V. N. Chernik

Mathematical and experimental simulation of impact of atomic oxygen of the Earth’s upper atmosphere on nanostructures and polymer composites

The article discusses the results of mathematical and experimental simulation of the impact of atomic oxygen of the Earth’s upper atmosphere on carbon and boron nitride nanotubes, graphene, hexagonal boron nitride sheets, and graphene nanoribbons, as well as composites based on polymer matrices with fillers in the form of nanosized particles of various types.

Degradation Testing of Spacecraft Materials for Long Flights in Low Earth Orbit

Results of simulation tests of the influence of the protective and functional coatings on the resistance of polymeric constructional spacecraft materials to the impact of atomic oxygen with fluences up to 3.5 × × 1022 cm−2 are presented. It was demonstrated that oxygen plasma beams can be used in accelerated tests of carbon-based and polymeric material structures (with the exception of filled and fluorinated hydrocarbons) to evaluate their resistance to the atomic oxygen impact in low Earth orbit. For unprotected materials, a sharp fall of mechanical properties and a deterioration of optical characteristics were observed. The application of protective coatings is shown to reduce this degradation.

Erosion of polyimide modified by amorphous silica sol in the stream of oxygen plasma

Polymeric coatings derived from Kapton H polyimide, thermoplastic polyimide (PI), and a composite with amorphous silica sol (PI-SS) were irradiated in a magnetoplasma dynamic accelerator of oxygen plasma simulating the action of atomic oxygen (AO). The volumetric erosion coefficients of polymers were calculated, and the comparative analysis of the stability of coatings was performed. The changes in morphology of polymer surfaces before and after irradiation were studied by means of scanning electron microscopy. It was shown that the PI-SS composite has increased resistance to atomic oxygen. The composition of the PI-SS composite was found at which the particles of silica sol are uniformly dispersed over the polymer volume that explains a better resistance of PI-SS polymeric-inorganic compositions to the action of atomic oxygen. The lowest stability was registered for the coating based on Kapton H polyimide. The surfaces of all coatings after irradiation were found to possess a carpetlike morphology. Each polymer featured a number of distinctive peculiarities of the surface structure caused by the differences in the chemical structure of the polymides under investigation.

RBS and XFA analysis of polyimide films from the mir space station

The elemental composition of polyimide film contamination was studied by the RBS and XFA methods. The films were exposed to the space environment aboard the Mir orbital space station during the KOMPLAST in-flight experiment. It was shown that the prevalent deposit element was silicon, which agrees with measurements performed on other spacecrafts.

Atomic Oxygen Influence on Polymer Nanocomposites with Different Fillers

This paper describes results of ground-based simulation of atomic oxygen influence on samples of polymer composites with different fillers. Polyimide and polyamide-imide were used as matrices, and polyorganosiloxanes, inorganic nanoparticles of Al2O3, TiO2, WC, multiwalled carbon nanotubes, and detonation nanodiamonds were used as fillers. Data on mass loss of composite samples due to atomic oxygen exposure and results of surface morphology analysis are given.

Critical Evaluation of Testing Results for Russian and Western Space Materials in Ground-Based Simulator Facilities and in Space Experiments

A critical evaluation of space flight experiments and ground-based testing results in LEO simulating facilities for Russian space materials and their functional US and European space materials counterparts, as well as predictive performance evaluation are presented and discussed. Results of long-term GEO imitating ground-based testing are presented also for selected advanced thermal control materials.

Experimental and physicomathematical simulation of the effect of an incident flow of atomic oxygen on highly filled polymer composites

The effect of the flow of atomic oxygen (AO) on highly filled composites of a high-impact polystyrene (HIPS) and a superfine silicon-organic filler is investigated. Erosion coefficients after the treatment with AO are calculated, and the postirradiation relief of the composites is studied by the method of scanning electron microscopy (SEM). A physicomathematical simulation of erosion processes is performed on the basis of the obtained data.

Use of hyperbranched polyethoxysiloxane to improve the resistance of thermoplastic polyimide coatings to atomic oxygen environment

Polyimide thin films both unmodified and modified with hyperbranched polyethoxysiloxane were treated with accelerated oxygen plasma flow to imitate a low Earth orbit environment. The resulting changes in the surface morphology were studied using scanning electron microscopy. The erosion yield values were calculated and the relative stability of the tested samples was established. It was shown that the polyimide-polyethoxysiloxane composites have higher atomic oxygen resistance owing to, presumably, the siloxane particles dispersed uniformly in the polyimide matrix. The study found that all plasma-treated samples exhibit the same fibrous, carpet-like surface morphology with some minor variations caused by differences in the chemical composition of polymers.

Investigation of the structure of a polyimide modified by hyperbranched polyorganosiloxanes

Polymer composites based on polyimide and hyperbranched polyorganosiloxanes have been irradiated by oxygen plasma imitating exposure to atomic oxygen in low near-earth orbits. It is demonstrated that the irradiation of composites gives rise to the generation of silicon dioxide particles distributed over the volume of the polymer matrix, promoting enhanced resistance of the materials to the action of atomic oxygen. The structures of the samples are investigated via dielectric and IR spectroscopies. It has been ascertained that introduced modifiers lead to the formation of regions with an increased ordering of polyimide chains around filler particles.

Surface structure changes in carbon-based materials and polymers under an oxygen-plasma beam

The surface topography of samples of graphite USB-15, pyrolytic carbon PGI, pyrolitic graphite UPV-1, and polyimide PM-1E exposed to accelerated oxygen-plasma beams has been studied by scanning electron microscopy. Surface etching by fast oxygen particles results in the formation of a system of cone/column-like protrusions. As the material mass loss increases, the protrusions increase in size, and the surface topography transforms. Etching of carbon-based materials leads to enrichment of the surface layer with carbon, which is most pronounced in the boron-doped graphite.