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Vacuum-arc Nitriding of Carbon Steels Having Low Tempering Temperature
Viacheslav Stolbovyi,
Anatoliy Andreev,
Iryna Serdiuk,
Igor Kolodii,
Anatoliy Shepelev
Issue:
Volume 10, Issue 4, December 2021
Pages:
48-54
Received:
2 September 2021
Accepted:
28 September 2021
Published:
29 October 2021
Abstract: Studies have been made into a new possibility of modifying the surface of steels having a low tempering temperature by nitriding them in a vacuum-arc gas discharge followed by heat treatment (heating, quenching and tempering). Generally, nitriding of hardened steels takes place at a temperature of about 500°C, and thus this process appears impossible for steels with tempering temperatures of the order of 200... 300°C. It is demonstrated here that a single ion-plasma nitriding of high-carbon steel with the composition of 0.9% C, 1% Cr, 1% Si, followed by heat treatment, provides the nitrided layer of 2.5 mm in depth, with the hardness between 9 and 11 GPa. Within the range of X-rays penetration, the nitride-hardened layer of the surface is defined as the nitrogen austenite-alpha ferrite mixture, which shows high wear resistance and impact toughness. This layer contributes, in particular, to three-/four-foldin crease in the operational life of cutting punches (made of this steel and used in the manufacture of metal sieves) as opposed to the punches that have undergone conventional heat treatment. After repeated nitriding of the same steel and its subsequent heat treatment according to standard technologies the nitrided layer thickness becomes nearly twice as large, and that allows for multiple regrinding of steel tools. A computer analysis of related publications entered into three International Databases (INIS, MSCI, SCOPUS) has been carried out.
Abstract: Studies have been made into a new possibility of modifying the surface of steels having a low tempering temperature by nitriding them in a vacuum-arc gas discharge followed by heat treatment (heating, quenching and tempering). Generally, nitriding of hardened steels takes place at a temperature of about 500°C, and thus this process appears impossib...
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Thermal Waters Circulation During the Formation of Ore Deposits
Ivan Vadimovich Gordienko,
Vadim Vyacheslavovich Gordienko
Issue:
Volume 10, Issue 4, December 2021
Pages:
55-66
Received:
28 September 2021
Accepted:
14 October 2021
Published:
29 October 2021
Abstract: The paper analyzes processes leading to the formation of gold-bearing sulphide deposits. The study was based on the data available for the territory of Ukraine and other regions. The deposits in question are shown to be associated with post-geosynclinal activation as postulated by concepts of the advection-polymorphism hypothesis. The nature of ore-bearing fluids is analyzed. Even on the ocean bottom helium isotopy points to the presence of mantle components in the fluid. Metamorphogenic and magmatic fluids are obviously involved in the process. An abnormally fast growth of permeability in fault zones during the activation period is shown to have contributed to the formation of deposits. The existence of metalliferous and barren phases of hydrothermal activity is explained. Thermal models of deposits are constructed and diagnostic criteria for their identification determined. The main features of the deposits are associated with faults through which mineralized deep waters circulate. In young deposits, these are: 1. Increased content of metals in soil and plants. 2. Intense heat flow anomalies. 3. High helium isotope ratios, indicating an active process in the Earth's mantle. 4. Zones of high electrical conductivity in the crust and upper mantle. 5. Near the faults, positive anomalies of the gravity field are formed, associated with the transformation of rocks under the influence of heating. The search for gold-bearing sulphide deposits should be continued, considering that the reserves already explored in Ukraine guarantee commercially viable production of over 10 tons of gold per year.
Abstract: The paper analyzes processes leading to the formation of gold-bearing sulphide deposits. The study was based on the data available for the territory of Ukraine and other regions. The deposits in question are shown to be associated with post-geosynclinal activation as postulated by concepts of the advection-polymorphism hypothesis. The nature of ore...
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Microstructure and Mineralogy of Compressed Earth Bricks Incorporating Shea Butter Wastes Stabilized with Cement
Alfred Niamien Kouamé,
Léon Koffi Konan,
Bi Irié Hervé Gouré Doubi
Issue:
Volume 10, Issue 4, December 2021
Pages:
67-74
Received:
15 October 2021
Accepted:
12 November 2021
Published:
9 December 2021
Abstract: The current context of sustainable development encourages the development of materials with low environmental impact, which explains the renewed interest in earthen constructions. This study is therefore a contribution to the valorization of clay raw materials from Côte d'Ivoire and agro-industrial waste in eco-construction. The aims of this study was studied the effect of shea butter wastes on the mineralogy and microstructure of Compressed Earth Bricks (CEB) stabilized with cement. To do this, two clay raw materials denoted F (Fronan) and K (Katiola) were sampled and then characterized. Various geotechnical and physicochemical tests have shown that these soils are loamy sand of class A2 and essentially contain quartz, kaolinite, mica and ferric compounds. As for shea butter wastes, it is mainly rich in lignin (32%); cellulose (28%) and hemicellulose (19%). Several samples of bricks with different percentages by mass of clay and shea butter wastes (0-10%), stabilized with 5% cement were prepared and then characterized. The results of the mechanical tests showed that the clay-cement matrix could contain 4% shea butter wastes for the formulations with clay F against 6% with clay K. The corresponding optimal formulations are F91TK4C5 and K89TK6C5 with clays F and K respectively. The SEM images showed a less dense microstructure for the optimal formulation F91TK4C5 compared to that of the clay-cement matrix unlike K89TK6C5 where the microstructure remained always dense. X-ray diffraction did not allow to observe mineralogical modifications with the incorporation of shea butter wastes into the clay-cement matrix due to their low quantities in the optimal formulations.
Abstract: The current context of sustainable development encourages the development of materials with low environmental impact, which explains the renewed interest in earthen constructions. This study is therefore a contribution to the valorization of clay raw materials from Côte d'Ivoire and agro-industrial waste in eco-construction. The aims of this study ...
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Study on the Preparation of Magnetic Pine Needle Biochar and Its Adsorption Performance for the Dye
Zhiyong Han,
Dehua Wang,
Jie Wu,
Qingyue Xiong,
Yanxia Zhang,
Kaiqing Zhang
Issue:
Volume 10, Issue 4, December 2021
Pages:
75-86
Received:
25 December 2021
Published:
29 December 2021
Abstract: The agricultural and forestry waste pine needle was selected to prepare the biochar which magnetized by the Fe3O4 to treat the typical wastewaters of the dye methylene blue (MB) and carmine (P4R) in view of the problem of quick increasing dye wastewater caused by the rapid development of textile, printing and dyeing industries, and the research result showed the experimental values of the maximum adsorption capacity of modified biochar for MB and P4R were 465.6mg·g-1 and 336.6mg·g-1 respectively. When the dosage of MBC is 0.010g and 0.015g, both the removal rate and the adsorption capacity can be maintained at a high level. Lower pH is conducive to the adsorption of P4R, and a higher pH is conducive to the adsorption of MB. As the adsorption time and initial dye concentration increase, the adsorption capacity of both dyes increases. As the temperature increases, the amount of MB adsorption increases, while the amount of P4R adsorption decreases and the adsorption of MB by MBC is a high-temperature spontaneous adsorption process, and the adsorption of P4R is a low-temperature spontaneous adsorption. The Langmuir model can better describe the adsorption process of MBC to MB, which is a single-layer adsorption, and the Freundlich adsorption model can better describe the adsorption process of MBC to P4R, which is a multi-layer adsorption. The adsorption of MB and P4R by MBC conforms to the quasi-second-order kinetic model.
Abstract: The agricultural and forestry waste pine needle was selected to prepare the biochar which magnetized by the Fe3O4 to treat the typical wastewaters of the dye methylene blue (MB) and carmine (P4R) in view of the problem of quick increasing dye wastewater caused by the rapid development of textile, printing and dyeing industries, and the research res...
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