简介:煤气的金属弧焊(GMAW)的数字模型正在试着联合液体(VoF)的弧和体积的magnetohydrodynamics(MHD)模型的电流金属转移当模特儿。他们忽视蒸发并且为弧区域假定氩气氛,因为它是为煤气的钨弧焊的模型的普通实践。这些模型在20000K和类似于钨的温度分布上面预言温度惰性的气体(TIG)弧。然而,在GMAW弧的当前的分光镜的温度大小表明低得多的弧温度。与TIG弧相对照,他们发现了光线的温度分发的中央本地最小。纸论述考虑金属蒸汽的一个GMAW弧模型并且它在与试验性地观察的温度的一个很好的协议。而且,模型能第一次在光线的温度和光线的电流密度分布预言本地中央最小。向轴的方向焊接火炬,工作片,电线和弧(液体领域)的对称的模型象在氩的狂暴的混合和金属蒸汽的热demixing一样实现MHD。从模拟获得的铁蒸汽的集体部分在2000~5000K在弧的穗上在弧核心和另一累积显示出累积。demixing效果导致在这二个区域之间的铁的很低的集中。敏感分析证明运输的影响和金属蒸汽的放射性质喂。最后模型预言与Zieliska等的测量结果相比。
简介:MoleculardynamicssimulationusingauniversalforcefieldhasbeenemployedtodeterminethediffusioncoefficientsofO2andNa2SO4vaporintoB2O3andSiCfrom700Kto1273K,respectively.Einsteindiffusionwasobservedina250~300pssimulation.ThediffusioncoefficientfortheO2rangefromabout9.279×10-9cm2/sforB2O3to2.275×10-10cm2/sforSiCataloadingof32moleculespersimulationbox,thatfortheNa2SO4vaporrangefromabout9.888×10-7cm2/sforB2O3to1.837×10-10cm2/sforSiCataloadingof8moleculespersimulationbox.EnvironmentpropertiesofC/SiCcompositewillbeincreasedviatheB2O3preventingthediffusionofO2andNa2SO4vaporintothepyrolyticinterphaseandcarbonfibers.
简介:Znbasedmetalshaveexhibitedpromisingprospectsasastructuralmaterialforbiodegradableapplications.PureZnporousscaffoldswereproducedbylaserpowderbedfusion(LPBF)basedondatafilesofdesigningandCTseanning.MassiveZnevaporationduringlasermeltinglargelyinfluencedtheformationqualityduringLPBFofZnmetal.Themetalvaporinprocessingchamberwasblownoffandsuctionedoutefficientlybyanoptimizedgascirculationsystem.Numericalanalysiswasusedtodesignandtestifytheperformanceofgasflow.Thesurfaceofscaffoldswascoveredwithnumerousparticlesindifferentsizes.Processingporesoccurredneartheoutlinecontourofstruts.Theaveragegrainsizeinwidthwas8.5μm,andthehardnesswas43.8HV.Chemicalpluselectrochemicalpolishingobtainedunifonnandsmoothsurfacewithoutprocessingpores,butthediameterofstrutsreducedto250μmfromthedesignvalue300μm.Thepoorsurfacequalityandprocessingporeswereresultedbythesplashingparticlesincludedspattersandpowdersduetotherecoilforceofevaporation,andthehorizontalmovementofliquidmetalduetooverheatingandwetting.TheinsufficientmeltingattheoutlinecontourcombinedwithgoodwettingofZnliquidmetalfurtherincreasedthesurfaceroughnessandprocessingpores.
简介:AhypereutecticAl-Sialloypowderwaspreparedbyultrasonicgasatomizationprocess.Themorphologies,microstructureandphaseconstituentofthealloypowderwerestudied.TheresultsshowedthatpowderofthealloywasveryfineanditsrnicrostructurewasmainlyconsistedofSicrystalsplusintermetalliccompoundAl9FeSi3,whichwere.veryfineanduniformlydistributed.
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简介:Anumberoftechniqueshavebeendevelopedtosynthesizenanocrystallinebulkmaterials,includinginert-gascondensationandconsolidation,electrodeposition,severeplasticdeformation,crystallizationofamorphoussolid,surfacemechanicalattrition,andpowdermetallurgy.However,itishardtoproducethebulkwithcontrollablenanostructures,especiallywiththegrainsizescontrollableinawiderangebelow100nm.Intheconventionalpowdermetallurgy,duetothefactthatrapidcoarseningoftheparticles...
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简介:用organo听Sn(OC4H9)4作为先锋,钠dodecylsulfonate(SDS)和SDS明胶(SDS-G)象模板复杂,二听二氧化物胶体的粒子被准备由一自己组装方法。两个SnO2产品分别地与SDS-G与SDS和SnO2-C粒子被标记SnO2-B粒子,它在制作相应于SnO2-B和SnO2-C传感器的SnO2煤气的传感器被使用。X光检查衍射(XRD),扫描电子显微镜学(SEM),传播电子显微镜学(TEM)和thermogravimetry和不同热分析(TG/DTA)被用于描述。试验性的结果证明SnO2-B胶体的粒子由mesoporous组成像片的粒子,当SnO2-C粒子主要由球形的粒子组成时。煤气的察觉到大小证明那个SnO2-B传感器执行察觉到反应到所有目标气体的最好,包括H2,C2H5OH和液体石油气体(LPG)。特别地,SnO2-B传感器的察觉到的反应在1000潩獮的集中在H2空气在32点被完成
简介:Thenon-isothermalcrystallizationkineticsofpolyamide6/diamine-modifiedmulti-walledcarbonnanotube(PA6/D-MWNT)nanocompositewasinvestigatedbydifferentialscanningcalorimetry(DSC).ThemodifiedAvramiequation,theOzawaequationandthecombinedAvrami/Ozawaequationwereemployedtoanalyzethenon-isothermalcrystallizationdata.ThecrystallizationactivationenergieswerealsoevaluatedbytheKissingermethod.ItwasfoundthatthecombinedAvrami/Ozawaequationcouldsuccessfullydescribethenon-isothermalcrystallizationprocess.TheresultsshowedthatD-MWNTsnotonlyactedaseffectivehetero-geneousnucleatingagentsforPA6andnoticeablyincreasedthecrystallizationtemperatureofPA6,butalsoinfluencedthemechanismofnucleationandcrystalgrowthofPA6andthenreducedtheoverallcrystallizationrateoftheneatPA6matrix.ThecrystallizationactivationenergyforthenanocompositesamplewasgreaterthanthatoftheneatPA6,whichindicatedthattheadditionofD-MWNTshinderedthemobilityofPA6chainsegments.