Small-angle neutron scattering, dielectric spectroscopy, and dynamic mechanical analysis data are reported for composites of isotactic polypropylene (IPP) with graphene nanoparticles (GNP) and nanographite. In various samples, the volume of the IPP matrix with a high degree of crystallinity contains GNP with concentrations of 0.7 and 1.8 wt

Методами термогравиметрии, дифференциальной сканирующей калориметрии, рентгенофазового анализа и электронной микроскопии исследованы особенности окисления порошков аморфного бора, модифицированных пентоксидом ванадия. Модифицирование осуществляли путем смешения порошков с ванадийсодержащими гелями — гидрогелем состава V2O5 · nH2O и олеогелем состава V(OCH2)2 · n(HOCH2)2. Установлено, что добавление к порошку аморфного бора 2 % (мас.) V2O5 на 200 °C снижает температуру начала его интенсивного окисления и на 25 % повышает удельное тепловыделение в процессе взаимодействия при нагревании на воздухе со скоростью 10 °C /мин. Взаимодействие бора с пентоксидом ванадия рассмотрено в рамках модели бортермального процесса. The oxidation of amorphous boron powders modified with vanadium pentoxide were studied by thermogravimetry, differential scanning calorimetry, X-ray phase analysis, and electron microscopy. The modification was carried out by mixing powders with vanadium-containing gels: V2O5 · nH2O hydrogel and V(OCH2)2 · n(HOCH2)2 oleogel. It was found that adding 2 wt.% V2O5 to the amorphous boron powder led to a decrease of 200 °C in the temperature at the onset of its intense oxidation and to a 25% increase in the specific heat release during interaction under heating in air at a rate of 10 °C/min. The reaction of boron with vanadium pentoxide is considered within the framework of a boron thermal process model.

Методами термогравиметрии с дифференциальной сканирующей калориметрией и одноволновой эллипсометрии исследована термическая устойчивость и защитные свойства оксидных пленок порошка сплава Al–2.3%V в прессованном и насыпном виде в температурном интервале 25–1200°С на воздухе. С использованием оптических констант, полученных на массивных поликристаллических образцах, исследован рост оксидного слоя и изменение доли металла на поверхности прессованных таблеток порошков исходного алюминия и сплава Al–2.3%V. Объяснено влияние легирующей добавки ванадия на изменение структуры поверхностного оксида порошка алюминия в условиях программируемого нагрева.

The purpose of the work is to characterize the lubricants based on Llitol-24 and synthetic solidol with additives copper(II) carboxylates when using them in friction nodes in loading conditions and temperature. The lubricant compositions with additives copper(II) carboxylates based on synthetic solidol and Litol-24 form the columnar mesophases depending on thermodynamical conditions and concentration of additives.Methods. We study the lubricant compositions with dielectric spectroscopy and и polarization light microscopy. The studies lubricant compositions are tested on the frictional machines by preceding authors, which performed their synthesis and numerical estimations for their geometry parameters. It is shown, that the columnar mesophase formed by the compositions with copper(II) carboxylates simulates favourable tribological conditions for lubrication (reduction of the friction coefficient at the appointed range of additive concentrations and reduction of wear) and unlike to crystalline phases, shows orientation effects at the surface of interacting surfaces of machine elements and devices. These factsmotivate the study of influence of physicochemical properties and composition on mesomorphism of considered lubricant compositions.Results. In our measurements, we found the main dielectric characteristics of two kinds of the lubricant compositions: dielectric constant and dielectric loss, electroconductivity, dissipation factor, the Arrhenius functions are plotted, and the activation energies of the lubricant compositions we study are calculated. The microphotogram for textures of the lubricant compositions depending on temperature and concentrations are received. The differences in mesomorphic properties of the lubricant compositions with additives Cu(II) valerate and isovalerate are confirmed.The conclusion of the work is that the composition of the lubricant is optimized by the choice of additive concentration, the length of the mesogenic chain of the copper(II) carboxylate molecule and its conformation.

X-ray diffraction analysis, ellipsometry, and optical microscopy have been used to study aluminum alloy samples (of Al and Al–2.3

The current state of research on composites containing graphene derivatives as nanofillers is considered. The results of works carried out at the Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences on the synthesis of filled composites based on polylactide and carbon nanofillers, reduced graphene oxide and graphite nanoplates, by two independent methods, ecofriendly solid-phase mixing of components under shear deformations and liquid-phase synthesis, are summarized. A comparative study of the mechanical, thermal, and electrical properties of the composites is performed depending on the production method and the nature of the used nanofillers, and their influence on the structure and complex of properties of the resulting composite materials is established.

Aspects of solid-state processing of nascent disentangled ultra-high-molecular-weight polyethylene (UHMWPE) powders of different syntheses mixed with electrically conductive carbon nanoparticles (NPs) of various types are studied. Effect of multiple parameters of the processing procedures on the electrophysical characteristics of the composite samples is investigated. Such parameters include time of preliminary ultrasonication (US) of NPs, time of US of UHMWPE/NPs mixtures, molding time, temperature, and pressure, deformation degree, etc. It is observed that by selecting optimal values of such parameters it is possible to obtain samples of composites with an extremely segregated structure made of the NPs, with NPs distributed evenly on the surfaces of the compacted UHMWPE powder particles. This ensures high levels of conductivity at very low values of NPs content. The segregated structure is retained when the composites are strengthened using the solid-state uniaxial shear deformation process. While conductivity of most of the composites filled with various types of NPs monotonously decreases with the deformation ratio, conductivity of the composites filled with exceptionally long double-walled carbon nanotubes is maintained. The processed oriented composites are also characterized by high EMR shielding properties, as well as interesting temperature dependencies of the electrical conductivity.

Composites of polyether polylactide (PLA) synthesized from natural raw materials with graphite nanoplates (GNP), which represent a new type of composite materials based on biodegradable polymers, were obtained by solid-phase method under the action of shear deformations. The porosity of composites was evaluated and their electrical and mechanical properties were studied. The effect of UV radiation on the molecular weight and molecular weight distribution of PLA in PLA-GNP composites of different compositions was investigated using the method of excision chromatography (EC), and the effect of the GNP nanofiller content on the change of their mechanical characteristics in the process of radiation was shown.

Purpose of research. The purpose of the study is to explain the mechanisms of clustering of fullerene molecules in liquid media observed using various structural nuclear -physical methods, as well as the interpretation of experimental data within the framework of a microscopic diffusion model. Methods. The article gives a brief overview of the results of positron annihilation spectroscopy, small-angle neutron scattering, translucent electron microscopy, with which the geometric parameters of fullerene clusters in solutions were established. The theoretical method of research is the microscopic diffusion model “Limited diffusion aggregation”, which describes the kinetic processes of clusterization. Results. The diffusion limited aggregation model displays adequately the mechanism of formation of C60 molecules in the form of fractal units in the volume of fluid, observed in experiments on positron annihilation spectroscopy and small-angle neutron scattering. The structural indicators of aggregate fullerene particles in carbon disulfide, o-Xylene, toluene, water and other solvents are analyzed. The properties of various diffusion models (the reaction limited aggregation model and the diffusion limited aggregation model) are considered and their combination in relation to the assessmentsof the kinetics of fullerene aggregation in solutions. A quantitative comparison of the results of the discussed models was carried out using the example of carbon disulfide. Conclusion. The diffusion microscopic models adequately describe the phenomenon of fullerene aggregation in polar and non-polar solvents, which are recorded by various nuclear methods (positron annihilating spectroscopy and small-angle neutron scattering), the most reliable is the diffusion limited aggregation model, more than that, it is the basis of a numerical definition of structural structures parameters of units. Compared to neutron scattering, with the annihilation of positrons, in the aggregation of fullerene the [Ps–C60] molecular complexes participate in the clusterization, but this does not affect the change in the size of the cluster and the reliability of the results.

The growth of an oxide film on the surface of polycrystalline β-rhombohedral boron during thermal oxidation in air at temperatures of 400, 500, 600, and 700°C was studied using in situ single-wave ellipsometry. At temperatures above the melting point of B2O3, the oxidation was significantly activated. Having reached its maximum at 500, 600, and 700°C, the thickness of the oxide film decreased. This is attributed to the dynamic equilibrium between the processes of evaporation of liquid oxide and film growth caused by the diffusion of boron and oxygen ions. The refractive index of the substrate (pure boron) decreased from 3.1 to 2.95 during the annealing due to a change in its porosity. It was established by Raman spectroscopy that after annealing at 700°C, the surface contained not only the oxide B2O3, but also traces of suboxide B6O, previously observed during the oxidation of boron at higher temperatures.

Nanocomposites of polylactide with graphite nanoplateletes (GNPs) and reduced graphene oxide (RGO) are prepared by liquid-phase synthesis. A comparative study of the mechanical, electric, and thermophysical characteristics of the compositions depending on the nature of the nanofillers is carried out. An insignificant difference in the mechanical parameters of the compositions containing GNPs and RGO is established. At the same time, when studying the electrical properties, it is found that the use of RGO as a filler produces of composites with a lower percolation threshold than in the case of GNPs and increased conductivity. The differential scanning calorimetry (DSC) method shows that compositions containing GNPs have higher degree of crystallinity in comparison with similar compositions containing RGO. This is caused by the structure of the filled compositions, which influences the nucleation rate of polylactide (PLA) crystallites on the surface of ordered planar nanoparticles of GNP and imperfect RGO particles. Thus, the use of different carbon nanofillers may promote the production of compositions that differ in their characteristics.

AbstractThermogravimetry, combined with differential scanning calorimetry and single-wave ellipsometry, was used to study the thermal stability and protective properties of oxide films of Al-2.3% V alloy powder in compressed and bulk forms over a temperature range of 25-1200 degrees C in air. Optical constants measured on massive polycrystalline samples were employed to examine the growth of the oxide layer and the change in the metal content on the surface of the initial aluminum and Al-2.3% V alloy powders compressed into tablets. The influence of the vanadium alloy additive on the structural changes of the surface oxide of aluminum powder under conditions of programmable heating was explained.

Basing on the data of small-angle neutron scattering for the nanocomposite composed of fullerene C60 (16.5 wt. %) in the matrix of isotactic polypropylene, we received information on clusterization of nanoparticles and defined their geometric parameters and dimensionality. In this paper, we propose interpretation of particle aggregation possessing the properties of surface fractal in the size range up to 80 nm observed using small-angle neutron scattering method. Basing on the well-known theories of defect structures of a fullerene molecule C60 in non-Euclidean metrics, in particular, of disclinations and monopole in two-dimensional spherical Gödel space—time, we formulate a lattice version for the action of monopole gas, in which with the lattice Monte Carlo method, using abelian projection, we estimate the energy of monopole currents at different monopole concentrations. In frames of the proposed model, it is possible to calculate fractal properties of the fullerene C60 in a polymer composite and also to interpret evolution of disclinations.

The plastic properties of specimens of Al — 2.3% V alloy and A85 aluminum, obtained by the method of selective laser melting, have been studied. Ultimate plasticity diagrams of these materials were plotted. It was found that the ultimate plasticity of the studied materials significantly depended on the deformation conditions (the type of stress state, which is characterized by the Lode—Nadai coefficient μσ). Thus, under tensile and shear test conditions (–1 ≤ μσ ≤ 0), the ultimate plasticity of the studied materials is practically the same. In the case of tests on extrusion of the bottom of a thick-walled cup (μσ = +1), the ultimate plasticity of the Al — 2.3% V alloy is approximately twice as high as that of primary aluminum under tensile stresses and by 30% higher under compressive stresses.

Создание композиций на основе полимеров и наполнителей различной природы вызывает в настоящее время большой интерес. Получение композиций с использованием в качестве наполнителей производных графита позволяет создавать материалы с улучшенным комплексом свойств, что может значительно расширить сферы применения синтетических и природных полимеров различных классов.

Based on small angle neutron-scattering data from a nanocomposite composed of fullerene C60 (16.5 wt

X-ray diffraction analysis, ellipsometry, and optical microscopy have been used to study aluminum alloy samples (of Al and Al-2.3% V) fabricated by 3D printing using selective laser melting. The mechanical properties of the resultant products have been compared. The strength and plastic properties of parts made from pure Al and Al-2.3% V alloys have been found to be insensitive to heat treatment. The addition of vanadium to pure Al showed that the Al-2.3% V alloy has significantly improved performance properties compared to those of primary aluminum, without affecting its initial plasticity.

Thermogravimetry, combined with differential scanning calorimetry and single-wave ellipsometry, was used to study the thermal stability and protective properties of oxide films of Al–2.3