1、Designation: E2089 00 (Reapproved 2014)Standard Practices forGround Laboratory Atomic Oxygen Interaction Evaluation ofMaterials for Space Applications1This standard is issued under the fixed designation E2089; the number immediately following the designation indicates the year oforiginal adoption or
2、, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 The intent of these practices is to define atomic oxygenexposure procedures tha
3、t are intended to minimize variabilityin results within any specific atomic oxygen exposure facilityas well as contribute to the understanding of the differences inthe response of materials when tested in different facilities.1.2 These practices are not intended to specify any particu-lar type of at
4、omic oxygen exposure facility but simply specifyprocedures that can be applied to a wide variety of facilities.1.3 The values stated in SI units are to be regarded as thestandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is therespon
5、sibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Terminology2.1 Definitions:2.1.1 atomic oxygen erosion yieldthe volume of a materialthat is eroded by atomic oxygen per incident oxyg
6、en atomreported in cm3/atom.2.1.2 atomic oxygen fluencethe arrival of atomic oxygento a surface reported in atoms/cm22.1.3 atomic oxygen fluxthe arrival rate of atomic oxygento a surface reported in atomscm2s1.2.1.4 effective atomic oxygen fluencethe total arrival ofatomic oxygen to a surface report
7、ed in atoms/cm2, whichwould cause the observed amount of erosion if the sample wasexposed in low Earth orbit.2.1.5 effective atomic oxygen fluxthe arrival rate of atomicoxygen to a surface reported in atomscm2s1, which wouldcause the observed amount of erosion if the sample wasexposed in low Earth o
8、rbit.2.1.6 witness materials or samplesmaterials or samplesused to measure the effective atomic oxygen flux or fluence.2.2 Symbols:Ak= exposed area of the witness sample, cm2As= exposed area of the test sample, cm2Ek= in-space erosion yield of the witness material, cm3/atomEs= erosion yield of the t
9、est material, cm3/atomfk= effective flux, atoms/cm2/sFk= effective fluence, total atoms/cm2Mk= mass loss of the witness coupon, g3. Significance and Use3.1 These practices enable the following information to beavailable:3.1.1 Material atomic oxygen erosion characteristics.3.1.2 An atomic oxygen eros
10、ion comparison of four well-characterized polymers.3.2 The resulting data are useful to:3.2.1 Compare the atomic oxygen durability of spacecraftmaterials exposed to the low Earth orbital environment.3.2.2 Compare the atomic oxygen erosion behavior betweenvarious ground laboratory facilities.3.2.3 Co
11、mpare the atomic oxygen erosion behavior betweenground laboratory facilities and in-space exposure.3.2.4 Screen materials being considered for low Earthorbital spacecraft application. However, caution should beexercised in attempting to predict in-space behavior based onground laboratory testing bec
12、ause of differences in exposureenvironment and synergistic effects.4. Test Specimen4.1 In addition to the material to be evaluated for atomicoxygen interaction, the following four standard witness mate-rials should be exposed in the same facility using the sameoperating conditions and duration expos
13、ure within a factor of3, as the test material: Kapton polyimide H or HN, TFE-fluorocarbon fluorinated ethylene propylene (FEP), low-density polyethylene (PE), and pyrolytic graphite (PG). Theatomic oxygen effective flux (in atomscm2s1) and effectivefluence (in atoms/cm2) for polyimide Kapton H or HN
14、 shouldbe reported along with the mass or thickness loss relative to1These practices are under the jurisdiction of ASTM Committee E21 on SpaceSimulation and Applications of Space Technology and are the direct responsibilityof Subcommittee E21.04 on Space Simulation Test Methods.Current edition appro
15、ved April 1, 2014. Published April 2014. Originallyapproved in 2000. Last previous edition approved in 2000 as E2089 00(2006).DOI: 10.1520/E2089-00R14.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1polyimide Kapton H or HN for the te
16、st material, TFE-fluorocarbon FEP, PE, and PG. For atomic oxygen interactiontesting at effective fluences beyond 2 1021atoms/cm2,polyimide Kapton H should be used and not Kapton HNbecause Kapton HN contains atomic oxygen resistant inorganicparticles which begin to protect the underlying polyimide th
17、usresulting in incorrect fluence prediction.4.2 It is not necessary to test the four standard witnesssamples for each material exposure if previous data exists atthe same exposure conditions and if the fluence for the testsample is within a factor of 3 of the standard witness exposure.When possible,
18、 the recommended standard witness polymermaterials should be 0.05 mm thick and of a diameter greaterthan 5 mm. It is recommended that the pyrolytic graphitewitness sample be 2 mm thick and of a diameter greater than5 mm. High-fluence tests, which may erode through the fullthickness of the standard p
19、olymer witness, can use the recom-mended thickness sample materials by stacking several layersof the polymer on top of each other.5. Procedure5.1 Sample Preparation:5.1.1 Cleaning:5.1.1.1 The samples to be evaluated for atomic oxygeninteractions should be chemically representative of materialsthat w
20、ould be used in space. Thus, the surface chemistry of thesamples should not be altered by exposure to chemicals orcleaning solutions which would not be representatively used onthe functional materials to be used in space.5.1.1.2 Wiping samples or washing them may significantlyalter surface chemistry
21、 and atomic oxygen protection charac-teristics of materials, and is therefore not recommended.However, if the typical use in space will require preflightsolvent cleaning, then perform such cleaning to simulate actualsurface conditions expected.5.2 HandlingThe atomic oxygen durability of materialswit
22、h protective coatings may be significantly altered as a resultof mechanical damage associated with handling. In addition,unprotected materials can become contaminated by handling,resulting in anomalous consequences of atomic oxygen expo-sure. It is recommended that samples be handled such as tominim
23、ize abrasion, contamination and flexure. The use of softfluoropolymer tweezers is recommended for handling poly-meric films with protective coatings. For samples too heavy tobe safely held with tweezers, use clean vinyl, latex, or othergloves which will not allow finger oils to soak through andwhich
24、 are lint-free to carefully handle the samples.5.3 Exposure Area Control:5.3.1 MaskingFrequently it is desirable to limit the expo-sure of atomic oxygen to one side of a material or a limited areaon one side of the material. This can be done by wrappingmetal foil (such as aluminum foil) around the s
25、ample, coveringan area with a sacrificial polymer (such as Kapton), or by usingglass to cover areas not to be exposed. It is recommended thatthe protective covering be in intimate contact with the materialto prevent partial exposure of the masked areas. When usingmetal foil within the RF or microwav
26、e excitation region of anatomic oxygen source, it is likely that electromagnetic interac-tions could take place between the metal and the plasma thatcould cause anomalous atomic oxygen fluxes or shielding fromcharged species, or both. It is important to expose the fourstandard witness coupons in thi
27、s configuration before any othertesting to determine the effects of the masking on the atomicoxygen flux.5.3.2 CladdingSamples which are coated with protectivecoatings on one side can be clad together by means ofadhesives to allow the protective coating to be exposed on bothsides of the sample. The
28、use of thin polyester adhesives (orother non-silicone adhesive) is recommended to perform suchcladding. The use of silicone adhesives should be avoidedbecause of potential silicone contamination of the sample.Although cladding allows samples to be tested with theprotective coatings on both faces, ed
29、ge exposure of the samplesand their adhesive does occur and should be accounted for incalculating erosion characteristics of the desired surfaces.5.4 Dehydration and Outgassing (for Samples UndergoingWeight Measurement)Because most nonmetals and nonce-ramic materials contain significant fractional q
30、uantities ofwater or other volatiles, or both, it is recommended that thesetypes of materials be vacuum-dehydrated before weighing toeliminate errors in weight because of moisture loss. Dehydratesamples of a thickness less than or equal to 0.127 mm (5 mils)in a vacuum of a pressure less than 200 mil
31、litorr for a durationof 48 h before sample weighing to ensure that the samplesretain negligible absorbed water. Dehydrate and weigh thickersamples periodically until weight loss indicates that no furtherwater is being lost. Dehydrate multiple samples in the samevacuum chamber provided they do not cr
32、oss-contaminate eachother, and that they are not of sufficient quantity so as to inhibituniform dehydration of all the samples.5.5 WeighingBecause hydration occurs quickly after re-moval of samples from vacuum, weighing the samples shouldoccur within five minutes of removal from vacuum dehydrationch
33、ambers. Reduction of uncertainty associated with moistureuptake can be minimized by weighing the samples at measuredintervals following removal from vacuum and back extrapo-lating to the mass at time of removal from vacuum. Weighsamples using a balance whose sensitivity is capable ofmeasuring the ma
34、ss loss of the atomic oxygen fluence witnesssamples. For 2.54-cm-diameter by 0.127-mm-thick Kapton Hpolyimide fluence witness samples, a balance sensitivity 1 mgis acceptable for effective fluences of at least 1019atoms/cm2.Weigh the samples at room temperature (20 to 25C). If thetemperature is outs
35、ide this range, measure and record at thetime of weighing.5.6 Effective Fluence Prediction:5.6.1 Fluence Witness Samples:5.6.1.1 If the test sample is a material that does not have anyprotective coating, then use polyimide Kapton H or HNsamples to determine the effective atomic oxygen fluence. Ifthe
36、 test sample has an atomic oxygen protective coating, thentest an unprotected sample of the substrate material as well.The unprotected sample can also be used to determine theeffective atomic oxygen fluence provided that in-space erosionE2089 00 (2014)2yield data is available. If such in-space data
37、is not available,then use a sample of polyimide Kapton H or HN should beused for determination of effective atomic oxygen fluenceassuming an in-space erosion yield of 3.0 1024cm3/atom.5.6.1.2 It is recommended that where physically possible,the atomic oxygen fluence witness material be exposed toato
38、mic oxygen simultaneously with the test samples to enablecalculation of the effective atomic oxygen fluence. If chambergeometry prevents this, expose a fluence witness coupon justprior to or immediately after the test sample. If high-fluenceexposure is necessary, quite often polymeric sheets are too
39、 thinto survive long exposures. Therefore, thick coupons of poly-imide or graphite are suggested to be used for high-fluenceweight or thickness loss measurements. The atomic oxygenerosion yield of pyrolytic graphite relative to polyimide KaptonH or HN is different in some ground laboratory facilitie
40、s thanin space. Therefore, it is necessary to convert the mass loss orthickness loss of the pyrolytic graphite to the equivalent loss ofpolyimide Kapton H. This can be accomplished by simultane-ous or sequential exposure of pyrolytic graphite and theKapton, and will enable the effective fluence to b
41、e calculated interms of Kapton effective fluence, which is the acceptedstandard.5.6.1.3 It is recommended that, periodically, samples ofKapton H or HN, TFE-fluorocarbon FEP, polyethylene, andpyrolytic graphite be exposed to atomic oxygen in the testchamber to verify operational consistency and to al
42、low com-parisons to be made between this test facility, space, and otherground-based systems. Report this data along with any test dataso that test results can be compared more easily.5.6.2 Test, Standard Witness, and Fluence Witness SamplePosition and OrientationFacilities typically experience some
43、spatial flux variation depending on how the atomic oxygen isformed. Minimization of errors in effective atomic oxygenfluence will be achieved if witness samples are placed as closeas possible to the same location as the test sample, and that theexposed surfaces of the test sample and witness sample
44、areidentical in size and orientation. The use of witness samples ofthe same size, position, and orientation as the test samples isrecommended.5.6.3 Inspection and Validation of Standard Witness andFluence Witness Sample ErosionVisibly inspect and comparewitness samples with previously exposed witnes
45、s samples thathave demonstrated acceptable performance to validate thatcontamination of the surface of the sample has not occurred.Contamination can look like oil spots on the surface, aprotective thin film, or other optical deviation from a normallydiffuse reflecting exposed surface. Compare the ef
46、fective fluxfor the witness sample with that from tests previously known tobe acceptable which were performed in the same facility toensure that neither contamination nor anomalous operation hasoccurred.5.6.4 Erosion MeasurementMeasurement of atomic oxy-gen erosion of test samples and witness sample
47、s generally canbe accomplished by weight loss or thickness loss measure-ments.5.6.4.1 Weight LossWeigh witness samples within fiveminutes of removal from the vacuum chamber. Remove onlyone sample at a time for weighing. The rest should remainunder vacuum to minimize rehydration mass increases. Whenw
48、itness samples are of the same chemistry as the substrate ofprotected samples, it is important to weigh both samples asclose as possible to the same time interval after removal fromvacuum.5.6.4.2 Thickness LossWitness coupon material loss canalso be measured using various surface profiling technique
49、s ifthe exposure area is too small for accurate weight measure-ments to be taken. Profiling can be accomplished by stylusprofiling, scanning atomic force microscopy, or other recessionmeasurement techniques. Take care when exposing samples toatomic oxygen which will be subsequently used for profilingmeasurements that a portion of the original surface is keptintact and that a clear step exists between the original surfaceand the atomic oxygen exposed portion. This requires that athin (0.2 mm thick) removable mask be used that is inintimate contact wit
