简介:有色金属的分类很多,大约有80多种,大致按其比重、价格、在地壳中的储量及分布情况和被人们发现与使用情况的早晚等分为五大类。(1)重有色金属;指比重大于4.5的有色金属。包括铜,镍,锢,铅,锌,锑,汞,镉和铋。(2)轻有色金属;指比重小于4.5的有色金属。包括铝,镁,钙、钾、锶和钡。(3)贵金属;指在地壳中含量少,开采和提取都比较困难,对氧和其它试剂稳定,价格比一般金属贵的有色金属。包括金、银。和铂族元素。一般比重都较大,熔点较高在916—3000度,有很好的化学稳定性、优良的抗氧化性及耐腐蚀性。(4)半金属;一般指硅、硒、碲、砷和硼五种元素。其物理化学性质介于金属和非金属之间。如砷是非金属,但它能传热和导电。
简介:Loadedonthecordierite,therareearthdopedcompositecatalystwaspreparedbysol-gelmethodcombinedwithdippingtechnique.TakingOrthodichlorobenzeneasmodel,thecatalystwasusedtoremovethedioxinsofthewastegas.Theresultsshowedthatat280℃andgasspacevelocitybeing8000h-1,theorthodichlorobenzenecouldberemovedeffectivilybythepreparedCeO2-TiO2-V2O5compositecatalystwhoseactivitywasremarkablyenhancedbythedopingofCe,whiletheindustrialside-streamtestofdioxinsfromrefuseincinerationsmokeindicatedthatthedecompositionratecouldreachabove93%underthesameconditions.
简介:Inthiswork,boththethermalexpansionandelectricalconductivityofnanocrystallineLa2Mo2O9werestudied.ThenanocrystallinepowderofLa2Mo2O9wasobtainedbysol-gelmethod,andwiththehelpofSHP(superhighpressure)upto4.5×104atmat700℃forashorttime,andthenanocrystallinepowderwasdensifiedwithoutobviousparticlesizegrowth.TheelectricalconductivityofnanocrystallineLa2Mo2O9wasoneorderofmagnitudelowerthanthatofthemicrocrystallinesampleatthesametemperature.Owingtothephasetransition,themicrocrystallineLa2Mo2O9hasanabruptincreaseofthermalexpansionwithapeakvalueof48×10-6K-1at556℃.Forthenanocrystallinematerial,thepeakvalueincreasesto112×10-6K-1at520℃.Ontheotherhand,above600℃thesignificantgrowthofparticlesizeofthenanocrystallineLa2Mo2O9wasobserved,accompanyingbyatremendousincreaseofthermalexpansionwithapeakvalueofthirdhigherthanthatofLa2Mo2O9.
简介:Basedonthethermodynamicallyself-consistentanalysisandoptimizationofthreesub-binarysystemsoftheternarysystemPrCl3-CaCl2-MgCl2,thethermodynamicsofthisternarysystemhasbeenstudied.UsingHillertmodelandtakingMgCl2asanasymmetriccomponent,thePrCl3-CaCl2-MgCl2phasediagramhasbeencalculated.Theagreementbetweencalculatedandmeasuredcompositionsandtemperaturesatdeflectingpointsonliquidusisgood.Thesystemisasimpleeutecticonewithaeutecticpointat26.0mol%PrCl3,41.5mol%CaCl2,32.5mol%MgCl2;560℃(calculated)and26.0mol%PrCl3,39.4mol%CaCl2,34.6mol%MgCl2;546℃(measured),respectively.
简介:TheZrO2-Al2O3ceramiccompositeswerepreparedbyappropriatetechniqueswithcommercialZrO2andAl2O3powdersasrawmaterialsandY2O3asstabilizer.TheresultsindicatethatwiththeintroductionofAl2O3intotheZrO2matrixwherethequantityofadditiveY2O3is3.5%(molefraction),thegrowthofZrO2grainsisefficientlyinhibited,whichhelpstheZrO2grainsexistinametastabletetragonalmanner;thushigherstrengthandtoughnessareacquired.Whenthecontentofaluminais20%(massfraction),thebendingstrengthandfracturetoughnessofthecompositesare676.7MPaand10MPa·m1/2respectively,themechanicalbehaviorsareclosetothosepreparedwithZrO2andAl2O3powderssynthesizedthroughwetchemicalapproach.Themechanicalbehaviorsofthecompositesarewellimprovedowingtothedispersiontougheningofaluminagrainsandphasetransformationtougheningofzirconiagrains.
简介:Differentrareearth(RE)ionsdopantswereaddedintotheSrAl2SiO7:Eu2+phosphorsinordertoenhancethephosphorescenceproperties,andtheeffectoftheREionsincludingYb3+,Ce3+,Nd3+,Dy3+andTm3+,wascomparativelyinvestigated.ItwasfoundthatNd3+additionimprovedthephosphorescencepropertiesobviouslyamongallthestudiedREions.Therefore,Sr1.96–xAl2SiO7:xEu2+,yNd3+phosphorswerestudiedindetail,andtheoptimumEu2+andNd3+concentrationsweredeterminedwiththeafterglowtimeofabout20min.Thephasestructures,photoluminescence(PL)properties,long-lastingphosphorescence(LLP)properties,afterglowdecaycurvesandthermo-luminescence(TL)fortheselectedphosphorsduringthecorrespondingstudywereinvestigated.AllthephosphorsexhibitedgreenPLemissionandLLPemission.ThereweretwoTLbandslocatedatabout325and380Kforthestudiedsamples,andtherelationshipbetweenREadditionandphosphorescencepropertieswasdiscussed.