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1、納米材料和納米結構溶膠-凝膠法Sol-gelProcessing第五講Basedoninorganicpolymerizationreactions（無機聚合反應）Usedtoprepareinorganicoxides,suchasglassesorceramics,especiallymulticomponentsystems（多組分體系）BeabletocontrolthestructureonnanoscalefromtheearlieststagesofprocessingEasytoobtainnanostruc
2、turedgrainswithcompositionalhomogeneity（組分均勻性）,higherpurity,lowerprocessingtemperaturesoverbothconventionalceramicprocessingandtraditionalglassmeltingbycontrollingthechemicaladditives（添加劑）andprocessing,butwithoutadoptingvacuumconditions1GeneralIntroductionThesol-ge
3、ltechniquetomaterialsynthesisisbasedonsomeorganicprecursors（先驅(qū)物）,andthegelsmayformbynetworkgrowthfromanarrayofdiscreteparticlesorbyformationofaninterconnected3-Dnetworkbythesimultaneoushydrolysisandpolycondensation（縮聚作用）oforganometallic（有機金屬）precursors.Thesizeofthe
4、solparticlesdependuponsomevariablefactorssuchaspH,solutioncomposition,andtemperatureetc..Bycontrollingtheexperimentalconditions,onecanobtainthenanostructuredtargetmaterialsintheformofpowderorthinfilm.PrinciplesBasedonthedifferenceoftheprecursorsused,thesol-gelproce
5、ssingisroughlydividedintothreegroups:Silica（二氧化硅）sol-gelprocessingMetalalkoxide（金屬醇鹽）processingPechini-typeprocessing2ExperimentalApproachThewholesilicasol-gelprocessingcouldbedividedintothreesteps:hydrolysisandpolycondensation,gelationanddrying.2.1SilicaSol-GelPro
6、cessingLiquidalkoxideprecursorandSi(OR)4ismixedwithwaterandacidorammonia,whereRrepresentsCH3,C2H5,orC3H7andacidorammoniaactsascatalyst.Thefollowinghydrolysisreactionwilltakeplace:Step1HydrolysisandPolycondensationThehydratedsilicatetrahedra（水合硅氧四面體）interactinaconde
7、nsationreaction（縮合反應）,formingbonds:LinkageofadditionaltetrehedraoccursasapolycondensationreactionandeventuallyresultsinaSiO2network,whilethewaterandalcoholexpelledfromthereactionremainintheporesofthenetwork.Thehydrolysisandpolycondensationreactionsinitiateatnumerou
8、ssiteswithintheTMOS+H2Osolutionasmixingoccurs.Whensufficientinterconnectedbondsareformedinaregion,theyrespondcooperativelyascolloidalparticlesora
