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  • 201.
    Awe, Samuel Ayowole
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Elimination and recovery of antimony from copper resources2013Conference paper (Refereed)
    Abstract [en]

    In a response to the recent growth in the global demand for copper products, mining industries have intensified in their mining operations. Unfortunately, the grade of copper ore concentrates mined today is declining due to the intensive mining of the relatively high grade copper resources. Therefore, future copper ore deposits to be mined are likely to be richer in impurity elements like antimony and arsenic which attract smelter’s penalty if the content of these impurities is too high. It is however imperative to selectively eliminate and recover the antimony impurity of the copper concentrates in an environmentally friendly process with a view of upgrading the concentrates for a pyrometallurgical processing.This paper discusses the alkaline sulphide hydrometallurgical technology to selectively solubilize antimony impurity from a copper concentrate. The effect of sodium sulphide and sodium hydroxide concentrations, leaching time and leaching temperature on antimony dissolution will be examined. Furthermore, antimony recovery as a marketable product from simulated pregnant leach liquor through electrodeposition will be discussed. Various experimental factors that influence antimony deposition from alkaline sulphide electrolyte are reported.

  • 202.
    Awe, Samuel Ayowole
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Electrowinning of antimony from model sulphide alkaline solutions2013In: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 137, p. 60-67Article in journal (Refereed)
    Abstract [en]

    The influence of initial antimony concentration, cathode current density, the concentrations of Na2S and NaOH, gas sparging and electrolyte temperature on average cell voltage, specific energy and current efficiency of antimony deposition has been studied. The experiments were conducted in a nondiaphragm electrolytic cell. Results revealed that increase in initial antimony concentration, temperature of the electrolyte and NaOH concentration enhanced the current efficiency. Excessive sodium sulphide concentration in the electrolyte promotes the formation of unwanted polysulphide and thiosulphate ions which can significantly decrease the current efficiency of the process. Sparging of the electrolyte facilitates a smooth and adherent antimony deposit with an improved purity. About 99.6% antimony purity was achieved when the electrolyte was sparged at 10 mL/min. The result showed that increase in NaOH concentration considerably promotes the formation of sulphate ions as the main anodic product. Anodic current efficiencies of 98% and 99% based on the amount of sulphate formed were obtained at sodium hydroxide concentrations of 8.75 M and 10 M, respectively. Average cell potential increased with increasing NaOH concentration and cathode current density. The preferred crystallographic orientations of the antimony deposit obtained at 2.5 M NaOH concentration are in the orders (012) (202) (110) (104), but the order becomes (012) (110) (104) (202) when NaOH concentration is increased further. The order of crystal orientations for antimony electrodeposition at 50 A/m2 cathodic current density is (012) (110) (104) (202), which does not change with increasing cathode current density but the peaks at (110) (104) (202) crystal planes become more broadened and suppressed as current density increased.

  • 203. Awe, Samuel Ayowole
    et al.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Leaching mechanism of tetrahedrite in alkaline sulfide solution2010In: Conference in Minerals Engineering: Luleå, 2 -3 februari 2010, Luleå tekniska universitet, 2010, p. 13-24Conference paper (Other academic)
    Abstract [en]

    The dissolution kinetics of tetrahedrite in aqueous alkaline sodium sulfide solutions was investigated in this present study. The effect of mineral particle size, reaction temperature, sodium sulfide and sodium hydroxide concentrations on the rate of dissolving antimony from tetrahedrite were studied. The result reveals that the rate of reaction increases with increasing reaction temperature, sodium sulfide concentration, sodium hydroxide concentration and with decreasing mineral particle size. The kinetics study indicates that tetrahedrite leaching rate by the lixiviant under the selected conditions is chemically controlled through the particle surface reaction. Therefore, the activation energy of antimony dissolution from tetrahedrite was estimated to be 81 kJ/ mol, which is in agreement with the value reported for the chemically controlled reactions process.

  • 204. Awe, Samuel Ayowole
    et al.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Selective leaching of arsenic and antimony from a tetrahedrite rich complex sulphide concentrate using alkaline sulphide solution2010In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 23, no 15, p. 1227-1236Article in journal (Refereed)
    Abstract [en]

    Removal of impurity elements in copper metallurgy is one of the major problems encountered today since pure copper ore reserves are becoming exhausted, and the resources of unexploited ores often contain relatively high amounts of impurity elements like antimony, arsenic, mercury and bismuth, which need to be eliminated. The present work is aimed at pre-treating a tetrahedrite rich complex sulphide concentrate by selective dissolution of the impurities, therefore, upgrading it for pyrometallurgical processing. To accomplish this, dissolution of antimony and arsenic by an alkaline sulphide lixiviant from the concentrate were investigated. The lixiviant proved selective and effective to dissolve these impurity elements from the concentrate with good recoveries. Further investigations on the factors influencing the leaching efficiency of the lixiviant were studied. The parameters considered were sulphide ion and hydroxide ion concentrations, mineral particle size, reaction temperature and leaching time. Analysis of the leach residue indicates that copper content of tetrahedrite has transformed into copper sulphides with the average chemical formula Cu1.64S. The grade and economic value of the concentrate were improved greatly after sulphide treatment, and therefore, suitable as a feedstock for smelting. The impurities have been reduced to low levels which are tolerable in the smelting furnace and consequently reduce both the treatment and environmental problem encountered when such concentrate is processed pyrometallurgically.

  • 205.
    Awe, Samuel Ayowole
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Tratamiento hidro-electrometalúrgicos de un concentrado de cobre con contenido de tetraedrita2014In: Mineria, ISSN 0026-4679, Vol. 439, p. 46-52Article in journal (Refereed)
    Abstract [en]

    Elimination of antimony and arsenic impurities is one of the major difficulties encountered in copper metallurgy. This is because the pure copper ore reserves are becoming exhausted and the resources of unexploited ores often contain relatively high amounts of antimony and arsenic. During smelting of copper concentrates, arsenic is easily removed into the offgas while antimony is not readily removed due to its lower partial pressure and high affinity for liquid copper. It is however imperative to selectively eliminate and recover the antimony impurity of the copper concentrates in an environmentally friendly process with a view of upgrading the concentrates for pyrometallurgical processing.This communication discusses (i) alkaline sulphide hydrometallurgy of antimony removal from a complex copper concentrate; and (ii) antimony recovery as a marketable product from synthetic alkaline sulphide pregnant leach liquors by electrowinning in a nondiaphragm cell. Also, the various experimental parameters that influence these processes are discussed.

  • 206.
    Awe, Samuel Ayowole
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Upgrading of an impure copper concentrate for pyrometallurgical processing2011In: Proceedings, European Metallurgical Conference EMC 2011: Copper/ General Pyrometallurgy/ Vessel Integrity/ Process Gas Treatment, Dusseldorf, Germany: GDMB , 2011, Vol. 1, p. 15-31Conference paper (Refereed)
    Abstract [en]

    Copper ore grades are diminishing worldwide as the higher grade reserves are exploited and pro-gressively depleted. Simultaneously, the global demand for copper is increasing continuously. Con-sequently, processing of future copper ores and concentrates will most likely involve the treatment of more complex, fine-grained minerals containing increased levels of impurity elements (e.g. Sb, As and Hg), which are detrimental to the smelting process as well as affecting the physical and me-chanical properties of the copper product. Unfortunately, the prevalence of antimony containing minerals among the copper-bearing ores will reduce their economic value, and therefore, need to be eliminated. However, it is beneficial if antimony can be removed at the early stage of the process as a saleable product instead of ending-up as a waste material in copper metallurgy. This article aims at pre-treating a tetrahedrite-rich copper concentrate by selective dissolution of antimony in alkaline sulphide media, thereby, upgrading the concentrate for smelting operation. Furthermore, the kinetic mechanisms of the leach process as well as the factors affecting it were investigated. The selectivity of the lixiviant towards antimony is also discussed. The results show that the extraction of antimony from the concentrate depends strongly on the concentration of sul-phide and hydroxide ions, reaction temperature, particle size and the leaching time. Kinetic data from the study indicates that tetrahedrite dissolution from the concentrate under selected conditions is chemically controlled through the particle surface reaction with an estimated activation energy of 81 kJ/mol. Analysis of the leach residue proves that the lixiviant is selective and effective to solubi-lize this impurity element from the concentrate with high recovery. The impurity content of the concentrate was found to have reduced to low levels acceptable for smelting operation, and there-fore, lessen the processing problems faced during pyrometallurgical treatment of such impure copper concentrate.

  • 207.
    Awe, Samuel Ayowole
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sundkvist, Jan-Eric
    Boliden Mineral AB.
    Bolin, Nils-Johan
    Boliden Mineral AB.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Process flowsheet development for recovering antimony from Sb-bearing copper concentrates2013In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 49, p. 45-53Article in journal (Refereed)
    Abstract [en]

    The technical feasibility, on laboratory scale, of hydro- and electrometallurgical processes of recovering metallic antimony from an antimony-bearing copper sulphide concentrate has been investigated. The influence of Na2S concentration, temperature and solid concentration was studied during the leaching test while the effect of current density, Na2S concentration, electrolyte temperature and NaOH concentration on antimony electrowinning from alkaline sulphide solutions was investigated. The leaching results showed that antimony dissolution is strongly dependent on the concentration of the leaching reagent as well as the leaching temperature. The antimony content in the concentrate was reduced from 1.7% to less than 0.1% Sb which is desirable for copper metallurgy. Cathode current efficiency is one of the important parameters to evaluate the performance of an electrolytic process. It is revealed in this study that current efficiency of antimony deposition from sulphide electrolytes is highly dependent on the concentration of sodium hydroxide and the current density used. The results illustrate that the combined effect of increasing anode current density (which was 10 times higher than the cathode current density) and NaOH concentration enhanced the current efficiency of the electrolytic process. It was demonstrated that excess free sulphide ions impacts the current efficiency of the process detrimentally. An integrated hydro-/electrometallurgical process flowsheet for antimony removal and recovery from a sulphide copper concentrate was developed.

  • 208.
    Awe, Samuel Ayowole
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sundkvist, Jan-Eric
    Boliden Mineral AB.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Formation of sulphur oxyanions and their influence on antimony electrowinning from sulphide electrolytes2013In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 53, p. 39-47Article in journal (Refereed)
    Abstract [en]

    Antimony electrowinning from synthetic alkaline sulphide electrolytes has been studied in a nondiaphragm electrolytic cell. The electrodes were constructed in such a way that the anode produces ten times higher current density than the cathodic current density to promote sulphide oxidation to sulphate at the anode; and simultaneously decreasing the tendency of hydrogen evolution at the cathode. The result revealed that at an anodic current density lower than 1500 A/m2, minute amounts of sulphate ions were formed but when the anode current density increased beyond 1500 A/m2, sulphate formation was promoted. The initial molar concentration ratio between hydroxide and free sulphide ions should be ≥ 10.3 to avoid thiosulphate formation at 2000 A/m2 anodic current density under the conditions used in these experiments. The highest anodic current efficiency obtained based on the amount of sulphate formed was 89%. An increase in the anode current density as well as NaOH concentration enhances the cathodic and anodic current efficiencies with respect to the antimony metal deposited and sulphate ions produced, respectively. Despite the high anodic current densities used, the specific energy of this process ranges from 0.6 to 2.3 kWh/kg which is significantly lower than values reported previously due to the prevention of undesirable sulphur species from being formed. The tests revealed that the concentration of thiosulphate formed during the electrolysis decreased with increasing anode current density and NaOH concentration. Addition of polysulphide from 0 to 30 g/L to the electrolyte decreases the current efficiency from 83% to 32% and correspondingly increases the specific energy from 1.7 to 4.8 kWh/kg. Results showed that a build-up of sulphite and sulphate ions in the solution does not have any detrimental effect on the current efficiency of antimony deposition.

  • 209.
    Axelsson, Hans
    et al.
    Alfa Laval Separation AB.
    Westberg, Törbjörn
    Alfa Laval Separation AB.
    Wiese, Karin
    Luleå tekniska universitet.
    Våtklassering med centrifug vid höga koncentrationer1995In: Konferens i mineralteknik: Luleå, 14-16 februari 1995 / [ed] Marianne Thomaeus; Eric Forssberg, MinFo , 1995, p. 213-223Conference paper (Other academic)
  • 210.
    Aycik, G.A.
    et al.
    Turkish Atomic Energy Authority, Ankara Nuclear Research and Training Center.
    Paul, M.
    Turkish Atomic Energy Authority, Ankara Nuclear Research and Training Center.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Paul, Jan
    Leaching of radioactive isotopes from ash2003Conference paper (Other academic)
    Abstract [en]

    The aim of the study is to reduce the environmental impact of ash deposits. Ash from coal and biomass combustion, containing uranium and thorium from Yatagan-Silopi and Tuncbilek coal; cesium-137 from forests in northeastern Turkey and central Sweden. Turkey is dependent on coal for power generation and huge volumes of ash (>15 Mton/yr) are produced every year. Because of that certain coals, in particular Yatagan, with known problems from Mo and U leaching to the ground water, and Silopi oil shales/asphaltites were studied. Biomass ash comes from branches, bark and other unused parts of the trees and plants. This ash has low concentration of environmentally hazardous metals, but {sup 137}Cs is a problem in certain regions and it is of interest to investigate the possibilities to leach this metal from the ash. Washing ash through rapid chemical leaching at low pH reduces the slow release of metals from ash due to precipitation and besides it may lead to metal recovery from the ash. Initial experiments were done in batch form, in which the neutralizing capacity at pH 1-1.5 was measured by adding sulfuric acid to maintain pH for mixtures of ash and water. Subsequent experiments were done in bench scale. The process also reduced the metal content of the ash, due to chemical leaching of metal oxides and ion exchange at the surfaces of stable oxides. This means that treated ash will not release further metals and, eventually, relaxes the requirements on depositories and allows the ash from coal to be used as an admixture in cement, and to be used as a fertilizer following after treatment of ash from biomass

  • 211.
    Ayedh, H. M.
    et al.
    Norway.
    Nipoti, R.
    Italy.
    Hallén, Anders
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics, Integrated devices and circuits.
    Svensson, B. G.
    Norway.
    Kinetics modeling of the carbon vacancy thermal equilibration in 4H-SiC2018In: International Conference on Silicon Carbide and Related Materials, ICSCRM 2017, Trans Tech Publications, 2018, p. 233-236Conference paper (Refereed)
    Abstract [en]

    The carbon vacancy (VC) is a major limiting-defect of minority carrier lifetime in n-type 4H-SiC epitaxial layers and it is readily formed during high temperature processing. In this study, a kinetics model is put forward to address the thermodynamic equilibration of VC, elucidating the possible atomistic mechanisms that control the VC equilibration under C-rich conditions. Frenkel pair generation, injection of carbon interstitials (Ci’s) from the C-rich surface, followed by recombination with VC’s, and diffusion of VC’s towards the surface appear to be the major mechanisms involved. The modelling results show a close agreement with experimental deep-level transient spectroscopy (DLTS) depth profiles of VC after annealing at different temperatures.

  • 212.
    Aytekin, Kasim
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Characterization of machinability in lead-free brass alloys2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Recent legislation has put focus on the toxic nature of lead as an alloying element in brass products. Watersupply systems are of biggest concern where suspected lead leakages from brass products are threatening human health.

    A comprehensive study has been conducted in order to characterize the machinability of lead-free brass alloys to provide the industry with necessary information to assist a replacement of the leaded alternatives. The characterization has focused on two particular machining processes, namely turning and drilling and has been based on cutting force generation and chip formation. While the turning tests aimed to characterize the machinability by comparing two lead-free alloys (CW511L and AquaNordic®) with a leaded alloy (CW625N), drilling tests aimed to characterize machinability of the lead-free AquaNordic® alloy particularly, with the main focus put on the impact of tool geometry on machinability.

    The results have shown that significantly higher cutting forces are generated during turning of lead-free alloys as compared to the leaded. There was, however, no significant difference between the two lead-free alloys regarding cutting forces while chip formation is improved for AquaNordic®. Drilling tests have shown that the machinability of the lead-free AquaNordic® alloy can be improved by increasing the tool rake angle and decreasing tool diameter.

    Based on the results from this thesis work, it has been concluded that the machinability of lead-free brass alloys is sufficiently good to be able to be adopted by the industry. However, improvement is necessary inorder to fulfill the requirement needed to replace the leaded alternatives.

  • 213.
    Ayyala, Sekhar
    Luleå tekniska universitet.
    Influence of hydrodynamics on hydrophobic flocculation of galena1995Licentiate thesis, monograph (Other academic)
  • 214.
    Ayyala, Sekhar
    et al.
    Luleå University of Technology.
    Pugh, R.J.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Aggregate characteristics in coagulation and flocculation1995In: Mineral Processing and Extractive Metallurgy Review, ISSN 0882-7508, E-ISSN 1547-7401, Vol. 12, no 2-4, p. 165-165Article in journal (Refereed)
  • 215.
    Ayyala, Sekhar
    et al.
    Luleå University of Technology.
    Subrahmanyam, T.V.
    Departmento de Geologia, CCE/UFRN, Campus Universitario, Natal.
    Pugh, R.J.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Effect of corrosion inhibitors on grinding and flotation of a lead-zinc ore1993In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 6, no 8, p. 929-935Article in journal (Refereed)
    Abstract [en]

    Grinding and flotation experiments on a Pb-Zn ore were carried out to evaluate: 1) wear of the grinding media both in the presence and absence of an inhibitor and 2) effect of the inhibitor on the flotation of Pb---Zn minerals. The percentage reduction in the wear of the grinding media was observed to be between 25–36%, depending on the type of the inhibitor and its critical concentration. The inhibitors used in the investigation were sodium sulphite, sodium nitrite, sodium chromate and sodium silicate. The results indicate that a specific corrosion inhibitor, for example sodium sulphite, may give better recoveries and grades in flotation but is not as efficient as sodium chromate in inhibiting the wear of the grinding media. Pulp solutions (after grinding) analysed for metal ion concentrations showed low Fe. Iron released into the solution as a result of corrosion reactions subsequently forms insoluble hydroxy complexes and may coat the mineral surfaces. Such hydrophilic coatings may adversely affect the floatabilities of minerals. The particle size analysis of the ground product has been carried out and the results are discussed.

  • 216.
    Aziziderouei, Mona
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    The influence of Strontium level on the microstructure formations and mechanical properties of Al-Si alloys2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Abstract

    The aim of this thesis is to investigate the influence of Strontium (Sr) addition on the microstructure formation, including porosity and the mechanical properties of commercial Aluminum alloy ENAC 46000. In addition, it is intended to obtain an optimum Sr level in order to achieve the desired mechanical properties.

    Specimens were prepared with gradient solidification technique at different cooling rates in order to achieve samples with a variety of microstructural coarseness. Beside microstructural and mechanical properties studies, thermal analysis was employed to keep track of the time and temperature of phases during solidification.

    The achieved results indicate that Sr affects the mechanical properties except the strength. The analysis of the result indicates that the optimum level of Sr is 150 ppm.

    Porosity is a function of both Sr addition and cooling rate. Comparing the influence of cooling rate with Sr addition on the amount of porosity shows that the cooling rate can modify the ENAC 46000 alloy more than Sr addition.

    Thermal analysis technique used to study effect of phase formation on modification. Influence of solidification rate and Sr level on time and temperature of α-Al (Τ_α) and Al-Si eutectic (Τ_N) nucleation was observed.

  • 217.
    Babu, Prasath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Indian Institute of Science, Bangalore, India.
    Vamsi, K. V.
    Karthikeyan, S.
    On the formation and stability of precipitate phases in a near lamellar γ-TiAl based alloy during creep2018In: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 98, p. 115-125Article in journal (Refereed)
    Abstract [en]

    The formation, evolution and stability of metastable phases observed in the γ-TiAl based alloy Ti-47Al-2Cr-2Nb was studied under creep deformation with stress applied at two different hard orientations in a highly textured as-cast + HIPed material. Previously we have reported that the metastable phase Ti(Al,Cr)2 with C14 Laves phase structure forms at the γ-α2 interface which acts as sink for the alloying elements ejected from the dissolving α2 phase and also expected to effectively control the interface stresses through short range diffusion and modifications in the chemical composition [1]. Ab initio density functional theory based calculations were carried out to evaluate the effect of choice of lattice position and site occupancy of aluminium atoms in the Ti(Al,Cr)2 structure on the lattice parameter variation and thermodynamic stability. C14 with the composition 25 at. % Al was found to have lattice parameter values close to the inter-planar spacing of <110>γ and <10-10>α2 which would have a lower misfit with C14 across the interface. From the cohesive energy calculations, Laves phase C14 with a constrained lattice parameter due to the adjoining phases, exhibits higher stability than the B2 and L10 structures across a range of compositions studied. Electron diffraction simulations of C14 with a composition of 25% Al compared with the experimental data suggest that the structure C14 has taken up either a random site occupancy compared to a specific choice of ordering to minimize the interfacial stress. Though the experimental evidences do not strongly support a long-range ordering theory in C14, short-range ordering could be a tangible choice for alleviating interface misfits. The ability of C14 to assume different lattice parameters at and far from the α2-γ interface also suggest that the C14 acts as buffer layer between α2 and γ phases in the presence of local stresses, although this is not the thermodynamically expected phase at the temperature of creep experiment.

  • 218.
    Bahbou, M. Fouzi
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    A study of the adhesion strength of plasma sprayed coatings2007Doctoral thesis, comprehensive summary (Other academic)
  • 219.
    Bahbou, M. Fouzi
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Choquet, Isabelle
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Clement, Uta
    Numerical and experimental study of Ni-particle impact on a ti-surfaceIn: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016Article in journal (Refereed)
  • 220.
    Bahbou, M. Fouzi
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Choquet, Isabelle
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Numerical and Experimental Study of Ni-Particle Impact On A Ti-Surface2007In: Proceedings of the International Thermal Spray Conference: May 2007, Beijing, China, ASM International , 2007, p. 219-224Conference paper (Refereed)
  • 221.
    Bahrami, Ataallah
    et al.
    Department of Mining Engineering, Urmia University, Urmia, Iran.
    Ghorbani, Yousef
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Hosseini, Mohammad Raouf
    Department of Mining Engineering, Isfahan University of Technology, Isfahan, Iran.
    Kazemi, Fatemeh
    Department of Mining Engineering, Urmia University, Urmia, Iran.
    Abdollahi, Morteza
    Department of Mining Engineering, Urmia University, Urmia, Iran.
    Danesh, Abolfazl
    Mineral Processing Plant, Sungun Mine, Tabriz, Iran.
    Combined Effect of Operating Parameters on Separation Efficiency and Kinetics of Copper Flotation2019In: Mining, metallurgy & exploration, ISSN 2524-3462, Vol. 36, no 2, p. 409-421Article in journal (Refereed)
    Abstract [en]

    This study aims to investigate the effects of operational variables on concentrate grade, recovery, separation efficiency, and kinetic parameters of the copper flotation process. For this purpose, the effects of the pulp solids content, collector and frother dosage, and preparation and concentrate collection time were studied using a Taguchi experimental design. The results of statistical analyses indicated that the concentrate collection time and pulp density were the most influential parameters on concentrate grade. Considering copper recovery, concentrate collection time, collector dosage, and pulp density were the most significant variables, in decreasing order of importance. Also, the separation efficiency was mostly influenced by the concentrate collection time. Furthermore, kinetic studies showed that the second-order rectangular distribution model perfectly matched the experimental flotation data. The highest kinetic constant of 0.0756 s−1 was obtained from the test, which was performed with 35% solids content and 40 and 20 g/t collector and frother, respectively. The highest predicted copper recovery of 99.57% was obtained from the test at 30% solids content, and the collector and frother dosages of 40 and 15 g/t, respectively.

  • 222.
    Bahrami, Ataallah
    et al.
    Department of Mining EngineeringUrmia UniversityUrmiaIran.
    Ghorbani, Yousef
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Mirmohammadi, Mirsaleh
    School of Mining EngineeringUniversity of TehranTehranIran.
    Sheykhi, Behnam
    Department of Mining EngineeringUrmia UniversityUrmiaIran.
    Kazemi, Fatemeh
    Department of Mining EngineeringUrmia UniversityUrmiaIran.
    The beneficiation of tailing of coal preparation plant by heavy-medium cyclone2018In: International journal of coal science & technology, ISSN 2095-8293, Vol. 5, no 3, p. 374-384Article in journal (Refereed)
    Abstract [en]

    Dense-medium cyclones have been used for beneficiation of fine particles of coal. In this study, the usability of cyclones in the beneficiation of tailings of a coal preparation plant was investigated. For this purpose, separation tests were conducted using spiral concentrator and heavy medium cyclones with the specific weight of medium 1.3–1.8 (g/cm3) on different grading fractions of tailing in an industrial scale (the weight of tail sample was five tons). Spiral concentrator was utilized to beneficiate particles smaller than 1 mm. In order to evaluate the efficiency of cyclones, sink and float experiments using a specific weight of 1.3, 1.5, 1.7 and 1.9 g/cm3, were conducted on a pilot scale. Based on the obtained results, the recovery of floated materials in cyclones with the specific weight of 1.40, 1.47 and 1.55 g/cm3 are 17.75%, 33.80%, and 50%, respectively. Also, the cut point (ρ50), which is the relative density at which particles report equally to the both products are 1.40, 1.67 and 1.86 g/cm3. The probable errors of separation for defined specific weights for cyclones are 0.080, 0.085 and 0.030, respectively. Also, the coefficients of variation was calculated to be 0.20, 0.12 and 0.03. Finally, it could be said that the performance of a cyclone with a heavy medium of 1.40 g/cm3 specific weight is desirable compared with other specific weights.

  • 223.
    Bahrami, Ataallah
    et al.
    Urmia University, Iran .
    Ghorbani, Yousef
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Sharif, Jafar Abdollahi
    Urmia University, Iran .
    Kazemi, Fatemeh
    Urmia University, Iran .
    Abdollahi, Morteza
    Urmia University, Iran .
    Salahshur, Abbas
    Urmia University, Iran .
    Danesh, Abolfazl
    Urmia University, Iran .
    A geometallurgical study of flotation performance in supergene and hypogene zones of Sungun copper deposit2019In: Mineral Processing and Extractive Metallurgy, ISSN 2572-6641Article in journal (Refereed)
    Abstract [en]

    The feed of mineral processing plants, usually consist of different minerals from various geological zones, which show different behavior in separation processes. In this research, samples from supergene and hypogene zones were provided to investigate the flotation behavior of copper minerals. Flotation experiments were carried out in three phases of supergene sample, hypogene sample and mixed samples. Based on the results, the recovery rate of the mixed sample was 83.61%, which is 7.63% and 1.79% higher than the recovery of the samples of hypogene and supergene zones, respectively. The concentrate grade values obtained for blended, hypogene zone and supergene zone are 10.32%, 2.81% and 12.37%, respectively. The maximum values of flotation constant and infinite recovery are 0.956 (s−1) and 88.833% for the mixed sample. It was also concluded that the highest amount of k and infinitive recovery were related to supergene zone sulfide flotation which are 0.831 (s−1) and 84.33% respectively.

  • 224.
    Bahrami, Ataallah
    et al.
    Department of Mining Engineering, Faculty of Engineering, Urmia University, Urmia, Iran.
    Kazemi, Fatemeh
    PhD Student of mineral processing, Faculty of Engineering, University of Kashan, Kashan, Iran.
    Ghorbani, Yousef
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Effect of different reagent regime on the kinetic model and recovery in gilsonite flotation2019In: Journal of Materials Research and Technology, ISSN 2238-7854Article in journal (Refereed)
    Abstract [en]

    Gilsonite is a natural fossil resource, similar to an oil asphalt high in asphaltenes. To determine the effect of reagent regime on the kinetic order and rate of flotation for a gilsonite sample, experiments were carried out in both rougher and cleaner flotation process. Experiments were conducted using different combinations of reagent: oil – MIBC; gasoline – pine oil; and one test without any collector and frother. According to results, kinetic in the test performed using the oil – MIBC and without any collector and frother were found to be first-order unlike the kinetic in the test conducted using the gasoline – pine oil. Five kinetic models were applied to the modeling of data from the flotation tests by using MATrix LABoratory software. The results show that all experiments are highly in compliance with all models. The kinetic constants (k) in rougher stage were calculated as 0.1548 (s−1), 0.2300 (s−1) and 0.2163 (s−1) for oil – MIBC, gasoline – pine oil, and test without any collector and frother, respectively. These amounts in the cleaner stage were 0.0450 (s−1), 0.1589 (s−1) and 0.0284 (s−1), respectively. The relationship between k, maximum combustible recovery (R∞" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; display: inline-block; line-height: normal; font-size: 16.2px; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;">R∞) and particle size was also studied. The results showed that the R∞" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; display: inline-block; line-height: normal; font-size: 16.2px; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;">R∞ and k were obtained with a coarse particle size of (−250 + 106) μm in the rougher and (−850 + 500) μm in cleaner flotation processes.

  • 225.
    Bahrami, Ataallah
    et al.
    Department of Mining Engineering, Urmia University, Urmia, Iran.
    Kazemi, Fatemeh
    University of Kashan, Kashan, Iran.
    Ghorbani, Yousef
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    The Order of Kinetic Models, Rate Constant Distribution, and Maximum Combustible Recovery in Gilsonite Flotation2019In: Mining, Metallurgy & Exploration, ISSN 2524-3462Article in journal (Refereed)
    Abstract [en]

    Kinetic models are the most important tool for predicting and evaluating the performance of flotation circuits. Gilsonite is a natural fossil resource similar to an oil asphalt, high in asphaltenes. Here, in order to determine the kinetic order and flotation rate of a gilsonite sample, flotation experiments were carried out in both rougher and cleaner stages. Experiments were conducted using the combinations of oil–MIBC and gas oil–pine oil, with one test without collector and frother. Five kinetic models were applied to the data obtained from the flotation tests using MATLAB software. Statistical analysis showed that the results of the experiment with oil–MIBC were highly in compliance with all models. Kinetic constants (k) were calculated as 0.1548 (s−1) and 0.0450 (s−1) for rougher and cleaner stages, respectively. Rougher and cleaner tests without collector and frother also matched all models well (R2 > 0.98), with kvalues of 0.2163 (s−1) and 0.284 (s−1), respectively. The relationship between flotation rate constant, maximum combustible recovery, and particle size showed that the maximum flotation combustible recovery and flotation rate were obtained in the size range of −250 + 106 μm in the rougher and cleaner stages. The combustible recovery and flotation rate were higher in the rougher flotation process than in the cleaner stage.

  • 226.
    Bahrami, Ataallah
    et al.
    Department of Mining Engineering, Urmia University, Urmia, Iran.
    Mirmohammadi, Mirsaleh
    School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran.
    Ghorbani, Yousef
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Kazemi, Fatemeh
    Department of Mining Engineering, Urmia University, Urmia, Iran.
    Abdollahi, Morteza
    Department of Mining Engineering, Urmia University, Urmia, Iran.
    Danesh, Abolfazl
    Complex of Copper Processing-Sungun, East Azerbaijan Province, Tabriz, Iran.
    Process mineralogy as a key factor affecting the flotation kinetics of copper sulfide minerals2019In: International Journal of Minerals, Metallurgy and Materials, ISSN 1674-4799, E-ISSN 1869-103X, Vol. 26, no 4, p. 430-439Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to apply process mineralogy as a practical tool for further understanding and predicting the flotation kinetics of the copper sulfide minerals. The minerals’ composition and association, grain distribution, and liberation within the ore samples were analyzed in the feed, concentrate, and the tailings of the flotation processes with two pulp densities of 25wt% and 30wt%. The major copper-bearing minerals identified by microscopic analysis of the concentrate samples included chalcopyrite (56.2wt%), chalcocite (29.1wt%), covellite (6.4wt%), and bornite (4.7wt%). Pyrite was the main sulfide gangue mineral (3.6wt%) in the concentrates. A 95% degree of liberation with d80 > 80 µm was obtained for chalcopyrite as the main copper mineral in the ore sample. The recovery rate and the grade in the concentrates were enhanced with increasing chalcopyrite particle size. Chalcopyrite particles with a d80 of approximately 100 µm were recovered at the early stages of the flotation process. The kinetic studies showed that the kinetic second-order rectangular distribution model perfectly fit the flotation test data. Characterization of the kinetic parameters indicated that the optimum granulation distribution range for achieving a maximum flotation rate for chalcopyrite particles was between the sizes 50 and 55 µm.

  • 227.
    Bai, Haitong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A Study of the Swirling Flow Pattern when Using TurboSwirl in the Casting Process2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The use of a swirling flow can provide a more uniform velocity distribution and a calmer filling condition according to previous studies of both ingot and continuous casting processes of steel. However, the existing swirling flow generation methods developed in last decades all have some limitations. Recently, a new swirling flow generator, the TurboSwirl device, was proposed. In this work, the convergent nozzle was studied with different angles. The maximum wall shear stress can be reduced by changing the convergent angle between 40º and 60º to obtain a higher swirl intensity. Also, a lower maximum axial velocity can be obtained with a smaller convergent angle. Furthermore, the maximum axial velocity and wall shear stress can also be affected by moving the location of the vertical runner. A water model experiment was carried out to verify the simulation results of the effect of the convergent angle on the swirling flow pattern. The shape of the air-core vortex in the water model experiment could only be accurately simulated by using the Reynolds Stress Model (RSM). The simulation results were also validated by the measured radial velocity in the vertical runner by the ultrasonic velocity profiler (UVP). The TurboSwirl was reversed and connected to a traditional SEN to generate the swirling flow. The periodic characteristic of the swirling flow and asymmetry flow pattern were observed in both the simulated and measured results. The detached eddy simulation (DES) turbulence model was used to catch the time-dependent flow pattern and the predicted results agree well with measured axial and tangential velocities. This new design of the SEN with the reverse TurboSwirl could provide an almost equivalent strength of the swirling flow generated by an electromagnetic swirling flow generator. It can also reduce the downward axial velocities in the center of the SEN outlet and obtain a calmer meniscus and internal flow in the mold.

  • 228.
    Bai, Haitong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Par
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Effect of TurboSwirl Structure on an Uphill Teeming Ingot Casting Process2015In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, no 6, p. 2652-2665Article in journal (Refereed)
    Abstract [en]

    To produce high-quality ingot cast steel with a better surface quality, it would be beneficial for the uphill teeming process if a much more stable flow pattern could be achieved in the runners. Several techniques have been utilized in the industry to try to obtain a stable flow of liquid steel, such as a swirling flow. Some research has indicated that a swirl blade inserted in the horizontal and vertical runners, or some other additional devices and physics could generate a swirling flow in order to give a lower hump height, avoid mold flux entrapment, and improve the quality of the ingot products, and a new swirling flow generation component, TurboSwirl, was introduced to improve the flow pattern. It has recently been demonstrated that the TurboSwirl method can effectively reduce the risk of mold flux entrapment, lower the maximum wall shear stress, and decrease velocity fluctuations. The TurboSwirl is built at the elbow of the runners as a connection between the horizontal and vertical runners. It is located near the mold and it generates a tangential flow that can be used with a divergent nozzle in order to decrease the axial velocity of the vertical flow into the mold. This stabilizes flow before the fluid enters the mold. However, high wall shear stresses develop at the walls due to the fierce rotation in the TurboSwirl. In order to achieve a calmer flow and to protect the refractory wall, some structural improvements have been made. It was found that by changing the flaring angle of the divergent nozzle, it was possible to lower the axial velocity and wall shear stress. Moreover, when the vertical runner and the divergent nozzle were not placed at the center of the TurboSwirl, quite different flow patterns could be obtained to meet to different requirements. In addition, the swirl numbers of all the cases mentioned above were calculated to ensure that the swirling flow was strong enough to generate a swirling flow of the liquid steel in the TurboSwirl.

  • 229.
    Bai, Haitong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    An Experimental and Numerical Study of Swirling Flow Generated by TurboSwirl in an Uphill Teeming Ingot Casting Process2016In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 56, no 8, p. 1404-1412Article in journal (Refereed)
    Abstract [en]

    A swirling flow has been demonstrated to be beneficial for making the flow pattern even and to reduce turbulence during filling in ingot casting. A new swirling flow generation device, TurboSwirl, was applied to improve the flow pattern of the liquid steel as it flows into the mold so that a more stable flow could be obtained. A water model was built including the TurboSwirl with different flaring angles of the divergent nozzle, according to a former numerical study indicating that a much more beneficial flow pattern could be obtained by reducing the flaring angle. To validate the mathematical model, the air-core vortex formed in the water model experiment was used, and the length of the vortex was measured and compared to the numerical predictions. Different turbulence models including the standard k-epsilon, realizable k-epsilon and Reynolds stress model were tested. It was found that only the Reynolds stress model could most accurately simulate the high swirling flow including a vortex. In addition, the radial velocity of the water around the vortex was measured by an ultrasonic velocity profiler (UVP). The experimental results revealed a high turbulence of the swirling flow and strong fluctuations of the vortex. The radial velocity of the water around the upper part of the vortex could be predicted well compared to the experimental results by the UVP measurements.

  • 230.
    Bai, Haitong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Experimental Validation and Numerical Analysis of the Swirling Flow in a Submerged Entry Nozzle and Mold by using a Reverse TurboSwirl in a Billet Continuous Casting Process2016In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344XArticle in journal (Refereed)
    Abstract [en]

    As an alternative to some traditional methods to generate a swirling flow in the continuous casting process, the use of a new swirling flow generator, TurboSwirl, was studied. Specifically, a reversed TurboSwirl device was designed as part of a submerged entry nozzle (SEN) for a round billet continuous casting process. Mathematical modelling was used to investigate this new design and a water model experiment was carried out to validate the mathematical model. The predicted velocities by the turbulence models: realizable k-ε model, Reynold stress model (RSM) and detached eddy simulation (DES) were compared to the measured results from an ultrasound velocity profile (UVP) method. The DES model could give the best prediction inside the SEN and had a deviation less than 3.1% compared to the measured results. Moreover, based on the validated mathematical model and the new design of the SEN, the effect of the swirling flow generated by the reverse TurboSwirl on the flow field of the SEN and mold was compared to the design of the electromagnetic swirl flow generator (EMSFG). A very strong swirling flow in the SEN and a stable flow pattern in the mold could be obtained by the reverse TurboSwirl compared to the EMSFG. 

  • 231.
    Bai, Haitong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Numerical Study of the Application for the Divergent Reverse TurboSwirl Nozzle in the Billet Continuous Casting ProcessManuscript (preprint) (Other academic)
    Abstract [en]

    The swirling flow is demanded from the submerged entry nozzle (SEN) to the mold for the continuous casting process. A new design of the SEN is applied by using the reverse TurboSwirl. The TurboSwirl has been proved that it can provide a more stable flow pattern of the liquid steel in the mold. It also can supply a strong enough swirling flow compared to other swirling flow generation methods. Furthermore, a divergent nozzle is added to replace the bottom part of the straight SEN. This new divergent reverse TurboSwirl nozzle (DRTSN) could gain a more beneficial flow pattern in the mold compared to the straight nozzle. The numerical results reveals that a stronger swirling flow can be gained at the SEN outlet with a calmer flow field and active meniscus flow. It is also found that the swirl intensity in the SEN is independent of the casting speed. Lower casting speed is more desired due to a lower maximum wall shear stress. The DRTSN is connected to the tundish by an elbow and a horizontal runner. Longer horizontal runner can supply a more uniform velocity profile and symmetrical flow pattern in the mold. 

  • 232. Bai, Q.
    et al.
    Guo, Z.
    Cui, X.
    Yang, X.
    Yanhua, L.
    Jin, L.
    Sun, Y.
    Experimental investigation on the solidification rate of water in open-cell metal foam with copper fins2018In: Energy Procedia, Elsevier Ltd , 2018, p. 210-214Conference paper (Refereed)
    Abstract [en]

    This study focused on the effect of inserting fins into metal foam on the solidification rate. To this aim, a well-designed experimental system with solid-liquid interface visualization was built. Metal foam samples with different fin intervals were prepared for experiments. Solidification process of water saturating in finned metal foam under bottom cooling was experimentally investigated. Results showed that inserting fins into metal foam can make a promotional improvement on solidification rate of water. The solid-liquid interface became curved after inserting fins, compared with metal foam sample without fins. Besides, changing the interval has little effect on the solidification rate. 

  • 233. Bai, Q.
    et al.
    Guo, Z.
    Li, H.
    Yang, Xiaohu
    KTH, School of Chemical Science and Engineering (CHE).
    Jin, L.
    Yan, Jerry
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Energy Processes.
    Experimental investigation on the solidification behavior of phase change materials in open-cell metal foams2017In: Energy Procedia, Elsevier Ltd , 2017, Vol. 142, p. 3703-3708Conference paper (Refereed)
    Abstract [en]

    This study presented an experimental investigation on solidification behavior of fluid saturated in highly porous open-cell copper foams. Particular attention has been made on the effect of pore parameters (pore density and porosity) on the solidification behavior. A purposely-designed apparatus was built for experimental observations. Results showed that the copper foam had a great effect on solidification and the full solidification time can be saved up to 50%, especially preventing the decrease in solidification rate during the later stage of phase change. The smaller the porosity is, the faster the solidification rate will be. Pore density was found to have little influence upon the solidification rate. In addition, the local natural convection does exist but it has a slight effect on solidification, leading to the slant of the solid-liquid interface.

  • 234.
    Balachandramurthi, Arun Ramanathan
    et al.
    Univ West, Sweden.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Univ West, Sweden.
    Dixit, Nikhil
    Univ West, Sweden.
    Deng, Dunyong
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Pederson, Robert
    Univ West, Sweden.
    Microstructural influence on fatigue crack propagation during high cycle fatigue testing of additively manufactured Alloy 7182019In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 149, p. 82-94Article in journal (Refereed)
    Abstract [en]

    A study of the microstructure of additively manufactured Alloy 718 was performed in order to better understand the parameters that have an influence on the fatigue properties of the material. The specimens were manufactured using two powder bed fusion techniques - Electron Beam Melting (EBM) and Selective Laser Melting (SLM). Four point bending fatigue tests were performed at room temperature with a stress ratio of R = 0.1 and 20 Hz frequency, on material that was either in hot isostatically pressed (HIP) and solution treated and aged (STA) condition or in STA condition without a prior HIP treatment. The grains in the SLM material in the HIP + STA condition have grown considerably both in the hatch and the contour regions; EBM material, in contrast, shows grain growth only in the contour region. Fractographic analysis of the specimens in HIP + STA condition showed a faceted appearance while the specimens in STA condition showed a more planar crack appearance. The crack propagation occurred in a transgranular mode and it was found that precipitates such as NbC, TiN or 8-phase, when present, did not affect the crack path. The areas with larger grains corresponded to the faceted appearance of the fracture surface. This could be attributed to the plastic zone ahead of the crack tip being confined within one grain, in case of the larger grains, which promotes single shear crack growth mode.

  • 235.
    Ballesteros, Antonio
    et al.
    JRC Petten, Holland.
    Hein, Hieronymus
    AREVA Gmbh Germany.
    May, Johannes
    AREVA Gmbh Germany.
    Planman, Tapio
    VTT Finland.
    Todeshini, Patrick
    EdF France.
    Brumowski, Milan
    UJV Czech Republic.
    Roudén, Jenny
    Gillemot, Ferenc
    MTA Hungary.
    Chaouadi, Rachid
    SCK-CEN, Belgium.
    Efsing, Pål
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Altstadt, Eberhard
    Forschung Center Rossendorff, Germany.
    Reactor Pressure vessel surveillance2014In: Nuclear Engineering International, ISSN 0029-5507, Vol. 59, no 12, p. 19-20Article in journal (Refereed)
    Abstract [en]

    This publication summarizes techniques suitable for surveillance program for the objective of  long term operation (LTO) on European NPPs and provides recommendations on reactor pressure vessel (RPV) irradiation surveillance based on the work preformed in the work package 7 "Surveillance guidelines" of the LONGLIFE international project. The LONGLIFE project "treatment of long term irradiation embrittlement effects in RPV safety assessment" was 50% funded by the Euratom 7th framework programme of the European commision. The project coordinated by the Helmholtz-centrum Dresden Rossendorf successfully finalized in 2014.

  • 236.
    Bamford, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Tool wear in turning of titanium alloy Ti–6Al–4V: Challenges and potential solutions for crater wear, diffusion and chip formation2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Titanium alloys are major materials used in the airplane industry, and prospects show that airplane production will double in the next 20 years. Consequently, the demand for cutting tools for machining of titanium alloys will increase. The primary problem when machining titanium alloys is their low thermal conductivity. Crater wear is the main factor limiting tool life, and is generally caused by thermal diffusion due to high temperatures in the tool-chip interface.

    This master’s thesis was performed in collaboration with Sandvik Coromant, with the prospect to increase knowledge of how diffusion and chip formation influences crater wear progression. The aim was to study tool wear of cutting tools when turning Ti–6Al–4V. This was done by testing two different rake face geometries, both coated and uncoated, at cutting speeds of 30–115 m/min. Diffusion was investigated to learn about the impact it has on crater wear. Chips were examined to investigate chip formation and shear strain.

    The coated modified rake face insert showed less crater wear only for the initial few seconds of machining. Uncoated inserts with a modified rake face showed higher diffusion rate and faster crater wear progression than did standard inserts. The standard inserts showed twice as long tool life as did the modified inserts. No significant differences in the chip formation mechanism were found between modified and standard inserts. Cracks were found within shear bands that were thinner than usual, which suggest that the generation of cracks allows less shear deformation.

  • 237.
    Banda, H.
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Der Einfluss von Trübedichte, Körnung und Filtrationsdruck auf den Durchflusswiderstand eines Filterkuchens1987In: Aufbereitungstechnik - Mineral processing, ISSN 0004-783X, Vol. 28, no 9, p. 513-520Article in journal (Refereed)
    Abstract [en]

    The effects of slurry concentration, filtration pressure and particle size distribution on the resistance of a filter cake are studied, and an attempt is made to examine the filtration process with reference to the structure of the filter cake. Micrographic analysis clearly demonstrates the effect of particles segregation on filtration rate. The resistance of the cake rises with increasing solids concentration of the slurry, mainly due to a lower degree of particle segregation.

  • 238.
    Banda, H.
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Porositätsvariationen bei auf horizontalen Flächen unter Druck geformten Filterkuchen1988In: Aufbereitungstechnik - Mineral processing, ISSN 0004-783X, Vol. 29, no 1, p. 1-7Article in journal (Refereed)
    Abstract [en]

    Direct measurement of the porosity variation in filter cakes by image analysis has been tested on chalcopyrite and magnetite slurries. It was found to give more accurate results than previous indirect methods, especially at the surface of the cake. Microscopy and image analysis visualize the effect of particle size, particle segregation and air bubbles on cake porosity. In a filter cake formed under constant pressure, the maximum porosity is shown to occur in regions inside the cake, rather than on the surface.

  • 239.
    Banda, H.
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Strukturanalyse eines Filterkuchens mit dem Bildanalysator1987In: Aufbereitungstechnik - Mineral processing, ISSN 0004-783X, Vol. 28, no 4, p. 175-180Article in journal (Refereed)
    Abstract [en]

    Two methods for the consolidation of filter cakes are developed; one of them is based on acrylate plastic as an impregnating medium, and the other uses epoxy resin and is suitable for sulfide-carrying materials, where the first one fails. Even cakes formed from fine particles ( less than 38 mu m) can be consolidated using these methods. Specimens prepared with acrylate offer no difficulties in grinding and polishing; those prepared with epoxy resin, however, call for procedures with bonded grinding media, and the sections are preferably examined under a scanning electron microscope. Direct comparison between the consolidation methods has not been made. Porosity and pore size distribution are measured in filter cakes formed from two different materials using a computerized image analyzer.

  • 240.
    Banda, S. M. Herath
    Luleå tekniska universitet.
    Studies in pressure filtration on upward facing surfaces from a structural point of view1987Doctoral thesis, comprehensive summary (Other academic)
  • 241.
    Banda, S.M. Herath
    Luleå tekniska universitet.
    Pressure filtration1986In: Workshop i mineralteknik: Luleå 11-12 februari 1986 / [ed] Börje Sköld; Eric Forssberg, MinFo , 1986, p. 45-61Conference paper (Other academic)
  • 242.
    Banda, S.M.Herath
    Luleå tekniska universitet.
    A fundamental study of cake filtration1986Licentiate thesis, comprehensive summary (Other academic)
  • 243.
    Banda, S.M.Herath
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Pressure filtration of a fine-grained chalcopyrite concentrate1988In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 17, no 2, p. 61-66Article in journal (Refereed)
    Abstract [en]

    How material properties, cake characteristics and operating parameters affect the filtration rate and the final moisture content was investigated by laboratory test with a concentrate from a complex sulfide ore. Porosity and pore size distribution were measured by automatic image analysis. With optimum conditions, a moisture content of 5. 5% was achieved. A copper/lead concentrate floated from a complex sulfide ore at the Stekenjokk concentrator of Boliden Mineral AB, Sweden was used.

  • 244.
    Banda, S.M.Herath
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Structure variation in filter cakes from flocculated slurries1988In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 17, no 2, p. 57-60Article in journal (Refereed)
    Abstract [en]

    To flocculate slimy material dispersed in water is a common operation in mineral processing either to recover the material or to clear the water. In laboratory tests with flocculated slurries, floc sizes, porosity and sizes of filter cakes were measured by automatic image analysis. An observed decrease in filtrate flow rate at flocculant overdosage was not caused by a smaller mean floc size but may have been due to an obstruction of the pore channels by adsorbed polymer threads. Samples of a copper/lead concentrate floated at the Stekenjokk concentrator of Boliden Mineral AB, Sweden, were used for this investigation.

  • 245.
    Banda, S.M.Herath
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Variation of filter cake permeability with mean pore diameter of the cake1998In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 17, no 2, p. 67-72Article in journal (Refereed)
    Abstract [en]

    It is shown that most particles in a filter cake have more than only point contact with each other. Therefore, the Kozeny-Carmen equation is modified by relating permeability to porosity and a mean pore diameter as measured by automatic image analysis in horizontal cross sections of the cake. In filter cakes of chalcopyrite and magnetite, the permeability increases stepwise with the product of porosity and square mean pore diameter.

  • 246.
    Bandyopadhyay, Robi
    University West, Department of Technology.
    Modelling of the flame spraying process2003Report (Other (popular science, discussion, etc.))
  • 247. Ban-Ya, S.
    et al.
    Hino, M.
    Hayashi, M.
    Sano, N.
    Fredriksson, Patrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Comments on "Evaluation of thermodynamic activity of metallic oxide in a ternary slag from the sulphide capacity of the slag"2005In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 45, no 11, p. 1754-1757Article in journal (Refereed)
  • 248.
    Barick, Prasenjit
    et al.
    International Advanced Research Centre for Powder Metallurgy and New Materials, Balapur Post, Hyderabad, 500005 Telangana, India.
    Chakravarty, Dibyendu
    International Advanced Research Centre for Powder Metallurgy and New Materials, Balapur Post, Hyderabad, 500005 Telangana, India.
    Saha, Bhaskar Prasad
    International Advanced Research Centre for Powder Metallurgy and New Materials, Balapur Post, Hyderabad, 500005 Telangana, India.
    Nitra, Rahul
    Department of Metallurgical and Materials Engineering, Indian Institute of Technology Kharagpur, Kharagpur, 721302 West Bengal, India.
    Joshi, Shrikant
    University West, Department of Engineering Science, Research Enviroment Production Technology West. International Advanced Research Centre for Powder Metallurgy and New Materials, Balapur Post, Hyderabad, 500005 Telangana, India.
    Effect of pressure and temperature on densification, microstructure and mechanical properties of spark plasma sintered silicon carbide processed with β-silicon carbide nanopowder and sintering additives2016In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 42, no 3, p. 3836-3848Article in journal (Refereed)
    Abstract [en]

    The effects of applied pressure and temperature during spark plasma sintering (SPS) of additive-containing nanocrystalline silicon carbide on its densification, microstructure, and mechanical properties have been investigated. Both relative density and grain size are found to increase with temperature. Furthermore, with increase in pressure at constant temperature, the relative density improves significantly, whereas the grain size decreases. Reasonably high relative density (~96%) is achieved on carrying out SPS at 1300 °C under applied pressure of 75 MPa for 5 min, with a maximum of ~97.7% at 1500 °C under 50 MPa for 5 min. TEM studies have shown the presence of an amorphous phase at grain boundaries and triple points, which confirms the formation of liquid phase during sintering and its significant contribution to densification of SiC at relatively lower temperatures (≤1400 °C). The relative density decreases on raising the SPS temperature beyond 1500 °C, probably due to pores caused by vaporization of the liquid phase. Whereas β-SiC is observed in the microstructures for SPS carried out at temperatures ≤1500 °C, α-SiC evolves and its volume fraction increases with further increase in SPS temperatures. Both hardness and Young׳s modulus increase with increase in relative density, whereas indentation fracture toughness appears to be higher in case of two-phase microstructure containing α and β-SiC.

  • 249.
    Bark, Glenn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Wanhainen, Christina
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Pålsson, Bertil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Textural setting of gold and its implications on mineral processing: preliminary results from three gold deposits in northern Sweden2013In: Mineral deposit research for a high-tech world: Proceedings of the 12th Biennial SGA Meeting, 12–15 August 2013, Uppsala, Sweden, Uppsala: Sveriges Geologiska Undersökning , 2013, p. 302-305Conference paper (Refereed)
    Abstract [en]

    Within the European Union (EU27) the two most important gold producers are Finland and Sweden, covering more than two thirds of the European market. Due to the high gold prize mining companies are looking to extract more of the metal by improving recovery. We have done textural analysis on three gold-bearing deposits to better understand how the gold-textures seen in drill cores might affect the processing of different gold-ore types. In the Nautanen IOCG deposit, gold deportment is different whether gold is associated with pyrite or magnetite, and this must be considered when optimising the future mine and process planning. In the VMS-type Kristineberg deposit, the gold is associated with pyrite, sphalerite, and galena. Low gold recoveries from flotation could be explained by the occurrence of gold-inclusions in the pyrite. In the epigenetic Svartliden lode gold deposit, the gold is rather coarse-grained and associated with arsenopyrite-löllingite, and silicates. The relatively large grain size of gold can result in incomplete breakdown of the largest gold grains in the cyanide leaching process. To properly understand gold deportment in ores and to be able to improve mine planning and predict metal recoveries a comprehensive textural analysis of gold in drill core-samples is essential.

  • 250.
    Barrirero, Jenifer
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Department of Material Science, Saarland University, Saarbrücken, Germany.
    Eutectic Modification of Al-Si casting alloys2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Aluminum alloys with silicon as the major alloying element are the most widely used aluminum casting alloys. The eutectic phase in these alloys is formed by hard and brittle silicon plates in an aluminum matrix. Such silicon plates can act as crack propagation paths deteriorating the toughness of the material. To enhance ductility, silicon can be modified to a coral-like microstructure by addition of a modifying agent. Amongst the elements proposed as modifiers, only strontium, sodium and europium induce a plate-tocoral transition, while others such as ytterbium, only refine the silicon plates. The exact mechanism for the remarkable plate-to-coral change, and the reason why certain elements only refine the structure, is still not completely understood.

    In this investigation, atom probe tomography and transmission electron microscopy were used to analyze and compare the crystal structure and the distribution of solute atoms in silicon at the atomic level. An unmodified alloy and alloys modified by strontium, sodium, europium and ytterbium were studied. Elements inducing silicon plate-to-coral transition were found to contain nanometer sized clusters at the defects in silicon with stoichiometries corresponding to compounds formed at the ternary eutectic reaction of each system. In contrast, the addition of ytterbium, that only refines the silicon plates, is unable to form clusters in silicon. We propose that the formation of ternary compound clusters AlSiNa, Al2Si2Sr and Al2Si2Eu at the silicon / liquid interface during solidification restrict silicon growth. The formation of clusters on silicon facets create growth steps and increase growth direction diversity. The incorporation of clusters in silicon explains the high density of crystallographic defects and the structural modification from plates to corals.

    The parallel lattice plane-normals 011Si // 0001Al2Si2Eu, 011Si // 610Al2Si2Eu and 111Si // 610Al2Si2Eu were found between Al2Si2Eu and silicon, and absent between Al2Si2Yb and silicon. We propose a favorable heterogeneous formation of Al2Si2Eu on silicon. The misfit between 011Si and 0002Al2Si2X interplanar spacings shows a consistent trend with the potency of modification for several elements such as strontium, sodium, europium, calcium, barium, ytterbium and yttrium.

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