简介:InordertoimprovethehydrogenstoragepropertiesofLiBH_4-MgH_2composite,twodifferentkindsofNb-basedcatalysts,NbCandNbF_5,wereaddedtoLiBH_4-MgH_2compositebyballmilling,andtheeffectofcatalystsonhydrogenstoragepropertiesofthemodifiedLiBH_4-MgH_2systemwasinvestigated.TheexperimentalresultsshowthatLiBH_4-MgH_2compositeisatwo-stepdehydrogenationprocess,andNb-basedcompoundscanremarkablyenhanceitsdehydrogenationkinetics.Forthecompositewithoutadditionofcatalysts,thestartingdecompositiontemperatureforthefirstdehydrogenationstepisaround320℃,andthereisalongperiodofincubationtime(around220min)fortheoccurrenceoftheseconddecompositionstepevenathightemperatureof450℃.Itneedsmorethan10htocompletethedecompositionprocessandreleasearound9wt%H_2.Afteradditionof5mol%NbF_5,thestartingdecompositiontemperatureforthefirstdehydrogenationstepisaround150℃,thereisnoincubationtimefortheseconddecompositionstep,andittakesaround40mintocompletethesecondstepandreachesatotaldehydrogenationcapacityof9.5wt%.NbF_5hasbettercatalyticeffectthanNbC.Basedonthehydrogenation/dehydrogenationbehaviorsandstructuralvariation,themechanismofcatalyticeffectwasdiscussed.
简介:CastingtitaniumalloyTC4(ZTC4)afterhotisostaticpressing(HIP)isoneofthepreferredmaterialsinthefieldofaerospacemanufacturing.Inthispaper,HIPZTC4afteralong-termthermalexposurewasinvestigated.Inordertoevaluatethevariationofmechanicalpropertieswithservicetime,thetensilepropertiesofthisalloyafterexposureat400°Cfor100,500,and1,000hwereinvestigated.Microstructureofsampleswasobservedbythemeansofopticalmicroscopy(OM),scanningelectronmicroscopy(SEM),andtransmissionelectronmicroscopy(TEM).Tensiletestwascarriedoutunderdifferenttesttemperaturesandfractureappearancewasstudied.Theresultsshowthatthestrengthincreaseswithexposuretimeduetothehardera2(Ti3Al)phaseprecipitatedintheaphaseandsuperficialoxygenlayerformed,whichresultsinthefactthattheresistanceofcrackpropagationcouldbeincreasedandcracksfirstinitiatebetweensurfaceoxidationandthematrix.Besides,thetensiletemperaturealsohasasignificanteffectonthemechanicalpropertiesofHIPZTC4.Theyieldstrengthandtensilestrengthdecreasewiththeincreaseoftensiletemperature,whilethetotalelongationincreases.
简介:Carbon-coatedlithiummanganesesilicate(Li2MnSiO4/C)nanoparticlesweresynthesizedbypolyolprocess.X-raydiffraction(XRD)patternsoftheobtainedmaterialsexhibitagoodfitwiththatoftheLi2MnSiO4phase.Fieldemissionscanningelectronmicroscopy(FESEM)imagesoftheobtainedsamplesshowthattheparticlesizeisonlytensofnanometers.Thehighresolutiontransmissionelectronmicroscopy(HRTEM)analysisshowsthattheLi2MnSiO4nanoparticlesaresurroundedbyaverythinfilmofamorphouscarbon.Thecompositepreparedthroughpolyolprocessshowsgoodperformanceascathodematerialsinlithiumcellsatroomtemperature.ThechargecapacityoftheLi2MnSiO4/Csamplesis219mAh/g(about1.3Li+perunitformulaextracted),andthedischargecapacityis132mAh/g(about0.8Li+perunitformulainserted)inthefirstcycleinthevoltagerangeof1.5-4.8V.Agoodcapacitycyclingmaintenanceof81.8%after10cycleswasobtained.
简介:Dynamicsinpartialtransientliquidphasebonding(PTLPbonding)ofSi3N4ceramicwithTi/Cu/Timulti-interlayerwassystematicallystudiedthroughmicro-analysisofjointinterfaces.Theresultsshowthatgrowthofreactionlayerandisothermalsolidificationprocessiondoatthesametime.GrowthofreactionlayerandmovingofisothermalsolidificationinterfaceobeytheparaboliclawgovernedbythediffusionofparticipatingelementsduringthePTLPbonding.Coordinationoftheabovetwodynamicsprocessisdonethroughtimeandtemperature.Whenreactionlayerthicknessissuitableandisothermalsolidificationprocessisfinished,thehighbondingstrengthatroomtemperatureandhightemperatureareobtained.
简介:石墨材料为一节所有钒氧化还原作用流动电池被用作电极,并且电极被转变修改提高它的电气化学的行为的金属性的离子。合成电极高有的一块多孔的石墨比表面区域和高电流密度。金属性的离子改进了的转变修改的电极能催化V的催化作用行为(Ⅱ)-V(Ⅴ)氧化还原作用反应由周期的voltammograms出现了。这篇文章由电气化学的阻抗光谱学(EIS)学习了修改电极的阻抗,并且同意电极由Co~(2+)和Mn~(2+)修改了,这比修改thenon的电极有一个更低的电嗬转移电阻。平均粒子尺寸分发的效果在Warburg阻抗的斜坡被大粒子尺寸分发减少的更低的频率。Co~(2+)的电压效率修改了电极测试房间是81.5%,它比修改thenon的电极的高。
简介:SphericalLiFePO4andLiFePO4/Ccompositepowdersforlithiumionbatteriesweresynthesizedbyanovelprocessingrouteofco-precipitationandsubsequentcalcinationsinanitrogenandhydrogenatmosphere.TheprecursorsofLiFePO4,LiFePO4/CcompositeandtheresultantproductswerecharacterizedbyX-raydiffraction(XRD),scanningelectronmicroscope(SEM),andtheelectrochemicalperformanceswereinvestigatedbygalvanostaticchargeanddischargetests.TheprecursorscomposedofamorphousFe3(PO4)2·xH2OandcrystallineLi3PO4obtainedintheco-precipitationprocessinghaveasphere-likemorphology.ThesphericalLiFePO4derivedfromthecalcinationsoftheprecursorat700℃for10hinareductionatmosphereshowsadischargecapacityof119mAh·g-1attheC/10rate,whiletheLiFePO4/Ccompositewith10wt.%carbonadditionexhibitsadischargecapacityof140mAh·g-1.TheelectrochemicalperformancesindicatethattheLiFePO4/CcompositehasahigherspecificcapacityandamorestablecyclingperformancethanthebareolivineLiFePO4duetothecarbonadditionenhancingtheelectronicconductivity.
简介:采用溶胶-凝胶法,添加不同比例的Li3PO4助熔剂,合成Li1.3Al0.3Ti1.7(PO4)3锂离子固体电解质烧结片,采用X射线衍射、扫描电子显微镜研究合成产物的结构与形貌,采用循环伏安及交流阻抗技术研究添加不同摩尔分数的Li1.3Al0.3Ti1.7(PO4)3固体电解质烧结片的结构、氧化-还原电位、离子电导率和活化能。结果表明:添加与未添加Li3PO4助熔剂的Li1.3Al0.3Ti1.7(PO4)3烧结片具有相似的X射线衍射结果。添加Li3PO4的Li1.3Al0.3Ti1.7(PO4)3烧结片的空隙率较小,更为致密。添加Li3PO4对Li1.3Al0.3Ti1.7(PO4)3的氧化-还原电位影响不大。在所有添加Li3PO4助熔剂的Li1.3Al0.3Ti1.7(PO4)3烧结片中,添加1%(摩尔分数)Li3PO4的烧结片具有最高的离子电导率6.15×10-4S/cm和最低的活化能0.3142eV。
简介:3.基板白边白角(接上期)3.4解决方法如上面所说,造成基板白边角的因素很多,所以要防止基板白边角的产生,需采取综合性的措施,才能收到较好的效果。其中以控制粘结片的树脂流动性,选择合适的层压菜单最为关键。3.4.1控制粘结片的树脂流动性与粘结片的流动性密切相关的技术参数有:粘结片的树脂流动度、粘结片的树脂凝
简介:微结构和电子横梁的机械描述焊接了伪造Ti-6Al-4V的关节被调查。Microhardness测试显示熔化地区(FZ)的坚硬比影响热的地区(HAZ)和贱金属的高。张力的结果证明焊接关节的机械性质以静态的力量与贱金属的那些是可比较的并且根据在微观结构和焊接关节的机械性质之间的关系。焊接的最终的张力的强度等于时漏关节的,它显示横向的FZ的纵的FZ和那些的机械性质是一样。基础材料,关节,和焊接标本的Macromechanical行为和macrofracture和microfracture被观察。在标本破裂现象的三种类型之中的比较揭示下列特殊差别:(1)破裂模式,(2)在中央区域的酒窝模式的显微图,并且(3)在中央区域和转变区域的酒窝的尺寸。