• Lazer ablation in liquid as innovative method for preparation of ZnO-zeolite nanocomposites

    pg(s) 308-310

    Laser ablation in liquid is an eco-friendly and efficient method to produce nanomaterials with interesting properties in a laboratory scale. Previously reported ZnO nanoparticles, obtained by nanosecond and millisecond pulsed laser under various laser parameters, demonstrated photocatalytic, gas-sensing, and antibacterial activity. Here we explore the possibility for laser ablation of Zn metal plate in natural zeolite suspension and isolation of a composite ZnO-Zeo. It was characterized by UV-vis, XPS and SEM methods. The characteristic UV-vis peak for ZnO nanoparticles was observed at 340 nm, which is associated with small particles size, proven by SEM images to be 30-50 nm. The spherical ZnO particles are located on the zeolite surface. It was found that the attraction forces between both phases cause a shift in Zn 2p XPS peak positions which were determined at 1022.0 eV and 1045.1 eV for 2p3/2 and 2p1/2 levels, respectively. The approach for laser ablation in suspension could open avenue for simultaneous formation and incorporation of various nanoparticles into different supports.

  • Investgation properties of part – holder of breaking shoe beam made of SG60/SE300 steel cast

    pg(s) 304-307

    The main reason to perform this research investigation was to find a reason for appearing failures in exploratory condition of a part holder of breaking shoe beam. This part is incorporated in an assembly in railway wagon. This part together with few others was damaged in exploratory condition. It means that cracks were noticed on these parts. Some parts were completely broken. Because of that purchaser of parts complained of received parts to the producer. One of these parts was delivered to Prof Cvetkovski to find a reason and to give opinion about the reason for failure. The damaged parts are made of cast steel SG60/SE300. Many types of investigation was performed in order to solve this problem. As first visual control was done. After that, radiographic control was made. Investigations continued with determination of chemical composition and macro and micro metallography and determination of non-metallic inclusions. Finally mechanical testing like tensile testing, hardness measurement and impact toughness were performed too. Performed research confirmed that typical casting defects in the investigated part like the hot tears, slag inclusions, shrinkage porosity and segregation are the main reasons for failure of the delivered parts, holder of breaking shoes i.e. appearing of cracks or their completely fracture.

  • Frost resistance of hollow ceramic structural elements for ceramic beehives

    pg(s) 301-303

    In laboratory conditions, the frost resistance of hollow ceramic samples (constructive elements of ceramic beehives) was examined by applying a standardized methodology for assessing the reliability of ceramic products. For both sample types that were investigated (each with different phase compositions), the result for the frost resistance coefficient Kfr is above 84%. The products retain their structural integrity and high resistance in an extreme temperature environment. It was not observed any significant damage that could disrupt their functionality. The obtained results prove the assumptions that the ceramic beehives are appropriate for use in vast geographical regions characterized by critical temperatures and high diurnal and seasonal temperature amplitudes. At the same time, the experimental data can serve for further optimization of the recipe compositions, the technological regime, and for improvements of the construction characteristics of the ceramic elements that build the ceramic beehive.

  • Development of non-equilibrium thermodynamics models of solid-phase transformations in iron-carbon alloys

    pg(s) 275-277

    The development of metal physics and physical materials science in the coming decades is one of the main driving forces of the new scientific and technological revolution, which will cause significant changes in many sectors of industry and energy, construction and agriculture, military equipment and everyday life. In the work using the principles of nonequilibrium thermodynamics develop new models of solid-phase transformations in iron-carbon alloys: annealing, tempering, γ→α – transformation, graphite formation, carbides transformation. Developed models of solid-phase transformations applied to the management of the structure formation of iron-carbon alloys and optimization of their thermal treatment and identifying the conditions of formation of dispersed (nano) particles of carbides in some of the investigated alloys and possibilities of their transformation.

  • Nanocomposite materials based on industrial thermoplastics for metal-polymer systems with high resource

    pg(s) 272-274

    Methodological approaches to the creation of nanocomposite materials based on thermoplastic matrices of industrial production for metal-polymer systems with high resource are considered. The concept of energy and technological compliance of components is proposed. This concept allows to achieve a synergistic effect when introducing dispersed particles in the nanostate into the thermoplastic matrix due to the formation of a structure with special parameters of characteristics. Examples of practical use of the concept of energetic and technological compliance of components in the creation of nanocomposites for special structures are presented.

  • Use of an ultrasonic bath in the production of digestate extracts

    pg(s) 242-242

    This study examines the potential of digestate, a byproduct of anaerobic digestion, in organic farming and its environmental implications. The EU produces around 180 million tons of digestate annually, mainly from agricultural sources. Renewable energy policies have promoted the use of biogas digestate. Analyzed the organic carbon concentration in digestate extracts using ultrasonic bath methods with water and potassium hydroxide solution. The study highlights factors influencing organic carbon concentration, including raw material origin, extraction time, temperature, and solvent type.

  • High-nitrogen steel of responsible purpose for special engineering

    pg(s) 238-241

    Metallurgy under pressure is one of the main trends in the development of quality metallurgy. High-nitrogen steel of responsible purpose for special engineering was created and produced on the basis of metallurgy under pressure by the methods of special electrometallurgy. Comparative mechanical tests of high-nitrogen steel were carried out. The structure of the steel was analyzed by the methods of non-destructive testing. High nitrogen steel was found to meet the technical requirements. The structure is dense, without defects.

  • Tribological characteristics and structure formation of P6M5K5-TiC carbide steels for use in hybrid junctions of the metal-matrix composite-ceramic system

    pg(s) 235-237

    The article investigates the influence of the technological parameters of manufacturing and the effect of the initial charge on the structure and tribological properties of carbide steel when used in hybrid components of the metal-matrix composite-ceramic system. It was found that the titanium carbide content of the initial charge was the determining factor in the formation of the properties. At the same time, an increase in the titanium carbide content above 20 (wt. %) does not lead to a significant increase in the hardness of the composite, and in some cases even to a decrease in hardness. It is also worth noting that the use of sprayed high-speed steel powder to prepare the mixture allows the composite to be obtained with fewer technological transitions. According to the results of tribological studies, it was found that the lowest wear was observed when the ceramics were paired with a composite with a titanium carbide content of 10 and 30 (wt. %). At the same time, the results of the analysis of friction track profilometry and the size of the contact patch showed that as the content of the carbide component increases to 30 (wt. %), a change in the nature of the friction occurs, accompanied by intensive wear of the ceramic ball. In the ceramic-carbide-steel (10 wt. % TiC) friction pair, however, no wear of the ceramic ball was observed, and the cross-sectional shape of the friction track changed from spherical to flat.

  • A new approach to densification of titanium-based hard composites reinforced by TiВ

    pg(s) 212-214

    Titanium–titanium boride (Ti/TiB) metal matrix composites have been widely identified as promising materials for various applications. The traditional ingot metallurgy processing strategies used to fabricate these materials are energy intensive and have fallen short of their perceived mass production potentials. Powder metallurgy processing, especially that aimed at in-situ synthesis of Ti/TiB composites from titanium and TiB2 powder blends, is currently widely used for the cost-efficient production of such composites. Additional processing by the method of hot pressing improves the structure and mechanical properties of this class of materials.

  • Synthetic diamond grinding powders with increased abrasive ability for grinding tools

    pg(s) 210-211

    The results of a quantitative study of the influence of methods of chemical cleaning, pulse treatment with high-voltage electric discharges in a liquid, and flotation separation of synthetic diamond powder of the AS20 grade with a grain size of 100/80 on its abrasiveness are given. It has been established that the use of pulse treatment with high-voltage electric discharges in a liquid provides selective destruction of low-strength diamond particles, activation of the energy state of the surface, and an increase in abrasiveness. Changes in powder characteristics: homogeneity in strength by 1.3-1.9 times; decrease in the mass fraction of impurities by 2.8-7.8 times; guarantee an increase in abrasiveness up to 30-34% and contribute to the improvement of the physico-mechanical and physico-chemical characteristics of synthetic diamond powder

  • Thermodynamic properties of melts of binary and ternary systems containing Fe, Mn, Si or Ti

    pg(s) 207-209

    The thermodynamic properties of the melts of the Fe–Mn(Ti)–Si, Fe–Mn–Ti, and Mn–Si–Ti ternary systems at 1873 K were studied using the “geometric” and “analytical” Redlich-Kister-Mujian models from reliable analogous data for binary boundary subsystems. Special attention is paid to the precise thermodynamic properties of melts of the Fe-Mn, Fe-Si, and Mn-Si systems, with analysis of new data for the Si-Ti, Fe-Ti, and Mn-Ti systems. Very negative deviations from ideal solutions were established for the activities of the components in melts of the Fe-Mn-Si system. In the melts of the Fe–Mn(Ti)–Si, Fe–Mn–Ti, and Mn–Si–Ti ternary systems, the minimum mixing enthalpies are observed in binary melts, and in the Fe–Mn–Si system, the minimum occurs in the Fe0.4Mn0.2Si ternary melt 0.4, because the double Fe(Mn)– Si subsystems make the largest contribution to the interaction energy between different atoms. This study demonstrates the ability to predict the thermodynamic behavior of ternary systems, allowing for optimization of alloy compositions and improvement of industrial processes. Calculations based on the Redlich-Kister-Mujianu model with a triple contribution of -200 kJ/mol for melts of the Fe–Mn–Si system agree with experimental data, which confirms sufficiently high accuracy predicted parameters.

  • Protection of aluminum and aluminum alloys from corrosion

    pg(s) 180-182

    This paper examines corrosion protection techniques for aluminum alloys, focusing on traditional and innovative surface treatment methods. Aluminum alloys are applicable in many industries due to their advantages derived from the good combination of chemical, physical, and mechanical properties. However, they are susceptible to various forms of corrosion, which can critically compromise the structure of the component and lead to damage that does not ensure safe operation. Coatings are necessary for the durability and effective protection of aluminum and its alloys from corrosion, ensuring safe and long-term operation of components in aggressive environments.