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1、CHAPTER2ProcessingofCarbonFibersIntroductionCarbonfibersarefabricatedfrompitchfibers,polymerfibers(e.g.,polyacrylonitrile),orcarbonaceousgases(e.g.,acetylene).Thosemadefrompitchandpolymerfibersarecommerciallyavailable,whereasthosemadefromcarbonaceousgasesarenotyetcommerciallyava
2、ilable.Thosemadefrompitchandpolymerfibersareinshortandcontinuousforms,whereasthosemadefromcarbonaceousgasesareintheshortformonly.Fibersmadefrompitchandcarbonaceousgasesaremoregraphitizablethanthosemadefrompolymers,sotheycanattainhigherthermalconductivityandlowerelectricalresisti
3、vity.Therawmaterialscostismuchlowerformakingfibersfrompitchorcarbonaceousgasesthanfrompolymers.However,thepresentmarketisdominatedbythosemadefrompolymersbecauseoftheircombinationofgoodmechanicalproperties(particularlytensilestrength)andreasonablecost.Incontrast,highlygraphiticpi
4、tch-basedcarbonfibersareveryexpensive,thoughtheyhavehightensilemodulus,highthermalconductivity,andlowelectricalresistivity.Ontheotherhand,thepriceofpitch-basedcarbonfibersisexpectedtodropwhentheproductionvolumeincreases.Eventually,theleastexpensivecarbonfibersareexpectedtobethos
5、emadefrompitchandcarbonaceousgases.Thefabricationofcarbonfibersfrompitchorpolymersinvolvespyrolysisofthepitchorpolymer;thisisperformedbyheating.Pyrolysisisakintocharring,thusformingcarbon.Incontrast,thefabricationofcarbonfibersfromcarbonaceousgasesinvolvescatalyticgrowthofcarbon
6、.Forthepyrolysisprocess,pitchhastheadvantageofhavingahighercarbonyieldthanpolymers.Thischapterdescribesthemethodsforfabricatingcarbonfibersfromallthreetypesofprecursors.Thechemicaltreatmentsandcoatingsneededtoenhancethebondingwithvariousmatricesincompositematerialsareaddressedin
7、thechaptersoncompositematerials.Ascarbonfibersaremostconvenientlyusedinawovenform,weavingisalsocoveredinthischapter.1314CARBONFIBERCOMPOSITESCarbonFibersmadefromPitchPitchusedasaprecursorforcarbonfiberscanbeapetra,;umpitch(suchasadistillationresidueobtainedbythedistillationofcru
8、deoilunderatmosphericorreducedpressure,oraheat-