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  • 101. Kapilashrami, A.
    et al.
    Lahiri, A. K.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Bubble formation through reaction at liquid-liquid interfaces2005In: Steel Research International, ISSN 1611-3683, Vol. 76, no 9, p. 616-623Article in journal (Refereed)
    Abstract [en]

    Slag foaming is an important phenomenon in steelmaking processes with both beneficial as well as negative effects. The present work is part of the wider project on the modelling of slag foaming, with special reference to dynamic conditions. Since bubble formation is the first step to foam formation, the present work was carried out in an attempt to simulate the bubble formation in slag/metal reactions in steelmaking processes by water-modelling experiments. The bubble formation due to the gas produced through chemical reaction at the interface between oleic acid and sodium bicarbonate solution was systematically monitored. The chemical reaction rate was varied by varying the concentration of sodium bicarbonate. The bubbles were observed to be generated in the heavier aqueous phase just below the water-oil interface. The bubbles penetrated the interface and escaped through the oil phase. The rate of the reaction was estimated from the volume of the gas that passed the water/oil interface. It was observed that the bubble formation and bubble growth mechanism were influenced by the reaction rate while the bubble size seemed to be unaffected by the reaction rate.

  • 102. Kapilashrami, Abha
    et al.
    Görnerup, Mårten
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Lahiri, A. K.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Bubble formation and dynamic slag foaming phenomena2006In: 2006 TMS Fall Extraction and Processing Division: Sohn International Symposium, 2006, p. 233-245Conference paper (Refereed)
    Abstract [en]

    Slag foaming proves to be both blessing and curse for the process productivity, depending on where in the process it occurs. In pyrometallurgical processes, slag foaming is often a result of chemical reactions taking place in the slag. As the slag composition and reaction rates are changing, foaming occurs under dynamic conditions. In the present work, slag foaming was studied with XRF. The foam displayed a fluctuating behaviour, unaccountable by existing models. The concept of foaming index was found not to be satisfactory in describing the foam, resulting in the need for alternative theories. The rate of fluctuations was seen to be related to the difference between rate of gas generation and rate of gas escape from the system (Ug-Ue) as well as the bubble sizes. Thus, model development of dynamic foaming phenomenon has to take the effective chemical reaction rate as well as the bubble sizes into consideration. The first step in obtaining foam is to form bubbles. In the present work, gas bubbles were generated through chemical reaction at interface between two immiscible liquids and the bubble formation was studied optically. The gas bubble size was seen to be uninfluenced by the reaction rate. However, bubble formation was seen to take place in one of the phases and since the bubbles consequently traversed the interface under the influence of buoyancy, the viscosity of the first phase was found to influence the final bubble size where increased viscosity would yield a larger bubble size.

  • 103.
    Kapilashrami, Era
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Wetting characteristics of oxygen-containing iron melts on refractory oxides2005In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 40, no 9-10, p. 2371-2375Article in journal (Refereed)
    Abstract [en]

    As part of refractory erosion studies, the wetting behaviour of molten iron containing varying amounts of oxygen on refractory oxides was investigated by the sessile drop method. The oxides investigated in the present work were alumina, silica and mullite. The reactions were followed in static as well as dynamic modes, under isothermal conditions, through contact angle measurements. Other parameters investigated in the present study were temperature and oxygen partial pressure. For all substrates, the contact angles started decreasing due to the lowering of the surface tension of iron, as oxygen at constant partial pressure, came into contact with the surface of the drop. At a critical level of oxygen in the metal drop, a reaction product started forming at the drop/substrate interface and at this stage the contact angle dropped suddenly. In all cases there was a tendency for the contact angle to increase after this minimum. In the alumina case, the iron drop moved away from the reaction site, once the product layer had been formed at the interface, probably due to the imbalance in the surface forces. In the case Of SiO2 and mullite, liquid slags were formed. The substrates were analysed through SEM and EDS. The reaction products identified were in agreement with thermodynamic predictions. In the case Of SiO2, deep erosions were formed along the periphery of the drops, probably due to Marangoni flow. The possible mechanisms of the reactions and their impact on refractory erosion are discussed in the light of the present experimental results.

  • 104. Kennedy, M. W.
    et al.
    Akhtar, S.
    Bakken, J. A.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science. Department of Materials Science and Engineering, Norwegian University of Science and Technology, Norway.
    Review of classical design methods as applied to aluminum billet heating with induction coils2011In: TMS Annual Meeting, 2011, p. 707-722Conference paper (Refereed)
    Abstract [en]

    In the present study classical induction design tools are applied to the problem of heating non-magnetic metal billets, using 50 Hz AC. As an example of great practical industrial interest, the induction heating of aluminum billets is addressed specifically. The predicted work piece power is compared with the measured work piece power for a long and a short coil, using well established methods, such as those of Burch and Davis, introduced in 1926/28, Dwight and Bagai in 1935, Baker in 1944/57, Vaughan and Williamson in 1945, and by Tudbury in 1960. A calculation methodology based on a combination of the available tools is also introduced and discussed. The method has proven to give an error of <10% of the actual work piece power. An equation for Tudbury's work piece shortness correction factor is disclosed for the first time.

  • 105.
    Kennedy, Mark W.
    et al.
    Norwegian University of Science and Technology, Trondheim, Norway .
    Akhtar, S.
    Bakken, J. A.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Analytical and FEM modeling of aluminum billet induction heating with experimental verification2012In: Light Metals 2012, John Wiley & Sons, 2012, p. 269-275Conference paper (Refereed)
    Abstract [en]

    Induction heating is commonly used in the re-heating of aluminum billets before forging or extrusion. Powerful finite element modeling (FEM) tools are available to assist in the design of such processes; however, such models should be validated by comparison with analytical solutions or experimental results to ensure accuracy. Induction heating experiments have been performed using a number of different coil designs and work piece dimensions at 50 Hz. Aluminum alloys with different electrical conductivities have been used, i.e. 6060 and A356. Process parameters such as: current, power, magnetic field, electrical conductivity, etc. have been measured with high precision instrumentation. Experimental data are presented and compared with equivalent 1D analytical and 2D axial symmetric FEM modeling results. The effect of frequency on the induction heating process is reviewed using the validated analytical and FEM models. Some recommendations are given with respect to appropriate modeling techniques, boundary conditions and numerical mesh sizes.

  • 106. Kennedy, Mark W.
    et al.
    Akhtar, S.
    Bakken, J. A.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Empirical Verification of a Short Coil Correction FactorManuscript (preprint) (Other academic)
    Abstract [en]

    The magnetic field produced in the air-gap by any particular 'short coil' at a fixed current, is affected by a highly complex interaction of the coil and work piece geometries and changes in frequency. A frequency modified semi-empirical short coil correction factor, based upon the formula published by Vaughan and Williamson in 1945, is presented and experimentally verified. This new equation is shown to predict the total system reactive power and the average magnetic flux at the surface of the work piece with typical differences of less than 2% at 50 Hz AC and to accurately predict work piece heating rates typically within 5% for aluminum billets at 50 Hz to 500 kHz AC. The work piece real and reactive powers, and total system reactive power are compared with both analytic and 2D axial symmetric FEM model solutions, as a function of operating frequencies from 50 Hz to 500 kHz. Measured flux density is compared to FEM and analytical predictions at 50 Hz.

  • 107. Kennedy, Mark W.
    et al.
    Akhtar, Shahid
    Bakken, Jon Arne
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Effect of Electromagnetic Lorentz Force on the Distribution of Inclusions Removed from Liquid Aluminum by a Ceramic Foam Filter in Continuous Filtration Tests2012Conference paper (Refereed)
  • 108. Kennedy, Mark W.
    et al.
    Akhtar, Shahid
    Bakken, Jon Arne
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Electromagnetically Enhanced Filtration of Aluminum Melts2011In: Light Metals 2011 / [ed] Stephen J. Lindsay, John Wiley & Sons, 2011, p. 763-768Chapter in book (Refereed)
  • 109.
    Kennedy, Mark W.
    et al.
    Norwegian University of Science and Technology, Trondheim, Norway .
    Akhtar, Shahid
    Bakken, Jon Arne
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Improved short coil correction factor for induction heating of billets2012In: 3rd International Symposium on High Temperature Metallurgical Processing, 2012, p. 373-382Conference paper (Refereed)
    Abstract [en]

    To determine the heating rate of billets using 'short coils', an appropriate correction factor must be applied to the theoretical relationship. In 1945, Vaughan and Williamson published a semi-empirically modified Nagaoka coefficient applicable for moderate frequency induction heating processes (10 kHz). Recently it was demonstrated that the method of Vaughan and Williamson gives <10% error in the estimated power when heating aluminum billets at 50 Hz. In the present study, experiments have been conducted on aluminum billets in order to verify an empirical frequency corrected 'short coil' equation. Measurements of electrical conductivity (<± 0.5%), current (± 1%), heat (± 1-3%), and magnetic flux density (± 1-2%) have been performed. The results are compared with 1D analytical calculations, and 2D axial symmetric FEM modeling using COMSOL 4.2®. The frequency corrected equation has proven to provide accurate predictions of power (<4% error) within the frequency range 50 Hz to 500 kHz.

  • 110. Kennedy, Mark W.
    et al.
    Fritzsch, Robert
    Akhtar, Shahid
    Bakken, Jon Arne
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Effect of Electromagnetic Force on the Distribution of Inclusions Removed from Liquid Aluminium by a Ceramic Foam Filter2011Conference paper (Refereed)
  • 111.
    Kennedy, Mark William
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Magnetic Fields and Induced Power in the Induction Heating of Aluminium Billets2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Induction heating is a common industrial process used for the reheating of billets before extrusion or forging. In this work the influence of the coil and work piece geometry, the effect of the electrical properties of the work piece, and the coil current and frequency, on the magnetic flux density and resulting work piece heating rates were studied. A combination of 1D analytical solutions, 2D axial symmetric finite element modelling and precise measurements has been used.

    Dozens of heating and magnetic field experiments have been conducted, with steadily increasing sophistication and measurement accuracy. The development of the experimental techniques will be described in the ‘cover’ and related to the later results published in the supplements. Experimental results are compared to predictions obtained from analytical and numerical models. The published measurements obtained for the billet heating experiments consisted of: billet electrical conductivity with <0.5% error, applied currents with <1% error, magnetic flux densities with 1-2% error, calorifically determined heating rates with <2% error and electrical reactive power with <~2% error. 2 D axial symmetric finite element models were obtained, which describe the measured results with less than a 2% difference (i.e. an ‘error’ of the same magnitude as the measurement uncertainty). Heating and reactive power results predicted by the FEM model are in excellent agreement with analytical solutions from 50 Hz to 500 kHz (differences from <1% to 6%).

    A modified 1D short coil correction factor is presented which accounts for the interaction of the coil and work piece geometry, electrical properties and operating frequency, on the average magnetic flux density of the coil/work piece air-gap and the resulting heating rate. Using this factor, the average magnetic flux density in the air-gap can be estimated analytically within 2-3% and the heating rates of billets of known electrical properties can be estimated, with typical errors on the order of 5%.

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  • 112.
    Kennedy, Mark William
    et al.
    Department of Material Science and Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway.
    Akhtar, Shahid
    Bakken, Jon Arne
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science. Department of Material Science and Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway.
    Electromagnetically Modified Filtration of Aluminum Melts-Part I: Electromagnetic Theory and 30 PPI Ceramic Foam Filter Experimental Results2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 3, p. 691-705Article in journal (Refereed)
    Abstract [en]

    In the present work, laboratory-scale continuous filtration tests of liquid A356 aluminum alloy have been performed. The tests were conducted using standard 30 PPI (pores per inch) ceramic foam filters combined with magnetic flux densities (similar to 0.1 and 0.2 T), produced using two different induction coils operated at 50 Hz AC. A reference filtration test was also carried out under gravity conditions, i.e., without an applied magnetic field. The obtained results clearly prove that the magnetic field has a significant affect on the distribution of SiC particles. The influence of the electromagnetic Lorentz forces and induced bulk metal flow on the obtained filtration efficiencies and on the wetting behavior of the filter media by liquid aluminum is discussed. The magnitudes of the Lorentz forces produced by the induction coils are quantified based on analytical and COMSOL 4.2(A (R)) finite element modeling.

  • 113. Kennedy, Mark William
    et al.
    Akhtar, Shahid
    Bakken, Jon Arne
    Aune, Ragnhild Elizabeth
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Reply to Discussion of "Characterization of Ceramic Foam Filters Used for Liquid Metal Filtration" and "Electromagnetically Modified Filtration of Aluminum Melts: Part I. Electromagnetic Theory and 30 PPI Ceramic Foam Filter Experimental Results"2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 5, p. 1056-1057Article in journal (Refereed)
  • 114. Kennedy, Mark William
    et al.
    Zhang, Kexu
    Fritzsch, Robert
    Akhtar, Shahid
    Bakken, Jon Arne
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Characterization of Ceramic Foam Filters Used for Liquid Metal Filtration2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 3, p. 671-690Article in journal (Refereed)
    Abstract [en]

    In the current study, the morphology including tortuosity, and the permeability of 50-mm thick commercially available 30, 40, 50, and 80 pores per inch (PPI) alumina ceramic foam filters (CFFs) have been investigated. Measurements have been taken of cell (pore), window, and strut sizes, porosity, tortuosity, and liquid permeability. Water velocities from similar to 0.015 to 0.77 m/s have been used to derive both first-order (Darcy) and second-order (Non-Darcy) terms for being used with the Forchheimer equation. Measurements were made using 49-mm "straight through" and 101-mm diameter "expanding flow field" designs. Results from the two designs are compared with calculations made using COMSOL 4.2a(A (R)) 2D axial symmetric finite element modeling (FEM), as a function of velocity and filter PPI. Permeability results are correlated using directly measurable parameters and compared with the previously published results. Development of improved wall sealing (49 mm) and elimination of wall effects (101 mm) have led to a high level of agreement between experimental, analytic, and FEM methods (+/- 0 to 7 pct on predicted pressure drop) for both types of experiments. Tortuosity has been determined by two inductive methods, one using cold-solidified samples at 60 kHz and the other using liquid metal at 50 Hz, giving comparable results.

  • 115. Khalaghi, B.
    et al.
    Kvalheim, E.
    Tokushige, M.
    Haarberg, G. M.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Electrochemical behaviour of dissolved iron chloride in KCl+LiCl+NaCl melt at 550°C2014In: ECS Transactions, ISSN 1938-5862, E-ISSN 1938-6737, Vol. 64, no 4, p. 301-310Article in journal (Refereed)
    Abstract [en]

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

  • 116. Khanna, R.
    et al.
    Haq, M. Ikram-Ul
    Wang, Y.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Sahajwalla, V.
    Chemical Interactions of Alumina-Carbon Refractories with Molten Steel at 1823 K (1550 degrees C): Implications for Refractory Degradation and Steel Quality2011In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 42, no 4, p. 677-684Article in journal (Refereed)
    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.

  • 117. Khanna, Rita
    et al.
    Ikram-Ul-Haq, Muhammad
    Sadi, Seyed Fahandej
    Sahajwalla, Veena
    Mukherjee, Partho Sarathy
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Reduction Reactions in Al2O3-C-Fe and Al2O3-Fe2O3-C Systems at 1 823 K2014In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 54, no 7, p. 1485-1490Article in journal (Refereed)
    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.

  • 118.
    Khodabandeh, Erfan
    et al.
    Amirkabir Univ Technol, Tehran Polytech, Mech Engn Dept, 424 Hafez Ave,POB 15875-4413, Tehran, Iran..
    Akbari, Omid Ali
    Islamic Azad Univ, Young Researchers & Elite Club, Khomeinishahr Branch, Khomeinishahr, Iran..
    Toghraie, Davood
    Islamic Azad Univ, Dept Mech Engn, Khomeinishahr Branch, Khomeinishahr 84175119, Iran..
    Saffari Pour, Mohsen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science. Sharif Univ Technol, Dept Mech Engn, Tehran, Iran..
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Numerical investigation of thermal performance augmentation of nanofluid flow in microchannel heat sinks by using of novel nozzle structure: sinusoidal cavities and rectangular ribs2019In: Journal of the Brazilian Society of Mechanical Sciences and Engineering, ISSN 1678-5878, E-ISSN 1806-3691, Vol. 41, no 10, article id UNSP 443Article in journal (Refereed)
    Abstract [en]

    In this paper, we present a numerical simulation of a laminar, steady and Newtonian flow of f-graphene nanoplatelet/water nanofluid in a new microchannel design with factors for increasing heat transfer such as presence of ribs, curves to enable satisfactory fluid mixing and changing fluid course at the inlet and exit sections. The results of this study show that Nusselt number is dependent on nanoparticles concentration, inlet geometry and Reynolds number. As the nanofluid concentration increases from 0 to 0.1% and Reynolds number from 50 to 1000, the Nusselt number enhances nearly up to 3% for increase in fluid concentration and averagely from 15.45 to 54.1 and from 14.5 to 55.9 for geometry with and without rectangular rib, respectively. The presence of ribs in the middle section of microchannel and curves close to hot walls causes a complete mixing of the fluid in different zones. When the nanoparticles concentration is increased, the pressure drop and velocity gradient will become higher. An increased concentration of nanoparticles in contribution with higher Reynolds numbers only increases the fraction factor slightly. (The fraction factor increases nearly 37% and 35% for Re = 50 and 1000, respectively.) The highest uniform temperature distribution can be found in the first zones of fluid in the microchannel and by further movement of fluid toward exit section, because of decreasing difference between surface and fluid temperature, the growth of temperature boundary layer increases and results in non-uniformity in temperature distribution in microchannel and cooling fluid. With decrease in the concentration from 0 to 0.1%, the average outlet temperature and FOM decrease nearby 0.62% and 6.15, respectively.

  • 119.
    Korojy, Bahman
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Ekbom, Lars
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Microsegregation and Solidification Shrinkage of Copper-Lead Base Alloys2009In: Advances in Materials Science and Engineering, ISSN 1687-6822Article in journal (Refereed)
    Abstract [en]

    Microsegregation and solidification shrinkage were studied on copper-lead base alloys. A series of solidification experiments was performed, using differential thermal analysis (DTA) to evaluate the solidification process. The chemical compositions of the different phases were measured via energy dispersive X-ray spectroscopy (EDS) for the Cu-Sn-Pb and the Cu-Sn-Zn-Pb systems. The results were compared with the calculated data according to Scheil's equation. The volume change during solidification was measured for the Cu-Pb and the Cu-Sn-Pb systems using a dilatometer that was developed to investigate the melting and solidification processes. A shrinkage model was used to explain the volume change during solidification. The theoretical model agreed reasonably well with the experimental results. The deviation appears to depend on the formation of lattice defects during the solidification process and consequently on the condensation of those defects at the end of the solidification process. The formation of lattice defects was supported by quenching experiments, giving a larger fraction of solid than expected from the equilibrium calculation.

  • 120.
    Korojy, Bahman
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Nassar, Hani
    Fredriksson, H
    Hot crack formation during peritectic reaction in steels2010In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 37, no 1, p. 63-72Article in journal (Refereed)
    Abstract [en]

    Hot crack formation during solidification was investigated during the peritectic reaction in steels. A series of in situ solidification experiments was performed using a MTS tensile testing machine combined with a mirror furnace. Sample temperature and force change were measured during the solidification process. The force measurements showed a sudden drop during the solidification of samples, which occurred around the peritectic temperature of the alloy, were accompanied by cracks or refilled cracks in the microstructure. Furthermore, the peritectic reaction types were studied theoretically and experimentally to understand their effects on the force change during solidification. The theoretical analyses showed that the volume change due to the peritectic transformation is one of the reasons for crack formation. In addition, when the peritectic reaction occurs in a diffusionless (partition less) manner in an alloy with sufficiently high primary precipitation, crack formation is more probable.

  • 121. Li, Jinfu
    et al.
    Sun, Yongqi
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Zhang, Zuotai
    Oxidation kinetics of magnesium aluminum oxynitride-boron nitride (MgAlON-BN) composites2014In: Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan, ISSN 1882-0743, Vol. 122, no 1429, p. 829-834Article in journal (Refereed)
    Abstract [en]

    The oxidation behaviour of MgAlON-BN composite was investigated under the air atmosphere using thermogravimetry (TG), scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques in the present articles. Non-isothermal experimental results indicated that the rate of oxidation can be neglected at low temperature and, with further increasing temperatures, an increase of the oxidation was observed. While BN addition promoted the oxidation above 1100 K, and the weight gain was observed to decrease due to the fast evaporation of boron oxide as the temperature was beyond 1580 K. Isothermal studies also clearly indicated the decrease of weight gain due to evaporation after a certain oxidation time. The oxidation mechanism was investigated, and the results showed the oxidation products were gamma-Al2O3 at low temperature and transformed to alpha-Al2O3 as the temperature was above 1100 degrees C. BN addition promoted the transformation from gamma-Al2O3 to alpha-Al2O3. From the isothermal oxidations, the kinetics of oxidation and evaporation were evaluated, and the overall kinetics of oxidation and evaporation were studied, and the activation energy for evaporation of B2O3 and for the oxidation of MgAlON-15 vol% BN at the later stage are 115.4 and 196.1 kJ/mol, respectively. The present paper provides a way to deal with oxidation of composites containing evaporating component.

  • 122.
    Li, Peng
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Innovative process solutions towards recycling of salt cake from secondary aluminum smelting2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    To offer better solutions for the recycling of salt cake from secondary aluminum melting, several innovative investigations were carried out based on hydrometallurgical and pyrometallurgical views.

    Thermal diffusivity measurements as a function of temperature on salts-Al composites having various compositions (0, 2, 4, 6, 8, 10, 12wt pct metallic Al) were carried out. Its attempt to derive theoretical relationships between aluminium contents in the salt-Al composites and the thermal conductivities so that these would serve as calibration curves for industrial samples taken out from secondary aluminium re-melting at a later stage.

    The AlN hydrolysis behavior in NaCl solution was investigated by immersing pure AlN powder in deionized water, 0.3mol/l NaCl aq, 0.6mol/l NaCl aq and NaCl solution respectively with CO2 bubbling at 291K. The results showed that AlN powder underwent enhanced hydrolysis in NaCl aq than that in deionized water, while, the introduction of CO2 was found to hinder the hydrolysis even in the presence of NaCl. The characterization of the products after hydrolysis was carried out using XRD, SEM and TEM analyses. It was shown that the hydrolysis process included a slow-reaction period involving the dissolution of aluminum hydroxide layer around raw AlN particle, followed by the precipitation of aluminum hydroxide gel and the crystallization of boehmite, bayerite and gibbsite. The effects of sodium chloride concentration on the hydrolysis behavior are presented.

    The leaching process in CO2-saturated water showed that, at a solid to liquid ratio of 1:20 and 3h at 291K, the extraction of Na and K from the dross could be kept as high as 95.6% and 95.9%, respectively. At the same time, with continuous CO2 bubbling, the mass of generated NH3 during the leaching process decreased significantly, also the escaping NH3 gas decreased from 0.25mg in pure water down to <0.006mg. The above results showed that the introduction of CO2 causes hindrance to the hydrolysis of AlN, meanwhile, effective absorption of ammonia. The plausible mechanisms for the observed phenomena are discussed. The concept of the leaching of the salt cake by carbonated water and the consequent retention of AlN in the leach residue opens up a promising route towards an environment-friendly recycling process for the salt cake viz. recovery of the salts, utilization of CO2 and further processing of the dross residue, towards the synthesis of SiAlON from the leach residues.  

    In alternative route to the processing of salt cake, the ammonia gas evolved by hydrolysis of AlN was collected by CO2-saturated water during water leaching at 373K. The products, i.e. ammonium carbonates which are free of chlorides, has application as a fertilizer, besides that, this method also has the advantage of fixing carbon from CO2, which is the subject of many investigations around the world.

    The oxidation behavior of composites SiMgAlON phases (β-SiAlON, MgAlON and 15R) synthesized from the residue during the leaching treatment of salt cake and corresponding synthetic samples was investigated in air by thermogravimetric measurements. The oxidation studies reveal the effects of impurities, namely, Fe2O3 and CaO present in the salt cake residue. From the view of kinetics, the addition of Fe2O3 brings a lower activation energy and more aggressive oxidation. The additive of CaO caused the shrinkage during the synthesis and liquid formation during the oxidation above 1673K, thus retard the oxidation rate. The impurities of CaO and Fe2O3 in the leaching residue can result in an aggressive oxidation at low temperature and a protective oxidation at temperatures above the eutectic point. From the view of phase evolution, with the progress of oxidation, the composition of the material being oxidized moved towards the Al2O3-rich corner of MgO-Al2O3-SiO2 or CaO-MgO-Al2O3-SiO2 phase diagrams relevant to SiMgAlON composite. At lower temperatures, the addition of Fe2O3 and CaO facilitated the formation of cordierite and anorthite, respectively. With the increasing of temperature, islands of silicate melt were formed dissolving these oxides, with the liquidus temperature getting lowered as a consequence. The liquid phase formed engulfed the adjacent solid phases providing strong mobility for the cations and enabling the crystal growth. As a result, intermediate products, i.e. cordierite, anorthite, spinel, which formed earlier during oxidation are found to get dissolved in the liquid phase.

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    thesis
  • 123.
    Li, Peng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Guo, M.
    Zhang, M.
    Wang, X. D.
    Seetharaman, Seetharaman
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Spinel synthesis from aluminium dross2011In: Transactions of the Institutions of Mining and Metallurgy, Section C: Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, Vol. 120, no 4, p. 247-250Article in journal (Refereed)
    Abstract [en]

    It is believed that aluminium recycling is going to become the main route of aluminium production in future. The secondary aluminium dross produced during aluminium remelting contains large amounts of salts and oxides. In recent years, various techniques were developed to recycle the dross in order to obtain the valuable materials in it. In this paper, spinel has been successfully synthesised from aluminium dross. After leaching for 1 h (the ratio of solid/liquid was 1 : 50 at 20uC) with water, the salts KCl and NaCl were almost removed off from the dross. The temperature effect on the spinel synthesis was investigated in detail using the traditional solid phase sintering method. It was found that with increasing temperature, the spinel and Al2O 3 became the main phases in the final products.

  • 124.
    Li, Peng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Guo, Min
    Zhang, M.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Leaching process investigation of secondary aluminium dross: Investigation of AlN hydrolysis behaviour in NaCl solution2012In: Transactions of the Institutions of Mining and Metallurgy, Section C: Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, Vol. 121, p. 140-146Article in journal (Refereed)
    Abstract [en]

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

  • 125.
    Li, Peng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Guo, Min
    Zhang, M.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Leaching Process Investigation of Secondary Aluminum Dross: The Effect of CO 2 on Leaching Process of Salt Cake from Aluminum Remelting Process2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 5, p. 1220-1230Article in journal (Refereed)
    Abstract [en]

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

  • 126.
    Li, Peng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Guo, Min
    Zhang, Mei
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Oxidation Kinetics of AlN Under CO2 Atmosphere2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 2, p. 406-412Article in journal (Refereed)
    Abstract [en]

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

  • 127.
    Li, Peng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Wang, Lijun
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Thermal conductivity of Al-Salt composites2012Report (Refereed)
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    fulltext
  • 128.
    Li, Peng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Zhang, Mei
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part I: Kinetics2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 1, p. 210-219Article in journal (Refereed)
    Abstract [en]

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

  • 129.
    Li, Peng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Zhang, Mei
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part II: Phase Evolution2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 1, p. 220-232Article in journal (Refereed)
    Abstract [en]

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

  • 130.
    Li, Peng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Zhang, Mei
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Recycling of Aluminum Salt Cake: Utilization of Evolved Ammonia2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 1, p. 16-19Article in journal (Refereed)
    Abstract [en]

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

  • 131. Mahjoub, R.
    et al.
    Cao, Weimin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Khanna, R.
    Sahajwalla, V.
    An atomistic Monte Carlo investigation on the Solid-Liquid phasetransition in BCC iron: The role of boundary conditionsIn: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801Article in journal (Other academic)
  • 132.
    Makaya, Advenit
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    On the effect of nitrogen, hydrogen and cooling rate on the solidification and pore formation in Fe-base and Al-base alloys2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Experiments on the production of porous metallic materials were performed on Fe-base and Al-base alloys. The method involves dissolution of gases in the liquid state and solidification at various cooling rates. The alloy compositions were selected to induce solidification of primary particles intended to control the pore distribution. For the Fe-base alloys, nitrogen was introduced into the melt by dissolution of chromium nitride powder. Fe-Cr-Mn-Si-C alloys featuring M7C3 carbide particles were selected. For the Al-base alloys, hydrogen gas was dissolved into the melt by decomposition of water vapor. Al-Ti and Al-Fe alloys featuring primary Al3Ti and Al3Fe intermetallic particles, respectively, were considered. In the Fe-base alloys, a homogeneous distribution of gas pores through the specimens’ volume was obtained at high cooling rate (water quenching) and after introduction of external nucleating agents. In the case of the Al-base alloys, a good pore distribution was observed at all cooling rates and without addition of nucleating agents. Calculations of the variation of nitrogen (respectively hydrogen) solubility based on Wagner interaction parameters suggest that pore nucleation and growth occur during precipitation of the primary particles (M7C3 carbides, Al3Ti or Al3Fe intermetallics), due to composition changes in the melt and resultant supersaturation with gas atoms. Microscopic analyses revealed that the primary particles control the pore growth in the melt and act as barriers between adjacent pores, thereby preventing pore coalescence and promoting a fine pore distribution. Uniaxial compression testing of the porous Al-Ti and Al-Fe materials showed the typical compressive behavior of cellular metals. Further work is needed to improve the quality and reproducibility of the porous structures which can possibly be used in energy absorption or load-bearing applications.

    As a corollary result of the quenching of hypereutectic Fe-Cr-Mn-Si-C alloys in the experiments of synthesis of porous metals, a homogeneous featureless structure was observed in some parts of the samples, instead of the equilibrium structure of M7C3 and eutectic phases. Subsequent investigations on rapid solidification of Fe-base alloys at various alloy compositions and cooling rates led to the formation of a single-phase structure for the composition Fe-8Cr-6Mn-5Mo-5Si-3.2C (wt.%), at relatively low cooling rates (≈103 K/s) and for large sample dimensions (2.85 mm). The single phase, which is likely to be the hcp ɛ-phase, was found to decompose into a finely distributed structure of bainite and carbides at ≈600 °C. The annealed structure showed very high hardness values (850 to 1200 HV), which could be exploited in the development of high-strength Fe-base materials.

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  • 133.
    Matsushita, Taishi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Chapman, L.
    Brooks, R.
    Egry, I.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Thermal diffusivity of TiAlNb and AlNi alloys - The European IMPRESS project2008In: Diffusion and defect data, solid state data. Part A, Defect and diffusion forum, ISSN 1012-0386, E-ISSN 1662-9507, Vol. 273-276, p. 375-380Article in journal (Refereed)
    Abstract [en]

    The thermal diffusivities of some industrially important alloys have been measured as a part of the EU funded Intermetallic Materials Processing in Relation to Earth and Space Solidification (IMPRESS) project which is coordinated by the European Space Agency (ESA). The thermal diffusivities of the alloys were measured by the Laser flash method with a carefully designed gas cleaning system to remove traces of oxygen from the argon atmosphere. In the present work, the thermal diffusivity of TiAlNb (Ti46.1Al45.9Nb8 at %) and AlNi alloy (Al-Ni31.5 at %) alloys have been measured independently at Royal Institute of Technology, Sweden (KTH) and National Physical Laboratory, UK (NPL). The results from both laboratories were consistent, and have been compared with predictions of phase transformation temperatures calculated using Thermo Calc and MTDATA software. Generally the variation of thermal diffusivity appears to be related to the phase transformation. However, one anomaly observed in the present work on TiAlNb was a maximum thermal diffusivity value at about HOOK. No corresponding peak was found for the density, ρ, the specific heat capacity, Cp, or the electrical resistivity, 1/σ, which were also measured as part of the project. In view of the fact that the thermal diffusivity could be related to electrical conductivity by the Wiedemann-Franz law describing electronic contribution to heat conduction, the present results indicate a non-electron contribution. This aspect is being currently investigated further. The recommended thermal diffusivity value of TiAlNb and AlNi alloys were obtained as follows. TiAlNb alloy: a = 3.75+ 5.16 ·10-3T+1.89·10-6 T2-2. 69·10-9 T3 [10-6 m2 s -1] (293 K &lt; T &lt; 1573 K) AlNi alloy: a = 4.77+ 5.41·10-2T- 7.14·10-5T2 + 2.88·10-8T3 [10-6 m2/s] (373K &lt;T&lt;943K).

  • 134.
    Matsushita, Taishi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Chapman, Lindsay
    Brooks, Rob
    Egry, Ivan
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Thermal diffusivity of TiAlNb and AN alloys - the European IMPRESS project2008In: Diffusion In Solids And Liquids III / [ed] Ochsner, A; Murch, GE, 2008, Vol. 273-276, p. 375-380Conference paper (Refereed)
    Abstract [en]

    The thermal diffusivities of some industrially important alloys have been measured as a part of the EU funded Intermetallic Materials Processing in Relation to Earth and Space Solidification (IMPRESS) project which is coordinated by the European Space Agency (ESA). The thermal diffusivities of the alloys were measured by the Laser flash method with a carefully designed gas cleaning system to remove traces of oxygen from the argon atmosphere. In the present work, the thermal diffusivity of TiAlNb (Ti46.1A145.9Nb8 at %) and AlNi alloy (Al-Ni31.5 at %) alloys have been measured independently at Royal Institute of Technology, Sweden (KTH) and National Physical Laboratory, UK (NPL). The results from both laboratories were consistent, and have been compared with predictions of phase transformation temperatures calculated using Thermo Calc and MTDATA software. Generally the variation of thermal diffusivity appears to be related to the phase transformation. However, one anomaly observed in the present work on TiAlNb was a maximum thermal diffusivity value at about HOOK. No corresponding peak was found for the density, p, the specific heat capacity, C, or the electrical resistivity, 1/sigma, which were also measured as part of the project. In view of the fact that the thermal diffusivity could be related to electrical conductivity by the Wiedemann-Franz law describing electronic contribution to heat conduction, the present results indicate a non-electron contribution. This aspect is being currently investigated further. The recommended thermal diffusivity value of TiAlNb and AIM alloys were obtained as follows. TiAlNb alloy: alpha = 3.75+ 5.16.10(-3)T+1.89.10(-6) T-2-2.69.10(-9) T-3 [10(-6) m(2) s(-1)] (293 K < T < 1573 K) AlNi alloy: alpha = 4.77+ 5.41.10(-2)T - 7.14.10(-5)T(2)+ 2.88.10(-8)T(3) [10(-6) m(2)/s] (373K < T < 943K).

  • 135.
    Matsushita, Taishi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Fecht, H. J.
    Wunderlich, R. K.
    Egry, I.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Studies of the Thermophysical Properties of Commercial CMSX-4 Alloy2009In: Journal of Chemical and Engineering Data, ISSN 0021-9568, E-ISSN 1520-5134, Vol. 54, no 9, p. 2584-2592Article in journal (Refereed)
    Abstract [en]

    In this paper, measurements of the heat capacities and thermal diffusivities of commercial CMSX-4 nickel-based superalloy are described, and the results are presented. Since the as-received commercial alloy sample is not at the thermodynamic equilibrium state, the phases present in the alloy undergo transformations toward equilibrium state as the measurements are made at temperatures above which the rate of transformation can be significant. The microstructures of the as-received sample as well as heat treated samples were observed, and the relation with the properties was discussed. The results are discussed considering the phase changes Occurring with the thermodynamic equilibrium state as the reference. The results are of great relevance in the performance of these alloys in industrial applications.

  • 136.
    Matsushita, Taishi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Hayashi, M.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Thermochemical and thermophysical property measurements in slag systems2005In: International journal of materials & product technology, ISSN 0268-1900, E-ISSN 1741-5209, Vol. 22, no 4, p. 351-390Article, review/survey (Refereed)
    Abstract [en]

    This paper reviews developments on experimental methods and results of thermochemical and thermophysical property measurements of molten silicate slag systems and its theoretical achievements. Several selected topics are focused on, including experimental procedure and measurements of viscosity, density, surface-interfacial tension, thermal conductivity, thermal diffusivity and velocity and absorption coefficient of ultrasonic waves. Thermal conductivity and diffusivity of slags have been mainly measured by the transient techniques such as the laser flash and hot wire methods. Most of the measurements for velocity and absorption coefficient of ultrasonic waves are carried out using a pulse technique. The reliable data for thermochemical and thermophysical properties are required for the optimisation of metallurgical processes and the data is needed in order to improve the numerical models of processing. For academic interest, the results were discussed from the viewpoint of slag structure, as these properties are closely related to the slag structure.

  • 137.
    Matsushita, Taishi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Ishikawa, T.
    Paradis, P. F.
    Mukai, K.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Density measurements of mould flux slags by electrostatic levitation method2006In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 46, no 4, p. 606-610Article in journal (Refereed)
    Abstract [en]

    In the present work, the densities of a mould flux slag were measured as a function of temperature by electrostatic levitation (ESL) method. The density of a mould flux, as measured by ESL method decreased linearly with increasing temperature. The results obtained are compared with the value measured by the sessile drop method just above the melting point of the slag. The discrepancies are explained on the basis of the inherent merits and demerits of the two types of measurements. The experimental values of present work were also compared with the density data for other mould flux slags from Swedish plant practice, obtained by the sessile drop method as part of the present work as well as literature data. A thermodynamic model of molar volume, developed in the present group was used to predict the density of slags. The molar volume was described as a function of integral molar enthalpies of mixing. In the case of ternary systems corresponding to the mould flux slag, the calculated values are in reasonable agreement with the experimental values.

  • 138.
    Matsushita, Taishi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Sasaki, Yasushi
    Gornerup, Marten
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Stress relaxation behavior of molten slags2006In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 46, no 8, p. 1258-1263Article in journal (Refereed)
    Abstract [en]

    In the present work, a method to measure stress relaxation of molten slags, developed earlier by one of the authors, was applied to mould flux slags as well as synthetic slags. The molten slag was sandwiched by two Pt plates and was compressed. And stress relaxation tests (the structural relaxation of molten slags) have been conducted by compressing the molten slags as well as mould flux slags at strain rates of 10 mm/min. The results of stress relaxation tests were discussed from the viewpoint of relaxation time and structure of slags with the aid of Raman spectroscopy. The stress relaxation behavior is found to be linked to the structure of slags. The residual stress after a compression was increased with increasing of Al2O3 content and with decreasing of CaF2 content. The relaxation behavior was changed drastically with increasing of temperature for some molten slags.

  • 139.
    Matsushita, Taishi
    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.
    ThermoLab project: Results on Thermophysical Properties Data of Iron Alloys2008In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 27, no 6, p. 413-421Article in journal (Refereed)
    Abstract [en]

    As a part of ThermoLab project, the thermophysical properties of industrially important iron alloys were measured. In this paper, the measurement results of the differential scanning calorimetry (DSC), specific heat capacity, thermal diffusivity, surface tension and viscosity of one Fe-Cr and of a low oxygen eutectoid manganese steel are reported. In addition to the ground based experiments, parabolic flights (microgravity) experiments with a non-contact electromagnetic levitation device were employed for surface tension and viscosity measurements.

  • 140.
    Matsushita, Taishi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Umezawa, Y.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Rupture Strength of some Mould Flux Slag Films relevant to Swedish Continuous Casting Practice2008Article in journal (Refereed)
    Abstract [en]

    In this paper, the high temperature rupture strengths of some solid mould flux slag films in Swedish continuous casting processes are presented. The apparatus, designed and constructed in the present laboratory is based on the principle that the solidified film of the mould flux slag is subjected to elongation stress at temperatures below the solidus points of the fluxes. The rupture strength tests were conducted in air. The results indicate that the rupture strength is dependent on the extent of polymerization of the silicate network. The results of Raman spectra studies of the mould flux slags used in the present work were corroborated by estimations of the NBO/T ratios of the slags. It was found that lower NBO/T ratios in the slag led to higher rupture strengths. Earlier measurements of the viscosities, thermal diffusivities as well as stress relaxation results for the same slags followed a similar trend indicating the dependency of these properties on the slag structure and a clear link between thermophysical and mechanical properties of slags. The results are expected to provide some basic guidelines to develop the next-generation mould flux and modelling of the continuous casting process.

  • 141.
    Matsushita, Taishi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Watanabe, T.
    Dynamic in situ X-ray observation of a molten steel drop shape change in molten slag2011In: Transactions of the Institutions of Mining and Metallurgy, Section C: Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, Vol. 120, no 1, p. 49-55Article in journal (Refereed)
    Abstract [en]

    In the present work, the interfacial reactions between molten synthetic slag (Al2O3-CaO-SiO2- FeO) and liquid iron alloy were investigated at 1873 K with the aid of an X-ray radiographic apparatus. The mother slag consists of 40 mass%CaO, 40 mass%SiO2 and 20 mass%Al2O3.FeO was added to this slag at the experimental temperature, and the movement of the droplet and deformation of the droplet shape were monitored in the dynamic mode. The change of the shape of the droplet is discussed based on the reaction and mass transfer at the slag/metal interface. From the movement of the droplet, interfacial velocity of the metal droplet induced by Marangoni flow was estimated and compared with the results obtained in the present laboratory earlier. The importance of surface velocity values on steel refining process simulations is discussed.

  • 142.
    Matsushita, Taishi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Watanabe, T.
    Hayashi, M.
    Mukai, K.
    Thermal, optical and surface/interfacial properties of molten slag systems2011In: International Materials Reviews, ISSN 0950-6608, E-ISSN 1743-2804, Vol. 56, no 5-6, p. 287-323Article, review/survey (Refereed)
    Abstract [en]

    In modelling mass and heat transfer steps in metallurgical processes, it is important to have knowledge of the physical properties of slags, the most important among these being the surface and interfacial tensions, thermal diffusivities, optical properties and viscosities. A critical review is presented of work reported in the past two decades relating to the following properties of slag systems: (i) surface/interfacial tensions and related interfacial phenomena; (ii) thermal diffusivities and thermal conductivities; (iii) velocities and coefficients of absorption of ultrasonic waves; (iv) optical properties. A perspective for further work is also provided.

  • 143. Mis, M.
    et al.
    Sardana, N.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    The Synthesis and Characterization of Ni-W-C Alloy Powders by H-2-CH4 Reaction with Oxides2008In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 27, no 4, p. 209-222Article in journal (Refereed)
    Abstract [en]

    With a view to developing a more energy-efficient and environment-friendly process route for the production of W-C based cutting tools, a single step process for the synthesis of tungsten carbides containing Ni from oxide precursors was investigated in the present work. A fluidized bed reactor was employed, wherein the mixed oxides were subjected to simultaneous reduction and carburization using H-2-CH4-Ar gas mixtures in the temperature range 1073-1273 K. The carbon potential in the gas phase could be accurately controlled by suitably adjusting the H-2/CH4 ratio. The impact of gas flow rates and temperature on the reaction product was examined. The carbide product obtained was characterized by SEM and X-ray diffraction. The results showed that the product consisted of Ni-W-C alloys, which were in consistency with the phase diagram at the temperature of reaction. The particle size of the carbides is in the range of 10(-8)m, which was dependent on the process temperature, higher temperature yielding larger grains. The results indicate that the gas-solid reaction route combining reduction and carburization is an efficient method that can be commercially applied for the production of a variety of cemented carbides.

  • 144. Mittal, Ayush
    et al.
    Jelkina Albertsson, Galina
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Gupta, Govind Sharan
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Subramanian, Sankaran
    Some Thermodynamic Aspects of the Oxides of Chromium2014In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 45, no 2, p. 338-344Article in journal (Refereed)
    Abstract [en]

    To understand Cr emissions from slag melts to a vapor phase, an assessment of the stabilities of the chromium oxides at high temperatures has been carried out. The objective of the present study is to present a set of consistent data corresponding to the thermodynamic properties of the oxides of chromium, with special reference to the emission of hexavalent chromium from slags. In the current work, critical analysis of the experimental data available and a third analysis in the case of Cr2O3 have been carried out. Commercial databases, Fact Sage and ThermoCalc along with NIST-JANAF Thermochemical Tables, have been used for the analysis and comparisons of the results that are presented. The significant discrepancies in the available data have been pointed out. The data from NIST-JANAF Thermochemical Tables have been found to provide a set of consistent data for the various chromium oxides. An Ellingham diagram and the equations for the Delta G degrees (standard Gibbs free energy change) of formation of CrOx have been proposed. The present analysis shows that CrO3(g) is likely to be emitted from slag melts at high oxygen partial pressures.

  • 145. Momcilovic, D.
    et al.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Material Property Changes vs. Release of Phthalates from In-vitro and In-vivo Aged Biomaterials Made of PVC2008Conference paper (Refereed)
  • 146. Morales, R.
    et al.
    Arvanitidis, I.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Gas-solid reactions towards new frontiers2006In: 2006 TMS Fall Extraction and Processing Division: Sohn International Symposium, 2006, p. 97-114Conference paper (Refereed)
    Abstract [en]

    Reactions between solids and a gas phase have many interesting theoretical aspects as well as technological applications. The present group had carried out experimental investigations as well as theoretical studies of a number of gas-solid reactions over the past decade and was able to derive interesting results. Studies of the decomposition of alkaline earth carbonates were carried out by thermogravimetric analyses. The experiments were carried out using thin powder beds as well as iso-statically pressed compacts with thermocouples embedded in the same. The investigations revealed the complexity of the reactions and the impact of the heat- and mass transfer aspects on the reaction kinetics. In the case of BaCO3, the kinetics of decomposition was complicated by the formation of a liquid phase. In the case of SrCO3, the reaction kinetics could be simulated by theoretical modeling. Gas-solid reactions were also employed as a versatile process tool towards the production of alloys and intermetallics involving transition elements by hydrogen reduction of complex oxides involving transition metals. Thin powder beds were employed to examine the micro-kinetics, while fluidized bed technique was utilized to produce bulk alloys. Preliminary correlations could be drawn between the thermodynamic stabilities of the oxides and the activation energies of chemical reduction steps. Adjusting the process parameters, products at nano-scale could be produced. The structural, mechanical and thermal properties were investigated in the case of these products. The potentialities of this method as a green route to produce industrially important alloys and intermetallics with unique properties are demonstrated.

  • 147. Morales, R.
    et al.
    Tavera, F. J.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Hydrogen reduction of complex oxides - a novel route toward the production of nanograined alloys and intermetallics2005In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 34, no 2, p. 108-115Article in journal (Refereed)
    Abstract [en]

    One of the major obstacles in the incorporation of nanomaterials in high technology is the lack of new processes for the bulk production of the materials with compositions tailored to suit the application. Oxides can potentially be reduced to metals, intermetallics or alloys by hydrogen or natural gas. The formation of homogeneous alloys and intermetallics by this method has been confirmed by a number of experimental studies. The kinetics of hydrogen reduction of pure oxides of transition metals as well as complex tungstates, molybdates, titanates, aluminates and chromate were investigated by thermogravimetry. The formation of homogeneous alloys and intermetallics was confirmed by these studies. Arrhenius activation energies of the reduction reactions could be linked to the stabilities of the complex oxides. The products were found to have nanograin structure. Bulk processing through hydrogen reduction route was examined in the case of iron molybdate using a fluidized bed reactor.

  • 148. Morita, K.
    et al.
    Sano, N.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Thermodynamic Aspects of Process Metallurgy. Introduction to Thermodynamics of Metallurgical Processes2013In: Treatise on Process Metallurgy, Elsevier, 2013, Vol. 1, p. 395-397Chapter in book (Refereed)
  • 149. Mostaghel, S.
    et al.
    Holmgren, H.
    Matsushita, Taishi
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Samuelsson, C.
    Integrated recycling at Boliden's Rönnskär Smelter; formation of slag products2012In: International Smelting Technology Symposium: Incorporating the 6th Advances in Sulfide Smelting Symposium, 2012, p. 117-124Conference paper (Refereed)
    Abstract [en]

    Rönnskär Smelter of Boliden Mineral AB, Sweden, is a large end-processor of secondary raw materials and waste, including electronic scrap. Electronic scrap may introduce various impurities to the smelter's flow-sheet, among which alumina is a common and significant one. This article summarizes the results of an ongoing research at Luleå University of Technology, Sweden, to study the influences of alumina on different properties of slag from the zinc filming process at Rönnskär smelter. A combination of different experimental techniques and thermodynamic calculations have been used to investigate properties such as density, surface tension, effective thermal diffusivity, viscosity, and melting/leaching behaviors. Results show that the addition of alumina to this slag increases the degree of polymerization of the melt, and physical properties vary correspondingly. Mineralogy of the semi-rapidly solidified samples is also changed due to alumina addition. A correlation between mineralogy and leaching behavior can be observed.

  • 150. Mostaghel, S.
    et al.
    Matsushita, T.
    Samuelsson, C.
    Björkman, B.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Influence of alumina on physical properties of an industrial zinc-copper smelting slag: Part 2 - Apparent density, surface tension and effective thermal diffusivity2013In: Transactions of the Institution of Mining and Metallurgy Section C - Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, E-ISSN 1743-2855, Vol. 122, no 1, p. 49-55Article in journal (Refereed)
    Abstract [en]

    Apparent density, surface tension and effective thermal diffusivity of an industrial iron-silicate based slag and mixtures of this slag with 5, 10 and 15 wt-% alumina addition were measured using the sessile drop and the laser flash techniques respectively. A comparison is made between corresponding values obtained from the commonly applied models and the experimental measurements. Results show that increasing the alumina concentration in slag increases the degree of polymerisation of the melt and, consequently, its effective thermal diffusivity. By alumina addition to the system, the surface tension increases progressively from 338 mN m-1, in the reference slag sample, to 488 mN m-1 in the mixture of slag and 15 wt-% alumina addition. The apparent density of the liquid-solid containing slag is continuously decreased due to the increased alumina concentration. However, the effect is more pronounced between 8 and 12 wt-% total alumina content in the slag.

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