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1、ThinFilmDiamondbyChemicalVapourDepositionMethodsM.N.R.Ashfold,P.W.May,andC.A.RegoSchoolofChemistrylUniversityofBristol,BristolBS8ITS,U.K.N.M.EverittDepartmentofAerospaceEngineering,UniversityofBristol,BristolBS81TR,U.K.1Introductionenergyofgraphite.DiamondisthedensestallotropeofcarbonDiamond,the
2、sp3-bondedallotropeofcarbon,haslonghelda(pdlamond=3513kgm-3,cf.PgraphLte=2260kgm-at293K);specialplaceintheheartsandmindsbothofscientistsandthethus,athighpressure,diamondmustbethestableformofsolidpublicatlarge.Forthelatter,theworddiamondmayconjureupcarbon.Thisisthescientificbasisforthehighpressur
3、ehighimagesof57facettedbrilliantgemstones,Amsterdamorminestemperature(HPHT)techniques(inwhichdiamondiscrystal-inSouthAfrica,wealthandspecialoccasions.Tothescientist,lized-frommetalsolvatedcarbonatP-50-100kBarandTdiamondisimpressivebecauseofitswiderangeofextreme1800-2300K)bywhichdiamondhasbeensyn
4、thesizedproperties.AsTable1shows,bymostmeasuresdiamondis‘thecommerciallyforover30years.2-biggestandbest’:Itisthehardestknownmaterial,hasthelowestcoefficientofthermalexpansion,ischemicallyinertandwearresistant,offerslowfriction,hashighthermalconductivity,iselectricallyinsulatingandopticallytransp
5、arentfromtheultra-Table1Someoftheoutstandingpropertiesofdiamondviolet(UV)tothefarinfrared(IR).Giventhesemanynotableproperties,itshouldcomeasnosurprisetolearnthatdiamondExtrememechanicalhardness(-90GPa)alreadyfindsuseinmanydiverseapplicationsincluding,ofStrongestknownmaterial,highestbulkmodulus(1
6、.2x10l2Nm-*),course,itsuseasapreciousgem,butalsoasaheatsink,asanlowestcompressibility(8.3x10-m2N-l)abrasive,andasinsertsand/orwear-resistantcoatingsforHighestknownvalueofthermalconductivityatroomtemperaturecuttingtools.Obviously,givenitsmanyuniquepropertiesitis(2xlo3Wm-’K-l)possibletoenvisageman
7、yotherpotentialapplicationsforThermalexpansioncoefficientatroomtemperature(0.8xK-l)diamondasanengineeringmaterial,butprogressinimplement-iscomparablewiththatofinvaringmanysuchideashasbeenhamperedbythecomparativeBroadopticalt
