Архив

Tribotechnical characteristics of elastomers based on SKI-3 isoprene rubbers and hybrid filler carbon black/carbon nanotubes (Taunit-M) produced by “Nanotechcenter” were studied in the paper. The content of carbon nanotubes in rubber mixtures was 0.5 wt. h. per 100 wt. h. of rubber. Asphalt concrete of grades I-II from a hot mixture of type A on bitumen BND60/90 was used as a counterbody. The experiments were carried out at rolling speeds from 60 to 80 kmh–1 and normal loads of 3.0–3.5 kN. The measurement error did not exceed 2 %. It was experimentally shown that when the normal load varies, the dependence of mass wear on the rolling speed does not change its character. This behavior of elastomeric materials fully corresponds to the Archard wear model, according to which wear is directly proportional to normal load and rolling speed. An increase in the mass wear value of Jm with an increase in load is associated with an increase in adhesion in contact. The maximum difference in the mass wear value of Jm during tests at the speed of 80 km/h and the load of 3.5 kN for SKI-3 rubber and rubber/carbon filler reached 2 times. The use of carbon nanostructures reduced the amount of mass wear by almost 40 %. Therefore, the use of carbon black/carbon nanotubes filler for rubbers is a promising method for improving their tribotechnical properties.

The paper discusses the possibility of realizing ionic conductivity in graphene-like layers containing impurity boron atoms. Currently, the search for new batteries is an urgent task. This is due to a number of disadvantages of modern materials, in particular, lithium-ion batteries are characterized by easy flammability, combustibility and the formation of dendritic structures with repeated use. Quantum-chemical studies of the vacancy migration process identified with the ion movement on the nanolayer surface have been performed and the effect of substituting B atoms on the phenomenon under study has been determined. The results of computer modeling of the defect movement on the surface with nanolayers containing a different number of impurity atoms – from pure graphene to the so-called “borophene”, i.e., a nanolayer consisting entirely of boron atoms are presented. It is established that with an increase in boron atoms impurity, the height of the potential barrier decreases, which makes the realization of ionic conductivity in boron-containing nanolayers more effective than in pure carbon ones. The direct relationship between the concentration of impurity boron atoms in the nanolayer and the height of the potential barrier has been unambiguously determined. The results presented in this article were obtained using the molecular cluster model and the DFT calculation method with the exchange-correlation functional B3LYP (valence-split basis set 6-31G).

Optical properties of carbon nanotubes depend on their geometric dimensions, presence of defects and availability of functional groups; all this is important to consider when choosing carbon nanotubes for specific photo-thermal and other processes. The present study investigated temperature differences between colloidal suspensions under the influence of sunlight, due to the difference in the rate of photo-thermal transformation (as a result of optical absorption). It was found that as the size of carbon nanotubes decreased, the optical absorption increases and its peak shifted to the blue side. Oxidized carbon nanotubes demonstrated an increase in overall optical absorption compared to non-oxidized carbon nanotubes. The optical absorption peak corresponding to π-plasmon in oxidized and non-oxidized carbon nanotubes of the Taunit-M and Taunit types was at values of 1.96, 1.25 and 1.13, respectively. Also, the temperature of colloidal suspensions and the rate of their heating increased with a decrease in the size of carbon nanotubes. As a result of the research, the carbon nanotubes type most suitable for specific use in optical absorbing devices (such as solar collectors) was determined based on the carbon nanotubes ratio to the target electromagnetic spectrum.

Due to the importance of conducting materials science research according to Critical Technologies of the Russian Federation and taking into account the demand for lithium fluoride-based matrices for UV and IR spectroscopy, laser technology and biomedicine, the paper highlights the advantages and prospects for the process of structuring the surface of the LiF matrix material with nanoobjects. Spectral characteristics (changes in transmission and reflection), mechanical parameters (microhardness), as well as the wetting angle of the lithium fluoride LiF surface modified with carbon nanotubes are considered; in comparison with those data for pure LiF crystals. The innovative laser-oriented deposition (LOD) technique and additional electric field varied in the range of 100–600 Vcm–1 are applied to structure the surface of the materials and deposit nanotubes in the vertical position. An extensive package of experimental results obtained is quite well confirmed by quantum chemical modeling.

In recent years, it has become necessary to determine the calorific value of pure combustible substances, since the error of the previously used formula by D.I. Mendeleev reaches 20 %, which is not acceptable. The method for determining the calorific value by M.S. Karash is also widely known. This method is based on the interaction principle between the electron fields of atoms and atomic groups – any interaction of the atom fields is accompanied by a change in the energy of the system. According to the Karash method, the calculated calorific value refers only to the liquid state, while for each class of organic compounds its own calculation formula is proposed, taking into account correction factors for all atomic groups. The need for at least a quantitative account of the molecule structure and the mutual arrangement of atomic groups complicates the calculation. The authors of this work have found a relationship between the calorific value of substances with a negative oxygen balance and the value of oxygen balance. The formula calculated by the authors has the form QL = 0.1387∙OB, MJ∙kg–1 and only one variable (oxygen balance). The determination accuracy is not worse than using the well-known formula by D.I. Mendeleev (6 variables), but the calculation is much simpler.

The paper substantiates the probability of solving a wide range of problems dealing with environmental protection from technogenic pollution with the help of activated carbons (ACs). One of the most important areas of protection against ecocide is detoxification of farmland soils from herbicide residues. It has been established that vegetable waste from agricultural crops, especially straw, is a valuable multi-tonnage raw material for the production of activated carbons. Activated carbons have been produced from a wide range of vegetable waste: straw (16 types), husks and sludge of coffee beans, husks of grains and sunflower stalks, rice husks, as well as nut shells and seeds of fruit trees. The adsorption properties (adsorption activity for iodine and methylene blue), porous structure parameters (total pore volume, mesopore volume, micropore size, total specific surface area, etc.) and other quality indicators of produced vegetable activated carbons (bulk density, mass fraction of ash, strengthat abrasion) have been evaluated. Detoxification of soils from the remains of potent herbicides – Singer SP (active ingredient metsulfuron-methyl) has been studied. The fields of application of the produced vegetable ACs in various fields of adsorption technology have been proposed.

In this paper a sample of an experimental annular four-stage thermoacoustic engine with a traveling wave was created in order to measure its performance, as well as to determine the optimal length of the cavities between the heat exchangers and the end surfaces of the stages. The engine stage diameter was 32 mm, the diameter of the resonators connecting the stages was 13 mm, and the total length of the ring resonator was 4.9 m. When thermal energy was supplied to the engine at a power of 88 W to 480 W, measurements of the amplitude distribution of pressure fluctuations in the resonator, acoustic power, and other parameters were made, in particular: electric heating power of each hot heat exchanger, pressure fluctuations at seven different points of the resonator, frequency of acoustic vibrations, temperature of each of the heat exchangers. In order to determine the optimal dimensions of the length of the cavities between the heat exchangers and the end surfaces of the stages, studies on the dependence of engine characteristics on the length of these cavities were carried out. It was shown that the optimal size of the cavities for a step with a diameter of 32 mm was in the range from 0 to 6 mm.