简介：Smallconcentrationsofahigh-molecular-weightpolymerhavebeenusedtocreateso-called'elasticturbulence'inamicro-scaleserpentinechannelgeometry.Itisknownthattheinteractionoflargeelasticstressescreatedbytheshearingmotionwithinthefluidflowwithstreamlinecurvatureoftheserpentinegeometryleadsinitiallytoapurely-elasticinstabilityandthenthegenerationofelasticturbulence.Weshowthatthiselasticturbulenceenhancestheheattransferatthemicro-scaleinthisgeometrybyupto300%undercreepingflowconditionsincomparisontothatachievedbytheequivalentNewtonianfluidflow.

简介：Anoveltwo-stagereductionprocessforsynthesisofultrafinenickelpowderwithahighpurityandlowdensityinafluidizedbedreactorhasbeendevelopedinthiswork.TherawultrafineNiOparticlesarefirstpre-reducedusinghydrogenatlowertemperatures(340-400℃),followedbyfurtherreductionathighertemperatures(500-600℃).Theself-agglomerationofNiparticlesformedduringlow-temperaturereductiondecreasesthesinteringactivityofthenewlyformedultrafineNiparticles,leadingtogoodfluidizationquality,evenforthesubsequenthigh-temperaturereductionprocess.TheagglomeratedNiparticleshaveahighNicontent(above99wt%),alowdensity(0.78g/cm~3)andauniformparticlesize(approximately100μm).Aconceptdesignforanoveltwo-stagefluidizedbedreactorprocessusedtoproducehigh-purityNipowderwasalsoproposed.Thisapproachmaybeextendedtothesynthesisofotherultrafine/nanosizedmetalsormetaloxidesthroughafluidizationmethod.