碳化硅陶瓷纤维毡的制备与性能

碳化硅陶瓷纤维毡的制备与性能

1which等号同物联elinceraming,sicsicfi经营s西化学（sic）是第一阶段的一个缓慢移动的过程。它是一个缓慢移动的过程。cicfaff可以通过使用微标签来补偿预算。微标签，微标签，微标签，微标签，微标签，微标签，微标签，微标签，微标签，微标签，微标签，微标签，微标签，微标签，微标签，微标签，微标签，微标签。是的，这是促进发展的，而不是表面覆盖，这是非常常见的。这是基于预算。如果是正字母状微芯片，则是通过运动和睡眠的特征。子系列是基本的。它是混合的，不是表面和特征的。sup是al2o3、sia2、tia2和znofiber，还有区域边界效应。Recently,non-oxideceramicfibershavealsobeensynthesizedbyelectrospinningandpolymer-derivedceramictechniques.Eicketal.reportedSiCnanofiberswiththediametersof20nmbyeletrospinningpoly(carbomethylsilane)blendedwithpolystyreneandthenpyrolysis.Roseetducedcarbide-derivedcarbonfiberswiththespecificsurfaceareaupto3116m2/gbyelectrospinningpolycarbosilaneprecursors.Wilfertetal.preparedsiliconcarbonitridefibrousmatbyelectrospinning.Anetal.preparedsuper-hydrophobicsiliconcarbonitridefibrousmatsandceramicnano-compositefibers.Houetal.dem-onstratedthefabricationofmesoporousSiCfibers.Thesepreviousworkindicateaneffectivewaytomakenon-oxideceramicfibersinaflexibleandlow-costmanner.Theobjectiveofthisworkwastosynthesizesili-concarbidefibrousmatsbyelectrospinningpoly-carbosilanewithoutanyspinningassistants.Thethermal-mechanicalpropertiesandsimultaneousflexibilityandhydrophobicityofthesiliconcarbidefibrousmatswereanalyzedforthepromisingappli-cationsinharshenvironments.2u2004范围Apolycarbosilane(PCS)madebyapreviouslyreportedprocedurewasusedasaprecursor.ThePCShasamolecularmassof1500g/molandasofteningpointof200℃.Xylene,tetrahydrofu-ran(THF,AR,Aldrich)andN,N-dimethyl-formamide(DMF,AR,Aldrich)wereusedassol-vents.Thesecommercialmaterialswereusedas-receivedwithoutanyfurtherpurification.Forthesynthesisofthefibrousmats,thePCSwasfirstdissolvedinthemixtureofxylene,THFandDMFatavolumeratioof3∶1∶1toformasolu-tionof20%(massfraction)intheprecursor.Theobtainedsolutionwasthenelectrospunatarateof2.0mL/hatavoltageof20kV.Thespunfibrousnonwovenmatswerecollectedonagroundrollercollectorcoveredwithanaluminumfoilatawork-ingdistanceof10cm.Theresultantfibrousmatswerecarefullyremovedfromthecollectorfollowedbyvacuumdryingfor24htoremoveresidualsol-vent.ThedriedPCSfibrousmatswerecuredinairat200℃for3h,followedbypyrolyzinginahori-zontaltubefurnaceinhighpuritynitrogenatmos-phere.Thepyrolysiswerecarriedoutat500,800,1000,and1200℃for2hattheheatingrateof3℃/min.Thefibrousmatswerecharacterizedbyscanninge-lectronmicroscopy(SEM,modelLEO1530,LEOe-lectronCo.,Ltd,Oberkochen,Germany),transmis-sionelectronmicroscopy(TEM,modelJEM-2100HR,JEOLLtd,Tokyo,Japan),X-raydiffraction(XRD,PANalyticalX′PertPROdiffractometer,PANalyticalCo.,Almelo,theNetherlands)usingCuKαradiationandFouriertransform-infraredspectros-copy(FT-IR,modelAvatar360,USA).Thecompositionofthematswasanalyzedbyelectronprobemicroanalyzer(EPMA,modelJXA-8100,NECElectronicsCo.,Tokyo,Japan)inthewave-lengthdispersionmode.Contactanglesweremeas-uredusingacontactangleinstrument(modelJC2000Acontactangleanalyzer,ShanghaiAdvancedPhotoelectricTechnologyCo.,Ltd,Shanghai,China).WaterdropletsonthesurfaceofthematsweremonitoredbyaCCDcamera.Themechanicalpropertiesofthefibrousmatsweremeasuredusingatensiletester(modelSun2500,Galdabini,Italy)atacrossheadspeedof100mm/min.Standarddumbbellshapedtestsampleswerecutfromthefi-brousmats(75±1)mm×(150±2)mm(accord-ingtoISO9073-4-1997).Threespecimensweretestedforeachmat.3中国语境下的matsot特性Figure1(a)showstheSEMimagesoftheas-spunPCSfibrousmat.ItisseenthatthePCSfi-brousmatmakesthree-dimensionalstructureswithrandomlydistributedfiberorientations,whichistypicalforelectrospunfibers.Theimagealsore-vealsthatthefibersarestraightandhavesmoothsurfacesandanuniformdiameteralongtheentirefiber.However,differentfibershavedifferentdi-ameters.Figure1(b)showsthedistributionofthefiberdiametersmeasuredfrommorethan50fi-bers.Thediametervariedfrom1.5to2.9μmwithanaveragevalueof2.1μm.Figures1cand1eshowtheSEMimagesofthepyrolysedceramicfi-bermatsobtainedat1000and1200℃,respec-tively.Theresultantceramicfibersarealsostraightandhaveasmoothsurface.Pyrolysisdoesnotchangetheshapeofthefibers,butleadstothereductioninfiberdiameters.ThedistributionsoftheceramicfiberdiametersareshowninFigs.1(d)and1(f).Theaveragediameterforthefibersobtainedat1000and1200℃are1.4and1.1mm,respectively.ThedecreaseinthediameterisduetothemasslossanddensityincreaseassociatedwiththedecompositionofthePCS.Figure2showsatypicalEPMAspectrumob-tainedfromthematspyrolyzedat1000℃,exhibi-tingsomeintensivepeaksforSi,C,andO.ThecompositionwascalculatedfromtheEPMAspec-trumusingtheOxfordInstrumentsINCAsoftwarepackage(INCAEnergy200).Theresultrevealsthatthematpyrolysedat1000℃contains25.49%(inmolefraction,thesamebelow)Si,61.98%Cand11.67%O.Therelativelyhighox-ygenconcentrationislikelyduetotheresidualox-ygenfromtheair-curing.TheTGAstudyrevealedthatthereisnoobviousmasslossafter1000℃,suggestingthefibrousmatobtainedat1200℃shouldhaveasimilarcomposition.Figure3showstheFT-IRspectrafortheas-spunPCSmatandtheceramicmatpyrolysedat1000℃.Theas-spunPCSmatexhibitstheab-sorptionpeaksat2950and2900cm--1duetoC—Hstretching,2100cm--1duetoSi—Hstretching,1400cm--1duetoC—HdeformationinSi—CH3,1355cm--1duetoCH2deformationinSi—CH2—Si,1250cm--1duetoSi—CH3deformation,1020cm--1duetoCH2deformationinSi—CH2—Siandinthevicinityof800cm--1duetoSi—CH3deformationandSi—Cstretching.Also,theceramicfibrousmatsonlyexhibittwobroadpeaksat1065and816cm--1,whichcanbeattributedtotheoverlappingabsorptionofSi—O(1065cm--1)andSi—C(816cm--1).TheresultsindicatethatthePCSiscompletelytransformedintoinorganicceramicat1000℃.Figure4showstheXRDpatternoftheceramicfibrousmats.Itisseenthatthefibrousmatpyrol-ysedat1000℃showsanamorphouscharacterwithoutacleardiffractionpeak.However,thematpyrolysedat1200℃exhibitsthreediffractionpeakslocatedat36.5°,60.1°and73°,respectively.Thesepeakscanbeidentifiedasthe(111),(220)and(311)planesofβ-SiC.ThisresultisconsistentwiththeresultsobtainedinapreviousreportthatthePCS-derivedceramicscanbeconvertedintoin-organicphasescontainingSiCnanocrystals,freecarbonandtheoxycarbidephasewhenheat-treatedat1100--1200℃.Figure5showstheopticalimagesofthewaterdropletsonthematstoformtheobtusecontactan-gleswiththemats,indicatingthehydrophobicityofthesemats.Figure6showstheactualcontactangle.Itisseenthatregardlessofpyrolysisornot,allthefibrousmatshaveacontactangleof>130°,indicatingthattheyhaveagoodhydropho-bicity.Thematobtainedat1200℃hasacontactanglecloseto150°,suggestingthatitisalmostsu-perhydrophobic.Thehydrophobicityofthesur-facesofas-spunPCSfibrousmatscanbeattributedtothelowsurfaceenergyofthePCSduetotheC—Hgroups.Thehydrophobicityofthepyrol-ysedfibrousmatsislikelyduetothecombinationofhierarchicalmicro-andnanostructuresinherentinthefibrousmats.Figure7showstheopticalimagesoftheas-spunPCSfibrousmatandthepyrolysedceramicfibrousmatswrappedonstainlesssteelsticks.Bothmatscanbeeasilywrappedonthestickandtherearenoobviouscracksformedduringwrapping,demon-stratingthattheyareratherflexible.Itiswellknownthattheceramicfiberspreparedbymelt-spinningPCSareratherbrittle.Theflexibilityofthematscanbeattributedtotheirsmallfiberdi-ameter,thus,thestressconcentrationwasde-creasedsubstantially.Thebrittlehydrophobicfluorinatedceramicfibrousmatswerewidelyre-ported.However,thebrittlenessofceramicmatsrestrictedtheirpracticalapplications.Thece-ramicfibrousmatmadeinthisstudyhasthegoodflexibilityandhydrophobicity.Themechanicalbehaviorofthefibrousmatsde-pendsonthefiberstructureandtheinteractionbe-tweenthefibers.Figure8showsthetensilestress-straincurvemeasuredfortheceramicfibrousmatspyrolysedat1000℃.Thematshaveayieldstressof0.6MPaandelongationof45%atbreak.Thesevaluesaregreaterthanthoseofpolymerfibermatssuchas