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1、纳米材料和纳米结构溶胶-凝胶法Sol-gelProcessing第五讲Basedoninorganicpolymerizationreactions（无机聚合反应）Usedtoprepareinorganicoxides,suchasglassesorceramics,especiallymulticomponentsystems（多组分体系）BeabletocontrolthestructureonnanoscalefromtheearlieststagesofprocessingEasytoobtainnanostruc
2、turedgrainswithcompositionalhomogeneity（组分均匀性）,higherpurity,lowerprocessingtemperaturesoverbothconventionalceramicprocessingandtraditionalglassmeltingbycontrollingthechemicaladditives（添加剂）andprocessing,butwithoutadoptingvacuumconditions1GeneralIntroductionThesol-ge
3、ltechniquetomaterialsynthesisisbasedonsomeorganicprecursors（先驱物）,andthegelsmayformbynetworkgrowthfromanarrayofdiscreteparticlesorbyformationofaninterconnected3-Dnetworkbythesimultaneoushydrolysisandpolycondensation（缩聚作用）oforganometallic（有机金属）precursors.Thesizeofthe
4、solparticlesdependuponsomevariablefactorssuchaspH,solutioncomposition,andtemperatureetc..Bycontrollingtheexperimentalconditions,onecanobtainthenanostructuredtargetmaterialsintheformofpowderorthinfilm.PrinciplesBasedonthedifferenceoftheprecursorsused,thesol-gelproce
5、ssingisroughlydividedintothreegroups:Silica（二氧化硅）sol-gelprocessingMetalalkoxide（金属醇盐）processingPechini-typeprocessing2ExperimentalApproachThewholesilicasol-gelprocessingcouldbedividedintothreesteps:hydrolysisandpolycondensation,gelationanddrying.2.1SilicaSol-GelPro
6、cessingLiquidalkoxideprecursorandSi(OR)4ismixedwithwaterandacidorammonia,whereRrepresentsCH3,C2H5,orC3H7andacidorammoniaactsascatalyst.Thefollowinghydrolysisreactionwilltakeplace:Step1HydrolysisandPolycondensationThehydratedsilicatetrahedra（水合硅氧四面体）interactinaconde
7、nsationreaction（缩合反应）,formingbonds:LinkageofadditionaltetrehedraoccursasapolycondensationreactionandeventuallyresultsinaSiO2network,whilethewaterandalcoholexpelledfromthereactionremainintheporesofthenetwork.Thehydrolysisandpolycondensationreactionsinitiateatnumerou
8、ssiteswithintheTMOS+H2Osolutionasmixingoccurs.Whensufficientinterconnectedbondsareformedinaregion,theyrespondcooperativelyascolloidalparticlesora
