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  • 1. Abbasalizadeh, A.
    et al.
    Sridar, S.
    Chen, Z.
    Sluiter, M.
    Yang, Y.
    Sietsma, J.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Hari Kumar, K. C.
    Experimental investigation and thermodynamic modelling of LiF-NdF3-DyF3 system2018Inngår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 753, s. 388-394Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrolysis of molten fluorides is one of the promising methods for the recovery and recycling of rare earth metals from used magnets. Due to the dearth of phase equilibria data for molten fluoride systems, thermodynamic modelling of LiF-DyF3-NdF3 system using the CALPHAD approach was carried out. Gibbs energy modelling for LiF-NdF3 and LiF-DyF3 systems was performed using the constitutional data from literature. Ab initio calculations were used to obtain enthalpy of reaction of LiDyF4, an intermediate phase that is found to exist in the LiF-DyF3 system. Differential thermal analysis was carried out for selected compositions in the NdF3-DyF3 system, in order to determine liquidus and solidus temperatures. The Gibbs energy parameters for the limiting binaries determined in this work is used for modelling the Gibbs energy functions of equilibrium phases in the ternary system. Selected compositions of LiF-NdF3-DyF3 were subjected to DTA in order to validate the calculated phase temperatures involving melt.

  • 2. Abbasalizadeh, A.
    et al.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Sietsma, J.
    Yang, Y.
    Rare Earth Extraction from NdFeB Magnets and Rare Earth Oxides Using Aluminum Chloride/Fluoride Molten Salts2015Inngår i: Rare Earths Industry: Technological, Economic, and Environmental Implications, Elsevier, 2015, s. 357-373Kapittel i bok, del av antologi (Annet vitenskapelig)
    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.

  • 3. Abbasalizadeh, Aida
    et al.
    Malfliet, Annelies
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sietsma, Jilt
    Yang, Yongxiang
    Electrochemical Extraction of Rare Earth Metals in Molten Fluorides: Conversion of Rare Earth Oxides into Rare Earth Fluorides Using Fluoride Additives2017Inngår i: JOURNAL OF SUSTAINABLE METALLURGY, ISSN 2199-3823, Vol. 3, nr 3, s. 627-637Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present research on rare earth extraction from rare earth oxides (REOs), conversion of rare earth oxides into rare earth fluorides with fluoride fluxes is investigated in order to overcome the problem of low solubility of the rare earth oxides in molten fluoride salts as well as the formation of oxyfluorides in the fluorination process. Based on thermodynamic calculations, a series of experiments were performed for converting the rare earth oxides into rare earth fluorides using AlF3, ZnF2, FeF3, and Na3AlF6 as fluorinating agents in a LiF-Nd2O3 system. The formation of neodymium fluoride as a result of the reactions between these fluxes and neodymium oxide is confirmed. The rare earth fluoride thus formed can subsequently be processed through the electrolysis route in the same reactor, and rare earth metal can be produced as the cathodic deposit. In this concept, the REO dissolution in molten fluorides would become unnecessary due to the complete conversion of the oxide into the fluoride, REF3. The results of XRD and EPMA analysis of the reacted samples indicate that AlF3, ZnF2, and FeF3 can act as strong fluorinating agents for the neodymium oxide giving rise to a complete conversion of neodymium oxide into neodymium fluoride.

  • 4. Abbasalizadeh, Aida
    et al.
    Malfliet, Annelies
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sietsma, Jilt
    Yang, Yongxiang
    Electrochemical Recovery of Rare Earth Elements from Magnets: Conversion of Rare Earth Based Metals into Rare Earth Fluorides in Molten Salts2017Inngår i: Materials transactions, ISSN 1345-9678, E-ISSN 1347-5320, Vol. 58, nr 3, s. 400-405Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, selective extraction of rare earth (RE) metals from NdFeB magnets is investigated by studying the effects of various fluxes, viz. AlF3, ZnF2, FeF3 and Na3AlF6 in the LiF-NdFeB system. The aim is to convert RE from RE magnet into the fluoride salt melt. The results show the complete selective separation of neodymium (also dysprosium) from the magnet and formation of rare earth fluoride, leaving iron and boron unreacted. The formed rare earth fluoride can subsequently be processed in the same reactor through an electrolysis route so that RE can be deposited as a cathode product. The results of XRD and EPMA analysis of the reacted samples indicate that AlF3, ZnF2 and FeF3 can act as strong fluorinating agents for extraction of rare earth from NdFeB magnet, converting the RE to REF3. The results confirm the feasibility of the rare earth metals recovery from scrap NdFeB magnet as raw material. The fluoride conversion- electrolysis route suggested in the present work enables the extraction of rare earth metals in a single step using the above-mentioned fluxes.

  • 5.
    Abbasalizadeh, Aida
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Sridhar, Seetharaman
    Grinder, Olle
    Izumi, Yukari
    Barati, Mansoor
    Highlights of the Salt Extraction Process2013Inngår i: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 65, nr 11, s. 1552-1558Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 6. Abbasalizadeh, Aida
    et al.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Venkatesan, Prakash
    Sietsma, Jilt
    Yang, Yongxiang
    Novel Reactive Anode for Electrochemical Extraction of Rare Earth Metals from Rare Earth Oxides2017Inngår i: RARE METAL TECHNOLOGY 2017 / [ed] Kim, H Alam, S Neelameggham, NR Oosterhof, H Ouchi, T Guan, X, SPRINGER INTERNATIONAL PUBLISHING AG , 2017, s. 87-92Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Electrolytic production of metallic neodymium is carried out in fused fluoride salts containing neodymium oxide. Two major challenges pertaining to neodymium production are (a) low oxide solubility, (b) possibility of anodic fluorine gas evolution if the electrolysis rate exceeds feeding rate of neodymium oxide. In this study, a novel method is proposed in which iron fluoride (FeF3) is used as a fluorinating agent to convert neodymium oxide into neodymium fluoride. Electron Probe Micro Analysis (EPMA) results of as-converted salt show a complete conversion of neodymium oxide into neodymium fluoride. In the electrolysis process, iron is used as a reactive anode with electrochemical dissolution of iron into the melt, thus preventing fluorine gas evolution at the anode. Therefore, the fluorinating agent is constantly regenerated in situ which enables the continuous conversion of neodymium oxide feed. The cathodic product is a Nd-Fe alloy which can be directly used as a master alloy for the production of NdFeB permanent magnets.

  • 7.
    Abbasalizadeh, Aida
    et al.
    Delft Univ Technol TU Delft, Dept Mat Sci & Engn, Mekelweg 2, NL-2628 CD Delft, Netherlands..
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Venkatesan, Prakash
    Delft Univ Technol TU Delft, Dept Mat Sci & Engn, Mekelweg 2, NL-2628 CD Delft, Netherlands..
    Sietsma, Jilt
    Delft Univ Technol TU Delft, Dept Mat Sci & Engn, Mekelweg 2, NL-2628 CD Delft, Netherlands..
    Yang, Yongxiang
    Delft Univ Technol TU Delft, Dept Mat Sci & Engn, Mekelweg 2, NL-2628 CD Delft, Netherlands..
    Use of iron reactive anode in electrowinning of neodymium from neodymium oxide2019Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 310, s. 146-152Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrolytic production of metallic neodymium is carried out in fused neodymium fluoride salts containing neodymium oxide. Two major challenges pertaining to neodymium production in fluoride salts are a) low solubility of neodymium oxide in fluoride melt, b) possibility of anodic gas evolution (CO, CO2, CF4, C2F6). In this study, iron is used as a reactive anode in the electrolysis process, promoting electrochemical dissolution of iron into the melt, preventing PFC (perfluorocarbon) gas evolution at the anode. Further, the rare earth oxide is converted to rare earth fluoride by the use of iron fluoride formed as the result of iron dissolution. Thus, the fluoridizing agent is constantly regenerated in-situ which enables the continuous conversion of neodymium oxide feed. The cathodic product is Nd-Fe alloy which can be used as a master alloy for the production of NdFeB magnets. 

  • 8.
    Abbasalizadeh, Aida
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Sridhar, S.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Neodymium extraction using salt extraction process2015Inngår i: Mineral Processing and Extractive Metallurgy: Transactions of the Institutions of Mining and Metallurgy: Section C, ISSN 0371-9553, E-ISSN 1743-2855, Vol. 124, nr 4, s. 191-198Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 9.
    Abdul Abas, Riad
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Thermal Diffusivity of Sintered Stainless steel-Alumina Composites2006Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, nr 4, s. 513-518Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermal diffusivity measurements were carried out as a function of temperature on sintered AISI 304 stainless steel-alumina composites having various compositions (0.001, 0.01, 0, 1, 1, 2, 3, 5, 7, 8, and 10 wt pct Al2O3). The measurements were carried out between room temperature and 1473 K. The thermal diffusivity and the thermal conductivity were found to increase with temperature in all the composite specimens. The thermal diffusivity was found to decrease with increasing weight fraction of alumina. This tendency can clearly be seen at temperatures above 755 K. The experimental results are in good agreement with the simple rule of mixture, the Eucken equation, and the Ohm’s law model developed by Hayashi et al. at weight fractions of alumina below 5 wt pct. Beyond this composition, the thermal diffusivity/conductivity shows a large discrepancy from the models. This could probably be attributed to the accumulation of alumina particles during cooled pressing and sintering.

  • 10. Ahmed, H. M.
    et al.
    Viswanathan, N. N.
    Seetharaman, Seshadri
    KTH.
    Gas-Condensed Phase Reactions - A Novel Route to Synthesize Alloys and Intermetallics Involving Refractory Metals2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Reduction and simultaneous reduction-carburization of oxide mixtures to get intermetallics and composite materials may open up shorter process routes towards the end-user needs. The use of natural gas or hydrogen would be environment-friendly. With these aims, the corresponding kinetics were studied by thermogravimetry, gas chromatography as well as laser-flash method. It was found that, under identical conditions, the Arrhenius activation energy for the reduction is proportional to the thermodynamic stability of the compound reduced. Intermetallics could be synthesized successfully and the product was found to have nanograins. Also, Metallic coating on copper surfaces was successfully developed.

  • 11.
    Ahmed, Hesham M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    El-Geassy, A. H. A.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Kinetics of Reduction of NiO-WO3 Mixtures by Hydrogen2010Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, nr 1, s. 161-172Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The kinetics of reduction of the oxide mixtures of Ni-W with different Ni/(Ni-W) molar ratios within the range of 923 K to 1173 K in flowing hydrogen gas was investigated by means of thermogravimetric analysis under isothermal conditions. The products were examined by X-ray diffraction, scanning electron microscope (SEM), and electron dispersion spectroscopy (EDS) analyses. Five different oxide mixtures apart from the pure oxides were studied in the present work. The results indicate that the reduction reaction proceeds through three consecutive steps that are as follows: NiO-WO3 -> Ni-WO3 -> Ni-WO2 -> Ni-W From the experimental results, the Arrhenius activation energies of the three steps were evaluated for all of the studied compositions. The activation energy for the first step was calculated to be approximately 18 kJ/mol. For the second and third stages, the activation energy values varied from 62 to 38 kJ/mol for the second stage and 51 to 34 kJ/mol for the third stage depending on the Ni/(Ni + W) molar ratio in the precursors; the activation energy increased with increasing ratios. SEM images showed that the grain size of the final product was dependent on the Ni/(Ni + W) molar ratio; smaller grains were formed at higher nickel contents.

  • 12.
    Ahmed, Hesham M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    El-Geassy, Abdel-Hady A.
    Viswanathan, Nurni Neelakantan
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Kinetics and Mathematical Modeling of Hydrogen Reduction of NiO-WO(3) Precursors in Fluidized Bed Reactor2011Inngår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, nr 9, s. 1383-1391Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, Fluidized bed reduction of NiO-WO(3) precursors was investigated isothermally at temperatures 973-1 273 K. The reaction progress was monitored by analysis of H(2)O evolved during the reaction process using a gas chromatograph instrument. A theoretical model based on intrinsic chemical reaction rate constants and thermodynamic equilibria was developed to estimate the apparent reaction rate constant for the reduction reaction. In developing the model, the particles are considered to be in a completely mixed condition and gas flow is described as plug flow. The proposed model is also suitable for scale-up calculations. The interfacial chemical reaction model was found to fit the experimental results. The apparent activation energy values of the reduction process at different stages were calculated accordingly. The present investigation proved that the fluidized bed technique can be successfully utilized in bulk production of intermetallics containing W and a transition metal (or a composite material) wherein the process conditions would have a strong impact on the particle size of the end product.

  • 13.
    Ahmed, Hesham M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Isothermal dynamic thermal diffusivity studies of the reduction of NiO and NiWO(4) precursors by hydrogen2011Inngår i: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, Vol. 102, nr 11, s. 1336-1344Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermal diffusivity measurements of uniaxially cold pressed NiO and NiWO(4) were carried out in a dynamic mode in order to monitor the kinetics of hydrogen reduction of the above-mentioned materials using a laser flash unit. The calculated activation energy was found to be higher than that for chemically-controlled reaction obtained earlier by thermogravimetry. The difference has been attributed to physical changes occurring along with the chemical reaction. The activation energy of sintering of the products was evaluated to be 33 and 36 kJ.mol(-1) for NiO and NiWO(4), respectively. Thermal conductivities were calculated taking into consideration the change in heat capacity considering the compositional and the structural changes with the progress of the reaction. The potentiality of the laser-flash method as a complementary technique to thermogravimetry in understanding the mechanism of gas solid reactions is discussed.

  • 14.
    Ahmed, Hesham M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Reduction-Carburization of NiO-WO3 Under Isothermal Conditions Using H2-CH4 Gas Mixture2010Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, nr 1, s. 173-181Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ni-W-C ternary carbides were synthesized by simultaneous reduction–carburization of NiO-WO3 oxide precursors using H2-CH4 gas mixtures in the temperature range of 973 to 1273 K. The kinetics of the gas–solid reaction were followed closely by monitoring the mass changes using the thermogravimetric method (TGA). As a thin bed of the precursors were used, each particle was in direct contact with the gas mixture. The results showed that the hydrogen reduction of the oxide mixture was complete before the carburization took place. The nascent particles of the metals formed by reduction could react with the gas mixture with well-defined carbon potential to form a uniform product of Ni-W-C. Consequently, the reaction rate could be conceived as being controlled by the chemical reaction. From the reaction rate, Arrhenius activation energies for reduction and carburization were evaluated. Characterization of the carbides produced was carried out using X-ray diffraction and a scanning electron microscope (SEM) combined with electron dispersion spectroscopy (SEM-EDS) analyses. The grain sizes also were determined. The process parameters, such as the temperature of the reduction–carburization reaction and the composition of the gas mixture, had a strong impact on the carbide composition as well as on the grain size. The results are discussed in light of the reduction kinetics of the oxides and the thermodynamic constraints.

  • 15.
    Ahmed, Hesham M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Viswanathan, N. N.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    On The Kinetics of Hydrogen Reduction of NiO-WO3 Precursors in Fluidized Bed- A Modeling Approach2011Inngår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, nr 9, s. 1383-1391Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, Fluidized bed reduction of NiO-WO3 precursors was investigated isothermally at temperatures 973-1 273 K. The reaction progress was monitored by analysis of H2O evolved during the reaction process using a gas chromatograph instrument. A theoretical model based on intrinsic chemical reaction rate constants and thermodynamic equilibria was developed to estimate the apparent reaction rate constant for the reduction reaction. In developing the model, the particles are considered to be in a completely mixed condition and gas flow is described as plug flow. The proposed model is also suitable for scale-up calculations. The interfacial chemical reaction model was found to fit the experimental results. The apparent activation energy values of the reduction process at different stages were calculated accordingly. The present investigation proved that the fluidized bed technique can be successfully utilized in bulk production of intermetallics containing W and a transition metal (or a composite material) wherein the process conditions would have a strong impact on the particle size of the end product.

  • 16.
    Ahmed, Hesham M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Viswanathan, Nurini N.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Dynamic Thermal Diffusivity Measurements - A Tool for Studying Gas-Solid Reactions2011Inngår i: DIFFUSION IN SOLIDS AND LIQUIDS VI, PTS 1 AND 2, 2011, s. 217-222Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the present work, the thermal diffusivity measurements of uniaxially cold pressed NiWO(4) has been carried out. The measurements were performed isothermally at temperatures between 973 and 1273 K under H(2) gas using the laser flash technique. The experimental thermal diffusivity values were found to increase with the reduction progress as well as with increasing temperature. The calculated activation energy was found to be higher than that for chemically controlled reaction. The difference has been attributed to factors like agglomeration of the product as well as sintering of the precursor along with the chemical reaction. In order to sort out the sintering effect on the thermal diffusivity values, complementary experiments have been done on pressed NiWO(4) and Ni-W, produced by the reduction of NiWO(4) at 1123K, under Argon gas. The porosity change and its effect on thermal diffusivity values have been studied.

  • 17.
    Ahmed, Hesham
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Mis, Michal
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    El-Geassy, Abdel-Hady
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Seethararnan, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Reduction-Carburization of the Oxides of Ni and W Towards the Synthesis of Ni-W-C Carbides2010Inngår i: ADVANCED MATERIALS FORUM V, PT 1 AND 2  / [ed] Rosa LG; Margarido F, 2010, Vol. 636-637, s. 952-962Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Ternary Ni-W-C cemented carbides were synthesized directly from mixture powder of NiO-WO3 by simultaneous reduction-carburization in mixed H-2-CH4 gas environment in a thin bed reactor in the temperature range 973-1273K. The kinetics of the reaction was closely followed by monitoring the mass change using thermogravimetric method (TGA). The nascent particles of the metals formed by reduction could react with the gas mixture with well-defined carbon potential to form a uniform product of Ni-W-C. The gas mixture ratio was adjusted in such a way that the Ni-W-C formed was close to the two phase tie line. In view of the fact that each particle was in direct contact with the gas mixture, the reaction rate could be conceived as being controlled by the combined reduction-carburization reaction. From the reaction rate, the Arrhenius activation energies were evaluated. Characterization of the carbides produced was carried out by using X-ray diffraction, SEM-EDS as well as high resolution electron microscope (HREM). The grain sizes were also determined. Correlations were found between the carbide composition as well as grain size and the process parameters such as temperature of the reduction-carburization reaction as well as the composition of the gas mixture. The results are discussed in the light of the kinetics of the reduction of oxides and the thermodynamic constraints.

  • 18. Ahmed, Hesham
    et al.
    Morales-Estrella, R.
    Viswanathan, Nurin
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Gas-Solid Reaction Route toward the Production of Intermetallics from Their Corresponding Oxide Mixtures2016Inngår i: Metals, ISSN 2075-4701, Vol. 6, nr 8, artikkel-id 190Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Near-net shape forming of metallic components from metallic powders produced in situ from reduction of corresponding pure metal oxides has not been explored to a large extent. Such a process can be probably termed in short as the "Reduction-Sintering" process. This methodology can be especially effective in producing components containing refractory metals. Additionally, in situ production of metallic powder from complex oxides containing more than one metallic element may result in in situ alloying during reduction, possibly at lower temperatures. With this motivation, in situ reduction of complex oxides mixtures containing more than one metallic element has been investigated intensively over a period of years in the department of materials science, KTH, Sweden. This review highlights the most important features of that investigation. The investigation includes not only synthesis of intermetallics and refractory metals using the gas solid reaction route but also study the reaction kinetics and mechanism. Environmentally friendly gases like H-2, CH4 and N-2 were used for simultaneous reduction, carburization and nitridation, respectively. Different techniques have been utilized. A thermogravimetric analyzer was used to accurately control the process conditions and obtain reaction kinetics. The fluidized bed technique has been utilized to study the possibility of bulk production of intermetallics compared to milligrams in TGA. Carburization and nitridation of nascent formed intermetallics were successfully carried out. A novel method based on material thermal property was explored to track the reaction progress and estimate the reaction kinetics. This method implies the dynamic measure of thermal diffusivity using laser flash method. These efforts end up with a successful preparation of nanograined intermetallics like Fe-Mo and Ni-W. In addition, it ends up with simultaneous reduction and synthesis of Ni-WN and Ni-WC from their oxide mixtures in single step.

  • 19.
    Albertsson, Galina
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Björkman, Bo
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Engström, Fredrik
    Effect of Low Oxygen Partial Pressure on the Chromium Partition in CaO-MgO-SiO2-Cr2O3-Al2O3 Synthetic Slag at Elevated Temperatures2013Inngår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, nr 7, s. 670-679Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 20. Andersson, G.
    et al.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    "Steel eco-cycle" - A Swedish cross-pollination environmental research program2013Inngår i: Materials Science and Technology Conference and Exhibition 2013, MS and T 2013, Warrendale , 2013, s. 1784-1791Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In 2004, Swedish steel industry launched the first truly holistic research program in one of the world's most energy intensive industries with the aim to drastically increase the energy and resource efficiency by governing and reinforce (closing) the loop in the steel life cycle. The inter-disciplinary approach of the program has led to a significant cross-pollination in environmental steel technology and related areas apart from the impact in the educational field. The program, alongside the development of resource-efficient production of steel, has led to offshoots in aluminium remelting industry, recovery of rare earths from magnetic scrap and recovery of lead from CRT glasses. The research efforts led to the successful recovery of vanadium and magnetically important manganese nanoferrites from (waste) steel slags. The results, in fact, even provide insights into declarations of human attitudes, future raw material prognoses, process optimizations and pilot plant trials along with instrument and model developments.

  • 21. Basu, S.
    et al.
    Lahiri, A. K.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Activity of Ferric Oxide in Steelmaking Slag2010Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, nr 2, s. 414-419Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Refining reactions in steelmaking primarily involve oxidation of impurity element(s). The oxidation potential of the slag and the activity of oxygen in the metal (h(O)) are the major factors controlling these chemical reactions. In turn, the oxidation potential of the slag is influenced strongly by the equilibrium distribution of oxygen between ferrous and ferric oxides. We recently investigated the activity coefficient of FeO in steelmaking slag and the effect of chemical composition thereon. This work is focused on estimation of the activity coefficient of Fe2O3.

  • 22. Basu, S.
    et al.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Lahiri, A. K.
    Thermodynamics of Phosphorus and Sulphur Removal during Basic Oxygen Steelmaking2010Inngår i: STEEL RESEARCH INTERNATIONAL    , 2010, Vol. 81, nr 11, s. 932-939Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Removal of impurity elements from hot metal is essential in basic oxygen steelmaking. Oxidation of phosphorus from hot metal has been studied by several authors since the early days of steelmaking. Influence of different parameters on the distribution of phosphorus, seen during the recent work of the authors, differs somewhat from that reported earlier. On the other hand, removal of sulphur during steelmaking has drawn much less attention. This may be due to the magnitude of desulphurisation in oxygen steelmaking being relatively low and desulphurisation during hot metal pre-treatment or in the ladle furnace offering better commercial viability Further, it is normally accepted that sulphur is removed to steelmaking slag in the form of sulphide only However, recent investigations have indicated that a significant amount of sulphur removed during basic oxygen steelmaking can exist in the form of sulphate in the slag under oxidising conditions. The distribution of sulphur during steelmaking becomes more important in the event of carry-over of sulphur-rich blast-furnace slag, which increases sulphur load in the BOF. The chemical nature of sulphur in this slag undergoes a gradual transition from sulphide to sulphate as the oxidative refining progresses.

  • 23.
    Cao, Weimin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Delin, Anna
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Calculation of Oxygen and Sulfur Average Velocity on the Iron Surface: A Two-dimensional Gas Model Study2010Inngår i: Steel Research International, ISSN 1611-3683, Vol. 81, nr 11, s. 949-952Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, a two-dimensional (2D) gas model is derived and used to simulate the average velocity of individual atoms of the surface active elements oxygen and sulfur on the Fe(100) surface. The average velocity of oxygen and sulfur atoms was found to be related to the vibration frequencies and minimal energy barrier. The calculated results are based on data from density functional calculations combined with thermodynamics and statistical physics. The calculated average velocity of oxygen on the Fe (100) is lower than that of sulphur. This is because of the stronger interaction between oxygen and the first iron layer. We conclude that our simple 2D gas model may be useful for simulating and understanding the complex interfacial phenomena in the steelmaking refining process from an atomic point of view.

  • 24.
    Cao, Weimin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Muhmood, Luckman
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Sulfur Transfer at Slag/Metal Interface-Impact of Oxygen Potential2012Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, nr 2, s. 363-369Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, the interfacial movement resulting from sulfur mass transfer at the slag/metal interface was monitored by X-ray sessile drop method in dynamic mode at temperature 1873 K (1600 A degrees C) under nonequilibrium conditions. The experiments were carried out with pure iron and CaO-SiO2-Al2O3-FeO slag (alumina saturated at the experimental temperature) contained in alumina crucibles with well-controlled partial pressures of oxygen and sulfur. The impact of oxygen potential on the droplet oscillation as sulfur from the gas phase reaches the metal drop through the intermediate slag phase was monitored. The interfacial velocity was investigated. It was found that the increases of interfacial velocity and the maximum oscillation time were mainly attributed to the partial pressure of oxygen increases. The experiment results were explained by previous ab initio calculations. The thermo-physical and thermo-chemical properties of slag were also found to influence interfacial velocity.

  • 25.
    Chychko, Andrei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Foaming in Electric Arc Furnace: Part I: Laboratory Studies of Enthalpy changes of Carbonate Additions to Slag Melts2011Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 42, nr 1, s. 20-29Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, a modified thermal analysis technique was used for studying the heat effect of slag foaming with carbonates addition. Experiments were conducted by sinking limestone and dolomite pieces of defined shapes (together with iron sinkers) in molten slag and monitoring the temperature changes accompanying the decomposition of carbonates. The heat effects of dolomite and limestone decompositions were determined at 1623 K (1350 A degrees C) and 1673 K (1400 A degrees C). It was found that the decomposition energy for dolomite and limestone for the studied slag composition is in the range of 56 to 79 pct of theoretical values, which is linked to the energy-saving effect of slag foaming. No influence of sample shape on decomposition energy was found for both limestone and dolomite.

  • 26.
    Chychko, Andrei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Nzotta, M.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Fe2MoO4 as a precursor material for Mo alloying in steel: (Part II): Upscaling test2011Inngår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 82, nr 8, s. 886-897Artikkel i tidsskrift (Fagfellevurdert)
    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

  • 27.
    Chychko, Andrei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Nzotta, M.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Synthesis and characterization of Fe2MoO4 as a precursor material for Mo alloying in steel2011Inngår i: Steel Research International, ISSN 1611-3683, Vol. 82, nr 3, s. 269-276Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 28.
    Chychko, Andrei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    ENERGY SAVING EFFECT OF SLAG FOAMING BY CARBONATE ADDITIONS IN EAF PROCESS2010Inngår i: ARCH METALL MATER, ISSN 1733-3490, Vol. 55, nr 4, s. 1089-1095Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 29.
    Chychko, Andrei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    Foaming in Electric Arc Furnace: Part II: Foaming visualization and Comparison with Plant trials2012Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, nr 5, s. 1078-1085Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 30.
    Chychko, Andrei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    MoO3 Evaporation Studies from Binary Systems towards Choice of Mo Precursors in EAF2010Inngår i: Steel Research International, ISSN 1611-3683, Vol. 81, nr 9, s. 784-791Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 31. El-Geassy, A. A.
    et al.
    Nassir, Nassier Abdul
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Ahmed, H. M.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Simultaneous reduction nitridation for the synthesis of tungsten nitrides from Ni-W-O precursors2013Inngår i: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 56, nr 5, s. 411-419Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tungsten nitrides were synthesised from NiO-WO3 and NiWO 4 precursors at 973-1273 K in a flow of H2-N2 gas mixture. The reduction-nitridation reactions were carried out isothermally in fluidised bed reactor, and the off-gas from the reactions was continuously analysed by gas chromatography. The effect of reaction temperature and precursor composition on the rate of formation of Ni-W nitrides was studied. The different phases developed during the reduction-nitridation reactions were identified by X-ray diffraction analysis technique. The morphology and the grain structure of the precursors were examined by SEM, and the elemental composition in the structure was analysed by electron dispersive spectrometry. The results showed that the reduction of Ni-W-O precursors proceeded in a stepwise manner (NiWO4→Ni-WO3→Ni-WO2→Ni-W). Tungsten nitrides (WN and WN2) were formed from the reaction of the freshly reduced W metal with N2 gas and WN was the predominant phase detected at higher temperatures. The reaction mechanisms were elucidated from the apparent activation energy values and the application of different formulations derived from the gas-solid reaction model at early and later stages of reactions. It was concluded that the interfacial chemical reaction is the rate determining step at initial stages, while a combined effect of gaseous diffusion and interfacial chemical reaction controlled the reaction at later stages. At final stages, the nitridation reactions contributed to the reaction mechanism leading to produce tungsten nitrides.

  • 32. El-Geassy, A. A.
    et al.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Synthesis and characterization of nano-structured molybdenum-iron intermetallics by gas-solid reaction technique2016Inngår i: IOP Conference Series: Materials Science and Engineering, Institute of Physics Publishing (IOPP), 2016, Vol. 119, nr 1, artikkel-id 012012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Ammonium molybdate and ferrous oxalate were used for the synthesis of nano-structured Mo-Fe intermetallics. Co-precipitation technique was applied to produce Mo/Fe precursors containing 58/42, 72/28 and 30/70 mass% respectively. The different phases formed were identified by XRD. The macro- and microstructures were microscopically examined by Reflected Light Microscope (RLM) and Scanning Electron Microscope (SEM) coupled with Electron Dispersion Spectroscopy (EDS). TG-DTA-DSC technique was applied to follow up the behavior of precursors up to 900oC (10K/min.). Endothermic peaks were detected at 97.8, 196.9 and 392.7oC due to the decomposition reactions to produce MoO3 and Fe2O3. The exothermic peak resulted at 427.8oC is due to the solid state reaction between these oxides to form Fe2(MoO4)3. Precursors were isothermally reduced at 600-850oC in a flow of purified H2 and the O2-weight loss from the reduction reactions was continuously recorded as a function of time. The isothermal reduction behavior of precursors was investigated. The structures of reduced products and the different phases formed were investigated and correlated with the reduction conditions. At >60% reduction extents, Fe2(MoO4)3] phase was first reduced to Fe2MoO3O8 before the formation of FeMo, while FeMoO4 and MoO2 were reduced to FeMo and Mo. In precursors containing higher content of Fe2O3, FeMo, Fe3Mo and Fe phases were produced. The visual observation of reduced samples showed that the volume was gradually shrinking with rise in temperature up to 800oC and beyond which a measurable swelling was observed reaching about 170% at 900oC.

  • 33.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Grinder, Olle
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    The salt extraction process: A novel route for metal extraction part 1 - Cr, Fe recovery from EAF slags and low grade chromite ores2010Inngår i: Mineral Processing and Extractive Metallurgy: Transactions of the Institutions of Mining and Metallurgy: Section C, ISSN 0371-9553, E-ISSN 1743-2855, ISSN 0371-9553, Vol. 119, nr 1, s. 27-32Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present work is part of an investigation towards the development of a process route for the extraction of metal values from slag, low grade ores and other oxidic materials such as spent refractories using molten salts in the temperature range 800-950uC. The present paper focuses on the recovery of metal values, primarily Cr and Fe, from electric arc furnace slag and chromite ore. The impact of different factors to the dissolution of slag, such as temperature, holding time, flux content and weight ratio of flux/slag was studied. Based on the optimised experimental factors, the salt bath containing metal values extracted from the slag/ore was electrolysed under an applied voltage of 2·8 V. The cathode deposit was subjected to SEM/EDS and XRD analyses, which confirmed the formation of CrFe alloy. The process was also extended towards the production of CrFe alloy directly from chromite ore. The results show that the molten salt extraction process offers a promising route towards the recovery of metal values from slags and low grade ores.

  • 34.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    The salt extraction process - A novel route for metal extraction Part 2 - Cu/Fe extraction from copper oxide and sulphides2010Inngår i: Mineral Processing and Extractive Metallurgy: Transactions of the Institutions of Mining and Metallurgy: Section C, ISSN 0371-9553, E-ISSN 1743-2855, ISSN 0371-9553, Vol. 119, nr 2, s. 93-100Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present work is Part 2 of a novel salt extraction process towards the extraction of metal values from slag, low grade ores, etc. The authors describe the extraction of copper/iron from CuO, Cu 2S and CuFeS 2, which provides a green process route to treat the copper ore including both oxides and sulphides. The dissolution properties were investigated with respect to process parameters such as weight ratio of flux/copper ore and temperature. The highest extraction ratio is found at 92% in dissolution of Cu 2S, and residue of salt melt was confirmed to be mainly Al 2O 3. A cell voltage between 1·6 and 2·2 V is introduced for electrolysis, and the cathode products are proved to be pure Cu for electrolysis of CuO/Cu 2S, and Cu/Fe mixture for CuFeS 2 by X-ray diffraction and scanning electron microscopy/energy dispersive spectroscopy analysis. Some sulphur and iron chloride were found to volatilise and were deposited in the low temperature zone. Yield of copper has been estimated to be 52·3% during electrolysis of Cu 2S.

  • 35.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Xiao, S. J.
    Haarberg, G. M.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Salt extraction process-novel route for metal extraction Part 3-electrochemical behaviours of metal ions(Cr, Cu, Fe, Mg, Mn) in molten (CaCl2-)NaCl-KCl salt system2010Inngår i: Mineral Processing and Extractive Metallurgy: Transactions of the Institutions of Mining and Metallurgy: Section C, ISSN 0371-9553, E-ISSN 1743-2855, Vol. 119, nr 3, s. 163-170Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present work is Part 3 of a novel salt extraction process towards the extraction of metal values from slag, low-grade ores, etc. The electrochemical behaviour of different metal ions, Cr(III), Cr(II), Cu(II), Fe(III), Mg(II) and Mn(II) was studied using cyclic voltammetry (CV) at 827°C in (CaCl 2-)NaCl-KCl system with a tungsten or glassy carbon electrode. The deposition process of Cr(III) species was found to be consisted of two electrochemical steps, while, in the case of other species, the deposition only involves one step. The deposition potentials and diffusion coefficients were determined from the cyclic voltammetrys. Electrodeposition of chromium was performed using a two-electrode cell under constant voltage, and pure dendrite and nodular-like crystals of chromium were obtained. The present study provides a good understanding of the electrochemical behaviour of these metal ions in molten salts, and thus is helpful to this novel salt process for the recovery of metal values from slag or other materials.

  • 36.
    Hayashi, Miyuki
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Rajter, Richard
    MIT, Dept Mat Sci & Engn, Cambridge, MA 02139 USA..
    Morales, Ricardo
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Thermal diffusivities of uniaxially cold-pressed Fe2Mo powders2022Inngår i: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, Vol. 94, nr 11, s. 1179-1184Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fe2Mo powders have been produced from Fe2MoO4 powders by gas - solid reduction using pure H-2 gas at 1023 and 1173 K. The thermal diffusivity of the cold-pressed Fe2Mo powders having a relative density between 0.52 and 0.72 has been measured at room temperature both in air and in vacuum using the laser-flash method. A correlation was observed between the thermal diffusivity and the relative density for the powders reduced at different temperatures, regardless of the difference in microstructure of the powders. In order to explain the porosity dependence of the effective thermal conductivity, a new simple method developed based on the Ohm's law models was used. The model successfully simulates the experimental data, and the thermal conductivity of bulk Fe2Mo was estimated as 10.8 W/mK.

  • 37.
    Hazra, Sujan
    et al.
    Tata Steel, Jamshedpur, India.
    Pal, Snehanshu
    Department of Metallurgical and Materials Engineering, National Institute of Technology Rourkela, Odisha, India, Odisha.
    Biswajeet, Devi Dutta
    Department of Metallurgical and Materials Engineering, National Institute of Technology Rourkela, Odisha, India, Odisha.
    Sahoo, Manisha
    Tata Steel, Jamshedpur, India.
    Tarachand, Garwa Sunny
    Department of Metallurgical and Materials Engineering, National Institute of Technology Rourkela, Odisha, India, Odisha.
    Bhattacharyya, Debanjana
    Mathematics Department, National Institute of Technology Rourkela, Odisha, India, Odisha.
    Nag, Samik
    Tata Steel, Jamshedpur, India.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Optimization of high alumina slag practice in blast furnace ironmaking: an industrial approach (PART 1: fundamental aspects)2023Inngår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 50, nr 8, s. 1124-1137Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The productivity of the blast furnace Ironmaking process is significantly dependent on the slag chemistry. The presence of compounds like Al2O3 in high quantities can make the hearth slag highly viscous and difficult to tap. The objective of part-1 of this study is to provide a comprehensive analysis of the role of high alumina (Al2O3 > 15%) compositions in the blast furnace slags. Slag viscosity, liquidus temperature, activation energy, etc., are critically reviewed with respective solutions to operate under the desired conditions. Flow parameters of the slag are examined to understand the melting-softening phenomena which directly affect the slag tap-to-tap time. The addition of certain additives to the slag system has also been studied with the aim to improve the target properties of the slag. A range of slag compositions and their optimization techniques are discussed in this part to provide greater insight into the topic.

  • 38. Hu, X.
    et al.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Wang, H.
    Sundqvist Ökvist, L.
    Yang, Q.
    Björkman, B.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Carbothermic reduction of synthetic chromite with/without the addition of iron powder2016Inngår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 56, nr 12, s. 2147-2155Artikkel i tidsskrift (Fagfellevurdert)
    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).

  • 39.
    Hu, Xianfeng
    et al.
    KTH.
    Wang, H.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Direct chromium alloying by chromite ore with the presence of metallic iron2013Inngår i: Journal of Mining and Metallurgy, Section B: Metallurgy, ISSN 1450-5339, Vol. 49, nr 2, s. 207-215Artikkel i tidsskrift (Fagfellevurdert)
    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%.

  • 40.
    Hugosson, Håkan Wilhelm
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Cao, Weimin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Delin, Anna
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sulfur- and Oxygen-Induced Alterations of the Iron (001) Surface Magnetism and Work Function: A Theoretical Study2013Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 12, s. 6161-6171Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electronic structure and magnetic properties of atomic sulfur and oxygen adsorbed on the iron (001) surface are examined using density functional theory (DFT). The sulfur/oxygen coverage is considered from a quarter of one monolayer (ML) to a full monolayer. The work function change, magnetic properties, and density of states are determined and compared. We find that the work function increases with sulfur coverage in agreement with experiment. We also find that sulfur interacts strongly with the surface layer and that the magnetic moment of the Fe surface decreases as the sulfur coverage increases. In the case of oxygen adsorption, we find that the magnetic moment of the surface Fe atoms instead increases. We show that the difference in surface magnetic moment between sulfur adsorption and oxygen adsorption can be simply explained combining the Slater-Pauling rigid band model linking d-occupation and magnetic moment with an electronegativity argument. Moreover, the work function of the Fe surface as a function of oxygen coverage is found to be very sensitive to overlayer arrangement, here seen in the cases of 0.5 ML c(2 x 2) and 0.5 ML p(2 x 1). This is shown to result from large differences in the surface dipole moment change induced by the oxygen adsorption in the two different overlayer arrangements.

  • 41.
    Jelkina Albertsson, Galina
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Engström, Fredrik
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Effect of the heat treatment on the chromium partition in CaO-MgO-SiO2-Cr2O3 synthetic slags2013Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, nr 6, s. 1586-1597Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 42. Khalaghi, B.
    et al.
    Kvalheim, E.
    Tokushige, M.
    Haarberg, G. M.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Electrochemical behaviour of dissolved iron chloride in KCl+LiCl+NaCl melt at 550°C2014Inngår i: ECS Transactions, ISSN 1938-5862, E-ISSN 1938-6737, Vol. 64, nr 4, s. 301-310Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 43. Khanna, R.
    et al.
    Haq, M. Ikram-Ul
    Wang, Y.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Sahajwalla, V.
    Chemical Interactions of Alumina-Carbon Refractories with Molten Steel at 1823 K (1550 degrees C): Implications for Refractory Degradation and Steel Quality2011Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 42, nr 4, s. 677-684Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A sessile-drop study was carried out on Al(2)O(3)-10 pct C refractory substrates in contact with molten iron to investigate possible chemical reactions in the system and to determine the influence of carbon and the role, if any, played by the presence of molten iron that can act both as a reducing agent and as a metallic solvent. These investigations were carried out at 1823 K (1550 A degrees C) in argon atmosphere for times ranging between 15 minutes and 3 hours. We report the occurrence of chemical reactions in the Al(2)O(3)-10 pct C/Fe system, associated generation of CO gas, and carbon pickup by molten iron. Video images of the iron droplet started to show minor deviations after 30 minutes of contact followed by intense activity in the form of fine aluminum oxide whiskers emanating from the droplet and on the refractory substrate. The interfacial region also changed significantly over time, and the formation of small quantities of iron aluminide intermetallics was recorded after 30 minutes as a reaction product in the interfacial region. These chemical reactions also caused extensive penetration of molten iron into the refractory substrate. This study has shown that alumina cannot be treated as chemically inert at steelmaking temperatures when both carbon and molten iron are present simultaneously. These findings point to an additional reaction pathway during steelmaking that could have significant implications for refractory degradation and contamination of steel with reaction products.

  • 44. Khanna, R.
    et al.
    Sahajwalla, V.
    Simento, N.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Atomistic Monte Carlo simulations on the influence of sulphur during high-temperature decarburization of molten iron-carbon alloys2010Inngår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 58, nr 6, s. 2225-2236Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report a Monte Carlo simulation study of the molten Fe-C-S system with the aim of developing a theoretical understanding of the influence of sulphur during decarburization reactions in Fe-C alloys. Focussing specifically on the role played by free surfaces, computer simulations were based on the hexagonal atomistic model of Fe-C-S system using isotropic atomic interaction parameters; free surfaces were characterized by a missing layer of atoms. Three geometrical configurations, namely a liquid bath, a prismatic block and a spherical droplet, were investigated. Simulations were carried out as a function of melt carbon and sulphur concentration, temperatures and surface/volume ratios of the simulation cell. Sulphur atoms were found to preferentially concentrate in the top few layers, with the second layer showing the highest amounts of sulphur; very little sulphur was observed in the bulk liquid. This trend was observed in all three simulation configurations over a wide carbon/sulphur concentration range and temperatures. Significant levels of iron were observed in the top surface layer. The influence of free surfaces on atomic concentration profiles was found to be a strong function of the surface/volume ratio. The surface segregation of S was more pronounced for small exposed surfaces and was much smaller for liquids with large exposed surfaces. The presence of surface-active sulphur resulted in a major re-distribution of carbon. Carbon tended to concentrate deeper in the bulk, with the surface region being severely depleted of carbon. In addition to several new findings and a better understanding of liquid surfaces, these simulations have helped overcome major limitations of Sain and Belton's model. Key experimental results on decarburization have been explained within the framework of our simulations. These simulation results have significant implications for surface decarburization reactions and carbon-boil phenomena in smelting technologies.

  • 45. Khanna, Rita
    et al.
    Ikram-Ul-Haq, Muhammad
    Sadi, Seyed Fahandej
    Sahajwalla, Veena
    Mukherjee, Partho Sarathy
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Reduction Reactions in Al2O3-C-Fe and Al2O3-Fe2O3-C Systems at 1 823 K2014Inngår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 54, nr 7, s. 1485-1490Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    With a view to produce Fe-Al alloys for deoxidation during steel refining, chemical reactions were investigated in Al2O3-C-Fe and Al2O3-Fe2O3-C systems at 1 823 K. Using a horizontal tube furnace and argon atmosphere, interactions were investigated for time periods up to 2 hours. Two sets of blends were prepared from initial constituents, which were later used to prepare two types of substrates. Alumina and synthetic graphite powders were blended in a 70: 30 proportion (blend l), and in the second set, Fe2O3 was blended with C in a proportion of 75:25 (blend II). In one case, blend I was mixed thoroughly with iron powder (Fe (2.7 pct C)) in a ratio of 80:20; in the second case, blend I was mixed with blend II in the ratio of 70:30. We report significant reduction reactions in both cases. SEM/EDS studies on the Al2O3-C-Fe system showed unambiguous evidence for the pick-up of aluminium by molten iron after 1 hour. Levels of aluminium in molten iron were found to increase significantly with time. Due to in-situ reduction of Fe2O3, the generation of CO gas and associated turbulence, the reactions were quite fast in the Al2O3Fe2O3-C system. X-ray diffraction studies showed the presence of additional diffraction peaks belonging to Fe(3)AIC and Fe(3)AI systems. Molten iron was found to act as a reducing agent and a metallic solvent in both cases. This study provides evidence for the carbothermic reduction of alumina at 1 823 K and for the formation of ferroalloys directly from mixed oxides of aluminium and iron.

  • 46. Khanna, Rita
    et al.
    Ikram-Ul-Haq, Muhammad
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sahajwalla, Veena
    Carbothermic Reduction of Alumina at 1 823 K: On the Role of Molten Iron and Reaction Mechanisms2016Inngår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 56, nr 7, s. 1300-1302Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A possible reaction mechanism is presented for the low temperature carbothermic reduction of alumina in the presence of molten iron under inert conditions. This reduction was found to take place in a number of stages that involved the carburization of molten iron, disintegration of alumina into sub -oxide gases, reduction of these gases by the solute carbon followed by the capture of reduced aluminum by molten iron due to its high affinity. With increasing levels of aluminum in the iron, the wettability of alumina with molten metal undergoes a transition from poor wetting (with Fe) to good wetting (with Fe-Al-C) leading to the dissolution and subsequent reduction of alumina in the Fe -Al -C melt. These reaction steps were observed to occur in Al2O3-Fe2O3-C system at 1 823 K and atmospheric pressure.

  • 47.
    Khanna, Rita
    et al.
    Univ New S Wales, Sydney, NSW, Australia.
    Kongkarat, Somyote
    Univ New S Wales, Sydney, NSW, Australia.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sahajwalla, Veena
    Univ New S Wales, Sydney, NSW, Australia.
    Carbothermic Reduction of Alumina at 1 823 K in the Presence of Molten Steel: a Sessile Drop Investigation2012Inngår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 52, nr 6, s. 992-999Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The carbothermic reduction of alumina was investigated at 1 823 K in the presence of molten steel in argon atmosphere for time periods up to 6 hours. A sessile-drop study was carried out to investigate the influence of operating parameters such as carbon/alumina ratio in the substrate, solute carbon level in the melt and reaction time. With molten steel acting both as a reducing agent and a metallic solvent, we report significant reduction reactions in the Al2O3-22.82 pct C/Fe (0.6 pct C) system, associated generation of CO gas and carbon pick-up by molten steel. The refractory substrate thickness was seen to decrease with time and the metal droplet started to flatten out and spread over the substrate after 5.5 hours. The chemical composition of metal deposited on the substrate was determined to be iron-aluminide; small levels of unreduced alumina and residual carbon were also observed. The carbon level in the metal droplet increased steadily to 1.5 wt pct during initial 3 hours and then decreased to 0.6 wt pct after 6 hours indicating carbon consumption; a small step increase in CO gas generation was also observed after 5.5 hours. While the metal droplet was still predominantly iron after 5 hours, it had completely transformed to iron aluminide after 6 hours of contact. The molten metal was also seen to penetrate deep in the substrate. These experimental results provide unambiguous evidence for a macroscopic carbothermic reduction of alumina occurring at 1 823 K in the presence of molten steel and for the dissolution of product aluminium in molten steel.

  • 48.
    Kiamehr, Saeed
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Ahmed, Hesham
    Viswanathan, Nurni
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Changes in Effective Thermal Conductivity During the Carbothermic Reduction of Magnetite Using Graphite2017Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, nr 3, s. 1502-1513Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Knowledge of the effective thermal diffusivity changes of systems undergoing reactions where heat transfer plays an important role in the reaction kinetics is essential for process understanding and control. Carbothermic reduction process of magnetite containing composites is a typical example of such systems. The reduction process in this case is highly endothermic and hence, the overall rate of the reaction is greatly influenced by the heat transfer through composite compact. Using Laser-Flash method, the change of effective thermal diffusivity of magnetite-graphite composite pellet was monitored in the dynamic mode over a pre-defined thermal cycle (heating at the rate of 7 K/min to 1423 K (1150 A degrees C), holding the sample for 270 minutes at this temperature and then cooling it down to the room temperature at the same rate as heating). These measurements were supplemented by Thermogravimetric Analysis under comparable experimental conditions as well as quenching tests of the samples in order to combine the impact of various factors such as sample dilatations and changes in apparent density on the progress of the reaction. The present results show that monitoring thermal diffusivity changes during the course of reduction would be a very useful tool in a total understanding of the underlying physicochemical phenomena. At the end, effort is made to estimate the apparent thermal conductivity values based on the measured thermal diffusivity and dilatations.

  • 49. Korobeinikov, I
    et al.
    Chikhi, N
    Fouquart, P
    Turquais, B
    Delacroix, J
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Volkova, O
    Surface Tension and Density of Cr–Mn–Ni Steels with Transformation Induced Plasticity Effect2020Inngår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344XArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermophysical properties of liquid metal alloys play a crucial role in the variety of processes. Present work reports experimental investigations of two new transformation induced plasticity (TRIP) steels. A classical maximum bubble pressure technique is successfully used to measure surface tension and density of the liquid TRIP-steel samples in the temperatures range of 1500–1800 °C. Experiments are performed in two different measurement cells from TU Freiberg and Commissariat a l'Energie Atomique (CEA), Cadarache. Capillaries are made of zirconia partially stabilized with yttrium oxide, and the samples are molten in Al2O3 crucibles. Measurements are conducted under the argon atmosphere. Surface tension of the investigated samples rises up to 1700 °C and further remains the same. Density of the new steels obtained in this study is in good agreement with the previously reported values for Fe–Cr alloys with similar Cr content. Density of the alloy is estimated as 875 488–11 885 × T (±218.85 kg m−3) for a 15%Cr alloy and 796 042–06 897 × T (±199 kg m−3) for a 19%Cr alloy. 

  • 50. Korobeinikov, I.
    et al.
    Endo, R.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Volkova, O.
    Density of Liquid Manganese Measured Using the Maximum Bubble Pressure Method2021Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 52, nr 2, s. 571-575Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Manganese is an important metal for steelmaking. Data on the density of the metal are scarce and show considerable scatter. Present work reports the density of the liquid manganese in the range of 1535 K to 1836 K estimated for the first time with the use of the maximum bubble pressure technique. The obtained density of the manganese is marginally higher than previously reported in the literature.

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