简介:为改善La-Mg-Ni系A2B7型合金的电化学贮氢性能,在合金中添加一定量的Si元素,通过真空熔炼及退火处理的方法制备La0.8Mg0.2Ni3.3Co0.2Six(x=0-0.2)电极合金。研究Si元素的添加对合金结构及电化学贮氢性能的影响。结果表明,铸态及退火态合金均为多相结构,分别为Ce2Ni7型的(La,Mg)2Ni7相和CaCu5型的LaNi5相以及少量的残余相LaNi3。Si元素的添加没有改变合金的主相,但使得合金中的(La,Mg)2Ni7相减少而LaNi5相增加。添加Si显著地影响了合金的电化学性能。随着Si含量的增加,铸态及退火态合金的放电容量逐步降低,但循环稳定性却随着Si含量的增加而增强。此外,合金电极的高倍率放电性能、极限电流密度、氢扩散系数以及电化学交流阻抗谱的测试均表明合金的电化学动力学性能随着Si含量的增加先增加而后减小。
简介:AWaveguideSwitchDesignUsingElectromagneticBandgapSubstrates;Abradingofbabbittmetalmouldwithhighefficiency;ChillcastingoflocomotivedieselIODIO0cylinderliners;Complexevaluationofmaterialsformetalmolds;CurvedSiliconElectronics;Developmentofcurvedholemachiningwithelectrochemicalmachining(lstreport)-processingmethodbyactuator-lesstool;DevelopmentofCurvedHoleProcessingTechniqueUsingElectrochemicalMachining(2ndReport)-Controllabilityofcurvatureofmachinedcurvedhole-
简介:InordertoobtainultrafineNd-Fe-Bpowder,aspray-driedprecursorwastreatedbyreduction-diffusion(R/D)process.And,unliketheconventionalR/Dprocess,calciumreductionthatisacrucialstepfortheformationofNd2Fe14BwasperformedwithoutconglomeratingtheprecursorwithCapowder.Byadoptingthismodifiedprocess,itispossibletosynthesizethehardmagneticNd2Fe14Batthereactiontemperatureaslowas850℃.TheaveragesizeofNd2Fe14Bparticlesthatareuniformlydistributedintheoptimallytreatedpowderwas<<1μm.MostNd2Fe14BparticleswereenclosedwiththinlayersofNd-richphase.TypicalmagneticpropertiesofsuchpowderwithouteliminatingimpurityCaOwereiHc=~5.9kOe,Br=~5.5kG,and(BH)max=~6MGOe.
简介:Widegapbrazing(WGB)experimentsusingthebuttedspecimenwitha1.5mmgapwerecarriedoutfortherepairofthefailedK418Bsuperalloylow-pressureturbinevanes.Thehightemperaturecreeprupturestrengthsofthebrazedjointsweretested,andthemicrostructuresandfracturesurfacesofthejointswereobserved.TheresultsshowthatthemicrostructureofK418Balloyjointiscomposedofdenseequiaxedgrain,smallanddiscretecompoundswithafewmicro-pores.Duringthecreeprupturetest,thecracksinitiatepreferentiallyatthemicro-poreorthegrainboundary,thenpropagatealongthegrainboundarytillthefracturehappens.Thecreeprupturestrengthat700℃ofthebrazedjointswith50%brazemetalintheworkingpartcouldexceed90%thatoftheK418Bsuperalloy,andthejointswith100%brazemetalintheworkingpartachieve70%to80%ofthecreeprupturestrengthsfortheK418Bbasemetal.