678 research outputs found
Inclusions chemistry for Mn/Si deoxidized steels: Thermodynamic predictions and experimental confirmations
No full textInclusions chemistry of Mn/Si deoxidized steel was studied through both thermodynamic computation and experimental method. The computational thermodynamics has proved to provide a powerful tool for controlling inclusions and precipitates in steel. For Mn/Si deoxidized steels, important factors in determining the liquidus temperature and primary phase of the inclusions are MnO/SiO2 ratio and Al2O3 content in inclusions. Provided that no further interaction with steel matrix during cooling, inclusions having MnO/SiO2 mass% ratio near unity and Al2O3 content in the range of 10-20 mass% give low liquidus temperatures (1150-1200degreesC) and primary phases of MnSiO3 and Mn3Al2Si3O12 both which are soft. For the case of Mn + Si = 1.0 in mass%, the Mn/Si ratio of 2-5 meets the above conditions. Effect of the top slag on the inclusions chemistry can be predicted with accuracy, and hence it is possible to control the inclusions chemistry through proper design of the top slag composition so that the inclusions show a low liquidus temperature and soft primary phase. As the inclusions composition gradually changes with time toward the top slag composition, the length of refining time which determines the extent of reaction with the top slag is an important factor in determining the inclusions chemistry.X1151sciescopu
Experimental study of phase equilibria in the MnO-Si-2-"TiO2"-"Ti2O3" system
No full textPhase equilibria and liquidus surface in the system MnO-SiO2-"TiO2"-"Ti2O3" under controlled atmosphere have been investigated in the temperature range from 1200 to 1 500 degrees C and in the range of log PO2 from -7.6 (pCO/pCO(2)=1) to -16.6 (C-CO equilibration). High-temperature equilibration, quenching and electron probe microanalysis (EPMA) were employed to obtain equilibrium compositions of liquid and several solid solutions. The following primary phases have been observed; molten oxide, manganosite (MnO), ru-tile (TiO2-delta), tridymite and cristobalite (SiO2), tephroite (Mn2SiO4), rhodonite (MnSiO3), spinel (Mn2TiO4-MnTiO4), pyrophanite (MnTiO3-Ti2O3) and pseudobrookite ("MnTi2O5"-Ti3O5) solid solutions. By decreasing oxygen partial pressure, homogeneous liquid oxide area becomes smaller. No ternary compounds or ternary solid solutions were observed.X1121sciescopu
Experimental study of phase equilibria in the Mn0-"TiO2"-"Ti2O3" system
No full textPhase equilibria and liquiclus in the system MnO-"TiO2"-"TiO3" under controlled atmosphere have been investigated in the temperature range from 1300 to 1 550 degrees C and in the range of log pO(2) (in atm) from -7.2 (pCO/pCO(2) = 1) to -16.6 (C-CO equilibration). High-temperature equilibration, quenching and electron probe microanalysis (EPMA) were employed to obtain equilibrium compositions of liquid and several solid solutions. The following phases have been observed; molten oxide, manganosite (MnO (s.s.)), rutile (TiO2-delta (s.s.)), spinel (Mn2TiO4-MnTi2O4), pyrophanite (MnTiO3-Ti2O3) and pseudobrookite ("MnTi2O5"-Ti3O5) solid solutions. Liquidus of manganosite and rutile were measured and compared with previous investigations. "MnTi2O5" compound was confirmed to be unstable phase in the MnO-"TiO2" system. It was found in the present study that sub-solidus phase equilibria are affected considerably by oxygen partial pressure.X1117sciescopu
Practical application of thermodynamics to inclusions engineering in steel
No full textThe present work briefly outlines thermodynamic. databases of oxide solutions relevant to slags and inclusions in steelmaking processes and steel products, and reviews their application particularly to inclusions engineering. This paper then presents recent work on control of inclusions chemistry and phases in liquid steel, during solidification, and in solid steel by employing a computational thermodynamic technique and practical experiments. The system of the-present study consists of metallic steel (Fe-C-Si-Mn-Al-Ti-Mg-O-S), non-metallic oxides (Fe-Si-Mn-Al-Ti-Ca-Mg-O-S), and various compounds. It is demonstrated that theoretical predictions are in a striking agreement with experimental results on change in composition and phase of inclusions subjected to a number of different thermal and chemical conditions. (c) 2004 Elsevier Ltd. All rights reserved.X1110sciescopu
Critical thermodynamic evaluation and optimization of the MnO-SiO2-"TiO2"-"Ti2O3" system
No full textA complete review, critical evaluation, and thermodynamic optimization of phase equilibrium, and thermodynamic properties of the MnO-SiO2-"TiO2"-"Ti2O3" systems at 1 bar pressure are presented. The molten oxide phase was described by the Modified Quasichemical Model. The Gibbs energies of the manganosite, spinel, pyrophanite and pseudobrookite and rutile solid solutions were taken from the previous study. A set of optimized model parameters for the molten oxide phase was obtained which reproduces all available reliable thermodynamic and phase equilibrium data within experimental error limits from 25 degrees C to above the liquidus temperatures over the entire range of compositions and oxygen partial pressure in the range of pO(2) from 10(-20) bar to 10(-7) bar. Complex phase relationships in these systems have been elucidated, and discrepancies among the data have been resolved. The database of model parameters can be used along with software for Gibbs energy minimization in order to calculate any phase diagram section or thermodynamic properties. (C) 2006 Elsevier Ltd. All rights reserved.X1112sciescopu
Experimental and thermodynamic modeling of the MnO-SiO2-TiO2-Ti2O3 system
No full textThe MnO-siO(2)-TiO2-Ti2O3 system is a key oxide system for well known "Oxide Metallurgy" for HSLA steel. However, the available thermodynamic data for this system are rare and even the available experimental data are often inconsistent with each other. In the present study, experimental and thermodynamic modeling studies have been carried out on the MnO-siO2-TiO2-Ti2O3 system. High-temperature equilibration and quenching technique followed by EPMA (electron probe X-ray microanalysis) was used to determine liquidus temperatures and solid solubilities of the crystalline phases such as manganosite, rutile, spinel, pyrophanite, pseudobrookite, tridymite, etc. in the temperature range from 1200 degrees C to 1550 degrees C (1473 to 1823 K) under an atmosphere controlled by CO-CO2 gas mixture. These equilibrium data for the MnO-SiO2-TiO2-Ti2O3 system, combined with previously reported data for this system, were used to obtain an self-consistent set of optimized parameters of thermodynamic models for all phases. In addition, the application of the optimized thermodynamic database to oxide metallurgy was discussed.X11sciescopu
Inorganic nanoparticles with enzyme-mimetic activities for biomedical applications
No full text© 2019 Elsevier B.V.Spurred by the recent advances in the chemical synthesis of nanomaterials, a group of inorganic nanoparticles with enzyme-mimetic activities has emerged as a new candidate to lead the future of nanomedicine. These so-called nanozymes have several advantages over their natural counterparts, such as more robust catalytic activities over wide ranges of pH and temperature, more economical production cost, and higher design flexibility through the integration and modification of various functional molecules and nanomaterials. To help readers understand this rapidly expanding field, we herein provide a short overview of the enzyme-mimetic activities of inorganic nanoparticles and their applications, with an emphasis on ceria and iron oxide nanoparticles, two of the most widely used nanozymes. Properties of other inorganic nanoparticle-based nanozymes are also briefly summarized. Finally, their current limitations and future outlook are discussed11sciescopu
Phase equilibria and thermodynamic properties of the CaO-MnO-Al2O3-SiO2 system by critical evaluation, modeling and experiment
No full textA complete literature review, critical evaluation and thermodynamic modeling of phase diagrams and thermodynamic properties of the CaO-MnO-Al2O3-SiO2 system at 1 bar pressure are presented. A few new quaternary liquidus measurements are also reported. The modeling is based solely upon model parameters obtained by critical evaluation and optimization of the four ternary subsystems. The predicted quaternary properties and phase diagrams are in very good agreement with measurements. Complex phase relationships are elucidated and discrepancies among the data are resolved. The database of model parameters can be used along with software for Gibbs energy minimization in order to calculate any phase diagram section or thermodynamic property from 25degreesC to above the liquidus at all compositions.X1137sciescopu
Critical thermodynamic evaluation and optimization of the CaO-MnO-SiO2 and CaO-MnO-Al2O3 systems
No full textA complete review, critical evaluation, and thermodynamic optimization of phase equilibrium and thermodynamic properties of the CaO-MnO-SiO2 and CaO-MnO-Al2O3 systems at 1 bar pressure are presented. The molten oxide phase was described by the Modified Quasichemical Model, the Gibbs energy of the olivine solid solution was modeled with the Compound Energy Formalism, and the wollastonite s.s., rhodonite s.s., and alpha- and alpha'-Ca2SiO4 solutions were modeled by polynomial expansions of the excess Gibbs energy. Sets of optimized model parameters for all phases were obtained which reproduce all available reliable thermodynamic and phase equilibrium data within experimental error limits from 25degreesC to above the liquidus temperatures over the entire ranges of composition. The liquidus surface of the CaO-MnO-Al2O3 system, which has not been measured, has been predicted. Complex phase relationships in these systems have been elucidated, and discrepancies among the data have been resolved. Phase equilibria between liquid slag and manganese alloys have been calculated. The database of model parameters can be used along with software for Gibbs energy minimization in order to calculate any phase diagram section or thermodynamic property.X1127sciescopu
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