Deformation behavior and joining of a MgF2 optical ceramic

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1、JournaloftheEuropeanCeramicSociety27(2007)33713376DeformationbehaviorandjoiningofaMgF2opticalceramicC.Lorenzo-Martina,D.Singhb,∗,J.Johnsonb,J.L.RoutbortaaEnergySystemsDivision,ArgonneNationalLaboratory,Bldg.212/E206,9700S.CassAvenue,Argonne,IL60439,USAbNuclearEngineeringDivision,ArgonneNation

2、alLaboratory,Argonne,IL60439,USAAvailableonline28March2007AbstractCompressivedeformationbehaviorofapolycrystallinemagnesiumfluoride(MgF2)ceramicwasinvestigatedattemperaturesrangingfrom760to830◦Cinanargonatmosphereatstrainratesbetween2×10−6and4×10−5s−1.Steady-stateflowstressesincreasedwithincrea

3、singstrainratesandrangedbetween2and38MPa.Stressexponentsof≈1.4±0.2weredeterminedattemperatures>760◦C,indicativeofaviscousdiffusion-controlleddeformationmechanism.Activationenergy,determinedfromflowstressasafunctionoftemperature,ataconstantstrainrate,was≈476±60kJ/mol.Self-joiningbyplasticdeform

4、ationofMgFwasdemonstratedat830◦Catastrainrateof5×10−6s−1.Thejoinedsamples2werecharacterizedbyopticaltransmissionmeasurementsandtheirtransmittivitywas≈80%oftheunjoinedsampleinthe2.58mwavelengthrange.©2007ElsevierLtd.Allrightsreserved.Keywords:Magnesiumfluoride;Opticalproperties;Creep1.Introduc

5、tionalithiumfluoride(LiF)interlayer.5DiffusionbondingentailedapplyingathinfilmofLiFonthematingsurfacesofthepiecesPolycrystallinemagnesiumfluoride(MgF2)isalmosttrans-beingjoinedandmaintainingaconstantcompressivestressforparentintheinfrared(IR)wavelengthregime(28m).1,2Due>3hat550575◦C.Withoutanyi

6、nterlayer,diffusionbondingtothisuniqueproperty,MgF2hasapplicationsforIRwin-wasaccomplishedbyapplyingconstantpressureat800830◦Cdowsandcoatingsinopticalinstruments,spacevehicles,andforabout6h4.Limitationsofthisprocessaretwo-fold:(a)longfrontaldomesinheat-seekingmissiles.13Magnesiumfluorideholdti

7、mesatelevatedtemperatureswhichcanresultingrainisanexcellentcandidateforthermallensingbecauseithasonegrowthand(b)useofanextraneousinterfacematerial.Bothoflowesttemperaturedependentrefractiveindexdistortions.3factorscancausedegradationoftheopti