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电化学有关论文范文素材,与硕士生学位文开题相关毕业论文格式范文
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#30340;转动,有利于提高永磁体的磁性能.关 键 词:Nd-Fe-B永磁体,磁性能,晶化热处理,熔体快淬
ABSTRACT
Intherecentyears,bondedNd-Fe-Bpermanentmagsweredevelopedrapidlyasforit'smoldingeasilyandlowpricebythetechnologyofmeltspinning.Inthesedays,bondedmagshavetakenuptheimportantroleatthemarketofpermanentmags.Theyareusedinthemanyfields,suchasputer,car,motor,munication,medicaltreatmentandsoon.Theyhavebeethebasematerialsofthemessagesandmachinesindustry.But,bondedmagshaveashorting,Magismpropertiesislowerthansinteredmags.Themainfactoristhatthepowdersenergyislow.Thehigherpowdersenergiesare,thebetter-bondedpermanentsmagsis.Inordertoimprovethemagism,thisarticlemainlyinvestigatedthetechnologiesofmagicpowderspreparationanddie-upsettingforbondedpermanentsalloys.
Thepowdersforisotropicpermanentsalloyswerepreparedbythetechniqueofmeltingatthehightemperatureandvacuummelt-spunintheexperiment.TheBHhystereticloopapparatusmeasuredmagicpropertiesofpermanentalloy.SEMwasusedforobservingmicrostructureofalloys,analyzedtheaffectionofcrystallitesinchesforthemagicenergiesofthebondedpermanentsmags.TEMwasappliedforthecoexistencemicrostructureofcrystalandamorphousphase.Thecrystalstructureofphaseswasanalyzedbythewayofelectricdiffraction.Atthesametime,thetransformationsofphasestructureintheprocessofcrystal-treatmentwerestudied,too.CrystaltrendwasexperimentedbyusingX-diffractionapparatus.
Allresultsofexperimentarefollowed:Whentheotherelementsarehomology,somePrelementinsteadofNdmayimprovethecoerciveforceofthepermanentmagsintheNd-Fe-Bpermanentsalloys.Thebestvalueisupto1227KA/m,Melt-spunalloysincludethreeparts:theamorphousarea,thecrystalareaofpoleandtheequal-axiscrystalarea.Whenthevelocityis21m/sofmelt-spun,thepercentofthecrystalareaofpoleisplentiful,theupgrowthofpolecrystaleintobeingthetexture.Theresultofexperimentstatedthatthistextureisthesametoeasymagizationorientationofpermanentmagicalloys,Thefineanduniformitycrystalcouldbegainedbythetechnologyoftheheattreatmentatthehightemperatureforashorttime.Theareaof
电化学有关论文范文素材
Keywords:Nd-Fe-Bpermanentmags,Magicproperty,Crystallizationheattreatment,Melt-pun
论文题目:水热合成LaAMnO3型钙钛矿及其磁热效应的研究
HydrothermalSynthesisandMagocaloricEffect
ofLaAMnO3Perovskite
研究生姓名:李解
导师姓名:李保卫教授
协助导师:王正德副教授
专业:材料加工工程
摘 要
室温磁致冷技术因具有代替气体压缩制冷的可能倍受各国关注..与其它磁致冷工质相比,稀土锰钙钛矿材料有以下优势:低磁场下其磁热效应较高,而且化学性质稳定,居里温度可调,电阻率大,成本低,是室温制冷的理想工质.
水热法制备了室温附近磁冷材料—LaAMnO3型钙钛矿(A为Ca,CaBa或CaSr),研究了合成条件(碱度,水热温度,水热时间)对其形貌的影响及-曲线测量仪研究了不同形貌钙钛矿的磁热效应,确定了La0.65Ca0.18Sr0.17MnO3与La0.7Ca0.21Ba0.09MnO3样品的最佳水热合成条件最佳合成条件为:碱度4.16mol/L和6.53～8.9mol/L水热温度240℃以上水热时间80h左右同时找到了影响合成结果的关键性因素—高压釜的密封性,最终改进了工艺:将最初的"水热—热处理"合成工艺变为一步水热即可合成.
水热条件(碱度,水热温度,水热时间)影响钙钛矿成分及形貌,不同形貌的钙钛矿样品,其磁热效应大小有差别:丝状样品比块状样品磁热效应大,而且化学性能更稳定一些采用最佳水热条件一步直接合成的La0.65Ca0.18Sr0.17MnO3样品,很纯其居里温度Tc为323K,最大为0.29KA位离子掺杂对钙钛矿(LaAMnO3)的磁热均有影响对于不同系列的La1-xAxMnO3型钙钛矿样品,其居里温度Tc与A位离子掺杂量x之间的规律性不同采用最小二乘法回归出La0.65Ca0.35-xSrxMnO3La0.7Ca0.3-xBaxMnO3拟合曲线和.依据这样的曲线规律,很容易制得室温附近的成分不同的钙钛矿样品,并能预测已知成分钙钛矿样品的居里温度.关 键 词:水热合成钙钛矿磁热效应居里温度Nownear-roomtemperaturemagicrefrigeranttechnologyismorefocusedonbymanycountriesforitsreplacinggaspressioninthefuture.InnerMongoliaUniversityofScienceandTechnologyhadcooperatedwithBaotouResearchInstituteofRareEarthforsixyearsonthestudyofDevelopmentofMagicRefrigerantTechnology.Thisthesisbelongstothestudyitemanditsmainpurposesaretoprepareandstudynear-roomtemperaturemagicrefrigerantmaterialsandsupplymaterialsformodemachinefinally.
Inparisionwithothermagicrefrigerantmaterials,rare-earthmanganeseperovskitehassuchadvantagesashighmagocaloriceffectatlowmagicfield,goodchemicalstability,tunableCurietemperature,largeelectricalresistivityandlowcost.Itisanidealnear-roomtemperaturemagicrefrigerantmaterial.
Inthiswork,thenear-roomtemperaturemagicrefrigerantsamplesofLaAMnO3(AisCa,CaBaorCaSr)seriesperovskitewerepreparedbyhydrothermalmethod.Theinfluencesofpreparedconditions(alkalinity,hydrothermaltemperature,hydrothermaltime)ontheirmineralposition,shapesandthemagocaloriceffectsofdifferentshapes'perovskitesamplesandtheirhightemperaturehotstabi
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