1、Designation: E 2089 00 (Reapproved 2006)Standard Practices forGround Laboratory Atomic Oxygen Interaction Evaluation ofMaterials for Space Applications1This standard is issued under the fixed designation E 2089; the number immediately following the designation indicates the year oforiginal adoption
2、or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 The intent of these practices is to define atomic oxygenexposure procedures
3、that 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
4、 atomic oxygen exposure facility but simply specifyprocedures that can be applied to a wide variety of facilities.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate s
5、afety and health practices and determine the applica-bility of regulatory limitations prior to use.1.4 The values stated in SI units are to be regarded as thestandard.2. Terminology2.1 Definitions:2.1.1 atomic oxygen erosion yieldthe volume of a mate-rial that is eroded by atomic oxygen per incident
6、 oxygen 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 r
7、eported 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 Ea
8、rth orbit.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 t
9、he test material, cm3/atomfk= effective flux, atoms/cm2/sFk= effective fluence, total atoms/cm2DMk= 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
10、 erosion 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
11、.3 Compare 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 testin
12、g because 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
13、exposure 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). The1These practices are under the jurisdiction of ASTM Committee E21 on SpaceSimulation and Applications of
14、 Space Technology and are the direct responsibilityof Subcommittee E21.04 on Space Simulation Test Methods.Current edition approved April 1, 2006. Published April 2006. Originallyapproved in 2000. Last previous edition approved in 2000 as E 2089 00.1Copyright ASTM International, 100 Barr Harbor Driv
15、e, PO Box C700, West Conshohocken, PA 19428-2959, United States.atomic oxygen effective flux (in atomscm2s1) and effectivefluence (in atoms/cm2) for polyimide Kapton H or HN shouldbe reported along with the mass or thickness loss relative topolyimide Kapton H or HN for the test material, TFE-fluoroc
16、arbon FEP, PE, and PG. For atomic oxygen interactiontesting at effective fluences beyond 2 3 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 thusresulting in incorre
17、ct 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, the recommended stand
18、ard 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 polymer witness, can us
19、e 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 would be used in space.
20、 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 and atomic oxygen pro
21、tection 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 materialswith protective coatings
22、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 tominimize abrasion, contamin
23、ation 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 are lint-free to care
24、fully 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 sample, coveringan area
25、 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 microwave excitation region of
26、 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 this configuration before
27、 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 use of thin polyester
28、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, edge exposure of the sam
29、plesand 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 quantities ofwater or o
30、ther 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 millitorr for a durationo
31、f 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 cross-contaminate eachot
32、her, 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 dehydrationchambers. Reduction of u
33、ncertainty 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 mass loss of the atomic
34、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 outside this range, measur
35、e 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 test sample has an at
36、omic 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 erosionE 2089 00 (2006)2yield data is available. If such in-space data is not available,then
37、 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 3 1024cm3/atom.5.6.1.2 It is recommended that where physically possible,the atomic oxygen fluence witness material be exposed toatomic oxygen simultan
38、eously 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 thinto survive lon
39、g 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 facilities thanin space. The
40、refore, 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 simulta-neous or sequential exposure of pyrolytic graphite and theKapton, and will enable the effective fluence to be calculated interm
41、s 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 allow com-parisons to
42、 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 experiencesome spatial flux variat
43、ion depending on how the atomicoxygen is formed. Minimization of errors in effective atomicoxygen fluence will be achieved if witness samples are placedas close as possible to the same location as the test sample, andthat the exposed surfaces of the test sample and witness sampleare identical in siz
44、e and orientation. The use of witness samplesof the 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 com-pare witness samples with previously exposed witness samplesthat hav
45、e 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 effective fluxfor t
46、he 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 samples generally canbe
47、 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. Whenwitness samples ar
48、e 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 techniques ifthe exposure
49、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 with the surface during th
