作者:标准资料网 时间:2024-04-28 04:48:55   浏览:9554   来源:标准资料网

【英文标准名称】:StandardTestMethodforNormalSpectralEmittanceatElevatedTemperaturesofNonconductingSpecimens
【原文标准名称】:升温时非传导样品的正常光谱发射的标准试验方法
【标准号】:ASTME423-1971(2008)
【标准状态】:现行
【国别】:美国
【发布日期】:1971
【实施或试行日期】:
【发布单位】:美国材料与试验协会(US-ASTM)
【起草单位】:E21.04
【标准类型】:(TestMethod)
【标准水平】:()
【中文主题词】:
【英文主题词】:emittance;infraredemittance;materialradiativeproperty;radiativeheattransfer;spacecraftthermalcontrol;spectralnormalemittance;thermalradiation
【摘要】:Thesignificantfeaturesaretypifiedbyadiscussionofthelimitationsofthetechnique.Withthedescriptionandarrangementgiveninthefollowingportionsofthistestmethod,theinstrumentwillrecorddirectlythenormalspectralemittanceofaspecimen.However,thefollowingconditionsmustbemetwithinacceptabletolerance,orcorrectionsmustbemadeforthespecifiedconditions.Theeffectivetemperaturesofthespecimenandblackbodymustbewithin1Kofeachother.Practicallimitationsarise,however,becausethetemperatureuniformitiesareoftennotbetterthanafewkelvins.Theopticalpathlengthinthetwobeamsmustbeequal,or,preferably,theinstrumentshouldoperateinanonabsorbingatmosphere,inordertoeliminatetheeffectsofdifferentialatmosphericabsorptioninthetwobeams.Measurementsinairareinmanycasesimportant,andwillnotnecessarilygivethesameresultsasinavacuum,thustheequalityoftheopticalpathsfordual-beaminstrumentsbecomesverycritical.Note48212;Verycarefulopticalalignmentofthespectrophotometerisrequiredtominimizedifferencesinabsorptancealongthetwopathsoftheinstrument,andcarefuladjustmentofthechoppertimingtoreducex201C;cross-talkx201D;(theoverlapofthereferenceandsamplesignals)aswellasprecautionstoreducestrayradiationinthespectrophotometerarerequiredtokeepthezerolineflat.Withthebestadjustment,thex201C;100%linex201D;willbeflattowithin3%.Front-surfacemirroropticsmustbeusedthroughout,exceptfortheprisminprismmonochromators,anditshouldbeemphasizedthatequivalentopticalelementsmustbeusedinthetwobeamsinordertoreduceandbalanceattenuationofthebeamsbyabsorptionintheopticalelements.ItisrecommendedthatopticalsurfacesbefreeofSiO2andSiOcoatings:MgF2maybeusedtostabilizemirrorsurfacesforextendedperiodsoftime.Theopticalcharacteristicsofthesecoatingsarecritical,butcanberelaxedifallopticalpathsarefixedduringmeasurementsortheincidentanglesarenotchangedbetweenmodesofoperation(during0%line,100%line,andsamplemeasurements).Itisrecommendedthatallopticalelementsbeadequatelyfilledwithenergy.Thesourceandfieldaperturesofthetwobeamsmustbeequalinordertoensurethatradiantfluxinthetwobeamscomparedbytheapparatuswillpertaintoequalareasofthesourcesandequalsolidanglesofemission.Insomecasesitmaybedesirabletodefinethesolidangleofthesourceandsamplewhencomparingalternativemeasurementtechniques.Theresponseofthedetector-amplifiersystemmustvarylinearlywiththeincidentradiantflux,ormustbecalibratedforlinearity,andcorrectionsmadeforobserveddeviationsfromlinearity.1.1Thistestmethoddescribesanaccuratetechniqueformeasuringthenormalspectralemittanceofelectricallynonconductingmaterialsinthetemperaturerangefrom1000to1800K,andatwavelengthsfrom1to35x03BC;m.Itisparticularlysuitableformeasuringthenormalspectralemittanceofmaterialssuchasceramicoxides,whichhaverelativelylowthermalconductivityandaretranslucenttoappreciabledepths(severalmillimetres)belowthesurface,butwhichbecomeessentiallyopaqueatthicknessesof10mmorless.1.2Thistestmethodrequiresexpensiveequipmentandratherelaborateprecautions,butproducesdatathatareaccuratetowithinafewpercent.Itisparticularlysuitableforresearchlaboratories,wherethehighestprecisionandaccuracyaredesired,andisnotrecommendedforroutineproductionoracceptan......
【中国标准分类号】:V10
【国际标准分类号】:49_025_01
【页数】:9P.;A4
【正文语种】:英语