简介:Thesynthesisofprecursorofgreenphosphors,LaPO4:Ce,Tb,bymeansofco-precipitationwithcocurrentflowfeedwasstudied.Theeffectsofthereactiontemperature,thekindandconcentrationoftheacidinthebottomwater,andthechargingrateonthephysicalproperties,suchasparticlesize,wereinvestigated.Itisfoundthattheparticlesizeofthepowderiscontrollablebyadjustingacidityinbottomwaterandchargingrate.Thepowderwithdiametersizeof3to5μmwasobtained.ItsXRDandSEMwereanalyzed.XRDpatternsoftheas-preparedgreenphosphorpowdersdisplaythetypicalpeaksofCePO4.SEMshowsthatthemorphologyofpowdersisball-shaped.
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简介:利用粉末冶金方法研制了Sm(CobalFe0.24Cu0.08Zr0.027)7.0,Sm(CpbalFe0.27Cu0.05Zr0.027)7.0,Sm(CobalFe0.26Cu0.05Zr0.026)7.03种高温永磁,并对其磁性能、温度稳定性和显微结构进行了分析.结果表明:样品Sm(CobalFe0.27Cu0.05Zr0.027)7.0具有最高的内禀矫顽力(2165.6kA·m-1)和最大磁能积(212.0kA·m-3);3种磁体的温度系数都较低,最高使用温度均在400℃以上,大大高于一般商用磁体;增加Sm,Co,Cu的含量和减少Fe的含量可以提高材料的温度稳定性.X射线分析表明,合金中含有Sm2(Co,Fe)17主相,Sm(Co,Cu)5相,含Zr化合物等.Sm(Co,Cu)5相、单质Zr、晶粒边界等钉扎畴壁,使合金具有较高的矫顽力.
简介:InordertoimproveandstabilizethemagneticpropertiesofnanocompositeNd2Fe14B/α-Femagneticalloysbyacompositionaladjustment,smallamountofDyand/orCowasaddedtoNd9Fe84B7alloys.DTAanalysisontheamorphousofthealloystookplaceasthesoftmagneticphaseswerecrystallized,andthenthehardmagneticNd2Fe14Bwasprecipitatedfromthem.Whileα-Feandametastable1:7(TbCu7-type)phasewereformedsimultaneouslyinDyandCo-freealloys,theywerecrystallizedseparatelyatdifferenttemperaturesafterDyorCowasadded.ThisphaseseparationoccurredmoreclearlyintheDy-treatedalloysandtheothersoftmagneticphaseFe3BwasalsostabilizedbyDyand/orCo.The1:7phasethatwasstabilizedbyDyand/orCowasnoteliminatedat700℃,decreasingmagneticpropertiesofthealloys.Itwaseventuallydisappearedabove725℃,butFe3Bwasnoteliminatedevenat750℃whenDywasaddedmorethan0.5at%orCowasaddedmorethan2.0at%.AmountofNd2Fe14BinthealloystendedtoincreaseasDyadditionincreased,whereasCoadditiondidnotleadtoanyappreciablechangeintheratioofα-FeandNd2Fe14B.Moreover,DyadditionapparentlyincreasedcoercivityofanalloywhileCoadditionhadabeneficialeffectonremanence.ThegrainsintheDytreatedalloyswereusuallyfinerthanthoseintheCo-treatedalloys.Thegrainsizeofbothα-FeandNd2Fe14Binthealloysexhibitingmr≥0.72wasintherangeof20~40nmorevenlarger50nm,whichislargerthanthetheoreticaloptimumsize(~10nm).TypicalmagneticpropertiesobtainedfromaNd7.5Dy1.5Fe82.5Co1.5B7alloyannealedfor12minat725℃wereiHc=4.85kOe,Br=11.32kG,(BH)max=15.73MGOe,andmr=0.73.
简介:SinglephaseofBa1-xMgAl10O17:xEu2+(0.02≤x≤0.14)phosphorswasfirstsuccessfullypreparedbyco-precipitationinaqueousmediumwitha'reversestrike'method,usingoxalicacidandammoniatogetherasprecipitants.Completelycrystallizedphosphorswereobtainedat1300℃,whichis300℃lowerthanthetemperatureofsolid-statereaction.TheirphotoluminescencewasinvestigatedunderUVandVUVregion,respectively.TheemissionspectraofBa1-xMgAl10O17:xEu2+samplesexcitedby254or147nmshowedacharacteristicwidebandwiththepeakcentredatabout450~454nm.Optimumemissionintensityreachedatx=0.1andthenconcentrationquenchingoccurred.Thesynthesizedphosphorshows10%higheremissionintensitythanthatpreparedbysolid-statereaction.
简介:RE-dopedNi-basedcatalystswerepreparedbysol-gelmethod.ThesecatalystswereappliedtothereactionofCO2reformingCH4tosyngas.ThestudiesrevealthatRE-doped(RE=La,Ce,Sm,Yb)Ni-basedcatalystsshowhighercatalyticactivitythanundopedNi-basedcatalyst,andwiththeincreasingofRE-dopedquantity,thecatalyticactivityofcatalystsexhibitsregularchanges.WhenRE-dopedquantityis0.2%(molarratio),thecatalystsshowthebestcatalyticactivity.
简介:TheNd60Fe20Al8Co10B2alloywaspreparedbysuctioncastingofthemoltenalloyintoacoppermoldunderargonatmosphere.Themicro-structuralandmagneticpropertychangesintheNd60Fe20Al8Co10B2alloyduringcrystallizationwereinvestigatedbyX-raydiffraction(XRD),differentialscanningcalorimetry(DSC),scanningelectronmicroscope(SEM)andthevibratingsamplemagnetometer(VSM).TheprecipitationandNd-richandFe-richphaseshavenosignificanteffectontheintrinsiccoercitityforNd60Fe20Al8Co10B2alloyannealedbelow723K.However,thegrowthofFe-richphasedecreasesthesaturatemagnetizationandremanenceofthealloy.Thehardmagneticbehaviorisdisappearedwhenthealloyisfullycrystallized.