溶胶凝胶必看精华书 solgel chemistry and molecular synthesis

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1、J.C.Jansen,M.Stbcker,H.G.KargeandJ.Weitkamp(Eds.)AdvancedZeoliteScienceandApplicationsStudiesinSurfaceScienceandCatalysis,Vol.85101994ElsevierScienceB.V.Allrightsreserved.Sol-GelChemistryandMolecularSieveSynthesisJ.LivageChimiedelaMatiheCondens&,UniversitkPierreetMarieCurie4placeJussieu-7525

2、2Paris-FranceSol-gelchemistryprovidesanewapproachtothepreparationofoxidematerials[11.Startingfromasolution,asolidnetworkisprogressivelyformedviainorganicpolymerizationreactions.Thetermsol-gelchemistrycouldactuallybeusedinabroadersensetodescribethesynthesisofinorganicoxidesbywetchemistrymetho

3、dssuchasprecipitation,coprecipitationorhydrothermalsynthesis.Tworoutesarecurrentlyuseddependingonthenatureofthemolecularprecursor.Theinorganicroutewithmetalsaltsinaqueoussolutionsandthemetal-organicroutewithmetalalkoxidesinorganicsolvents.Inbothcasesthereactionisinitiatedviahydrolysisinorder

4、togetreactiveM-OHgroups.ThisreactioncanbesimplyperformedbyaddingwatertoanalkoxideorbychangingthepHofanaqueoussolution[2].Condensationthenoccursleadingtotheformationofmetal-oxygen-metalbonds.Condensedspeciesareprogressivelyformedfromthesolutionleadingtooligomers,oxopolymers,colloids,gelsorpre

5、cipitates.Oxopolymersandcolloidalparticlesgiverisetosolswhichcanbeshaped,gelled,driedanddensifiedinordertogetpowders,films,fibresormonolithicglasses[3].Thispaperdescribesthebasicchemicalreactionsinvolvedinsol-gelsynthesesfrombothinorganicandmetal-organicprecursors.1.METALCATIONSINAQUEOUSSOLU

6、TIONSMolecularsievesareusuallypreparedviahydrothermalmethodsfromaqueoussolutions[4].Thisroutehasalreadybeenusedforalongtimeinindustryforthesynthesisofcatalystsandceramicpowders.Literatureprovidesmanydatadescribingthehydrolysisofmetalcationsindilutesolutions[5]butverylittleisknownabouttheform

7、ationofpolynuclearspeciesatconcentrationsgreaterthanabout1mol.1-1,althoughtheseconditionsaregenerallyrelevanttothesynthesisofsolidphases.Oneofthemainproblemarisesfromthefactthatwaterbehavesbothasaligandandasolvent.Alargenumberofoligomericspeciesare