简介:通过金相显微镜(OM)、扫描电镜(SEM)和动态热机械分析仪(DMAQ800)等分析手段研究粉末冶金法制备的Ti-47Al-2Cr-2Nb-0.2W(原子分数,%)合金微观组织对其阻尼性能的影响。研究结果表明:Ti-47Al-2Cr-2Nb-0.2W合金初始组织为近γ组织,其阻尼性能最差,在振幅为100μm时,损耗因子仅为0.007;在1330℃下保温15min空冷可获得细小全层片组织,层片晶团的平均尺寸约为200μm,其损耗因子在振幅为100μm时达到0.012。随温度升高或保温时间延长,层片尺寸和晶团尺寸明显增大,合金阻尼性能下降,保温120min时层片晶团的平均尺寸约为510μm,其损耗因子在振幅为100μm时为0.009。细小全层片的阻尼性能最好,而双态组织的阻尼性能介于近γ组织和细小全层片组织之间。
简介:采用电场、磁场、应力场和温度场多场耦合成形与烧结一体化技术制备高致密Fe-2Cu-2Ni-1Mo-0.8C合金,利用光学显微镜和扫描电镜对该合金的显微组织以及磨损表面进行观察和分析,重点研究耦合外加脉冲磁场对合金耐磨性能的影响。结果表明,在电场、应力场和温度场三场耦合放电等离子烧结技术的基础上进一步耦合适合的脉冲磁场,可明显改善烧结合金微观组织和合金元素分布的均匀性,不仅提高合金的耐磨性,同时还可显著提高合金的耐磨性能均匀性。在峰值电流、基值电流、频率、占空比分别为2700A、360A、50Hz和50%的脉冲电流以及烧结压力为30MPa的条件下烧结铁基合金粉末3min,耦合外加脉冲磁场强度为2.36×106A/m时,烧结材料的耐磨性能最佳,合金的磨损机制主要为粘着磨损。
简介:基于国外定向凝固氧化物/氧化物共晶复合陶瓷的晶体生长动力学行为的研究成果,阐述其动力学机制,分析动力学因素对微观结构形态的影响,探讨晶体生长热力学、动力学行为与微观结构形态之间的关系,同时结合以燃烧合成、快速凝固技术制备的新型高强韧A12O3/ZrO2(Y2O3)共晶复合陶瓷,探讨共晶复合陶瓷在快速凝固条件下的晶体生长动力学行为。结合定向凝固与快速凝固两种晶体生长机制,得知过冷度、凝固界面前沿的温度梯度是影响晶体生长方式的重要因素,且受二者决定的凝固速率(即晶体生长速率)则决定材料的最终微观结构与形态。
简介:混合氧化物(Ce0.6Zr0.4O2)由帮助微波的加热一起沉淀准备了的CeO2-ZrO2被用作支持经由早期湿的受精的方法与各种各样的CuO内容(0wt.%15wt.%)准备一系列CuO/Ce0.6Zr0.4O2催化剂。获得的CuO/Ce0.6Zr0.4O2样品被N2吸附,XRD,拉曼,TEM和H2-TPR技术,和他们的催化活动描绘因为公司氧化被调查。结果证明CuO/Ce0.6Zr0.4O2催化剂的活动被CuO的内容强烈影响,并且有10wt.%CuO的催化剂在公司氧化展出了最好的催化活动,它能在催化剂被归因于CuO,和高氧空缺集中的高分散和reducibility。
简介:Eu2+andDy3+codoped(Ca,Sr)7(SiO3)6Cl2yellowphosphorsweresuccessfullysynthesizedbyself-fluxmethod.Thestructure,morphologyandphotoluminescencepropertieswereinvestigatedbyX-raydiffraction(XRD),scanningelectronmicroscopy(SEM)andphotoluminescencespectra.Theas-preparedphosphorshowedabroademissionspectrumcenteredat550nmforEu2+single-dopedphosphor,whilelocatedat548–544nmfortheEu2+,Dy3+codopedsamplesunderexcitationat380nmlight.TheemissionintensitywasgreatlyimprovedwhenDy3+wasdopedintothe(Ca,Sr)7(SiO3)6Cl2:Eu2+system.Thecomposition-optimizedsamplewith3mol.%ofDy3+andconstant10mol.%ofEu2+exhibiteda220%PLenhancementcomparedtothephosphorwith10mol.%Eu2+single-doped.Meanwhile,itwasfoundthatthequantumefficiencyofphosphornamely(Ca,Sr)7(SiO3)6Cl2:3mol.%Dy3+,10mol.%Eu2+couldgetupto24.6%.Thesynthesizedyellow-emitting(Ca,Sr)7(SiO3)6Cl2:Dy3+,Eu2+isapromisingcandidateashigh-efficiencyyellowphosphorforNUV-excitedwhiteLEDs.
简介:DirectextractionofmetalsfromsolidswithcomplexingagentsinsupercriticalCO2(SC-CO2)hasrecentlyattractedinterestsinseparation,purification,recovery,andanalysisofmetals.Inthepresentstudy,thestatic/dynamicextractionofrareearthelements(Nd,Ce)fromtheiroxides(Nd2O3,CeO2)withorganophosphoruscomplexeswithHNO3andH2OinSC-CO2wasinvestigated.ThestaticextractionefficiencyofNdfromNd2O3withthetri-n-butylphosphate(TBP)-HNO3complexcouldreach95%underoptimizedexperiment...
简介:Steelmakingisenergyandmaterialintensive.Thatiswhysteelisalwaysdemonizedandconfrontedwithincriminationsandrequirementsforreductionofitsenvironmentalimpact.Thosepuredemands-likeforemissiontradingareshort-sightedastheydonotbaseonanintegratedapproach.InsteadtheymerelyconsiderCO2emissionsduringtheproductionprocess.Aforward-looking,globalclimateandenvironmentalpolicyneedsasustainablelifecycleapproach.Thereforeitmustforexamplealsotakeintoaccountthecontributionofsteeltowardscuttingemissionsinitsapplication-intheenergy.automotiveandhouseholdsectors.Steelwillplayakeyroleinclimateprotection.One-thirdoftheremainingCO2reductiontargetplannedinGermanyby2020canonlybeachievedwiththehelpofinnovativesteelproductsandtheirapplications.ThisistheconclusionofanindependentstudybyTheBostonConsultingGroup(BCG)onbehalfofSteelInstituteVDEh,andGermanSteelFederation.ThestudycomparesCO2savingsfromimportantinnovativesteelapplications(suchasmoreefficientpowerstations,windturbines,orlightervehicles)withCO2emissionscausedbysteelproduction.Byadoptingthiscomprehensiveperspective,thestudyforthefirsttimeprovidesaCO2balanceforthematerialsteelbycomparingtheCO2reductionsmadepossiblethroughinnovativesteelapplicationswiththeCO2emissionsresultingfromsteelproduction.ThebalancewascalculatedonthebasisofeightselectedinnovativesteelapplicationsinGermanyfortheperiod2007to2020,wherebytheCO2emissionscausedbysteelproductionwereconsideredthroughouttheentirelifecycleoftheparticularsteeluse.Fortheselectedexamples,theuseofinnovativesteelsresultedinatotalsavingspotentialof74MtofCO2in2020.Thecalculationsarebasedonconservativeassumptions;forexamplewithoutcountingofpotentialsbyexportedsteelorbycomparisonwithcompetitivematerials.TheproductionofsteelinGermany,includingtheextractiono