Change search
Refine search result
123456 1 - 50 of 298
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Abas, R. Abdul
    et al.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Thermal diffusivity of sintered stainless steel-alumina composites2006In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 4, p. 513-518Article in journal (Refereed)
    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.

  • 2. Abbasalizadeh, A.
    et al.
    Sridar, S.
    Chen, Z.
    Sluiter, M.
    Yang, Y.
    Sietsma, J.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Hari Kumar, K. C.
    Experimental investigation and thermodynamic modelling of LiF-NdF3-DyF3 system2018In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 753, p. 388-394Article in journal (Refereed)
    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.

  • 3. 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.

  • 4. Abbasalizadeh, Aida
    et al.
    Malfliet, Annelies
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sietsma, Jilt
    Yang, Yongxiang
    Electrochemical Extraction of Rare Earth Metals in Molten Fluorides: Conversion of Rare Earth Oxides into Rare Earth Fluorides Using Fluoride Additives2017In: JOURNAL OF SUSTAINABLE METALLURGY, ISSN 2199-3823, Vol. 3, no 3, p. 627-637Article in journal (Refereed)
    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.

  • 5. Abbasalizadeh, Aida
    et al.
    Malfliet, Annelies
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sietsma, Jilt
    Yang, Yongxiang
    Electrochemical Recovery of Rare Earth Elements from Magnets: Conversion of Rare Earth Based Metals into Rare Earth Fluorides in Molten Salts2017In: Materials transactions, ISSN 1345-9678, E-ISSN 1347-5320, Vol. 58, no 3, p. 400-405Article in journal (Refereed)
    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.

  • 6.
    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.

  • 7. Abbasalizadeh, Aida
    et al.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Venkatesan, Prakash
    Sietsma, Jilt
    Yang, Yongxiang
    Novel Reactive Anode for Electrochemical Extraction of Rare Earth Metals from Rare Earth Oxides2017In: RARE METAL TECHNOLOGY 2017 / [ed] Kim, H Alam, S Neelameggham, NR Oosterhof, H Ouchi, T Guan, X, SPRINGER INTERNATIONAL PUBLISHING AG , 2017, p. 87-92Conference paper (Refereed)
    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.

  • 8.
    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.

  • 9.
    Abdul Abas, Riad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Hayashi, M.iyuki
    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.
    Thermal Diffusivity measurement of CMSX-4 alloy by Laser flash method2007In: International journal of thermophysics, ISSN 0195-928X, E-ISSN 1572-9567, Vol. 28, no 1, p. 109-122Article in journal (Refereed)
    Abstract [en]

    In the present work, thermal diffusivity measurements have been carried out on industrial samples of CMSX-4 nickel-base superalloy using the laser-flash method with emphasis on studying the effect of temperature and microstructure on the thermal diffusivity. The measurements were performed in the temperature range from 298 to 1623 K covering both solid as well as liquid ranges. Below 1253 K, the thermal-diffusivity values were found to increase with increasing temperature. Microstructural investigations of quenched samples revealed that below 1253 K, an ordered phase, usually referred to as the -phase was present together with the disordered fcc phase, often referred to as the γ phase. Between 1253 K and the solidus temperature, the phase was found to dissolve in the matrix alloy causing an increase in the disordering of the alloy, and thereby a small decrease in the thermal-diffusivity values. The thermal-diffusivity values of samples pre-annealed at 1573 K exhibited constancy in the temperature range from 1277 to 1513 K, which is attributed to the attainment of thermodynamic equilibrium. These equilibrium values were found to be lower than the results for samples not subjected to annealing. The thermal-diffusivity values of the alloy in the liquid state were found to be independent of temperature.

  • 10.
    Abdul Abas, Riad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Hayashi, Miyuki
    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.
    Thermal Diffusivity Measurements of some Industrially Important Alloys by a Laser Flash Method2007In: International journal of materials reseach, ISSN 1862-5282, Vol. 98, no 6, p. 535-540Article in journal (Refereed)
    Abstract [en]

    In the present work, thermal diffusivity measurements of three industrially significant alloys, viz. 90Ti.6Al.4V, stainless steel with 25Cr and 6Ni as well as plain carbon steel with 0.7 % carbon have been carried out as a function of temperature. The aim of this work is to study the effect of temperature and microstructure on the thermal diffusivities of these alloys. For the 90Ti.6Al.4V alloy, thermal diffusivity increases with temperature below 1225 K. Above this temperature, the values started decreasing probably due to the dissolution of Ti3Al intermediate phase in the matrix, which would result in an increase in the disorder of the structure. For 25Cr: 6Ni stainless steel, the thermal diffusivity is nearly constant up to about 700 K. Above this, there is an increase in the thermal diffusivities with temperature during the heating cycle, which was reproducible during thermal cycling. On the other hand, the slope of the curve increases above 950 K.

    In the case of the 0.7 % carbon steel, the thermal diffusivity shows a decreasing trend with temperature below the Curie point for the alloy, where the alloy consists of bcc + fcc phases. Above this point, only the fcc phase is prevalent and the thermal diffusivity was found to increase with temperature. Heat transfer is carried out by lattice vibration (phonons) as well as electrons. The contribution of electrons varies depending upon the type of alloy. In this study, the highest electron contribution was found in 0.7 % carbon steel, while the lowest was in stainless steel. The thermal conductivity values of these alloys are in good agreement with the calculated values using the model proposed by Mills.

  • 11.
    Abdul Abas, Riad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jakobsson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Hayashi, Miyuki
    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.
    Studies on Graphitisation of Blast Furnace Coke by X-ray Diffraction Analysis and Thermal Diffusivity Measurements2005In: Steel research, ISSN 0177-4832, Vol. 77, no 11, p. 763-769Article in journal (Refereed)
    Abstract [en]

    High temperature XRD and thermal diffusivity experiments were employed to investigate the degree of graphitisation in blast furnace coke. The experiments were conducted between room temperature and 1473 K. X-ray diffraction studies were carried out in order to monitor the degree of graphitisation in the coke samples from the same campaign. In these cases, the degree of graphitisation was followed by the changes in the vertical dimension. The degree of graphitisation was found to be dependent on temperature. On the other hand, the graphitisation at each temperature was instantaneous, even at as low a temperature as 973 K and no dependency on time could be noticed. The thermal diffusivities of the coke samples taken from deeper level of the experimental blast furnace were measured using the laser-flash technique. The results from these measurements showed that thermal diffusivities increased with the degree of graphitisation, which in turn, can be affected by the level in the blast furnace at which the coke sample was taken. The present results indicate that the degree of graphitisation as followed by X-ray diffraction analysis as well as thermal diffusivities can be used to trace the thermal history of coke. DSC measurements show that the heat capacity of the coke increases with temperature towards the heat capacity of graphite, which could be due to the increasing the graphitisation degree of the coke.

  • 12.
    Abdul Abas, Riad
    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.
    Thermal Diffusivity of Sintered Stainless steel-Alumina Composite2006In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 4, p. 513-518Article in journal (Refereed)
    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.

  • 13. 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 Metals2016Conference paper (Refereed)
    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.

  • 14.
    Ahmed, Hesham M.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    El-Geassy, A. H. A.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Kinetics of Reduction of NiO-WO3 Mixtures by Hydrogen2010In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 1, p. 161-172Article in journal (Refereed)
    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.

  • 15.
    Ahmed, Hesham M.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    El-Geassy, Abdel-Hady A.
    Viswanathan, Nurni Neelakantan
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Kinetics and Mathematical Modeling of Hydrogen Reduction of NiO-WO(3) Precursors in Fluidized Bed Reactor2011In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, no 9, p. 1383-1391Article in journal (Refereed)
    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.

  • 16.
    Ahmed, Hesham M.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    El-Geassy, Abdel-Hady
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Kinetic Studies of the Hydrogen Reduction of NiO-WO3 precursors in a Fluidized-bed reactorIn: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916Article in journal (Other academic)
  • 17.
    Ahmed, Hesham M.
    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.
    Isothermal dynamic thermal diffusivity studies of the reduction of NiO and NiWO(4) precursors by hydrogen2011In: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, Vol. 102, no 11, p. 1336-1344Article in journal (Refereed)
    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.

  • 18.
    Ahmed, Hesham M.
    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.
    Reduction-Carburization of NiO-WO3 Under Isothermal Conditions Using H2-CH4 Gas Mixture2010In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 1, p. 173-181Article in journal (Refereed)
    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.

  • 19.
    Ahmed, Hesham M.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Viswanathan, N. N.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    On The Kinetics of Hydrogen Reduction of NiO-WO3 Precursors in Fluidized Bed- A Modeling Approach2011In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, no 9, p. 1383-1391Article in journal (Refereed)
    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.

  • 20.
    Ahmed, Hesham M.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Viswanathan, Nurini N.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Dynamic Thermal Diffusivity Measurements - A Tool for Studying Gas-Solid Reactions2011In: DIFFUSION IN SOLIDS AND LIQUIDS VI, PTS 1 AND 2, 2011, p. 217-222Conference paper (Refereed)
    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.

  • 21.
    Ahmed, Hesham
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mis, Michal
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    El-Geassy, Abdel-Hady
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seethararnan, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Reduction-Carburization of the Oxides of Ni and W Towards the Synthesis of Ni-W-C Carbides2010In: ADVANCED MATERIALS FORUM V, PT 1 AND 2  / [ed] Rosa LG; Margarido F, 2010, Vol. 636-637, p. 952-962Conference paper (Refereed)
    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.

  • 22. Ahmed, Hesham
    et al.
    Morales-Estrella, R.
    Viswanathan, Nurin
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Gas-Solid Reaction Route toward the Production of Intermetallics from Their Corresponding Oxide Mixtures2016In: METALS, ISSN 2075-4701, Vol. 6, no 8, article id 190Article in journal (Refereed)
    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.

  • 23.
    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.

  • 24. Andersson, G.
    et al.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    "Steel eco-cycle" - A Swedish cross-pollination environmental research program2013In: Materials Science and Technology Conference and Exhibition 2013, MS and T 2013, Warrendale , 2013, p. 1784-1791Conference paper (Refereed)
    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.

  • 25. Arvanitidis, I.
    et al.
    Kapilashrami, A.
    Du, S. C.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    Intrinsic reduction kinetics of cobalt- and nickel-titanates by hydrogen2000In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 15, no 2, p. 338-346Article in journal (Refereed)
    Abstract [en]

    The isothermal reduction of synthetic CoTiO3 and NiTiO3 in hydrogen (1 atm) was investigated using thermogravimetric analysis technique in the temperature range, 928-1287 K (CoTiO3) and 884-1387 K (NiTiO3). Shallow beds of fine titanate powders were reduced by hydrogen at a high flow rate. Quenched samples were analyzed by scanning electron microscopy. The rates of the reaction of the titanates with H-2 were very fast during the reduction of Co2+, Ni2+, or Fe2+ ions into metals. The reduction of the remaining titanium oxide was very slow. The activation energy for the reduction of CoTiO3 by hydrogen to Co and TiO2 was evaluated to be 151 +/- 1 kJ/mol, and the activation energy for the reduction of NiTiO3 by hydrogen to Ni and TiO2 was evaluated to be 153 +/- 1 kJ/mol. The study was complemented by hydrogen reduction of synthetic TiO2 (rutile). The results were also compared with the hydrogen reduction of FeTiO3.

  • 26.
    Aune, Ragnhild E.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Battezzati, L.
    Egry, I.
    Etay, J.
    Fecht, H. J.
    Giuranno, D.
    Novakovic, R.
    Passerone, A.
    Ricci, E.
    Schmidt-Hohagen, F.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Wunderlich, R.
    Surface tension measurements of Al-Ni based alloys from ground-based and parabolic flight experiments: Results from the ThermoLab project2006In: Microgravity, science and technology, ISSN 0938-0108, E-ISSN 1875-0494, Vol. 18, no 3-4, p. 73-76Article in journal (Refereed)
    Abstract [en]

    Surface tension measurements of different alloys of the Al-Ni system, performed both under reduced gravity conditions in parabolic flights and on ground by conventional techniques, are presented. The alloys compositions were selected on the basis of the intrinsic compound forming tendency with the aim to allow a sensitive test of model predictions.

  • 27.
    Aune, Ragnhild E.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Battezzati, Livio
    Brooks, Rob
    Egry, Ivan
    Fecht, Hans-Joerg
    Garandet, Jean-Paul
    Mills, Ken C.
    Passerone, Alberto
    Quested, Peter N.
    Ricci, Enrica
    Schneider, Stephan
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wunderlich, Rainer K.
    Vinet, Bernard
    Measurement of Thermophysical Properties of Liquid Metallic Alloys in a Ground- and Microgravity Based Research Programme - the ThermoLab Project2005In: Microgravity, science and technology, ISSN 0938-0108, E-ISSN 1875-0494, Vol. 16, no 1-4, p. 7-10Article in journal (Refereed)
    Abstract [en]

    The ThermoLab project is concerned with the measurement of the thermophysical properties of industrial alloys in the liquid phase. The project combines long and short duration microgravity measurements based on containerless processing with an electromagnetic levitation device and a ground based experimental programme using conventional and containerless processing techniques. An overview of the project and representative results from the ground based experimental programme are given. Alloys investigated included Ni-based, Fe-based, a Cu-Sn-Mg alloy and a gamma-TiAl alloy.

  • 28.
    Aune, Ragnhild E.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Battezzati, Livio
    Brooks, Rob
    Egry, Ivan
    Fecht, Hans-Joerg
    Garandet, Jean-Paul
    Mills, Ken C.
    Passerone, Alberto
    Quested, Peter N.
    Ricci, Enrica
    Schneider, Stephan
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wunderlich, Rainer K.
    Vinet, Bernard
    Surface Tension and Viscosity of Industrial Alloys from Parabolic Flight Experiments: Results of the ThermoLab Project2005In: Microgravity, science and technology, ISSN 0938-0108, E-ISSN 1875-0494, Vol. 16, no 1-4, p. 11-14Article in journal (Refereed)
    Abstract [en]

    The surface tension and the viscosity of a series of industrial alloys have been measured by the oscillating drop technique with an electromagnetic levitation device under reduced gravity conditions in several parabolic flights. It was demonstrated that the 20 seconds of reduced gravity available in a parabola were sufficient for melting, heating into the liquid phase, and cooling to solidification of typically 7 mm diameter metallic specimen. The surface tension and the viscosity were obtained from the frequency and the damping time constant of the oscillation which were evaluated from the temperature signal of a highresolution pyrometer. Alloys processed included steels, Ni-based superalloys, and Ti-alloys which were supplied by industrial partners to the project. Three to four parabolas were sufficient to obtain the surface tension and the viscosity over a large range in temperature.

  • 29.
    Aune, Ragnhild E.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Battezzati, Livio
    Brooks, Robert
    Egry, Ivan
    Fecht, Hans-Joerg
    Garandet, Jean-Paul
    Hayashi, Miyuki
    Mills, Ken C.
    Passerone, Alberto
    Quested, Peter N.
    Ricci, Enrica
    Schmidt-Hohagen, Frank
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Vinet, Bernard
    Wunderlich, Rainer K.
    Thermophysical properties of IN738lc, MM247lc and CMSX-4 in the liquid and high temperature solid phase2005In: Superalloys 718, 625, 706 and Derivatives, Proceedings, 2005, p. 467-476Conference paper (Refereed)
    Abstract [en]

    Thermophysical properties of the Ni-based superalloys CMSX-4, IN738LC, and MM247LC have been measured in the liquid and high-temperature solid phase. Properties included calorimetric, thermal transport, the surface tension, and the viscosity. Experiments have been performed in ground-based laboratory using classical calorimetry and rheometry as well as under reduced gravity conditions in an electromagnetic levitation device on board parabolic flights. In this contribution, an overview of the various properties of three Ni-based superalloys is given with emphasis on the surface tension and viscosity as obtained from the parabolic flight experiments. The measurements were performed within a program called ThermoLab dedicated to the measurement of thermophysical properties of industrial alloys.

  • 30.
    Aune, Ragnhild E.
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Hayashi, M.
    Nakajima, K.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    Thermophysical properties of silicate slags2002In: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 54, no 11, p. 62-69Article in journal (Refereed)
    Abstract [en]

    The optimization of metallurgical processes requires reliable data of the slag phase. This paper focuses on three properties that are relevant to heat and mass-transfer calculations-viscosities, thermal diffusivities, and surface tensions of silicate melts. A brief account of the experimental techniques used for the measurements of these properties, with special reference to the work carried out in the Division of Metallurgy, Royal Institute Of Technology, Stockholm, Sweden, are presented, along with the advantages and limitations. As these properties are structure-oriented, the impact of structure on these properties is also presented. The paper is intended as a state-of-the-art review of the subject.

  • 31.
    Aune, Ragnhild, E
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Jacob, K.T
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    Thermodynamic Data of the Rare Earth Sesquioxides1996Report (Other (popular science, discussion, etc.))
  • 32.
    Aune, Ragnhild, E
    et al.
    KTH, Superseded Departments, Metallurgy.
    Seetharaman, Seshadri
    KTH.
    Experimental studies of heat capacities of Nd2Fe17, Nd2Fe17N1.49 and Nd2Fe17N1.75 alloys in the temperature range 273-773 K1998In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 17, no 4, p. 299-311Article in journal (Refereed)
  • 33.
    Aune, Ragnhild, E
    et al.
    KTH, Superseded Departments, Metallurgy.
    Sichen, Du
    KTH.
    Seetharaman, Seshadri
    Phase Relationships in the System Mn-Co-C1997In: The Japan Society of Calorimetry and Thermal Analysis - Netsu Sokutei, Vol. 24, no 4, p. 171-178Article in journal (Refereed)
  • 34.
    Aune, Ragnhild Elizabeth
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Experimental designs toward an understanding of process phenomena in steelmaking2006In: Iron and Steel Technology, ISSN 1547-0423, Vol. 3, no 12, p. 137-146Article in journal (Refereed)
    Abstract [en]

    Various experimental studies towards the understanding of different process phenomena in iron and steelmaking were presented. Thermal diffusivity measurement was carried out at various temperature to monitor the structural changes occurring in coke. X-ray diffraction measurements were carried out to determine the average crystallite size of graphite along the structural c-axis and in the structural ab plane. It was observed that the apparent thermal diffusivity during the cooling cycle is larger than the heating cycle. Many experiments were also conducted in a high-temperature x-ray diffraction unit, to study the rate of graphitization at any given temperature for a given coke sample. An experimental design for the investigation of the mechanism of reduction in the blast furnace shaft, and the role of coke by dynamic x-ray photography was also carried out. The heating and melting of a mold flux during continuous casting were also simulated in specially designed laboratory.

  • 35.
    Aune, Ragnhild Elizabeth
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Experimental designs towards an understanding of process phenomena in steel making2005In: ICS 2005: Proceedings of the 3rd International Congress on the Science and Technology of Steelmaking, 2005, p. 381-392Conference paper (Refereed)
  • 36.
    Aune, Ragnhild Elizabeth
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Experimental Designs towards an Understanding of Process Phenomena in Steel Making2006In: Iron & Steel Technology, ISSN 1547-0423, Vol. 3, no 12, p. 137-146Article in journal (Refereed)
  • 37.
    Aune, Ragnhild Elizabeth
    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.
    Thermodynamic Aspects of Metals Processing2005In: Fundamentals of Metallurgy / [ed] Seshadri Seetharaman, Woodhead Publishing Limited, 2005, p. 38-81Chapter in book (Refereed)
  • 38. Basu, S.
    et al.
    Lahiri, A. K.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Activity of Ferric Oxide in Steelmaking Slag2010In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 2, p. 414-419Article in journal (Refereed)
    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.

  • 39. Basu, S.
    et al.
    Lahiri, A. K.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Activity of iron oxide in steelmaking slag2008In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 39, no 3, p. 447-456Article in journal (Refereed)
    Abstract [en]

    Most refining reactions in steelmaking involve oxidation of impurity element(s). The product(s) of oxidation either dissolve in the slag or escape as gaseous phase. The activities of oxygen in the metal (h (O)), and that of "FeO" in slag (a (FeO)), are major factors controlling these chemical reactions. The activities of oxygen and "FeO" are thermodynamically related, provided equilibrium distribution of oxygen between the slag and the metal is attained. This enables direct estimation of one parameter from the other. A thorough knowledge of the variation in activity of FeO, and factors affecting the same, is therefore of great importance in the process metallurgy of steelmaking. The present work experimentally measures the activity of FeO in steelmaking slags and attempts to develop a correlation for estimation of gamma(FeO) as a function of temperature and chemical composition of the slag.

  • 40. Basu, S.
    et al.
    Lahiri, A. K.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Distribution of phosphorus and oxygen between liquid steel and basic oxygen steelmaking slag2008In: Proc. ICS 2008: The 4th Int. Congress Sci. Technol. Steelmaking, 2008, p. 594-597Conference paper (Refereed)
  • 41. Basu, S.
    et al.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Lahiri, A. K.
    Thermodynamics of Phosphorus and Sulphur Removal during Basic Oxygen Steelmaking2010In: STEEL RESEARCH INTERNATIONAL    , 2010, Vol. 81, no 11, p. 932-939Conference paper (Refereed)
    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.

  • 42.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    A model for activity coefficient of P2O5 in BOF slag and phosphorus distribution between liquid steel and slag2007In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 47, no 8, p. 1236-1238Article in journal (Refereed)
  • 43.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    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.
    Distribution of phosphorus and oxygen between liquid steel and basic oxygen steelmaking slag2009In: Revue de métallurgie (Imprimé), ISSN 0035-1563, E-ISSN 1156-3141, Vol. 106, no 1, p. 21-+Article in journal (Refereed)
    Abstract [en]

    The efficiency of dephosphorisation is governed by the thermodynamic behaviour of phosphorus and oxygen in molten metal, and P2O5 and FeO in slag. The equilibrium distribution of phosphorus and oxygen, for a wide range of chemical compositions simulating the evolution of slag composition during a typical BOF blow, has been experimentally determined. A mathematical model for estimation of the activity coefficients, as a function of the chemical composition, was also attempted.

  • 44.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Phosphorus partition between liquid steel and CaO-SiO2-FeOx-P2O5-MgO slag containing 15-25 %FeO2007In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 38, no 4, p. 623-630Article in journal (Refereed)
    Abstract [en]

    CaO-SiO2-FeO2-P2O5-MgO bearing slags are typically used in the basic oxygen steelmaking (BOS) process. The partition ratio of phosphorus between slag and steel is an index of the phosphorus holding capacity of the slag, which determines the phosphorus content achievable in the finished steel. The influence of factors such as FeO content and basicity on the phosphorus partition ratio was investigated at two different temperatures. The partition ratio initially increased with basicity but remained constant beyond a basicity of 2.5 to 2.6. An increase in the FeO content up to 18 to 20 mass pct was beneficial for the phosphorus partition at a basicity level of 2 to 3, but a higher concentration of FeO resulted in a decrease in the phosphorus partition ratio; the FeO concentration corresponding to this transition varied with basicity and temperature. At even lower basicities, however, the equilibrium phosphorus partition showed either no change, or a marginally decreasing trend, with an increase in the FeO content.

  • 45.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    KTH.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Phosphorus partition between liquid steel and CaO-SiO2-P2O5-MgO slag containing low FeO2007In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 38, no 3, p. 357-366Article in journal (Refereed)
    Abstract [en]

    CaO-SiO2-FeOx-P2O5-MgO bearing slags are typical in the basic oxygen steelmaking (BOS) process. The partition ratio of phosphorus between slag and steel is an index of the phosphorus holding capacity of the slag, which determines the phosphorus content achievable in the finished steel. The influences of FeO concentration and basicity on the equilibrium phosphorus partition ratios were experimentally determined at temperatures of 1873 and 1923 K, for conditions of MgO saturation. The partition ratio initially increased with basicity but attained a constant value beyond basicity of 2.5. An increase in FeO concentration up to approximately 13 to 14 mass pet was beneficial for phosphorus partition.

  • 46.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    KTH.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Halder, Jayanta
    Change in phosphorus partition during blowing in a commercial BOF2007In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 47, no 5, p. 766-768Article in journal (Refereed)
  • 47. Bjorkvall, J.
    et al.
    Du, S. C.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    Thermodynamic description of Al2O3-CaO-MnO and Al2O3-FeO-MnO melts - a model approach2000In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 24, no 3, p. 353-376Article in journal (Refereed)
    Abstract [en]

    Assessments for the binary systems. Al2O3-CaO, Al2O3-FeO and Al2O3-MnO were carried out using a slag model developed at the present department. Calculations of the oxide activities in the homogenous liquid phase have been performed for the Al2O3-CaO-MnO and Al2O3-FeO-MnO systems, The activities in the ternary systems were calculated using the parameters obtained from the binary subsystems. Comparison between experimental data and the model calculations demonstrates the ability of the model to describe the thermodynamics of ternary systems using only information ti-om the binary systems. In the case of the Al2O3-CaO-MnO system, the comparison between model calculations and the results of the only available experimental measurements is less satisfactory. This could partly be attributed to the non availability of experimental data for the subsystem CaO-MnO. Future experimentation in the Al2O3-CaO-MnO system is strongly recommended.

  • 48. Bjorkvall, J.
    et al.
    Du, S. C.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    Thermodynamic description of 'FeO'-MgO-SiO2 and 'FeO'-MnO-SiO2 melts - a model approach2000In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 19, no 1, p. 49-59Article in journal (Refereed)
    Abstract [en]

    Activities of the oxide components in the 'FeO'-MgO-SiO2 and 'FeO'-MnO-SiO2 systems have been predicted based on the information of binary systems using a thermodynamic model. The model considers the ionic melt as an oxygen-ion matrix with the cations including Si4+ distributed in it. The interactions between different cations in the presence of O2- are considered as functions of both composition and temperature. The activities predicted by the model are in good agreement with the experimental data available in the literature.

  • 49. Bjorkvall, J.
    et al.
    Du, S. C.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    Thermodynamic model calculations in multicomponent liquid silicate systems2001In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 28, no 3, p. 250-257Article in journal (Refereed)
    Abstract [en]

    A thermodynamic model developed earlier in the present laboratory for oxidic melts was applied to some multicomponent systems, namely CaO-FeO-MgO-SiO2, Al2O3-CaO-MgO-SiO2, Al2O3-FeO-MnO-SiO2, and Al2O3-CaO-FeO-MgO-MnO-SiO2. Model calculations were carried out using only the parameters corresponding to the binary systems, which, in turn, were based on the available thermodynamic information for these systems. The predicted thermodynamic activities of the component oxides in higher order systems were compared with the experimental data published in the literature. In general, the agreement between the model predictions and the experimental values was found to be satisfactory within the limits of experimental uncertainties and limitations of the model calculations. Examples of model predictions for some typical slag compositions, relevant to the Swedish steel industry and used in the blast furnace, electric arc furnace, and ladle furnace are also presented.

  • 50. Bjorkvall, J.
    et al.
    Du, S. C.
    Stolyarova, V.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    A model description of the thermochemical properties of multicomponent slags and its application to slag viscosities2001In: Glass Physics and Chemistry, ISSN 1087-6596, E-ISSN 1608-313X, Vol. 27, no 2, p. 132-147Article in journal (Refereed)
    Abstract [en]

    In view of the urgent need for an extrapolation of the thermochemical and thermophysical properties of multicomponent metallurgical slags, a semiempirical slag model has been developed at the Department of Metallurgy, Royal Institute of Technology, Stockholm. In this model, Temkin's description of ionic melts is coupled with Lumsden's total dissociation of polymerized silicate and aluminate species. The excess Gibbs energies are described by means of Redlich-Kister polynomials. The model parameters that correspond to binary silicate systems are generated from available experimental data and used consequently to describe systems of higher order. The model is successful in extrapolating the thermodynamic data for a number of ternary and higher-order silicate systems. in view of the uncertainties in the literature data in the case of the Al2O3-SiO2 system. Knudsen cell mass spectrometric measurements are conducted and the model parameters are assigned on the basis of these results. This enables reasonable predictions of the thermodynamic properties of multicomponent aluminosilicate slags. The model description is also used in linking thermodynamic data with slag Viscosities. The viscosities of ternary silicates could be predicted from the binary viscosities and the thermodynamic data.

123456 1 - 50 of 298
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf