陶瓷材料制备2.pdf

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1、Precursors for sol-gelHydrolysis behavior of various yttrium precursorsOC2H4OMeFibersafter7 daysNo precipitateNo effectY3(OR)5(acac)4acac firstThen OAcAcidic catalysis(precipitate)No precipitateNo effectY2(OAc)2(acac)4OC2H4OMeTransparent gel(t=15min)Transparent gel(t=15min)No effectY(OR)310OPriAmorp

2、hous precipitateAmorphous precipitateCrystalline precipitateY5O(OPri)1315100.13Ligand removedHydrolysis ratio h=H2O/MCompoundL.G.Hubert-Pfalzgraf et al.,MRS Symp.Proc.,Vol.180,1990,p73.Precursors for sol-gelTi(OPri)4+2 acacPriO-Ti-O-Pri+2 PriOHO OO OC CC CH3C CH CH3H3C CH CH3Roles of acetylacetone:(

3、1)decreasing hydrolysis rate;(2)modifier to cause linear-chain polymerization(1-D rubbery polymers).Precursors for sol-gelOther organic chelating agents to cause rubbery polymerization:(1)ethylenediamine(en);(2)diethylenetriamine(DETA);(3)acetic acid.OHOAcOTiHOAcOTiAcOHOTiiiiiPr)()Pr()(Pr()Pr(34+TiT

4、iOPriOPriPriOOPriOPriPriOOOCCH3OOCCH3CA less hydrolyzable bidentatedbridging alkoxide is yelded and henece the gelation time increases.Multicomponent oxides preparation by sol-gelThe hydrolysis rates of different precursors should be matched in order to get a homogeneous gel:(1)Using chelating organ

5、ic ligands to control the hydrolysis rate of the more reactive alkoixdes;(2)Adopting prehydrolysis of less reactive alkoxides;(3)Using complex alkoxides as precursors.6.4 St6.4 Stber process and Ostwald ripeningber process and Ostwald ripeningOstwald ripening:Small particles dissolve faster than lar

6、ger particles.As the process is dynamic and reversible,smaller particles may be dissolved to feed growth of the larger particles.The growth stops when the difference in solubility between the largest and smallest particle is a few ppm.It is therefore possible to prepare spherical,non-porous,highly m

7、onodisperse silica particles(Stber particles)which have diameters of several 100 nm from a gel.W.Stber,A.Fink,and E.Bohn.1968.J.Colloid Interface Sci.,26,62Origin of Ostwald ripeningRTrVPrPmlv 2)(ln0=Kelvin equation(Liq-Vap interface)Vm=molar volume =surface tensionr=radiusRTrVCrCmsl 2)()(ln=Ostwald

8、-Freundlich equation(Liq-solid interface)Gibbs-Thomson equation:rHTrTTrTsfslmBmmBm4)()(=TmB=Bulk melting temperature sl=solidliquid interface energy(per unit area)Hf=bulk enthalpy of fusion(per gram of material)s=density of solidAuRelated effect:Ouzo effect for stabilization of emulsionThe ouzo effe

9、ct(also louche effect and spontaneous emulsification):is a phenomenon observed when water is added to ouzo and other anise-flavored liqueurs and spirits.The ouzo effect occurs when a strongly hydrophobic essential oil of trans-anethole is dissolved in a water-miscible solvent,such as ethanol,and the

10、 concentration of ethanol is lowered by addition of small amounts of water.Stber processtetraethylorthosilicate,tetra-ethoxy-silaneTEOSSi(OC2H5)4+C2H5OH+NH4OH+H2Oe.g.0.5 M TEOS/6 M H2O/0.0032 M HCl(in ethanol)+0.0032 M NaOH/0.02 M NH3(in ethanol)The average particle size of SiO2can be varied from 20

11、00 to 10 nm by varying the amount of ammonia and of water.Stber processStber processStber processto microporous SiO2spheres0.2M NH3/3.2M H2O in ethanol0.2M TEOS in ethanol+Porogens:(1)3-aminopropyltriethoxysilane(APTES)(2)glycerolis known to adsorb very well to cations and oxide surfaces under basic

12、 conditions.The glycerol was added directly to the water/ammonia/ethanol mixture prior to the addition of TEOS.R.Vacassy et al.,J.Colloid Interface Sci.227,302315(2000)Stber processto microporous SiO2spheresSiO2100/024 hSiO2100/04 hSiO2gly24hTEOS/APTES 90/10Then 500C heatingStber processto microporo

13、us SiO2spheres6sBETdS=Sol-gel processes for La1-xSrxCoO3-Aqueous sol-gelPolymeric sol-gelLa1-xSrxCoO3-fine powderLa1-xSrxCoO3-porous layerMater.Sci.Eng.B 39(2)(1996)129-132.J.Mater.Chem.6(5)(1996)815-819.Sol-gel processes for PZT,PbZr1-xTixO3The method may provide good control over stoichiometry and

14、 reduced sintering temperature.This is especially important if one of the components are volatile.May also enable production of low temperature phases.The largest piezoelectric response of PZT:x=0.47.The stoichiometryis difficult to control by the ceramic method,where heating at 1100C for several ho

15、urs is needed.Louis:TIPT6.5 6.5 PechiniPechini method for powder preparationmethod for powder preparationModified resinintermediate processing of perovskitepowders:Part I.Optimization of polymeric precursorsLone-Wen Tai,Paul A.LessingThe formation of a polyester between citric acid(CA)and ethylene g

16、lycol(EG)was found to be a decisive factor for the foaming of resin intermediates in a Pechini-type powder process.This process was modified by changing the organic mass ratio of CA/EG which results in ceramic powders with different morphologies.The most porous resin intermediate(with or without che

17、latedcations)was prepared using a polymeric gel made of equimolar citric acid and ethylene glycol.It was also found that a premixing of organic components,prior to adding constituent nitrate solutions,makes the whole process more controllable.Keywords:Ceramics;Chemical synthesis;PowderMaterials:La0.

18、85Sr0.15CrO3J.Mater.Res.,Vol.7,No.2,1992,p.502.Pechnis method related patents and papers1)M.Pechini,“Method of Preparing Lead and Alkaline Earth Titanates andNiobates and Coating Method Using the Same to Form a Capacitor,”U.S.Pat.No.3 330 697,July 11,1967.2)N.G.Eror and H.U.Anderson,“Polymeric Precu

19、rsor Synthesis of CeramicMaterials,”Mater.Res.Soc.Symp.Proc.,73,57177(1986).3)P.A.Lessing,“Mixed-Cation Oxide Powders via Polymeric Precursors,”Am.Ceram.Soc.Bull.,68 5 10021007(1989).4)(a)L.-W.Tai and P.A.Lessing,“Modified Resin-Intermediate Processing ofPerovskite Powders:Part I.Optimization of Pol

20、ymeric Precursors,”J.Mater.Res.,7,50219(1992).(b)L.-W.Tai and P.A.Lessing,“Modified Resin-IntermediateProcessing of Perovskite Powders:Part II.Processing for Fine,NonagglomeratedSr-Doped Lanthanum Chromite Powders,”J.Mater.Res.,7,50219(1992).5)H.U.Anderson,“Review of p-type Perovskite Materials for

21、SOFC and OtherApplications,”Solid State Ionics,52,3341(1992).6)L.-W.Tai,H.U.Anderson,and P.A.Lessing,“Mixed-Cation Oxide Powders viaResin Intermediates Derived from a Water-Soluble Polymer,”J.Am.Ceram.Soc.,7512 349094(1992).Pechnis methodIn this powder-synthesis route,citric acid forms poly(basic ac

22、id)chelates with the metal cations.These chelates undergo polyesterification,when heated with a poly(hydroxy alcohol),such as ethylene glycol,at a temperature of 150Cto form a polymeric precursor resin.The cations are expected to be dispersed uniformly throughout the polymeric resin.Additional heati

23、ng of the resin in air(at 400C)results in the removal of organics and the formation of a char with a controlled cation stoichiometry,with little cation segregation.Then,the char is heated to higher temperatures and oxidized to form the oxide ceramics.Ethylene glycolNitrates solution+citric acid+ethy

24、lene glycol?heat and evaporation?“resin”(xerogel)?calcine?grinding?sinteringExample:Preparation of strontium-and/ormagnesium-doped lanthanum gallate(LSGM)PowdersPrecursors:La(NO3)39H2O,Ga(NO3)3 xH2O,Sr(NO3)2,Mg(NO3)26H2OCitric acid monohydrate(C6H8O7),ethylene glycol(C2H6O2)CA:EG=60:40(w/w)CA:Mtot=1

25、.88This solution was homogenized by stirring at room temperature for 1 h.Then,the resulting clear solution was evaporated(in a period of 3 h)ona hot plate until first a clear yellow gel and then a dark brown resin formed.The obtained resins(following overnight drying in an oven at 100C)were scraped

26、off the beakers with a spatula,then ground by hand using an agate mortar and pestle,and finally calcined isothermallyin a stagnant-air-atmosphere box furnace over a temperature rangeof 2001400C.Each calcination batch of powders was heated tothe specified temperature at a rate of 5C/min,annealed at t

27、histemperature for 6 h,and then furnace-cooled to room temperature.Tas et al.,J.Am.Ceram.Soc.8312(2000)2954.Analyses of LSGM precursors at different temperaturesFig.3.XRD spectra of La0.8Sr0.2Ga0.83Mg0.17O2.815precursor powders calcined at different temperatures.Secondary phases observed are indicat

28、ed(“1,”LaSrGa3O7peak,“2,”LaOOH peak,“3,”La2O3peak,and“4,”LaSrGaO4peak).Table I.Results of residual carbon analyses(wt%)_ Temp.(C)LaGaO3La0.9Sr0.1GaO2.95La0.8Sr0.2Ga0.83Mg0.17O2.815_ 10031.7(3)33.3(2)32.7(6)35010.3(3)10.4(1)13.8(2)7000.530(3)0.550(5)0.280(4)8500.059(1)0.143(9)0.168(3)10000.042(2)0.05

29、0(3)0.060(2)13400.0100.0124(2)0.0143(4)_ Microstructures of LSGM precursors at different temperatures100C500C700C1000C1400C(pellets)6.6 Glycine-nitrate pyrolysis(GNP)method6.6 Glycine-nitrate pyrolysis(GNP)method（甘氨酸盐热解法）Ce(NO3)solutionSm(NO3)3solutionblended in a certain ratioGlycine was added G:M=

30、0.7 to 3.4Heated under stirringViscous solutionEvaporation,and ignited to flamePale-yellow ashSm-doped CeO2750/2h2/minFlow chart for preparing SDC powderDoped CeODoped CeO2 2prepared with prepared with glycineglycine-nitrate methodnitrate methodGlycine-Nitrate Process(GNP)is a self-sustaining combus

31、tion synthesis technique,containing metal nitrates as oxidizers and glycine as a fuel.NH2CH2COOH?Forms complexes with metal ions Preventing selective precipitationMaking the metals mixed at atomic level?Fuel for combustion NH2CH2COOHCe4+Sm3+Doped CeODoped CeO2 2prepared with prepared with glycinegly

32、cine-nitrate methodnitrate methodCe(NO3)3+NH2CH2COOH CeO2+CO2+H2O+N2(glycine/metal=14/91.56)Sm(NO3)3+NH2CH2COOH Sm2O3+CO2+H2O+4N2(glycine/metal=15/91.67)For SDC:the glycine/metal1.58all glycine were oxidized by nitrate(no air),the gaseous products of combustion were CO2、H2O and N2(no CO)Assumption:T

33、he powders morphology and sinterablity is influenced by the ratio of glycine/metal.304050607080904224203314002223112202001111450oC600oCash2X-ray diffraction patterns of the ash as synthesized by a glycine-nitrate process,the SDC powder calcined at 600oC,and a SDC pellet sintered at 1450oC.Characteri

34、zation(TEM)TEM photographs of SDC powders heated at 750oC.The powders were prepared with glycine-to-metal ratio of(a)0.7,(b)1.0-2.5,and(c)3.4a100nm100nmb250nmcCharacterization(SEM)SEM images of Sm0.2Ce0.8O1.9pellets fracture at different ratio sintered at 1500o C for 5h a)the glycine/metal ratio of

35、0.7 or 3.4 b)the glycine/metal ratio of 1.7abExample：Pechini method to CeO2-SnO2and CeO2-TiO2coatingsThin Solid Films 410(2002)1-7.6.7 Other wet-chemical method6.7 Other wet-chemical methodsI)Hydrothermal method to CuO-5051 01 52 02 53 03 54 04 55 05 501 0 02 0 03 0 04 0 05 0 06 0 07 0 08 0 0 A:o v

36、e ra ll c a p a c ity a t C/5 ra te w ith 3 0%A B B:o v e r a ll c a p a c ity a t C/5 r a te w ith 2 0%A B C:o v e r a ll c a p a c ity a t 2 C r a te w ith 3 0%A BC y c le n u m b e rSpecific capacity(mAh/g)C B AScripta Mater.57(2007)337.?通过水热处理，可以得到由纳米针状组装而成的蒲公英状微米球，直径在2-5 m。?样品的比表面积为19 m2/gThree

37、 different types of synthetic methods for generation of hollow nanostructures:(A)random aggregation of nanocrystallites and core hollowing via Ostwald ripening,resulting in polycrystalline nanospheres;(B)two-dimensional oriented attachment for formation of thin crystal planes and construction of hol

38、low octahedra in a plane-by-plane manner;and(C)three-dimensional oriented attachment for solid nanocubes and creation of hollow interiors by Ostwald ripening.Hashed areas indicate the solid parts of nanostructures,and dark areas represent interior spaces.H.C.Zeng,et al.,Langmuir 2006,22,7369-7377.(N

39、ational University of Singapore)Two synthetic strategies for hollow nanostructured materials:(1)template-assisted synthesis with a)hard templates such as polymeric and metallic cores or b)soft templates such as surfactant micelles or ionic solvents;(2)template-free synthesis:through various physicoc

40、hemical processes.II)Fe3O4亚微米粉体负极材料亚微米粉体负极材料(水热制备水热制备)?Fe3O4亚微米粉体具有低的首次容量损失较高的的比容量，但能量效率较低。（亚微米粉体具有低的首次容量损失较高的的比容量，但能量效率较低。（J.Power Sources 195(2010)5379)FeCl36H2O(1.35 g)in EG(35 ml)+PEG2000(1 g)+NaAc(3.6 g)?(200C/autoclave/48 h)?submicron-Fe3O4spheroidsFe3O4亚微米粉体负极材料亚微米粉体负极材料(水热制备水热制备)III)CuO纳米带状团

41、簇的自牺牲模板法合成纳米带状团簇的自牺牲模板法合成200 nm2m(a)(b)200 nm2m2m(a)(b)02468100200400600 CountsEnergy(keV)COCuCuCu(d)(c)Cu：O=1：112ZnZnNH3,Cu(NH3)4 2+34Zn10M NaOH-NH3-Cu(OH)2-Zn(OH)212ZnZnNH3,Cu(NH3)4 2+34Zn10M NaOH-NH3-Cu(OH)2-Zn(OH)2Cu(NH3)42+?Cu2+4NH3 NH3+H2O?NH4+OH-Zn+4NH3+2H2O?Zn(NH3)42+2OH-+H2(g)Zn(NH3)42+?Zn2+4NH3Cu2+2OH-?Cu(OH)2(s)Zn2+2OH-?Zn(OH)2(s)Zn(OH)2+2NaOH?Na2Zn(OH)4 Zn+2NaOH+2H2O?Na2Zn(OH)4+H2(g)Cu(OH)2(s)?CuO(s)+H2O 第一步：第二、三步：第四步：反应机理分析