THERMODYNAMIC MODELING OF THE EQUILIBRIUM COMPOSITION OF THE REACTION PRODUCTS IN THE DEWATERING PROCESS OF THE CHANNEL OF URANIUM-GRAPHITE REACTOR

Author(s):  
A. O. Pavliuk ◽  
E. V. Bespala ◽  
S. G. Kotlyarevskiy ◽  
I. Yu. Novoselov
2020 ◽  
Vol 4 (1) ◽  
Author(s):  
Kang Wang ◽  
Junsoo Han ◽  
Angela Yu Gerard ◽  
John R. Scully ◽  
Bi-Cheng Zhou

AbstractThe potential-pH diagram, a graphical representation of the thermodynamically predominant reaction products in aqueous corrosion, is originally proposed for the corrosion of pure metals. The original approach only leads to stoichiometric oxides and hydroxides as the oxidation products. However, numerous experiments show that non-stoichiometric oxide scales are prevalent in the aqueous corrosion of alloys. In the present study, a room temperature potential-pH diagram considering oxide solid solutions, as a generalization of the traditional potential-pH diagram with stoichiometric oxides, is constructed for an FCC single-phase multi-principal element alloy (MPEA) based on the CALculation of PHAse Diagram method. The predominant reaction products, the ions in aqueous solution, and the cation distribution in oxides are predicted. The oxide solid solution is stabilized by the mixing free energy (or mixing entropy) and the stabilizing effect becomes more significant as the temperature increases. Consequently, solid solution oxides are stable in large regions of the potential-pH diagram and the mixing free energy mostly affects the equilibrium composition of the stable oxides, while the shape of stable regions for oxides is mostly determined by the structure of the stable oxides. Agreements are found for Ni2+, Fe2+, and Mn2+ between the atomic emission spectroelectrochemistry measurements and thermodynamic calculations, while deviations exist for Cr3+ and Co2+ possibly due to surface complexation with species such as Cl− and the oxide dissolution. By incorporating the solution models of oxides, the current work presents a general and more accurate way to analyze the reaction products during aqueous corrosion of MPEAs.


2020 ◽  
Vol 975 ◽  
pp. 59-64
Author(s):  
Andrey N. Anikeev ◽  
Ilia V. Chumanov ◽  
Vadim Sedukhin

Study of TiC interaction with low-and high-carbon steel is presented in this article. Was carried out interaction thermodynamic modeling in the temperature range of 900-1800 °C, which showed that titanium carbide would dissolve in melts with these compositions, regardless of melt’s carbon content at given parameters. The obtained thermodynamic results were verified by conducting an experiment with high-temperature complex in order to study substances interaction processes. The obtained experimental samples were studied with scanning microscope as well as structure and compounds composition, obtained as a result of experiment mentioned above.


2006 ◽  
Vol 911 ◽  
Author(s):  
Vladimir Sevastyanov ◽  
Yurij Ezhov ◽  
Roman Pavelko ◽  
Nikolaj Kuznetsov

AbstractHomologues with the general stoichiometry a(SiCl4) : bSi : cC : d(SiC) are shown to be potential precursors for the low-temperature gas-phase synthesis of silicon carbide. Thermal decomposition of these precursors yields the chemically stable gaseous species SiCl4 and condensed Si, C, SiC, SiC+Si, or SiC+C. Thermodynamic modeling of the thermal decomposition of octachlorotrisilane, Si3Cl8, is used to analyze the key features of the thermolysis of perchlorosilanes with the general stoichiometry a(SiCl4) : bSi. The equilibrium compositions of reaction products in the Si3Cl8+CO system are determined. This reaction system enables low-temperature (400 – 1200 K) synthesis of silicon carbide.


2012 ◽  
Vol 488-489 ◽  
pp. 300-304
Author(s):  
Tawat Chanadee ◽  
Jessada Wannasin ◽  
Sutham Niyomwas

The in-situself propagating high temperature synthesis technique were used to synthesis tungsten based intermetallic alloys from WO3/SiO2/Al and WO3/B2O3/Al reactant mixture system. The reaction was carries out in a SHS reactor under static argon gas at the pressure of 0.5 MPa. The standard Gibbs energy minimization method was used to calculate the equilibrium composition of the reacting species. The microstructure and phase distribution of the SHS reaction products were characterized by scanning electron microscopy (SEM) and energy dispersive x-ray (EDX), respectively. The results indicate that complete reaction of precursors to yield Al2O3-WSi2 and Al2O3-WB as product composites with clearly separation between Al2O3 and WB.


2021 ◽  
Vol 64 (11) ◽  
pp. 825-831
Author(s):  
I. A. Rybenko ◽  
E. V. Protopopov

One of the promising directions in metallurgy is the use of iron-containing waste, such as converter production sludge, iron-containing concentrates, rolling scale, iron ore processing waste and others. Development of new resource-saving technologies using such waste requires preliminary research and accumulation of information in the field of iron recovery. The paper considers the processes of iron recovery from oxides under various conditions. The authors used the method of thermodynamic modeling based on the search for the entropy maximum. The thermodynamic modeling tool was TERRA software package created at the Bauman Moscow State Technical University. TERRA complex is designed to calculate the thermodynamic properties and composition of the phases of equilibrium state of arbitrary systems with chemical and phase transformations. Using this software package, studies of the processes of iron recovery by various reducing agents (carbon, manganese, and silicon) in model thermodynamic systems were carried out, and optimal conditions for temperature and consumption of reducing agents were determined. The paper presents the results of a study of processes in the metal-slag system in equilibrium. The analysis of the metal-slag system equilibrium state was carried out for the temperature range of 1773 - 1973 K with different amounts of slag. Boundaries of the areas of redox processes were determined and the influence of metal components on conditions for iron oxides recovery from slag to metal was evaluated. The dependences of the system equilibrium composition on temperature at different ratios of metal and slag were obtained, as well as the optimal conditions for iron recovery.


2019 ◽  
Vol 59 (9) ◽  
pp. 125-131
Author(s):  
Alexander S. Vusikhis ◽  
◽  
Evgeny N. Selivanov ◽  
Stanislav N. Tyushnyakov ◽  
Victor P. Chentsov ◽  
...  

Thermodynamic modeling technique is used to describe the metal reduction from oxide melt by carbon monoxide. The B2O3-CaO-MeO (Me – Ni, Zn, Pb, Cu) system, was used with periodic output of the metal phase and gases from the working body. The approach originality is that the equilibrium is determined for each single portion of the gas injected into the working body, and the metal oxides content being reduced in each calculation cycle is taken from the previous data. This approach gives qualitative possibility to make simulated processes closer to real ones. The proposed method calculations allow determining, such parameters as the oxide melt and metal phase compositions, degree of elements reduction, oxide and metal phases mass ratio, equilibrium composition of the gas, reducing ability of gas utilization degree, and others, depending on the introduced gas quantities. Reducing process modeling of Nickel, Copper, Lead and Zinc from B2O3-CaO-MeO melts gives opportunity to determine the process for each metal. Copper reducing from CuO, goes with intermediate oxide (CuO → Cu2O → Cu) formation. Reduction of Nickel (NiO → Ni), Lead (PbO → Pbs + Pbg) and Zinc (ZnO → Zng) proceeds in one stage. The temperature dependence of the non-ferrous metals content in the oxide melt, its reduction degree and reducing agent quantity introduced are described by the second-order polynomial equations. The information obtained may be useful for thermo-extraction processes prognosis during the Nickel, Copper, Lead, and Zinc extraction from non-ferrous metallurgy slag in bubbling process of oxide melt by reducing gases.


2021 ◽  
Vol 346 ◽  
pp. 02027
Author(s):  
Nina Ilinykh ◽  
Anastasia Krivorigova ◽  
Boris Gelchinski ◽  
Sergey Ilinykh

Thermodynamic modeling of a powder self-fluxing material PGSR-2 based on nickel (wt. %): Ni-79.3, C-0.5, Cr-15, Si-3.2, B-2 was carried out. Modeling was executed in the temperature range of 300-6000 K in the atmosphere of air and gas mixture “92 vol. % air + 8 vol. % propane” at a total pressure of P=105 Pa. The temperature dependences of the equilibrium composition of the condensed and gas phases formed during the heating of the investigated system were calculated. It is shown that the distribution of the components of the condensed and gas phases changes significantly when the initial content of the powder material and the composition of the plasma-forming gas are changed.


Author(s):  
J.R. Walton

In electron microscopy, lead is the metal most widely used for enhancing specimen contrast. Lead citrate requires a pH of 12 to stain thin sections of epoxy-embedded material rapidly and intensively. However, this high alkalinity tends to leach out enzyme reaction products, making lead citrate unsuitable for many cytochemical studies. Substitution of the chelator aspartate for citrate allows staining to be carried out at pH 6 or 7 without apparent effect on cytochemical products. Moreover, due to the low, controlled level of free lead ions, contamination-free staining can be carried out en bloc, prior to dehydration and embedding. En bloc use of lead aspartate permits the grid-staining step to be bypassed, allowing samples to be examined immediately after thin-sectioning.Procedures. To prevent precipitation of lead salts, double- or glass-distilled H20 used in the stain and rinses should be boiled to drive off carbon dioxide and glassware should be carefully rinsed to remove any persisting traces of calcium ion.


Sign in / Sign up

Export Citation Format

Share Document