4 Effect of the heat treatment on the structure and the properties of the electroless Co Fe B aWord文件下载.docx
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4 Effect of the heat treatment on the structure and the properties of the electroless Co Fe B aWord文件下载.docx
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Balloy
Sen-LinWang
a,
andLiang-LiangHonga
aDepartmentofAppliedChemistry,CollegeofMaterialsScienceandEngineering,HuaqiaoUniversity,Quanzhou362021,PRChina
Received19February2006;
revised14April2006;
accepted18April2006.
Availableonline5June2006.
Abstract
TheCo
Balloywaselectrolesslydepositedfromthesolutionusingpotassiumborohydride(KBH4)asareducingagentandethylenediamineasthestabilizer.ThecrystallizationbehaviorofthealloycoatingwasstudiedbyusingthedifferentialscanningcalorimetryandX-raydiffraction.Thestructureoftheas-plateddepositisamorphous.ThedepositwasconvertedintoCo3BandCoFephasesat464.9
°
C.Theeffectoftheheattreatmentonthesurfacemorphology,themagneticpropertiesandthemicrohardnessoftheCo
Bdepositwereinvestigated.Asaresult,themicrohardnessandthemagneticperformancesofthedepositrisewiththeincreaseoftheheattreatmenttemperatureupto500
C,thentheydecrease.Thedeposittreatedat500
Cconsistsofnano-grains(thesizeofthegrainsisabout20
nm),andhasoptimalmagneticproperties.
Keywords:
Co
Balloy;
Heattreatment;
X-raydiffraction;
Magneticproperty
ArticleOutline
1.
Introduction
2.
Experimentaldetails
3.
Resultsanddiscussion
3.1.Thecompositionandthecrystallizationbehaviorofthedeposit
3.2.Theeffectofheattreatmentonthesurfacemorphologyofthedeposit
3.3.Theeffectofheattreatmentonthemagneticpropertiesofthecoating
3.4.Theeffectofheattreatmentonthemicrohardnessofthedeposit
4.
Summary
Acknowledgements
References
1.Introduction
Thesoftmagneticfilmsareusuallypreparedbyelectro-deposition.Forexample,theelectrodepositedCoFehashighsaturationmagnetism(MS)andlowcoercivity(HC),whichhasbeenreported[1]and[2].However,suchsoftmagneticfilmspreparedbytheelectroplatingmethodarenotuniforminthethicknessandcompositionbecauseoftheununiformityofthecurrentdensitydistribution.Theelectrolessplatingdoesnotsufferfromtheseproblems,andthusitshouldbemoresuitableforplatinguniformfilmsonsubstrateswithcomplexmorphologies.Uptodate,severalgroupshavereportedthepreparationofsoftmagneticthinfilmsbytheelectrolessdeposition[3],[4]and[5].Forexamples,T.Osaka'
sresearchgroupreportedtheelectrolessCo
Bthinfilmsusingdimethylamineborane(DMAB)asareducingagent,whichhaveasaturationmagnetismvalueashighas1.6
T[6],[7]and[8];
T.P.XuansimplyusedpotassiumborohydrideasreducingagenttoplatetheCo
Bthinfilms.BasedonT.P.Xuan'
swork[9],wesubsequentlydevelopedaCo
Balloybathbytheadditionofpotassiumborohydrideasreducingagentandethylenediamineasstabilizer.Inthisstudy,theeffectofheattreatmentonthestructure,themicrohardness,thesurfacemorphologyandthemagneticpropertiesoftheCo
Balloywereinvestigated.
2.Experimentaldetails
Balloywaselectrolesslydepositedfromthesolutioncontaining:
CoSO4·
7H2O0.08
mol
L−1,FeSO4·
7H2O0.02
L−1,C4H4O6KNa·
4H2O0.30
L−1,KBH40.059
L−1,NaOH0.50
L−1,C2H8N210.0
mL
L−1.Thetemperaturewaskeptat50
C.Theplatingtimewas2.5
h.Theloadcapacityoftheelectrolessplatingwas40
cm2
L−1.Thesubstratesweremechanicallypolishedandchemicallyetchedbeforetheexperiments.
Theheattreatmentexperimentsofthesampleinavacuum(0.67
Pa)werecarriedoutatvarioustemperaturesfor1.0
h.Thecompositionofthedepositwasdeterminedbyanenergy-dispersiveX-rayspectroscopy(EDX,ISIS-300,OxfordInstruments)attachedonascanningelectronmicroscope(SEM,LEO-1530).ThesurfacemorphologiesofthedepositwereobservedbytheSEM.ThestructureofthedepositwasstudiedbytheX-raydiffraction(XRD)onaRigakuD/max-RCdiffractometerwithamonochromatizedCuKαradiation,andwasalsomeasuredbytransmissionelectronmicroscope(TEM,JEM-100CXII).ThemicrohardnessmeasurementsweremeasuredbyusingaVickersmicrohardnesstesterunderaloadof100
g.Thethicknessofthesedepositswaskeptatthesamevalue,whicheliminatederrorsinthemeasuringofhardness.Thesamplesforabovemeasurementswereplatedonthecarbonsteelsubstrates,whichhas6.00
cm2surfacearea.Thecrystallizationtemperatureofthecoatingwasmeasuredbyadifferentialscanningcalorimeter(DSC-2960,TAInstruments)inanatmosphereofpureargongas.TopreparetheDSCspecimens,thealloywasdepositedonstainlesssteelsheet,andthenpeeledoffbyusingthemechanicalmethod.Themagneticmeasurementsweremadeusingavibratingsamplemagnetometer(VSM).Thesamplewasplatedonthecoppersubstratewhosesurfaceareaisabout0.25
cm2.
3.Resultsanddiscussion
3.1.Thecompositionandthecrystallizationbehaviorofthedeposit
Fig.1showstheEDXspectrumofthedeposit.Itisfoundthatthechemicalcompositionisalmostthesameinthedifferentzones,andthecoatingonlycontainstheCoandFeelements(EDXspectrumcannotdetectelementboron).Theatomicpercentageofthedepositiscalculatedas83.08%forcobalt,16.92%foriron,wherethecontentofboronisneglected.Theboroncontentinthedepositsisusuallybelow6.0
at.%,whichhasbeenmeasuredbyplasmaemissivespectrum[10].Fig.1alsodemonstratesthehighpurityofthecoating.
Full-sizeimage(4K)
Fig.1.
TheEDXspectrumofthedeposit.
ViewWithinArticle
Thedifferentialscanningcalorimetry(DSC)curvesofthecrystallizationprocessfortheCo
BcoatingatvariousheatingrateisillustratedinFig.2.TwoexothermicpeaksappearineachDSCcurve,andthepeakat450.0–480.0
Cisstrong,whilethepeakat200.0–210
Cisweak.Thestrongpeakmovestoahighertemperatureregionwiththeincreaseoftheheatingrate.Fig.3indicatesthattheXRDpatternsofthedepositafterheattreatmentfor1.0
hatvarioustemperatures.AccordingtotheXRDpatterns,thestrongDSCpeakobservedat450.0–480.0
CcorrespondstotheformationofCo3B(Pnma)andCoFe(Pm3m)phases,andthefirstweakpeakat200.0–210.0
CisascribedtotheevolutionofH2orthestructuralrelaxation.FromtheXRDpattern,itcanbefoundthattheas-plateddepositconsistsofanamorphousphase.Thecrystallizationpeaksat2θ
=
45.0°
and65.0°
areduetotheX-raydiffractionfromiron(Im3mphase)ofthesubstrate.Theelectrondiffractionpattern(Fig.4)ofthedepositedfilmalsosuggeststhatthestructureoftheas-plateddepositisamorphous.WhentheCo
Balloydepositwastreatedatabout500
C,thecrystallizationpeakswereobserved,whichisduetothecrystallizationoftheamorphousCo
BalloyintoCo3Bphase[11].
Full-sizeimage(44K)
Fig.2.
TheDSCcurvesofthecoating.
Full-sizeimage(10K)
Fig.3.
TheXRDpatternsofthedepositatvarioustemperaturesheattreatmentfor1
h.
Full-sizeimage(39K)
Fig.4.
Theelectrondiffractionpatternoftheas-plateddeposit.
3.2.Theeffectofheattreatmentonthesurfacemorphologyofthedeposit
Fig.5showsthesurfacemorphologiesofthedepositsofas-platedandheatedatdifferenttemperature.Theas-plateddepositconsistsofcompactparticleswiththediameterofabout20
nm,asshowninFig.5(a).Theboundaryamongtheparticlesissomeunclear.Afterheattreatmentat250
C,thecompactparticlesofthedepositincreaseto40
nm(Fig.5(b)).Furthermore,theparticlesofthedepositaftertreatedat250
Carerelativelyeven.Astheheattreatmenttemperatureincreasedto400
C,thesizeofcompactparticlesofthedepositinFig.5(c)becamenotasevenasthattreatedat250
C.Thediameterofcompactparticlesvariesfrom20to80
nm.Whenincreasingthetreatmenttemperature,theshapeofthecompactparticlesofthedepositdidnotchangeuntiltheheattreatmenttemperaturewascontrolledbelow400
C,whichindicatedthattheheattreatmentatthistemperatureregiondidnotproducenewphase.TheseSEMresultsagreewellwiththatoftheXRDmeasurements.Whentheheattreatmenttemperaturewasincreasedto500
C,manyfinegrains(about20
nm)wereformed,whichmaybeduetothetransformationoftheamorphousalloyphaseintothecrystallizedCo3BandCoFephases,asshowninFig.5(d).Inaword,theheattreatmenttemperatureaffectsthestructureofthedepositandthesizeofthegrains.
Full-sizeimage(282K)
Fig.5.
TheSEMphotosofthedepositafterheattreatmentatvarioustemperatures(°
C)for1
h:
(a)as-plated;
(b)250;
(c)400and(d)500.
3.3.Theeffectofheattreatmentonthemagneticpropertiesofthecoating
Themagnetichysteresiscurvesfortheas-platedandheat-treateddepositsatdifferenttemperatureareshowninFig.6.Thesaturationmagnetization(MS)(Ycoordinateaxisintercept)andthecoercivity(HC)(Xcoordinateaxisintercept)was,respectivelydeterminedfromFig.6,andtheresultswasillustratedinFig.7.ThesaturationmagnetizationofthedepositismorethanthatoftheCo
Bdeposit[6].Thesaturationmagnetizationandthecoercivityrosewiththeincreaseofheattreatmenttemperaturefrom50to450
C.Themaximumofthesaturationmagnetizationandthecoercivityr
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