Journal of Chemical Technology and Metallurgy

STUDY OF SOLUBILITY PROPERTIES OF COMPONENTS IN ACETATE UREA - TRIETHANOLAMINE - WATER SYSTEM

Eldor Khusanov, Zhamshid Shukhurov — Tue, 07 May 2024 00:00:00 +0000

In this work, in order to synthesize new physiologically active substances, the solubility properties of the components in the acetate urea triethanolamine water ternary system were studied by observational polythermal method at a wide range of concentration and a temperature range from -43°C to 18°C. The solubility diagram of the studied system was constructed and the crystallization areas of all substances acetateurea, triethanolamine, ice and the new compound С₃Н₈O₃N₂∙N(C₂H₄OH)₃ acetate ureatriethanolammonium were separated. The composition of the new substance С₃Н₈O₃N₂∙N(C₂H₄OH)₃ was determined using the chemical analysis method. In order to determine optimal conditions for the synthesis of С₃Н₈O₃N₂∙N(C₂H₄OH)₃ acetate ureatriethanolammonium, which has a new physiologically active property, the rheological properties of the solution were studied by adding triethanolamine to 60, 70 and 80 % acetateurea. A “composition-property” diagram was constructed based on the rheological properties of the studied system, the рH indicator, the density and viscosity of the solution, and the refractive index. The optimal conditions for the synthesis of the new substance С₃Н₈O₃N₂∙N(C₂H₄OH)₃ acetate ureatriethanolammonium, obtained by the ratio of components, were determined by adding triethanolamine to a 60 % acetate urea solution.

THE DEPENDENCE OF ACID-BASE EQUILBRIA AND ACIDITY CONSTANTS OF CONGO RED IN BUFFER SOLUTIONS ON THE IONIC STRENGTH

Sokaina Saad Hemdan — Tue, 07 May 2024 00:00:00 +0000

In this study, the spectrophotometric studies of aqueous ethanol solution of Congo red in various buffers solutions at room temperature 25oC and at different ionic strength of 0.05, 0.1, 0.3, and 0.5 KCl mol L-1 were investigated.
The acidity constants of Congo red were estimated by three different methods. The two protonation stages were observed in pH range 2 - 4 and 4 - 6 as result as protonation of amino group and azo groups. The dependence of absorption spectra of Congo red on the ionic strength of solutions which exhibited blue shift with increases ionic strength in addition the shape and intensity were varied. Therefore, the acid-base equilibria shifted toward the higher pHs with the rise in ionic strength. Also, the acidity constants were affected by the ionic strength which the acidity constants decrease with increasing ionic strength of solution because the electrostatic interaction force increased.

STUDY OF SOLUBILITY OF CO(NH2)2 - HOOC - COOH · NH2C2H4OH - H2O SYSTEM

Tue, 07 May 2024 00:00:00 +0000

In this work, the interaction of components in the CO(NH₂)₂ - HOOC - COOH ·NH₂C₂H₄OH - H₂O system was studied by visual polythermic method in the temperature range from -11.2 to 61°C. A polythermal solubility diagram of the system was constructed and the crystallization sites of ice, urea, monoethanolammonium oxalate, and the new phase ureamonoethanolammonium oxalate were determined.
During the addition of monoethanolammonium oxalate to urea solutions of different concentrations, changes in rheological properties (pH, density, refractive index, viscosity) were recorded, and the results were found to be consistent with the polythermal solubility diagram. A new phase formed during the study of the CO(NH₂)₂ - HOOC-COOH · NH₂C₂H₄OH - H₂O system, ureamonoethanolammonium oxalate, was isolated and analyzed by confirmed using appropriate analytical methods (IR, Thermal, X-ray phase).

PROCESSING OF A WASHED DRY CONCENTRATE CONTAINING 26% P2O5 INTO AMMOPHOSPHATE, SULPHO- AND NITROAMMOPHOSPHATE FERTILIZERS

Tue, 07 May 2024 00:00:00 +0000

The process of obtaining ammophosphate by means of phosphoric acid decomposition of washed dried concentrate (WDC) with 26 % Р₂О₅ and 10 % СО) - raw material for the production of thermally fired concentrate, has been studied. The extraction phosphoric acid contains (mass. %): 16.46 P₂O₅, 0.06 CaO, 1.11 MgO, 0.27 Fe₂O₃, 0.41 Al₂O₃, 2.98 SO₃ and 0.99 F. The mass ratio of WPPA: WDC ranged from 100: 10 to 100: 30. Then acidic phosphate pulps (at 65°C) after 45 minutes were ammoniated to pH = 3.8, granulated and dried at 85 - 90°C. It has been shown that the nitrogen content in the finished product ranges from 4.92 - 7.11 %, total phosphorus (P2O 5t.) 41.48 - 46.44 %, phosphorus assimilated by plants (P2O5acceptable) 34.79 - 45.11 %, water-soluble phosphorus (P2O 5w.s.) 23.49 - 37.73 %. The addition of 5 - 7.5 % H₂SO₄ or HNO₃ in the form of a monohydrate makes it possible to intensify the process of phosphoric acid decomposition of phosphate raw materials and to obtain sulfo- and nitroammophosphate with significantly high
contents of P₂O₅acceptable and P₂O₅w.s.. So, with a weight fraction of WDC equals to 30 and weight fractions of H₂SO₄ - 5 and 7.5, there have been 37.6 and 34.47 % P₂O₅total in sulfoammophosphate; 24.11 and 22.06 % CaO t. , 88.75 and 96.4 % P₂O₅acceptable: P₂O_5t., 77.39 and 79.54 % P₂O₅w.s. : P₂O_5t., 6.03 and 7.08 % nitrogen, respectively. In the case of using HNO3, nitroammophosphate contains the largest amount of nitrogen due to additionally introduced nitric acid, but the phosphate raw material has a relatively low decomposition coefficient. The strength of granules of all brands of fertilizers averages 3.50 MPa and are quite suitable for bulk storage and transportation. Material balances for the production of ammophosphate, sulfoammophosphate and nitroammophosphate have been calculated.

BIOACTIVE PROPERTIES AND MORPHOLOGICAL FEATURES OF HYDROXYAPATITE/ZINC OXIDE HYBRID REINFORCED BIO-BASED EPOXY RESIN COMPOSITES FOR DENTISTRY

Tue, 07 May 2024 00:00:00 +0000

In this work, hybrid reinforced epoxy biopolymer composites were developed using natural hydroxyapatite and zinc oxide (nHAp/ZnO). The epoxy was reinforced with varying addition of nHAp and ZnO in the steps of 3, 5 and 7 wt. % respectively using stir casting molding process. The developed composites were immersed in simulated body fluid (SBF) at 37oC to determine their bioactivity. Microstructure evaluation using scanning electron microscopy was also used to assess the morphology of the developed composites before and after in vitro test, respectively.
The microstructure evaluation in vitro showed good deposition of white-like layers on the surface indicating good bioactivity reaction with the SBF and affirm that the developed biopolymers will react well with living tissue when used in vivo. However, hybrid sample BP5HB showed better apatite-like layer deposition.

INVESTIGATING THE EFFECT OF HYDROGEN PEROXIDE ON PHOTOCATALYTIC DEGRADATION OF COMMERCIAL PARACETAMOL USING TiO2

Khoiriah Khoiriah, Reza Audina Putri, Ratnawati Ratnawati, Mega Puspita Sari — Tue, 07 May 2024 00:00:00 +0000

The role of hydrogen peroxide on paracetamol degradation was investigated. Photocatalysis system contains UV radiation and commercial titania (TiO₂ ) as catalyst. The parameters studied for optimal photocatalysis conditions were catalyst dose (0.05 - 0.2 g), initial concentration of paracetamol (5 - 20 mg L-1), and irradiation times (0 - 210 min). Optimal condition obtained by determining the changes of paracetamol concentration converted to be degradation percentage. The influence of hydrogen peroxide concentrations (1 % - 7 %) on photocatalysis TiO₂system was studied. The highest paracetamol degradation was obtained at addition of 3 %. It gives positive effect on degradation process. Thus, hybrid process (UV / TiO₂ / H₂O₂ ) is more effective in comparison to the process UV/ TiO₂ and UV/H₂O₂. Paracetamol (5 mg L-1) was degraded about 90.80 % using 0.1 g TiO₂ , 3 % H₂O₂ addition for 180 min. According to the GC-MS analysis results, paracetamol degradation forms new less toxic by-products. The hybrid process is an alternative technique for degradation of wastewater containing paracetamol.

ANTIBACTERIAL AND ANTIOXIDANT ACTIVITY OF COSMETIC CREAMS WITH EXTRACTS OF DRY FLOWERS AND FRUITS OF SAMBUCUS NIGRA L. - USE OF SAMBUCUS NIGRA L. AS A NON-TRADITIONAL CHEMICAL PRESERVATIVE

Tue, 07 May 2024 00:00:00 +0000

Natural ingredients rich in antioxidants and polyphenols in the forme of extracts, essential oils, organic acids have been used in the production of different cosmetic products. In the development of new cosmetic compositions, or the improvement of products already implemented in production, the evaluation of the user is of great importance, as it directly affects the demand for a given product. The present study aimed to produce phytocosmetic creams based on stearic acid with extracts of dry flower and fruit juice of Sambucus nigra L. (S. nigra) and to investigate
in parallel their potential as substitutes for conventional preservatives. The obtained creams were determined for minimum inhibitory, and minimum bactericidal activity using three bacterial strains (Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC25923, Bacillus subtilis ATCC 6633). In addition, the antibacterial effect of creams against Escherichia coli (BW 28357) was determined. In our experiments we found that addition of dried flower extracts or elderberry fruit extracts from S. nigra in the emulsion does not disturb the compositional system. In conclusion, according to the results, the Sambucus nigra L. extracts from dry flowers and elderberry fruits
are appropriate for use in cosmetic emulsions that demonstated antioxidant stability and antibacterial properties.

REVIEW ON THE SYNTHESIS OF ALPHA-LIPOIC ACID AND ITS THERAPEUTIC POTENTIAL IN EXPERIMENTAL MODEL OF DEMENTIA

Hristian Staykov, Reni Kalfin, Lyubka Tancheva — Tue, 07 May 2024 00:00:00 +0000

LA or (±)-α-Lipoic acid (6,8-thioctic acid, 5-(1,2-dithiolan-3-yl)pentanoic acid) (LA) is a heterocyclic thia fatty
acid consisting of pentanoic acid and a 1,2-dithiolan-3-yl group at the 5-position. LA is an amphiphilic pharmacophore
with excellent antioxidant, anti-inflammatory and neuroprotective effects attested by numerous studies for its potential
utility in both the treatment and diverse forms of prophylaxis of neurodegenerative disorders, especially Alzheimer’s
disease. This article aims to assess the differences in neuroprotective effect after short-term (11 days) and longterm
(51 days) LA administration in an experimental rat model of scopolamine-induced dementia by correlating
biochemical data on acetylcholinesterase activity with behavioural data. Behaviourally appraised changes in learning
and memory appear to correlate with biochemical changes in AChE activity. The neuroprotective effect of LA, as
ascertained by its beneficial effects on learning and memory in a scopolamine animal model, appears to be associated
with cholinergic mechanisms (a decrease in AChE activity), and to be larger after short-term administration rather
than long-term administration. These results further underscore the candidacy of LA as a viable drug candidate
suitable for continued investigation and derivate synthesis endeavours.

SYNTHESIS OF Ag-MODIFIED TiO2 SOL-GEL FILMS AND ITS APPLICATION AS PHOTOCATALYSTS FOR METHYLENE BLUE DEGRADATION

Tue, 07 May 2024 00:00:00 +0000

In the study, the photocatalytic activity of TiO2 films that are created by dip-coating from a sol that contained titanium (IV) isopropoxide, monoethanolamine, and 2-methoxyethanol is demonstrated. Through photo-fixation of Ag (I) ions with varied concentration (10^-2 - 10^-4 M) in the water phase under UV illumination, the films are subsequently surface-modified with Ag co-catalyst layers. Scanning Electron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), Ultraviolet-Visible (UV) Spectroscopy, and Electron Paramagnetic Resonance (EPR) techniques are used to physically characterize the samples. Results reveal that the modification of the co-catalyst had no impact on the thickness and porosity of the films. In addition, the study show that the modified TiO₂ films had increased photocatalytic activity. All the characterization methods used have shown the formation
of surface - bound Ag (I) species and metallic silver nanoclusters. By measuring the Methylene Blue (MB) dye degradation under UV light illumination, as - prepared and Ag -modified TiO2 films are evaluated for their photocatalytic activity, and the impact of the silver precursor concentration during photo-fixation is investigated.
The highest catalytic activity is seen for films that have been modified at a concentration of Ag (I) of 10^-2 M. Ordered from highest to lowest, the MB photodegradation rate constants are TiO₂ < TiO₂ /Ag, 10^-4 < TiO₂ /Ag, 10^-3 < TiO₂ / Ag, 10^-2.

DIVERSITY AND PHYTATE-DEGRADING POTENTIAL OF YEAST MICROORGANISMS ISOLATED FROM SOURDOUGH

Tue, 07 May 2024 00:00:00 +0000

Phytases, which perform the stepwise hydrolysis of phytic acid to myo-inositol and inorganic phosphate, are used worldwide to reduce phosphorus pollution and improve nutrition in monogastric animals and humans. Yeasts isolated from their natural environments represent rich and still underexplored sources of industrially valuable enzymes, including phytases; therefore, they are widely studied for the production of these enzymes. In this regard, thirteen yeast pure cultures were isolated from the microbial consortium of four types of sourdough obtained during the natural fermentation of different grain-based flours. Ten of the newly isolated yeast strains were selected as potential phytase producers based on their growth in liquid culture media with sodium phytate as the sole source of phosphorus. Using 18S rDNA and D1/D2 26S rDNA analyses, the species affiliation of the selected isolates was established. They referred to seven yeast species from 3 families, with the most significant representation of the family Saccharomycetaceae.
Intracellular phytate-degrading activity was found in 8 isolates, the highest being in Nakaseomyces glabratus strain 7-4. The highest level of extracellular phytase was measured in Pichia membranifaciens strain 5-2. Both isolates showed significant antioxidant capacity higher than those of ascorbic acid.

RESOURCE-SAVING WHEAT STRAW PROCESSING TECHNOLOGY

Iryna Trembus, Nazarii Mykhailenko — Tue, 07 May 2024 00:00:00 +0000

The wheat straw delignification condition influence in the medium “acetic acid-water-hydrogen peroxide-citric acid catalyst” to the yield and cellulose product composition was studied. It was established that the fibrous semi-finished product output and the residual lignin content are decrease with increasing temperature and delignification duration. The oxidative wheat straw delignification process was described by a first-order kinetic equation, and it was characterized by low activation energy values of 16.7 kJ mol-1. The oxidized cellulose sample’s structure was studied using IR spectroscopy.

STUDY OF THE INFLUENCE OF CONSERVATION TREATMENT ON THE CHROMATIC CHARACTERISTICS OF ARABIC MANUSCRIPTS

Iordanka Ivanova, Iskren Spiridonov, Rumyana Boeva — Tue, 07 May 2024 00:00:00 +0000

In the present experiment, a study was conducted to investigate the effect of conservation treatment of an Arabic manuscript on its chromatic characteristics. For this purpose, extremely valuable, unrestored manuscripts (18 - 19th century) were selected from the archives of the National Library “St. St. Cyril and Methodius”, on which spectrophotometric chromatic characteristics were measured. The research was conducted at the restoration center of the National Library. The following processes were applied to the manuscript: mechanical cleaning and
deacidification. Measurements of color characteristics were taken indifferent parts of the manuscript after each stage of the treatment: before treatment, after mechanical cleaning, after deacidification. The following parameters - CIE Lab, CIE Lch, ∆Eab, ∆E2000, ∆L, ∆c, ∆h was calculated. Based on the results obtained, the changes and effects of each of the chromatic parameters were determined.

PHYSICO-CHEMICAL ANALYSIS OF QUARTZ SAND AND TECHNOLOGICAL WASTE USED AS A MAIN RAW MATERIAL FOR GLASS PRODUCTION

Khidir A. Adinaev, Zulayhа R. Kadyrova — Tue, 07 May 2024 00:00:00 +0000

The composition and structure of Sherobod quartz sand and man-made waste were fully investigated using chemical, scanning electron microscope, X-ray, infrared spectroscopic and differential thermal analysis methods. It was found that the content of lead and manganese oxides in Handiza lead concentrate and manganese waste is 25 - 26 %, respectively, and silicon oxide in Sherabad quartz sand is more than 80 %. According to the results of chemical and physico-chemical analyzes of Sherabad quartz sand and man-made waste, it was found that they can be added as glass components by cleaning them from various additives.

APPLICATION OF SPARK PLASMA SINTERING AS A METHOD FOR PRODUCING NEW CERAMIC MATERIALS FROM SILICON PRODUCTION WASTE

Gulzhainat Akhmetova, Gulnara Ulyeva, Kurmet Tuyskhan, Irina Volokitina — Tue, 07 May 2024 00:00:00 +0000

The article presents some existing methods of producing silicon carbide, forms and types of silicon carbide, various compositions and formulations, production technology. The authors proposed a new method of processing silicon production waste - microsilica by spark plasma sintering with a carbon-containing reducing agent (soot) which produces a silicon carbide compound. Studies have shown that sintered silicon carbide has improved strength properties. Thus, the possibility of application of production wastes to create new composite materials characterized by a certain complex of properties is confirmed.

SYNTHESIS AND CHARACTERIZATION OF PURE AMORPHOUS SILICON OXIDE FROM TREATED KAOLINITIC CLAY USING CHEMICAL EXTRACTION

Sunday Gbenga Borisade, Seun Samuel Owoeye, Aderonke Ayeni — Tue, 07 May 2024 00:00:00 +0000

Pure silicon oxide was produced in this study utilizing a sodium silicate solution made from Kankara clay as a precursor. The Kankara clay that was obtained from Nigeria was first beneficiated to produce pure dried powder clay. After that, the dried powdered clay was treated with heat activation and acid leaching, respectively. In a 500 mL Erlenmeyer flask, appropriate amounts of each clay (raw, thermally treated clay, and leached clay) were reacted with 3M NaOH solution. The flask was heated to 200°C and stirred continuously for 3 hours on a magnetic stirring hot plate connected to a reflux condenser. The solution was filtered to yield sodium silicate solution, which was then precipitated with 3M HCl while constantly stirring to produce a gelly-like white substance. The gel was aged for 18 hours, then washed with de-ionized water several times before being dried at 80°C for 12 hours to get pure white silica particles, which were subsequently described. The XRD analysis revealed that the silicon oxide synthesized is amorphous, but the microstructure evaluation revealed particles aggregation, which is usual in sol-gel synthesized powder.

PORT INJECTION OF DIESEL, BIODIESEL, AND PETROL IN A COMPRESSION IGNITION DIRECT INJECTION DIESEL ENGINE TO MITIGATE NITROGEN OXIDES AND SOOT EMISSIONS

Tue, 07 May 2024 00:00:00 +0000

The internal combustion engine is critical to modern society’s development. Spark ignition engine (SI) and compression ignition engine (CI) now use gasoline and diesel as their primary fuels. As a result of burning these fuels, significant amounts of pollutants are released into the atmosphere, resulting in environmental issues. Internal combustion (IC) engines are widely acknowledged as a significant source of environmental air pollution. The engine’s fuel oxidation process not only produces useful power, but also produces significant amounts of pollutant emissions such as carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxide (NOx ), and particulate matter (PM). When developing a new combustion process, consideration must be given to: lean homogeneous air-fuel mixture, increased compression ratio, and total and instantaneous combustion, all of which result in Port Injection Compression Ignition (PICI), that is a highly efficient and clean method of combustion. The goal of this research is to conduct an experimental investigation of PICI process of compression in a Premixed Charge Compression Ignition (PCCI) mode with Pilot Injection (PI) as the combustion activator. It was found that when compared to the conventional mode, the PICI mode produces cooler exhaust gas temperatures. Temperatures were lower in the PICI mode with biodiesel and petrol as secondary and primary fuels than in the PICI mode with other fuel combinations. In the PICI mode, the HC emission decreases at higher load with all fuels. In the biodiesel conventional mode, HC emission is minimum than in other modes. For all modes of operation, the specific fuel consumption has reduced with load. Diesel and gasoline have the lowest specific fuel consumption as primary and secondary fuels, respectively. Fuel usage in the PICI mode is lower than in the normal mode.

METHANE PRODUCTION FROM COW MANURE IN THE PRESENCE OF Bi(III) COMPLEX OF SULFAMIC ACID

Anelia Tzanova, Nikolay Kaloyanov, Kamelia Ruskova, Alexander Zahariev — Tue, 07 May 2024 00:00:00 +0000

The present study examines the process of biomethanization of cow manure in an anaerobic environment, in the presence of small amounts of Bi(III) complex of sulfamic acid. Since this complex has good antimicrobial activity, the purpose of adding the complex is to determine its effect on biogas and methane production. The reference samples (cow manure only) and mixtures of cow manure + 10 mg and cow manure + 20 mg of bismuth complex with a composition [Bi₆O₄(OH)₄](NH₂SO₃)₆ are subjected to biodegradation under the following conditions – duration of 33 days, nitrogen atmosphere and temperature of 34.5 ± 1°C. During the process, the volume of biogas and the percentage content of methane in biogas are measured in 2 - 3 days as well.
The analyses performed reveal that until the 10th day, the amount of biogas produced increases constantly and is comparable both for the control samples and for the mixtures. Further, until the end of the experiment, a significant and constant increase in the volume of biogas produced by the mixtures is observed compared to the control samples.
Regarding the percentage of methane produced by the reference samples and the mixtures, comparable relative amounts are found by the 7th day. From the 8th day to the 33rd day, the percentage of methane released by the mixtures is visibly greater than that by the reference samples.

SYNTHESIS OF COPOLYMERS FOR PROTECTIVE COATINGS

Vladimir Merkulov, Gulnara Ulyeva, Gulzhainat Akhmetova, Andrey Volokitin — Tue, 07 May 2024 00:00:00 +0000

Copolymers were obtained in this work and the methodology for their synthesis was worked out. Various fillers were selected for the polymer coating. Resulting copolymers have good adhesion required for composite protective coatings. An experiment was conducted to determine the corrosion resistance of metals coated with copolymers when exposed to aggressive environments, as well as to determine the hardness and thickness of the polymer coatings obtained. It was found that the polymer coating filled with bronze powder, despite the small thickness of 43.4 μm, has
the best adhesion and corrosion properties, as well as having the highest hardness values of 80.5 HB. Such physical and mechanical properties of polymer coatings allow them to be used as protective coatings for metal products working under the influence of aggressive media.

METHODOLOGY AND EQUIPMENT FOR RESEARCHING CORROSION CRACKING PROCESSES IN CASTING ALLOYS

Maria Krasteva — Tue, 07 May 2024 00:00:00 +0000

Corrosion cracking is the destruction of metal under static stresses and an aggressive environment. Corrosion fatigue is destruction of the metals and the alloys under the impact of cyclic mechanical pressure and aggressive environment simultaneously.
Stress corrosion is the least studied and systematized in terms of literature data on the impact of various aggressive environment (type, temperature, and concentration), composition and structure of the material, mode of heat treatment, method of obtaining and cleaning the casting, methodology for determination of corrosion under stress, as well as equipment for carrying out similar studies. The purpose of this paper is to present the methodology and equipment developed for corrosion cracking testing of cast alloys.

EXPLORING STRENGTHENING MECHANISMS OF ULTRAFINE-GRAINED Fe35Mn27Ni28Co5Cr5 HIGH-ENTROPY ALLOY PROCESSED BY SEVERE COLD ROLLING PROCESS

Tue, 07 May 2024 00:00:00 +0000

This study describes the strengthening mechanisms of an ultrafine-grained (UFG) Fe₃₅Mn₂₇Ni₂₈Co₅Cr₅ high-entropy alloy (HEA) processed by severe cold rolling (SCR) process at room temperature. Microstructural evaluations were performed by field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The findings demonstrated that the development of deformation microstructures consisted of a single face-centered cubic (FCC) phase with stretched grains along the rolling direction and lamellar deformation bands after a 90 % reduction in thickness. Using the Nix-Gao model, the dislocation density was determined by measuring the microhardness indentation size effect. The results indicated that an increase in rolling deformation leads to an increase in dislocation density. The dislocation density increased from 2.28 ×109 cm-2 for as-homogenized specimen to 8.65 ×109 cm-2 after 90 % reduction in thickness. The yield strength of the UFG Fe₃₅Mn₂₇Ni₂₈Co₅Cr₅ HEA was 5.2 times (1155 MPa) higher than that of the as-homogenized state (225 MPa). Finally, an assessment was conducted on the relative contributions of individual mechanisms, such as dislocation and grain refinement, to the strengthening of the Fe₃₅Mn₂₇Ni₂₈Co₅Cr₅ HEA.

COMPUTER SIMULATION OF PRELIMINARY HEAT TREATMENT AND RADIAL-SHEAR ROLLING OF BRASS

Tue, 07 May 2024 00:00:00 +0000

This paper presents the results of computer modeling of preliminary heat treatment and radial-shear rolling of L63 brass in the Deform program by cellular automata method. Quenching and annealing were simulated as pre-heat treatment modes. Radial-shear rolling consisted of three passes with a compression of 3 mm per pass. The variable parameters were the roll rotation speed (40 rpm, 70 rpm and 100 rpm) and the workpiece heating temperature before rolling (500°C and 700°C). It was found that the most effective mode of preliminary heat treatment of L63 brass is annealing at a temperature of 500°C. The most rational value of the heating temperature of the workpiece before rolling is 500°C, since in this case, at all selected speeds the recrystallization process does not start, which contributes to intensive grain grinding. An increase of roll rotation speed causes additional deformation heating, which contributes to recrystallization and a decrease of grain grinding intensity.

THERMOPHYSICAL PROPERTIES OF HYPOEUTECTIC, EUTECTIC AND HYPEREUTECTIC Al-Si AUTOMOTIVE ALLOYS UNDER AGEING TREATMENT

Tue, 07 May 2024 00:00:00 +0000

Influence of different levels of silicon under a variety of thermal treatment is investigated on the thermophysical behaviour of Al-Si-Cu-Mg automotive alloys. Conventional cast alloys are subjected to T6 heat treatment for age hardening. Hardness values, thermal conductivity along with microstructural observation under different heat-treated conditions are well thought-out to comprehend the ageing performance and the precipitation behaviour of the alloys. From these investigational results it is indicated that two successive hardening peaks take place in the aged
alloys. Ageing sequence consists of different phases like a supersaturated solid solution, GP zones, intermediate βʹʹ, intermetallic βʹ, equilibrium β and the Q phase but GP zones and the metastable phases are most likely responsible for these ageing peaks. Thermal conductivity decreases for these precipitates formation during ageing and increases for relieving the internal stress, dissolution of metastable phase and coarsening the precipitation of the alloys. Adding
up of Si to the alloy showed earlier ageing peaks with higher intensities intended for its increasing properties of heterogeneous nucleation and diffusion kinetics. After ageing around at 200°C for four hours the alloys offer the height hardness. Microstructural study reveals that eutectic silicon makes the grain boundary coarsen and beyond the eutectic composition the star-shaped blocky primary Si is formed. Subsequent to ageing at 350oC for one hour the alloys reach completely recrystallized state.

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ALUMINUM AND A356 ALLOY FOAMS CRYSTALLIZED IN A THIN-WALLED WATER-COOLED MOLD

Tue, 07 May 2024 00:00:00 +0000

Cylindrical foam castings of Al and A356 alloy were produced using a melt foaming method with the introduction of Ca and TiH2. Foam crystallization takes place in a cooled thin-walled metal mold. Samples cut off from the foam castings are investigated by X-ray tomography, quantitative data for porosity, average pores diameter and average cells wall thickness are obtained. It is found that the porosity is mainly open. Same samples are tested in quasi-static mode and the compressive strength is determined. The influence of porosity on compressive strength is analyzed.

STUDY OF STEELS FOR THE PURPOSE OF COMPARISON IN TERMS OF QUALITY INDICATORS AND ENERGY EFFECT OF THEIR PRODUCTION

Rositsa Gavrilova — Tue, 07 May 2024 00:00:00 +0000

The main purpose of this work is to examine ingots of steel grades 35HGSL, GS-34CrMo₄ and GS-42CrMo₄ and to obtain data on the microstructure and mechanical properties in the cast state and after heat treatment. Based on the results, it is necessary to evaluate the effectiveness of the heat treatment used and possibly prove its justification, since this type of additional treatment is usually recommended to improve the quality of materials, but it is not mandatory, as in the present case. The economic costs of the manufacturer for conducting heat treatment can be a good solution only in the case of achieved better performance indicators of the materials, and the energy efficiency of the applied processes is essential. For all these reasons, as a result of researches will be created databases, which will give the opportunity to definite opinion on the problem.

ENERGY AND POWER PARAMETERS OF ROLLING PROFILES FOR WHEEL RIMS WITH REDUCED METAL INTENSITY AND TAPERED SEATS

Valeriy Chigirinsky, Irina Volokitina — Tue, 07 May 2024 00:00:00 +0000

Analysis of experimental data on rolling asymmetric thin-walled sections with reduced metal consumption can be useful in identifying the features and prospects of application of profiles with reduced metal intensity, allowing obtaining significant economic and technological effects in production. The most mass-produced lightweight rim profiles 7.0-20-03 and 8.5-20-03 were studied to find the energy and power parameters. Rolling force, motor voltage current, revolutions and strip temperature were determined. The experimental data obtained indicate the possibility of mass production of high-performance rolled products for the automotive industry.

FREE UNDAMPED SPATIAL VIBRATIONS OF A ROBOT FOR PROCESS AUTOMATION IN METALLURGY

Valentin Slavov, Verjinia Aleksandrova — Tue, 07 May 2024 00:00:00 +0000

This paper presents the results of mechano-mathematical modeling of free undamped spatial vibrations of a robot for process automation in metallurgy.
A dynamic model of the robot is made. It is studied as a mechanical system with twelve degrees of freedom, contained by seven rigid bodies.
Kinetic and potential energy are derived symbolically by using the kinematics study results. The matrices characterizing the mass-inertial and elastic properties of the mechanical system are obtained. The differential equations that describe the free undamped vibrations are derived. They take into account the geometrical, mass, inertial and elastic characteristics of the mechanical system.
A compiled calculation algorithm is entered into a standard mathematical software product. Results are obtained in symbolic and graphical form. The natural frequencies and natural mode of a robot with concrete parameters are determined.
Results of the study of free undamped vibrations represent a basis for studying of the free damped and forced vibrations of a robot for process automation in metallurgy.

FEATURES OF THE FORMATION OF THE NANOSTRUCTURAL STATE OF THE SURFACE LAYER OF STEEL PARTS DURING PROCESSING AND OPERATION

Tue, 07 May 2024 00:00:00 +0000

Considered patterns of formation of the nanostructural state of the surface layer of machine parts during friction under conditions of complex dynamic loading. The results of the complex assessment of the state of the surface layer of samples after friction continuous indentation and scanning methods indenter, an analysis of changes in the work function of the electron from the surface of the samples. Shown that during the friction of steel surfaces, an increase in transverse slippage contributes to the formation of a more uniform surface layer. This decreases its strength, wear resistance, and a more uniform surface microgeometry. This is accompanied by a decrease in the magnitude and spread of the electron work function over the surface. The relationship between the nanostructural state of a polished surface and roughness and reflectivity is presented.

ELASTOHYDRODYNAMIC EFFECTS IN LUBRICATION OF JOURNAL BEARINGS UNDER TURBULENT CONDITIONS

Tue, 07 May 2024 00:00:00 +0000

The current paper is aimed to investigate the deformability effects of the bearing surface on the lubrication performance of cylindrical journal bearing with finite length under turbulent conditions. The bush is coated with a thin resilient layer with a smooth surface, the radial distortions of which are of the same order of magnitude as the film thickness. The elastohydrodynamic problem is studied under elasticity conditions in accordance with the plain strain hypothesis (Winkler model). The modified Reynolds equation is carried out on the base of the turbulent lubrication model of Hirs (bulk flow model). The partial differential equation is solved numerically by successive over-relaxation technique on a finite difference grid, considering different values of coating materials, lubricant viscosity, and journal speed. Results for the performance characteristics of the bearing are given for several selected values of Reynolds number and elasticity parameters of the soft liner on the bush.

MULTIMODAL SYSTEM FOR FACIAL EMOTION RECOGNITION BASED ON DEEP LEARNING

Atanas Atanassov, Dimitar Pilev, Fani Tomova — Tue, 07 May 2024 00:00:00 +0000

Emotions are one of the main ways of communication between people and of expressing attitudes towards objects, products, services, etc. They are divided to verbal and non-verbal classes. Human speech and intonation belong to the first class, and to the second (non-verbal) facial and body emotions, known as body language. The subject of this report is the development of multimodal deep learning system intended to recognize facial and body emotions and their relationship with the scene (weather) in which they occur. It is based on three deep learning neural networks (DNN) each one for recognition of facial emotion, body emotion and weather. Combining their results, we improve significantly the final facial emotion recognition (FER) results.

TOPOLOGY OF GALVANIC ISOLATED BATTERY CHARGING UNIT WITH POWER FACTOR CORRECTION

Yovko Rakanov — Tue, 07 May 2024 00:00:00 +0000

The present study investigates topology for battery charging units (BCU) with simple design and power factor correction. It has a galvanic isolation between the grid and the battery, which is one of the law and standard requirements. The impulse transformer ensures galvanic isolation, which makes the topology suitable for onboard electric vehicles (EV) charging units (OBC). The study also presents a simulation model a simulation model with the help of which a simulation is conducted and a result is obtained.