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  • 1. Abbasalizadeh, A.
    et al.
    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.
    Sietsma, J.
    Yang, Y.
    Rare Earth Extraction from NdFeB Magnets and Rare Earth Oxides Using Aluminum Chloride/Fluoride Molten Salts2015In: Rare Earths Industry: Technological, Economic, and Environmental Implications, Elsevier, 2015, p. 357-373Chapter in book (Other academic)
    Abstract [en]

    In the current research, the feasibility of the recovery of neodymium and dysprosium from spent NdFeB magnets (about 6wt% Dy) was investigated using molten salt processes. The salt bath consisted of a eutectic composition of an NaCl-KCl-LiCl mixture. To enable the efficient dissolution of metal in the molten salt phase, AlCl3 was used as a chlorinating agent. Iron-free electrodeposition was carried out successfully. Energy-dispersive spectroscopic analysis of the electrodeposit revealed that co-deposition of the dysprosium occurs along with neodymium at the cathode. The process shows that this method is well suited for recovering rare earth metals from magnetic scrap containing these metals.Furthermore, the setup design for recovery of neodymium and dysprosium from their oxides was investigated with regard to previous studies on the neodymium magnets. The stability of different fluoride and chloride salts was studied by means of thermodynamic calculation. Aluminum fluoride-based molten salt systems were studied in detail as the electrolyte for electrochemical extraction of rare earth oxides into rare earth metal elements with Al.

  • 2.
    Abbasalizadeh, Aida
    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.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Sridhar, Seetharaman
    Grinder, Olle
    Izumi, Yukari
    Barati, Mansoor
    Highlights of the Salt Extraction Process2013In: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 65, no 11, p. 1552-1558Article in journal (Refereed)
    Abstract [en]

    This article presents the salient features of a new process for the recovery of metal values from secondary sources and waste materials such as slag and flue dusts. It is also feasible in extracting metals such as nickel and cobalt from ores that normally are difficult to enrich and process metallurgically. The salt extraction process is based on extraction of the metals from the raw materials by a molten salt bath consisting of NaCl, LiCl, and KCl corresponding to the eutectic composition with AlCl3 as the chlorinating agent. The process is operated in the temperature range 973 K (700 degrees C) to 1173 K (900 degrees C). The process was shown to be successful in extracting Cr and Fe from electric arc furnace (EAF) slag. Electrolytic copper could be produced from copper concentrate based on chalcopyrite in a single step. Conducting the process in oxygen-free atmosphere, sulfur could be captured in the elemental form. The method proved to be successful in extracting lead from spent cathode ray tubes. In order to prevent the loss of AlCl3 in the vapor form and also chlorine gas emission at the cathode during the electrolysis, liquid aluminum was used. The process was shown to be successful in extracting Nd and Dy from magnetic scrap. The method is a highly promising process route for the recovery of strategic metals. It also has the added advantage of being environmentally friendly.

  • 3.
    Abbasalizadeh, Aida
    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, S.
    Dysprosium extraction using molten salt process2014In: Rare metal technology 2014: proceedings of a symposium sponsored by The Minerals, Metals & Materials Society (TMS) held during TMS 2014, 143rd Annual Meeting & Exhibition, February 16-20, 2014, San Diego Convention Center, San Diego, California, USA, 2014, p. 207-208Conference paper (Refereed)
  • 4.
    Abbasalizadeh, Aida
    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.
    Sridhar, S.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Neodymium extraction using salt extraction process2015In: Transactions of the Institution of Mining and Metallurgy Section C - Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, E-ISSN 1743-2855, Vol. 124, no 4, p. 191-198Article in journal (Refereed)
    Abstract [en]

    The present paper deals with the feasibility of the neodymium recovery from spent Nd-Fe-B magnets using molten salt electrodeposition method. The salt bath consisted of a mixture of LiCl- KCl-NaCl corresponding to the eutectic composition. The experimental set-up with its salient features is presented. AlCl3 was used as flux and graphite rods dipped in the salt bath served as electrodes. The voltage for the electrolysis was chosen on the basis of the decomposition potential of NdCl3. The reaction sequence can be described as Iron-free neodymium deposition could be carried out successfully. In view of the proximity of the electrode potentials, the co-deposition of the aluminium and neodymium was observed to occur at the cathode, as revealed by SEM/EDS and XRD analyses of the electrodeposit.

  • 5.
    Albertsson, Galina
    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.
    Björkman, Bo
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Engström, Fredrik
    Effect of Low Oxygen Partial Pressure on the Chromium Partition in CaO-MgO-SiO2-Cr2O3-Al2O3 Synthetic Slag at Elevated Temperatures2013In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, no 7, p. 670-679Article in journal (Refereed)
    Abstract [en]

    The objective of the present work is to get an understanding of the impact of Al2O3 addition on the phase relationships in the CaO-MgO-Al2O3-SiO2-Cr2O3 slags at low oxygen partial pressures (P-O2 = 10(-4) Pa), with a view to control the precipitation of Cr-spinel in the slag. The equilibrium phases in CaO-MgO-Al2O3-SiO2-Cr2O3 slag system in the range on 1673-1873 K have been investigated. The compositions close to the industrial slag systems were chosen. The Cr2O3 content was fixed at 6 wt% and MgO at 8 wt%. Al2O3 contents in the slag were varied in the range of 3-12 wt%. The basicity (CaO/SiO2) of slag was set to 1.6. Gas/slag equilibrium technique was adopted. The samples were heated to 1873 K and soaked at this temperature for 24 h. The samples were then slow cooled to 1673 K and equilibrated for an additional 24 h. The oxygen partial pressure was kept at 10(-4) Pa. A gas mixture of CO/CO2 was used to control the oxygen partial pressure. After the equilibration, the samples were quenched in water. The chromium distribution and phase compositions in the quenched slags were studied using SEM-WDS and XRD techniques. The results were compared with the phase equilibrium calculations obtained from FACTSAGE software and the samples equilibrated in air. The size of spinel crystals increased drastically after slow cooling followed by annealing compared to samples being quenched after soaking at 1873 K. It was also found that low oxygen partial pressure had a strong impact on chromium partition. The amount of spinel phase increases with increased Al2O3 content.

  • 6.
    Chychko, Andrei
    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.
    Nzotta, M.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Fe2MoO4 as a precursor material for Mo alloying in steel: (Part II): Upscaling test2011In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 82, no 8, p. 886-897Article in journal (Refereed)
    Abstract [en]

    The Mo yield when using three different alloying mixtures (MoO3 +C; MoO3 +C + FeOx; and MoO3+ C + CaO) was tested both in laboratory experiments (16 g and 0.5 kg scale) and industrial trials (3 ton scale). The alloying is based on in-situ formation of compounds of Mo in the mixtures from molybdenite concentrate with industrial grade Fe 2O3. Thermogravimetry (TGA) and X-ray diffraction (XRD) analyses were performed to identify the reduction steps and final products of the alloying mixtures. At least two steps of mass change were discovered during the reduction of all tested mixtures by carbon. The Mo yield for MoO3 + C mixture is 93% which was confirmed by both laboratory and industrial experiments. The Mo yield for MoO3 + C + CaO mixture is around 92% during 16 g scale laboratory and 3 ton scale industrial tests. The best results were obtained in the case of the mixture which contained FeOx, MoO3 and C, resulting in the Mo yield up to 98% at all the experiment scale levels. It was found that the combination of both lower evaporation and fast reduction by carbon of the mixture along with further dissolution in steel are necessary to provide high Mo yield during steel alloying. The calculated mass balance of 3 ton trial heats showed that only a small part of initial Mo amount (8-13 ppm) has gone into slag. Copyright

  • 7.
    Chychko, Andrei
    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.
    Nzotta, M.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Synthesis and characterization of Fe2MoO4 as a precursor material for Mo alloying in steel2011In: Steel Research International, ISSN 1611-3683, Vol. 82, no 3, p. 269-276Article in journal (Refereed)
    Abstract [en]

    Iron molybdate (Fe2MoO4) has been studied as a new potential precursor for Mo additions in high alloy steel processing. Fe2MoO4 was synthesized by high temperature reactions between MoO3, FeOx and carbon by holding the mixture first for 23 hours at 873K and then for 16 hours at 1373 K. The Fe2MoO4 syntheses were carried out with pure reagents as well as commercial grade materials supplied by steel industry. A thermodynamic analysis of the stabilities of the various phases in the Fe-Mo-O-C quaternary was carried out. The synthesis processes, leading to the Fe2MoO4 formation from the precursors and further reduction by carbon were studied with the aid of thermogravimetric analysis (TGA), high-temperature X-ray diffraction (HT-XRD) and evolved gas analysis by gas chromatography (GC). The maximum temperature in the case of all the experiments was 1373 K. It was found that the reactions between the precursor components start already above 873 K. The precursor mixture from commercial grade materials offers an economically advantageous process route with high Mo yield in steel.

  • 8.
    Chychko, Andrei
    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.
    ENERGY SAVING EFFECT OF SLAG FOAMING BY CARBONATE ADDITIONS IN EAF PROCESS2010In: ARCH METALL MATER, ISSN 1733-3490, Vol. 55, no 4, p. 1089-1095Article in journal (Refereed)
    Abstract [en]

    Slag foaming has been studied systematically for more than 50 years. The main reason for such interest is a big number of benefits of slag foaming technology in steelmaking, especially for the process in an electric arc furnaces (EAF). There are 2 types of reactions which can be used for slag foaming. The most famous one is the carbon oxidation by oxygen dissolved in metal. Another type of slag foaming reactions is a decomposition of carbonates or other substances, which can produce gas at high temperature. However, it can be concluded that the slag foaming with carbonates is not usual in steelmaking practice. The purpose of the present work is to study the energy effect of slag foaming caused by carbonates decomposition.

  • 9.
    Chychko, Andrei
    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
    Foaming in Electric Arc Furnace: Part II: Foaming visualization and Comparison with Plant trials2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 5, p. 1078-1085Article in journal (Refereed)
    Abstract [en]

    The kinetics of slag foaming by limestone particles was studied at 1773 K (1500 A degrees C) with the aid of an X-ray imaging system. Two models were implemented to describe the decrease in foam height with the time on the basis of the lowering of the average temperature and CaO shell formation during decomposition reaction. The energy impact of carbonate additions was studied on an industrial scale in a 100-ton electric arc furnace (EAF). It was found that, in the case of the addition of carbonates after the scrap is completely molten, the heat effects for limestone and dolomite (2255 and 2264 kJ/kg, respectively) were only 70 pct from theoretical values. Comparing these values with similar additions during the scrap melting stage shows that the energy requirements in the case of carbonate additions to steel bath are much smaller. It was found from the trial heats with dolomite addition to the steel bath that the partial substitution of lime by raw dolomite can be made without an increase in energy consumption.

  • 10.
    Chychko, Andrei
    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.
    MoO3 Evaporation Studies from Binary Systems towards Choice of Mo Precursors in EAF2010In: Steel Research International, ISSN 1611-3683, Vol. 81, no 9, p. 784-791Article in journal (Refereed)
    Abstract [en]

    The evaporation rate of molybdenum oxide from mixtures with CaO or MgO was studied in the temperature range 300-1573 K. The investigations were carried out using high temperature X-ray diffraction and thermogravimetry. Further, additions of these precursors to molten steel in the laboratory scale and the Mo yield achieved were determined. The X-ray studies show that the calcium molybdate is formed from the oxide mixture in the temperature interval 773-873K, which precedes the beginning of evaporation of MoO3. Results of thermogravimetric studies with mixtures CaO and MgO with MoO3 as well as the compounds CaMoO4 and MgMoO4 confirm the above results. Addition of various molybdenum precursors, viz, the mixtures of carbon with pure MoO3, CaMoO4 and MgMoO4, as well as oxide mixtures (CaO + MoO3, MgO + MoO3) show that the highest yield was observed for CaMoO4 + C and MoO3 + C mixtures, while MgO + C + MoO3 mixture showed much lower yield.

  • 11. Gupta, G. S.
    et al.
    Sarkar, S.
    Chychko, Andrei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Eramet group, Sweden.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Nzotta, M.
    Seetharaman, S.
    Process Concept for Scaling-Up and Plant Studies2014In: Treatise on Process Metallurgy, Elsevier, 2014, Vol. 3, p. 1100-1144Chapter in book (Refereed)
    Abstract [en]

    This article deals with the concept of scaling -up and scaling -down of industrial processes which is an essential requirement to understand and optimize the process. The concept has been described based on physical modeling of the process at laboratory scale using various techniques. The concept of physical modeling has been followed by two industrial examples where it has been used successfully. First example deals about scaling down of an industrial process to a laboratory scale to understand the raceway formation phenomena in an iron making blast furnace. In second example development of a new process for Mo addition in EAF practice is described. The development starts from theoretical backgrounds for the process of Mo addition improvements and then follows with number of experimental trials starting from 16g laboratory scale furnace to 70 ton industrial EAF.

  • 12. Hu, X.
    et al.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Wang, H.
    Sundqvist Ökvist, L.
    Yang, Q.
    Björkman, B.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Carbothermic reduction of synthetic chromite with/without the addition of iron powder2016In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 56, no 12, p. 2147-2155Article in journal (Refereed)
    Abstract [en]

    Carbothermic reduction of chromite is an important industrial process for extracting chromium from the chromite. To have a better understanding of the effect of iron on the carbothermic reduction of chromite, the reduction of synthetic chromite (FeCr2O4) by graphite with/without the addition of iron powder was investigated in this paper by Thermogravimetric Analysis (TGA) in argon atmosphere. The fractional reduced samples were examined by SEM/EDS and XRD analysis, and the reduction process was thermodynamically and kinetically evaluated. The experimental results show that the iron powder addition enhances the reduction of FeCr2O4 and this effect increases when increased amounts of iron powder are added. This phenomenon is attributed to the in situ dissolution of chromium into the iron and mixed carbide (Cr,Fe)7C3, which can decrease the activity of the nascent chromium formed by the reduction of the FeCr2O4. The experimental results indicate that the reduction of FeCr2O4 with up to 80 wt.% iron powder addition is likely to be a single-step process and the kinetic analysis suggests that the reduction reaction is likely to be either (a) chemical reaction at the surface of FeCr2O4 or (b) diffusional dissolution of the product (FeCr2) into the iron/alloy particles or the mixed control of (a) and (b).

  • 13.
    Hu, X.
    et al.
    KTH.
    Wang, H.
    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.
    Direct chromium alloying by chromite ore with the presence of metallic iron2013In: Journal of Mining and Metallurgy, Section B: Metallurgy, ISSN 1450-5339, Vol. 49, no 2, p. 207-215Article in journal (Refereed)
    Abstract [en]

    Direct chromium alloying by chromite ore in EAF operation is a promising process in stainless steel production, which has the advantage of resource-saving, energy-saving, and environment-friendly. In the present investigation, iron, carbon, and chromite ore mixture (Fe+C+FeCr2O4) were chosen as the precursor for direct chromium alloying. Thermogravimetric Analysis (TGA) experiments were carried out to investigate the effect of iron content on the reduction kinetics, and the results show that the presence of metallic iron in the precursor will increase the reduction rate of chromite. Up-scaling experiments (100 g and 500 g scale) have been carried out in the induction furnace to further test the effectiveness of using industrial chromite ore for direct chromium alloying. The induction furnace tests confirmed the necessity of adjusting composition of the slags to ensure high yield of chromium in the final products; and chromium yield can reach 90%.

  • 14.
    Jelkina Albertsson, Galina
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Engström, Fredrik
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Effect of the Heat Treatment on the Chromium Partition in Cr-Containing Industrial and Synthetic Slags2014In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, no 10, p. 1418-1431Article in journal (Refereed)
    Abstract [en]

    In the present work, the effects of the slag composition and heat-treatment conditions on the phase relationships in a number of Cr-containing industrial and synthetic slags were investigated with a view to control the precipitation of Cr-spinel in the slag phase. Gas/slag equilibrium technique was used for the chromium partition and the phase relationship study. The phase relationships in synthetic slags and industrial EAF slags supplied by Swedish steelmaking plants have been investigated experimentally in the temperature range of 1473-1873 K. The slags were re-melted, slow-cooled to, and soaked at targeted temperatures in controlled atmosphere. Two different heat-treatment sequences were used in the present experiments. The oxygen partial pressure (p(O2) = 10(-3) Pa) was maintained by a suitable mixture of CO and CO2 gases. Phases present and their compositions in the quenched slags were studied using X-ray diffractometry (XRD) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The chromium content in the phases present was analyzed using wavelength-dispersive spectrometer (WDS). Chromium partition was found to depend on the heat-treatment temperature.

  • 15.
    Jelkina Albertsson, Galina
    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.
    Björkman, Bo
    Divison of Extractive Metallurgy, Luleå University of Technology, Luleå, Sweden.
    Effect of basicity on chromium partition in CaO-MgO-SiO2-Cr 2O3 synthetic slag at 1873 K2014In: Transactions of the Institution of Mining and Metallurgy Section C - Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, E-ISSN 1743-2855, Vol. 123, no 2, p. 116-122Article in journal (Refereed)
    Abstract [en]

    The objective of the present work is to get an understanding of the phase relationships in the CaO-MgO-SiO2-Cr2O3 system with a view to control the precipitation of Cr-spinel in the slag phase. The equilibrium phases in CaO-MgO-SiO2-Cr2O3 slag system at 1873 K (1600°C) have been investigated experimentally and compared with the results from thermodynamic calculations. The Cr2O 3 and MgO contents in the slag were fixed at 6 and 8 wt-% respectively. The basicity (CaO/SiO2) of slag was varied in the range 1·0-2·0. A gas/slag equilibrium technique was adopted to synthesise the slag at a high temperature in air. The samples were heated to and soaked at 1873 K (1600°C) for 24 h in order to achieve the equilibrium state and subsequently quenched in water. The chromium distribution and phase compositions in the quenched slag were studied using scanning electron microscope wavelength dispersive spectroscopy and X-ray diffraction techniques. FactSage software was used for the phase equilibrium calculations. The experimental results obtained from the present work were compared with the calculation results from FactSage software. It was found that the spinel formation at 1873 K (1600°C) is favoured in the slag basicity range 1·0-1·4.

  • 16.
    Jelkina Albertsson, Galina
    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.
    Engström, Fredrik
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Effect of the heat treatment on the chromium partition in CaO-MgO-SiO2-Cr2O3 synthetic slags2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 6, p. 1586-1597Article in journal (Refereed)
    Abstract [en]

    Mg-spinel phase is known to be important for control of Cr leaching from Cr-containing slags. The objective of the present study is to get an understanding of the phase relationships in the CaO-MgO-SiO2-Cr2O3 system with a view to control the precipitation of Cr-spinel in the slag phase. The equilibrium phases in CaO-MgO-SiO2-Cr2O3 slag system in the range of 1673 K to 1873 K (1400 A degrees C to 1600 A degrees C) have been investigated experimentally and compared with the results from thermodynamic calculations. The slag compositions close to the industrial slag systems were chosen. The Cr2O3 and MgO contents in the slag were fixed to be 6 and 8 wt pct, respectively. The basicity (CaO/SiO2) of the slag was varied in the range of 1.0 to 2.0. The slags were synthesized at a pre-determined oxygen partial pressure (10(-4)) or air (2.13 x 10(4) Pa) at a temperature above the liquidus temperature. The samples were then soaked at targeted temperatures for 24 hours in controlled atmosphere in order to achieve the equilibrium state before quenching in water. Four different heat-treatment regimes (defined as Ia, Ib, II.a and II.b) in Section II-D) were used in the present experiments. The lower oxygen partial pressure was maintained by a suitable mixture of CO and CO2 gases. Phases present and their compositions in the quenched slags were studied using scanning electron microscopy coupled with energy-dispersive spectroscopy and X-ray diffraction techniques. The chromium content in the phases present was analyzed using wavelength-dispersive spectrometer. The experimental results obtained are compared with the calculation results from Factsage software. The size of spinel crystals increased drastically after slow-cooling from 1873 K (1600 A degrees C) followed by annealing at 1673 K (1400 A degrees C) for 24 hours (heating regimes II) compared to samples being quenched directly after soaking at 1873 K (1600 A degrees C) (heating regime I.a). It was found that the amount of foreign elements in the spinel phase, and other phases decreased after soaking at oxygen partial pressure of 10(-4) Pa resulting in phases with less defects and foreign oxide contents compared to those treated in air. The size of spinel crystals was found to be larger in samples with lower basicity.

  • 17.
    Jönsson, Pär
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Matsushita, Taishi
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Sundberg, Sven
    The Seetharaman Seminar June 14-15, 2010 in Stockholm, Sweden2012In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 31, no 3, p. 193-193Article in journal (Other academic)
  • 18. Khalaghi, B.
    et al.
    Kvalheim, E.
    Tokushige, M.
    Haarberg, G. 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.
    Electrochemical behaviour of dissolved iron chloride in KCl+LiCl+NaCl melt at 550°C2014In: ECS Transactions, ISSN 1938-5862, E-ISSN 1938-6737, Vol. 64, no 4, p. 301-310Article in journal (Refereed)
    Abstract [en]

    An electrochemical study of iron was carried out in KCl+LiCl+NaCl melt at 550C using a glassy carbon working electrode. Cyclic voltammetry showed that the Fe(II)/Fe(0) electron exchange is a soluble/insoluble reversible process. The diffusion coefficient of Fe(II) was calculated using cyclic voltammetry; 1.4×10-5 cm2 s-1. For the Fe(II)/Fe(III) red/ox reaction, analysis of the voltammograms suggests that the process is not reversible and is coupled with a chemical reaction. The stability of FeCl<inf>3</inf> and the effect of equilibrium between FeCl<inf>3</inf> and FeCl<inf>2</inf> are also briefly discussed.

  • 19.
    Li, Peng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Guo, Min
    Zhang, 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.
    Leaching process investigation of secondary aluminium dross: Investigation of AlN hydrolysis behaviour in NaCl solution2012In: Transactions of the Institutions of Mining and Metallurgy, Section C: Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, Vol. 121, p. 140-146Article in journal (Refereed)
    Abstract [en]

    The AlN hydrolysis behaviour in NaCl solution was investigated by immersing AlN powder in deionised water, 0.3 mol L -1 NaCl aq and 0.6 mol L -1 NaCl aq at 291 K respectively. The pH value of the suspension was monitored continuously for the first 4 days, and the amount of NH 3 formed within 10 days period was measured by water quality-determination of ammonium- distillation and titration method. The characterisation of the products after hydrolysis was carried out using X-ray diffraction, SEM and TEM analyses. It was shown that the hydrolysis process included a slow reaction period involving the dissolution of aluminium hydroxide layer around raw AlN particle, followed by the precipitation of aluminium hydroxide gel and the crystallisation of boehmite, bayerite and gibbsite. The effects of sodium chloride concentration on the hydrolysis behaviour are presented.

  • 20.
    Li, Peng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Guo, Min
    Zhang, 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.
    Leaching Process Investigation of Secondary Aluminum Dross: The Effect of CO 2 on Leaching Process of Salt Cake from Aluminum Remelting Process2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 5, p. 1220-1230Article in journal (Refereed)
    Abstract [en]

    For the recycling/disposal of aluminum dross/salt cake from aluminum remelting, aqueous leaching offers an interesting economic process route. One major obstacle is the reaction between the AlN present in the dross and the aqueous phase, which can lead to the emission of NH 3 gas, posing a serious environmental problem. In the current work, a leaching process using CO 2-saturated water is attempted with a view to absorb the ammonia formed in situ. The current results show that at a solid-to-liquid ratio of 1:20 and 3 hours at 291 K (18 °C), the extraction of Na and K from the dross could be kept as high as 95.6 pct and 95.9 pct respectively. At the same time, with continuous CO 2 bubbling, the mass of escaping NH 3 gas decreased from 0.25 mg in pure water down to &lt;0.006 mg, indicating effective absorption of ammonia by carbonized water. Furthermore, the results in the case of the leaching experiments with synthetic AlN show that the introduction of CO 2 causes hindrance to the hydrolysis of AlN. The plausible mechanisms for the observed phenomena are discussed. The concept of the leaching of the salt cake by carbonated water and the consequent retention of AlN in the leach residue opens up a promising route toward an environment-friendly recycling process for the salt cake viz. recovery of the salts, utilization of CO 2, and further processing of the dross residue, toward the synthesis of AlON from the leach residues.

  • 21.
    Li, Peng
    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, Materials Process Science.
    Guo, Min
    Zhang, Mei
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Oxidation Kinetics of AlN Under CO2 Atmosphere2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 2, p. 406-412Article in journal (Refereed)
    Abstract [en]

    The oxidation kinetics of AlN powder in CO2 atmosphere was investigated using thermogravimetric analysis. The experiments were carried out in the isothermal mode at different flow rates of CO2, 20 mL/min, 40 mL/min, 150 mL/min, and 265 mL/min. The results showed that the oxidation rate was affected by temperature as well as the flow rate of CO2. Based on the experimental data, a kinetic model for predicting the oxidation behavior of AlN powder has been developed, which could simulate both the chemical reaction and diffusion -controlling periods as a function of temperature and carbon dioxide concentration.

  • 22.
    Li, Peng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Zhang, Mei
    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.
    Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part I: Kinetics2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 1, p. 210-219Article in journal (Refereed)
    Abstract [en]

    The oxidation behaviors of composites SiAlON/MgAlON phases (beta-SiAlON, 15R-SiAlON and MgAlON) synthesized from the residue during the leaching treatment of salt cake and corresponding synthetic samples were investigated in air by thermogravimetric measurements. Combined kinetics, viz. linear law + arctan law + parabolic law, are used to describe the kinetics of oxidation in isothermal mode. The oxidation studies reveal the effects of impurities, namely, Fe2O3 and CaO, present in the salt cake residue. The addition of Fe2O3 results in a lower activation energy and more aggressive oxidation. The addition of CaO caused the shrinkage during the synthesis and liquid formation during the oxidation above 1673 K (1400 A degrees C). The impurities of CaO and Fe2O3 in the leaching residue can result in an aggressive oxidation at low temperature and a protective oxidation at temperatures above the eutectic point.

  • 23.
    Li, Peng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Zhang, Mei
    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.
    Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part II: Phase Evolution2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 1, p. 220-232Article in journal (Refereed)
    Abstract [en]

    The oxidation behavior of composite SiAlON/MgAlON phases, synthesized from the leaching residue after the aqueous treatment of salt cake from aluminum remelting, is compared with the oxidation of corresponding synthetic samples. The samples were subjected to oxidation under air as the oxidant atmosphere in the temperature range of 1373 K to 1773 K (1100 A degrees C to 1500 A degrees C). The phases present were analyzed by scanning electron microscopy (SEM)-electron-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) to arrive at the evolution of the various phases formed during oxidation. From the experimental results, especially by the characterization of the oxidation products, the mechanism of the oxidation reaction was deduced as follows: With the progress of oxidation, the composition of the material being oxidized moved toward the Al2O3-rich corner of MgO-Al2O3-SiO2 and CaO-MgO-Al2O3-SiO2 phase diagrams relevant to the SiAlON/MgAlON composite. At lower temperatures, the addition of Fe2O3 and CaO facilitated the formation of cordierite and anorthite, respectively. With increasing temperature, islands of silicate melt were formed dissolving these oxides, with the liquidus temperature getting lowered as a consequence. The liquid phase formed engulfed the adjacent solid phases providing strong mobility for the cations and enabling the crystal growth. As a result, intermediate products, i.e., cordierite, anorthite, and spinel, which were formed earlier during oxidation, are found to get dissolved in the liquid phase.

  • 24.
    Li, Peng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Zhang, Mei
    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.
    Recycling of Aluminum Salt Cake: Utilization of Evolved Ammonia2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 1, p. 16-19Article in journal (Refereed)
    Abstract [en]

    The communication presents an extension of the leaching process of the salt cake earlier developed by the present authors. The process describes the investigations in capturing the ammonia gas evolved by hydrolysis of AlN during aqueous leaching at 373 K (100 A degrees C) by CO2-saturated water. The product, i.e., ammonium bicarbonate which is free of chlorides, is a value-added product and can find application in the fertilizer industry. The present method has the added advantage of fixing CO2 as well.

  • 25.
    Seetharaman, Seshadri
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Andersson, G.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Retainment, Recovery and Recycling: A Swedish Success Story of ECO-Steelmaking2013In: Transactions of the Indian Institute of Metals, ISSN 0972-2815, Vol. 66, no 5-6, p. 567-575Article in journal (Refereed)
    Abstract [en]

    With a view to optimize the environmental aspects of steelmaking, the Swedish Steel Producers Association took the initiative to start a national project on ECO-steelmaking with financial support from Swedish Foundation for Strategic Environmental Research. The Division of Materials Process Science at the Royal Institute of Technology has an important part of the project, viz. "Retention, Recovery and Recycling", with emphasis on the retention of metal values in the steel bath without loss to the slag or gas phases, to recover the metal values that are lost to the slag phase by the development of new or optimized process concepts and aim at a total recycling of the metal values as well as the slag components within or outside the steel sector. The present paper describes the optimization of existing process concepts as well as evolving newer concepts to meet the above project goals. The use of CO2-O-2-Ar gas mixtures for the decarburization of high-alloyed steels, development of a low cost precursor for the addition of molybdenum to steel in EAF, direct alloying in EAF are some of the concepts initiated in the present work. Successful recovery of iron and manganese values by oxidation of the slag and separation of the magnetite or manganese ferrate by electromagnetic separation formed part of the recovery part. As part of the project, a salt extraction process was developed by which the metal values in slags could be extracted into a chloride phase followed by electrolysis in fused chloride medium. This method was found to be successful in the recovery of metal values from slags. This process could be extended to the recovery of a variety of metal values from a variety of secondary sources. The salient features of the process designs and the results are presented in this paper.

  • 26.
    Seetharaman, Seshadri
    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.
    Hayashi, Miyuki
    Wang, Lijun
    Understanding the Properties of Slags2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 1, p. 1-8Article, review/survey (Refereed)
    Abstract [en]

    Understanding of the properties of slags is a pre-requisite in optimizing their functions towards the making and refining of steel. Important contributions towards this objective have been made over the past half a century, in different parts of the world, especially in USA, UK, Germany and most of all in Japan. Knowledge of the slag properties enables in understanding the slag structure as well. The present review paper summarizes the contributions made in this field by the Division of Materials Process Science, Royal Institute of Technology, Stockholm, Sweden. The paper deals with the measurement and modeling of (a) thermochemical properties of slags, (b) thermophysical properties and (c) inter-property correlations. Some important contributions during recent years, such as the determination of the valence states of Cr and V in slags, wetting characteristics related to hot-metal desulphurization, diffusion of sulphide ions in slags, partition of phosphorus between slag and metal phases and studies on process phenomena such as foaming are highlighted. The research work has led to the evolution of a new basicity concept. Dynamic physical property measurements are pointed out to be an experimental tool towards understanding of reaction mechanisms. Developments with respect to slag/metal interfacial phenomena, viz, the concept of surface velocity and surface viscosity and quantification of these properties are presented.

  • 27.
    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.

  • 28.
    Teng, Lidong
    KTH, Superseded Departments, Materials Science and Engineering.
    Thermodynamic investigations of transition metal systems containing coabon and nitrogen2004Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    In view of the important applications of carbides and carbo-nitrides of transition metals in the heat-resistant and hard materials industries, the thermodynamic activities of Cr and Mn in the Cr-C, Fe-Cr-C, Mn-Ni-C and Mn-Ni-C-N systems have been studied in the present work by the use of the galvanic cell technique. CaF2single crystals were used as the solid electrolyte. The phase relationships in selected regions of the systems in question were investigated by the use of the equilibration technique. The phase compositions and microstructures of the alloys were analysed by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM).

    In the Cr-C system, the Gibbs energy of formation of Cr3C2 were obtained from ElectroMotive Force (EMF) measurements conducted in the temperature range 950-1150 K. The values of the enthalpy of formation of Cr3C2 were evaluated by the third-law method. The ground-state energy of the hypothetic end-member compound CrC3, in the bcc structure at 0 K, was calculated by use of the Ab-initio method. Based on the obtained results the Cr-C system was reassessed by use of the CALPHAD approach.

    In the Fe-Cr-C system, 16 different alloys were quenched at 1223 K and their equilibrium phases identified by XRD. The experimental results show that the substitution of Cr by Fe in the (Cr,Fe)7C3 carbide changes the lattice parameters of the phase. A slight decrease of the lattice parameters with an increase in the Fe content was established. The lattice parameters of the γ-phase in the Fe-Cr solid solution did also show a decrease with an increase of the Fe content. The activities of chromium in Fe-Cr-C alloys were investigated in the temperature range 940-1155 K. The activity of chromium decreases with an increase in the Fe content when the ratio of C/(Cr+C) was constant. It was also established that the activity of chromium decreases with an increase of the carbon content when the iron content was constant. The experimental results obtained were compared with the data calculated by use of the Thermo-Calc software.

    In the Mn-Ni-C system the phase relationships were investigated at 1073 K as well as at 1223 K. The experimental results obtained showed that the site fraction of Ni in the metallic sublattice of the carbides M23C6, M7C3 and M5C2 (M=Mn and Ni) was quite low (approximately 2~3 percent). The activities of manganese in Mn-Ni-C alloys were investigated in the temperature range 940-1165 K. The three-phase region γ/M7C3/graphite was partly constructed at 1073 K.

    In the Mn-Ni-C-N system, nitrogen was introduced into Mn-Ni-C alloys by equilibrating with N2 gas. It was established that the solubility of nitrogen in the investigated alloys was effected by the carbon content, and that a (Mn,Ni)4(N,C) compound was formed in the nitrided alloys. EMF measurements were performed on Mn-Ni-C-N alloys in the temperature interval 940-1127 K. The addition of nitrogen to Mn-Ni-C alloys was found to decrease the activity of manganese. The negative effect of nitrogen on the activity of manganese was found to decrease as the carbon content increased.

    Keywords: Thermodynamic activity; Galvanic cell technique; Transition metal carbides; Transition metal nitrides; Phase equilibrium; Thermodynamics; Differential thermal analysis; Scanning electron microscopy; Transmission electron microscopy; Ab-initio calculations; CALPHAD approach;

  • 29.
    Teng, Lidong
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Aune, Ragnhild E.
    KTH, Superseded Departments, Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    Thermodynamic Studies of Cr3C2 and Reassessment of the Cr-C System2004Conference paper (Refereed)
  • 30.
    Teng, Lidong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Aune, Ragnhild
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Li, W.C.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Phase relationships and thermodynamic properties in the Mn-Ni-C system2005In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 36, no 10, p. 2585-2593Article in journal (Refereed)
    Abstract [en]

    In the present work, phase relationships in selected phase regions of the Mn-Ni-C system have been investigated at 1073 and 1223 K by use of an equilibration technique. Alloys of Mn-Ni-C were prepared from pure Mn, Ni, and C powders by the powder metallurgy method. The phase identification of the heat-treated samples was carried out by scanning electron microscope (SEM) and transmission electron microscope (TEM). The main phase compositions of the alloys have been analyzed by X-ray diffraction (XRD). The experimental results show that the site fraction of Ni in the metallic sublattice of the carbides M23C6, M7C3, and M5C2 is quite low and the value is around 0.02 to 0.03. The thermodynamic activities of manganese in 16 different Mn-Ni-C alloys have been studied by solid-state galvanic cell technique with single-crystal CaF2 as the solid electrolyte in the temperature range 940 to 1165 K. The results are discussed in light of the available thermochemical information.

  • 31.
    Teng, Lidong
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Aune, Ragnhild
    KTH, Superseded Departments, Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    Study of Mn activities in Mn-Ni-C alloys by EMF measurements2003In: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 11, no 11-12, p. 1229-1235Article in journal (Refereed)
    Abstract [en]

     The activities of manganese in Mn-Ni-C alloys have been studied by solid-state galvanic cell technique with CaF2 as the solid electrolyte. The measurements of electromotive force (EMF) have been carried out in the temperature range 920-1240 K. The main phase compositions of the alloys have been analyzed by X-ray diffraction (XRD). It was established that the substitution of Mn by Ni in the (MnNi)(23)C-6 carbide was limited, that the lattice parameter decreased slightly with increase in the Ni content and that a solid solution is formed between Mn and Ni. It was also found that the activity of manganese decreases with increase in the nickel content when the ratio of C/(Mn+C) is less than 8.3 wt.%, and that the negative effect of Ni on the activity of Mn in Mn-Ni-C ternary system decreases as the carbon content increases. However, when the ratio of C/(Mn+C) is equal to 8.3 wt.% or more, the activity of manganese is independent of the nickel content.

  • 32.
    Teng, Lidong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Aune, Ragnhild
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Sesadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Thermodynamic investigations of the C-Cr-Fe system by galvanic cell technique2005In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 36, no 2, p. 263-270Article in journal (Refereed)
    Abstract [en]

    In view of the applications of intermetallic carbides in the hard materials industries, the thermodynamic properties of the C-Cr-Fe system have been measured by the use of the solid-state galvanic cell technique with CaF2 as the solid electrolyte. The thermodynamic activities of chromium have been calculated from the results of the electromotive force (EMF) measurements. For the calculations, pure b+cc-Cr was used as the standard state. X-ray diffraction (XRD) and scanning electron microscopy were used to identify the stable phases present in each investigated sample, as well as for establishing the phase compositions. The experimental results obtained were compared with data calculated by the use of the TCFE3 database available with the Thermo-Calc software.

  • 33.
    Teng, Lidong
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Lu, Xiao Gang
    KTH, Superseded Departments, Materials Science and Engineering.
    Aune, Ragnhild
    KTH, Superseded Departments, Materials Science and Engineering.
    Seetharaman, Sesadri
    KTH, Superseded Departments, Materials Science and Engineering.
    Thermodynamic investigations of Cr3C2 and reassessment of the Cr-C system2004In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 35A, no 12, p. 3673-3680Article in journal (Refereed)
    Abstract [en]

    The Gibbs energies of formation for Cr3C2, Δ fCr3C2, have been obtained from electromotive force (EMF) measurements, in the temperature range 950 to 1150 K, using the following galvanic cells with CaF2 single crystals as the electrolyte: Cr, CrF2 CaF2 CrF2, Cr 3C2, C (950 to 1150 K) Extreme precautions were taken during the experimental measurements to avoid errors. The reliability and reproducibility of the values were confirmed by careful repetition of several of the experiments. The following equation has been obtained by a linear analysis of the EMF results as a function of temperature: ΔfCr3C2(± 1600) = - 58,857 - 22.344T (J·mo1-1) (950 to 1150 K) The generated values are compared with those reported in the literature. The values of the enthalpy of formation were evaluated by using a third-law analysis, and an average value of Δf298 = -71.7 kJ/mol was obtained. The ground-state energy of the hypothetic end-member compound CrC3 in the bcc structure at 0 K was calculated by using the ab initio method. The experimental results obtained, as well as the results from the ab initio calculations, were employed in a reassessment of the Cr-C system using the CALPHAD approach. A new set of parameters for the bcc phase was evaluated using first-principles calculations.

  • 34.
    Teng, Lidong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nakatomi, Daisuke
    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.
    Oxidation behavior of TiAl-8Nb turbine blade alloy2007In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 38, no 3, p. 477-484Article in journal (Refereed)
    Abstract [en]

    The oxidation behavior of the TiAl-8Nb alloy has been investigated by the thermogravimetric method. Isothermal experiments were carried out in the temperature range of 1173 to 1473 K in air as atmosphere. The activation energy of the reaction was calculated from the results of the isothermal experiments. The results show that the reaction rate is controlled during the initial stages by the chemical reaction, while, at the later stages, the diffusion process is likely to be the rate-controlling step. Further, the rate-determining diffusion step is likely to be the self-diffusion of Ti in alloy. The microstructure and composition distribution of the oxide layer were analyzed by scanning electronic microscopy (SEM) and electron dispersion spectroscopy (EDS). A mechanism for oxidation of the TiAl-8Nb alloy in the experimental temperature range is proposed based on the experimental results.

  • 35.
    Teng, Lidong
    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.
    Nzotta, M.
    Dong, R. D.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ge, H. L.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wang, Lijun
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wang, Haijuan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Chychko, Andrei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    RETENTION, RECOVERY AND RECYCLING OF METAL VALUES FROM HIGH ALLOYED STEEL SLAGS2010In: ARCH METALL MATER, ISSN 1733-3490, Vol. 55, no 4, p. 1097-1104Article in journal (Refereed)
    Abstract [en]

    The work was carried out in four parallel directions. The thermodynamic activities of oxides of Cr in steel slags were determined by slag-gas equilibration technique. The ratio of Cr2+/Cr3+ in CaO-MgO(-FeO)-AlO3-SiO2-CrO(x)system slags was measured by X-ray absorption near edge spectra (XANES). High-temperature mass spectrometry method was also used to obtain the distribution of chromium oxides. A mathematical correlation was established for estimating the ratio of Cr2+/Cr3+ as a function of temperature, partial pressure of oxygen and slag basicity. Laboratory investigations of the decarburization of high alloy steels under controlled oxygen potentials have been carried out to retain Cr in the steel phase. A mathematical model has been developed for the decarburization process with controlled oxygen partial pressure. Experimental and theoretical investigations have been carried out in optimizing the Mo-additions to steel in the EAF practice in Uddeholm Tooling AB. Substantial saving of Mo as well as less emissions of Mo-bearing dust are indicated in the study. A salt extraction process was developed to extract the metal values from steel slags. Successful extractions, followed by electrolysis indicate that this could be a viable route towards recovery of metals from metallurgical slags.

  • 36.
    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.

  • 37. 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.

  • 38.
    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.

  • 39.
    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.

  • 40. 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.

  • 41. 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.

  • 42.
    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.

  • 43.
    Xie, Jiaying
    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.
    Teng, Li-Dong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Chen, N-X
    Atomistic study on the site preference and thermodynamic properties for Cr23-xFexC62005In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 53, no 20, p. 5305-5312Article in journal (Refereed)
    Abstract [en]

    The site preference of Fe in Cr23-xFexC6 is investigated based on the interatomic potentials obtained by the lattice inversion method. The calculated results show that Fe atoms preferentially Substitute For Cr at 4a sites first and then 8c sites. The structural parameters of Cr23-xFexC6 With content x are calculated and the results are consistent with experimental results. The calculated cohesive energies indicate that the increase in x value is accompanied by the decrease in the stability of Cr23-xFexC6. The thermodynamic properties of Cr23C6, such as the phonon density of states and vibrational entropy, as well as the bulk modulus of Cr23-xFexC6 are evaluated. The calculated results are in good agreement with experimental results. This work provides a simple and promising method for Studying the properties of carbides with complex structures

  • 44.
    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.

  • 45.
    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.

  • 46.
    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)
  • 47.
    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.

  • 48.
    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.

  • 49.
    Zhang, Zuotai
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Teng, Li-Dong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Li, Wenchao
    Mechanical Properties and Microstructures of hot-pressed MgAlON-BN Composites2007In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 27, no 1, p. 319-326Article in journal (Refereed)
    Abstract [en]

    The relationship between the mechanical properties and microstructure of hot-pressed MgAlON-BN composite materials was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution electron microscopy (HREM) and X-ray diffraction (XRD) techniques. The phase compositions of hot-pressed samples prepared from starting mixtures of Al2O3, AlN, MgO and h-BN consisted of MgAlON phases as a matrix and BN phases as the second phase. The density, bending strength at room temperature, fracture toughness and Vickers hardness were measured. The results indicated that the density, strength and Vickers hardness decrease with increasing h-BN content due to the non-reactive nature and layered structure of h-BN. The fracture toughness, however increased with increasing h-BN addition, reaching a maximum of 3.64 MPa m(0.5); it decreased with further increase of BN content. The increase of fracture toughness was attributed to the presence of microcracks and the decrease was considered to be the discontinuous microstructure of the MgAlON phases. Temperature dependence of bending strength remained constant at low temperature, followed by an increase at 800 degrees C and then, dropped quickly. The increase in the bending strength of the composite was attributed to the decrease of residual stress and to the interwoven microstructure of the composites which prevented grain boundary slip and reduced the attenuation rate of high temperature strength. The machinability of the composites was examined. The results indicate that the composite materials with BN content more than 15 vol.% exhibit excellent machinability and could be drilled using conventional hard metal alloy drills

  • 50.
    Zhang, Zuotai
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Teng, Li-Dong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Li, Wenchao
    Thermal shock Behavior of MgAlON and MgAlON-BN CompositesArticle in journal (Refereed)
1 - 50 of 50
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