Key Engineering Materials Vol. 910

Abstract: Nonwoven fibers from biodegradable polymers such as polylactide and poly-3-hydroxybutyrate were obtained by electrospinning. The fiber morphology was studied by optical microscopy. The fiber materials were used like the substrates for the plant growing. The sowing qualities of the "Athena"winter wheat (triticum aestivum L.) and biometric indicators of the plants were determined. The biometric indicators of wheat plants grown on polymer substrates are higher compared with the GOST technique. Eco-friendly fiber materials are promising for the agricultural application. Polylactide and poly-3-hydroxybutyrate undergo a hydrolysis process. They are destroyed to form nutrients for the growth and development of wheat plants.

Abstract: The combination of natural additives with synthetic polymers allows the development of environmentally friendly materials with increased biodegradability. In this article, we investigated composite films based on low density polyethylene (PE) with different content (10-30 wt %) of natural rubber (NR). A mycological test with fungi and a full-scale soil test revealed that the composite with 30 wt% NR was the most biodegradable (weight loss was 7.2 wt % over 90 days). In the experiment on biodegradation in soil, the most intensive development of filamentous fungi was recorded in field tests. However, the rate of weight loss by samples of PLA-LDPE compositions when exposed in natural conditions is significantly lower than the rate of weight loss in laboratory tests. Thus, the present study was carried out to analyse the effect of various additives of biodegradable polymers on biodegradation in soil.

Abstract: The work is devoted to the problem of synthesis of coatings based on titanium carbide. Methods for obtaining coatings using femtosecond laser radiation and a CO₂ laser are considered. The differences in mechanisms of titanium carbide synthesis, as well as the areas of application of technologies, are described. The Raman spectra of the obtained coatings are presented and analyzed. It can be judged that as a result of laser treatment, titanium carbide was formed.

Abstract: The article is devoted to the method of obtaining a diamond-like coating on a silicon substrate by laser ablation of a glassy carbon target in a vacuum. The presented technology makes it possible to achieve the synthesis of wear-resistant thin-film coatings with a thickness of about 200 nm. The diagnostics of the obtained coating was carried out using probe microscopy, the chemical and phase composition was estimated by the Raman spectra.

Abstract: The authors carried out complex studies of a composite multilayer high-entropy coating obtained by HVOF in a protective atmosphere. They also investigated metallophysical properties of the coating (using electron microscopy and X-ray diffraction analysis) in order to obtain new information on its composition, mechanical properties, and phase composition. Functional properties of the high-entropy layer were also determined. The effect of mechanical activation of powders on the structural-phase state and quality of the layered coating has also been studied. On the basis of complex metallophysical studies, they investigated the formation of a structure in a composite multilayer high-entropy coating after HVOF in a protective atmosphere and subsequent thermomechanical treatment. Calorimetric tests of the functional high-entropy layer were carried out to reveal the exo effect corresponding to the manifestation of phase transformation. The mechanical properties of steel with a multilayer composite coating have been determined.

Abstract: The study of the influence of the physical and mechanical properties of concrete on various hydraulic binders on the corrosion resistance of steel reinforcement has been carried out. As a binder, the following were considered: CEM I 42.5 N and a slag-alkaline binder (SAB) based on ground granulated blast-furnace slag of Novolipetsk Metallurgical Plant (NMP). For comparative tests, concretes of class B 25 (M300) were used on granite aggregate with a fraction of 2,5-7,5 mm. Indicators of physical and mechanical properties such as: compressive strength, porosity, water absorption coefficient and weight loss coefficient of reinforcement at the age of 28, 90 and 180 days are criterial. 5 % aqueous solutions of NaCl, Na₂S0₄ were used as working media in assessing the corrosion resistance of reinforcing steel; MgS0₄. It has been established that steel reinforcement in slag-base concrete (SBC) has high corrosion resistance, both in an aqueous solution of NaCl and in solutions of Na₂S0₄ and MgSO₄. Slag-alkali concretes are characterized by low porosity, lower water absorption coefficient in comparison with concretes based on Portland cement.

Abstract: This work aims at investigating the stages and irregularity of plastic strain in austenitic stainless steel 12Kh18N9T within a temperature range of 143 < T < 420 K. The localized plastic strain fronts at different stages of strain hardening have been visualized and monitored via digital speckle photography (DSP). This method consists in the high-accuracy recording of the displacement field via tracking any material surface changes and the subsequent comparison of speckle images acquired under uniaxial tension. The stress-strain diagrams were found to strongly vary with a decrease in temperature due to strain-induced-phase transition. The analysis of localized strain distributions revealed the emergence of a mobile system of equidistant strain localization foci at the strain hardening stage. The temperature dependence of plastic strain localization parameters at the linear strain hardening stage was established as well.

Abstract: The mechanorheological viscoelastic plastic model was used to study the effect of impact speed on the dynamics of mechanical interaction of a spherical body with the surface. An analysis of the impact process made it possible to draw some conclusions. The impact interaction time depends on the impact speed and mechanical properties of the material. The impact time decreases with an increase in the impact speed, a decrease in plasticity, and an increase in elasticity. With an increase in the impact speed, the impact time decreases. During the experiment, the initial impact speed increased 10 times. During the impact interaction, the body deformation increased 6-7 times. According to the calculations, the average body deformation speed also increased 10 times. As a result, the time for travelling a distance equal to the elastic and plastic deformation when loading bodies and the elastic deformation when unloading bodies decreased. The total deformation is composed of elastic and plastic components. With an increase in the impact speed, the plastic component increases, which decreases the unloading time due to a decrease in the elastic component. The impact time is an important characteristic of the dynamic process of interaction. Therefore, when identifying theoretical models to the real processes, these parameters should be congruent. To improve the modeling accuracy and reliability for various technological processes under dynamic loads, it is necessary to take into account various factors.

Abstract: The paper presents the results of tests of HPC (high performance composites) samples consisting of aramid and glass fabrics modified by agglomerates of WC and WO₃ nanopowders. According to the test results, introduction of WC and WO₃ powders into the composite plate structure makes it more rigid and elastic, increasing its ability to dissipate energy.

Abstract: In connection with the gradual development of deep oil deposits, it is necessary to develop deposits at a depth of no more than 3000 m. For the production of such oil, the method of hydraulic fracturing with the injection of hydraulic fracturing fluids and proppants under high pressure is actively used. Proppants are used as proppants, which are granular bulk material. Their application depends on the depth of the well and the composition of the reservoirs. In the process of oil production, a large amount of drill cuttings is formed, which must be processed and used as raw materials, for example, for the production of aluminosilicate proppants. This paper discusses the possibility of using drill cuttings, ground cullet and alkali to obtain proppants. To achieve this goal, studies of drill cuttings were carried out, a technology for obtaining aluminosilicate proppants and raw mixtures was developed, during the molding of which the studied samples were fired and underwent the necessary studies, on the basis of which the corresponding conclusion was made.