简介：PositronannihilationbehaviorshavebeenstudiedinthesinglephaseNd2Fe14BmagnetandthenanocompositeNd2Fe14B/α-Femagnet,preparedbymeltspinning.Theresultsshowedthatthenumberofvacancy-clusteratgrainboundariesincreaseswithincreasingannealingtemperatureforthebothtypesofmagnets.Theincreaseofthiskindofdefectcanimprovethecoercivityof

简介：Magnetizationanddemagnetizationcurvesandhysteresisloopsapplieddifferentmagnetizing.fieldsinsinteredNd-Fe-BandNd-Dy-Fe-Bmagnetsfromthermallydemagnetizedanddcfield-demagnetizedstateswereinvestigatedattemperaturesofupto150℃.Thefirst-quadrantremagnetizationcurvesandthecurvesofcoerciveforces_MH_CversusrernagnetizingfietdsH_mfromdcfield-demagnetizedstateatroomtemperatureshowasteparoundmagnetizingfieldasabsolutevalueofthemaximumintrinsiccoercivity.Thestepsof_MH_C-H_mcurvesshiftedtolowerremagnetizingfieldsandtheshapesofmagnetizationcurveschangedfromsteptypetoprecipitoustypewhentemperaturewentupto100～150℃orafterthespecimenwasthermallydemagnetizedatatemperaturehigherthantheCurietemperature.Thesteepriseofkneecoereivitywithincreasingmagnetizingfieldisbehindthatof_MH_C.NotethatthemagnetichardeninginsinteredNd-Fe-Bmagnetsiscontrolledbypinningofdomainwalls.

简介：FenanowirearraywithstrongshapeanisotropywasemployedasthesoftphaseinNd-Fe-Bbasednanocomposites.TheeffectsoftheFenanowiredistributiononmagneticpropertiesofthenanocompositeswereinvestigatedbymicromagneticsimulation.TheresultsindicatethattheshapeanisotropyofFewiresaddedinthesamedirectionastheuniaxialmagnetocrystallineanisotropyofthehardphasecannotincreasethecoercivityofthenanocomposite.Whenthenanowiresaredistributedperpendiculartotheeasyaxisofthehardphase,theshapeanisotropyofsoftphasecanretardthemomentsfromrotatingtothefullreverseddirection,leadingtoenhancedcoercivity.Inaddition,withincreasingthenanowirediameter,thecoercivityofthenanocompositedecreases,butthedipolarinteractionshowsdifferentrolesinmagneticreversalofnanocompositefordifferentdistributionsofnanowires.ThecurrentresultssuggestthatthecoercivityoftheNd2Fe14B/α-Fenanocompositecanbeenhancedbyintroducingthesoftmagneticnanowirearraywiththediameterlessthantheexchangelengthandwiththelongaxisalongthedirectionotherthantheeasyaxisofhardphase.

简介：1.IntroductionSofarthemicrostructureandcoercivityofSm（Co,Cu,Fe,Zr）7.4alloyhavebeenstudiedindetailbyvariousauthors.TheeffectofZr-richlaminarphasestructureonthehighcoecivityofalloyismoreattractive.Thechangesofmagnetic

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：TheCurietemperatureof(Nd1-xPrx)2Fe14CoyBcompounds（x=0,0.2,…,1.0andy=O,2,4,6,14）hasbeendeterminedwithACinitialsusceptibilitymeasurement.ItwasfoundthatthevariationsofCurietempera-turewithxisnotlinearfory=0and14,whereasitislinearforothervaluesofy.Thelatticeconstantsof(Nd1-xPrx)2Fet14BweredeterminedbyusingX-raydiffraction.Thelatticeexpansionwasmostlyalongthecaxis,whereasthatalongthea-axisremainedpracticallyzeroforthewholeseries.ItissuggestedthatPratomsmayshowsitepreferenceinR2M14Bcompounds（M=FeorCo）.DuetothesubstitutionofCoforFe.thetendencyofsitepreferenceofPrbecomeslesspronounced,whichmaybeattributedtothedecreaseofdiffer-enceofcrystalelectricfield（CEF）actingonthetworareearthsiteswiththeintroductionofCoorFe.Incon-trasttothatofthePratoms,thesitepreferenceofCoiu（Nd（1-x）Prx）2Fe（14-y）CoyBcompoundsdoesnotdependonthecompositionoftherareearthsublattice（R=NdorPr）.

简介：

简介：为stoichiometric作文的nanocrystallineNd-Fe-B磁铁的demangetization曲线被使用微磁力的有限元素技术计算。曲线，特别iHc随N.The很小的iHc的增加变得更小从一系列沿着不同的地方向的曲线为N=∞接近那。iHc随L的增加增加，并且是什么的靠近的cr一些比小试验性的价值应该是。

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：ThecoercivitymechanismofNd-Fe-Bbasedmagnetspreparedbyanewtechniqueofstripcastingwasinvestigated.Differentfromthetraditionalmagnets,α-FephasesaredifficulttobefoundinNd-Fe-Bmagnetspreparedbystripcasting.Meanwhile,therich-Ndphasesoccurnotonlynearthegrainboundariesofmainphases,butalsowithinthemain-phasegrains.Investigationonthemagnetizingfielddependenceofthecoercivityforthe(Nd0.935Dy0.065)14.5Fe79.4B6.1magnetandthetemperaturedependenceofthecoercivityfortheNd14.5Fe79.4B6.1magnethavebeendone.Resultsshowthatcoercivitiesforstripcastingmagnetsarecontrolledbythenucleationmechanism.

简介：EffectsofNbandZrsubstitutionsonthecrystal]izationbehaviorsandmagneticpropertiesofmelt-spun(Nd,Pr)2Fe14B/α-Fealloyswerestudied.Theresultsshowthatfor(Nd0.4Pr0.6)8.5Fe85.5B6ribbons,themetastable(Nd,Pr)3Fe62B14precipitatesaftertheinitialcrystallizationofα-Feanddecomposesintothefinalmixtureof(Nd,Pr)2Fe14Bandα-Fe.For(Nd0.4Pr0.6)8.5Fe84.5Zr0.5Nb0.5B6ribbons,however,(Nd,Pr)2Fe14Bandα-Fephasesprecipitatesimultaneously.ThisindicatesthatbothNbandZrdopingcanavoidtheformationofmetastablephaseand!

简介：EnvironmentalfriendlyrecyclingprocessforNd-Fe-Bsinteredmagnetsludgesgeneratedinthemanufacturingprocess,whichcontainlargeamountofrareearth,includingNd,PrandDy,isbadlyneededsofar.Inpresentstudy,wehavedevelopedaneffectiveroutetoobtainrecycledsinteredmagnetsfromNd-Fe-Bsinteredmagnetsludgesbycalciumreduction-diffusion（RD）process.Comparedtoconventionalrecyclingprocess,ourresearchisfocusedonrecoveringmostoftheusefulelements,includingNd,Pr,Dy,Co,andFetogetherinsteadofjustrareearthelements.Toimprovetherecyclingefficiencyandreducepollution,theco-precipitatingparametersweresimulatedandcalculatedusingMATLABsoftware.Mostofusefulelementswererecoveredbyaco-precipitationmethod,andtheobtainedcompositepowderswerethendirectlyfabricatedasrecycledNd-Fe-Bpowdersbyacalciumreduction-diffusion（RD）method.Therecoveryratesare98%,99%,99%,93%,and99%,forNd,Pr,Dy,Co,andFe,respectively.Theamountofusefulelementscontainedintherecoveredcompositepowdersisgreaterthan99.71wt%.TheprocessofRDforsynthesizingNd2Fe14BandsubsequentlyremovingCaOwasthoroughlyinvestigated.Furthermore,therecycledNd-Fe-Bmagnetexhibitsaremanenceof1.1T,acoercivityof1053kA/m,andanenergyproductof235.6kJ/m3,respectively,indicatingthatrecycledNd-Fe-Bsinteredmagnetwassuccessfullyrecoveredfromtheseverelycontaminatedsludgesviaaneffectiverecyclingroute.

简介：

简介：RadiallyorientedNd–Fe–BringmagnetswerepreparedbybackwardextrusionofMQ-Cpowder.Thepunchchamferradiushasagreatimpactonthemicrostructureandmagneticpropertiesoftheringmagnet.Withthechamferradiuschangingfrom2,5to8mm,thecracksintheinnerwalldecreaseobviouslywhilethecrystallographicalignmentdrops.Furthermore,themechanismofcaxisgrowthwassuggestedtobeacombinationofsheardeformationinthecornerandsolution-precipitationunderthestressparalleltoradialdirection.Thealignmentdropsonthetopofringbecausethegrainsgrowfreelyandsometexturedgrainsgrowthroughnucleationandrecrystallization.Inthepresentwork,theoptimalpunchchamferradiusisfoundtobe2mm,andinthiscase,theremanence,coercivity,andmaximumenergyproductoftheringmagnetachieve1.4T,670kJám,and342kJám,respectively.

简介：

简介：TooptimizethemagneticpropertiesofnanocompositeNd9Fe85B6magnets,theas-quenchedribbonswithdifferentmicrostructureswerepreparedatsixwheelvelocitiesfrom10to30ms-1throughrapidquenching,followedbyaseriesofannealingtreatmentsat550–800°Cfor5–10min.Itisfoundthatboththelargeinitialgrainsatlowcoolingrateandhighcontentofamorphousphaseathighcoolingratecausea-Fegrainscoarsening,whichleadstoadeclineinthestrengthofexchangecouplinginteractionandthedeteriorationofmagneticproperties.Inordertooptimizethemagneticproperties,theas-quenchedribbonsshouldbechosenwithrelativelysmallinitialgrainsaswellasasmallamountofamorphousphase.FornanocompositeNd9Fe85B6materials,theoptimizedmagneticpropertiesofHcj=446kAm-1,Br=0.86T,(BH)max=80kJm-3areobtainedforribbonspreparedat18ms-1afterannealingat620°Cfor5min.

简介：GrainboundarydiffusiontechniquewithTbH_3nanoparticleswasappliedtofabricateTb-lesssinteredNdFe-Bpermanentmagnetswithhighcoercivity.Themagneticpropertiesandmicrostructureofmagnetsweresystematicallystudied.Thecoercivityandremanenceofgrainboundarydiffusionmagnetareimprovedby112%andreducedby26%comparedwiththoseoftheoriginalmagnet,respectively.Meanwhile,boththeremanencetemperaturecoefficient(α)andthecoercivitytemperaturecoefficient(β)ofthemagnetsareimprovedafterdiffusiontreatment.MicrostructureshowsthatTbelementenrichesinthesurfaceregionofNd_2Fe_(14)Bgrainsandisexpectedtoexistas(Nd,Tb)_2Fe_(14)Bphase.Thus,themagneto-crystallineanisotropyfieldofthemagnetimprovesremarkably.Asaresult,thesinteredNd-FeBmagnetsbygrainboundarydiffusionwithTbH_3nanoparticlesexhibitenhancedcoercivity.

简介：ＣｕｒｉｅＴｅｍｐｅｒａｔｕｒｅｏｆＡｍｏｒｐｈｏｕｓＦｅＳｉＢａｎｄＦｅＷＳｉＢＡｌｏｙｓＷａｎｇＬｉｎｇｌｉｎｇ，ＺｈａｏＬｉｈｕａ，ＨｕＷａｎｇｙｕ（王玲玲）（赵立华）（胡望宇））ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃｓ，ＨｕｎａｎＵｎ...

简介：Theeffectofanexternalelectricfieldonthecrystallizationbehaviorofamorphous(Nd0.1Fe0.9)3Balloywasinvestigated.ThecrystallizationproductofNd2Fe23B3phasewasobtainedforthisamorphousalloyannealedat923Kfor300sinthepresenceofanexternalelectricfieldof300kV·m-1(50Hz);whilethecrystallizationproductsareNd1.1Fe4B4,α-Fe,andFe3Bphasesunderthesameannealingconditionexceptforfree-electricfield.Ontheotherhand,thesampleswereannealedat1023K,whichishigherthanthedecompositiontemperatureofmetastableNd2Fe23B3phase,for600s.Inthecaseofthepresenceofanexternalelectricfield,themetastableNd2Fe23B3phase,asamainphase,isstillstayedinthesample.ThisfactsuggeststhattheexternalelectricfieldenhancesthestabilizationofthemetastableNd2Fe23B3phase.Theeffectoftheexternalelectricfieldonthephaseselectionandstabilizationwasexplainedintermsofthespecificconductancedifferencebetweenthecrystallizationproducts.

简介：建立了脉冲熔融-飞行时间质谱法测定Nd-Fe-B材料中的氧、氮、氢的方法,在选定的实验条件下,氧、氮、氢的检出限分别为0.021,0.060,0.002μg/g;利用系列标准样品得到各元素的校准曲线,线性相关系数R2均大于0.99。将方法应用于Nd-Fe-B材料的测定,经对比实验验证,方法测定值与传统的脉冲熔融-红外/热导方法测定值相符合。