International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The possibility to produce white Eco-cement with the use of a dry method under low-temperature firing of a raw material mixture based on the CaO – SiO2 – Al2O3 – MgO system is shown. Computer calculations were performed and an analysis of the dependence of the characteristics of cement clinker on the quantitative ratio of raw components was carried out. A new composition of the raw material mixture with a decrease of 19 wt. % amount of the carbonate component and, accordingly, CO2 emissions during combustion was determined. The peculiarities of phase transformations in the material during firing with a maximum temperature of 1100 ᵒС when microtalcum was introduced into the initial mixture with the formation of pericloze, ockermanite and merwinite as a factor in the structure and properties of cement clinker were noted.

Two-dimensional van der Waals (vdW) materials possess novel physical properties and promising applications. A wide range of 2D vdW materials having been obtained via the chemical vapor transport (CVT) method. In this work, we develop the controllable growth meyhod of 2H-NbSe2 single crystals via the CVT method. The quality of fabricated crystals was characterized by X-ray diffraction, and electron dispersive spectrometry (EDS) measurements. Crystals of the best quality were successfully grown under selected temperature/time schedule.

A methodology has been developed for obtaining of porous castings from Al and aluminum A356 alloy. The methodology includes introduction of Ca into the melt for viscosity increasing and homogenization by mechanical stirring. This is followed by addition of TiH2, homogenization, subsequent formation of the porous structure and crystallization. Tests were carried out on specimens of the castings involving abrasive wearing under dry friction conditions on a surface with hard-attached abrasive particles.

Two-dimensional van der Waals (vdW) materials possess novel physical properties and promising applications. A wide range of 2D vdW materials having been obtained via the chemical vapor transport (CVT) method. In this work, we develop the controllable growth meyhod of 2H-NbSe2 single crystals via the CVT method. The quality of fabricated crystals was characterized by X-ray diffraction, and electron dispersive spectrometry (EDS) measurements. Crystals of the best quality were successfully grown under selected temperature/time schedule.

Nowadays, the decrease of CO2 concentration in the atmosphere and/or its utilization need urgent resolution. At the same time, preparation of advanced graphene-based composites through effective environmentally benign procedures remains in the focus of intensive research. In the present work, composites consisted of reduced graphene oxide and nanocarbons (rGO/nC) were prepared by simultaneous reduction reaction of solid graphite oxide and CO2 gas over alkaline earth reductant. The structure and the morphology of the prepared composite material were examined employing X-ray diffraction analysis and scanning electron microscopy. It was revealed that the characteristic narrow peak of the graphite oxide (GtO) at low 2θ (~11o) was not present in the pattern of the composite suggesting its successful reduction. Instead, a broad one positioned at 26o was recorded which was attributed to the formed nanocarbons. The observed accordion-like morphologies typical for reduced-graphene-oxide type of graphene evidenced the detachment of the graphene layers during the thermal treatment, while the formed nanocarbons were with irregular shape. The rGO/nC composite exhibited specific surface area (485 m2/g) higher than the pure nanocarbons (417 m2/g) obtained without addition of GtO. The outcome was attributed to the influence of the layered rGO which hinders the aggregation of the nanocarbons and facilitates their homogeneous distribution. The prepared composite can be considered as candidates for gas and energy storage applications, while the suggested environmentally benign preparation method can be scaled up to industrial extent due to simplicity.

The electrochemical corrosion properties in a 3% NaCl solution of the titanium-based multicomponent composite of the 65TiH2–30FeSiMn–B4C system were investigated. The kinetics and the mechanism of anode dissolution of metals and oxidation of specimens have been studied by using polarization curves, chemical and x-ray phase analyses. It was found a decrease in the titanium carbide peaks on the X-Ray defractions also the titanium silicon carbide almost disappears after immersing the sample in a 3% NaCl solution. Formation of silicon and boride phases of titanium in the synthesis process leads to an increase in corrosion resistance due to the inhibition of the velocities of both the anode and cathode processes.

Biomaterials are becoming an increasingly important research topic over time as they are used to replace parts and functions of the human body, helping to improve the quality of human life. Titanium alloys are particularly important for the development of new biomaterials. Commercial pure titanium and its alloys are used as essential structural biomaterials in the manufacture of implants due to their excellent biocompatibility, good corrosion resistance and mechanical strength. However, studies have shown that aluminum and vanadium ions are released in alloys such as Ti-6Al-4V, which can cause health problems over time. Because of the problems that occur, researchers are working to improve the properties of titanium alloys by adding new elements. In most cases, different metals are added to titanium and it is known that with the presence of different metals, the properties of titanium also change. All biomedical titanium alloys must undergo various testing procedures before they can be used. The article describes the characterisation methods used in the development of titanium alloys, such as: light and scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction analysis, differential scanning calorimetry, differential thermal analysis. The reliability of the results depends on the methods used and the avoidance of errors in the characterisation of biomedical alloys in order to reach better conclusions and produce alloys of the highest quality desirable for use in the human body.

In this paper, the results of the DTA-TGA, SEM-EDS, and FTIR analysis of the corn silk are presented. The DTA-TGA analysis shows that the decomposition of corn silk has several stages which are manifested with corresponding peaks on obtained DTA-TGA curves. SEM-EDS analysis was performed before and after the adsorption of copper ions. It has shown that untreated corn silk has a non-uniform structure, consisting of channels and cavities of irregular orientation, which facilitates the penetration of the water phase into the adsorbent structure, and incorporation of copper ions in the internal active sites. After the adsorption of Cu2+ ions, the structure becomes more compact, and uniform, as a result of the incorporation of copper ions into the molecular structure of the corn silk. FTIR analysis shows that ion exchange is not the dominant mechanism of binding copper ions to the active sites in the molecular structure of the corn silk, but also chemisorption and physical adsorption is present.

The work shows that there is no significant change in the phase composition of composites with a change in the synthesis temperature, so we can use pre-synthesized heats at a temperature of 950 oC to obtain hot-stamped aluminum-based composites. The best characteristics of the synthesized titanium carbide were obtained for the composition 45Al-11C-44Ti (%, wt.). The lattice period of titanium carbide for this sample is 0.4324, and the particle size of titanium carbide formed after sintering is 0.8-1.5 μm. The influence of the component composition of the initial charge on the features of the structure and the phase composition of the thermally synthesized heat of the Al-C-Ti system was established.

In view of the practical applications of the piezoelectric ceramics produced from barium titanate (BaTiO3) and barium stannate (BaSnO3), (the BT-BS system), the dielectric behavior of such materials was studied. The starting components (powder of both BaTiO3 and BaSnO3) were synthesizedand structurally characterized in аdvance. Bulk samples of BT-BS (formed as tablets with addition of PVA plasticizer) were prepared using the sol-gel method by varying the BT-BS composition percentage. The samples were characterized by complex electrical impedance spectroscopy and dielectric spectroscopy in the frequency range from 0.1 Hz to 1 MHz. As compared to BaTiO3, an increase with at least 50 % was measured for the value of the room-temperature dielectric constant (e′ – the real part of the dielectric permittivity) of the BT-BS samples containing 15 wt% BaSnO3. In contrast, the 50 wt% content of BaSnO3 led to a decrease of ′ value of BT-BS by a factor of 3.5, due to relatively low e′ value of BaSnO3. Analyses of the frequency spectra of complex electrical impedance and complex dielectric permittivity revealed the dielectric relaxational behavior of the BaTiO3+BaSnO3 system. The results obtained for ′ of BT-BS dielectrics as a function of the temperature were correlated with the data from structural studies. In particular, a specific enhancement of e′ was observed in temperature range around 120C for the BT-BS samples containing 15 wt% BaSnO3. Corresponding conclusions were done. The effects observed show that the synthesized BaTiO3-BaSnO3 ceramics are promising materials for piezoelectric and dielectric applications, e.g., in energy storage devices.

The object of research – the natural glycoalkaloid solanine as a possible inhibitor of acid corrosion of steel St3. Modern data on the structure and physico-chemical properties of solanine, such as amphiphilicity, surface activity, basicity, characteristic of modern organic corrosion inhibitors, are presented. The basic concepts are defined: basic nitrogen, solanine amphiphilicity, mass and volume corrosion indicators, corrosion inhibitor, degree of protection, corrosion inhibition coefficient. The literature data on the corrosive activity of lactic acid (MC) are presented and characterized.

The time being, one of the greatest concerns is the environmental pollution. Nowadays, various dangerous compounds reach to the air, soil and water. Pharmaceuticals, such as 17α-ethinylestradiol (EE2), are one of the most emerging pollutants in water ecosystems. Hence, powerful but green approaches should be developed in order to completely remove the pollutants. Heterogeneous photocatalysis is a sustainable and efficient process in the removal of organic pollutants, such as pharmaceuticals. ZnO is one of the most commonly used semiconductors but also possess some drawbacks. In this study novel synthesis pathway of ZnO nanoparticles from banana peel extract was
obtained. Besides, the photocatalytic efficiency of the newly synthesized ZnO was examined in the degradation of EE2. Both the eco-friendly ZnO nanoparticles, as well as pure banana peel extract showed a promising photocatalytic activity in the degradation of EE2 under simulated solar irradiation (SSI). Namely, EE2 was completely degraded after 60 min of SSI.