![SEM of a crack in the P4 coating (adapted from Kulig [20]),](https://www.researchgate.net/profile/Packirisamy-Shanmugam/publication/226701414/figure/fig1/AS:668916888133639@1536493622723/SEM-of-a-crack-in-the-P4-coating-adapted-from-Kulig-20_Q320.jpg)
![Mass loss of unprotected and DBP-1 protected Kapton 9 on exposure to atomic oxygen (adapted from Packirisamy et aL [50]).](https://www.researchgate.net/profile/Packirisamy-Shanmugam/publication/226701414/figure/fig4/AS:668916888129555@1536493622899/Mass-loss-of-unprotected-and-DBP-1-protected-Kapton-9-on-exposure-to-atomic-oxygen_Q320.jpg)
![SEM of broken glassy layer of DBP-1 coating ashed for 624 h (adapted from Packirisamy et aL [50]).](https://www.researchgate.net/profile/Packirisamy-Shanmugam/publication/226701414/figure/fig6/AS:668916888133644@1536493622996/SEM-of-broken-glassy-layer-of-DBP-1-coating-ashed-for-624-h-adapted-from-Packirisamy-et_Q320.jpg)
![Figure t2 SEM of a broken glassy layer in a severely bent area of the P2 coating (adapted from Schwam et aL [27]).](https://www.researchgate.net/profile/Packirisamy-Shanmugam/publication/226701414/figure/fig2/AS:668916888129551@1536493622777/Figure-t2-SEM-of-a-broken-glassy-layer-in-a-severely-bent-area-of-the-P2-coating-adapted_Q320.jpg)
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Atomic oxygen resistant coatings for low earth orbit space structures
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This review presents research in the area of polymeric coatings developed for protecting low earth orbit (LEO) space structures from atomic oxygen. Following a brief description of the LEO environment, ground-based simulation facilities for atomic oxygen and evaluation of protective coatings are discussed. Atomic oxygen resistant coatings based on different polymeric systems such as fluorinated polymers, silicones, poly (carborane-siloxane)s and decarborane-based polymers are presented. Finally, the performances of different coating systems are compared and the scope for further research to improve the performance of some of the coating systems is discussed.
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... Atomic oxygen is the main gas in the low Earth orbit space [167][168][169]. Many space and ground simulation results have proved that the high energy AO will destroy the carbon chain of the polymer, leading to being oxidized into CO, CO 2 , H 2 O, and other volatile gases, which become the primary damage to PI (Figure 18). ...
... Atomic oxygen is the main gas in the low Earth orbit space [167][168][169] and ground simulation results have proved that the high energy AO will d bon chain of the polymer, leading to being oxidized into CO, CO2, H2O, and gases, which become the primary damage to PI (Figure 18). One princip method is preparing oxide protective coating on a PI substrate to prevent s Lachance [170] and Russel [171] et al. prepared SiO2 and Al2O3 inorga ings on PI surfaces by chemical vapor precipitation, and multilayer film Al2O3/TiO2 and Al2O3/ZnO, prepared by atomic layer deposition (ALD) tively avoid AO erosion, while ALD owns the disadvantage of high vacu requirement. ...
Polyimide (PI) is one of the most dominant engineering plastics with excellent thermal, mechanical, chemical stability and dielectric performance. Further improving the versatility of PIs is of great significance, broadening their application prospects. Thus, integrating functional nanofillers can finely tune the individual characteristic to a certain extent as required by the function. Integrating the two complementary benefits, PI-based composites strongly expand applications, such as aerospace, microelectronic devices, separation membranes, catalysis, and sensors. Here, from the perspective of system science, the recent studies of PI-based composites for molecular design, manufacturing process, combination methods, and the relevant applications are reviewed, more relevantly on the mechanism underlying the phenomena. Additionally, a systematic summary of the current challenges and further directions for PI nanocomposites is presented. Hence, the review will pave the way for future studies.
High-performance polymer (HPP) blends have made it possible to reliably replace metallic components in certain tribological applications over a broad temperature range, even in the absence of liquid lubrication. The current study examines the tribological performance of an advanced HPP aromatic thermosetting copolyester (ATSP) with those of poly-hydroxybenzoic acid polymer or Ekonol® as additives for polytetrafluoroethylene (PTFE). The tribological performance of the HPP blends was evaluated using a pin-on-disk configuration under unlubricated conditions from room temperature up to 300 °C. Compared to PTFE-Ekonol composites, PTFE-ATSP blends not only showed almost 50% reduction in the wear rate at all tested temperatures, but higher wear resistance at different sliding speeds. Temperature plays a critical role in the deposition of transfer films from the blended composite to the 440C stainless steel (440C SS) disk, where it was observed a rich fluoride transfer film when tested against PTFE-ATSP. Better tribological performance of PTFE- ATSP, compared to PTFE-Ekonol is attributed to its viscoelastic stability or higher mechanical strength in the studied temperature range, which results in lower wear rates. Tribological results point out that PTFE-ATSP blends are an attractive solution for oil-less applications in the temperature range of 25-300oC.
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.
Colorless polyimides (CPIs) with excellent optical transparency and atomic oxygen (AO) erosion resistance have potential applications in optoelectronic devices in low earth orbit (LEO) such as flexible thin film solar cells. Herein, 2‐trifluoromethyl‐4,4′‐diaminodiphenyl ether (3F‐ODA) and amine‐terminated HBPSi were synthesized as amino monomers. After co‐polymerizing with 1,2,4,5‐cyclohexanetetracarboxylic dianhydride (CHDA) and 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) in a typical sequential reaction manner, a series of CPI films with various HBPSi contents were fabricated. The resulting CPIs show high optical transmittance (84.8%–86.8% at 400 nm), outstanding atomic oxygen (AO) erosion resistance (AO erosion rate 4% that of pure CPI), satisfactory mechanical properties (tensile strength ca. 80 MPa, tensile modulus ca. 2.8 GPa), good thermal stability (Td ≥ 467 °C, Tg ≥ 304 °C) and desirable solubility. More importantly, the resulting CPIs show increasing AO resistance with the increase of HBPSi amount, and a fairly high optical transmittance can still be retained after AO exposure, far better than that of pure CPI. These impressive performances enable HBPSi CPIs capable of being used as substrate for lightweight solar cell arrays onboard spacecraft in LEO environment.
Design of materials embodying the adhesive and cohesive nature of mussel byssal protein mimics have long served to inspire material developers in uncommon areas. Herein, a Catechol-Polydimethyl Siloxane Covalent Hybrid polymer (PGDX) derived from mussel chemistry is demonstrated as a highly effective atomic oxygen resistance (AOR) coating/adhesive, a yet unreported activity. The rational design of PGDX through a greener route is derived from poly dimethyl siloxane diglycidyl ether (PG) and dopamine (D). PGDX coating achieved excellent AOR on commonly used aluminised polyimide (AI-PI) and polyimide (PI) multilayer insulation materials for satellites as exposure to AO fluence of 2.5 × 10¹⁸ atom/cm² resulted in 47 % and 71 % reduction in mass-loss rate for AI-PI and PI respectively. The hybrid morphology of the polymer enabled its solubility in solvents having different polarities thus widening the scope of coating perspectives of dopamine. The coated substrates possessed lower surface energy (PI/Al-PI, 23.6/24.8 mN/m) than their uncoated counterparts (Al-PI/PI, 29.60/34.4 mN/m) and lower work of adhesion that denoted the hydrophobicity of the coating owing to the siloxane segment. The modified PDMS backbone with mussel chemistry show potential for application as a coating and adhesive for protecting delicate satellite components from the highly degrading AO rich Low Earth Orbit (LEO) environment.
During the last decade, silicon-containing polymers such as polysilanes and polycarbosilanes have attracted much attention because of their potential applications as ceramics precursors,1 binders for ceramics2 and for powder metallurgy,3 photoresistors4 and photoinitiators,5 and non-linear optical materials.6 The first practical use of a polysilane was in the production of β-silicon carbide by the Yajima process (Eq. 1).7
Polymers of type [-B10H12·diamine]-n have been prepared by reaction of decaborane(14) with various diamines, including H2NCH2CH2NH2, Me2NCH2CH2NMe2, HN(CH2CH2)2NH, and N(CH2CH2)3N in diethyl ether solution. The polymers, all white solids, were characterized by elemental, thermogravimetric, and thermomechanical analysis and molecular weight determinations. The synthesis and characterization of copolymers and end-capped oligomers are also described. Pyrolysis of such polymers in a stream of argon to 1000°C gave boron carbonitride in high yield. Pyrolysis in a stream of ammonia gave almost carbon-free boron nitride. Heating of these amorphous ceramics to 1500°C gave a crystalline material. The pyrolysis mechanism involves early conversion of the covalent polymer, by proton transfer from boron to nitrogen, to a nonvolatile diammonium salt of the [B10H10]2- anion. These polymers serve as low-loss binders for ceramic powders and as precursors for ceramic monoliths. Short (5 cm) fibers could be drawn from syrups of such polymers in DMF; subsequent pyrolysis gave ceramic fibers.
An optical microscope study of the stress relief forms of diamond-like carbon thin films is presented in this paper. The dimensions of the stress relief patterns are shown to be proportional to the film thickness. Three stress relief forms are distinguished. They are analysed in the framework of the linear theory of plate buckling. The forms of the stress relief correspond to two different solutions of the differential equations.
The mechanical properties of thin coatings are closely coupled with the preparation techniques used. In carbon layers deposited by electron beam and ion beam techniques high compressive stresses were measured and these stresses cause debonding of the layer. In some cases amazing structures and shapes of the debonded regions were observed: wavy wrinkles with well-defined widths and shapes. The nucleation and growth of these wrinkles is caused by a very well-defined combination of internal strain, Young's modulus, coating thickness and adhesion energy. This may be used to estimate the internal strain as well as the adhesion energy. For the i-C (where i signifies the use of an ion beam) layers 200 nm thick that were investigated internal stresses of 3–6 GPa and adhesion energies in the range of 4–7 N m−1 were estimated. These adhesion energies are more than an order of magnitude higher than those measured previously.
The mechanical properties of carbon films 500–3000 Å thick deposited onto glass substrates were investigated. The average internal stress measured by the cantilever method was 5 x 108N m−2 compression. This large stress often generates wrinkles in the films. Young's modulus of the film and the adhesion energy between the film and the substrate can be estimated from the shape and size of the wrinkles. As a method of estimation, the elastic energy of the wrinkled film is considered. The dependence of the size of the wrinkles on the film thickness is deduced and compared with experimental results.
Under basic conditions B10H12((C6H5) 2P·Cl)2 and B10H12((C6H5) 2P·OH)2 were found to enter into a condensation polymerization with elimination of hydrogen chloride to form a P-O-P linked polymer, (-OP(C6H5)2B10H12P(C 6H5)2-)x. A study of the pyrolysis of this polymer and monomeric compounds of the type B10H12((C6H5) 2P·R)2 was conducted. B10H12((C6H5) 2-N·N3)2 and diphosphines reacted in refluxing benzene with evolution of nitrogen to give P=N-P linked polymers of high thermal stability, e.g., (=P(C6H5)2-C6H4-P(C 6H5)2=N-P(C6H5) 2B10H12P(C6H5)2N=) x, dec. >340deg;.