Studies of the extraction of impurities of calcium(II), magnesium(II), boron(III), and chloride ions from sulfate-chloride nickel solutions have been carried out. As extractants, we used di-2-ethylhexylphosphoric acid (D2EHPA), di-(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272), trialkylamine (TAA), tributyl phosphate (TBP), and aliphatic alcohols: octanol-1, 2-ethylhexanol, and a by-product of its production—distillation residue (TPRD). According to the results of research, it was established that a mixture of 40% TAA in 2-octanone and TPRD exhibits a high extraction ability with respect to boron(III); the degree of boron extraction is 60.7 and 74.5%, respectively. The effect of the acidity of the aqueous phase and the composition of organic mixtures on the extraction ability of organophosphorus acids D2EHPA and Cyanex272 in the extraction of calcium(II) and magnesium(II) was studied. The optimal concentration of individual extractants was found to be 20 vol % in Escaid 100 solvent and the composition of the mixture (vol %) 15 (D2EHPA) + 5 (Cyanex 272). Individual D2EHPA predominantly extracts calcium(II): extraction of 62% Ca(II) and 15% Mg(II). When using Cyanex272, the extraction of magnesium(II) predominates: extraction of 59% Mg(II) and 20% Ca(II). It is shown that the extraction mixture has higher performance than individual extractants for the extraction of Ca(II) and Mg(II) from nickel solutions in the range of pH 3.0–3.5, at which the coextraction of nickel(II) is negligible. With increasing pH values, the extraction of Ca(II) decreases owing to the increasing extraction of nickel and the displacement of calcium by it from the organic phase. The results of the extraction purification of the nickel electrolyte of JSC Kola MMC with an extraction mixture in the Ni form to exclude pH adjustment at each stage of the process are presented. The experimental data obtained make it possible to conclude that the extraction purification of nickel electrolytes of JSC Kola MMC is promising, as a result of which pure solutions of nickel sulfate with a residual content of ≤0.010 g/dm3 B(III), Ca(II), Mg(II), and chloride ions were obtained.
The quality of metal powder composition (MPC) made of heat resistant alloy EP648 (Ni–Cr–W–Mo) used for fabrication of parts by direct metal deposition (DMD technology) has been analyzed. It has been established that, regarding the main requirements (chemical composition, particle size distribution, purity, bulk density, yield, moisture content), the MPC meets the requirements of Technical Specifications TU 136-225-2019. The influence of the parameters of direct laser deposition (power of laser radiation, cladding speed) on the structure and microhardness of experimental specimens has been analyzed. The highest number of defects (multiple shrinkage cavities and incomplete fusion) is formed in the specimen fabricated at the power of laser radiation P = 1000 W and the cladding speed v = 40 mm/s. At the same time, the defects have the maximum dimensions. The minimum number of defects is observed in the specimens fabricated at P = 1400 and 1600 W and v = 45 and 38 mm/s. In this case, the most homogeneous structure of laser cladding is formed owing to complete fusion of powder particles and melt spreading. Nevertheless, the structure of the specimen deposited at P = 1600 W and v = 38 mm/s contains cracks located at the subgrain boundaries in the center of cladding tracks. Their formation is caused by overheating of the metal due to higher power of laser radiation and accumulation of high internal stresses after previously deposited layers. The microhardness of the specimens fabricated by all modes of direct laser deposition changes insignificantly in the range of 270–310 HV. On the basis of the obtained experimental results, it has been determined that the most optimum structure is formed in the specimen at the laser power of 1400 W and the cladding speed of 45 mm/s.
This review is devoted to known theoretical and experimental results in the field of using physical methods for processing melts in the preparation of metal matrix composite materials in conditions of casting and metallurgical technological processes. The possibilities, advantages, and disadvantages of various methods of physical influences are considered from the standpoint of their influence on the structural and morphological characteristics and physicomechanical and operational properties of cast composite materials based on aluminum and its alloys. A classification is presented and a detailed description of physical methods for processing melts when obtaining metal matrix composites is presented, depending on the state of the melt during the processing period (during melting, pouring, and crystallization) and according to the physical principle of imposed effects (thermal, electromagnetic, cavitation, mechanical, and others). The modern concepts of the laws and mechanisms of the influence of the processing of the melt by physical methods on the processes of structure and phase formation of metal matrix composites in the cast state are presented. From a qualitative and quantitative point of view, the currently known effects of exposure to the structure of composites are described, in particular, those associated with a change in the wettability of particles, their distribution, dispersion, and morphology, as well as with a change in the structural state of the matrix material. Data on the physicomechanical, operational, and technological properties of metal matrix composites obtained with the use of physical effects on the melt during melting and crystallization are systematized. The prospects for the development and practical application of methods of physical effects on melts in the production of metal matrix composites based on various matrix materials and reinforcement systems, including endogenously reinforced, exogenously reinforced, and complex-reinforced composite materials, are shown. Priority areas of theoretical research and experimental development are discussed; areas of discussion and issues in the field of obtaining metal matrix composites using physical effects on melts during melting and crystallization are revealed. On the basis of a systematic analysis of the key problems that limit the widespread industrial use of physical methods for processing melts, areas for future research in this direction are proposed.
The temperature dependences of the dynamic viscosity of molten lithium and beryllium fluorides, which are considered as candidate compositions for fuel and coolant of the molten salt reactor (MSR) burner of long-lived actinides from spent nuclear fuel of a VVER 1000/1200 (pressurized water reactor), were obtained by rotational viscometry using an FRS 1600 high-temperature rheometer (Anton Paar, Austria). Molten salt mixtures 0.66LiF–0.34BeF2 and (0.73LiF–0.27BeF2) + UF4 containing 1 and 2 mol % UF4 were studied with regard to the intermediate and fuel circuits of the MSR. The salt mixtures were prepared by direct melting of components and certified using X-ray phase and elemental analyses. The shear rate parameter was selected according to the viscosity curves obtained in the melts at a temperature of 700°C. It was found that the viscosity does not depend on the shear rate in the range of γ = 6–20 s–1. When measuring the temperature dependence of viscosity, the γ value was 11 s–1. The experimentally obtained values of the viscosity of the LiF–BeF2–UF4 melts in the temperature range from liquidus to 800°C are described by the linear equation log η = a + b/t, but their temperature coefficients differ noticeably, which indicates a significant dependence of the viscosity of these melts on composition and temperature. The obtained viscosity values for the 0.66LiF–0.34BeF2 melt agree with the available published data within 7–10% in the temperature range of 650–750°C. With an increase in the LiF content, the viscosity of the melt decreases: it is 20% lower in the 0.73LiF–0.27BeF2 melt at t = 650°C. However, when 2 mol % UF4 is added, the viscosity of the fuel salt 0.73LiF–0.27BeF2 + UF4 increases by 10% at the same temperature.
In Russia, most aluminum smelters are equipped with cells with self-baking anodes for which the task of reducing of anode paste consumption is relevant, since the fraction of anode materials in the cost of aluminum varies from 8 to 20%. To solve this problem, it is necessary to determine the need for anode paste. The method for calculating the specific anode paste consumption used at the enterprises of the aluminum industry has a large error. The article discusses the main errors of this technique, shows the stages of calculating the flow rate of the anode paste, assesses the adequacy of the calculations, and gives recommendations for improving the technique. In general, the considered methodology adequately reflects the processes of carbon consumption; however, the final result of the calculations may differ significantly from the real one. The values taken constant to simplify the calculation, in fact, can change during the electrolysis, which leads to a significant change in the final result of the calculations. For example, an increase in the fraction of CO2 from 0.45 to 0.5 leads to a decrease in the anode paste consumption by 15.3 kg/t Al. At the same time, it is known that, with the onset of the anode effect, the composition of the anode gases changes sharply: the fraction of CO2 decreases, and the fraction of CO increases. In summer, at high ambient temperatures, both the proportion of vaporized pitch and the proportion of anodes with an increased surface temperature rise. A change in the latter to 0.25 leads to an increase in anode paste consumption by 6.6 kg/t Al. The same applies to oxidation in air. The number of depressurized cells may increase, which will increase the carbon consumption. It is necessary to pay attention to the factors affecting the quality of the anode. Incorrectly selected particle size distribution or worn equipment can significantly degrade the quality of the anode and lead to an increase in carbon consumption. To correctly take into account the peculiarities of the formation of carbon monoxide, it is necessary to make adjustments to the calculation.
Although Ni-rich 60 NiTi shape memory alloy (SMA) shows superior properties, it is difficult to process due to its high hardness and studies on the manufacturing method are still needed. By the hot isostatic pressing process (HIP), parts close to the net shape are produced and the second operation may no longer be required. In this study, the effects of mechanical alloying on NiTi alloy produced by the HIP process were investigated. The starting powders of the first group were mechanically alloyed. The starting powders of the second group were mechanically mixed. Afterwards, the microstructures, transformation temperatures and some mechanical properties of these two groups were compared. For these examinations, SEM-EDS, XRD, DSC analyzes and microhardness measurement, density measurement by hydrostatic weighing method were performed. The result showed, mechanical alloying causes a more homogeneous microstructure and higher transformation temperatures.
Tungsten Inert Gas (TIG) welding was used successfully to weld 5 mm thick aluminum alloy plates AA5052-H32 utilizing as and 0.25 wt % Sc added ER 5356 filler rod in this study. Furthermore, the effect of adding Sc to the filler rod on TIG welded joints with mechanical and metallurgical properties was investigated. An optical microscope (OM) and a scanning electron microscope (SEM) were used to examine the microstructures of the joints The Al-Sc precipitates are distributed uniformly throughout the fusion zone of scandium added weldment. The welded joint with scandium added filler rod has fewer porosities, resulting in enhanced joint efficiency. Commercial filler rod welded joints had a coarse microstructure, but Sc modified filler rod welded junctions had a fine dendritic structure. The welded joints’ tensile characteristics and hardness were investigated. Compared to commercial filler rods, the weld junction created with scandium enhanced filler rod has twice the ductility. SEM fractography revealed brittle fractures in weld samples with commercial filler rods and ductile fractures in weld samples with scandium-added filler rods. With the addition of Sc to the filler rod, no appreciable hardness difference was observed in the fusion zone. This study paper will aid companies and researchers to better understand the metallurgical and mechanical behaviour of TIG-welded AA5052-H32 plates using scandium added filler rod, reducing the number of experimental trials and allowing for further research.
The results of studies on the use of ozone for the extraction of nonferrous, rare, and noble metals from ores, enrichment concentrates, and technogenic raw materials, identified from world scientific publications and in patent literature since the beginning of the 20th century, are summarized. Ozone is a strong oxidizing agent, the oxidation potential of which is 1.5 times higher than the potential of chlorine in an acidic environment. With the participation of ozone, even resistant metals and minerals are dissolved. The use of ozone for the extraction of metals from mineral raw materials is not accompanied by contamination of processed products and the formation of hazardous waste. A significant number of studies have been presented on the use of ozone to dissolve gold and other noble metals in mineral acids, showing an increase in the extraction of metals into solution. Cyanide and thiocarbamide leaching of gold from mineral raw materials by replacing oxygen with ozone have been studied. The results of vat and heap leaching of nonferrous and noble metals using ozone obtained by irradiation of air or oxygen with ultraviolet light, in particular, using photoelectrochemical treatment, are presented, on the basis of which new technologies are patented. An assessment of the effectiveness of ozone application for flotation enrichment of mineral raw materials, purification and detoxification of solutions and solid products of metallurgical processing, regeneration of other oxidizing agents, and extraction of metals from technological solutions is given. The results of studies on the use of ozone for vat leaching of metals from refractory sulfide ores and sulfide enrichment concentrates in acid solution, as well as the study of the kinetics of oxidation with the participation of ozone of sulfide minerals of copper, iron, zinc, and molybdenum, are summarized. The results of using a combination of ozone with other oxidizing agents—hydrogen peroxide and iron(III) ions—for the extraction of metals from sulfide mineral raw materials in a sulfuric acid solution are presented and analyzed. According to the results of most studies, it can be concluded that the use of ozone is effective for the extraction of metals from mineral raw materials: the technological parameters of the processes increase (extraction of metals into solution, selectivity of the extraction of metals from complex raw materials) and the duration of processing decreases.
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