Change search
Refine search result
2345 201 - 241 of 241
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 201.
    Taniguchi, Yoshinori
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science. Nippon Steel Corporation, Japan.
    Sano, N.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Sulphide capacities of CaO-AI2O3-SiO 2-MgO-MnO slags in the temperature range 1673-1773 K2009In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 49, no 2, p. 156-163Article in journal (Refereed)
    Abstract [en]

    With a view to estimate the sulphide capacities of slags used in hot metal pretreatment processes, the sulphide capacities of CaO-AI2O 3-SiO2-MgO, CaO-AI2O3-SiO 2-MnO and CaO-AI2O3-SiO2-MgO-MnO slags in low SiO2 concentration region were measured in the temperature range 1 673-1 773 K. The gasslag equilibrium technique has been used for these measurements. From the results obtained, it was found that the MgO and MnO increased the sulphide capacity values of slag. A new empirical model based on optical basicity for sulphide capacity prediction of these slags was developed using the measured values of the present work and literature.

  • 202. Teng, L. D.
    et al.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Thermodynamic investigations of the Mn-Ni-C-N quarternary alloys by solid-state galvanic cell technique2005In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 388, no 2, p. 250-257Article in journal (Refereed)
    Abstract [en]

    In view of the important applications of carbides and nitrides of transition metals in the hard materials industries, the thermodynamic activities of manganese in Mn-Ni-C-N alloys have been studied by solid-state galvanic cell technique with CaF2 as the solid electrolyte. The phase compositions and microstructure of various alloys have been analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Nitrogen was introduced into the alloy by equilibrating with N-2 gas. It was established during the experiments that the solubility of nitrogen in the alloys was affected by the carbon content. A (Mn,Ni)(4)(N,C) nitride was formed during the nitriding procedure in the alloys. The electromotive force (EMF) measurements were carried out in the temperature range 940-1127 K in order to determine the activities of Mn in the alloys. The activities of manganese were calculated and compared with those of the corresponding Mn-Ni-C ternary alloys.

  • 203.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Refractory Corrosion During Steelmaking Operations2013In: Treatise on Process Metallurgy, Elsevier, 2013, Vol. 2, p. 283-303Chapter in book (Refereed)
    Abstract [en]

    Refractory corrosion during steelmaking operations is a complex phenomenon involving not only chemical wear but also physical/mechanical wear (such as erosion/abrasion) processes which may act synergistically. To understand the corrosion mechanisms, the following should all be examined together-refractory microstructure, melt properties, and their wetting and interaction at high temperatures. In this chapter, the corrosion mechanisms between solid refractories and liquid melts (slag or metal) will be discussed. The refractory corrosion test methods will be briefly summarized. The main focus is on the discussion of tar-bonded oxide refractories, which are widely used in steelmaking practice, and their corrosion mechanism. Local corrosion of refractories at the slag-metal interface is one of the important factors shortening the service life of the refractory during the steelmaking processes. The Marangoni effect plays an important role in the local refractory corrosion at the slag-metal interface.

  • 204. Teng, Lidong
    et al.
    Noguchi, Satoko
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Reduction kinetics of FeO-CoO solid solution by hydrogen gas2007In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 38, no 1, p. 55-61Article in journal (Refereed)
    Abstract [en]

    The reduction kinetics of the FeO-CoO solid solutions (Fe0.8CO0.2O, Fe0.7CO0.3O, and Fe0.6CO0.4O) by hydrogen gas has been investigated using the thermogravimetric technique. Isothermal experiments were carried out in the temperature range 573 to 973 K. The activation energies for the reduction were calculated from the results of the isothermal experiments, and a typical value for Fe0.8CO0.2O solid solution was 65.9 kJ/mol. The activation energy values were found to be higher than the corresponding values for FeO and COO obtained earlier under identical reduction conditions. Fine Fe-Co alloy particles were obtained by carrying out the reduction experiments using a fluidized bed reactor with the parameters defined by the thermogravimetric results. The transmission electron microscope and laser particle sizer studies confirmed that the particle size of the synthesized alloys is in the range of 20 to 300 nm. By using Vibrating sample magnetomer measurements, the saturation magnetization values (Ms) were evaluated to be 196 emu/g and the coercive field was 33 Oe for Fe0.8CO0.2.

  • 205.
    Thorning, Casper
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Zhang, Zuotai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Sridhar, Seetharaman
    Carnegie Mellon University.
    Grain Boundary Ridge Formation During Simultaneous Recrystallization and High Temperature Oxidfation of a Mn IF SteelManuscript (Other academic)
  • 206.
    Thorning, Casper
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Zhang, Zuotai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Sridhar, Seetharaman
    Carnegie Mellon University.
    The Effect of the Addition of Sb on Grain Boundary Ridge Formation During Simultanous Recrystallizaiton and High Temperature Oxidation of an Mn IF SteelManuscript (Other academic)
  • 207.
    Tilliander, Ulrika
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Synthesis of nano sized Cu and Cu-W alloy by hydrogen reduction2005Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The major part of the present work, deals with the reduction kinetics of Cu2O powder and a Cu2O-WO3 powder mixture by hydrogen gas, studied by ThermoGravimetric Analysis (TGA). The reduction experiments were carried out both isothermally and non-isothermally on thin powder beds over different temperature intervals. During the experiments, the reductant gas flow rate was kept just above the starvation rate for the reaction to ensure that chemical reaction was the rate-controlling step. The activation energy for the reactions was evaluated from isothermal as well as non-isothermal reduction experiments.

    In the case of the reduction of Cu2O, the impact of the stability of the copper oxide on the activation energy for hydrogen reduction under identical experimental conditions is discussed. A closer investigation of additions of Ni or NiO to Cu2O did not have a perceptible effect on the kinetics of reduction.

    In the case of the reduction of the Cu2O-WO3 mixture, the reaction mechanism was found to be affected in the temperature range 923-973 K, which is attributed to the reaction/transformation in the starting oxide mixture. At lower temperatures, Cu2O was found to be preferentially reduced in the early stages, followed by the reduction of the tungsten oxide. At higher temperatures, the reduction kinetics was strongly affected by the formation of a complex oxide from the starting materials. It was found that the Cu2O-WO3 mixture underwent a reaction/transformation which could explain the observed kinetic behavior.

    The composition and microstructures of both the starting material and the reaction products were analyzed by X-ray diffraction (XRD) as well as by microprobe analysis. vi Kinetic studies of reduction indicated that, the mechanism changes significantly at 923 K and the product formed had unusual properties. The structural studies performed by XRD indicated that, at 923 K, Cu dissolved in W forming a metastable solid solution, in amorphous/nanocrystalline state. The samples produced at higher as well as lower temperatures, on the other hand, showed the presence two phases, pure W and pure Cu. The SEM results were in conformity with the XRD analysis and confirmed the formation of W/Cu alloy. TEM analysis results confirmed the above observations and showed that the particle sizes was about 20 nm.

    The structure of the W/Cu alloy produced in the present work was compared with those for pure copper produced from Cu2O produced by hydrogen reduction under similar conditions. It indicated that the presence of W hinders the coalescence of Cu particles and the alloy retains its nano-grain structure. The present results open up an interesting process route towards the production of intermetallic phases and composite materials under optimized conditions.

    Download full text (pdf)
    FULLTEXT01
  • 208.
    Tilliander, Ulrika
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Hydrogen reduction of a Cu2O-WO3 mixture2006In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 2, p. 265-274Article in journal (Refereed)
    Abstract [en]

    In the present work, the reduction kinetics of Cu2O-WO3 mixtures by hydrogen gas was studied by thermogravimetric analyses (TGA). The reduction experiments were carried out both isothermally and nonisothermally on shallow powder beds in the temperature interval 673 to 1073 K. During the experiments, the reductant gas flow rate was kept just above the starvation rate for the reaction to ensure that chemical reaction was the rate-controlling step. The composition and microstructures of the reaction products were analyzed after each experiment by X-ray diffraction (XRD) as well as by microprobe analyses. In the temperature interval 673 to 923 K, copper oxide was found to be preferentially reduced in the early stages of the experiment followed by the reduction of tungsten oxide. The reaction mechanism was found to be affected by a reaction/transformation in the starting copper-tungsten oxide mixtures in the temperature interval 923 to 973 K. At temperatures higher than 973 K, the reduction of the complex oxide formed was found to have a strong impact on the reaction kinetics. The activation energy was evaluated, from the isothermal as well as nonisothermal reduction experiments, for the two stages of reduction identified. The XRD and scanning electron microscopy (SEM) studies indicated the formation of a metastable solution of copper in tungsten at about 923 K. The advantage of the hydrogen reduction route toward the bulk production of alloy powders in the nanosize is demonstrated.

  • 209.
    Tilliander, Ulrika
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Kinetics studies of hydrogen reduction of Cu2O2006In: Zeitschrift für Metallkunde, ISSN 0044-3093, Vol. 97, no 1, p. 72-78Article in journal (Refereed)
    Abstract [en]

    In present work, reduction kinetics Of Cu2O by hydrogen gas was studied by thermogravimetric analyses (TGA). The TGA experiments were carried out both isothermally and non-isothermally on shallow powder beds. It was established that additions of Ni or NiO did not have any serious effect on the kinetics of reduction of Cu2O. The composition and microstructures of the reaction products were analyzed after each experiment by X-ray diffraction (XRD) as well as by scanning electron microscopy (SEM). The activation energy for the reaction was evaluated from isothermal as well as non-isothermal reduction experiments and was found to be in good agreement. The impact of the stability of the oxide on the activation energy for hydrogen reduction is also discussed.

  • 210.
    Tilliander, Ulrika
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Bergqvist, Hans
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Morphology studies of a W/Cu alloy synthesized by hydrogen reduction2006In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 21, no 6, p. 1467-1475Article in journal (Refereed)
    Abstract [en]

    Because of the applications for W/Cu composite materials in high technology, the advantages of synthesizing this alloy by the hydrogen reduction route were investigated, with special attention to the properties of the product that was formed. Kinetic studies of reduction indicated that the mechanism changes significantly at 923 K, and the product had unusual properties. In the present work, morphological studies of the W/Cu alloy with 20 wt% Cu, produced at 923 K, were carried out by x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses. The structural studies performed by XRD indicated that, at 923 K, Cu dissolved in W, forming a metastable solid solution in the nanocrystalline state. The samples produced at higher as well as lower temperatures, on the other hand, showed the presence of two phases, pure W and pure Cu. The SEM results were in agreement with the XRD analysis and confirmed the formation of W/Cu alloy. TEM analysis results confirmed the above observations and showed that the particle sizes were about 20 nm. The structure of the W/Cu alloy produced in the present work was compared with those for pure Cu, produced from Cu2O produced by hydrogen reduction under similar conditions. This indicated that the presence of W hinders the coalescence of Cu particles, and the alloy retains its nano-grain structure. The present results open up an interesting process route toward the production of intermetallic phases and composite materials under optimized conditions.

  • 211.
    Trejo, Eder
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Martell, Fernando
    Sch Engn & Informat Technol, Inst Tecnol & Estudios Super Monterrey, Monterrey, Mexico .
    Micheloud, Osvaldo
    Sch Engn & Informat Technol, Inst Tecnol & Estudios Super Monterrey, Monterrey, Mexico .
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Llamas, Armando
    Sch Engn & Informat Technol, Inst Tecnol & Estudios Super Monterrey, Monterrey, Mexico .
    Montesinos-Castellanos, Alejandro
    Sch Engn & Informat Technol, Inst Tecnol & Estudios Super Monterrey, Monterrey, Mexico .
    A novel estimation of electrical and cooling losses in electric arc furnaces2012In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 42, no 1, p. 446-456Article in journal (Refereed)
    Abstract [en]

    A method to calculate electrical losses and a heat transfer model of a conventional Electric Arc Furnace (EAF) are presented. The application of a novel power theory for the EAF was used to compute electrical losses and it was compared with conventional power calculations. The electrical losses and electrical variables were used as input parameters to the proposed heat transfer model. Chemical energy sources were included as energy inputs to estimate the overall heat transferred including the heat losses in the cooling system. In the heat transfer model the furnace was divided in 11 inner surfaces and the radiation view factors between them were estimated by a commercial finite element software. Variations of the view factors for different arc coverage were evaluated. Different scenarios for cooling panels losses, with respect to arc coverage and thickness of slag layers adhered to cooling system panels, were analyzed. The approach presented in this work allows calculation of energy balances in electrical arc furnaces with low computational resources. Finally, the contribution of this research work is to define a framework for further research oriented to improve both the electrical and thermal energy efficiencies to increase productivity and reduce energy consumption in steel plants.

  • 212. Wang, H.
    et al.
    Nzott, M. M.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Decarburization of ferrochrome and high alloy steels with optimized gas and slag phases towards improved Cr retention2013In: Journal of Mining and Metallurgy, Section B: Metallurgy, ISSN 1450-5339, Vol. 49, no 2, p. 175-181Article in journal (Refereed)
    Abstract [en]

    Chromium is a high value metal and the retention of the same during the refining of high carbon ferrochrome as well as high alloy steel has significant economic and environmental impacts. The loss of chromium during the decarburization is generally minimized using argon-oxygen mixtures thereby reducing the oxygen partial pressure (PO2) of the oxidant gas. In the current study, experiments were carried out in an induction furnace and CO2 was introduced with the view to partly reduce PO2 and partly as an oxidizer. During these experiments, the decarburization of molten Cr-alloy was conducted using pure O2, pure CO2 or O2+CO2 mixtures. The results demonstrated that the Cr loss can be minimized under CO2 introduction. The kinetic analysis showed that the mass transfer is effective due to the production of 2CO gas molecules from one CO2 molecule during the reaction which will improve the stirring of the bath. Besides, CO2 reacts with carbon in melt is an endothermic reaction, introduction of CO2 could be a cooler during the refining process, hence the temperature could be controlled by controlling the diluting gas amount, in this case, the over heat of bath refractory could be prevented and the lifetime of refractory could be extended.

  • 213. Wang, H.
    et al.
    Yu, H.
    Teng, L.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Evaluation on material and heat balance of EAF processes with introduction of CO22016In: Journal of Mining and Metallurgy, Section B: Metallurgy, ISSN 1450-5339, Vol. 52, no 1, p. 1-8Article in journal (Refereed)
    Abstract [en]

    The advantages of using CO2 for the decarburization of high alloy steels have been recognized from environmental and economic view points. The present paper presents the heat and materials balances in the decarburization process with the introduction of CO2 as a diluting gas in Electric Arc Furnace (EAF) process for steel production. The aim is to optimize the amount of CO2 and the materials requirements, which includes the addition of scrap, hot metal and coolant. These estimations are also important to control the bath temperature, thereby prolong the lifetime of the refractory lining of the furnace. The present calculations enable an optimization of the CO2:O-2 ratio and materials input in the decarburization of carbon steel melts. Another important extension of the work is the possibility to enhance the addition of hot metal during steel making process. The present results show that addition of up to 20% hot metal is likely to the energy loss due to the introduction of 50% CO2 for a 110 tons EAF resulting in the saving of electric energy.

  • 214.
    Wang, Haijuan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Investigations on the Oxidation of Iron-chromium and Iron-vanadium Molten Alloys2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    With the progress of high alloy steelmaking processes, it is essential to minimize the loss of valuable metals, like chromium and vanadium during the decarburization process, from both economic as well as environmental view points. One unique technique to realize this aim, used in the present work, is the decarburization of high alloy steel grades using oxygen with CO2 in order to reduce the partial pressure of oxygen. In the present work, the investigation on the oxidation of iron-chromium and iron-vanadium molten alloys under CO2-O2 mixtures was carried out and presented in this dissertation.

    For oxidation study on Fe-Cr molten alloy with CO2-O2 mixtures, on the basis of thermodynamic analysis, energy balance calculation and modeling results, experimental validation in laboratory was carried out, and later on, the oxidation kinetics of Fe-Cr and Fe-Cr-C melts under controlled partial pressure of oxygen was investigated. Thermodynamics calculation and energy balance estimation demonstrated that, it is possible to use CO2 or CO2-O2 mixtures as decarburizers during EAF process and high initial carbon contents in the steel can be adopted at the beginning in order to reduce the cost.

    A generic model has been developed to describe the overall process kinetics prevailing in metallurgical reactors containing liquid metal and gas bubbles. This model is general and can be extended further to consider any gas liquid reactions in any chemical engineering reactor, and especially the metallurgical ones, like AOD. In the present dissertation, the model is applied in predicting the evolution of Cr and C contents in a Fe-C-Cr melt during injection of different O2-CO2 mixtures. The related simulation results illustrated that CO2 is efficient in Cr retention.

    In order to verify the modeling results, 1kg induction furnace experiments were carried out in the present laboratory. The results indicated that the predictions of the model are in good agreement with the experimental results. Meanwhile, the experimental results indicated that the Cr-losses can be significantly lowered by replacing the oxygen with CO2 in the injected gas, specifically for Fe-Cr-C melts with carbon levels higher than about 0.8 mass%. Subsequently, the oxidation kinetics of Fe-Cr and Fe-Cr-C melts was investigated under different CO2-O2 mixtures. It is indicated that, the oxidation rate is controlled by the chemical reaction at the initial stage and the reaction rate can be expressed as  at the Cr range of 11-21 mass% in the Fe-Cr melt.

    For oxidation study on Fe-V liquid alloy, the investigation of the oxidation kinetics was carried out under CO2-O2 mixtures, which is followed by the study on thermodynamic properties of vanadium containing slags. During oxidation of Fe-V melt, in the case of alloys with vanadium contents exceeding 10 mass%, there exists an incubation period before the chemical reactions prevail the process. In addition, the ‘incubation time’ increased with the increase of temperature and the vanadium content, whereas it decreased with the increase of oxygen partial pressure in the oxidant gas.

    High-temperature mass spectrometric method was used to determine the activity of the vanadium oxide in CaO-MgO-Al2O3-SiO2-V2O3 slags, whereas, the oxidation states of vanadium in the CaO-MgO-Al2O3-SiO2-VOxslag system was studied by XANES method. The results indicated that, higher basicities stabilize higher vanadium oxidation state, whereas, higher temperature stabilizes lower vanadium oxidation state.

    The present work, which was carried out within the ECO-STEELMAKING project funded by MISTRA via Jernkontoret is expected to lead to implementation of some modifications in high alloy steel production based on fundamental concepts towards more environment-friendly steel processing.

    Download full text (pdf)
    FULLTEXT02
  • 215.
    Wang, Haijuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Determination of vanadium oxidation states in CaO-MgO-Al2O3-SiO2-VOxsystem by K edge XANES methodIn: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916Article in journal (Other academic)
  • 216.
    Wang, Haijuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Stolyarova, V. L.
    Lopatin, S. I.
    Kutuzova, M. E.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    High-temperature mass spectrometric study of the vaporization processes of V2O3 and vanadium-containing slags2010In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 24, no 16, p. 2420-2430Article in journal (Refereed)
    Abstract [en]

    A Knudsen effusion mass spectrometric method was used to study the vaporization processes and thermodynamic properties of pure V2O3 and 14 samples of vanadium-containing slags in the CaO-MgO-Al2O3-SiO2 system in the temperature range 1875-2625 K. The system was calibrated using gold in the liquid state as the standard. Vaporization was carried out from double tungsten effusion cells. First it was shown that, in vapor over V2O3 and the vanadium-containing slags in the temperature range 1875-2100 K, the following vapor species were present: VO2, VO, O, WO3 and WO2, with the latter two species being formed as a result of interaction with the tungsten crucibles. The temperature dependencies of the partial pressures of these vapor species were obtained over V2O3 and the slags. The ion current comparison method was used for the determination of the V2O3 activities in slags as a function of temperature with solid V2O3 as a reference state. The V2O3 activity coefficients in the slags under investigation indicated positive deviations from ideality at 1900 K and a tendency to ideal behavior at 2100K. It was shown that the V2O3 activity as a function of the slag basicity decreased at 1900 K and 2000 K and was practically constant in the slag melts at 2100K. The results are expected to be valuable in the optimization of slag composition in high-alloy steelmaking processes as well as for their environmental implications. Copyright (C) 2010 John Wiley & Sons, Ltd.

  • 217.
    Wang, Haijuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Investigation of the oxidation kinetics of Fe-Cr and Fe-Cr-C melts undercontrolled oxygen partial pressures2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 6, p. 1476-1487Article in journal (Other academic)
    Abstract [en]

    In the current work, oxidation kinetics of Fe-Cr and Fe-Cr-C melts by gas mixtures containing CO2 was investigated by Thermogravimetric Analysis (TGA). The experiments were conducted keeping the melt in alumina crucibles, allowing the alloy melt to get oxidized by an oxidant gas. The oxidation rate was followed by the weight changes as a function of time. The oxidation experiments were conducted using various mixtures of O-2 and CO2 with = 10(-2) to 10(4) Pa. In order to understand the mechanism of oxidation, the wetting properties between the alumina container and the alloys used in the thermogravimetric analysis (TGA) experiments and the change of the alloy drop shape during the course of the oxidation were investigated by X-ray radiography.The experiments demonstrated that the oxidation rate of Fe-Cr melt increased slightly with temperature under the current experimental conditions, but it is strongly related to the Cr-content of the alloy as well as the oxygen partial pressure in the oxidant gas mixture, both of which caused an increase in the rate. For the Fe-Cr-C system, the oxidation rate has a negative relationship with carbon content, viz. with increasing carbon, the oxidation rate of the alloy melt slightly decreased. The chemical reaction was found to be the rate determining step during the initial stages, whereas as the reaction progressed, the diffusion of oxygen ions through slag phase to the slag-melt interface was found to have a strong impact on the oxidation rate. The overall impact of different factors on the chemical reaction rate for the oxidation process derived from the current experimental results can be expressed by the relationship: A model for describing the kinetics of oxidation of Fe-Cr and Fe-Cr-C alloys under pure CO2 was developed. Simulation of the oxidation kinetics using this model showed good agreement with the experimental results.

  • 218.
    Wang, Haijuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Zhang, Jiayun
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Oxidation of Fe-V Melts Under CO2-O-2 Gas Mixtures2010In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 5, p. 1042-1051Article in journal (Refereed)
    Abstract [en]

    The oxidation mechanism of liquid Fe-V alloys with V content from 5 to 20 mass pct under different oxygen partial pressures using CO2-O-2 mixtures with CO2 varying from 80 pct to 100 pct was investigated by thermogravimetric analysis between 1823 K and 1923 K (1550 degrees C and 1650 degrees C). The products after oxidation were identified by scanning electron microscopy energy-dispersive spectrograph and X-ray diffraction. The results indicate that the oxidation process can be divided into the following steps: an apparent incubation period, followed by a chemical reaction step with a transition step before the reaction, and diffusion as the last stage. At the initial stage, a period of slow mass increase was observed that could be attributed to possible oxygen dissolution in the liquid iron-vanadium coupled with the vaporization of V2O. The length of this period increased with increasing temperature as well as vanadium content in the melt and decreased with increasing oxygen partial pressure of the oxidant gas. This analysis was followed by a region of chemical oxidation. The oxidation rate increased with the increase of the O-2 ratio in the CO2-O-2 gas mixtures. During the final stage, the oxidation seemed to proceed with the diffusion of oxygen through the product layer to the reaction front. The Arrhenius activation energies for chemical reaction and diffusion were calculated, and kinetic equations for various steps were setup to describe the experimental results. The transition from one reaction mechanism to the next was described mathematically as mixed-control equations. Thus, uniform kinetic equations have been setup that could simulate the experimental results with good precision.

  • 219.
    Wang, Haijuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Viswanatha, N.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Oxidation kinetics of ferrochrom under controlled oxygen pressures2010In: Proceedings of the 12th International Ferroalloys Congress: Sustainable Future, 2010, p. 411-419Conference paper (Refereed)
    Abstract [en]

    In order to make the stainless steel making process efficient and environment friendly, it is essential to minimize the loss of chromium to the slag phase. With a view to investigate the advantages of using CO2 to attain moderate oxygen partial pressures in the oxidant gas during the decarbirization of stainless steel, the present experiments were carried out to understand the oxidation kinetics of Fe-Cr alloy and Fe-Cr-C alloy with gas mixtures containing CO2. In the present work, the oxidation behavior of Fe-Cr was examined by thermogravimetric analysis (TGA). Various mixtures of O2 and CO2 were used as the oxidant gas and the oxidation rate was followed by the weight changes as a function of time. One trial was made on the oxidation of Fe-Cr-C alloy with CO2 as the oxidant. The experiments demonstrated that the oxidation rate is independent of temperature at present experimental situation, but has strongly related to the Cr-content of the alloy as well as the oxygen partial pressure in the oxidant gas mixture. The wetting of alumina by the iron drop and the change of the drop shape during the course of the oxidation were investigated by X-ray radiography.

  • 220.
    Wang, Haijuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Viswanathan, N. N.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Oxidation kinetics of Fe-Cr and Fe-V liquid alloys under controlled oxygen pressures2010In: Energy technology 2010 : conservation, greenhouse gas reduction and management, alternative energy sources: proceedings of symposia sponsored by the Light Metals Division of the Minerals, Metals & Materials Society (TMS) ; held during TMS 2010 Annual Meeting & Exhibition Seattle, Washington, USA, February 14-18, 2010, 2010, p. 215-230Conference paper (Refereed)
    Abstract [en]

    In order to make the stainless steel making process efficient and environment friendly, it is essential to minimize the loss of chromium to the slag phase. With a view to investigate the advantages of using CO2 to attain moderate oxygen partial pressures in the oxidant gas during the decarburizations of stainless steel, the present experiments were carried out to understand the oxidation kinetics of Fe-Cr alloys and Fe-V alloy with gas mixtures containing CO2 In the present work, the oxidation behavior of Fe-Cr and Fe-V was examined by thermogravimetric analysis (TGA). Various mixtures of O2 and CO2 were used as the oxidant gas and the oxidation rate was followed by the weight changes as a function of time. The experiments demonstrated that the oxidation rate is independent of temperature at present experimental situation, but has strongly related to the Cr-content of the alloy as well as the oxygen partial pressure in the oxidant gas mixture. The wetting of alumina by the iron drop and the change of the drop shape during the course of the oxidation were investigated by X-ray radiography.

  • 221.
    Wang, Haijuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Viswanathan, Nurni N.
    Ballal, N. B.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Modelling of Physico-Chemical Phenomena between Gas inside a Bubble and Liquid Metal during Injection of Oxidant Gas2010In: INT J CHEM REACT ENG, ISSN 1542-6580, Vol. 8Article in journal (Refereed)
    Abstract [en]

    Gas liquid reactors are extensively used in many metallurgical processes involving the refining of liquid metals. In these processes, reactions leading to the oxidation of various solutes in liquid metal often compete with each other, which ultimately determine the liquid metal composition. In the present paper, a model has been proposed to simulate the evolution of solute contents in a metallic melt considering mass transfer of solutes in the melt in the vicinity of the bubble, equilibrium at the gas-metal interface and gas composition evolution in the bubble during its ascent through the melt. The composition of solutes at the metal-gas interface in principle can be altered by changing the injected gas composition.

    The model was applied to the case of oxygen injection through a lance into liquid steel-containing C and Cr, aiming sufficient decarburization without much oxidation of Cr to the slag. The Cr loss to the slag by oxidation is generally much more than that expected based on equilibrium thermodynamics applied to the bulk metal and gas. The actual Cr loss, as shown by the present model, is determined by the composition of solutes at the metal-gas interface rather than in the bulk. The effect of change of the partial pressure of oxygen in the bubble by replacing oxygen by carbon dioxide in the injected gas and the corresponding evolution of C and Cr contents in the melt was simulated. Some preliminary experiments were conducted to validate the model predictions. The frame work of the model is generic and can be extended to many gas-liquid metal reactors in liquid metal processing.

  • 222.
    Wang, Haijuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Viswanathan, Nurni N.
    Ballal, N. Bharath
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Modeling of Reactions between Gas Bubble and Molten Metal Bath-Experimental Validation in the Case of Decarburization of Fe-Cr-C melts2009In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 28, no 6, p. 407-419Article in journal (Refereed)
    Abstract [en]

    A theoretical generic model describing the mass transfer phenomena between rising gas bubbles and a metal bath has earlier been developed by the present authors, to predict the composition change in the melt as consequence of blowing different oxidant gases. In order to verify the model predictions, a series of experiments involving reactions between Fe-Cr-C melts and different O(2)-CO(2) gas mixtures were carried out. The results showed that the decarburization deviates significantly from thermodynamic paths predicted on the basis of bulk compositions and that the model was able to make reasonably reliable predictions of the changes of chromium and carbon contents in the melt as a function of time. According to the model, the compositions at the vicinity of injection point as well as at the gas-melt interface in the bubble are likely to be far from that in the bulk. The results of the present set of experiments showed, with CO(2) injection, the utilization of the available oxygen for decarburization was higher as compared to O(2) injection in the case of melts containing higher carbon levels (>1mass%). Reverse is the case in low carbon melts. The results also indicate relatively less Cr-losses from the metal bath when CO(2) is used as the oxidant. As the model predictions are found to be reasonably reliable, the model predictions are extended to predict the impact of the variation of different process parameters.

  • 223. Wang, Haijuan
    et al.
    Wang, Lijun
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Determination of Vanadium Oxidation States in CaO-MgO-Al2O3-SiO2-VOx System by K Edge XANES Method2016In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 87, no 2, p. 199-209Article in journal (Refereed)
    Abstract [en]

    The oxidation states of vanadium in the CaO-MgO-Al2O3-SiO2-VOx slag system are investigated with the initial V2O5 concentration in the range of 1-10 mole fraction, in the temperature range, 1823-1923K, partial pressures of oxygen from 10(-5) to 10(3)Pa, and with the basicities in the range of 0.85-2.20. The valance states of vanadium are determined by the X-Ray Absorption Near-Edge Structure (XANES) method. The results indicates that, for the oxide VOx, at a given temperature, and basicity, x is found to increase slightly with increase of initial V2O5 concentration. With the increase of slag basicity, x is increased. It is also found that x in VOx decreases with the increase of temperature, whereas, at constant basicity, the value of x increases with the increased oxygen partial pressure. The present results are useful in the quantification of V3+/V4+ and V4+/V5+ ratios for a given slag as functions of basicity, temperature, and oxygen partial pressure.

  • 224.
    Wang, Lijun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Chou, Kuo-chih
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    A comparison of tradition geometrical models and mass triangle model in calculation the surface tensions of ternary sulphide melts2008In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 32, no 1, p. 49-55Article in journal (Refereed)
    Abstract [en]

    Surface tension of the Ni3S2-FeS-Cu2S ternary mattes has been calculated using a mass triangle model as well as six traditional geometrical models based on the same calculation data to investigate the difference between mass triangle model and other kinds of geometrical models. From the calculated results, it might be seen that, the mass triangle model, irrespective of the method of selection of the binary data, would give the best results compared with other traditional geometrical models. The mean square root errors of the mass triangle method only range from 1.09% to 2.8%, which are almost within the experimental error of 2.5%.

  • 225.
    Wang, Lijun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Chou, Kuo-chih
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    A new method for evaluating some thermophysical properties for ternary system2008In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 27, no 2, p. 119-126Article in journal (Refereed)
    Abstract [en]

    In our earlier papers, we have presented a new method, named the mass triangle model, for calculating physicochemical properties in the ternary system within a limited solubility area. This model was shown to be superior to traditional geometrical models in the computation of ternary data from the known data for the corresponding binaries. In the present paper, the authors extend this method to a ternary system where the entire compositional area inside the ternary triangle is homogeneous. The successful application of this new method to the estimation of surface tension and density has been demonstrated in the case of the system Ni(3)S(2)-FeS-Cu(2)S at 1473K with mean square root error of +/- 1.83%, +/- 4.33% respectively, compared with the experimental results.

  • 226. Wang, Li-jun
    et al.
    Hayashi, Miyuki
    Chou, Kuo-chih
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    An Insight into Slag Structure from Sulphide Capacities2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 6, p. 1338-1343Article in journal (Refereed)
    Abstract [en]

    The molar sulphide capacities = (mol pct S) ()(1/2) on four binary systems, MgO-SiO2, CaO-SiO2, MnO-SiO2 and FeO-SiO2 are elucidated so as to compare the magnitudes of the basicities of four metallic oxides and to estimate the temperature dependencies of the basicities of metallic oxides. The enthalpy changes of the reaction 2O(-) = O + O2-, viz. the silicate polymerization reaction (denoted as ) have been calculated from the slopes of the log vs 1/T curves for four binary silicates. The value is considered in the present work to be an index of the basicity of silicate melts. The basicities obtained on the basis of the values are in the order MgO < CaO < MnO < FeO, which are determined by two effects; (i) ionicity of chemical bonds between metallic and oxygen ions and (ii) clustering of metallic oxides in silicates. It is also found that the basicity of the FeO-SiO2 system is larger at higher temperatures.

  • 227.
    Wang, Lijun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Experimental Studies on the Oxidation States of Chromium Oxides in Slag Systems2010In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 5, p. 946-954Article in journal (Refereed)
    Abstract [en]

    In view of the importance of the thermodynamic behavior of chromium in the slag phase as well as the serious discrepancies in the earlier reports on the valence state of chromium in slag melts, the oxidation state of chromium oxides in CaO-SiO2-CrOx and CaO-MgO-(FeO-) Al2O3-SiO2-CrOx were investigated experimentally in the present study using two different experimental techniques. The gas-slag equilibrium technique was adopted to study the CaO-SiO2-CrOx system between 1823 K (1550 °C) and 1923 K (1650 °C) and equilibrated with mixtures of CO-CO2-Ar gases corresponding to three different oxygen partial pressures (between 10-4 and 10-5 Pa). After equilibrating, the samples were quenched and subjected to analysis using the X-ray absorption near edge structure method to determine the distribution ratio of Cr2+/Cr3+ in the slags. The second technique examined the applicability of the high-temperature mass spectrometric method combined with the Knuden effusion cell for quantifying the valence states of Cr in the multicomponent system CaO-MgO-(FeO-) Al2O3-SiO2-CrOx up to a maximum temperature of 2000 K (1727 °C). The results showed that the Knudsen cell-mass spectrometric method could be used successfully to estimate the valence ratio for Cr in silicate melts. According to the present study, the Cr2+/Cr3+ ratio increased with increasing temperature and a decreasing slag basicity as well as the oxygen partial pressure prevailing in the system. A mathematical correlation of XCrO/XCrO1.5 as a function of temperature, oxygen partial pressure, and basicity was developed in the present work based on the present results as well as on those assessed from earlier data.

  • 228.
    Wang, Lijun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Experimental Studies on the Sulfide Capacities of CaO-SiO2-CrOx Slags2010In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 2, p. 367-373Article in journal (Refereed)
    Abstract [en]

    To understand the desulfurization process during the refining of Cr-containing steel grades, this work was initiated to study the reactions between Cr-sulfur and chromium-containing slags. The sulfide capacities of CaO-SiO2-CrOx pseudo-ternary slags were measured using the traditional gas-slag equilibration technique between 1823 K and 1923 K. Sixteen different slag compositions were examined, and two different equilibrium oxygen partial pressures were used to understand the impact of the varying valence of Cr on the sulfide capacities. The results showed that log(10) Cs varied linearly with the reciprocal T, and the slope was higher than the corresponding value reported for the binary CaO-SiO2 of corresponding composition. It was difficult to isolate the relative effects of the bi- and trivalent Cr in the slags because the Cr2+/Cr3+ ratio was influenced by the basicity of the slag. By using the equation developed by these authors earlier that related Cr2+/Cr3+ with basicity, oxygen partial pressure, and temperature, it was possible to obtain an approximate trend of the CrO effect on the sulfide capacities; viz. the sulfide shows a decreasing trend as Cr2+ replaces Ca2+ in the slag. With a continued increase of Cr2+ content, indications of the occurrence of a minimum point were observed; beyond which the sulfide capacities showed a slight increasing trend. The latter was attributed, based on slag-structure analysis by Gaskell et al., to the increasing extent of the polymerization reaction releasing oxygen ions for sulfide reactions.

  • 229.
    Wang, Lijun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Taniguchi, Yoshinori
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Measurements of Solidus and Liquidus Temperatures of CaO-Al2O3-SiO2 and CaO-MgO-Al2O3-SiO2 Slags with MnO Additions2012In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, no 2, p. 157-161Article in journal (Refereed)
    Abstract [en]

    The present work was carried out with a view to re-examine the phase diagram aspects of CaO?Al2O3?SiO2 and CaO?MgO?Al2O3?SiO2 slags with MnO additions. The aim was to confirm the homogeneous liquid range necessitated for sulfide capacities measurements of the above-mentioned slags. The liquidus and solidus temperatures of these slags were measured by DSC and X-ray radiograph techniques. The experimental results were compared with the liquidus and solidus temperatures obtained from literature (Slag Atlas) and commercial softwares ThermoCalc and FactSage. The results indicate that there is good agreement between the experimental values and those retrieved from literature and the commercial software in the case of the ternary system CaO?Al2O3?SiO2. For the CaO?MgO?MnO?Al2O3?SiO2 system, significant deviations were observed between the different sources. The present observations indicate that X-ray radiography can be a very useful tool in estimating the solidus temperatures of slags while DSC would complement the information with respect to liquidus temperatures.

  • 230. Wang, Lijun
    et al.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Chou, Kuo-Chih
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Determination of Vanadium Valence State in CaO-MgO-Al2O3-SiO2 System By High-Temperature Mass Spectrometry2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 4, p. 948-953Article in journal (Refereed)
    Abstract [en]

    In the present study, the applicability of the high-temperature mass spectrometric method combined with Knudsen effusion cell for quantifying the valence states of V in the multicomponent system CaO-MgO-Al2O3-SiO2-VO (x) up to a maximum temperature of 2050 K (1777 A degrees C) was examined. The valence ratio of V3+/V4+ in slag phase was derived from the partial pressures of VO and VO2 in the effused vapor phase. The results show good agreement with the literature values obtained by other techniques. A correlation between the valence ratio V3+/V4+ and the oxygen partial pressure as well as basicity was achieved based on the present results and accessed data in the literature. The results of the present study demonstrate that the Knudsen cell-mass spectrometric method can be a very effective tool in estimating the valence ratios for of transition metals in metallurgical slags.

  • 231. Wang, Li-jun
    et al.
    Yu, Ji-peng
    Chou, Kuo-chih
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Effects of MgO and Al2O3 Addition on Redox State of Chromium in CaO-SiO2-CrOx Slag System by XPS Method2015In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, no 4, p. 1802-1808Article in journal (Refereed)
    Abstract [en]

    The effects of MgO and Al2O3 on the redox state of chromium in CaO-SiO2-CrO), system have been investigated at 1873 K (1600 degrees C) under Ar-CO-CO2 atmosphere and analyzed by means of X-ray photoelectron spectroscopy. From the analysis of the Cr 2p core level spectra, it was found that both Cr(II) and Cr(III) exist simultaneously in CaO-MgO/Al2O3-SiO2-CrOx, and the quantitative ratio Cr(II)/Cr(III) has been obtained by deducing from the area under the computer-resolved peaks. Substitutions of CaO by MgO, SiO2 by Al2O3 favored the Cr(II) state existing in the system in the composition ranges of 3 to 10 wt pct MgO and 5 to 20 pct Al2O3. Meanwhile, from the analysis of the Ols spectra in CaO-MgO-SiO2-CrOx, it was found that the ratio of the non-bridging oxygen content increased first due to the CrO contribution to the electron distribution uniformly as 0- at MgO low content. Afterward, it went to decreasing with continuing addition of MgO because ionic contribution of MgO is less than that of CaO and the influence of the CrO clustering on the non-Bridging oxygen is limited due to only 5 wt pct Cr Ox. In CaO-Al2O3-SiO2-CrOx system, COI) acts as a network modifier to compensate Al-3 charge balance to make the structure stable, so the non-bridge oxygen in this system continues decreasing. (C) The Minerals, Metals & Materials Society and ASM International 2015

  • 232.
    Wei, Guohui
    et al.
    Shanghai Inst Technol, Sch Mat Sci & Engn, Shanghai 201418, Peoples R China..
    Zheng, Dongmei
    Shanghai Inst Technol, Sch Mat Sci & Engn, Shanghai 201418, Peoples R China..
    Xu, Lijuan
    Shanghai Inst Technol, Sch Mat Sci & Engn, Shanghai 201418, Peoples R China..
    Guo, Qiangsheng
    Shanghai Inst Technol, Sch Chem & Environm Engn, Shanghai 201418, Peoples R China..
    Hu, Jianfeng
    Shanghai Univ, Sch Mat Sci & Engn, Shangda Rd, Shanghai 200444, Peoples R China..
    Sha, Na
    Shanghai Inst Technol, Sch Chem & Environm Engn, Shanghai 201418, Peoples R China..
    Zhao, Zhe
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science. Shanghai Inst Technol, Sch Mat Sci & Engn, Shanghai 201418, Peoples R China..
    Photothermal catalytic activity and mechanism of LaNixCo1-xO3(0 <= x <= 1) perovskites for CO2 reduction to CH4 and CH3OH with H2O2019In: MATERIALS RESEARCH EXPRESS, ISSN 2053-1591, Vol. 6, no 8, article id 086221Article in journal (Refereed)
    Abstract [en]

    A series of LaNixCo1-xO3 perovskites were synthesized by sol-gel combustion method, the photothermal catalysis of CO2 and H2O into CH4 and CH3OH was investigated systematically. The crystal structure, surface area, oxygen vacancies, band structures and catalytic performance of LaNixCo1-xO3 perovskites were characterized thoroughly in order to understand the design principle of the material for such a photothermal catalysis of CO2 and H2O. With the change of x value, the best catalytic performance was achieved at x = 0.4 and the accumulated yield of CH4 and CH3OH can reach 678.57, 20.83 mu molg(-1) in 6 h, which were 3.4 and 3.8, 1.9 and 2.2 times of that of two end composition, LaCoO3 and LaNiO3 under the same condition. For LaNi0.4Co0.6O3, the surface area reached a maximum concentration of oxygen vacancy while the band gap reached a minimum of 1.42 eV. It is evident that the formation of solid solution between LaMO3 (M = transition metals) compounds can be a general strategy for the new catalyst design.

  • 233. Xie, J. Y.
    et al.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Chen, N. X.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Study of Chromium Activity in the Cr-Fe-N System by Galvanic Cell Method2010In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 41A, no 1, p. 172-180Article in journal (Refereed)
    Abstract [en]

    In the present work, the Cr-Fe-N alloys with different compositions were synthesized by nitriding the Cr-Fe powder mixtures in the purified nitrogen gas (101,325 Pa) at 1473 K for 2 weeks. The phase relationships in the synthesized alloys and the alloys equilibrated at 1173 K were carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The nitrogen content in the alloys equilibrated in the nitrogen gas (101,325 Pa) at 1173 K was analyzed using the inert-gas fusion thermal conductivity (IGFTC) method. The thermodynamic activities of Cr in Fe-Cr-N alloys were measured in the temperature range 973 to 1123 K using the solid-state galvanic cell technique with CaF2 single crystal as the solid electrolyte. Based on the measured EMF values, the chromium activities in the alloys were calculated with respect to pure Cr with bcc structure as the standard state. The effect of nitrogen on Cr activities in the Cr-Fe-N system was examined by comparing the experimental results of the Cr activities in the Cr-Fe and Cr-Fe-C systems.

  • 234.
    Xie, Jiaying
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Chen, Nan-Xian
    Shen, Jiang
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Atomistic study on the structure and thermodynamic properties of Cr7C3, Mn7C3, Fe7C32005In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 53, no 9, p. 2727-2732Article in journal (Refereed)
    Abstract [en]

    The crystal structures and stabilities of Cr7C3, Mn7C3, Fe7C3 have been investigated using the interatomic potentials obtained by the lattice inversion method. The calculated structures of Cr7C3, Mn7C3 and Fe7C3 are proposed to be hexagonal with P6(3)mc space group and the calculated lattice constants are in basic agreement with the experimental data. The calculated cohesive energies indicate that the increase in the atomic number of the metal is accompanied by the decrease in the stability of its carbides. The phonon density of states and vibrational entropy related to dynamic phenomena are also evaluated. This work provides a new method for studying the properties of carbides with complex structure.

  • 235. Xie, Jiaying
    et al.
    Shen, Jiang
    Chen, Nanxian
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Site preference and mechanical properties of Cr23-xTxC6 and Fe21T2C6 (T = Mo, W)2006In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 54, no 18, p. 4653-4658Article in journal (Refereed)
    Abstract [en]

    The site preference, stability, crystal structure and mechanical properties of Cr23-xTxC6 and Fe21T2C6 (T = Mo, W) carbides have been investigated using inverted pair potentials. Among the four different kinds of metal sites in these compounds, the most preferential sites for Mo atoms or W atoms are 8c sites. The result of stability indicates that each of the Mo atoms and W atoms significantly increases the stability of Cr23C6 and Fe23C6. The stability of Fe21T2C6 is lower than that of Cr21T2C6 and the carbides containing W atoms are more stable than those containing Mo atoms. The calculated structural properties are in good agreement with experimental data. Further-more, the mechanical properties have also been evaluated and the results indicate that Mo atoms or W atoms can improve the hardenability of the systems.

  • 236.
    Xie, Jiaying
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Teng, Li-Dong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Chen, Nan-Xian
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Atomistic simulation on the structural properties and phase stability for Cr23C6 and Mn23C62006In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 420, no 1-2, p. 269-272Article in journal (Refereed)
    Abstract [en]

    Based on the successful applications of lattice inversion method in many fields, the crystal structure and phase stability of Cr23C6 and Mn23C6 are investigated using the interatomic potentials obtained by lattice inversion method in this research. The calculated atomic coordinates and crystal parameters are in good agreement with the experimental results and the phase stability of Cr23C6 and Mn23C6 are tested by random atom shifts and global deformations. The calculated energy also indicates that the Cr23C6 is more stable than Mn23C6.

  • 237.
    Xie, Jiaying
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Teng, Li-Dong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Chen, Nan-Xian
    Thermodynamic studies of the Fe-Cr-C-N system by EMF measurements2007In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Metallurgical and materials transaction B, Vol. 38, no 1, p. 93-100Article in journal (Refereed)
    Abstract [en]

    In this work, the Fe-Cr-C-N alloys were synthesized by nitriding the Fe, Cr, and C powder mixtures at 1573 K in the N-2 gas (101 325 Pa). The nitrogen content and phase relationships at 1173 K in the alloys were investigated by the use of an equilibration technique. The thermodynamic activities of chromium in the alloys were studied using the solid-state galvanic cell method with CaF2 as the solid electrolyte in the temperature range 973 to 1173 K in an atmosphere of N-2 gas (101 325 Pa). The activities of chromium in the Fe-Cr-C-N alloys were calculated and compared with those of the corresponding Fe-Cr-C ternary alloys with pure bcc-Cr as standard state. X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods were used to identify the equilibrium phases and microstructures of the investigated alloys. The experimental results show that a Cr2N-based nitride was formed during the nitriding procedure in the alloys. The nitrogen content in the alloys decreases with the decreasing chromium content, as well as the increasing temperature. The addition of nitrogen to the ternary Fe-Cr-C alloy was found to have a strong negative impact on the Cr activity in the Fe-Cr-C-N system.

  • 238.
    Xie, Jiaying
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Teng, Li-Dong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Chen, N-X
    Thermodynamic investigations of the Cr-Fe-N system with solid-state galvanic cell methodIn: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Metallurgical and materials transaction AArticle in journal (Refereed)
  • 239.
    Yang, Yang
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Equilibrium phase relationships in the CaO-MgO-SiO2-Cr2O3 slags2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Download full text (pdf)
    Equilibrium phase relationships in the CaO-MgO-SiO2-Cr2O3 slags
  • 240.
    Yang, Yang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Experimental Study of Phase Equilibria in CaO-SiO2-MgO-Al2O3-V2O3 Slags2014In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, no 12, p. 1588-1596Article in journal (Refereed)
    Abstract [en]

    Thermodynamic data with regard to slags containing vanadium oxide are scarce and scattered. In the present study, the classic gas-slag equilibrium technique has been adopted to investigate the phase relationships in the CaO-SiO2-MgO-Al2O3-V2O3 slags. The phase equilibria in the slag systems in the temperature range of 1773-1823K (1500-1550 degrees C) at oxygen partial pressures of 10(-5) Pa and 0.21 x 10(5) Pa were characterized. CaVO3 was precipitated in samples with basicity 1.5 and 1.8 treated in air at 1773 K (1550 degrees C) while all vanadium was dissolved in equilibrium phases in samples treated at oxygen partial pressure of 10(-5) Pa. Vanadium distribution between the slags and solid Pt and phase compositions were analyzed using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and X-ray diffractomer (XRD) techniques. The effects of temperature, oxygen partial pressure, and slag basicity on the phase compositions in the slags are presented. Activities of VO1.5 were also calculated using the value of vanadium activity in the Pt-V alloy.

  • 241.
    Yang, Yang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Kinetic Studies on Evaporation of Liquid Vanadium Oxide, VO (x) (Where x=4 or 5)2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 6, p. 1684-1691Article in journal (Refereed)
    Abstract [en]

    As part of the Swedish National Eco-steel project, the present work was carried out with a view to study the evaporation of vanadium as V2O5 with a focus on the health hazards. The evaporation rate was followed by monitoring the mass loss from liquid V2O5 melts by thermogravimetric analysis (TGA) in the temperature range 1723 K to 1873 K (1450 A degrees C to 1600 A degrees C). The studies were carried out under three different oxygen partial pressures, viz, oxygen, air, or CO2. The experiments were carried out in the isothermal mode. The Arrhenius activation energies for the evaporation reaction in different atmospheres were calculated from the results. A mathematical model was developed in order to describe the kinetics of the evaporation process. Good agreement could be achieved between the mathematical model and the experimental results. Evaporation coefficients and enthalpies in different atmospheres were also estimated. The present results may also have implications in recovering vanadium values from different vanadium sources.

2345 201 - 241 of 241
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf