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A study of the reaction characteristics and mechanism of Kapton in a plasma-type ground-based atomic oxygen effects simulation facility
Journal of Physics D: Applied Physics
Abstract
Kapton, a commonly used spacecraft material, is studied to investigate the
atomic oxygen (AO) erosion effects in a plasma-type ground-based AO
effects simulation facility. The samples before and after the experiments are
compared in aspect, mass and surface morphology. The reaction characteristics of
the material in the facility are obtained. The contribution of AO and
ionic oxygen to mass loss in the sample and the reaction mechanism between the different
particles and samples are analysed. It is concluded that neutral
AO is the major cause of material erosion and mass loss and that the
collision of energetic ions may accelerate the oxidation reaction.
... High-vacuum AO functionalization of these bitty films was performed in the ground-based AO effect simulation facility in Beijing University of Aeronautics and Astronautics (BUAA) (Zhao et al. 2001). The facility was a filament discharge plasma-type ground-based AO effect simulation facility for simulating low earth orbit environment (Zhao et al. 2001). ...
... High-vacuum AO functionalization of these bitty films was performed in the ground-based AO effect simulation facility in Beijing University of Aeronautics and Astronautics (BUAA) (Zhao et al. 2001). The facility was a filament discharge plasma-type ground-based AO effect simulation facility for simulating low earth orbit environment (Zhao et al. 2001). The filament was heated to a high temperature by current. ...
... ? could be as high as 15 eV (Zhao et al. 2001). AO exposure experiments were carried out in the conditions of vacuum pressure of 0.15 Pa, filament discharge voltage of 120 V, and filament discharge current of 140 mA. ...
Though chemical modification of graphene based on Hummers method has been most widely used to tailor its properties and interfacial characteristics, a method which could achieve definitive and controllable groups and properties is still highly required. Here, we demonstrate a high-vacuum oxidation strategy by atomic oxygen (AO) and investigate the AO induced functionalization and wettability transition in films made from basal-defect- and oxide-free graphene dispersions. These graphene-based films are neither graphene nor graphite, but graphene blocks constituted by numerous randomly stacked graphene flakes. It is found that AO induced functionalization of these films through the formation of epoxy groups, sp(3) configuration, ether, and double and triple C-O groups. The films turn to be hydrophilic after exposed to AO. The contact angle increases with AO exposure time. This phenomenon is attributed to the lower surface roughness induced by collision and/or edge erosion of energetic ions to the film surface and is further explained by the Wenzel model. The demonstrated strategy can overcome limitations of Hummers method, provide possibility to gain functionalization and wettability transition in liquid-phase exfoliated basal-defect- and oxide-free graphene in the dry environment, and may extend the study and application of this material in spacecraft in low earth orbit.
... As collision with the plate, the accelerated oxygen positive ions are neutralised via the negative charges and rebounded to form a neutral AO beam with an average kinetic energy of about 5 eV that is analogous to the energy of AO impacting on the surface of spacecraft in space environment. 28,29 The flux of AO was about 6 × 10 15 atoms/cm 2 ·s, which was measured by the standard method of Kapton mass loss. 28 The exposure time of AO is controlled about 180 minutes. ...
... 28,29 The flux of AO was about 6 × 10 15 atoms/cm 2 ·s, which was measured by the standard method of Kapton mass loss. 28 The exposure time of AO is controlled about 180 minutes. The UV irradiation test was performed under the excimer light with the wavelength range of 200 to 450 nm in high vacuum environment (4.0 × 10 −3 Pa) using a mercury xenon lamp. ...
... Ion bombardment is a widely used technique to modify the material characteristics, to attain technological improvement: a) ion beam assistance of a growing film, to vary the optical and mechanical properties [1,2,3]; b) ground simulation of surface damage to components undergoing the Low Earth Orbit Space environment [4,5,6]; c) improvement of the substrate adhesion of metallic and dielectric layers [7,8,9]. A knowledge of the parameters influencing the material property changes, under ion bombardment, is useful in simulating the physical mechanisms which govern the ion and matter interaction. ...
... As a consequence, the ion beam can be considered as a mixture of O 2 + and O + . In the literature, a value of 0.2 is assigned as the ratio O + / O 2 + [4]. For kinetic energies higher than the fragmentation energy (E f = 18.69 eV) [24] the O 2 + ions can break during the collision with the atoms of the target surface. ...
Low energy ions are used for different applications such as ion beam assistance, surface modification of materials, ground simulation of space, etc. In this paper, polyimide (Dupont KaptonTM) sheets were bombarded by an ion beam produced by an End-Hall ion source. The erosion rate, measured at the masking part of the Kapton target, was measured with varying source parameters. Two set of samples were bombarded with argon and oxygen ions. The erosion mechanism was explained by assuming that a low energy ion comes to rest a few monolayers from the Kapton surface. Most of the ion energy is released as phonons and a thermal spike is generated. According to the physics of the SRIM (Stopping Range of Ions in Matter) code, a thermal spike model was developed and compared with the experimental results. Quite good agreement between the calculated and measured erosion rates was found.
... Oxygen-atom corrosion was carried out in the filament-discharge plasma-type atom oxygen effect simulation facility. 30,31 The atom oxygen has strong oxidative reactivity to polymers. Taking Kapton as a standard polymer for oxygen-atom induced corrosion, it has been confirmed that one oxygen atom can induce a volume loss of $3.0 Â 10 À24 cm 3 in Kapton. ...
... Taking Kapton as a standard polymer for oxygen-atom induced corrosion, it has been confirmed that one oxygen atom can induce a volume loss of $3.0 Â 10 À24 cm 3 in Kapton. 30,31 The accumulative oxygen-atom flux was $2.78 Â 10 20 atoms/cm 2 . 21 We examined the surface morphology of the naked membrane and BNNSs-coated membrane before and after oxygen-atom corrosion, as shown in the scanning electron microscopy (SEM) images in Fig. 4. The pristine membrane shows pore structures with tightly stacked thick Nylon fibers (Figs. ...
The research of two-dimensional nanomaterials for anticorrosion applications is just recently burgeoning. Herein, we demonstrate the boron nitride nanosheets (BNNSs) coatings for protecting polymer from oxygen-atom corrosion. High-quality BNNSs, which are produced by an effective fluid dynamics method with multiple exfoliation mechanisms, can be assembled into coatings with controlled thickness by vacuum filtration. After exposed in atom oxygen, the naked polymer is severely corroded with remarkable mass loss, while the BNNSs-coated polymer remains intact. Barrier and bonding effects of the BNNSs are responsible for the coating's protective performance. These preliminary yet reproducible results pave a way for resisting oxygen-atom corrosion.
... The surface change through IPL is a micro-scale change and does not have any effect on the contact angle and consequently the surface energy. Lower contact angle for plasma treated samples can be attributed to the chemical transformations induced by the plasma treatment [18]. Even in the absence of evident alterations at the macroscopic level, the energetic interactions at the surface underwent a remarkable shift due to chemical functionalization [19]. ...
In this investigation, we conducted an extensive analysis of techniques used to modify the surface properties of Kapton® substrate, a crucial material in the field of printed electronics. Our study focused on three primary methods: Intense Pulsed Light (IPL) Laser and Plasma treatment, with the aim of improving Kapton®’s suitability for electronic applications. To evaluate these treatments, we carried out experiments to measure contact angle. Although the IPL treatment didn’t lead to any significant changes in the contact angle, Plasma and Laser treatment produced substantial and noteworthy results. Our research highlights the differing effects of IPL and Plasma and laser treatments on Kapton® surfaces, offering valuable insights to researchers and practitioners in the printed electronics field. This study emphasizes the importance of precise control over treatment parameters and a deep understanding of the techniques, allowing for tailored surface modifications to meet the specific needs of electronic applications.
... Experiments involving Pr, UV, AO, and El irradiation of the hybrid films were performed in ground-based simulation facilities at the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences. For the AO irradiation, the average kinetic energy was approximately 5 eV, which is analogous to the energy of AO impacting the surface of a spacecraft in a space environment 26,27 . The flux of AO was approximately 6 × 10 15 atoms cm 2 s −1 , which was measured via the standard method of Kapton mass loss. ...
In this paper, we investigated the effect of space irradiation on the lubricating properties of IL/(GO-MWCNT) solid–liquid lubricating coatings. The solid–liquid lubricating coatings consist of ionic liquids (IL), graphene oxide (GO), and multi-walled carbon nanotubes (MWCNT). Irradiation experiments were carried out using ground simulation equipment. Atomic oxygen (AO), ultraviolet (UV), proton (Pr), and electron (El) irradiation alter the composition, structure, morphology, and tribological properties of solid–liquid lubricating coatings. The experimental results show the composition changes induced by irradiation, including the decomposition of ILs lubricants. The damage to the lubricating material was the most serious by Pr irradiation and the least by UV irradiation.
... The energy with which the atoms of the oxygen impinge on the spacecraft surface, moving with a high velocity, becomes around 5 eV. In this LEO region, the flux of the atomic oxygen varies from $10 12 to 10 15 atoms cm À2 s À1 [36]. The surface region of the polymer which is used as a shielding material over the spacecraft, therefore, receives fluences of $10 19 -10 22 ions cm À2 in a period of about 1 year. ...
Polyimide (PI, PMDA-ODA, C22H11N2O5, Kapton-H), is a class of polymer, extensively used in microelectronics and space technology, due to its exceptional mechanical, dielectric, and chemical properties. In space, PI heat shield experiences a harsh environment of energetic electrons, ultra-violet radiation, and atomic oxygen, causing degradation and erosion. Radiation-assisted physicochemical surface modulations in PI, in view of understanding and reducing the degradation in laboratory-based systems, are discussed in the chapter. Strategies for the design and development of 2D, flat, and flexible electromechanical devices by swift heavy ion induced bulk modifications in PI are also described. Fabrication of a couple of such devices, including their performance analysis, is presented.
... Various kinds of coatings have been developed [8][9][10]. For example, ceramic coatings, such as Al 2 O 3 [11] and SiO 2 , have very low AO erosion-corrosion yield, being only 0.1-0.2% of that of Kapton (the registered trademark of a polyimide produced by DuPont) [12]. Meanwhile, the ceramic coatings also show excellent resistance to VUV irradiation in long-term exposure. ...
A continuous and uniform AZ31 magnesium alloy coating was deposited by magnetron sputtering to protect flexible polyimide substrate (Kapton HN) from atomic oxygen (AO) erosion-corrosion in low earth orbit. The AO erosion yield of the coated Kapton was determined to be 8.87 × 10⁻²⁶ cm³ atom⁻¹ after exposure to AO fluence of 1.47 × 10²¹ atoms cm⁻², about 34 times lower than that of blank Kapton. XPS analysis results showed that an oxide layer of MgO formed on the surface of the coating after AO exposure, which is the main reason for the enhanced AO erosion-corrosion resistance of the AZ31 Mg-alloy coating.
... AO exposure tests were conducted on a ground-based AO effect simulation facility designed by Beijing university of aeronautics and astronautics [31]. The AO flux was calculated to be 2.1 Â 10 15 atoms/ cm 2 $s from mass loss of Kapton ® H. ...
... When the pressure of the facility chamber was reduced to 4.0 × 10 −3 Pa by means of a vacuum system, the oxygen stream was introduced into the chamber through a flow controller. Simultaneously, some electrons were discharged by a heated cathode filament and were accelerated by using a directed magnetic field to strike and debone O−O for producing the desired AO particles [12]. ...
Atomic oxygen (AO) is considered the most erosive particle to spacecraft materials in low earth orbit (LEO). Carbon fiber, carbon/carbon (C/C), and some modified C/C composites were exposed to a simulated AO environment to investigate their behaviors in LEO. Scanning electron microscopy (SEM), AO erosion rate calculation, and mechanical property testing were used to characterize the material properties. Results show that the carbon fiber and C/C specimens undergo significant degradation under the AO bombing. According to the effects of AO on C/C-SiC and CVD-SiC-coated C/C, a condensed CVD-SiC coat is a feasible approach to protect C/C composites from AO degradation.
Flexibility and lightweight are promising research topics for space science and technology, which benefit to reduce load, reduce volume, and integrate device. However, most photoelectronic devices on spacecraft are rigid devices now, because the space environment consists of irradiations and thermal cycling, with higher requirements for flexible photoelectronic materials and devices. The main bottlenecks include: the synthesis of space-durable packaging materials, the fabrication and packaging of flexible photoelectronic devices, and the effective investigation method for irradiation mechanism analysis. In view of these problems, this review presents the synthesis of bulk-phase silicon-reinforced yellow and transparent polyimides with space durability, the optical modulation of bulk-phase silicon-reinforced polyimide to ultra-black film and flexible color filters, the electrical modulation of bulk-phase silicon-reinforced polyimide into flexible transparent electrode, the integration of the bulk-phase silicon-reinforced transparent polyimide and flexible triple-junction GaAs thin-film solar cell, and the exploration of general investigation methods for irradiation mechanism based on the penetration depth and damage modes including atomic oxygen, ultraviolet, electron, proton, and thermal cycling. The material synthesis, device fabrication, and mechanism analysis method focus on the core scientific problems of space-durable flexible lightweight photoelectronic materials and devices, leading the development direction of flexible and lightweight space science and technology.
Graphene and graphene/nanoparticles were explored to enhance the atomic oxygen (AO) corrosion resistance of polyimide (PI) composites. Graphene flakes (EGs) were produced by electrochemical method using alternating current (AC). A series of EGs/PI composite films were prepared by in-situ polymerization. After exposure to AO, although all EGs/PI composite films were resistant to AO, we found a much greater enhancement, i.e. adding 1.5 wt% EGs can reduce the mass loss of the composite by 42%. On this basis, EGs/SiO2 and EGs/Al2O3 co-doping fillers were firstly used to further enhance the AO corrosion resistance of PI. The sample co-doped 1.5 wt% EGs with 3 wt% SiO2 could achieve a 71% decrease in the composite’ mass loss. Bonding effect and barrier effect of graphene fillers are responsible for the enhanced protective performance. At the same time, the “synergistic effect” between EGs and nanoparticles also plays a role in the enhancement. These preliminary but interesting results pave a novel way for the study of AO corrosion resistance.
Searching for a method for simple and low-cost preparation of polyimide (PI) composite film and exploring their atomic oxygen (AO) erosion resistance properties are highly important. For the first time we studied the AO erosion resistance of SiO2-Al2O3 doped composite PI film, and the associated sol-gel method and physical blending method were compared. After exposure to AO, all the nanocomposite film shows enhanced AO erosion resistance. Especially, a loading of 7.5 wt% SiO2-2.5 wt% Al2O3 can decrease the AO induced mass loss by 81% when compared to the pure PI, i.e. the AO resistance was increased by 4-5 times. It is found that with the same doping content, the AO resistance of the two-component (SiO2-Al2O3) hybrid PI film is notably higher than that of the single component one. The mechanism could be attributed to the SiO2-Al2O3 synergistic effect which induces a more stable protective layer on the material surface. The two-component PI composite film with enhanced AO resistance shows promise in the space applications where AO erosion has to be avoided.
Erosion studies of polyimide, exposed to high energy electrons and atomic oxygen, is necessary in view of its application in space vehicles. Here we present the erosion studies and degradation characteristics of polyimide after its sequential exposure to 1 MeV pulsed electron beam from Microtron accelerator and ~12 eV oxygen ions from a plasma reactor in the laboratory. The fluence of electrons was varied from 5 × 10¹⁴ to 2.0 × 10¹⁵ electrons/cm² and that of oxygen ions from ~5 × 10¹⁶ to 2 × 10¹⁷ ions cm⁻². The post irradiated and virgin polyimide samples were characterized by gravimetric analysis and contact-angle measurements. The morphological and spectroscopic information were obtained with Scanning Electron Microscopy, Fourier Transform Infra-Red spectroscopy, and photo-absorption spectroscopy. The erosion yield, surface wettability and the surface roughness were seen to be much higher when exposed to both the radiations as compared to either of them, reflecting the synergetic effects.
Polyhedral oligomeric silsesquioxane (POSS) was grafted onto the surface of carbon fibres (CFs) to fabricate carbon fibre/epoxy (CF/EP) composites with improved interlaminar shear strength (ILSS) and atomic oxygen (AO) erosion resistance. POSS-CF was prepared by reacting amine groups on the pretreated CF surface with the POSS to form a continuous uniform layer of siloxane oligomers. X-Ray photoelectron spectroscopy, scanning electron microscopy and Fourier transform infrared spectroscopy demonstrated that POSS was successfully grafted onto the CF surface. The ILSS and AO erosion resistance of the POSS-treated CFs and CF-EP interface were improved because a SiO 2 passivation layer formed with AO exposure, especially with POSS-EP0409. This is an effective solution for enhancing the interfacial bonding force and interfacial AO erosion resistance for the low-Earth orbit environment.
We have studied the thermal stability of RuO2/polyimide (Kapton) interface using experimental and theoretical methods. Based on calorimetric and spectroscopic analyses, this inorganic-organic system does not exhibit any enthalpic peaks as well as all bonds in RuO2 and Kapton are preserved up to 500 °C. In addition, large-scale density functional theory based molecular dynamics, carried out in the same temperature range, validates the electronic structure and points out that numerous Ru-C and a few Ru-O covalent/ionic bonds form across the RuO2/Kapton interface. This indicates strong adhesion, but there is no evidence of Kapton degradation upon thermal excitation. Furthermore, RuO2 does not exhibit any interfacial bonds with N and H in Kapton, providing additional evidence for the thermal stability notion. It is suggested that the RuO2/Kapton interface is stable due to aromatic architecture of Kapton. This enhanced thermal stability renders Kapton an appropriate polymeric substrate for RuO2 containing systems in various applications, especially for flexible microelectronic and energy devices.
Copolymers of polyhedral oligomeric silsesquioxane (POSS) and polyimide (PI) have shown remarkable resistance to atomic oxygen (AO) attack and have been proposed as a replacement for Kapton on the external surfaces of spacecraft in the harsh oxidizing environment of low Earth orbit (LEO). POSS PI blends would be an economical alternative to the copolymers if they also resisted AO attack. Thus, blends of trisilanolphenyl POSS and PI with different weight percentages of the Si7O9 POSS cage were cast into films and exposed to a hyperthermal AO beam, and they were characterized in terms of their recession, mass loss, surface morphology, and surface chemistry. In order to compare the AO resistance of the blends with POSS PI copolymers, samples of previously studied copolymers were also investigated in parallel with the blends. For all POSS PI materials, the AO resistance increased with increasing AO fluence and with increasing POSS cage loading. At similar POSS cage loadings and exposure conditions, the TSP POSS PI blends showed comparable erosion yields to the POSS PI copolymers, with specific samples of blends and copolymers achieving erosion yields as low as 0.066 × 10-24 cm³ atom⁻¹ with an AO fluence of 5.93 × 10²⁰ O atoms cm⁻². SEM and XPS analyses indicated that passivating SiOx layers were formed on the surfaces of all POSS-containing polymers during AO exposure. Thus, a TSP POSS PI blend is proposed as a low-cost variant of a POSS polyimide for use in extreme oxidizing environments, such as LEO.
Polyimide (PI) films, used as thermal blankets for satellites, are exposed to AO irradiation and subjected to hypervelocity debris impacts. Ground based experiments showed that due to these impacts, residual tensile stresses are formed in the PI causing accelerated erosion in an AO environment. However, fundamental research in regard to stress related AO erosion effect is missing.
The objective of this work is to study the erosion mechanism of Kapton (commercial PI) films which are subjected to tensile stresses in an environment simulating AO exposure. The combined effect of the tensile stresses’ magnitude and direction on Kapton films erosion while exposed to AO environment are studied in terms of changes in surface morphology.
The results reveal that the Kapton’s surface morphology is affected by the stress intensity and by its applied direction relative to the polymer chains direction. At low AO fluencies, without applied stress, a classical carpet-like morphology was attained. Under combined effect of stress and AO irradiation, an ordered surface was formed almost orthogonal to the direction of the applied stress.
It is critical for carbon fiber/epoxy (CF/EP) composites to have a high resistance to atomic oxygen (AO) erosion when they are utilized in a low earth orbit (LEO) environment. Herein, we proposed a simple method whereby a silane coupling agent (SCA) was applied onto the carbon fiber surface to fabricate CF/EP composites with both improved interfacial shear strength (IFSS) and AO erosion resistance. The SCA was first hydrolyzed, then reacted with the hydroxyl groups on the pretreated CF surface, and finally formed a continuous uniform layer of siloxane oligomers. Atomic force microscopy images exhibited relatively smooth surfaces for SCA-treated CFs after AO erosion, when compared to the rough surface for bare CFs. It was found that the IFSS and AO erosion resistance were improved for SCA-coated CFs and CF/EP composite interface since a silica (SiO2) layer was formed upon exposure to AO as confirmed by XPS results.
Based on the ground-based simulation facility, the effects of atomic oxygen (AO) irradiation on the structural and tribological properties of pure polytetrafluoroethylene (PTFE) and carbon fiber and MoS2-filled PTFE composites were studied by scanning electron microscopy, X-ray photoelectron spectroscopy, and a ball-on-disc tribometer. The results shown that AO irradiation had significant effects on the structural and tribological properties of pure PTFE, in which the surface morphologies, mass loss, friction coefficient, and wear rate had been changed greatly after AO irradiation. However, it was noticeable that the addition of carbon fiber and MoS2 filler to PTFE could improve the AO resist capacity and tribological properties of PTFE composites significantly.
In order to investigate the effect of space environmental factors on spacecraft materials, a ground-based simulation facility for space atomic oxygen (AO) irradiation was developed in our laboratory. Some Kapton film samples were subjected to AO beam generated by this facility. The Kapton films before and after AO exposure were analyzed comparatively using optical microscopy, scanning electronic microscopy, atomic force microscopy, high-precision microbalance, and X-ray photoelectron spectroscopy. The experimental results indicate that the transmittance of Kapton film will be reduced by AO irradiation notably, and its color deepens from pale yellow to brown. Surface roughness of the AO-treated sample is already increased obviously after AO irradiation for 5 hours, and exhibits a flannel-like appearance after 15 hours’ exposure in AO beam. The imide rings and benzene rings in kapton molecule are partially decomposed, and some new bonds form during AO irradiation. The mass loss of kapton film increases linearly with the increase of AO fluence, which is resulted from the formation of volatile products, such as CO, CO2and NOx. The breakage in structure and degradation in properties of AO-treated Kapton film can be attributed to the integrated effect of impaction and oxidization of AO beam. The test results agree well with the space flight experimental data. © 2014, Wuhan University of Technology and Springer-Verlag Berlin Heidelberg.
The changes in the surface structure and the tribological performance of polyetheretherketone (PEEK) induced by individual and sequential irradiations with atomic oxygen (AO) and protons (Prs) were investigated in a space environment simulation facility. The experimental results showed that Pr irradiation induced the surface carbonization of PEEK which induced the greatest degree of decrease in the surface roughness from 29.61 nm to 16.15 nm, surface energy from 49.16 mJ m-2 to 46.96 mJ m-2, friction coefficient from 0.28 to 0.08 and wear rate from 10.28 × 10-5 mm3 N-1 m-1 to 5.45 × 10-5 mm3 N-1 m-1. The AO irradiation induced the surface oxidation of PEEK, and then increased the surface roughness from 29.61 nm to 58.77 nm, surface energy from 49.16 mJ m-2 to 73.75 mJ m-2, friction coefficient from 0.28 to 0.35 and wear rate from 10.28 × 10-5 mm3 N-1 m-1 to 18.22 × 10-5 mm3 N-1 m-1. The surface structural variations and tribological performance of PEEK induced by the sequential Pr-AO and AO-Pr irradiations were respectively similar to the results of the individual AO and Pr irradiations, and the final form of irradiation has a bigger effect on the changes in the surface structure and tribological performance during the sequential irradiation tests. The erosion stacking effect of the sequential irradiations was observed, and the AO-Pr irradiations caused the biggest changes in infrared spectra and the surface composition of C and O elements in X-ray photoelectron spectroscopy. The Pr-AO irradiations gave the biggest increment in the surface energy from 49.16 mJ m-2 to 74.03 mJ m-2 and wear rate from 10.28 × 10-5 mm3 N-1 m-1 to 24.07 × 10-5 mm3 N-1 m-1. This journal is
Hyperbranched polysiloxane (HBPSi) polyimide membranes were fabricated by copolymerizing amine–functionalized HBPSi and imide monomers. The atomic oxygen (AO) resistance of the resulting polyimides were investigated in simulated AO environment, based on their evolution of surface chemistry and morphology. Results indicated that a silica passivating layer finally formed on the membrane surfaces and, there was a percolation threshold of HBPSi addition to achieve the most desirable AO resistance. This is explained by the formation of a much denser and more connected silica passivating layer in shorter time on the membrane surface at high HBPSi loading upon AO exposure.
A new model was developed for the simulation of the friction coefficient in lubricated sliding line contacts. A half-space-based contact algorithm was linked with a numerical elasto-hydrodynamic lubrication solver using the load-sharing concept. The model was compared with an existing asperity-based friction model for a set of theoretical simulations. Depending on the load and surface roughness, the difference in friction varied up to 32 %. The numerical lubrication model makes it possible to also calculate lightly loaded contacts and can easily be extended to solve transient problems. Experimental validation was performed by measuring the friction coefficient as a function of sliding velocity for the stationary case.
The effects of atomic oxygen exposure on pure polyimide and nano-ZrO2 reinforced polyimide composites were investigated in a ground-based simulation facility. The experimental results indicated that the surface structure of both pure polyimide and ZrO2/polyimide composites were destroyed by atomic oxygen attack, but the addition of nano-ZrO2 particles in polyimide could obviously decrease the mass loss, which showed that ZrO2 could enhance the atomic oxygen resistance. The results of ZrO2/polyimide composites before and after atomic oxygen exposure showed that atomic oxygen irradiation aggravated the friction and wear of the ZrO2/polyimide composites. The wear mechanism was mainly abrasive particles wear arising from the ZrO2-rich layer on the surface of composites. The ZrO2/polyimide composites with 1 wt% nano-ZrO2 owns the lowest varying rate of the friction coefficient and wear rate before and after atomic oxygen exposure, which showed stable friction and wear properties and was expected to become a kind of potential tribological materials for practical spacecraft designation.
Highly uniform and defect-free multilayer coatings of montmorillonite (MMT) and poly (p-aminostyrene) (PPAS) on Kevlar fibers were generated to provide protection from atomic oxygen (AO) erosion, one of the greatest causes of degradation of polymeric materials used in the low earth orbit. The quantified protective MMT/PPAS layer was successfully deposited through a layer-by-layer assembly technique, as confirmed by Fourier-transform infrared spectroscopy and scanning electron microscopy. The accelerated AO durability was tested in a ground-based AO-effects simulation facility. The results show that the multilayers provide the Kevlar fibers an excellent protection from AO erosion.
The carbon fiber/phenolic resin composites were prepared and the atomic oxygen exposure test was conducted in a ground-based AO effects simulation facility. The effect of atomic oxygen on the composites was studied by scanning electron microscopy (SEM), attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR) and the X-ray photoelectron spectroscopy (XPS). The results show that the atomic oxygen environment, the mass loss are happened in the phenolic resin and carbon fiber and carbon/phenolic composite, and the mass loss of carbon/phenolic composite mass loss rate is greater than the total mass loss of phenolic resin and carbon fiber. Its mechanism shows the interaction of atomic oxygen with phenolic resin and carbon fiber agree with Undercutting Model. For phenolic resin, the methylene bridges and ether bond both can be oxidized after AO exposure, which result in void distributed on the surface of phenolic resin. For carbon fiber, the sizing agent is etched first and then the fiber is oxidized into -O-C=O and -C=O after AO exposure with the result that the size of carbon fiber diminishes and the cylindrical carbon fiber is out of shape with shallow and broad groove distributed on the surface.
Few-layer graphene (FLG) and graphene oxide (GO) were explored to enhance the oxygen-atom corrosion resistance of composites. FLG flakes of two different average lateral sizes (large: ∼1.3 μm(2) and small: ∼0.23 μm(2)) were prepared by a centrifugation-based size selection route. After exposure to oxygen atoms, although all fillers could enhance the oxygen-atom corrosion resistance of the composites, we found a much greater enhancement using large FLG, i.e. adding 1 wt% large FLG can achieve a 42% decrease in the composites' mass loss. Bonding and barrier effects of the flaked fillers are responsible for the enhanced resistance. These preliminary yet intriguing results pave a novel way for resisting oxygen-atom corrosion.
The effect of atomic oxygen (AO) on the surface oxidation of several typical Cu-based bulk metallic glasses (BMGs) was studied in the present work. The AO source using in this study is generated by discharge plasma type ground simulation equipment. The AO erosion/oxidation resistances of the amorphous alloy samples were assessed based on the analysis of mass loss, surface color and microstructure. It is found that these Cu-based BMGs possess good AO erosion/oxidation resistance and their resistance to AO erosion/oxidation strongly depends on the chemical composition. For the samples containing more Ag and/or Cu, the AO erosion/oxidation resistance is weaker. The present result is important for designing new metallic glasses using as space materials.
Inspired by the birch bark, which has multilayered structures, we fabricated layer-by-layer (LbL) assembled montmorillonite (MMT) and poly(p-aminostyrene) (PPAS) nanocomposites on cotton fiber curved surfaces to provide protection from atomic oxygen (AO) erosion. The multilayer coated fibers had high flexibility, uniformity, defect free, ease of preparation and low cost. The AO erosion durability has been dramatically enhanced which was evidenced by testing in the ground-based AO effects simulation facility. And the dimension and surface morphologies of the fibers observed by SEM had few changes, indicating excellent AO erosion resistant ability of the coatings. These results provide us a new method to design fibrous materials exposed directly in low earth orbit environment.
In order to expand the application field of MoS2 lubricant coatings (films) and to improve their adaptability in harsh environments, a Ni/MoS2–C composite coating composed of Ni metallic matrix and two lubricating components was prepared on AISI 52100 steel substrates with a nano electro-brush plating process. The relationship between microstructure and properties of the coating was analyzed via microstructure characterization. The tribological properties of the as-received coating samples and the samples treated in humid air (HA), high vacuum (HV), atomic oxygen (AO) erosion and ultraviolet (UV) irradiation exposure were investigated comparatively. The results show that the surface of the obtained Ni/MoS2–C coating is smooth and clean. The micro and nano MoS2–C grains are dispersed in the Ni matrix homogeneously. The MoS2 and C particles also showed good synergistic effects. The added nano graphite particles not only increased the moisture resistance of the composite coating, but also reduced the residual stress and enhanced the mechanical properties of the coating. The composite coating still showed good lubricating properties after long-duration treatments in HA, HV, AO and UV environments, and the friction coefficients during the stable running periods remained at about 0.1. The influence of vacuum outgassing on the properties of the lubricants is not obvious. The coatings were oxidized slightly by AO, and thus their initial friction coefficients in AO conditions also increased, but the coating still showed good friction reduction properties after a short running-in period. The changes in microstructure and properties of the coating after UV irradiation were also inconspicuous. All test results indicate that the Ni/MoS2–C composite coating has excellent space tribological properties and good adaptability in harsh environments. So it is promising to use Ni/MoS2–C composite coating in a space solid lubrication area.
Searching for a method for low-cost, easily manageable, and scalable production of boron nitride nanosheets (BNNSs) and exploring their novel applications are highly important. For the first time we demonstrate that a novel and effective hydrodynamics method, which involves multiple exfoliation mechanisms and thus leads to much higher yield and efficiency, can realize large-scale production of BNNSs. The exfoliation mechanisms that multiple fluid dynamics events contribute towards normal and lateral exfoliation processes could be applied to other layered materials. Up to ∼95% of the prepared BNNSs are less than 3.5 nm thick with a monolayer fraction of ∼37%. Compared to the conventional sonication and ball milling-based methods, the hydrodynamics method has the advantages of possessing multiple efficient ways for exfoliating BN, being low-cost and environmentally-friendly, producing high quality BNNSs in high yield and efficiency, and achieving concentrated BNNSs dispersions even in mediocre solvents. It is also shown for the first time that BNNSs can be utilized as fillers to improve the oxygen-atom erosion resistance of epoxy composites which are widely used for spacecraft in low earth orbit (LEO) where atom oxygen abounds. An addition of only 0.5 wt% BNNSs can result in a 70% decrease in the mass loss of epoxy composites after atom oxygen exposure equivalent to 160 days in an orbit of ∼300 km. Overall, the demonstrated hydrodynamics method shows great potential in large-scale production of BNNSs in industry in terms of yield, efficiency, and environmental friendliness; and the innovative application of BNNSs to enhancing oxygen-atom erosion resistance of polymeric composites in space may provide a novel route for designing light spacecraft in LEO.
A novel space survivable polyimide with a variety of desirable properties such as excellent thermal stability, high optical transparency, good mechanical strength, satisfactory break elongation and outstanding atomic oxygen (AO) erosion resistance has been prepared by first synthesizing hyperbranched polysiloxane (HBPSi) and second incorporating HBPSi into polyimide (PI) chains via copolycondensation reactions. 29Si nuclear magnetic resonance (29Si-NMR) spectrum of HBPSi indicated HBPSi possessed hyperbranched topology. The ground-based simulated AO exposure experiments demonstrated the mass loss of HBPSi polyimides decreased with increasing HBPSi addition and AO fluence and it reached as low as 7.7% that of pristine polyimide when HBPSi addition was 29.7 wt. % after 22 h's AO exposure. Surface morphologies confirmed pristine polyimide was significantly roughened after AO exposure while HBPSi polyimide appeared even less rough surface topography. During exposure of HBPSi polyimide to AO, the organic polyimide of the surface was first degraded and a silica protective layer eventually formed, which enabled the surface to be "self-healing". It is this passivation layer that prevents the underlying polymer from additional erosion. The whole preparation process of HBPSi polyimide is moderate, low-cost, environmentally friendly and suitable for industrialized mass production, which contributes this novel material to a "drop-in" replacement for the widely used Kapton on spacecrafts functioning in space environment.
Polyimide (PI) and fluorinated ethylene propylene (FEP) samples were exposed to atomic oxygen ions of average energy ∼12 eV and flux ∼5 × 1013 ions cm−2 s−1, produced in an ECR plasma. The fluence of the oxygen ions was varied from sample to sample over a range from ∼5 × 1016 to 2 × 1017 ions cm−2. The pre- and the post-irradiated samples were characterized by the contact angle, AFM and XPS techniques. The results indicate that the surface roughness of the polyimide increased from ∼7 to ∼65 nm, that of the FEP from ∼5 to ∼28 nm and the surface regions of both polyimide and FEP changed from hydrophobic to hydrophilic after exposure to atomic oxygen ions. The XPS results reveal that the concentrations of carbon, fluorine and oxygen changed even at a fluence of ∼1017 ions cm−2 of the atomic oxygen ions. The results of the present study reveal that significant changes have been induced in the surface morphology and adhesion properties of polyimide and FEP after exposure to atomic oxygen ions.
Polytetrafluoroethylene (Teflon), a widely used spacecraft material, is studied to investigate the vacuum ultraviolet (VUV) effects and its synergistic effects with atomic oxygen (AO) in a ground based simulation facility. The samples before and after the experiments are compared in appearance, mass, optical properties and surface composition. The reaction characteristics of Teflon are summarized and the reaction mechanisms are analyzed. The following conclusion can be drawn: at the action of VUV the Teflon sample surface is darkened for the accumulation of carbon; and when the sample is exposed to AO, the carbon is oxidized and the darkening surface is bleached; the synergistic effects of VUV and AO may cause the erosion of Teflon more severe.
A new technology is adopted to improve atomic oxygen resistance characteristics of spacecraft resin matrix composites, which is to fill superfine particles into the resin matrix. The superfine plerospheres, which are non-reactive with atomic oxygen, are filled into the phenolic matrix in order to produce the AO-resistant fibre/phenolic resin composite in the paper. Plerospheres/fiber/phenolic resin composites were prepared and the AO exposure test was conducted in a ground-based AO effects simulation facility. It was found that the filling of plerospheres effectively protected the fibre/phenolic resin against AO erosion. After the AO exposure test of 50–60h, the erosion yield of the glass fibre/phenolic resin and the carbon fibre/phenolic resin with plerosphere fillers could decrease to 9% and 13% of the composite without fillers, respectively. Furthermore, the erosion yield of all the composites decreased with the increase of the filler amount.
In the present work, an interaction potential between an incident reactive particle and a. material surface is constructed. The potential is formulated based on the unit bond index-quadratic exponential potential model and two adjustable factors characterizing the correlations of equilibrium-length scales and of attractive potential. In addition, the effective potential between monomers is obtained by Lifshitz's theory. The interaction of atomic oxygen with Kapton(R) is computed as a test case using the potential functions developed in the present paper in conjunction with the molecular dynamic model constructed by Lee and Chen (Lee, C.-H., and Chen, L. W., "Reactive Probability of Atomic Oxygen with Material Surfaces in Low Earth Orbit," Journal of Spacecraft and Rockets, Vol. 37, No. 2, 2000, pp. 252-256). The reactive probability computed by the present model is found to be 16.8% lower than for the STS-46 flight data, and the law of the incident angle-dependency deduced from the flight data is also confirmed by the numerical simulation. The numerical value of the accommodation factor computed in this task is 0.1368, which lies between the values of 0.1165, computed via the hard-sphere model, and 0.68, obtained from the ground test for atomic oxygen interacting with Kapton at an impingement angle of 45 deg and energy of 1.5 eV. The effects of the two adjustable factors given in. the potential model are also briefly discussed.
Polyimides (PIs), used in satellites, are exposed to atomic oxygen (AO) irradiation and subjected to hypervelocity debris impacts which form residual tensile stresses and accelerated erosion.
The objectives of this work are to study the PI's macromolecular structure and its deformation and erosion mechanisms when subjected to tensile stresses in an AO environment.
The study shows that commercial PI is anisotropic, characterized by two main axis which are related to its semicrystalline structure. Under combined effects of stress and AO irradiation the PI's morphology was dependent on the direction of the applied stress and its magnitude. When the stress was applied parallel to the first main axis a carpet-like texture was formed. When the stress was however applied parallel to the second main axis an ordered surface was formed orthogonal to the direction of the applied stress.
A mechanism which relates these findings to the PI macromolecular orientation is suggested.
To improve the atomic oxygen (AO) resistance of the spacecraft resin matrix material, inorganic silica nanoparticles were filled into the epoxy resin. Samples of the epoxy/silica nanocomposites were prepared and AO exposure experiments were conducted in a ground-based AO effects simulation facility. The samples exhibited significantly less mass loss and erosion yield than the corresponding pristine epoxy resin. Analysis of the surface morphology, composition and chemical structures showed that some organic structures still resides on the nanocomposites surface after the AO exposure experiment. The silica nanoparticles and the organic structures could serve as a barrier to resist further erosion. POLYM. ENG. SCI., 47:1156–1162, 2007. © 2007 Society of Plastics Engineers
Polyimide (Kapton-H), was subjected to atomic oxygen from an electron cyclotron resonance plasma. An optical emission spectrometer was used to characterize the atomic oxygen produced in the reactor chamber. The energy of the ions was measured using a retarding field analyzer, placed near the substrate. The density of atomic oxygen in the plasma was estimated using a nickel catalytic probe. The surface wettability of the polyimide samples monitored by contact angle measurements showed considerable improvement when treated with plasma. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopic studies showed that the atomic oxygen in the plasma is the main specie affecting the surface chemistry and adhesion properties of polyimide. The improvement in the surface wettability is attributed to the high degree of cross-linking and large concentration of polar groups generated in the surface region of polyimide, after plasma treatment. The changes in the surface region of polyimide were observed by atomic force microscopic analysis.
The presence of several atomic species in the LEO (Low Earth Orbits) could be considered one of the reasons for the degradation of the surfaces exposed to the Space Environment.At an average height of 400 Km (the altitude of International Space Station), the concentration of the main atomic species during the high sun activity are: for atomic oxygen (AO), for molecular nitrogen (N2) and for atomic nitrogen (N). The energy with which the atoms collide with the surface of orbiting vehicle depends on the relative speed of the vehicle itself. For instance, the atoms colliding the International Space Station (ISS) (orbit average height: 400 Km; relative speed: 7.5 Km/s) have an energy of 8 eV for N2, 5 eV for OA and 4 eV for N.The atomic oxygen is the most abundant species presents in LEO and it is considered the main responsible of the thermal, optical and mechanical alteration of the surfaces exposed to the Space Environment.Different hypothesis are reported in literature in order to explain the physical/chemical mechanisms that govern the material degradation in the Space, but no conclusion has been reached.In the energy range of few of eV, the main mechanism with which colliding atoms transfer its energy to the atoms of the surface is by phonons. In this paper the effect of an oxygen ion beam produced in the space environment simulator on materials for Space applications is studied in the frame of the thermal spike theory. Comparison between the measured erosion and the calculated one will be reported. The erosion mechanism will be modelled in order to understand the main thermodynamic parameters that govern the interaction between the atomic oxygen and the surface of the tested materials.
To improve the atomic oxygen (AO) resistant characteristics of spacecraft resin matrix composite, nano-silicon dioxide particles were filled into glass fiber/polyimide composite and atomic oxygen exposure experiments were conducted in a ground-based AO effects simulation facility. After the exposure experiment, the surface morphology and surface compositions of the samples were analyzed with SEM and XPS, respectively. The experimental results showed that the AO resistant characteristics of this new composite were improved remarkably; the mass loss and erosion yield fell distinctly. It proves that filling these nano-particles is an effective method to improve the AO resistant characteristics of the composite. The erosion yield of glass fiber/15SiO2/polyimide decreased to 16.4% after a 40-h exposure experiment.
Polyimides are used as the outer layer of thermal control insulation blankets covering most of the external spacecraft surfaces that are exposed to space environment. The combined effect of ground simulated hypervelocity space debris impacts and atomic oxygen (AO) on the fracture of polyimide films was studied. A laser-driven flyer system was used to accelerate aluminum flyers to impact velocities of up to 3 km/s. The impacted films were exposed to an RF plasma source, which was used to simulate the effect of AO in the low Earth orbit. Scanning electron microscopy and atomic force microscopy were used to characterize the fracture and surface morphology. When exposed to oxygen RF plasma, the impacted polyimide film revealed a large increase in the erosion rate, the damage being characterized mainly by the formation of new holes. This effect is explained by the formation of residual stresses due to the impact and enhancement of oxygen diffusivity and accumulation. A complementary experiment, in which a stressed polyimide was exposed to RF plasma, supports this model. This study demonstrates a synergistic effect of the space environment components on polymers' degradation, which is essential for understanding the potential hazards of ultrahigh velocity impacts and AO erosion for completing a successful spacecraft mission.
Spacecraft traveling in low earth orbit (LEO) will react with environmental factors, such as atomic oxygen (AO), ultraviolet radiation (UV) and vacuum ultraviolet radiation (VUV), which may severely affect the lifetime of the spacecraft. Teflon, including PTFE (polytetrafluoroethylene) Teflon and FEP Teflon, is a commonly used spacecraft material. Existing studies showed that Teflon could be eroded by AO in LEO but with a lower erosion yield than most of other spacecraft materials. However, its erosion yield increases in long-term flight experiments, which might be caused by synergism of several environmental effects. In this work, experiments were conducted to investigate the erosion effects of atomic oxygen on PTFE Teflon in a ground-based simulation facility. The samples, before and after the experiments, were compared in appearance, mass, surface morphology, optical properties and surface composition. We also analysed the influence of temperature, ultraviolet radiation and vacuum ultraviolet radiation on the atomic oxygen effects. Four conclusions can be drawn: first, PTFE Teflon is eroded severely in the ground-based facility, where the erosion yield is higher than that in the flight experiments and identical to those from other ground-based facilities. Secondly, the erosion yield increases with the sample temperature. Thirdly, ultraviolet radiation has little effect on the mass loss and erosion yield of the Teflon sample in the AO experiment. Lastly, there may be some synergistic effects of atomic oxygen and vacuum ultraviolet radiation, which could be one of the main factors that cause the more severe erosion of Teflon.
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