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ID:37617262
大小:1.93 MB
页数:42页
时间:2019-05-26
《溶胶凝胶必看精华书 solgel chemistry and molecular synthesis》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
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
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