Abstract The reaction mechanism of the N atom interaction with a single-layer MoS 2 , two-dimensional transition metal dichalcogenide, is considered in detail. These mechanisms were studied by DFT (density functional theory) modeling using both static and dynamic approaches. The most important processes for pristine and modified MoS 2 surfaces are revealed. For incident N atoms both the scattering and recombination with adsorbed atoms are prevailed. Various formation mechanisms for vacancies and other defects by thermal and hot N atoms are proposed and discussed. The results of dynamic DFT simulations are used to illustrate the reaction pathways.

This study investigates the properties of epoxy resin reinforced with carbon nanomaterials (graphene and multi-walled carbon nanotubes "Taunit M" and "Taunit MD"), focusing on their structural and optical characteristics, as well as the effects of atomic oxygen (AO) exposure, which is crucial for the application of such composites in low Earth orbit (LEO) conditions. Exposure to AO in LEO, with an average energy of similar to 5 eV, leads to the surface erosion of composites, resulting in significant mass loss. Experimental results indicate that the average erosion yield (Rm) is 1.07.10(-23) g/atom for the composite with "Taunit M" filler, 1.21.10(-23) g/atom for "Taunit MD", and 8.56.10(-24) g/atom for the graphene-filled composite. This effect occurs because carbon fillers undergo the oxidation and chemical sputtering under AO exposure, a typical behavior for materials used in space environments. After irradiation with an AO fluence of (1.7-30.0)10(20) atom/cm(2), a significant decrease in reflection coefficients (both specular and diffuse) is observed across a broad spectral range (0.2-25 mu m). Specular reflection decreased by 1.4 times for pure epoxy resin, and by 9.9, 15.8, and 13.6 times for samples filled with graphene, "Taunit M", and "Taunit MD", respectively. Diffuse reflection from the pure epoxy decreased by 1.2 times, while for graphene-, "Taunit M"-, and "Taunit MD"-filled samples, it decreased by 5.3, 16.7, and 9.0 times, respectively. These findings indicate that modifying epoxy resin with carbon nanomaterials followed by AO irradiation leads to the formation of a surface layer with high anti-reflective properties. Such materials, treated with low-energy oxygen plasma, are highly effective for use in optical and optoelectronic systems of spacecraft, as well as in terrestrial applications requiring materials with high absorption and low reflection.

The reaction mechanism of the N atom interaction with a single-layer MoS2, two-dimensional transition metal dichalcogenide, is considered in detail. These mechanisms were studied by DFT (density functional theory) modeling using both static and dynamic approaches. The most important processes for pristine and modified MoS2surfaces are revealed. For incident N atoms both the scattering and recombination with adsorbed atoms are prevailed. Various formation mechanisms for vacancies and other defects by thermal and hot N atoms are proposed and discussed. The results of dynamic DFT simulations are used to illustrate the reaction pathways.

A series of studies was conducted on the functional and structural characteristics of polymer composite materials (PCMs) based on silicone polymers modified with multi-walled carbon nanotubes (MWCNTs) and metallic particles (CuAl or Al). The influence of the structural parameters of carbon and metallic inclusions in the polymer matrix on the electrophysical and thermophysical properties of the composites was demonstrated. Various conduction mechanisms dominating in the inverse temperature ranges of 50 K–1–13 K–1, 13 K–1–6 K–1, and 6 K–1–2 K–1 were identified. The operational modes of the polymer composites as active materials for thermoregulating coatings were established. The highest temperature of 32.9 °C in operating mode and the shortest warm-up time of 180 s were observed in the composite modified with 4 wt.% CNTs and 10 wt.% bronze particles at a supply voltage of 10 V. The characteristics of the composites under atomic oxygen (AO) exposure with a fluence of 3 × 1021 atoms/cm2 was evaluated, confirming their functionality, particularly for potential space applications. The composites demonstrated nearly complete retention of their functional characteristics. The aim of this study was to develop electrically conductive functional composites based on silicone polymers containing MWCNTs and metallic particles inclusions for creating electric heating elements with tailored functional characteristics.

Описан программный комплекс Coulomb, предназначенный для моделирования электризации космических аппаратов (КА) в магнитосферной плазме на высоких и низких околоземных орбитах. Рассмотрены физические механизмы электризации КА и методы математического моделирования этого явления в разных областях космического пространства. Приведены примеры результатов расчета распределения электрического потенциала на поверхности и в окрестности КА для геостационарной орбиты и низких околоземных орбит.

•Metallosiloxane nanoparticles enhance the AO erosion resistance of copolyimides.•Siloxane-copolyimide is able to resist the AO attack on a par with nanoparticles.•The protection of metallosiloxane nanoparticles is not affected by the AO fluence.•The combined protection of the filled copolyimide is achieved at the high AO fluence.

The paper describes a magnetoplasmodynamic accelerator and the laboratory facility based on it that have been developed at the Skobeltsyn Institute of Nuclear Physics of Moscow State University to simulate the impact of atomic oxygen in the Earth’s upper atmosphere on materials of low-orbit satellites. The simulation methodology for accelerated ground-based testing of spacecraft materials is described in detail. Some results of laboratory research and numerical modelling of polymeric materials destruction by atomic oxygen are presented.

The Coulomb software complex for modeling of spacecraft charging in magnetosphere plasma in high and low Earth orbits is described. Physical mechanisms of spacecraft charging and methods of mathematical modeling of this phenomenon in various areas of space are considered. Examples of the calculation results of electrical potential distribution on the spacecraft surface and in the vicinity of the spacecraft in geosynchronous and the low Earth orbits are presented.

The paper deals with the experimental and theoretical study of the interaction of quasi-two-dimensional MoS2 films with nitrogen and oxygen plasmas in order to reveal the main mechanisms of their surface functionalization and to analyze its effects on the structure and properties of the films. Diagnostics of samples before and after treatment with radicals and ions was performed ex situ by Raman spectroscopy, spectroscopic ellipsometry, atomic force microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results of the experimental study showed that nitrogen and oxygen plasma treatment of ultrathin MoS2 films leads to the modification of the near-surface layers of the samples due to the removal of sulfur and the incorporation of incident atoms into forming vacancies. Nitrogen and oxygen ions with even low (less than 30 eV) energy causes partial removal of upper layers of the films leading to their partial destruction, while remote plasma (mainly by thermal radicals) guarantees more ‘soft’ treatment of films. The obtained spectroscopic data also indicated different effects of radicals (thermal O and N atoms) on the MoS2 surface. To analyze these effects, the computer modelling with density functional theory method was carried out. Its results enables to reveal the main mechanisms of the surface functionalization of MoS2 monolayers and to explain the experimental data.

The results of experimental studies of the processes occurring on the surface of protective glasses of solar batteries and elements of reflective coatings of high-orbit artificial Earth satellites (AES) under irradiation with electrons with an energy of 30 keV are presented. The studied samples were made on the basis of K-208 glass, while the samples of reflective coatings differed in the presence of silver and stainless steel layers on the reverse surface of the glass plates, deposited sequentially by the magnetron sputtering method. Electron irradiation of the samples was carried out in a vacuum of 10–4 Pa at a particle flux density (φ) from 1·109 to 8·1012 cm–2s–1; the surfaces of the samples before and after irradiation were examined by atomic force microscopy (AFM). On the irradiated surface of glass samples, electrostatic discharges (ESD) arose, the parameters of which were characterized by oscillograms of generated electromagnetic pulses; for elements of reflective coatings, leakage currents to the metal substrate were additionally measured. It was found that changes in the structure of the irradiated surface of the samples are due to the appearance of traces of ESD and the formation of gas-filled bubbles on it, and changes in the back surface of glass plates are caused, presumably, by shock waves formed when ESD occurs on the irradiated surface. The ESD frequency and leakage currents increase with increasing electron flux density in the specified range, but these dependences differ significantly. Measurements at a constant value of φ = 2.0·1010 cm–2s–1 showed that with an increase in the electron fluence from 1014 to 5·1016 cm–2, the ESR frequency increases, but the amplitude of electromagnetic pulses decreases.

Changes in the structure of the surface of K-208 glass irradiated in vacuum (10–4 Pa) by protons with energies of 30 keV have been studied. It has been established that the nature of the changes depends on the proton flux density (ϕр). At ϕр 3.0 × 1010 cm–2·s–1, the changes are mainly associated with the emergence of percolation channels on the irradiated surface. Percolation channels during proton irradiation of glass are formed as a result of migration of Na+ ions in the field of the charge injected into the glass. As ϕр increases, the formation of gas-filled bubbles begins to play a significant role. The appearance of bubbles is due to the fact that the field migration of Na+ ions is accompanied by the release of non-bridge oxygen atoms, which provided electrical neutrality in the vicinity of the localization of these ions. At values of ϕ 2 × 1011 cm–2·c–1, gas-filled bubbles and sodium microarrays form and grow in pairs. The authors believe that under these irradiation conditions, accelerated field migration of sodium ions through the percolation channel ensures intensive release of non-bridge oxygen atoms in its vicinity, followed by their migration and the formation of gas-filled bubbles.

Structural, optical and EMI shielding properties of epoxy resin reinforced with carbon nanotubes fillers “Taunit-M” and “Taunit-MD” have been studied. To estimate the resistance of nanocomposites operating in low-Earth orbits, the samples were exposed to atomic oxygen (AO) in the fluence range of (1.7–30) × 1020 cm−2. AO exposure results in mass loss of epoxy resin with carbon fillers: the erosion yields (Rm) are 1.07 × 10−23 g/atom and 1.21 × 10−23 g/atom for “Taunit-M″ and “Taunit-MD”, respectively. Diffuse and specular reflectance noticeably decreases after AO exposure which in their turn leads to increase of solar absorptance from 0.940 to 0.996 for “Taunit-M″ and from 0.944 to 0.992 for “Taunit-MD”. AO exposure also results in reduction of EMI shielding effectiveness from ∼5 dB to ∼4.2 dB and ∼4.96 dB for epoxy resin with “Taunit-M″ and “Taunit-MD”, respectively, in the frequency range of 8.2–12.4 GHz (X-band) at room temperature.

The effect of oxygen plasma on the structural and optical properties of an epoxy resin with graphene and carbon nanotubes of the Taunit-M series was studied to estimate the resistance of polymer nanocomposites to atomic oxygen attack in low Earth orbits. It was shown that the addition of carbon fillers to epoxy resin resulted in an increase in mass loss and erosion depth when exposed oxygen plasma. The mass erosion coefficient at an atomic oxygen fluence of 30 × 1020 cm–2 is 0.82 × 10–23 g/at. for pure epoxy resin and 0.86 × 10–23 and 1.0 6× 10–23 g/at. for samples with graphene and Taunit-M fillers, respectively. A larger weight loss and erosion depth under oxygen plasma was typical for the sample with the Taunit-M filler compared to the sample with the graphene one. Oxygen plasma exposure resulted in a significant decrease in the reflectance coefficients of carbon nanocomposites in the spectral range 0.2–2.5 µm. The lowest diffuse (less than 1%) and specular (less than 0.02%) reflectance coefficients were achieved for the exposed polymer with Taunit-M filler.

Structural, optical and EMI shielding properties of epoxy resin reinforced with carbon nanotubes fillers "Taunit-M" and "Taunit-MD" have been studied. To estimate the resistance of nanocomposites operating in low-Earth orbits, the samples were exposed to atomic oxygen (AO) in the fluence range of (1.7-30) x 1020 cm-2. AO exposure results in mass loss of epoxy resin with carbon fillers: the erosion yields (Rm) are 1.07 x 10-23 g/atom and 1.21 x 10-23 g/atom for "Taunit-M '' and "Taunit-MD", respectively. Diffuse and specular reflectance noticeably decreases after AO exposure which in their turn leads to increase of solar absorptance from 0.940 to 0.996 for "Taunit-M '' and from 0.944 to 0.992 for "Taunit-MD". AO exposure also results in reduction of EMI shielding effectiveness from-5 dB to-4.2 dB and-4.96 dB for epoxy resin with "Taunit-M '' and "Taunit-MD", respectively, in the frequency range of 8.2-12.4 GHz (X-band) at room temperature.

This paper discusses the reaction mechanism of N, O, and H atom interaction with a single-layer MoS2, two-dimensional transition metal dichalcogenide. These mechanisms were studied thoroughly by DFT (density functional theory) modeling using both static and dynamic approaches, which allowed us to find and analyze the most important processes that occur on the MoS2 monolayer surface under such a treatment. Our calculations demonstrate distinct behavior of thermal N, O and H atoms interacting with pristine and modified MoS2 surfaces: for nitrogen the main processes are scattering and recombination of incident and adsorbed atoms, for oxygen the chemisorption on the MoS2 surface dominates, while hydrogen effects can be considered as intermediate case. Based on simulation results, we propose different mechanisms of defect formation by thermal N, O, and H atoms. Some results of dynamic DFT simulations for thermal and hot atoms to illustrate these finding are presented.

The morphology and physical properties of nanocomposites based on organosoluble polyimides with different chemical structures are studied. Metalloalkoxysiloxanes that differ in terms of the type of the central metal atom and substituent at the silicon atom, namely, tris(3-aminopropyldiethoxysiloxy)chromium, tris(methyldiethoxysiloxy)gallium, and tetrakis(methyldiethoxysiloxy)titanium, are used as precursors of the dispersed phase. It is shown that the difference in the chemical structure of the matrix polymer, provided that the same precursor of the dispersed phase of the nanocomposite is used, manifests itself in a change in the shape and sizes of the nanoparticles formed in the polymer. Filled polyimide films are characterized by a high resistance to atomic oxygen. The values of the erosion coefficients of the nanocomposites based on them when using tetrakis(methyldiethoxysiloxy)titanium are 89% lower when compared to unfilled polyimides. The ability of the filled polymer films to withstand the erosive action of an incoming oxygen plasma is to a greater extent determined by nanoparticles of the dispersed phase. The protective function of nanoparticles increases with an increase in the number of Si–O–Si blocks in their structure which, in turn, is predetermined by the valence of the central metal atom of the precursor. Thus, polyimides with particles based on tetrakis(methyldiethoxysiloxy)titanium are less susceptible to erosion under the action of atomic oxygen when compared to nanocomposites, the dispersed phase of which is formed based on tris(3-aminopropyldiethoxysiloxy)chromium and tris(methyldiethoxysiloxy)gallium. The chemical structure of the matrix polymer has little effect on the values of the erosion coefficients of the filled polyimide films.

The changes in the structure of the surface of K-208 and CMG cover glasses after electron irradiation and the effect of the molecular fluxes investigated by atomic force microscopy (AFM) are presented. It is demonstrated that contamination of the surfaces of glasses irradiated with electrons at flux densities φ from 1010 to 8 × 1010 cm–2 s–1 occurs at electrostatic discharges accompanied by the release of plasmoids into the environment, the particles of which are deposited on the glass. It has been found experimentally that the effect of preliminary irradiation of the glass on the deposition of components of the molecular flow is the most effective just after the irradiation and decreases over time. This is due to the drain of the charge injected into the glass and decrease in the initially high reactive capacity of the substances of the discharge channels. It is also demonstrated that the combined effect of electrons and molecular flux on the glasses significantly increased the discharge frequency at a predetermined value of φ and, as a consequence, led to an increase in the number of the discharge channels on the surfaces of samples. To interpret the experimental results, a mathematical model of the deposition of molecular flow components on glass is proposed.

The influence of electron-proton irradiation on the process of changing the surface structure of K‑208 glass, caused by the formation of gas-filled bubbles and their destruction, is studied by atomic-force microscopy (AFM). These phenomena are associated with the formation of hydrogen atoms H in the process of the recombination of protons with electrons injected into the glass and those that appeared in it during ionization. The migration of hydrogen atoms and their aggregation into H-clusters in the vicinity of glass structure defects leads to the formation of molecular hydrogen (H2) bubbles. The glass is exposed to electrons and protons with energies of 40 and 20 keV, respectively. Irradiation is carried out in a vacuum chamber with a residual pressure of 10–4 Pa. At a fixed value of the proton flux density φр = 5.5 × 1010 cm–2 s–1, the electron flux density φe varies in the range (0–16.8) × 1010 cm–2 s–1. It is shown that the size of the bubbles depends on the ratio of the parameters φe and φр. Analysis of the experimental data suggests that the destruction of a bubble occurs with a local decrease in the thickness of its cap to 10–20 nm, as a result of heating and growth in the direction normal to the surface under the pressure of the accumulating gas. It is also found that electrostatic discharges developing along the irradiated glass surface stimulate the destruction of bubbles.

The formation of gas-filled bubbles, which is one of the indicators and quantitative criteria for radiation degradation of the surface layer of K-208 glass irradiated with 20-keV electrons, and the effect of ITO (indium tin oxide) film deposited on the glass are investigated. Using atomic force microscopy, the nucleation of oxygen bubbles in the surface layer of glass irradiated to a fluence (Φ) on the order of 10 15 cm –2 at a particle flux density (φ) of 2 × 10 10 cm –2 s –1 was detected. Gas-filled bubbles appear on the surface of samples with an ITO film at Φ ≥ 4 × 10 15 cm –2 in smaller amounts but larger sizes than on glass without a film. The formation of oxygen bubbles is explained by the formation of a negative charge region in the surface layer of the irradiated glass, in the field of which sodium ions migrate, which plays a key role in the release of non-bridging oxygen atoms. Migration and aggregation of released oxygen atoms in defective places in the glass grid lead to the formation of gas-filled bubbles.