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1、纳米材料和纳米结构溶胶-凝胶法Sol-gelProcessing第三讲basedoninorganicpolymerizationreactions（无机聚合反应）usedtoprepareinorganicoxides,suchasglassesorceramics,especiallymulticomponentsystems（多组分体系）beabletocontrolthestructureonnanoscalefromtheearlieststagesofprocessingeasytoobtainnanostructu
2、redgrainswithcompositionalhomogeneity（组分均匀性）,higherpurity,lowerprocessingtemperaturesoverbothconventionalceramicprocessingandtraditionalglassmeltingbycontrollingthechemicaladditives（添加剂）andprocessing,butwithoutadoptingvacuumconditions(不适用于真空）1GeneralIntroductionTheso
3、l-geltechniquetomaterialsynthesisisbasedonsomeorganicprecursors（先驱物）,andthegelsmayformbynetworkgrowthfromanarrayofdiscreteparticlesorbyformationofaninterconnected3-Dnetworkbythesimultaneoushydrolysisandpolycondensation（缩聚作用）oforganometallic（有机金属）precursors.Thesizeoft
4、hesolparticlesdependuponsomevariablefactorssuchaspH,solutioncomposition,andtemperatureetc..Bycontrollingtheexperimentalconditions,onecanobtainthenanostructuredtargetmaterialsintheformofpowderorthinfilm.PrinciplesBasedondifferentkindsofprecursors,thesol-gelprocessingi
5、sroughlydividedintothreegroups:Silica（二氧化硅）sol-gelprocessingMetalalkoxide（金属醇盐）processingPechini-typeprocessing2ExperimentalApproachThewholesilicasol-gelprocessingcouldbedividedintothreesteps:hydrolysisandpolycondensation,gelationanddrying.2.1SilicaSol-GelProcessingL
6、iquidalkoxideprecursorandSi(OR)4ismixedwithwaterandacidorammonia,whereRrepresentsCH3,C2H5,orC3H7andacidorammoniaactsascatalyst.Thefollowinghydrolysisreactionwilltakeplace:Step1HydrolysisandPolycondensationThehydratedsilicatetrahedra（水合硅氧四面体）interactinacondensationrea
7、ction（缩合反应）,formingbonds:LinkageofadditionaltetrehedraoccursasapolycondensationreactionandeventuallyresultsinaSiO2network.Thewaterandalcoholexpelledfromthereactionremainintheporesofthenetwork.ThehydrolysisandpolycondensationreactionsinitiateatnumeroussiteswithintheTM
8、OS+H2Osolutionasmixingoccurs.Whensufficientinterconnectedbondsareformedinaregion,theyrespondcooperativelyascolloidalparticlesorasol
