4 Effect of the heat treatment on the structure and the properties of the electroless Co Fe B a.docx
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4 Effect of the heat treatment on the structure and the properties of the electroless Co Fe B a.docx
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4EffectoftheheattreatmentonthestructureandthepropertiesoftheelectrolessCoFeBa
JournalofAlloysandCompounds
Volume429,Issues1-2,21February2007,Pages99-103
doi:
10.1016/j.jallcom.2006.04.039 | HowtoCiteorLinkUsingDOI
Copyright©2006ElsevierB.V.Allrightsreserved.
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EffectoftheheattreatmentonthestructureandthepropertiesoftheelectrolessCo
Fe
Balloy
Sen-LinWang
a,
andLiang-LiangHonga
aDepartmentofAppliedChemistry,CollegeofMaterialsScienceandEngineering,HuaqiaoUniversity,Quanzhou362021,PRChina
Received19February2006;
revised14April2006;
accepted18April2006.
Availableonline5June2006.
Abstract
TheCo
Fe
Balloywaselectrolesslydepositedfromthesolutionusingpotassiumborohydride(KBH4)asareducingagentandethylenediamineasthestabilizer.ThecrystallizationbehaviorofthealloycoatingwasstudiedbyusingthedifferentialscanningcalorimetryandX-raydiffraction.Thestructureoftheas-plateddepositisamorphous.ThedepositwasconvertedintoCo3BandCoFephasesat464.9 °C.Theeffectoftheheattreatmentonthesurfacemorphology,themagneticpropertiesandthemicrohardnessoftheCo
Fe
Bdepositwereinvestigated.Asaresult,themicrohardnessandthemagneticperformancesofthedepositrisewiththeincreaseoftheheattreatmenttemperatureupto500 °C,thentheydecrease.Thedeposittreatedat500 °Cconsistsofnano-grains(thesizeofthegrainsisabout20 nm),andhasoptimalmagneticproperties.
Keywords:
Co
Fe
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
Fe
Bthinfilmsusingdimethylamineborane(DMAB)asareducingagent,whichhaveasaturationmagnetismvalueashighas1.6 T[6],[7]and[8];T.P.XuansimplyusedpotassiumborohydrideasreducingagenttoplatetheCo
Fe
Bthinfilms.BasedonT.P.Xuan'swork[9],wesubsequentlydevelopedaCo
Fe
Balloybathbytheadditionofpotassiumborohydrideasreducingagentandethylenediamineasstabilizer.Inthisstudy,theeffectofheattreatmentonthestructure,themicrohardness,thesurfacemorphologyandthemagneticpropertiesoftheCo
Fe
Balloywereinvestigated.
2.Experimentaldetails
TheCo
Fe
Balloywaselectrolesslydepositedfromthesolutioncontaining:
CoSO4·7H2O0.08 mol L−1,FeSO4·7H2O0.02 mol L−1,C4H4O6KNa·4H2O0.30 mol L−1,KBH40.059 mol L−1,NaOH0.50 mol 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
Fe
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.
ViewWithinArticle
Full-sizeimage(10K)
Fig.3. TheXRDpatternsofthedepositatvarioustemperaturesheattreatmentfor1 h.
ViewWithinArticle
Full-sizeimage(39K)
Fig.4. Theelectrondiffractionpatternoftheas-plateddeposit.
ViewWithinArticle
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.
ViewWithinArticle
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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