Mishra В.М.

Director NSF Center for Resource Recovery & Recycling, PhD, Professor, Worcester Polytechnic Institute

Effect of distilled water at high temperature on ductility and low-cycle fatigue of steel 10MgNi2MoV

https://doi.org/10.58224/2618-7183-2026-9-2-1
Аннотация
The results of experimental tests of 10MgNi2MoV steel samples for low-cycle fatigue at various deformation rates in air and in distilled water at a temperature of 280 °C in a rigid loading mode with a symmetrical change in the range of elastic-plastic deformations are presented.
Since it is technically difficult to create real operating conditions for the material of a nuclear reactor vessel and a steam generator in laboratory conditions, the authors of the article created testing equipment. The results of experimental tests have shown that high-temperature distilled water significantly reduces the durability of steel than air.
The composition of the water has a great influence; it has been found that neutral water is less damaging than water with high acidity. Distilled water of these parameters, along with a decrease in the cyclic strength of steel, significantly affects its plastic properties. It has been established that during low-cycle deformation in high-temperature water, the plasticity of steel is significantly affected by the rate of elastic-plastic deformation of the material. Plasticity decreases at a certain critical range of deformation rates.
A mathematical model of the change in the ductility of steel in high-temperature water from the rate of deformation of the material is presented.
It has been established that the operating mode of the equipment must be organized so that the deformation rates of the bearing elements are far from the critical deformation rates obtained experimentally.
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Utilization of serpentinite waste for the production of magnesium compounds

https://doi.org/10.58224/2618-7183-2025-8-5-8
Аннотация
The article presents the results of research on the complex processing of powdered man-made serpentinite waste formed during the enrichment of chrysotile raw materials in order to obtain high-purity magnesium compounds and assess the potential of their use in the production of building materials. The relevance of the work is due to the need to dispose of accumulated waste and expand the raw material base for the construction industry within the framework of the principles of circular economy. The developed technology includes the stages of acidic leaching of magnesium from PTW with sulfuric acid, neutralization and purification of the solution using thermally activated PTW (TA-PTW) and subsequent precipitation of the target products. It was found that thermal activation of waste at 750 °C leads to dehydroxylation and the formation of highly reactive phases, forsterite and periclase, which significantly increases their sorption activity. The optimal leaching regime is recognized as the use of 0.7 stoichiometrically normal amount of H₂so₄, which makes it possible to extract 82.5% of magnesium from the amount of acid introduced into the solution. The combined use of the initial and thermally activated PTW provides a degree of magnesium extraction of 52.3% of its total content in the system and effective purification of the magnesium sulfate solution from impurities of iron, aluminum, chromium and nickel. Sequential precipitation from the purified solution made it possible to obtain high–purity magnesium hydroxide with a calcium content of 0.0110%, and its subsequent calcination - magnesium oxide with a calcium content of 0.0187%. Special attention is paid to the prospects of practical application of synthesized compounds in the construction industry. It is shown that magnesium sulfate can be used as a modifying additive in cements and as a sealer for magnesia binders. Magnesium hydroxide is an effective flame retardant filler, and magnesium oxide is the main component for the production of flame–resistant and moisture-resistant magnesia binders and plates such as glass-magnesium sheets. Thus, the work demonstrates not only the technical feasibility of highly efficient processing of serpentinite waste, but also the significant resource potential of the resulting magnesium compounds for creating modern building materials with improved performance characteristics.
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