第一次報告-張成智

報告人：張成智2015年4月10日不連續(xù)鍍鉻石墨纖維增強銅基復合材料的微觀結(jié)構(gòu)和熱力學性能的研究先碳中心學術報告會Microstructureandthermalpropertiesofcoppermatrixcompositesreinforcedbychromium-coateddiscontinuousgraphitefibers實驗213介紹結(jié)果與討論Contents第1頁目錄（Content）43結(jié)論前言（Foreword）第2頁粉末冶金（powdermetallurgy）PMprocess：powdermixture→compact（obtaingreencompact）→sintering（densification）

粉末冶金:是制取金屬粉末或用金屬粉末（或金屬粉末與非金屬粉末的混合物）作為原料，經(jīng)過成形和燒結(jié)，制造金屬材料、復合材料以及各種類型制品的工藝技術。一般球磨前言（Foreword）第3頁熱壓燒結(jié)：將干燥粉料充填入模型內(nèi)，再從單軸方向邊加壓邊加熱，使成型和燒結(jié)同時完成的一種燒結(jié)方法。優(yōu)點：熱壓燒結(jié)由于加熱加壓同時進行，粉料處于熱塑性狀態(tài)，有助于顆粒的接觸擴散、流動傳質(zhì)過程的進行，因而成型壓力僅為冷壓的1/10；還能降低燒結(jié)溫度，縮短燒結(jié)時間，從而抵制晶粒長大，得到晶粒細小、致密度高和機械、電學性能良好的產(chǎn)品。缺點：過程及設備復雜，生產(chǎn)控制要求嚴，模具材料要求高，能源消耗大，生產(chǎn)效率較低，生產(chǎn)成本高。熱壓燒結(jié)（hot-pressingsintering）2、介紹（Introduction）第4頁Materialsservingasheatsinksofsuchelectronicdevicesshouldhaveahighthermalconductivitytorapidlydissipateheatandalowcoefficientofthermalexpansion(CTE)toeffectivelyminimizethermalstresses.Combiningsuchgraphitefiberswithhighthermalconductivecopperinanappropriateway,itisexpectedtoobtainthegraphitefiber/Cucompositeswithhighthermalconductivity,lowCTE,goodmachinabilityandreasonablecost.粉末冶金可生產(chǎn)梯度散熱材料。散熱片材料(Materialsservingasheatsinks)3、實驗（Experiment）第5頁Inthepresentwork,suchmilledgraphitefibersarecompoundedwithCupowdersbyhot-pressingsintering.Inordertoimprovetheinterfacialbonding,chromium,acarbide-formingelement,iscoatedonthesurfaceofthesefibersthroughchemicalvapordeposition(CVD)technique.ThemicrostructureoftheresultantCr-coatedgraphitefiber/CucompositesareexaminedbyX-raydiffraction,scanning/transmissionelectronmicroscopes,andtheeffectsofarrangement,chromiummetallizationandcontentofthefiberonthethermalpropertiesintermsofthermalconductivityandCTEarediscussed.3.1實驗過程(Experiment)3、實驗（Experiment）第6頁3.2原料(Rawmaterials)Themilledformofmesophasepitch-basedgraphitefibers

(XN100type)usedinthisworkwaspurchasedfromNippon

GraphiteFiberCorporation.3、實驗（Experiment）第7頁3.2原料(Rawmaterials)TheCupowdersusedarethegas-atomized

sphericalCupowders,havingameanparticlesizeof14mmanda

purity>99.9%,suppliedbyGeneralResearchInstituteforNonferrousMetals,Beijing,China.3、實驗（Experiment）第8頁3.3石墨纖維的Cr金屬化(Chromiummetallizationofgraphitefibers)

CrCl3：providechromiumresource，CrH3：asreducingagent.graphitefibers：CrCl3：CrH3

ataweightratioof100：15：4.ThemixturewasplacedintoadepositionchamberofCVDapparatus.ThemainreactionincurrentCVDprocesscanbeexpressedas:CrCl3（g）+CrH3(s)→Cr(s)+3HCl(g)ThesegeneratedreactivegaseousCratomsdepositedonthesurfaceofthegraphitefibers,formingCrcoating.Theaverage

thicknessoftheCrcoatingonthefibersisabout150nm(SEM圖)3、實驗（Experiment）第9頁3.4復合材料的合成(Consolidationofcomposites)TheCupowderswithvaryingcontentsofCr-coatedgraphite-fibers(35,40,45,50and55vol%)weredrymixedatroomtemperaturebyusinga3-Dvibratorymillfor8hwithrotaryspeedof

2500rpm.Vacuumhot-pressingsinteringsystem(ModelHighMulti5000,FujidempaKogyoCo.Ltd.,Japan)wasusedtosynthesizetheCr-coatedgraphitefiber/Cucomposites.Asheetofgraphitefeltwasplacedbetweenthe

punchandthepowdersaswellasbetweenthedieandthepowders

foreasyremoval.3、實驗（Experiment）第10頁3.5復合材料的性能(Characterization)

Bulkdensity：thewater

immersionmethodbasedonArchimedes'lawandcomparedwiththe

theoreticaldensity.Themorphologyandfracturesurface：LEO-1450SEM.

Thephases：X-raydiffraction(XRD)conductedon

SiemensD5000diffractometerusingCuKaradiation.

Interfacearea

：LEOJSM-7001Ffieldemission

(FE)-SEMandJEM-2100transmissionelectronmicroscopy(TEM).3、實驗（Experiment）第11頁3.5復合材料的性能(Characterization)

λ=ραСThermalconductivityλCompositedensityρ：water

immersionmethodThermaldiffusivityα：differentialscanningcalorimetryHeatcapacity

C：alaserflashapparatusCoefficientofthermalexpansion(CTE)：PerkineElmerTMA7dilatometerintemperaturerange20-2500C.

4、結(jié)果與討論（Resultsanddiscussion）第12頁4.1復合材料的微觀結(jié)構(gòu)(Microstructureofthecomposites)Densitymeasurementsshowapost-sinteringdensificationof>96.5%

Fig.2ThegraphitefibersarehomogeneouslydistributedintheCumatrix.Thereisalmostnospecificdegradationofthefibers,separated

interfaces,orevidentporescanbeobserved.Moreover,thedensificationprocessleadstoapreferentialorientationofthefibersin

theplane(X-Y)perpendiculartothepressingdirection(Z).Theirpropertieswillbehighly

anisotropic.4、結(jié)果與討論（Resultsanddiscussion）第12頁4.1復合材料的微觀結(jié)構(gòu)(Microstructureofthecomposites)4、結(jié)果與討論（Resultsanddiscussion）第13頁4.1復合材料的微觀結(jié)構(gòu)(Microstructureofthecomposites)Fig.4(a)presentsFE-SEMmicrographoftheinterfaceareaob-tainedfromthecompositewith50vol%fibers.Acontinuousinterlayerofacontrast(darkgray)differentfromthoseofgraphitefiber(blackgray)andCumatrix(lightgray),about130nmthickon

theaverage,isclearlyvisibleinthesecondelectron(SE)mode.

CombinedtheresultsfromXRDanalysis,itcanbeverifiedthatthis

interlayeristhechromiumcarbidelayer.4、結(jié)果與討論（Resultsanddiscussion）第14頁4.1復合材料的微觀結(jié)構(gòu)(Microstructureofthecomposites)Atthisscaleofobservation,theoverallmorphologyofthisinterfaceregionexhibitsaneat

profile,wherethethinanduniformCr3C2

interlayeristightly

adheredtoboththefiberandCumatrix.Moreover,thedetailed

observationoftheCr3C2/graphitefiberinterfacewasdeterminedby

TEMinFig.4(b)

4、結(jié)果與討論（Resultsanddiscussion）第15頁4.2纖維排列對熱力學性能的影響(Effectofberarrangementonthermalproperties)Obviously,suchplanararrangementofthefibersmakes

theaxialhighthermalconductivityandlowCTEofthefibershavea

muchhigherdegreeofutilizationintheX-Ydirectionthanthatin

theZdirectionofthecomposites.4、結(jié)果與討論（Resultsanddiscussion）第16頁4.3纖維Cr金屬化對熱力學性能的影響(Effectoffiberchromiummetallizationonthermalproperties)Fig.5presentstheTEM

micrographoftheinterfaceoftheuncoatedcomposite.theadhesionbetweengraphitefiberandCumatrixisvery

weak,becausesomenano-sizedinterfacialgapsareoftenobserved.

AccordingtotheC/Cuphasediagram,theCsolubilityinCuis

negligible.copperisknowntobechemicallyinertwith

respecttocarbon.Thechemicalincompatibilityofcarbonand

coppercanresultinaweakmechanicalinterfacialbondingbetweengraphiteberandCumatrix,thereforetoseverelyreduce

thethermalconductivityoftheuncoatedcomposite.4、結(jié)果與討論（Resultsanddiscussion）第17頁4.3纖維Cr金屬化對熱力學性能的影響(Effectoffiberchromiummetallizationonthermalproperties)Animproved

interfacialadhesion,bycontrast,wasobtainedduetotheformation

ofacontinuousCr3C2

interlayer，buttheCr3C2

itselfhasaverylowthermalconductivity.whichismuchlowerthanthatofthegraphitefiberorcopper,soUnderthepremiseofensuringtheabilitytoformagoodcombinationbetweengraphitefiberandCumatrix,thethicknessofthelayershouldbeassmallaspossible.Nevertheless,theoptimumthicknessforthelayerorthepriorCrcoatingneedstobefurtherstudiedinthefollowingwork.4、結(jié)果與討論（Resultsanddiscussion）第18頁4.3纖維Cr金屬化對熱力學性能的影響(Effectoffiberchromiummetallizationonthermalproperties)Alarge

numberofstudiesaboutthethermalexpansionbehaviorsofcompositeshaveshownthattheCTEsofcompositesarenotonlydeterminedbythethermalexpansionsofreinforcementandmatrixthemselves,butalsobytherestrictionofreinforcementtothe

thermalexpansionofmatrixthroughinterfaces.Fig.6

givestheSEMfractureimagesofthebothuncoatedandCr-coatedcompositeswith50vol%bers.Thefracturesurfacesare

paralleltoZdirection.4、結(jié)果與討論（Resultsanddiscussion）第19頁4.3纖維Cr金屬化對熱力學性能的影響(Effectoffiberchromiummetallizationonthermalproperties)Fromtheabovediscussions,itcanbeconcludedthatusing

chromiummetalizedgraphitefiber,theformedinterlayer

withastrongadhesionforcewiththefiberandcoppercausedthe

interfacestructureofthegraphitefiber/Cucompositetochange

frommechanicalbondingintometallurgicalbonding,thustheheat

andloadtransferabilitiesbetweenthefiberandCumatrixcanbeimproved,whichareeffectiveforenhancingthermalconductivityandreducingCTEofthecomposites.4、結(jié)果與討論（Resultsanddiscussion）第20頁4.4纖維含量對熱力學性能的影響(Effectoffibercontentonthermalroperties)whenthefiber

contentexceeds50vol%,thethermalconductivityofthecomposite

begantodeclineanddifficultiestothedensification.Thiscanbeattributedtothedecreaseddensities

ofthecomposites.Asweallknow,poresareharmfultothethermal

conductivity.Thisisprobablydueto