简介：Highlyc-axis-orientedZnOfilmsweredepositedsuccessfullyonthenucleationsidesoffree-standingdiamond(FD)filmsbythedirectcurrent(DC)magnetronsputteringmethod.Theeffectofthesputteringparameters,suchaspower,gaspressureandsputteringplasmacompositionofAr-to-O_2,onthepropertiesofZnOthinfilmswasinvestigatedindetail.X-raydiffraction(XRD)measurementsshowedthat,atasputteringpowerof200W,gaspressureof0.5PaandanAr-to-O_2compositionof1:1,ahigherintensityofthe(002)diffractionpeakandanarrowerfullwidthathalfmaximum(FWHM)weredetectedwhichmeanthighc-axisorientationandhighqualityoftheZnOfilms.ToimprovethequalityoftheZnOfilm,athinZnOlayerwaspre-grownasahomo-bufferlayer.XRDmeasurementsshowedthatthisbufferlayerhadabeneficialeffectonthestructuralandmorphologicalpropertiesofthepost-grownZnOfilm.

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简介：Amodellingstudyisperformedtocomparetheplasmaflowandheattransfercharacteristicsoflow-powerarc-heatedthrusters(arcjets)forthreedifferentpropellants:hydrogen,nitrogenandargon.Theall-speedSIMPLEalgorithmisemployedtosolvethegoverningequations,whichtakeintoaccounttheeffectsofcompressibility,LorentzforceandJouleheating,aswellasthetemperature-andpressure-dependenceofthegasproperties.Thetemperature,velocityandMachnumberdistributionscalculatedwithinthethrusternozzleobtainedwithdifferentpropellantgasesarecomparedforthesamethrusterstructure,dimensions,inlet-gasstagnantpressureandarccurrents.Thetemperaturedistributionsinthesolidregionoftheanode-nozzlewallarealsogiven.Itisfoundthattheflowandenergyconversionprocessesinthethrusternozzleshowmanysimilarfeaturesforallthreepropellants.Forexample,thepropellantisheatedmainlyinthenear-cathodeandconstrictorregion,withthehighestplasmatemperatureappearingnearthecathodetip;theflowtransitionfromthesubsonictosupersonicregimeoccurswithintheconstrictorregion;thehighestaxialvelocityappearsinsidethenozzle;andmostoftheinputpropellantflowstowardsthethrusterexitthroughthecoolergasregionneartheanode-nozzlewall.However,sincethepropertiesofhydrogen,nitrogenandargon,especiallytheirmolecularweights,specificenthalpiesandthermalconductivities,aredifferent,thereareappreciabledifferencesinarcjetperformance.Forexample,comparedtotheothertwopropellants,thehydrogenarcjetthrustershowsahigherplasmatemperatureinthearcregion,andhigheraxialvelocitybutlowertemperatureatthethrusterexit.Correspondingly,thehydrogenarcjetthrusterhasthehighestspecificimpulseandarcvoltageforthesameinletstagnantpressureandarccurrent.Thepredictionsofthemodellingarecomparedfavourablywithavailableexperimentalresults.