Smelting Research Articles

Studies of the expansion mechanism on different pellets under hydrogen-rich reducing atmosphere

ABSTRACT In response to the need to develop green low-carbon iron smelting technology, blast furnace hydrogen reduction technology is of great significance for reducing CO2 emissions from the ironmaking system. This study focuses on the change in swelling behaviour of different types of pellets during the blast furnace hydrogen smelting process. It analyses the reduction swelling index (RSI/%) and compression strength before and after reduction at 900°C in a variety of reduction gas atmospheres, among other indices. The results show that under the condition of ore grade, the reduction expansion rate of pellet increases with the increase of grade. With the increase of basicity (R) (0 ∼ 0.25) and the Mg-Al ratio (M/A) (0.4 ∼ 1.4), the reduction in expansion of the pellet shows an upward trend. However, the RSI/% shows a downward trend with the increase of the synergistic effect of ore silicon and aluminium (S + A). The compression strength after reduction increases to different degrees with the increase of the proportion of hydrogen in the reduction atmosphere; the maximum increase was about 0.591 KN. SEM-EDS detection was carried out on pellet in different reduction atmospheres, and the structure and component changes of various regions during the reduction process were analysed.

Emission Characteristics and Health Risk Assessment of Volatile Organic Compounds in Key Industries: A Case Study in the Central Plains of China

Volatile organic compounds (VOCs), the precursors of ozone and fine particulate matter, are one of the atmospheric pollutants harmful to human health. The emission characteristics of VOCs in Anyang, a typical industrial city in the Central Plains of China, are unclear. To determine the emission level and composition of local VOCs, this study conducted on-site sampling of 20 factories in eight key industries. A total of 105 VOC species in seven categories were observed. The concentration of total VOCs emitted from the eight industries in order from large to small was as follows: packaging and printing > pharmaceutical > paint manufacturing > industrial coating > chemical industry > metal smelting > furniture manufacturing > textile printing and dyeing. In addition to industrial coating, the total VOCs and their corresponding ozone formation potential of organized emissions in seven industries (1.44–87.64, 1.52–181.61 mg/m3) were higher than those of unorganized emissions (0.38–24.17, 0.38–125.55 mg/m3). The VOC emissions were concentrated in the central, south-central, and south-eastern parts of the city, mainly from the factories in the packaging and printing, pharmaceutical, paint, and coating industries. The furniture manufacturing (4.55 × 10−3) and pharmaceutical (1.66 × 10−3) industries in organized emissions were at high risk of carcinogenesis, while the pharmaceutical industry in unorganized emissions (3.61 × 10−4) was at moderate risk of carcinogenesis. Naphthalene was the main high-risk compound. In terms of non-carcinogenic risk, the packaging and printing industry in organized emissions (228.51) and the metal smelting industry in unorganized emissions (16.16) had the highest risk, and the main high-risk compound was ethyl acetate.

Characteristics of Cd, As, and Pb Pollution in Farmland Soil and Edible Parts of Chili Pepper and Sweet Potato and Their Health Risk Assessment

To clarify the characteristics of Cd, As, and Pb concentrations in edible parts of crops and farmland soils, a key farmland survey was conducted on the field scale to investigate the characteristics of Cd, As, and Pb in soil and chili pepper （edible parts in the above-ground section） and sweet potato （edible parts under the ground） and assess the health risk of Cd-As-Pb in edible parts of chili pepper and sweet potato to humans in the typical co-contaminated agricultural soils by Cd, As, and Pb from metal smelting and sewage irrigation in North China. The results showed that the agricultural soil from chili pepper and sweet potato fields was co-contaminated by Cd and As at a moderate pollution level. The combined pollution index （2.82） of soil from sweet potato farmland was significantly higher than that from chili pepper fields （2.38） for sweet potato land much nearer to the pollution sources （P<0.05）. However, Cd concentrations in edible parts of chili pepper exceeded the safety limitation of 0.1 mg·kg-1 in the national standard of "Green food pepper products" （NY/T 1711-2020）, but the concentrations of Cd, As, and Pb in edible parts of sweet potato did not exceed the "National food safety standard food pollutant limit" （GB 2762-2022）. Additionally, the bioaccumulation factors （BAFs） of Cd, As, and Pb in edible parts of chili pepper to soil were markedly higher than those of sweet potatoes, especially for Cd, which showed the maximum of the BAFs for chili pepper. Therefore, BAFs could be the key factor in Cd accumulation in the fruits of chili peppers. The risk assessment of Cd and As as the carcinogenic elements in edible parts of chili pepper and sweet potato to human health demonstrated that Cd in the whole fruit of chili pepper had posed a significant health risk to adults （Ri>1×10-4）, and it was an acceptable level of health risk from Cd and As in edible parts of both crops to children. The non-carcinogenic element of Pb in the fruits of both crops did not cause health risks to adults or children. In summary, the chili pepper products from this co-contaminated farmland by Cd and As would pose risks to human health, and the sweet potato products would cause acceptable health risks to humans.

Urinary metabolic alterations associated with occupational exposure to metals and polycyclic aromatic hydrocarbons based on non-target metabolomics.

Long-term occupational exposure to metals and organics have been reported to be under great health risks. However, limited data are available on the molecular mechanism between combined exposure to metals and polycyclic aromatic hydrocarbons (PAHs) and harmful health effects. In present work, non-target metabolomics study was conducted based on urine samples from nonferrous metal smelting workers (n = 207), surrounding residents (n = 180), and the control residents (n = 187) by using ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS). Differential and correlation analyses among metabolic features indicate that total 22 differential metabolites in smelting workers were associated (p < 0.05) with metal and PAH exposure. Particularly, amino acid metabolism was strongly disturbed, and other metabolic pathways, including steroid hormone biosynthesis, citrate cycle, and pantothenate and coenzyme A (CoA) biosynthesis were also perturbed. Among them, steroid hormone biosynthesis was more affected by PAH exposure than metals, especially for hydroxyphenanthrene. These altered pathways were closely associated with oxidative stress, inflammation, and energy metabolism disorder. Additionally, our results indicate that endogenous metabolism in surrounding residents were also affected by nonferrous metal smelting activities to some extent. Our work provides valuable insights into molecular mechanisms of adverse health effects probably induced by combined exposure to metals and PAHs.

Distribution and Source-specific Ecological Risk Analysis of Soil Heavy Metals in South Hunan Province

To identify the spatial distribution patterns and assess the ecological risks associated with soil heavy metal pollution in the southern region of Hunan Province, a total of 362 surface soil samples were collected from the studied area. This study employed multivariate statistics and geographic information systems （GIS） to investigate the spatial distribution pattern of soil metals （Cd, Hg, As, Pb, Zn, Ni, Mn, Tl, and Sb）. Furthermore, the pollution sources and source-specific ecological risk of heavy metals were quantified by combining the positive matrix factorization （PMF） model and the comprehensive ecological risk index model. The results suggested that the mean concentration of soil metals in the study area exceeded the mean background values. Specifically, Cd, Hg, Pb, and Sb showed significant pollution levels and substantial spatial variability, with their concentrations reaching the background values by factors of 8.31, 9.12, 5.09, and 2.79, respectively. The spatial distribution of these heavy metals exhibited discernible patterns, with a higher concentration observed in western Chenzhou and a noticeable trend of increasing concentrations from the central region towards the periphery. The clusters with high concentrations of heavy metals were predominantly situated near industrial zones engaged in black metal smelting and processing and nonferrous metal mining and processing enterprises. Source apportionment indicated that the primary sources of soil heavy metals in the area were industrial activities associated with black metal mining and metallurgy （29.06%）, atmospheric deposition （22.05%）, nonferrous metal mining and processing （20.65%）, a combination of industrial and transportation sources （14.73%）, and natural sources （13.50%）. Moreover, the source-ecological risk assessment model specifically identified Cd and Hg as crucial elements requiring prioritized control measures to mitigate soil ecological risks. Industrial activities, including black metal smelting and processing and atmospheric deposition sources, were identified as the priority sources for health risks in the study region. These results provide an important theoretical basis for the development of effective strategies aimed at managing and diminishing the risks associated with heavy metal contamination in the southern region of Hunan Province.

Investigations of liquid-liquid transitions in metallic melts by fast differential scanning calorimetry

Investigations of liquid-liquid transitions in metallic melts by fast differential scanning calorimetry

Modeling regional private income and its embedded carbon emissions: sources, flows and inequalities.

Composing regional total income jointly with government income, private income represents levels of development and affluence from the household perspective. Considering the need for fair carbon emission reduction responsibility distributions among regions with divergent income levels, private income-embedded emission (PIEE) and the inter-regional inequalities remain to be explored. Combining input-output analysis and the Gini coefficient, this study traces the sources and disposals of regional private income in China, as well as their embedded carbon emission flow, and quantifies the distribution and inequality of PIEE across industrial sectors and provincial regions. Results indicate that the sectors of power and heat, smelting and pressing of metals, and manufacture of non-metallic mineral products contribute the most to PIEE. Hebei and Inner Mongolia have larger PIEE, while emissions embedded in private income disposals are primarily driven by consumption of products from agriculture, light industry, and services. Regions clustering at the beginning (Beijing, Shanghai, Tianjin) of the C-Lorenz curve of PIEE account for 19.3% of private income, while 8.2% in PIEE, with the percentages for those clustering at the end (Inner Mongolia, Ningxia, Xinjiang) as 10.0% and 28.5%. The findings provide insights into strategizing emission reduction along the entire value flow and coordinating carbon emissions, income and emission reduction responsibility.

Enhanced two-temperature model and its application in comprehensive analysis of femtosecond laser melting of gold, copper and their alloys.

Extensive research on ultrashort laser-induced melting of noble metals like Au, Ag and Cu is available. However, studies on laser energy deposition and thermal damage of their alloys, which are currently attracting interest for energy harvesting and storage devices, are limited. This study investigates the melting damage threshold (DT) of three intermetallic alloys of Au and Cu (Au3Cu, AuCu and AuCu3) subjected to single-pulse femtosecond laser irradiation, comparing them with their constituent metals. This is accomplished by extending an earlier-developed two-temperature model (TTM)-based code with several improvements, including precise modeling of temperature-dependent optical properties and ballistic electron transport. The dynamic optical model inclusive of ballistic effects is demonstrated to reproduce the experimental DT of pure metals with minimal variation and is therefore adopted for further investigation. Our simulations reveal that the alloy films have significantly lower incipient and complete melting thresholds compared to the pure metals due to their low thermal conductivity and high electron-phonon coupling strength. Theoretical studies on varying the thickness of metal and alloy films unveil the usual trend of a rapid increase in DT up to a certain thickness, followed by a saturation region. This universal DT profile is elucidated by proposing a first-of-its-kind analytical function. Excellent agreement between the coefficients of the function with optical and electron diffusion parameters derived from the comprehensive theory proposed here reinforces the robustness of the model. The novelty of this study also lies in introducing the concept of a critical film thickness for which the entire film attains the melting temperature at its complete melting threshold.

Зв'язок хімічної мікронеоднорідності сірого чавуну та структури пластинчатого графіту

The relationship between chemical microheterogeneity of gray cast iron castings, revealed by the method of color etching in sodium picrate, and the structure of flake graphite was studied. The results of microstructural studies indicate that the crystallization of gray cast iron is accompanied by the emergence of several levels of chemical and structural microheterogeneities of the crystallizing melt, affecting the formation of graphite. Microstructural features indicate that the cast iron melt, which is close in carbon content to the eutectic composition, acquires a dendritic and cellular structure before the formation of graphite. The intensity of chemical microheterogeneity and its topology are hereditarily related to the location, size and shape of graphite inclusions. Flake graphite formed inside and on the periphery of melt cells has different structure and thickness of plates. The enrichment of areas of cast iron melt with silicon leads to the formation of dendrites of primary austenite and primary graphite of the largest size in them. The microhardness of ferrite in the dendrites of former primary austenite is approximately 1.5 times greater than the microhardness of ferrite in areas adjacent to inclusions of primary graphite. A close inverse correlation (r = –0.93) was established between the microhardness of ferrite in areas with different liquation intensities and the thickness of graphite flakes located in these areas. The greatest spread of microhardness values and width of graphite flakes is observed in the most liquated areas enriched with silicon in the center of the cells, corresponding to the location of eutectic colonies. In the spaces between the cells, graphite is observed with the smallest thickness of the flakes, which are located at the smallest distance from each other. It is necessary to continue research into the hereditary influence of the structure and physical and chemical properties of high-carbon iron melts on the mechanism of graphite formation and the features of its structure in cast irons.

Prevalence and Risk Factors of Lower Extremity Musculoskeletal Disorders Among Occupational Groups in Key Industries - China, 2018-2023.

Lower extremity musculoskeletal diseases (LE-MSDs) have emerged as a significant contributor to the global disease economic burden and worker absenteeism, becoming a global public health concern. However, the epidemic characteristics of LE-MSDs among occupational populations in China are unknown. This report finds that the LE-MSDs prevalence rate among key occupational groups in China is 17.7%, with the top 5 being toy manufacturing, medical personnel, automobile manufacturing, nonferrous metal smelting and rolling processing, and coal mining and washing. This study investigated the occurrence of LE-MSDs in key industries in China and its possible risk factors to provide big data support for preventing and controlling such diseases in these industries.

MULTILEVEL INVERTER TO GENERATE VOLTAGE WITH COMPLEX HARMONIC COMPOSITION

The paper deals with the problem of forming the desired and controllable harmonic composition of the output curve of a multilevel voltage inverter. The problem is relevant when creating installations for multi-frequency induction heating and metal melting. The purpose of the study is to develop an effective method to form the output voltage of power sources for multi-frequency induction heating installations, the curve of which has a given harmonic spectrum. Materials and methods. The theoretical part of the work was carried out on the basis of the circuit base of multi-level voltage inverters and switching DC converters using numerical analytical methods of studying nonlinear electrical circuits, methods of solving nonlinear differential equations and approximate harmonic analysis, as well as simulation modeling methods using the MATLAB/Simulink mathematical package. Experimental verification of the theoretical results was carried out in laboratory conditions on the example of a multi-level inverter generating a voltage curve with three operating harmonics. ACS758 series sensors and a four-channel RIGOL DS1104Z digital oscilloscope were used to record the results. Research results. Achieving of the purpose is based on the use of a universal multilevel voltage inverter, the circuit scheme of which does not depend on the levels number of the generated curve, which ensures a minimum number of power elements for any complexity of the curve spectrum. The method of forming of the output curve of this inverter consists in alternately connecting of the output capacitors of two direct voltage impulse converters to the input of a single-phase bridge voltage inverter using a transistor switch. In this case, voltages of different parity levels are formed by capacitors in the order of their succession, as a result of which a constant-sign multilevel voltage is formed on the input of the bridge inverter, corresponding to the required alternating-sign multilevel voltage. The law of the transistor switching of the bridge inverter ensures the conversion of its input voltage into a load voltage with a given harmonic composition. The peculiarity of the developed converter control method is that the transistor switching of the bridge inverter is carried out in accordance with the change in the sign of the generated curve. The method contains an algorithm to determine levels values formed by capacitors of impulse converters that realizes the required spectrum of the inverter output curve. The efficiency of the proposed method is illustrated by computer modeling of the converter when voltage with four working harmonics of the spectrum (i.e. the required spectrum harmonics) is generated. The quality indicators of the realized spectrum of the voltage curve are proposed and the analysis results of the influence of the levels number on values of these indicators are presented. The efficiency of the proposed methods is demonstrated experimentally with a laboratory model of the converter. Conclusions. The paper proposes a method to form the output voltage of a power source, the curve of which has a given harmonic, the efficiency of which is confirmed by the results of computer modeling and laboratory experiments. The proposed technical solutions made it possible to generate an output voltage, the spectrum of the curve of which contains four or more harmonics with specified amplitudes with a minimum number of power elements of the circuit. The paper also proposes models of quality indicators of the realized spectrum of the voltage curve and presents the results of the analysis of the influence of the number of levels on the values of these indicators. The developed methodology allows the development in the direction of controlling the spectrum of the generated voltage in real time, as well as non-periodic alternating voltage that changes according to a given program in accordance with the requirements of the technological process.

Investigation of the problems of existing methods of electric contact welding of rails and local heat treatment of welded joints

The article presents a statistical analysis of the operational cycle of welded joints of domestic and imported rails on all Russian Railways (JSC Russian Railways), which indicate insufficient reliability of welded joints. Statistical data on defective rails en route of JSC Russian Railways are presented as of 01.01.2022, 01.01.2023 and 01.01.2024. During contact welding of rails, parts of the welded rails are in two states: at the weld site, the metal is heated to a temperature exceeding the melting point of 1520 °C, where the metal melts and the metal is ejected from the weld, and in a plastic state in the HAZ. The ends of the rails are heated to temperatures below the solidus (for steel up to 1100–1200 °C), and under the action of a compressive force, they are plastically deformed by a certain amount (subsidence) and welded. The amount of upsetting, the compressive force, and the heating temperature of the rails have a decisive effect on the formation of the welded joint and are the main factors in the process of contact welding. Insufficient fatigue strength of welded joints has become increasingly evident when welding rails using the pulsed flashing method in steels alloyed with chromium and silicon. The high cooling rate of the HAZ leads to the formation of martensite areas that act as stress concentrators and subsequently to the possible formation of defects in welded joints, i.e. to the development of fatigue cracks in the foot, neck and head of the rail with subsequent brittle fracture. If the hardening technology is violated, the metal of the head of the welded joint spalls, and the softening of the metal during welding leads to the crushing of the metal of the head of the welded joint. Welded joints in rail strings must not have internal and external defects of a certain type that exceed the standard dimensions. As the speed of movement increases, the requirements for the straightness of the rails and welded joints increase.

Magnetic properties of quenched binary and ternary quasicrystal approximants

The magnetic properties of binary Gd-Cd and ternary Gd-Au-Ge crystals obtained from the newly introduced low-melt peritectic formation (LMPF) synthesis method were investigated. This method consists of a rapid quenching of the metallic melt followed by an annealing treatment at a relevant temperature. In the first system, both quasicrystal (QC) and approximant crystal (AC) phases can be stabilized, whereas only the AC phase is obtainable in the pseudo-binary Gd-(Au-Ge) system. The magnetic properties of the crystals obtained from LMPF for each system are compared to those of larger single grain crystals obtained from the self-flux (SF) method.

Solubility of rare earth oxides in chloride, chloride-fluoride and fluoride melts of alkali and alkaline earth metals

This paper presents a review of data on the solubility of rare earth oxides in halide melts of alkali and alkaline earth metals. The highest solubility of rare earth oxides is observed in fluoride melts, the lowest – in chloride melts. There are very few works devoted to the study of the solubility of rare earth oxides in mixed chloride-fluoride melts. The solubility of rare earth oxides decreases in the series La-Ce-Pr-Nd-Gd. The greatest number of works are devoted to the study of the solubility of neodymium, lanthanum and cerium oxides. There are practically no data on the solubility of “heavy” rare earth oxides (from Tb to Lu) in halide melts.

Physical and technological features of mechanoactivation of powder particles formed during hydro-vacuum dispersion of metallic melts

A study has been conducted on the hydro-vacuum dispersion process of metal melts using gray cast iron SCh20 (in Russian nomencluture; 3.3–3.5C, 1.4–2.4Si, 0.7–1Mn, 0.15S, 0.2P in wt %)—an analogue of GG20. It has been revealed that the main factor conditioning the mechanoactivation of formed particles is their solidification in a fibrous non-equilibrium structural-tensioned state. This state is achieved by flattening and asymmetric twistedness of droplets that are detached from the liquid metal in the disperser under volumetric impact of shock-pulsating waves of hydraulic discharge. The degree of particle activation was found to depend exponentially on their dispersion and specific surface area. These parameters determine the degree of asymmetry of shear deformations and the amount of accumulated energy. In turn, the size dispersion and specific surface are significantly influenced by physical and technological factors such as the specific flow rate and pressure of injected water, the thickness and the elevation angle of the hydro shell of the vacuum diffusion funnel, the diameter of the dispersed melt jet passed through it, and its superheating temperature. The control of these parameters makes it possible to smoothly adjust the key ratio “liquid metal: water” and set up the dispersion process with the highest possible degree of size dispersion and activation of the resulting powder.

Activation and development of direct plasma spark sintering and this method after the synthesis of combustion of ceramic-metal compositions through different mixtures of metal melts and/or intermetallic compounds

The article shows the effect of different mixtures melts of metals and/or intermetallic compounds with various oxide, non-oxide additives, obtained solid solutions of metallic phases during spark plasma sintering, spark plasma sintering after combustion synthesis on the phase composition, micrstructure, grains sizes of crystalline phases, relative density, linear shrinkage, microstructural featres of boundary layers, paths of microcracks, physical-mechanical properties, values of standart erors of properties of samples. Synthesized powders of h-BN, B4C, NiTi, NiZr are characterisized by high intensity of crystallization of h-BN, B4C, NiTi, NiZr. Sintered by spark plasma method c-ZrO2, c-BC2N at pressing loadings 35 MPa and 1400 oC, 5 GPa and 2327 oC in boron melt show evoluted crystalli-zation of c-ZrO2, с-BC2N phases, respectively, crystalline, uniform and dense microstructures. Obtained by combustion synthesis powder shows multi-phase composition with various crystallization of phases. Sintered by direct spark plasma method samples show evoluted mullitization, crystallization of c-ZrO2, solid solutions of metallic phases, but in the samples, obtained by spark plasma method in different sintering conditions after combustion synthesis are visible crystalline, multi-intensive phases. The samples show crystalline, multi-uniform and multi-dense microstructures, variously dispersed grains of crystalline phases. Sintered samples are differ by the relative density, linear shrikage, density, uniformity, width, path of boundary layers and propagating microcracks across these boundary layers, the resistance to the cracking, values of physical-mechanical properties, values of standart errors of properties of samples.

Improved Surface Quality and Microstructure Regulation in High Power Fiber Laser Cutting of Stainless Steel Grid Plates.

In order to disintegrate nuclear fuel rods in the grid connection structure, a 10 kW fiber laser was used to cut a stainless steel simulation component with four layers of 3 mm thick plates and 12 mm gaps. The slit width is regarded as an important indicator to evaluate the cutting quality of the four-layer stainless steel plate. The results showed that good laser cutting quality can be successfully achieved under the proper process parameters. The widths of the cut seams of the four layers of grating after cutting were 1.25, 1.65, 1.80, and 1.92 mm. As the auxiliary gas pressure decreased layer by layer, the metal melting pool for the first two plates was mainly destroyed by the auxiliary gas. The cutting quality was good, and the slit area was mainly austenite with the presence of some ferrite. The third- and fourth-layer plates almost had no gas flow to assist blowing off, so the cut surface was an uneven melting pit, the cutting quality was poor, and the cut seam area ferrite content was higher than the upper plate cut seam area. At the same time, due to the lack of airflow cooling of the bottom plate, high laser energy, and long heating time, grain coarsening occurred, while grain deformation and a large number of dislocations existed. It can provide process support and technical guidance for the disintegration of nuclear fuel rods.

Вивчення змочування SnO2—In2O3-кераміки розплавами срібло—мідь

To improve the wetting of oxide ceramic with metals in addition to traditional dopands (Ti, Zr, Nb, etc.), which have a high chemical affinity to solid phase atoms, alternative active additions can also be used. In particular, it relates to non-metallic electronegative elements VIa—VIIa groups of the periodic system (O, S, Se, F, Cl, Br), which have a high affinity to electron. Such additives are able to reduce free surface energy at the liquid/gas and liquid/solid interfaces and in such a way improve the wetting. The SnO2—In2O3 system is the most optimal material for the layers of the so-called TCO (Transparent Conductive Oxide). Since the cost of metal indium and its compounds continues to grow and new technologies are actively developing, there is a need to find alternative TCO that would have less In2O3 content. That is why systems containing SnO2, doped by relatively small amounts of In2O3 were explored. Ag—Cu based fillers is often used to joint oxide materials. In this case, there is a significant effect of the additives of the third component on the activity of oxygen in liquid metal, which causes an increase in oxygen content directly in the melt. Specially synthesized high-dense ceramics based on SnO2, which was received by adding 5, 10, 20 or 40% (mass.) of In2O3 with subsequent sintering, were used for wetting experiments. The experimental data indicate that in vacuum and air copper, added to the silver melt, significantly improves wetting on all types of the studied ceramic substrates, as well as the wetting is improved with increasing of the In2O3 content in the substrate. A dense transition layer of about 10 μm, which contains a large amount of copper, is formed on the interfacial border. A similar phenomenon was observed at the inter-phase boundary of other oxide materials. The improvement of wetting is explained by an increase in the solubility of oxygen in the melt, which acts as an adhesive-active element, with the addition of copper and increased electronegativity of the substrate with increasing content of In2O3. Keywords: tin dioxide, indium oxide, semiconductor, wetting, contact interaction, metal melt.

Оксид галію — перспективний мультифункціональний матеріал четвертого покоління (огляд)

This work is devoted to the analysis and systematization of the main information on the properties of gallium oxide and materials based on it and their practical application, as well as the prospects for further research of the specified actual oxide material. A review of literature data concerns general properties and structure of gallium oxide Ga2O3, various methods to produce Ga2O3 thin films, nanostructures, bulk crystals, powders, the application of gallium oxide in various fields of science and technology, including semiconductor field, electronic engineering, optoelectronics, the creation of composite transparent materials, etc. In the last thirty years or so, thanks to the progress in growing large-volume, high-quality gallium oxide crystals, this material with an ultra-wide band gap and a high critical breakdown field has gained significant application in the manufacture of the latest power electronics and high-voltage electronic devices. Important experimental studies, in particular, in terms of developing methods of metallization, joining similar materials, connecting electrical contacts, for example, by soldering, require the study of the wetting of these oxide materials by metal melts and the contact interaction at the interphase boundaries. Data on surface phenomena, in particular the wetting of gallium oxide by metals, are practically absent in the literature, and this requires further additional research. Keywords: gallium oxide, physical properties, semiconductor, power electronics, optoelectronics, transparent composite materials.

Formation of B2 Phase and its Phase Stability in Equiatomic Al-Cu-Fe-Ni-Ti High Entropy Alloy

In the present investigation, we have synthesized a single-phase high-entropy alloy in Al-Cu-Fe-Ni-Ti system by melting of the individual metals using a radiofrequency induction furnace under an argon environment. The as-synthesized alloy shows the formation of a B2-type ordered phase with a lattice parameter of 0.289nm. The mechanical stability of this single phase high-entropy alloy was investigated under high-energy ball milling. The milling was performed at a speed of 400rpm for 10, 20, and 40h under a hexane medium with a ball-to-powder ratio of 40:1. The formation of nano crystallites (~ 10nm sizes) body centered cubic (BCC) phase (disordered B2) has been observed after 40h of ball milling, which has been confirmed by X-ray diffraction and transmission electron microscopic investigation. The equiatomic Al-Cu-Fe-Ni-Ti high entropy alloy structure is observed to be quite stable during mechanical milling up to 40h; only grain refinements and lattice strain accumulation were observed with milling time.