简介:Theboundaryelementmethodwasimprovedforthe2Delasticcompositeswithrandomlydistributedinclusions.Thisproblemcanbereducedtoaboundaryintegralequationforamulti-connecteddomain.Further,consideringthematricesofthetractionsanddisplacementsforeachgroupoftheidenticalinclusionwerethesame,aneffectivecomputationalschemewasdesigned,sincetheordersoftheresultingmatrixequationscanbegreatlyreduced.Numericalexamplesindicatethatthisboundaryelementmethodschemeismoreeffectivethantheconventionalmulti-domainboundaryelementmethodforsuchaproblem.Thepresentschemecanbeusedtoinvestigatetheeffectivemechanicalpropertiesofthefiber-reinforcedcomposites.
简介:Coppercoatingwasdepositedonthesurfaceofaluminumboratewhiskerbyanelectrolessplatingmethod.Thismethodwasusedtomodifytheinterfacialpropertyofsqueeze-castingaluminumboratewhiskerreinforced6061Almatrixcomposite.Interfaceobservationindicatesthatthespinelreaction(MgAl2O4)ishinderedbythecoppercoating,andthedifferenceininterfacialreactiondegreeaffectsthetensilepropertyandagingbehaviorofthecomposite.Forthecompositewithlessspinelreaction(MgAl2O4),itspeak-agingprocessarepostponedduetolessdepletionofmagnesium.Onthefracturesurfaceofcopper-coatedcompositedimplesandfracturesofwhiskersaremore,butonthefracturesurfaceofuncoatedcompositepull-outofwhiskersaremorethanthatonthecoatedone.Inuncoatedcompositethefracturegenerallyoriginatesfromthenear-interface-region.
简介:HotcompressionbehaviorofTiC–Al2O3/AlcompositeswasstudiedusingtheGleeble-1500systematatemperaturerangeof300–550°Candatstrainraterangeof0.01–10.00s-1.TheassociatedstructuralchangeswerestudiedbyTEMobservations.Theresultsshowthatstressleveldecreaseswithdeformationtemperatureincreasingandstrainratedecreasing,whichcanberepresentedbyaZener–Hollomonparameterinanexponent-typeequationwithhotdeformationactivationenergyQof172.56kJ·mol-1.Dynamicrecoveryoccurseasilywhenstrainratesarelessthan10.00s-1.Dynamicrecrystallizationcanoccuratstrainrateof10.00s-1.
简介:ThepiezoelectriccompositescontaininghighlyorientedBaTiO3whiskersasactivephaseandPVDFasmatrixhavebeenpreparedbymicro-holeextrusionandorientationincarriedfibers.ThemorphologyoforientedBaTiO3whiskersandmicrostructureofthecompositeswereobservedbySEM.Asforitselectromechanicalproperties,itisfoundthatthedielectricconstant,piezoelectricconstantandremnantofpolarizationintheBaTiO3whisker-PVDFcompositeareconsiderablyhigherthanthatintheBaTiO3powders-PVDFcomposite,whilethelossfactorsfollowtheoppositetrend.FortheBaTiO3whisker-PVDFcomposite,thevaluesofε,d33andPrparalleltothewhiskerorientation(normalspecimen)aremuchhigherthanthatperpendiculartothewhiskerorientation(parallelspecimen).Thesignificanteffectsoftheconnectivepassagesofactivephaseonelectromechanicalpropertiesofthepiezoelectriccompositeshasalsobeeninvestigated.
简介:Toobtainthecompatiblematerialofhighhardnessandhightoughness,Hadfieldsteelmatrixcomposites,reinforcedbyhigh-Crcastironbarsmadeofflux-coredweldingwires,whichwereinsertedintotheHadfieldsteelmelt,wereinvestigated.Themechanicalpropertiesofthreematerials,ie,compositesforas-castandquenching-watercondition,aswellasHadfieldsteel,werecompared.Theresultsshowthatthealloypowderinsideflux-coredweldingwirescanbemeltedbytheheatcapacityofHadfieldsteelmeltandsolidifyintohigh-Crcastironbars.Theimpacttoughnessofthecompositeforquenching-waterconditionishigherthanthatofthecompositeforas-castconditionandislowerthanthatoftheHadfieldsteel,butitcanstillmeettherequirementsofhardnessandtoughnessinindustrialapplication.Regardlessofloadvariation,compositeforquenching-waterconditionshowsbetterwearresistancethanthoseofthecompositeforas-castconditionandHadfieldsteel.ThemodifiedfracturetoughnessandwearresistanceofcompositesareattributedtonotonlythecombiningactionsofHadfieldsteelmatrixandhigh-Crcastironbars,butalsotheeffectofheattreatment.
简介:在这个工作,flame-retardant聚丙烯(PP)/ramie纤维(RF)合成被准备。苎麻纤维被生产经由的包含磷、包含氮的火焰retardant(FR)化学上包在situ冷凝作用反应以便压制他们的烛蕊效果。红外线的光谱学(FTIR),X光检查光电子光谱学(XPS)和扫描电子显微镜学(SEM)表明了的Fourier变换苎麻纤维由FR(FR-RF)化学上包了,这成功地被获得。Thermogravimatric测试证明PP/FR-RF合成比PP/RF在高温度有更多的残余和更好热的稳定性合成。锥热量计(CC)结果显示热版本率(PHRR)和全部的热版本(THR)的山峰相应地与整洁的PP/RF的价值相比在23.4%和12.5%减少了。PP/FR-RF合成在燃烧以后创造了连续、紧缩的字符层。在有热传导系数的CC测试以后的字符残余的联合FTIR分析结果,RF上的FR的charring极大地削弱了RF的烛蕊效果,这能被结束,并且在RF域的更多的字符残余在整个燃烧地区便于更多的连续、紧缩的字符层的形成,因而在燃烧期间保护了PPcomposites,导致比PP/RF的合成的PP/FR-RF的更好的火焰retardancy合成。
简介:Inthisstudy,Almatrixcompositesreinforcedby7.5and15vol.%B4CparticlesandalsomonolithicAl(AlwithouttheB4Cparticles)wereproducedbywetattritionmillingandsubsequenthotforwardextrusionprocesses.Themicrostructureofthecomposites,evaluatedbyscanningelectronmicroscopy(SEM),showedthattheB4CparticleswereproperlydistributedintheAlmatrix.MechanicalpropertiesoftheAI/B4CcompositesandmonolithicAlwereinvestigatedbytensile,wearandhardnesstests.TheresultsrevealedthatwithincreasingcontentofB4Cparticles,thetensilestrengthandmicrohardnessofcompositesincreasedbuttheelongationdecreased.Inaddition,thetensilestrengthandmicrohardnessofcompositesampleswerehigherthanthoseofmonolithicAl.ThedensitymeasurementsrevealedthatthedensityofcompositesdecreasedwithincreasingcontentoftheB4Cparticles.
简介:Duetotheminiaturizationofmoderndevicesre-quirecomponentswithlightweight,highintegra-tionandtheabilitytostoreenergyinassmallvol-umeaspossible.Asaresult,energystoragedensitybecomesanimportantfigureofmeritforenergystor-agedevices.Inthispaper,firstly,wediscussedtheenergydensityinfine-grainedleadzirconatetita-nateglass-ceramicscompositewiththehelpofthe
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简介:Anovelin-situroutewasemployedtosynthesizeLiFePO4/carbon-nanofibers(CNFs)composites.Theroutecombinedhigh-temperaturesolidphasereactionwithchemicalvapordeposition(CVD)usingFe2O3andLiH2PO4astheprecursorsforLiFePO4growthandacetylene(C2H2)asthecarbonsourceforCNFsgrowth.ThecompositeswerecharacterizedbyX-raydiffraction(XRD),Brunauer-Emmett-Teller(BET)specificsurfacearea,fieldemissionscanningelectronmicroscopy(FE-SEM),andtransmissionelectronmicroscopy(TEM).Theelectrochemicalperformanceofthecompositeswasstudiedbygalvanostaticcyclingandcyclicvoltammetry(CV).Theresultsshowedthatthein-situCNFsgrowthcouldberealizedbythecatalyticeffectoftheFe2O3precursor.Thesampleafter80minCVDreactionshowedthebestelectrochemicalperformance,indicatingapromisingapplicationinhigh-powerLi-ionbatteries.
简介:ZrN-basedcompositesweresynthesizedfromzirconiaviaaluminothermicreductionandnitridationproceswithAlpowdersandMgOasthereductantandsinteringaids,respectively.ZrN-basedcompositesarepromisingforapplicationintherefractorymaterialsorotherhightemperatureindustryfields.TheeffectsofextraAlpowderonphysicalproperties,phasetransformationandmicrostructureswereinvestigated.ProductswithdifferenphasecompositionandmorphologieswereobtainedwithdifferentAlpowdersadditions.TheproductswerecomposedofZrN,ZrO_2,MgAl_2O_4,andZrAl_3O_3Nbyaluminothermalreductionandnitridationofzirconiawith0%extraAlpowdersaddition.ThediffractionpeaksoZrNwerethestrongestwhilepeaksofZrO_2vanishedwith6%extraAladdition.ThethermodynamiccalculationindicatedthatintroducingMgOintothesystemcouldpromotethereactionprocess.