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

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

  • 2.
    Abbasalizadeh, Aida
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Sridhar, Seetharaman
    Grinder, Olle
    Izumi, Yukari
    Barati, Mansoor
    Highlights of the Salt Extraction Process2013Inngår i: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 65, nr 11, 1552-1558 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 3.
    Abbasalizadeh, Aida
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, S.
    Dysprosium extraction using molten salt process2014Inngår i: Rare metal technology 2014: proceedings of a symposium sponsored by The Minerals, Metals & Materials Society (TMS) held during TMS 2014, 143rd Annual Meeting & Exhibition, February 16-20, 2014, San Diego Convention Center, San Diego, California, USA, 2014, 207-208 s.Konferansepaper (Fagfellevurdert)
  • 4.
    Abbasalizadeh, Aida
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Sridhar, S.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Neodymium extraction using salt extraction process2015Inngår i: Transactions of the Institution of Mining and Metallurgy Section C - Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, E-ISSN 1743-2855, Vol. 124, nr 4, 191-198 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 5.
    Abdel-Khalek, N.A.
    et al.
    Central Metallurgical Research and Development Institute (CMRDI), Helwan, Cairo.
    Yassin, K.E.
    Central Metallurgical Research and Development Institute (CMRDI), Helwan, Cairo.
    Kota, Hanumantha Rao
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Kandel, A-H
    Chemistry Department, Faculty of Science, Helwan University.
    Effect of starch type on selectivity of cationic flotation of iron ore2012Inngår i: Transactions of the Institution of Mining and Metallurgy Section C - Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, E-ISSN 1743-2855, Vol. 121, nr 2, 98-102 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cationic flotation is one of the most widely accepted technologies for upgrading siliceous iron ore using polysaccharides (mainly starches) as depressing agents for iron bearing minerals while floating silica with amines. In this paper, a group of starches are investigated as depressants for haematite. These starches are wheat, corn, rice, potato and dextrin. The role of starch type on the selectivity of the separation process has been studied through zeta potential, adsorption measurements as well as flotation tests. The effects of type of starch and pH of the medium have been studied. The results indicate that the selectivity of the separation process is strongly affected by the type of starch used, where better results are obtained with corn starch or wheat starch in comparison to the other types. Fourier transform infrared spectroscopy measurements indicated that the interaction between starches and haematite surface is intermolecular interaction

  • 6.
    Abdul Abas, Riad
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Experimental Studies of Thermal Diffusivities concerning some Industrially Important Systems2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The main objective of this industrially important work was to gain an increasing understanding of the properties of some industrially important materials such as CMSX-4 nickel base super alloy, 90Ti.6Al.4V alloy, 25Cr:6Ni stainless steel, 0.7% carbon steel, AISI 304 stainless steel-alumina composites, mould powder used in continuous casting of steel as well as coke used in blast furnace with special reference to the thermal diffusivities. The measurements were carried out in a wide temperature range covering solid, liquid, glassy and crystalline states.

    For CMSX-4 alloy, the thermal conductivities were calculated from the experimental thermal diffusivities. Both the diffusivities and conductivities were found to increase with increasing temperature. Microscopic analysis showed the presence of intermetallic phases γ´ such as Ni3Al below 1253 K. In this region, the mean free path of the electrons and phonons is likely to be limited by scattering against lattice defects. Between 1253 K and solidus temperature, these phases dissolved in the alloy adding to the impurities in the matrix, which, in turn, caused a decrease in the thermal diffusivity. This effect was confirmed by annealing the samples at 1573 K. The thermal diffusivities of the annealed samples measured at 1277, 1403 and 1531 K were found to be lower than the thermal diffusivities of non-annealed samples and the values did not show any noticeable change with time. It could be related to the attainment of equilibrium with the completion of the dissolution of γ´ phase during the annealing process. Liquid CMSX-4 does not show any change of thermal diffusivity with temperature. It may be attributed to the decrease of the mean free path being shorter than characteristic distance between two neighbouring atoms.

    Same tendency could be observed in the case of 90Ti.6Al.4V alloy. Since the thermal diffusivity increases with increasing temperature below 1225 K and shows slight decrease or constancy at higher temperature. For 25Cr:6Ni stainless steel, the thermal diffusivity is nearly constant up to about 700 K. Beyond that, there is an increase with temperature both during heating as well as cooling cycle. On the other hand, the slope of the curve increases above 950 K, which can be due to the increase of bcc phase in the structure. 0.7% carbon steel shows a decrease in the thermal diffusivity at temperature below Curie point, where the structure contains bcc+ fcc phases. Above this point the thermal diffusivity increases, where the structure contains only fcc phase. The experimental thermal conductivity values of these alloys show good agreement with the calculated values using Mills model.

    Thermal diffusivity measurements as a function of temperature of sintered AISI 304 stainless steel-alumina composites having various composition, viz, 0.001, 0.01, 0.1, 1, 2, 3, 5, 7, 8 and 10 wt% Al2O3 were carried out in the present work. The thermal diffusivity as well as the thermal conductivity were found to increase with temperature for all composite specimens. The thermal diffusivity/conductivity decreases with increasing weight fraction of alumina in the composites. The experimental results are in good agreement with simple rule of mixture, Eucken equation and developed Ohm´s law model at weight fraction of alumina below 5 wt%. Beyond this, the thermal diffusivity/ conductivity exhibits a high discrepancy probably due to the agglomeration of alumina particles during cold pressing and sintering.

    On the other hand, thermal diffusivities of industrial mould flux having glassy and crystalline states decrease with increasing temperature at lower temperature and are constant at higher temperature except for one glassy sample. The thermal diffusivity is increased with increasing crystallisation degree of mould flux, which is expected from theoretical considerations.

    Analogously, the thermal diffusivity measurements of mould flux do not show any significant change with temperature in liquid state. It is likely to be due to the silicate network being largely broken down.

    In the case of coke, the sample taken from deeper level of the pilot blast furnace is found to have larger thermal diffusivity. This can be correlated to the average crystallite size along the structural c-axis, Lc, which is indicative of the higher degree of graphitisation. This was also confirmed by XRD measurements of the different coke samples. The degree of graphitisation was found to increase with increasing temperature. Further, XRD and heat capacity measurements of coke samples taken from different levels in the shaft of the pilot blast furnace show that the graphitisation of coke was instantaneous between 973 and 1473 K.

  • 7.
    Abdul Abas, Riad
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Hayashi, M.iyuki
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Thermal Diffusivity measurement of CMSX-4 alloy by Laser flash method2007Inngår i: International journal of thermophysics, ISSN 0195-928X, E-ISSN 1572-9567, Vol. 28, nr 1, 109-122 s.Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 8.
    Abdul Abas, Riad
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Hayashi, Miyuki
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Thermal Diffusivity Measurements of some Industrially Important Alloys by a Laser Flash Method2007Inngår i: International journal of materials reseach, ISSN 1862-5282, Vol. 98, nr 6, 535-540 s.Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 9.
    Abhale, Prakash Bansi
    et al.
    Global R and D, ArcelorMittal, Kolkatta.
    Yadav, Vishal Kumar
    Department of Metallurgy and Materials Engineering (MTM), Katholieke Universiteit, Leuven.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Ballal, Bharath Nidambur
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Efficient computation of gas flow in blast furnace in 3-D2012Inngår i: 6th Int. Congress on the Science and Technology of Ironmaking 2012, ICSTI 2012: Including Proceedings from the 42nd Ironmaking and Raw Materials Seminar, and the 13th Brazilian Symp. on Iron Ore, 2012, Vol. 1, 722-732 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Blast furnace continues to occupy prominent place among iron making technologies as it accounts for more than 90% of the hot metal produced in the world. In India, as a part of initiative from Ministry of Steel, efforts are being made to develop offline as well as online models with an aim to improve blast furnace performance. As a part of this effort, offline comprehensive models simulating the internal state of an operating blast furnace are being developed. Such comprehensive models involve systematic integration of various sub-models for gas flow, solid flow, reaction kinetics, enthalpy balance etc. Unlike in many other systems, these sub-processes are highly interlinked in blast furnace and hence call for large number of iteration among the sub-models which ultimately results in significant computation time. Our efforts in integration of these sub-models have indicated that the gas flow is one of the important bottle necks in achieving faster computation. This has led to a development of new and efficient computation scheme to simulate the gas flow in 2-D [1]. This new scheme provided efficient way of handling complex burden profile in a blast furnace. This paper presents the extension of this 2-D gas flow model to 3-D. Further, the 3-D model has been used to investigate the asymmetry in gas flow which can arise from blanking the tuyeres, asymmetric fusion or cohesive zone or formation scabs or scaffolds in the furnace behavior

  • 10.
    Abouzari, Sara
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Solid solution strengthening effect on creep strength of austenitic stainless steel2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Sanicro 25 is a newly developed austenitic stainless steel, designed for the next generation of Ultrasupercritical coal-fired boilers in electrical power plants. This material is applicable in reheater and superheater tubes, where the material temperature is up to 700

    °C. One of the main strengthening mechanisms in high temperature materials is solid solution strengthening. A combination of this mechanism and precipitation hardening, promotes creep strength of heat resistance materials. The aim of this work was to characterize the effects of solid solution strengthening on creep strength of Sanicro 25.Previous works has been done for effects of phosphorous in copper and also for influence of laves phase on the creep properties of CrMo alloys. The results of these two works are used and the model is adapted to austenitic stainless steel. First a Zero starting state was defined which was Alloy 316H and then the calculation was made for Sanicro 25. Thermodynamic calculations were made using DICTRA and Thermo-Calc. Elastic misfit parameter was determined using ab initio calculations. The results from the simulation in this work indicate that solutes with larger size misfit compare to the parent atoms have better solid solution strengthening effect. A decrease in the creep strength by increasing temperature has been observed which could be attributed to growth of laves phase.

  • 11.
    Abramov, A.A.
    et al.
    Moscow State Mining University, Moscow.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Chemistry and optimal conditions for copper minerals flotation: theory and practice2005Inngår i: Mineral Processing and Extractive Metallurgy Review, ISSN 0882-7508, E-ISSN 1547-7401, Vol. 26, nr 2, 77-143 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reliable information on the surface state of sulphide copper minerals and regularities of sulphidization and flotation of oxidized copper minerals, the composition of sorption layer on the mineral surface forming during its interaction with xanthate or dixanthogen, and the influence of collector forms sorption on the copper minerals floatability and on the optimal conditions for these minerals flotation and depression has been obtained at present. The determined physicochemical models in the form of quantitative equations have been derived for the optimal conditions of flotation and depression of copper minerals under changing pH value and of sodium sulphide, lime, cyanide, zinc–cyanide complexes additions. The equations derived were proven in the laboratory and industrial scale and can be used both in automatic control systems at plants and for improvement of technological processes of selective flotation of copper containing ores.

  • 12.
    Abrikosov, Igor A.
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Alling, Björn
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Steneteg, Peter
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Hultberg, Lasse
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    Hellman, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Yu Mosyagin, Igor
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten. Department of Theoretical Physics and Quantum Technologies, National Research, Technological University MISiS, Moscow, Russia.
    Lugovskoy, Andrey V.
    Department of Theoretical Physics and Quantum Technologies, National Research, Technological University MISiS, Russia.
    Barannikova, Svetlana A.
    Institute of Strength Physics and Materials Science, Siberian Branch of Russian Academy of Science, Tomsk, Russia; Department of Physics and Engineering, Tomsk State University, Tomsk, Russia.
    Finite Temperature, Magnetic, and Many-Body Effects in Ab Initio Simulations of Alloy Thermodynamics2013Inngår i: TMS2013 Supplemental Proceedings, John Wiley & Sons, 2013, 617-626 s.Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Ab initio electronic structure theory is known as a useful tool for prediction of materials properties. However, majority of simulations still deal with calculations in the framework of density functional theory with local or semi-local functionals carried out at zero temperature. We present new methodological solution.s, which go beyond this approach and explicitly take finite temperature, magnetic, and many-body effects into account. Considering Ti-based alloys, we discuss !imitations of the quasiharmonic approximation for the treatment of lattice vibrations, and present an accurate and easily extendable method to calculate free ,energies of strongly anharmonic solids. We underline the necessity to going beyond the state-of-the-art techniques for the determination of effective cluster interactions in systems exhibiting mctal-to-insulator transition, and describe a unified cluster expansion approach developed for this class of materials. Finally, we outline a first-principles method, disordered local moments molecular dynamics, for calculations of thermodynamic properties of magnetic alloys, like Cr1-x,.AlxN, in their high-temperature paramagnetic state. Our results unambiguously demonstrate importance of finite temperature effects in theoretical calculations ofthermodynamic properties ofmaterials.

  • 13.
    Adegoke, Olutayo
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Homogenization of Precipitation Hardening Nickel Based Superalloys2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Allvac 718 Plus and Haynes 282 are relatively new precipitation hardening nickel based superalloys with good high temperature mechanical properties. In addition, the weldability of these superalloys enhances easy fabrication. The combination of high temperature capabilities and superior weldability is unmatched by other precipitation hardening superalloys and linked to the amount of the γ’ hardening precipitates in the materials. Hence, it is these properties that make Allvac 718 Plus and Haynes 282 desirable in the manufacture of hot sections of aero engine components.

    Studies show that cast products are less weldable than wrought products. Segregation of elements in the cast results in inhomogeneous composition which consequently diminishes weldability. Segregation during solidification of the cast products results in dendritic microstructure with the segregating elements occupying interdendritic regions. These segregating elements are trapped in secondary phases present alongside γ matrix. Studies show that in Allvac 718Plus, the segregating phase is Laves while in Haynes 282 the segregating phase is not yet fully determined.

    Thus, the present study investigated the effects of homogenization heat treatments in eliminating segregation in cast Allvac 718 Plus and Haynes 282. Paramount to the study was the effect of different homogenization temperatures and dwell time in the removal of the segregating phases. Experimental methods used to both qualify and quantify the segregating phases included SEM, EDX analysis, manual point count and macro Vickers hardness tests.

    Main results show that there is a reduction in the segregating phases in both materials as homogenization proceeds hence a disappearance of the dendritic structure. In Allvac 718 Plus, plate like structures is observed to be closely associated with the Laves phase at low temperatures and dwell times. In addition, Nb is found to be segregating in the interdendritic areas. The expected trend of increase in Laves as a result of the dissolution of the plate like structures at the initial stage of homogenization is only detectable for few cases. In Haynes 282, white and grey phases are clearly distinguished and Mo is observed to be segregating in interdendritic areas.

  • 14. Adolfsson, Daniel
    Cementitious properties of steelmaking slags2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The present study is directed towards the use of steelmaking slags as raw material for sulphoaluminate belite cement (SAB). Another important objective was to characterise the cementitious properties of phases in ladle furnace slag (LFS) specifically the calcium aluminates. Mayenite (C12A7) is considered one of the most important calcium aluminate in LFS, and since comparatively limited data on the kinetic properties of this phase are available, it was decided to study C12A7 more closely with regard to both particle size and temperature sensitivity. The behaviour of high-temperature reactions of tested SAB mixtures was investigated using thermogravimetric analysis coupled with a quadrupole mass spectrometer. Mineralogical observations were carried out with x-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The results proved that steelmaking slags have the potential to work as raw material, since sulphoaluminate (C4A3 S ) along with polymorphs of dicalcium silicate (C2S) and ferrite phase (C4AF) were detected after firing at 1200ºC in an air atmosphere. The hydration properties of the specimens were analysed through conduction calorimetry, and compressive strength of specimens hydrated for 2 and 28 days. The compressive strength was in accordance with that suggested in the literature for slow hardening SAB cement. Both mixtures tested behaved the same with regard to heat development as well as the amount of ettringite (AFt) formed during the first 24 hours of the hydration. The formation of AFt was characterised with both differential scanning calorimeter (DSC) and XRD. The crystallographic distribution in LFS samples was quantified using Rietveldanalysis. Calorimetric studies were performed at 20, 25 and 30°C in order to calculate the activation energy of hydration and thereby to suggest a kinetic model for tested compositions within this temperature interval. In addition to heat of hydration, compressive strength tests were completed on mortar prisms of LFS, and LFS in a blend with ground granulated blast furnace slag (GGBFS) which hydrated for 2, 7 and 28 days. Both compositions reached acceptable early strengths, whereas, after 28 days hydration, the blend was superior to neat LFS. Related activation energy was according to the Avrami-Erofeev model determined to 58 kJ/mol for the LFS and 63 kJ/mol for the blend. Corresponding calorimetric studies at the same temperatures were performed on a fine and coarse size fraction (Fraction A and Fraction B) of a synthesised C12A7. The purity was confirmed by XRD, and the hydraulic behaviour was investigated in excess water with respect to the dissolution. The apparent activation energy was calculated to 33 and 79 kJ/mol, respectively, for Fractions A-B using the Avrami-Erofeev model. From the model, it was also concluded that the acceleration period can be ascribed to a phase-boundary controlled mechanism. The principal calcium aluminate hydrates obtained were C2AH8 and C2AH7.5, and it was further observed that C12A7 is accompanied by an anomalous setting behaviour much like monocalcium aluminate (CA), and that the decomposition of C2AH8 to C2AH7.5 develops more slowly with higher surface area, specifically at 20 and 30°C.

  • 15. Adolfsson, Daniel
    Steelmaking slags as raw material for sulphoaluminate belite cement2007Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The present work was undertaken as part of the research in the Minerals and Metals Recycling research centre, MiMeR. The course of the thesis is attributed to metallurgical slags from the steelmaking industry and the possible use of such by-products as raw material for sulphoaluminate belite cement (SAB). Implementing steel slags into the production of cement could contribute to the steel industry's possibility of increasing the recirculation. In addition to the previous objective, the introduction of slag into the cement manufacturing can also facilitate the reduction of carbon dioxide emissions as well as lowering the overall energy consumption during the manufacturing. The reason for this is that the SAB system enables the reduction of the lime saturation factor (LSF) which in turn implies that less limestone is needed in the raw meal. Additionally, the firing temperature can be reduced by about 100-150°C, since dicalcium silicate and sulphoaluminate are formed already at approximately 1200-1250°C. In any event, one should remember that this is not intended to be a final solution for the recycling of slag, nor a replacement for already accepted cement materials. A number of applications currently exist where ordinary Portland cement (OPC) is used, but in cases where the OPC could be replaced with other type of cements, e.g. SAB cement, the possibility of using residues material in cement applications is increased. Considering the clinker covered within this work, possible applications are those where slow hydraulic properties are suitable. The behaviour of high temperature reactions of tested mixtures was investigated using thermogravimetric analysis coupled with a quadrupole mass spectrometer. Mineralogical observations were carried out with x-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The results proved that steelmaking slags have the potential to work as raw material, since sulphoaluminate along with polymorphs of dicalcium silicate and ferrite phases were detected after firing at 1200 ºC in an air atmosphere. The hydraulic properties of the specimens were analysed through conduction calorimetry, XRD, differential scanning calorimetry (DSC) as was the mechanical strength of the specimens when hydrated for 2 and 28 days. The compressive strength was in accordance with that suggested in the literature for slow hardening SAB cement. Both mixtures tested behaved the same with regard to heat development as well as the amount of AFt formed during the first 24 hours of the hydration.

  • 16. Adolfsson, Daniel
    et al.
    Engström, Fredrik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Robinson, Ryan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Cementitious phases in ladle slag2011Inngår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 82, nr 4, 398-403 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ladle slag is an internal by-product generated within the steelmaking industry during the refining of steel. The realisation of beneficial inherent properties of ladle slag as a binder supplement or substitute material is believed to be advantageous with respect to both economy and environment for steelmakers. For this reason, the current study has focused on highlighting the properties of ladle slag that are pertinent to the formation of calcium aluminate hydrates. Three fractions of ladle slag, two of which were based on different slag formers, have been characterised using XRF, XRD and calorimetric analysis. Commonly known hydraulic minerals such as mayenite, tricalcium aluminate and dicalcium silicate were detected during analysis. An important aspect in the utilisation of ladle slag is the slag handling methodology. Therefore, this study also highlights and discusses the need to reconsider slag handling procedures concerning unnecessary exposure to weathering and the possible need for further processing of the slag in order to better employ the inherent hydraulic properties of this material.

  • 17. Adolfsson, Daniel
    et al.
    Menad, Nourreddine
    Viggh, Erik O.
    Bureau de Recherches Géologiques et Minières, Orléans.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Hydraulic properties of sulphoaluminate belite cement based on steelmaking slags2007Inngår i: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605, Vol. 19, nr 3, 133-138 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Based on modified Bogue calculations, steelmaking slags were combined in order to produce a belite-rich clinker activated with sulphoaluminate. The experiments were conducted on two different mixtures based on steelmaking slags together with additives, namely MixA and MixB. The objective of the present study was to investigate the hydraulic properties of the specimens, using conduction calorimetry, X-ray diffraction and differential scanning calorimetry, and also to measure the mechanical strength of the specimens when hydrated for 2 and 28 days. The compressive strength was satisfactory in relation to the estimated compositions. Both mixtures behaved the same with regard to heat development as well as the amount of ettringite formed during the first 24 h of the hydration.

  • 18. Adolfsson, Daniel
    et al.
    Menad, Nourreddine
    Viggh, Erik O.
    Cementa AB, Malmö.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Steelmaking slags as raw material for sulphoaluminate belite cement2007Inngår i: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605, Vol. 19, nr 4, 147-156 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present study, slags from the steelmaking industry are described and considered as a potential raw material within the field of sulphoaluminate belite cement. The objective of the study was to investigate the possibility of using a substantial amount of steelmaking slags as raw meal in the manufacture of a sulphobelitic clinker. A further aim was to compare the influence of different slags in relation to the formation of sulphoaluminate and the other clinker phases required. The behaviour of high temperature reactions was investigated by using thermogravimetric analysis coupled with a quadrupole mass spectrometer. Mineralogical observations were carried out through X-ray powder diffraction, and scanning electron microscopy. Three different mixtures and a single ladle slag were prepared using modified Bogue calculations, which are characterised by the assessment of a potential phase composition in order to produce belite-rich cement activated with sulphoaluminate. The results so far prove that steelmaking slags have the potential to be used as raw material, since sulphoaluminate along with polymorphs of dicalcium silicate and ferrite phases were detected after firing at 1200 degrees C in an air atmosphere.

  • 19. Adolfsson, Daniel
    et al.
    Robinson, Ryan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Blagojevic, J.
    SSAB Tunnplåt AB.
    Su, F.
    SSAB Tunnplåt AB.
    Assessment of ladle slag as binder alternative for cold bonded briquettes2008Inngår i: REWAS 2008: Global Symposium on Recycling, Waste Treatment and Clean Technology ; held October 12 - 15, 2008 in Cancun, Mexico / [ed] B. Mishra; C. Ludwig; S. Das, Minerals, Metals & Materials Society, 2008, 117-123 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Cold bonded briquetting of steel plant by-products has proven to be a viable recycling alternative concerning technology, economy and environment in both the traditional blast furnace route and the direct reduction process. A critical parameter in cold bonded briquettes is the type and amount of binder used during production. The binder material must meet certain quality requirements concerning low and high temperature strength, chemistry and economy. Currently, SSAB Tunnplåt uses ordinary Portland cement (OPC) as binder in their cold bonded briquettes. In order to improve binder quality and possibly decrease OPC dependency, a binder feasibility study has been conducted concerning an internal by-product, ladle slag, as a supplement and/or partial substitute for OPC. Several characterization techniques have been used to study the behaviour of ladle slag, these include: XRD, XRF, SEM, glass content analysis, calorimetric analysis, particle size distribution and thermochemical stability considerations concerning the CaO-Al2O3-SiO 2 system.

  • 20. Adolfsson, Daniel
    et al.
    Robinson, Ryan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Blagojevic, J.
    Su, F.
    Assessment of ladle slag as bnder alternative for cold bonded briquettes2008Inngår i: REWAS 2008: Global Symposium on Recycling, Waste Treatment / [ed] B. Mishra; C. Ludwig; S. Das, Minerals, Metals & Materials Society, 2008, 117-124 s.Konferansepaper (Fagfellevurdert)
  • 21.
    Adolfsson, Daniel
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Robinson, Ryan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Engström, Fredrik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Influence of mineralogy on the hydraulic properties of ladle slag2011Inngår i: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 41, nr 8, 865-871 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present study is aimed at investigating the hydraulic characteristics of ladle furnace slag (LFS), under the pretence of using LFS as a cement substitute in certain applications. Furthermore, LFS has been considered as a possible activator in a blend containing 50% LFS, and 50% ground granulated blast furnace slag (GGBFS). Phases detected in LFS were quantified using Rietveld analysis. Calorimetric studies were performed at 20, 25 and 30 °C in order to calculate the apparent activation energy of hydration and thereby to suggest a kinetic model for the tested compositions within this temperature interval. In addition, compressive strength tests were performed on mortar prisms made with LFS, and LFS/GGBFS which had hydrated for 2, 7 and 28 days. Both compositions reached acceptable early strengths, (e.g. LFS, 33.1 MPa, and LFS/GGBFS, 17.9 MPa, after 2 days), but after 28 days hydration the blend was superior to neat LFS. Related apparent activation energies were determined using an Avrami–Erofeev model and gave Ea = 58 kJ/mol for neat LFS and Ea = 63 kJ/mol for the blend. The results imply that LFS or a LFS/GGBFS blend can be favourably used as supplement in binder applications such as binder in by-product metallurgical briquettes, which are used as recycle to the blast furnace or basic oxygen furnace depending on the specific briquette composition.

  • 22. Adolfsson, Daniel
    et al.
    Viggh, Erik O.
    Cementa AB.
    Steelmaking slags as raw material for calcium sulfoaluminate belite cement2005Inngår i: Securing the future: international conference on mining and the environment, metals and energy recovery : proceedings, Stockholm: SweMin , 2005, 8- s.Konferansepaper (Annet vitenskapelig)
  • 23. Affatato, S.
    et al.
    Leardini, W.
    Jedenmalm, Anneli
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Zavalloni, M.
    Ruggeri, O.
    Tarterini, F.
    Viceconti, M.
    Microstructural effects on the wear resistance of CO-CR implant alloys2006Inngår i: Proceedings of the 8th Biennial Conference on Engineering Systems Design and Analysis, 2006, -951 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Modem metal-on-metal articulation have been proposed to reduce the incidence of osteolysis due to polyethylene particles debris, as a late complication. The tribology of large metal-on-metal articulations allows theoretical advantages with respect to other configurations, especially for the lubrication regime. This study was aimed to compare the wear performances of different diameters of clinically available acetabular metallic components manufactured in a cast cobalt-chrome alloy. To evaluate the influence of the material properties of wear and microstructure, metal-on-metal components were tested in a hip joint simulator for five million cycles with bovine calf serum as lubricant. In particular, three different configurations of metal-on-metal components (28-mm, 36-mm, 54-mm) were tested. After the test all specimens were examined with optical and electronic scanning microscope. A statistical difference were observed among the three groups tested in the run-in and steady-state wear rates, favoring the larger femoral heads. The results of this study indicate that the 54-mm diameter femoral heads prove a better wear behavior than the smaller configurations.

  • 24.
    Aghasibeig, Maniya
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Laser cladding of a featureless iron-based alloy2012Inngår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 209, 32-37 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Laser cladding experiments with powder injection technique were carried out to create coatings of Fe-8.1Cr6.4Mn-5.3Si-6.9Mo-3.6C alloy on AISI 1018 steel substrates using a diode laser. Analysis of the clad layers showed that an almost featureless structure was formed at different dilutions between 1% and 4%. The featureless phase with a high hardness of 1155 HV was characterized as a metastable solid solution of e phase. However, the featureless structure appeared to be very brittle with numerous cracks. After heat-treatment, it decomposed into a bainitic structure with a high hardness of 884 HV.

  • 25.
    Ahlberg, E.
    et al.
    Chalmers University of Technology, Department of Inorganic Chemistry.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Wang, Xianghuai
    Luleå tekniska universitet.
    The surface oxidation of pyrite in alkaline solution1990Inngår i: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 20, nr 6, 1033-1039 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The collector-less flotation of pyrite has been studied by conventional techniques and is correlated to the electrochemical behaviour of pyrite in alkaline solution (1m NaClO4, pH 11). It was concluded that the initial oxidation of pyrite produces a hydrophobic sulphur rich surface together with hydrophilic iron hydroxide species. Also upon grinding, the surface is covered by hydrophilic species and therefore no significant flotation was obtained in the absence of a collector. However, collectorless flotation was readily obtained in an iron complexing solution like EDTA. This indicates that the remaining sulphur-rich layer is responsible for the floatability of pyrite under these conditions

  • 26.
    Ahlin, Björn
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Gärdin, Marcus
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Automated Classification of Steel Samples: An investigation using Convolutional Neural Networks2017Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Automated image recognition software has earlier been used for various analyses in the steel making industry. In this study, the possibility to apply such software to classify Scanning Electron Microscope (SEM) images of two steel samples was investigated. The two steel samples were of the same steel grade but with the difference that they had been treated with calcium for a different length of time. 

    To enable automated image recognition, a Convolutional Neural Network (CNN) was built. The construction of the software was performed with open source code provided by Keras Documentation, thus ensuring an easily reproducible program. The network was trained, validated and tested, first for non-binarized images and then with binarized images. Binarized images were used to ensure that the network's prediction only considers the inclusion information and not the substrate.

    The non-binarized images gave a classification accuracy of 99.99 %. For the binarized images, the classification accuracy obtained was 67.9%.  The results show that it is possible to classify steel samples using CNNs. One interesting aspect of the success in classifying steel samples is that further studies on CNNs could enable automated classification of inclusions. 

  • 27.
    Ahmad, Yousef
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Oxidation of Graphite and Metallurgical Coke: A Numerical Study with an Experimental Approach2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    At the royal institute of technology (KTH) in the department of applied process metallurgy, a novel modelling approach has been developed which allows a dynamic coupling between the commercial thermodynamic software Thermo-Calc and the commercial computational fluid dynamic (CFD) software Ansys Fluent, only referred to as Fluent in the study. The dynamic coupling approach is used to provide numerical CFD-models with thermodynamic data for the thermo-physical properties and for the fluid-fluid chemical reactions occurring in metallurgical processes. The main assumption forthe dynamic coupling approach is the existence of local equilibrium in each computational cell. By assuming local equilibrium in each computational cell it is possible to use thermodynamic data from thermodynamic databases instead of kinetic data to numerically simulate chemical reactions. The dynamic coupling approach has been used by previous studies to numerically simulate chemical reactions in metallurgical processes with good results. In order to validate the dynamic coupling approach further, experimental data is required regarding surface reactions. In this study, a graphiteand metallurgical coke oxidation experimental setup was suggested in order to provide the needed experimental data. With the experimental data, the ability of the dynamic couplings approach to numerically predict the outcome of surface reactions can be tested.By reviewing the literature, the main experimental apparatus suggested for the oxidationexperiments was a thermo-gravimetric analyzer (TGA). The TGA can provide experimental data regarding the reaction rate, kinetic parameters and mass loss as a function of both temperature and time. An experimental setup and procedure were also suggested.In order to test the ability of Fluent to numerically predict the outcome of surface reactions, without any implementation of thermodynamic data from Thermo-Calc, a benchmarking has been conducted. Fluent is benchmarked against graphite oxidation experiments conducted by Kim and No from the Korean advanced institute of science and technology (KAIST). The experimental graphite oxidation rates were compared with the numerically calculated graphite oxidation rates obtained from Fluent. A good match between the experimental graphite oxidation rates and the numerically calculated graphite oxidation rates were obtained. A parameter study was also conducted in order to study the effect of mass diffusion, gas flow rate and the kinetic parameters on the numerically calculated graphite oxidation rate. The results of the parameter study were partially supported by previous graphite oxidation studies. Thus, Fluent proved to be a sufficient numerical tool for numerically predicting the outcome of surface reactions regarding graphite oxidation at zero burn-off degree.

  • 28.
    Ahmadi, R.
    et al.
    Iran Mineral Processing Research Centre (IMPRC), Karaj.
    Hashemzadehfini, M.
    Iran Mineral Processing Research Centre (IMPRC), Karaj.
    Parian, Mehdi Amiri
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Rapid determination of Bond rod-mill work index by modeling the grinding kinetics2013Inngår i: Advanced Powder Technology, ISSN 0921-8831, E-ISSN 1568-5527, Vol. 24, nr 1, 441-445 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Generally, Bond work index is a common method for selecting comminution equipment as well as estimation of grinding efficiency and calculating required power. In the current research, a simple, fast and accurate procedure is introduced to find the rod-mill work index based on the conventional Bond work index. The grinding experiments were carried out on four typical samples of iron, copper, manganese and lead–zinc ore with three test-sieves in specified time periods and aimed to shortening the procedure. Furthermore, the grinding kinetics and mass balance equations were applied to model the standard Bond rod-mill work index. For comparing the standard Bond rod-mill work index and the new modeled method, work index (Wi) and produced fine particles in a cycle (Gi) for the four samples determined. The performed paired Student’s t-test results indicated that the Standard Deviation for Gi and Wi obtained by the shortened method are respectively 0.50 and 0.58 in respect of traditional Bond method.

  • 29.
    Ahmed, Hesham
    Skolan för industriell teknik och management, Kungliga Tekniska högskolan.
    Investigations of the Kinetics of Reduction and Reduction/Carburization of NiO-WO3 Precursors.2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Kinetic studies of reduction of the mixtures of NiO and WO3 having different Ni/(Ni+W) molar ratios in flowing hydrogen gas were investigated by means of Thermo Gravimetric Analysis (TGA), Fluidized Bed (FB) technique as well as Thermal diffusivity measurements under isothermal conditions. In the case of TGA, the reaction progress was monitored by mass loss, while evolved gas analysis by a gas chromatograph was the indicator of the reaction progress in the case of FB. The results indicate that the reduction reaction proceeds through three consecutive steps, viz.NiO-WO3 Ni-WO3 Ni-WO2 Ni-WThe present results show 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.During the investigations, it was found that there was a delay in the reaction during the hydrogen reduction of NiO-WO3 mixed oxides in a fluidized bed reactor. In order to understand the same, a theoretical model was developed to estimate the apparent reaction rate constant for the reduction reaction from the intrinsic chemical reaction rate constant. Appropriate differential mass balance equations based on intrinsic chemical reaction rate constants and thermodynamic equilibria were developed. The proposed model was successfully applied in predicting the overall reaction kinetics of a fluidized bed reactor. This model is also suitable for scale-up calculations.SEM images showed that the particle size of the final product was dependent on the Ni/(Ni+W) molar ratio; smaller particles were formed at higher nickel contents. X-ray diffractions of the reduced precursors exhibited slight shift of Ni peaks from the standard one indicating the dissolution of W into Ni.A new method for studying kinetics of the hydrogen reduction of NiO-WO3 precursors was developed in which the reaction progress was monitored by following the change of thermal diffusivity of the precursors. Activation energies of reduction as well as sintering were calculated. This method is considered unique as it provides information regarding the physical changes like sintering, change of porosity and agglomeration along with the chemical changes occurring during the gas/solid reaction.As a continuation of the kinetic studies, Ni-W-C ternary carbides were synthesized by simultaneous reduction–carburization of Ni-W-O system using H2-CH4 gas mixtures by TGA. The results showed that the 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. The above-mentioned experiments were conducted in such a way to ensure that the reaction was controlled by the chemical reaction. The activation energies of the reduction as well as carburization processes at different stages were calculated accordingly.The present dissertation demonstrates the potential of the investigations of gas/solid reactions towards tailoring the process towards materials with optimized properties as for example introduction of interstitials. The present process design is extremely environment-friendly with reduced number of unit processes and the product being H2O.

  • 30.
    Ahmed, Hesham
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Andersson, Anton
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    El-Tawil, Asmaa
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Lotfian, Samira
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Alternative Carbon Sources for Reduction2015Konferansepaper (Annet vitenskapelig)
  • 31.
    Ahmed, Hesham
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Andersson, Charlotte
    LKAB, Research & Development, 983 81 Malmberget, LKAB Research and Development.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Effect of olivine fineness and thermal profile on oxidation-sintering of magnetite concentrate pellets2015Inngår i: AISTech 2015: Proceedings of the Iron & Steel Technology Conference : 4-7 May 2015, Cleveland, Ohio, U.S.A / [ed] Ronald E Ashburn, Warrendale, PA: Association for Iron & Steel Technology , 2015, 379-388 s.Konferansepaper (Fagfellevurdert)
  • 32.
    Ahmed, Hesham
    et al.
    Department of Materials Science and Engineering, Royal Institute of Technology.
    El-Geassy, Abdel Hady
    Central Metallurgical Research and Development Institute (CMRDI), Helwan, Cairo.
    Seetharaman, Seshadri
    Kungliga tekniska högskolan, KTH.
    Kinetics of Reduction of NiO–WO3 Mixtures by Hydrogen2010Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, nr 1, 161-172 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The kinetics of reduction of the oxide mixtures of Ni-W with different Ni/(Ni-W) molar ratios within the range of 923 K to 1173 K in flowing hydrogen gas was investigated by means of thermogravimetric analysis under isothermal conditions. The products were examined by X-ray diffraction, scanning electron microscope (SEM), and electron dispersion spectroscopy (EDS) analyses. Five different oxide mixtures apart from the pure oxides were studied in the present work. The results indicate that the reduction reaction proceeds through three consecutive steps that are as follows:NiO-WO3→Ni-WO3→Ni-WO2→Ni-WFrom 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.

  • 33.
    Ahmed, Hesham
    et al.
    Department of Materials Science and Engineering, Royal Institute of Technology.
    Geasyy, Abdel Hady El
    Central Metallurgical Research and Development Institute (CMRDI), Helwan, Cairo.
    Nurni, Viswanathan
    Indian Institute of Technology (IIT).
    Seetharaman, Seshadri
    Kungliga tekniska högskolan, KTH, Department of Metallurgy, Royal Institute of Technology, Stockholm, Division of Metallurgy, Department of Materials Science and Technology, Royal Institute of Technology.
    Kinetics and mathematical modeling of hydrogen reduction of NiO-WO 3 precursors in fluidized bed reactor2011Inngår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, nr 9, 1383-1391 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, Fluidized bed reduction of NiO-WO 3 precursors was investigated isothermally at temperatures 973-1 273 K. The reaction progress was monitored by analysis of 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.

  • 34.
    Ahmed, Hesham M.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Investigations of the Kinetics of Reduction and Reduction/Carburization of NiO-WO3 Precursors.2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Kinetic studies of reduction of the mixtures of NiO and WO3 having different Ni/(Ni+W) molar ratios in flowing hydrogen gas were investigated by means of Thermo Gravimetric Analysis (TGA), Fluidized Bed (FB) technique as well as Thermal diffusivity measurements under isothermal conditions. In the case of TGA, the reaction progress was monitored by mass loss, while evolved gas analysis by a gas chromatograph was the indicator of the reaction progress in the case of FB. The results indicate that the reduction reaction proceeds through three consecutive steps, viz.

    NiO-WO3 Ni-WO3 Ni-WO2 Ni-W

    The present results show 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.

    During the investigations, it was found that there was a delay in the reaction during the hydrogen reduction of NiO-WO3 mixed oxides in a fluidized bed reactor. In order to understand the same, a theoretical model was developed to estimate the apparent reaction rate constant for the reduction reaction from the intrinsic chemical reaction rate constant. Appropriate differential mass balance equations based on intrinsic chemical reaction rate constants and thermodynamic equilibria were developed. The proposed model was successfully applied in predicting the overall reaction kinetics of a fluidized bed reactor. This model is also suitable for scale-up calculations.

    SEM images showed that the particle size of the final product was dependent on the Ni/(Ni+W) molar ratio; smaller particles were formed at higher nickel contents. X-ray diffractions of the reduced precursors exhibited slight shift of Ni peaks from the standard one indicating the dissolution of W into Ni.

    A new method for studying kinetics of the hydrogen reduction of NiO-WO3 precursors was developed in which the reaction progress was monitored by following the change of thermal diffusivity of the precursors. Activation energies of reduction as well as sintering were calculated. This method is considered unique as it provides information regarding the physical changes like sintering, change of porosity and agglomeration along with the chemical changes occurring during the gas/solid reaction.

    As a continuation of the kinetic studies, Ni-W-C ternary carbides were synthesized by simultaneous reduction–carburization of Ni-W-O system using H2-CH4 gas mixtures by TGA. The results showed that the 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. The above-mentioned experiments were conducted in such a way to ensure that the reaction was controlled by the chemical reaction. The activation energies of the reduction as well as carburization processes at different stages were calculated accordingly.

    The present dissertation demonstrates the potential of the investigations of gas/solid reactions towards tailoring the process towards materials with optimized properties as for example introduction of interstitials. The present process design is extremely environment-friendly with reduced number of unit processes and the product being H2O.

  • 35.
    Ahmed, Hesham M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    El-Geassy, Abdel-Hady A.
    Viswanathan, Nurni Neelakantan
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Kinetics and Mathematical Modeling of Hydrogen Reduction of NiO-WO(3) Precursors in Fluidized Bed Reactor2011Inngår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, nr 9, 1383-1391 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 36.
    Ahmed, Hesham M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Reduction-Carburization of NiO-WO3 Under Isothermal Conditions Using H2-CH4 Gas Mixture2010Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, nr 1, 173-181 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 37.
    Ahmed, Hesham
    et al.
    Department of Materials Science and Engineering, Royal Institute of Technology.
    Mis, Mikeal
    Kungliga tekniska högskolan, KTH.
    El-Geassy, A.H.A.
    Department of Minerals Technology and Processing, Central Metallurgical Research and Development Institute (CMRDI), Cairo.
    Seetharaman, Seshadri
    Division of Materials Process Science, Department of Materials Science and Engineering, Royal Institute of Technology, Kungliga tekniska högskolan, KTH, Department of Metallurgy, Royal Institute of Technology, Stockholm, Division of Metallurgy, Department of Materials Science and Technology, Royal Institute of Technology.
    Reduction-Carburization of the Oxides of Ni and W towards the Synthesis of Ni-WC Carbides2010Inngår i: Advanced Materials Forum V: selected, peer reviewed papers from the V International Materials Symposium MATERIAiS 2009 (14th meeting of SPM - Sociedade Portuguesa de Materiais), Instituto Superior Técnico, Technical University of Lisbon, April 5 - 8, Lisbon, Portugal, 2009 / [ed] Luís Guerra Rosa; Fernanda Margarido, Stafa-Zurich: Trans Tech Publications Inc., 2010, 952-962 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Ternary Ni-W-C cemented carbides were synthesized directly from mixture powder of NiO-WO3 by simultaneous reduction-carburization in mixed H2-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.

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

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

  • 39.
    Ahmed, Hesham
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi. Department of Minerals Technology, Central Metallurgical Research and Development Institute.
    Morales-Estrella, Ricardo
    Instituto de Investigación en Metalurgia y Materiales, Universidad Michoacana de San Nicolás de Hidalgo.
    Viswanathan, Nurin
    Centre of Excellence in Steel Technology (CoEST), Indian Institute of Technology Bombay.
    Seetharaman, Seshadri
    Royal Institute of Technology (KTH), Stockholm.
    Gas-solid reaction route toward the production of intermetallics from their corresponding oxide mixtures2016Inngår i: Metals, ISSN 2075-4701, Vol. 6, nr 8, 190Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Near-net shape forming of metallic components from metallic powders produced in situ from reduction of corresponding pure metal oxides has not been explored to a large extent. Such a process can be probably termed in short as the “Reduction-Sintering” process. This methodology can be especially effective in producing components containing refractory metals. Additionally, in situ production of metallic powder from complex oxides containing more than one metallic element may result in in situ alloying during reduction, possibly at lower temperatures. With this motivation, in situ reduction of complex oxides mixtures containing more than one metallic element has been investigated intensively over a period of years in the department of materials science, KTH, Sweden. This review highlights the most important features of that investigation. The investigation includes not only synthesis of intermetallics and refractory metals using the gas solid reaction route but also study the reaction kinetics and mechanism. Environmentally friendly gases like H2, CH4 and N2 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.

  • 40.
    Ahmed, Hesham
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Mousa, E.A.
    Minerals Technology Division, Central Metallurgical Research and Development Institute, 87-Helwan, Cairo.
    Larsson, Mikael
    Process Integration Department, Swerea MEFOS.
    Viswanathan, Nurni
    Department of Metallurgical Engineering and Materials Science, Centre of Excellence in Steel Technology (CoEST), IIT Bombay.
    Recent Trends in Ironmaking Blast Furnace Technology to Mitigate CO2 Emissions: Top Charging Materials2016Inngår i: Ironmaking and Steelmaking Processes: Greenhouse Emissions, Control, and Reduction / [ed] Pasquale Cavaliere, Springer International Publishing , 2016, 101-124 s.Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    The iron- and steelmaking is the largest energy consuming in the industrial sectors. The high energy consumption is associated with emission of CO 2and other pollutants. The most common ironmaking process used in the world is the blast furnace which contributes around 70 % of the world’s steel production. Recently, blast furnace has undergone tremendous modifications and improvements to reduce the energy consumption and CO 2emissions. The modifications are being focused on two main approaches: (1) development of top charging materials and (2) injections of auxiliary fuels through blast furnace tuyeres. The present chapter will discuss the recent modifications and development in the top charging burden and how it could participate in minimizing the energy consumption and CO 2emissions for more efficient and sustainable iron and steel industry. The injection of auxiliaryfuels will be discussed in details in another chapter. The enhancement of burden material quality and its charging mode into the blast furnace has resulted in a smooth and efficient operation. Recently, the usage of nut coke in the modern blast furnace is accompanied by higher production and lower reducing agent rates. An efficient recycling of in-plant fines by its conversion into briquettes with proper mechanical strength is applied in some blast furnaces to exploit the iron- and carbon-rich residues. Nowadays, novel composite agglomerates consist of iron ores and alternative carbonaceous materials represent a new trend for low-carbon blast furnace with lower dependence on the conventional burden materials. The recent investigations demonstrated that the novel composites are able to reduce the thermal reserve zone temperature in the blast furnace and consequently enhance the carbon utilization through its higher reactivity compared to fossil fuels. The top charging of bioreducers and hydrogen-rich materials into the blast furnace is one of interesting innovations to mitigate the CO 2emissions. Although some of previous approaches are recently applied in the modern blast furnace, others are still under intensive discussions to enhance its implementations.

  • 41.
    Ahmed, Hesham
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Composite pellets: a potential raw material for iron-making2014Inngår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, nr 3, 293-306 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Coke constitutes the major portion of iron-making cost and its production causes severe environmental concerns. In addition, lower energy consumption, lower CO2 emission and waste recycling are driving the Iron and steel making industry to develop “coke free, zero waste or green processes”. In the present article, an overview of possible ways to recognize a reasonable improvement in iron and steel making industry is summarized. The present discussion is focusing on the following approaches: 1. Replacing expensive coke with relatively less expensive alternate fuels having carbon as well as significant amount of hydrogen such as coal, waste plastic and biomass materials.2. Producing agglomerates from cheaper raw materials (secondary resources) as well as improving their performance in BF.3.Making the process towards higher carbon utilization by shifting the wustite equilibrium towards lower CO/CO2 ratio by using high reactive coke or catalytic activated one.4.Recycling the unused CO in the top gas by removing CO2 from the gas stream.Much attention has been paid to carbon composite agglomerates (CCA) as a promising raw material for future iron making. Production, mechanical and chemical suitability, reduction behavior, etc. are being elaborated. In addition, other possible ways to utilize CCA in alternate iron-making process has been explored.

  • 42.
    Ahmed, Hesham
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Isothermal reduction kinetics of self-reducing mixtures2017Inngår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 44, nr 1, 66-75 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Isothermal reduction of haematite carbon mixtures was investigated at temperatures 750–1100°C under inert atmosphere. Mass loss curves proved the stepwise reduction of haematite to metallic iron. The non-linear feature of haematite to magnetite reduction kinetics was observed and an activation energy of 209 kJ mol−1 was calculated. Irrespective of carbon-bearing material type, reduction rate of magnetite was linear. Activation energy values were calculated to be 293–418 kJ mol−1. Significant increase in the reduction kinetics in the last step (Wustite reduction) was observed and explained by the catalytic effect of freshly formed metallic iron. During the initial stages of wustite reduction, the activation energy values were calculated to be in the range of 251–335 kJ mol−1 for all carbon-bearing materials.

  • 43.
    Ahmed, Hesham
    et al.
    Royal Institute of Technology (KTH), Stockholm.
    Nurni, Viswanathan
    Indian Institute of Technology, Bombay.
    Seetharaman, Seshadri
    Division of Materials Process Science, Department of Materials Science and Engineering, Royal Institute of Technology, Kungliga tekniska högskolan, KTH, Department of Metallurgy, Royal Institute of Technology, Stockholm, Division of Metallurgy, Department of Materials Science and Technology, Royal Institute of Technology.
    Dynamic thermal diffusivity measurements: A tool for studying gas-solid reactions2011Inngår i: Diffusion in Solids and Liquids VI: selected, peer reviewed papers from the 6th International Conference on Diffusion in Solids and Liquids : mass transfer, heat transfer, microstructure & properties, nanodiffusion and nanostructured materials : DSL-2010, 5-7 July 2010, Paris, France / [ed] Andreas Öchsner; Graeme E. Murch ; João M.P.Q. Delgado, Durnten-Zurich: Trans Tech Publications Inc., 2011, Vol. 312-315, 217-222 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the present work, the thermal diffusivity measurements of uniaxially cold pressed NiWO4 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.

  • 44.
    Ahmed, Hesham
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Persson, Amanda
    Swerea MEFOS AB.
    Sundqvist, Lena
    Swerea MEFOS AB.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Energy Efficient Recycling of in-Plant Fines2014Inngår i: Proceedings of World Academy of Science, Engineering and Technology, ISSN 2010-376X, E-ISSN 2070-3740, Vol. 8, nr 6, 485-491 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    —Numerous amounts of metallurgical dusts and sludge containing iron as well as some other valuable elements such as Zn, Pb and C are annually produced in the steelmaking industry. These alternative iron ore resources (fines) with unsatisfying physical and metallurgical properties are difficult to recycle. However, agglomerating these fines to be further used as a feed stock for existing iron and steel making processes is practiced successfully at several plants but for limited extent. In the present study, briquettes of integrated steelmaking industry waste materials (namely, BF-dust and sludge, BOF-dust and sludge) were used as feed stock to produce direct reduced iron (DRI). Physical and metallurgical properties of produced briquettes were investigated by means of TGA/DTA/QMS in combination with XRD. Swelling, softening and melting behavior were also studied using heating microscope.

  • 45.
    Ahmed, Hesham
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Persson, Amanda
    Swerea MEFOS AB.
    Sundqvist, Lena
    Swerea MEFOS AB.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Utilization of Steelmaking Industry Waste Materials in Producing Direct Reduced Iron2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The depletion of coke reserves and the raised environmental concerns motivated researchers to work on alternative iron-making processes. Large amount of metallurgical dusts and sludge containing iron and C are produced in the steelmaking industry. These alternative iron ore resources (fines) with poor hydrophilicity are difficult to recycle. The idea of briquetting such wastes containing iron to be used as a feed stock for steelmaking industry is practiced successfully at several plants.In the present study, agglomerates of integrated steelmaking industry waste materials were used as feed stock to produce direct reduced iron (DRI). The reduction behavior of blends of different waste materials (namely, BF dust and sludge, BOF dust and sludge) were investigated thoroughly utilizing TGA/DTA/QMS in combination with XRD.

  • 46.
    Ahmed, Hesham
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Persson, Amanda
    Swerea MEFOS AB.
    Sundqvist-Ökvist, Lena
    Swerea MEFOS AB, Luleå tekniska universitet, SSAB Tunnplåt AB, LKAB.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Reduction Behaviour of Self-reducing Blends of In-plant Fines in Inert Atmosphere2015Inngår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 55, nr 10, 2082-2089 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Large amount of dust and sludge recovered during cleaning of iron and steel making process gases are annually put on landfill or intermediate storage. These by-products have high contents of iron (Fe) and carbon (C) that potentially could be utilized in the steel industry. However, due to the presence of impuritycompounds as well as the unsuitable physical properties, these by-products cannot be recycled directly. The main objective of the present study is to investigate the possibilities to recover the valuable components Fe and C in these by-products and thereby decrease the need of landfills at the steel plants as well as reduce the consumption of virgin materials, including fossil coal, and reduce CO2 emissions. A recycling route has been investigated by means of laboratory trials and FactSage thermodynamic modeling. Four different blends of BF and BOF dusts and sludges are prepared in predetermined ratios. Reduction behavior of each blend is studied using TG/DTA/QMS and in-situ high temperature X-ray diffraction. High temperature physical properties like softening, swelling and melting are also investigated by means of heatingmicroscope. The obtained results indicate the feasibility of both minimizing the impurity elements as well as recovering of valuable components.

  • 47.
    Ahmed, Hesham
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Seetharaman, Seshadri
    Kungliga tekniska högskolan, KTH.
    Isothermal dynamic thermal diffusivity studies of the reduction of NiO and NiWO4 precursors by hydrogen2011Inngår i: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, Vol. 102, nr 11, 1336-1344 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermal diffusivity measurements of uniaxially cold pressed NiO and NiWO4 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 NiWO4, 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.

  • 48.
    Ahmed, Hesham
    et al.
    Department of Materials Science and Engineering, Royal Institute of Technology.
    Seetharaman, Seshadri
    Kungliga tekniska högskolan, KTH.
    Reduction-Carburization of NiO-WO3 Under Isothermal Conditions Using H2-CH4 Gas Mixture2010Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, nr 1, 173-181 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 49.
    Ahmed, Hesham
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Viswanathan, Nurni
    Department of Metallurgical Engineering and Materials Science, Centre of Excellence in Steel Technology (CoEST), IIT Bombay.
    Seetharaman, Seshadri
    Division of Materials Process Science, KTH-Royal Institute of Technology .
    Gas-Condensed Phase Reactions: A Novel Route to Synthesize Alloys and Intermetallics Involving Refractory Metals2016Inngår i: Materials Today: Proceedings, E-ISSN 2214-7853, Vol. 3, nr 9 Part B, 2951-2961 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 50.
    Ajayi, John Ade
    et al.
    Department of Metallurgical and Materials Engineering, Federal University of Technology, P.M.B 704, Akure.
    Awe, Samuel Ayowole
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Recovery efficiency study on ilesha placer gold ore by flotation using locallysourced frothers and collectors2010Inngår i: XXV International Mineral Processing Congress: IMPC 2010, "Smarter processing for the future" : Brisbane, Australia 6-10 September 2010 : congress proceedings, Carlton, Vic: The Australasian Institute of Mining and Metallurgy, 2010, Vol. 2, 1695-1702 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The research conducted by the defunct Nigerian Mining Corporation revealed that minable quantities of gold deposit are present over an expanse of Ilesha-Ife area. This optimism prompted several researchers to study the response of Ilesha gold ore to amalgamation and cyanidation. Unfortunately, these methods (amalgamation and cyanidation) are environmentally hazardous and the reagents are rather expensive when available. This is the thrust for this research which is aimed at studying the amenability of Ilesha placer gold ore to froth flotation which is environmentally friendly using locally-sourced reagents. The mineralogical study of the deposit was carried out and the result showed that the Ilesha placer deposit is non-refractory with fine-grained gold particles. Potassium salts of groundnut and palm kernel oils (as collectors) and their fatty acids (as frothers) were prepared and used to float gold concentrate from Ilesha placer gold ore. The following flotation parameters: pulp density, impeller speed, pulp pH, collector concentration and particle size analysis were optimised. The results obtained shows that optimum recovery of 91.8 per cent and 89.56 per cent of gold concentrates were obtained at pulp pH of 9, pulp density of 100 g/cm3, impeller velocity of 1350 rpm and mineral particle size range of -75 μm when potassium salts of groundnut and palmkernel oils were used respectively as collectors. Thus Ilesha placer gold ore is amenable to froth flotation using locally-sourced frothers and collectors.

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