit

pH 74

rese

rvoi

r

Potentiostat


Heat-bathRE

CE

Ther

moc

oupl

e

Sam

ple (

WE)

Hab

er-L

uggi

nca

pilla

ry

HBSSStirrer

Stirrer

pH-e

lect

rode

Cover

37∘C

CO2

CO2

CO2

inle

t


2


40 50 60 70 80 90

Inte

nsity

(au

)

120572-F

e (110

)

s-Fe 800∘C 2h 120572-F

e (200

)

120572-F

e (211

)

s-Fe 600∘C 2h

s-Fe 400∘C 2h

Cu (1

11)


00)

2120579 angle (∘)





As-deposited

2120583m

2120583m 4120583m

4120583m

⟨110⟩









119888

(V)














Aver

age g

rain

size

(120583m

)

4

3

2

1

0



Yiel

d str

engt

h (M

Pa)

700

600

500

400

300

200

100

0







0 5 10 15

s-Fe as-deposited

0

200

400

600

Stre

ss (M

Pa)

Strain ()




(a)

s-Fe as-deposited

0

200

400

600

Stre

ss (M

Pa)

0 5 10 15 20Strain ()




(b)


10120583m10120583m

(a)

3120583m

(b)



4 Conclusion




0 5 10 15 20 25 30 35 40 45 50 55 60

200

400



SS316L [3]

Fe35Mn [15]


UD-Fe annealed [20]


Ulti

mat

e ten

sile s

treng

thRp

(MPa

)






|j|

(A m

minus2)

10

1

01

001

1E minus 3

1E minus 4


s-Fe

as-d

epos

ited

s-Fe

800∘ C

2h

s-Fe

600

∘ C2

h

s-Fe

400

∘ C2

h


119888


isobserved







Acknowledgments


References






















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




pH-control-unit

pH 74

rese

rvoi

r

Potentiostat


Heat-bathRE

CE

Ther

moc

oupl

e

Sam

ple (

WE)

Hab

er-L

uggi

nca

pilla

ry

HBSSStirrer

Stirrer

pH-e

lect

rode

Cover

37∘C

CO2

CO2

CO2

inle

t


2


40 50 60 70 80 90

Inte

nsity

(au

)

120572-F

e (110

)

s-Fe 800∘C 2h 120572-F

e (200

)

120572-F

e (211

)

s-Fe 600∘C 2h

s-Fe 400∘C 2h

Cu (1

11)


00)

2120579 angle (∘)





As-deposited

2120583m

2120583m 4120583m

4120583m

⟨110⟩









119888

(V)














Aver

age g

rain

size

(120583m

)

4

3

2

1

0



Yiel

d str

engt

h (M

Pa)

700

600

500

400

300

200

100

0







0 5 10 15

s-Fe as-deposited

0

200

400

600

Stre

ss (M

Pa)

Strain ()




(a)

s-Fe as-deposited

0

200

400

600

Stre

ss (M

Pa)

0 5 10 15 20Strain ()




(b)


10120583m10120583m

(a)

3120583m

(b)



4 Conclusion




0 5 10 15 20 25 30 35 40 45 50 55 60

200

400



SS316L [3]

Fe35Mn [15]


UD-Fe annealed [20]


Ulti

mat

e ten

sile s

treng

thRp

(MPa

)






|j|

(A m

minus2)

10

1

01

001

1E minus 3

1E minus 4


s-Fe

as-d

epos

ited

s-Fe

800∘ C

2h

s-Fe

600

∘ C2

h

s-Fe

400

∘ C2

h


119888


isobserved







Acknowledgments


References






















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




As-deposited

2120583m

2120583m 4120583m

4120583m

⟨110⟩









119888

(V)














Aver

age g

rain

size

(120583m

)

4

3

2

1

0



Yiel

d str

engt

h (M

Pa)

700

600

500

400

300

200

100

0







0 5 10 15

s-Fe as-deposited

0

200

400

600

Stre

ss (M

Pa)

Strain ()




(a)

s-Fe as-deposited

0

200

400

600

Stre

ss (M

Pa)

0 5 10 15 20Strain ()




(b)


10120583m10120583m

(a)

3120583m

(b)



4 Conclusion




0 5 10 15 20 25 30 35 40 45 50 55 60

200

400



SS316L [3]

Fe35Mn [15]


UD-Fe annealed [20]


Ulti

mat

e ten

sile s

treng

thRp

(MPa

)






|j|

(A m

minus2)

10

1

01

001

1E minus 3

1E minus 4


s-Fe

as-d

epos

ited

s-Fe

800∘ C

2h

s-Fe

600

∘ C2

h

s-Fe

400

∘ C2

h


119888


isobserved







Acknowledgments


References






















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






119888

(V)














Aver

age g

rain

size

(120583m

)

4

3

2

1

0



Yiel

d str

engt

h (M

Pa)

700

600

500

400

300

200

100

0







0 5 10 15

s-Fe as-deposited

0

200

400

600

Stre

ss (M

Pa)

Strain ()




(a)

s-Fe as-deposited

0

200

400

600

Stre

ss (M

Pa)

0 5 10 15 20Strain ()




(b)


10120583m10120583m

(a)

3120583m

(b)



4 Conclusion




0 5 10 15 20 25 30 35 40 45 50 55 60

200

400



SS316L [3]

Fe35Mn [15]


UD-Fe annealed [20]


Ulti

mat

e ten

sile s

treng

thRp

(MPa

)






|j|

(A m

minus2)

10

1

01

001

1E minus 3

1E minus 4


s-Fe

as-d

epos

ited

s-Fe

800∘ C

2h

s-Fe

600

∘ C2

h

s-Fe

400

∘ C2

h


119888


isobserved







Acknowledgments


References






















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 5 10 15

s-Fe as-deposited

0

200

400

600

Stre

ss (M

Pa)

Strain ()




(a)

s-Fe as-deposited

0

200

400

600

Stre

ss (M

Pa)

0 5 10 15 20Strain ()




(b)


10120583m10120583m

(a)

3120583m

(b)



4 Conclusion




0 5 10 15 20 25 30 35 40 45 50 55 60

200

400



SS316L [3]

Fe35Mn [15]


UD-Fe annealed [20]


Ulti

mat

e ten

sile s

treng

thRp

(MPa

)






|j|

(A m

minus2)

10

1

01

001

1E minus 3

1E minus 4


s-Fe

as-d

epos

ited

s-Fe

800∘ C

2h

s-Fe

600

∘ C2

h

s-Fe

400

∘ C2

h


119888


isobserved







Acknowledgments


References






















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 5 10 15 20 25 30 35 40 45 50 55 60

200

400



SS316L [3]

Fe35Mn [15]


UD-Fe annealed [20]


Ulti

mat

e ten

sile s

treng

thRp

(MPa

)






|j|

(A m

minus2)

10

1

01

001

1E minus 3

1E minus 4


s-Fe

as-d

epos

ited

s-Fe

800∘ C

2h

s-Fe

600

∘ C2

h

s-Fe

400

∘ C2

h


119888


isobserved







Acknowledgments


References






















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Research Article Magnetron Sputtering a New ... - Hindawi

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Transcript of Research Article Magnetron Sputtering a New ... - Hindawi