1、Designation: E2089 00 (Reapproved 2014)E2089 15Standard 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 ado
2、ption or, 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 oxygen exposure proce
3、dures that are intended to minimize variability inresults within any specific atomic oxygen exposure facility as well as contribute to the understanding of the differences in theresponse of materials when tested in different facilities.1.2 These practices are not intended to specify any particular t
4、ype of atomic 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 the standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It i
5、s the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Terminology2.1 Definitions:2.1.1 atomic oxygen erosion yieldthe volume of a material that is eroded by atomic oxygen per inci
6、dent oxygen atom reportedin cm3/atom.2.1.2 atomic oxygen fluencethe arrival of atomic oxygen to a surface reported in atoms/cm22.1.3 atomic oxygen fluxthe arrival rate of atomic oxygen to a surface reported in atomscm2s1.2.1.4 effective atomic oxygen fluencethe total arrival of atomic oxygen to a su
7、rface reported in atoms/cm2, which would causethe observed amount of erosion if the sample was exposed in low Earth orbit.2.1.5 effective atomic oxygen fluxthe arrival rate of atomic oxygen to a surface reported in atomscm2 s1, which would causethe observed amount of erosion if the sample was expose
8、d in low Earth orbit.2.1.6 witness materials or samplesmaterials or samples used 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 = e
9、rosion yield of the test 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 be available:3.1.1 Material atomic oxygen erosion characteristics.3.
10、1.2 An atomic oxygen erosion comparison of four well-characterized polymers.1 These practices are under the jurisdiction of ASTM Committee E21 on Space Simulation and Applications of Space Technology and are the direct responsibility ofSubcommittee E21.04 on Space Simulation Test Methods.Current edi
11、tion approved April 1, 2014Oct. 1, 2015. Published April 2014October 2015. Originally approved in 2000. Last previous edition approved in 20002014 asE2089 00(2006).(2014). DOI: 10.1520/E2089-00R14.10.1520/E2089-15.This document is not an ASTM standard and is intended only to provide the user of an A
12、STM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as publishe
13、d by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2 The resulting data are useful to:3.2.1 Compare the atomic oxygen durability of spacecraft materials exposed to the low Earth orbit
14、al environment.3.2.2 Compare the atomic oxygen erosion behavior between various ground laboratory facilities.3.2.3 Compare the atomic oxygen erosion behavior between ground laboratory facilities and in-space exposure.3.2.4 Screen materials being considered for low Earth orbital spacecraft applicatio
15、n. However, caution should be exercised inattempting to predict in-space behavior based on ground laboratory testing because of differences in exposure environment andsynergistic effects.4. Test Specimen4.1 In addition to the material to be evaluated for atomic oxygen interaction, the following four
16、 standard witness materialsshould be exposed in the same facility using the same operating conditions and duration exposure within a factor of 3, as the testmaterial: KaptonKapton(R)2 polyimide H or HN, TFE-fluorocarbon HN polyimide, tetrafluoroethylene (TFE)-fluorocarbonfluorinated ethylene propyle
17、ne (FEP), low-density polyethylene (PE), and pyrolytic graphite (PG). The atomic oxygen effectiveflux (in atomscm2s1) and effective fluence (in atoms/cm2) for polyimide Kapton H or HN polyimide should be reported alongwith the mass or thickness loss relative to polyimide Kapton H or HN polyimide for
18、 the test material, TFE-fluorocarbon FEP, PE,and PG. For atomic oxygen interaction testing at effective fluences beyond 2 1021 atoms/cm2, polyimide Kapton H should beused and not Kapton H polyimide has been recommended in the past, however E. I. du Pont de Nemours and Company (DuPont(TM2Kapton HN be
19、cause Kapton HN contains atomic oxygen resistant ) has discontinued its manufacture. Kapton H polyimideis the preferred replacement, but Kapton HN polyimide contains atomic oxygen-resistant inorganic particles which begin to protectthe underlying polyimide, thus resulting in incorrect fluence predic
20、tion.an atomic oxygen erosion yield in low Earth orbit (2.81 10-24 cm3/atom) that is slightly less than that of Kapton H (3.00 10-24 cm3/atom) (1)3.4.2 It is not necessary to test the four standard witness samples for each material exposure if previous data exists at the sameexposure conditions and
21、if the fluence for the test sample is within a factor of 3 of the standard witness exposure. When possible,the recommended standard witness polymer materials should be 0.05 mm thick and of a diameter greater than 5 mm. It isrecommended that the pyrolytic graphite witness sample be 2 mm thick and of
22、a diameter greater than 5 mm. High-fluence tests,which may erode through the full thickness of the standard polymer witness, can use the recommended thickness sample materialsby stacking several layers of the polymer on top of each other.5. Procedure5.1 Sample Preparation:5.1.1 Cleaning:5.1.1.1 The
23、samples to be evaluated for atomic oxygen interactions should be chemically representative of materials that wouldbe used in space. Thus, the surface chemistry of the samples should not be altered by exposure to chemicals or cleaning solutionswhich would not be representatively used on the functiona
24、l materials to be used in space.5.1.1.2 Wiping samples or washing them may significantly alter surface chemistry and atomic oxygen protection characteristicsof materials, and is therefore not recommended. However, if the typical use in space will require preflight solvent cleaning, thenperform such
25、cleaning to simulate actual surface conditions expected.5.2 HandlingThe atomic oxygen durability of materials with protective coatings may be significantly altered as a result ofmechanical damage associated with handling. In addition, unprotected materials can become contaminated by handling, result
26、ingin anomalous consequences of atomic oxygen exposure. It is recommended that samples be handled such as to minimize abrasion,contamination and flexure. The use of soft fluoropolymer tweezers is recommended for handling polymeric films with protectivecoatings. For samples too heavy to be safely hel
27、d with tweezers, use clean vinyl, latex, or other gloves which will not allow fingeroils to soak through and which are lint-free to carefully handle the samples.5.3 Exposure Area Control:5.3.1 MaskingFrequently it is desirable to limit the exposure of atomic oxygen to one side of a material or a lim
28、ited area onone side of the material. This can be done by wrapping metal foil (such as aluminum foil) around the sample, covering an areawith a sacrificial polymer (such as Kapton), a polyimide), salt-spraying to produce sites of atomic oxygen protection, or by usingglass to cover areas not to be ex
29、posed. It is recommended that the protective covering be in intimate contact with the material toprevent partial exposure of the masked areas. When using metal foil within the RF or microwave excitation region of an atomicoxygen source, it is likely that electromagnetic interactions could take place
30、 between the metal and the plasma that could causeanomalous atomic oxygen fluxes or shielding from charged species, or both. It is important to expose the four standard witnesscoupons in this configuration before any other testing to determine the effects of the masking on the atomic oxygen flux.5.3
31、.2 CladdingSamples which are coated with protective coatings on one side can be clad together by means of adhesives toallow the protective coating to be exposed on both sides of the sample. The use of thin polyester adhesives (or other non-silicone2 Kapton(R) and DuPont (TM) are trademarks or regist
32、ered trademarks of E. I. DuPont de Nemours and Company.3 The boldface numbers in parentheses refer to a list of references at the end of this standard.E2089 152adhesive) is recommended to perform such cladding. The use of silicone adhesives should be avoided because of potential siliconecontaminatio
33、n of the sample. Although cladding allows samples to be tested with the protective coatings on both faces, edgeexposure of the samples and their adhesive does occur and should be accounted for in calculating erosion characteristics of thedesired surfaces.5.4 Dehydration and Outgassing (for Samples U
34、ndergoing Weight Measurement)Because most nonmetals and nonceramicmaterials contain significant fractional quantities of water or other volatiles, or both, it is recommended that these types of materialsbe vacuum-dehydrated before weighing to eliminate errors in weight because of moisture loss. Dehy
35、drate samples of a thicknessless than or equal to 0.127 mm (5 mils) in a vacuum of a pressure less than 200 millitorr for a duration of 48 h before sampleweighing to ensure that the samples retain negligible absorbed water. Dehydrate and weigh thicker samples periodically untilweight loss indicates
36、that no further water is being lost. Dehydrate multiple samples in the same vacuum chamber provided theydo not cross-contaminate each other, and that they are not of sufficient quantity so as to inhibit uniform dehydration of all thesamples.5.5 WeighingBecause hydration occurs quickly after removal
37、of samples from vacuum, weighing the samples should occurwithin five minutes of removal from vacuum dehydration chambers. Reduction of uncertainty associated with moisture uptake canbe minimized by weighing the samples at measured intervals following removal from vacuum and back extrapolating to the
38、 massat time of removal from vacuum. Weigh samples using a balance whose sensitivity is capable of measuring the mass loss of theatomic oxygen fluence witness samples. For 2.54-cm-diameter by 0.127-mm-thick Kapton H or HN polyimide fluence witnesssamples, a balance sensitivity of 1 mg is acceptable
39、for effective fluences of at least 1019 atoms/cm2. Weigh the samples at roomtemperature (20 to 25C). If the temperature is outside this range, measure and record at the time 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
40、not have any protective coating, then use polyimide Kapton H or HN samplesto determine the effective atomic oxygen fluence. If the test sample has an atomic oxygen protective coating, then test anunprotected sample of the substrate material as well. The unprotected sample can also be used to determi
41、ne the effective atomicoxygen fluence provided that in-space erosion yield data is available. If such in-space data is not available, then use a sample ofpolyimide Kapton H or HN should be used for determination of effective atomic oxygen fluence assuming an in-space erosion yieldof 3.0 1024 cm3/ato
42、m./atom or 2.81 1024 cm3/atom respectively.5.6.1.2 It is recommended that where physically possible, the atomic oxygen fluence witness material be exposed to atomicoxygen simultaneously with the test samples to enable calculation of the effective atomic oxygen fluence. If chamber geometryprevents th
43、is, expose a fluence witness coupon just prior to or immediately after the test sample. If high-fluence exposure isnecessary, quite often polymeric sheets are too thin to survive long exposures. Therefore, thick coupons of polyimide or graphiteare suggested to be used for high-fluence weight or thic
44、kness loss measurements. The atomic oxygen erosion yield of pyrolyticgraphite relative to polyimide Kapton H or HN is different in some ground laboratory facilities than in space. Therefore, it isnecessary to convert the mass loss or thickness loss of the pyrolytic graphite to the equivalent loss of
45、 polyimide Kapton H. Thiscan be accomplished by simultaneous or sequential exposure of pyrolytic graphite and the Kapton, and will enable the effectivefluence to be calculated in terms of Kapton effective fluence, which is the accepted standard.5.6.1.3 It is recommended that, periodically, samples o
46、f Kapton H or HN, TFE-fluorocarbon FEP, polyethylene, and pyrolyticgraphite be exposed to atomic oxygen in the test chamber to verify operational consistency and to allow comparisons to be madebetween this test facility, space, and other ground-based systems. Report this data along with any test dat
47、a so that test results canbe compared more easily.5.6.2 Test, Standard Witness, and Fluence Witness Sample Position and OrientationFacilities typically experience somespatial flux variation depending on how the atomic oxygen is formed. Minimization of errors in effective atomic oxygen fluencewill be
48、 achieved if witness samples are placed as close as possible to the same location as the test sample, and that the exposedsurfaces of the test sample and witness sample are identical in size and orientation. The use of witness samples of the same size,position, and orientation as the test samples is
49、 recommended.5.6.3 Inspection and Validation of Standard Witness and Fluence Witness Sample ErosionVisibly inspect and compare witnesssamples with previously exposed witness samples that have demonstrated acceptable performance to validate that contaminationof the surface of the sample has not occurred. Contamination can look like oil spots on the surface, a protective thin film, or otheroptical deviation from a normally diffuse reflecting exposed surface. Compare the effective flux for the witness sample with thatfrom tests previously known t
