Journal of Chemical Technology and Metallurgy

A WAY TO IMMOBILIZATION OF ANTIMICROBIAL PEPTIDENISIN ON POLYDIMETHYLSILOXANE SURFACE

Todorka Vladkova, Peter Dineff, Dilyana Gospodinova — Fri, 11 Jul 2025 00:00:00 +0000

Medical devices associated infections due to microbial attachment and biofilm formation are with a high impact on human health and huge socioeconomic costs. Increasing resistance to traditional antibiotics and multidrug treatments are already recognized as one of the top-most serious threats to human health. This rises an argent need in the development of new antimicrobial agents, materials and strategies for improved protection of medical devices against infections. Immobilization of antimicrobial peptides onto the material surface is one of them. Many medical devices are fabricated by chemically inert polymers, like polydimethylsiloxane (PDMS), polystyrene, polyethylene, etc. to which surfaces is difficult the chemical bonding of biomolecules.

The aim of this investigation is to demonstrate the ability of plasma based Ar⁺ beam (PBAIB) to initiate antimicrobial peptides immobilization onto the chemically inert PDMS surface, using the bacteriocin nisin as an example. Earlier developed by us multi-step procedure was utilized that makes possible three types bonding of antimicrobial peptides: i) linker – free, at the first step, just after the PBAIB treatment; ii) via vinyl monomer linker, at the second step after grafting of vinyl monomer and; iii) via flexible spacer after coupling of di-NH₂PEG on vinyl monomer grafted surface. A parallel plate reactor, equipped with a serial capacitance, was employed to ensure arise of an ion flow inside the plasma volume, directed toward the treated sample. The changes in the chemical composition of the PDMS surface were studied at every step of the modification procedure and the successful immobilisation of nisin via flexible spacer (di-NH₂-PEG5000) was proved by XPS analysis.

This multi-step procedure to biofunctionalization of strong hydrophobic chemically inert polymer surfaces has a potential to be used whenever need arises to control antimicrobial activity of PDMS or other chemically inert polymeric materials and medical devices fabricated by them.

EFFECT OF STIRRING SPEED ON THE PREPARATION OF UREA-FORMALDEHYDE MICROCAPSULES FILLED WITH ROSE OIL BY INTERFACIAL IN SITU POLYMERIZATION METHOD

Stanislav Bayryamov, Maria P. Nikolova — Fri, 11 Jul 2025 00:00:00 +0000

In this paper, rose oil was microencapsulated by the chemical process of in situ interfacial polymerization using urea and formaldehyde as monomers serving as the capsule wall building material. As was found, in the process of microencapsulation by in situ polymerization, the emulsification step is one of the most important, which is why the authors pay special attention to it. Based on their preliminary studies, they divided this step into two sub-steps, considering the influence of reaction conditions separately in each one of them. The presented work examines the influence of stirring speed in the emulsification step (sub-step A and sub-step B), on the process efficiency, yield and quality of the obtained microcapsules, thus the authors hope to contribute to the optimization of the conditions for obtaining better quality microcapsules and with a higher yield.

STUDY OF DUNE SANDS OF YAZYAVAN FOR PRODUCING CERAMIC MATERIALS

ABDULAZIZ KHOKIMOV, Ashrap Eminov, Zulayho Kadirova, Saodat Mirsalimova — Fri, 11 Jul 2025 00:00:00 +0000

Results are provided for a comprehensive study of the dune sands of the Yazyavan of the Fergana region to prepare ceramic materials. The research investigates the chemical-mineralogical compositions and physical-chemical characteristics of the dune sands, focusing on their suitability for ceramic production. Various analytical techniques were employed to characterize these sands, including granulometric analysis and X-ray diffraction, to determine the mineralogical composition. The findings reveal that the dune sands possess unique properties that can enhance the quality of ceramic materials when used in combination with other raw materials and industrial wastes available in Uzbekistan. The study emphasizes the importance of optimizing the raw material mix to improve the performance and cost-effectiveness of ceramic products. Additionally, the results contribute to the understanding of local mineral resources and their potential applications in the ceramics industry, highlighting the need for further research to explore innovative ways to utilize these materials effectively. The overall goal is to promote sustainable practices in the production of ceramic goods, leveraging local resources while minimizing environmental impact.

STUDY ON ENCAPSULATION OF LAVENDER OIL ESSENCE IN ZEOLITE AND BENTONITE MATRICES

Janna Mateeva, Stoyan Djambazov, Albena Yoleva, Orhan Musa — Fri, 11 Jul 2025 00:00:00 +0000

In the present study, four matrices for encapsulation of essential oils were investigated: based on natural zeolite, based on alkali-activated bentonite, based on combination of 60 mass % alkali-activated bentonite and 40 mass % natural zeolite and based on 60 mass % alkali-activated bentonite and 40 mass % limestone. All natural raw materials are from deposits in the Eastern Rhodopes, Bulgaria. These matrices were loaded with lavender oil essence in amounts of 5 mass %, 15 mass % and 30 mass % respectively. The change in weight was monitored after the matrices loaded with lavender oil essence and had been exposed to air for a certain period of time at room temperature (for 1, 2, 7, 9, 14 and 60 days). Using XRD and FT-IR, the preservation of lavender oil essence in the matrices was established after 1, 2, 7, 9, 14 and 60 days of exposure to air at room temperature. It can be concluded that after the granulation into spherical particles with a size of 1 to 2.5 mm, alkaline-activated bentonite can be successfully used as a matrix alone or with the addition of other natural mineral raw materials such as zeolite and limestone for encapsulation of essential oils.

TECHNOLOGICAL SOLUTIONS OF USING SLUDGE FROM GROUNDWATER DEMANGANATION PROCESSES IN BUILDING MATERIALS

Inna Trus, Mariia Tverdokhlib, Vita Halysh — Fri, 11 Jul 2025 00:00:00 +0000

The development of solutions for the disposal of waste from water treatment is important from the point of view of reducing its accumulation. In this paper, manganese hydroxide from water demanganization is considered as a component of the cement mixture, which accelerates its hardening. A rational dose of manganese hydroxide sludge for the use in building mixtures is 0.5 - 4.0%. The research results showed that the desorption of manganese from cement in an aqueous medium is 0.003 - 0.035 mg/dm³ in 1 day and 0.005 - 0.041 mg/dm³ in 30 days. A technological scheme for the preparation of drinking water from an underground source containing an increased content of manganese and iron ions with subsequent processing of the formed sediments is proposed.

COMPARISON OF THE ADDITION OF TRIACETIN TO PETROLEUM AND WASTE PLASTIC FUELS

Fri, 11 Jul 2025 00:00:00 +0000

The increasing production capacity of biodiesel every year, the by product in the form of glycerol is increasing and causing the price of glycerol to fall. To increase its value, glycerol can be synthesized into triacetin which can be used as a fuel bio-additive. This study aims to determine the effect of triacetin on the quality of the fuel produced by the pyrolysis of plastic waste and RON 88 gasoline. The research method begins with the synthesis of triacetin from glycerol and acetic acid using Amberlyst 15 wet catalyst in a three-neck flask. The operating temperature was maintained at 100oC with a mixing speed of 290 rpm. Then the triacetin obtained were mixed with fuel from the plastic waste pyrolysis and RON 88 gasoline with a percentage variation of 0 % to 20 % v/v. The best effect was obtained by adding 20 % v/v of triacetin to each fuel. In the plastic waste pyrolysis fuel, the density and viscosity decreased by 0.0046 and 0.093, respectively, and increased calorific value by 160.87. While the RON 88 fuel can increase the mileage by 4.60 % on car engines and 11.11 % on motorcycle engines and can increase the octane number up to 89.

POTENTIAL PRODUCTION AND CHARACTERIZATION OF CHARCOAL-BASED BIO-BRIQUETTES FROM ULIN WOOD WASTE AS AN ALTERNATIVE SUSTAINABLE ENERGY RESOURCE

Fri, 11 Jul 2025 00:00:00 +0000

A biomass of Ulin wood waste in tropical countries has significant potential as the raw material used for an alternative sustainable energy resource. This is due to its high technical and economic value and environmental friendliness. This study aims to develop Ulin wood briquettes using tar extracted from Acacia bark as a binder to form solid cylindrical briquettes. The methodology includes the variation of the burning temperature (300-500°C), the burning time (3-5 hours) and the composition of the binder relative to the total mass of the briquettes (91-95%). The briquettes were analyzed in terms of yield, moisture content, ash content, volatile matter, fixed carbon, optimum conditions, and surface morphology. The briquettes were also tested for their suitability according to International standardincluding calorific value, relaxation density, drop test, and combustion rate. The results show that the best quality briquettes based on the mixture of Ulin charcoal and Ulin sawdust with tar binder were found with a variation of 91% Ulin charcoal and a burning time of 5 hours. The best quality variation of Ulin wood charcoal briquettes produced a calorific value of 7161.26 cal/g, a moisture content of 2.17%, an ash content of 2.46%, a volatile matter content of 15.19% and a fixed carbon content of 81.11%. The briquettes produced comply with the quality standards of the ASTM (American Society for Testing and Materials) standard D2395-2007a and SNI (Indonesia National Standard) 01-6235-2000.

HIGH-TEMPERATURE CARBOTHERMIC REDUCTION OF COAL BENEFICIATION WASTE

Vasil Metodiev — Fri, 11 Jul 2025 00:00:00 +0000

This study investigates the high-temperature carbothermic reduction of coal beneficiation waste (CBW) as a sustainable approach to resource recovery and waste valorization. Addressing the environmental burden of CBW accumulation, the inherent carbon content of the waste is utilized as a reductant to transform residual metal oxides into valuable metallurgical products. Experiments were conducted to evaluate the influence of temperature, holding time, reductant quantity, and additives on the reduction process.
Mathematical models describing the degree of carbothermic reduction and the reaction rate were developed. Results demonstrate the technical feasibility of carbothermic reduction for converting CBW into reusable materials, offering the dual benefits of waste mitigation and resource circularity. This approach aligns with circular economy principles, providing a scalable solution to minimize landfill disposal and promote sustainability within coal-dependent industries. The study highlights the potential for industrial implementation, emphasizing the economic and environmental advantages of metallurgical reprocessing of these mineral wastes.

GRREEN SYNTHESIS OF COBALT NANOPATRICLES BY USING ULTRASOUND WAVES ,WALNUT GREEN SKIN EXTRACT AS REDUCING AGENT AND EVALUATION OF PHOTOCATALYSTY ACTIVETY

Mohammad Hadi Meshkatalsadat, Rezaei, Tayebeh Momeni, Azizi — Fri, 11 Jul 2025 00:00:00 +0000

In this investigation, one-step synthesis of cobalt nanoparticles using aqueous extract of walnut green skin with the help of ultrasound waves and photo-catalytic activity as reducing agents was investigated and researched. After conducting preliminary tests and obtaining nanoparticles, The resulting particles were analysed using a scanning electron microscope (SEM) and the size of the particles was between 22 - 70 nm, then X-ray diffraction (XRD) analysis of the average size Cobalt crystals was shown to be 549 nm by Fourier transform infrared spectroscopy (FT-IR) of the sample was studied and the functional groups, OH, CH, C=C and CO, which indicated cobalt metal, were observed. After that, the photo-catalytic activity of cobalt particles on methylene blue was tested and studied, and the degree of its degradation was checked using ultraviolet-visible spectrometry (UV-Vis). SEM determines the structure of nanoparticles. Also in this study, ultrasound waves were used, and the sound waves hit the molecules of the extract and cause more vibrations. These vibrations cause the intrinsic activities of the molecule, because of which the formation of suitable bonds happens earlier and better.

EFFECT OF SILICA NANOPARTICLES ON WATER EVAPORATION PROCESS

Fri, 11 Jul 2025 00:00:00 +0000

This manuscript details an experimental study investigating the surface evaporation characteristics of a nanofluid composed of water and SiO2 nanoparticles with an average diameter of 16 nm. The study evaluated the evaporation rates of nanofluids with varying nanoparticle mass concentrations (0.05 %, 0.1 %, 0.2 %, 0.3 %, 0.4 %, 0.5 %, 1 %, 3%, 5 %) using a STA PT1600 thermal analyser at a temperature of 40°C. Results indicate that SiO2 nanoparticles initially reduce the evaporation rate of water up to a concentration of 0.1 mass %, but this effect reverses, with the evaporation rate increasing at intermediate concentrations (up to 0.5 mass%). At higher nanoparticle concentrations (1 mass % and above), the evaporation rate stabilizes and does not change significantly. These results demonstrate
that the evaporation properties of water can be modulated by adjusting the nanoparticle mass concentration up to 1 %.

MICROSTRUCTURE STUDY OF MIXTURES OF MICRO-POWDER Al AND NANO-POWDERS TiN, SiC AND Al2O3 PRODUSED BY TWO STAGE PROCESS

Fri, 11 Jul 2025 00:00:00 +0000

Composite wires obtained from aluminum shell, micron-sized aluminum powder and nanosized TiN, SiC and Al2O3 powders were fabricated by a two-stage process. The stages included ultrasonic treatment and hot extrusion. TEM and SEM observations were performed to investigate the wires’ microstructure. Individual nanopowder particles as well as particle agglomerations were observed by two microscopic methods, as well as nanoparticles distribution and localization in the matrix. It was found that the observed nanoparticles and clusters were located in the volume of micron-sized Al particles and along the grain boundaries of the matrix. The provided EDX analysis confirms the presence of nanoparticles in the aluminum matrix. From the obtained results, it can be concluded that the two-stage fabrication process of nanocomposite wires leads to better wetting of the nanopowders from the aluminum melt. Nanocomposites obtained by mixing and extruding TiN, SiC and Al2O3 nanopowders and Al micropowder can be used as modifiers of aluminum alloys, as the nanoparticles will contribute to grain refinement and will participate as additional crystallization centers.

FEATURES OF SHAPE CHANGE OF RING-SHAPED FORCE ELEMENTS MADE OF TiNi ALLOY AFTER ACTIVE DEFORMATION

Fri, 11 Jul 2025 00:00:00 +0000

The paper considers the features of shape change of ring-shaped force elements made of TiNi alloy during thermocycling. Non-monotonic deformation characteristics were obtained. The decrease in the sample shape during thermocycling is associated with incomplete martensitic transformation of the material due to temperature shifts during training. Holding of the sample in the martensitic state can lead to stabilization of the martensitic transformations’ temperatures and an increase in the proportion of martensite in the ring material. It can increase the shape change of the ring.

DETONATION SPRAYING OF AlCoCrFeNi2.1 EUTECTIC HIGH ENTROPY ALLOY COMPOSITE COATINGS REINFORCED BY Al2O3 PARTICLES

Fri, 11 Jul 2025 00:00:00 +0000

AlCoCrFeNi_2.1 eutectic high entropy alloy (HEA) composite coatings reinforced by Al₂O₃ particles were prepared by detonation spraying (DS) on low alloy steel substrates. The effect of annealing at different temperatures on the microstructure and mechanical properties of the coatings was further studied. The as-deposited AlCoCrFeNi_2.1-30 wt. % Al₂O₃composite coating exhibited a dual-phase FCC+BCC lamellar microstructure matrix with Al₂O₃ reinforcement particles. The crystalline structure and lamellar microstructure of the coatings highly retained after annealing at 500°C and 800°C, however, a partial dissolution of BCC was noted after annealing. Moreover, annealing improved inter-diffusion and annihilated pores, therefore highly compensated the decline in microhardness due to strain relief effect of annealing. The as-deposited composite exhibited a microhardness value of 415 HV, which slightly decreased to about 409 HV and 403 HV after annealing at 500°C and 800°C, respectively. The microhardness values demonstrated low fluctuation over the thickness of the coatings.

ORE ENRICHMENT WASTE AS RAW MATERIAL FOR HEAVY METAL SORBENTS

Arailym Kalymbet, Sholpan Kubekova, Silviya Lavrova — Fri, 11 Jul 2025 00:00:00 +0000

The study considered ore enrichment waste from the Ashiktas, Akbakai, and Maikain deposits to create sorbents based on silicophosphates. X-ray phase and electron probe elemental analysis were carried out, which confirmed the presence of silicon, aluminosilicate, and other valuable components suitable for the sorbents synthesis. The optimal synthesis temperature (600°C) contributes to the sorbents' porous structure development and a sorption capacity increase concerning Ni²⁺ ions, allowing them to be used to purify industrial wastewater from heavy metals, which was proven using zeta potential measurements and SEM images.

EVALUATION OF MECHANICAL PROPERTIES, WEAR AND HARDENING POTENTIALS OF CASSAVA LEAVES (MANIHOT SPP), FeCr, AND FeMo ON CASE HARDENED DUCTILE IRON

Sylvester Omole, Abdullahi Adebayo, Ekiomoadona Inegbedion — Fri, 11 Jul 2025 00:00:00 +0000

In this study, ductile iron was produced using lift out crucible furnace and was “packed” case hardened with simulated carbide from Ferrochromium (FeCr), Ferromolybdenum (FeMo) mixed with graphites, and grinded cassava leaves (Manihot Spp), by heating to temperature of 850^oC in the presence of snail shell as energizer, held for 2 hours in the muffle furnace and were quenched in SAE 20W-50 engine oil. They were tempered at 500^oC for 2 hours and allowed to cool in air to room temperature. Both the treated and untreated samples were characterized with metallurgical microscope. Wear and mechanical tests such as hardness, tensile and fracture toughness were carried out on treated and untreated samples. The microstructural features shows sample A treated with FeCr and graphite to have clusters of diffused carbides, that of B treated with FeMo and graphite showed finely dispersed carbide around the nodules and that of C was seen with diffused carbo-nitrided compounds or cyanide finely dispersed into the structure. Sample C treated with cassava leaves has the highest hardness value and lowest wear rate, followed by sample A treated with FeCr, then sample B treated with FeMo. Sample A has a slightly higher fracture toughness and UTS than sample C.

METAL FRACTURE IMAGE ANALYSIS FOR AUTOMATED STRENGTH MEASUREMENT BY THE VISCOSITY AREA SHARE

Vasilii Oskolkov, Egor Volkov, Olga Salnikova, Evgeny Ershov — Fri, 11 Jul 2025 00:00:00 +0000

The article proposes an approach to the automated detection of the viscosity area share in a metal fracture by means of using its image, which can be used in various lighting and does not require special personnel training. The viscosity area share is determined by means of using a set of segmentation neural networks, which includes the U-NET, which finds the objects under test in the image, which are metal fractures, and the Mask R-CNN, which finds the brittle fracture areas. Neural networks were trained on a dataset provided by the customer. Experimental verification of the proposed solution confirmed the possibility of automating the process of measuring the strength properties of the metal from fracture images with an accuracy of at least 85 %.

PRODUCTION OF BARIUM SULFATE WITH CONSIDERABLY IMPROVED WHITENESS THROUGH CALCINATION OF BARITE RECOVERED FROM WASTE MATERIAL

Ani Stoilova, Iliyan Mitov, Rositsa Gavrilova, Boyan Yordanov — Fri, 11 Jul 2025 00:00:00 +0000

The study presents calcination of barite recovered from the gangue stored in the tailings dam at a metallurgical plant in Bulgaria with the aim to product BaSO₄ with improved whiteness. The calcination was carried out in a rotary kiln at 1150⁰C under air. Samples from three batches of barite with different particle size, namely 40 µm, 20 µm and 6 µm, were processed and the color and brightness value of the product was measured. The residence time of the material in the kiln, respectively in the heated zone, was also determined. The results show that the brightness of the barite recovered from the gangue could be improved by 4 – 20 units through calcination.

DETERMINATION OF OPTIMAL GEOMETRIC AND TECHNOLOGICAL PARAMETERS OF SHEET METAL REINFORCEMENT STAMPING FOR A RUBBER-REINFORCED PRODUCT “BRAKE PAD” BASED ON COMPUTER MODELING

Fri, 11 Jul 2025 00:00:00 +0000

The article presents the results of finite element modeling of the sheet stamping process for obtaining metal fittings for a rubber-reinforced part "brake pad". DEFORM program considered obtaining a part by sequential cutting operations with punching and subsequent bending. In the process of computer modeling, the influence of various factors was studied: the type of separation operation, the gap between the die and the punch, the shape of the cutting punch, the use of lubricant, and other factors. The analysis of the results of computer modeling was carried out according to the level of deformation force. As a result, the most optimal parameters of the deformation process were identified: obtaining the initial workpiece for bending by cutting strips of strip metal; the gap between the punch and the die is 0.12 mm on each side during separation operations; the use of lubricants or punches with beveled edges; the gap between the punch and the die in the range of 4.4 - 4.5 mm on each side, taking into account thickness of the workpiece during U-shaped bending. Performing a bending operation at the second or third stage does not have a fundamental difference in evaluating the quality of the geometry of the parts being produced.