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1、MakingsyntheticmaterialsmoreimperviousRUBengineersdevelopplasma-basedcoatingprocessesbyJuliaWeiler January8,2015 Organiclight-emittingdiodes,artificialkidneysandPETbottleshaveonethingincommon:theyareallmadeofsyntheticmaterials.Unfortunately,thesematerialsarepermeab
2、letovariousgases.Inordertomakeplasticmoreimpervious,RUBengineersuseplasmastoapplywafer-thinlayersonsurfaces.PETbottleshavereplacedglassbottlesinmanyinstances,coolingshelvesarefullofplasticpackaging,acurrentdebaterevolvesaroundsupplyingbabyfoodinplasticcontainersrat
3、herthanjars,seeingastheyarelighterandlesslikelytobreak.However,toomanypeopleareyetconcernedthatharmfulsubstancescontainedinthepackagingmayseepintothefood.Novelplasma-basedcoatingprocessesmayprovidearemedy,andtheymayalsoextendthefoodproducts’shelflife.AttheInstitute
4、forElectricalEngineeringandPlasmaTechnology,ProfDr-Ing.PeterAwakowiczandhisteamdevelopprocessesforcoatingsurfaceswithprotectivelayersthatrenderthesyntheticmateriallesspermeable.Fig.1Plasticshaveaverypoorgasbarrier,i.e.theyarepermeabletoairwhichcanpassthroughthemate
5、rialinbothdirections.“ThisiswhywaterstoredinPETbottleslosescarbondioxideandwhyfoodgoesbad,forexamplebychangingitsflavour,”saysPeterAwakowicz(fig.1).Thecoatinghisgroupisworkingonwouldmakeplasticpackagingonehundredtimesmoreimperviousthanitistoday.Consequently,theshel
6、flifeoffoodproductswouldbeprolonged,andtheywouldbeprotectedfromsubstancesthatseepoutfromthesyntheticmaterial.“Sometimesyouhearpeoplesay,‘Thistastesofplastic’,andtheyareright,”explainsAwakowicz.“Asyntheticmaterialthatdoesnotleakingredientsofsomesortdoesnotexist.With
7、ourcoating,thevolumeofthosesubstancescouldbereducedtoonepercentofthevolumethatusuallyseepsout.”TheRUBteamstudiesinwhatwayanobjectwithanychosenshapemadefromaspecificsyntheticmaterialmaybebestcoatedusinga plasma.Forthispurpose,theresearchersutiliseplasmaenhancedchemi
8、calvapourdeposition,i.e.PECVD.Inthecourseofthisprocessthesubstancehexamethyldisiloxaneisvaporised,blendedwithoxygenanddispersedinplasma.Thus,sili