溶膠—凝膠法合成鈣鈦礦型復(fù)合氧化物L(fēng)a-,1-x-Sr-,x-Fe-,1-y-Co-,y-O-,3-的實(shí)驗(yàn)研究.pdf

1、昆明理工大學(xué)碩士學(xué)位論文摘要200405摘要鈣欽礦型復(fù)合氧化物作為一種與環(huán)保和能源課題密切相關(guān)的新型材料，引起了國(guó)內(nèi)外許多科研人員的關(guān)注。由于鈣欽礦型氧化物的結(jié)構(gòu)和性能與制備過(guò)程密切相關(guān)，所以對(duì)其制備的研究至關(guān)重要。為了進(jìn)一步推動(dòng)鈣欽礦型復(fù)合氧化物的理論和實(shí)際應(yīng)用發(fā)展，本文系統(tǒng)研究了EDTA鰲合溶膠下凝膠法制備鈣欽礦復(fù)合氧化物的工藝過(guò)程，以改進(jìn)制備方法，并使制備方法具有可重復(fù)性和可靠性，用來(lái)合成結(jié)構(gòu)和性能優(yōu)良的鈣欽礦型復(fù)合摻雜氧化物。采

2、用EDTA鰲合溶膠一凝膠法制備了鈣欽礦型復(fù)合氧化物L(fēng)a.SrFe_YCoy03體系，借助X射線衍射(XRD)、透射電鏡(TEM)和掃描電鏡(SEM)、比表面測(cè)試、熱分析(TGDTA).氧程序升溫?zé)崦摳?02TPD)以及激光粒度分析等分析測(cè)試手段對(duì)實(shí)驗(yàn)過(guò)程和所制備的材料進(jìn)行了研究。通過(guò)實(shí)驗(yàn)改變不同的體系組成、鰲合劑用量、pH值、蒸發(fā)溶劑溫度、乙二醇用量和焙燒溫度等條件，探討了各種條件的改變對(duì)實(shí)驗(yàn)過(guò)程和結(jié)果的影響，并利用樣品對(duì)煤的催化燃燒考

3、察其催化性能。確定了EDTA鰲合溶膠一凝膠法制備鈣欽礦型復(fù)合氧化物實(shí)驗(yàn)的優(yōu)化條件，設(shè)計(jì)了最佳制備工藝過(guò)程。成功合成了La.Sr.Fe03(x_0.8)粉末樣品和La.Sr.Fe.yCoy03(x=0.2y=0.20.4)粉末樣品。X射線衍射分析(XRD)表明所有樣品均為鈣欽礦氧化物結(jié)構(gòu)，沒(méi)有簡(jiǎn)單金屬氧化物或其它雜相存在.合成的Lal.SrJe03樣品由正交晶系向菱方晶系轉(zhuǎn)變，La.xSr.Fe_yCoyO3(x=0.2y=0.20.4)

4、樣品為菱方鈣欽礦氧化物結(jié)構(gòu)。隨著Sr摻雜量x的增加，X射線衍射峰向高角度移動(dòng)，表明晶胞向尺寸減小的方向畸變。TEM觀察粉末樣品顆粒為球狀顆粒，平均粒徑約為61nm。通過(guò)掃描電子顯微鏡(SEM)觀察其形貌為多孔質(zhì)，BET(N2吸附)法測(cè)定比表面積為11.6m2g，平均孔容量0.034ccg平均孔徑11.9nm。激光粒度分析表明樣品平均粒度約0.18wm粒度分布比較均勻。通過(guò)差熱一熱重分析(TGDTA)研究了干凝膠熱分解過(guò)程，TG曲線在65

5、0℃以上趨于平穩(wěn)，說(shuō)明晶體已經(jīng)基本形成。02TPD曲線表明鈣欽礦結(jié)構(gòu)中存在表面弱吸附氧、氧空位吸附氧和晶格氧。樣品與煤混合燃燒的TGDTA結(jié)果表明:該實(shí)驗(yàn)過(guò)程中樣品對(duì)煤燃燒的催化效果不明顯，主要原因是樣品與煤混合很不均勻以及富氧氣氛的影響，須進(jìn)一步考察其催化性能。實(shí)驗(yàn)確定制備的優(yōu)化工藝條件為:溶液的pH值控制在中性到堿性范圍內(nèi)對(duì)有機(jī)試劑量進(jìn)行選擇時(shí)，合適的比例是金屬離子與EDTA鰲合劑的摩爾比在t昆明埋工大學(xué)碩1:學(xué)位論文ABSTRAC

6、T2004.05ABSTRACTPerovskitetypeoxideshaveattractedparticularlyatentionsfrompeoplefortheiruseasnewmaterialsinenvironmentalprotectionandenergyresource.Thestructureandpropertiesofthesematerialsarestronglyinfluencedbythesynth

7、esisprocesssoitisveryimportanttoimprovethepreparationmethods.InordertopromotetheresearchontheoryandapplicationofperovskitethepreparationofperovskitetypeoxidesbyEDTAsolgelmethodissystemicallystudiedtoimprovethemethodandit

8、sstabilityandrepeatabilityinthisthesis.PerovskitetypeoxidesLa_Sr.Fe.yCoy03weresynthesizedbyEDTAcomplexingsolgelmethod.TheprocessandthesampleswerecharacterizedviaXraydiffraction(XRD)transmissionelectronmicroscope(TEM)scan

9、electronmicroscope(SEM)thespecificsurfaceareamensurationthermogravimetricanalysis(TG)anddiferentialthermalanalysis(DTA)temperatureprogrammeddesorptionof02(02TPD)techniquesandlasergranularityanalysis.Theefectsofdiferentco

10、nditionssuchasthesystemcompositionspHvaluetheamountofchelanttheamountofglycoltheevaporationtemperatureandthecalcinationtemperaturewereinvestigatedintheprocess.AndthecatalysisofthesampleinZhaotonglignitecombustionwasstudi

11、edthroughTGDTAtechniqueinbrief.Theoptimumconditionsofthepreparationprocesshavebeenchosen.TwoseriesofperovskitetypeoxidesLal.Sr.Fe03(x_0.8)andLai.SrFel.YCoy03(x=0.2y=0.20.4)powdersampleshavebeensynthesized.TheXRDresultssh

12、owthatallthepowdersamplesareperovskitetypecompoundsandnosimplemetaloxidesoranyothersecondaryphaseexits.ThelatticesymmetryofLalSrxFe03systemchangesfromorthorhombictorhombohedrallattice.Lal..Sr%Fel.YCoy03systemhasrhombohed

13、rallatice.WiththeincreaseofxthemaindifractionpeaksofXRDmovetolargeangleswhichrepresentadistortiontosmallsizeofthecell.TEMobservationshowsthepowdersareuniforrhwithsphericalshape.Theaveragesizeisabout61rimindiameter.Throug

14、hSEMthepowdercanbeidentifiedtoporousstructurewithspecificsurfaceareasofabout11.6m2gtotalporevolumeof0.034ccgandaverageporediameterof11.9nrn妙BETmethod.Theparticleisuniformwithanaveragesizeofabout0.1810nbylasergranularitya

15、nalysis.ThethermaldecompositionprocesshasbeenstudiedbyTGDTAtechniquesSmoothTGcurveswereobtainedatabout6200Cindicatingtheformationofperovskitestructure.OxygendesorptionfromLal.XSrxFe03below8500Cwasexaminedby02TPDandtheres

16、ultshowsthattherearethreetypesofoxygeninthestructure.AccordingtoTGDTAresultsthesamplesshowlittlecatalysistoZhaotonglignitecombustionmainlybecausethesamplesdidntmixedwiththeligniteuniformlyandatthesametimetherewasexcessiv

17、eoxygeninexperimentalatmosphereleadingtowithoutobviouscatalysisefect.Theoptimumconditionsoftheprocessaresummarizedas:thepHvalueofthesolutionshouldbeadjustedto7^14themolratioofmetaliontoEDTAshouldbe1:1.1to1:1.2themolratio

18、ofglycoltoEDTAis3:1theconcentrationtemperatureshould卜60C^700C，calcinationtemperatureshouldbe700C8000C.Inconclusion、Vebycanobtainsinglephasedperovskitetypeoxidespowderwithsmallparticlesizewithhighstabilityandrepeatability