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  • 301.
    Asp, Leif
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Szpieg, Magdalena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Wysocki, Maciej
    Swerea SICOMP AB.
    Mechanical performance and modelling of a fully recycled modified CF/PP composite2012Inngår i: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 46, nr 12, s. 1503-1517Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A fully recycled carbon fiber reinforced maleic anhydride grafted polypropylene (MAPP)-modified polypropylene (rCF/rPP) composite material has been developed and characterized. This new composite was manufactured employing papermaking principles, dispersing the recycled carbon fibers (rCF) in water, and forming them into mats. Two layers of the recycled polypropylene (rPP) films manufactured using press-forming were sandwiched between three rCF preform layers in a stack. The stack was heated and press-formed resulting in a composite plate with a nominal thickness of 1.20 mm and a fiber volume fraction of 40%. A series of tensile tests using rectangular specimens cut in four different directions (0°, 90°, ± 45°) in the composite plate were performed to confirm in-plane material isotropy. Models to predict stiffness and strength of the short fiber rCF/rPP composite were also employed and validated using experiments. The models were found to be in good agreement with experimental results. Fiber length distribution measurements were performed before (unprocessed) and after (processed) composite manufacturing to investigate the influence of processing on fiber degradation. The results revealed a significant reduction in fiber length by the press-forming operation. To model the viscoelastic and viscoplastic responses of the composite an inelastic material model was employed and characterized using a series of creep and recovery tests. From the creep tests, it was found that the time and stress dependence of viscoplastic strains follows a power law. The viscoelastic response of the composite was found to be linear in the investigated stress range. The material model was validated in constant stress rate tensile tests and the agreement was good, even close to the rupture stress.

  • 302.
    Atiyah, H.
    et al.
    Faculty of Engineering, The University of Nottingham.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Petring, D.
    Fraunhofer Institute for Laser Technology ILT.
    Stoyanov, S.
    Fraunhofer Institute for Laser Technology ILT.
    Voisey, T.
    Faculty of Engineering, The University of Nottingham.
    Fiber laser cutting: The use of carbon-filled acrylic as a qualitative and quantitative analysis tool2018Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 30, artikkel-id 032009Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The use of carbon-filled black acrylic (CFBA) as a quantitative and qualitative analytical tool for fiber laser cutting is investigated. In the qualitative work, CFBA targets placed below the laser cutting zone when cutting stainless steel showed a distinctive “leaf” shaped evaporation crater which can provide information about the nature of the reflections taking place in the cut zone. Quantitative measurements have revealed a specific evaporation energy of 3.4 J/mm3 for CFBA. However, this figure is only applicable when considering intense beams when the CFBA target is stationary with respect to the laser beam.

  • 303.
    Avila, Marta
    et al.
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Burks, Terrance
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Stockholm University.
    Göthelid, Mats
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Lansåker, Pia C
    Department of Engineering Sciences, The Ångström Laboratory, Uppsala University.
    Toprak, Muhammet S
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Muhammed, Mamoun
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Uheida, Abdusalam
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Surface functionalized nanofibers for the removal of chromium (VI) from aqueous solutions2014Inngår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 245, s. 201-209Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polyacrylonitrile (PAN) nanofibers functionalized with amine groups (PAN-NH2) were prepared using a simple one-step reaction route. The PAN-NH2 nanofibers were investigated for the removal of chromium(VI) from aqueous solutions. The adsorption and the kinetic characteristics were evaluated in batch process. The adsorption process showed pH dependence and the maximum Cr(VI) adsorption occurred at pH = 2. The Langmuir adsorption model described well the experimental adsorption data and estimated a maximum loading capacity of 156 mg/g, which is a markedly high value compared to other adsorbents reported. The kinetics studies indicated that the equilibrium was attained after 90 min and the experimental data followed a pseudo-second order model suggesting a chemisorption process as the rate limiting step. X-ray Photoelectron Spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) revealed that the adsorption of Cr(VI) species on PAN-NH2 was facilitated through both electrostatic attraction and surface complexation. High desorption efficiency (>90%) of Cr(VI) was achieved using diluted base solutions that may allow the reuse of PAN-NH2 nanofibers.

  • 304.
    Awe, Samuel Ayowole
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Antimony recovery from complex copper concentrates through hydro- and electrometallurgical processes2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Today, one of the major difficulties confronted during copper metallurgy is the elimination of antimony and arsenic impurities from the process. 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. Therefore, removal of these impurities at an early stage of processing will be beneficial for the copper making process. The present research is aimed at (i) purifying impure complex copper sulphide concentrates by selectively dissolving the impurities, and consequently, upgrading the concentrates for pyrometallurgical processing, and (ii) depositing antimony as a marketable product from synthetic alkaline sulphide pregnant leach liquors by electrowinning. The mineralogical investigations conducted on the concentrates studied revealed that tetrahedrite, chalcopyrite, galena, sphalerite and pyrite were the common mineralogical phases present in the concentrates. Silver and arsenic were found as solid solution in the tetrahedrite crystal structure. Alkaline sulphide solution was used to dissolve antimony from the concentrates. Antimony recovery from tetrahedrite dissolution was increased by approximately 280% when the reaction temperature was increased from 84⁰C to 105⁰C. By raising the concentration of Na2S from 60 g/L to 100 g/L, the extraction of Sb was raised by a factor of 3 while increase in NaOH concentration from 30 g/L to 60 g/L enhanced the recovery by 140%. It was found that the leaching yield decreased by about 37% when the mineral particle size of the concentrate was increased from -53+38 µm to -106+75 µm. Under the selected leaching conditions, the estimated activation energy of tetrahedrite dissolution in the leaching reagent was 81 kJ/mol, which is indicative of a chemically controlled leach process. Characterisation of the leach residue by XRD and QEMSCAN proves that the alkaline sulphide lixiviant is selective and effective to dissolve the antimony and arsenic from the complex concentrate. The average crystal chemical formulae of the solid residue determined by QEMSCAN indicate the conversion of tetrahedrite into a new copper sulphide having stoichiometry of Cu1.64S. Tetrahedrite in the concentrate was reduced from 30.2% to 1.1% in the purified leach residue.Moreover, the results of electrowinning tests showed that the initial Na2S concentration had a significant influence on Sb deposition from this specific system. Current efficiency decreased remarkably when Na2S concentration was increased to 150 g/L. The test results indicated that the desired Na2S concentration should be less than 100 g/L. Faraday efficiency increased with increase in current density provided that the residual Sb concentration in the electrolyte remained above 20 g/L. Increase in NaOH concentration from 100 to 400 g/L raised the current efficiency by a factor of almost 1.5 while the specific energy requirement was reduced from 2.3 to 1.9 kWh/kg. Experimental results demonstrated that the specific energy decreased by almost 38% as the electrolyte temperature increased from 45 to 90⁰C and the optimum temperature should be between 50 and 75⁰C to reduce the heating cost. It was noted that polysulphide and thiosulphate had an adverse effect on Sb deposition. Current efficiency of the process decreased sharply from 83% to 32% when the polysulphide concentration was increased from 0 to 30 g/L; and at this polysulphide concentration, the specific energy was raised from 1.7 to 4.9 kWh/kg. Sparging of the electrolyte facilitates a smooth and adherent antimony deposit with an improved purity. The results from these experiments demonstrated that the anodic reactions were influenced by anodic current density and NaOH concentration. The molar concentration ratio between hydroxide and free sulphide ions must be ≥ 7.3 to produce appreciable amounts of sulphate in the electrolytic process. The amount of sulphate formed increased from 0.5 to 16.9 g/L when the anodic current density was increased from 500 to 2500 A/m2. By raising NaOH concentration from 100 to 400 g/L, the production of sulphate at the anode was enhanced by 6.2 g/L increment. However, the concentration of thiosulphate formed during the electrolysis decreased with increasing anode current density and NaOH concentration. The main factors influencing the purity of the antimony deposits were current density and NaOH concentration. Antimony purity was lowered from 99.9% to 99.2% when the current density was increased from 50 to 250 A/m2. Sparging of the electrolyte during the electrodeposition enhanced antimony purity by 0.4%. Finally, a simplified integrated hydro-/electro-metallurgical process flowsheet for antimony removal and recovery from Rockliden sulphide copper concentrate was developed. The experimental results from this investigation confirmed that different concentrations of Na2S and NaOH were needed at leaching and electrowinning stages to achieve an efficient process. 

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  • 305.
    Awe, Samuel Ayowole
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Hydrometallurgical upgrading of a tetrahedrite-rich copper concentrate2010Licentiatavhandling, med artikler (Annet vitenskapelig)
    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 antimony, arsenic, mercury and bismuth, which need to be eliminated. The present work aims at pre-treating a tetrahedrite rich complex copper sulphide concentrate by selective dissolution of the impurities, therefore, upgrading it for pyrometallurgical processing. Characterisation of the complex concentrate was performed and the result shows that antimony and part of arsenic were present as tetrahedrite and bournonite. Dissolution kinetics of tetrahedrite in aqueous alkaline sodium sulphide solutions was investigated. It was found that the rate of dissolving tetrahedrite by the lixiviant increases with increase in reaction temperature, sodium sulphide concentration, sodium hydroxide concentration, and with decrease in mineral particle size. The kinetic study indicates that the rate of leaching tetrahedrite in the lixiviant under the selected conditions is chemically controlled through the particle surface reaction. The activation energies of the process were estimated as 81 kJ/mol and 75 kJ/mol, respectively, for antimony and arsenic dissolution from tetrahedrite. The estimated activation energies were within the range reported for a chemically controlled reaction process. Besides, the alkaline sulphide lixiviant proves 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. Analysis of the leach residue indicates that copper content of the 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 in the concentrate were found to have reduced to a level satisfactory for smelting operation.Furthermore, modelling and optimisation of alkaline sulphide leaching of a complex copper concentrate containing 1.69% Sb and 0.14% Sn were conducted. Response surface methodology, in combination with central composite face-centred design (RSM-CCF), was used to optimise the operating parameters. The leaching temperature, sulphide ion concentration and solid concentration were chosen as the variables, and the response parameters were antimony and tin recoveries, and the time required to achieve 90% Sb dissolution. It was seen that the leaching process was strongly dependent on the reaction temperature as well as the sulphide ion concentration without any significant dependence on the solid concentration. Additionally, a mathematical model was constructed to characterise the leaching behaviour within the experimental range studied. The results from the model allow identification of the most favourable leaching conditions. The model was validated experimentally, and the results show that the model is reliable and accurate in predicting the leaching process.

    Fulltekst (pdf)
    FULLTEXT01
  • 306. Awe, Samuel Ayowole
    et al.
    Khoshkhoo, Mohammad
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Kruger, Paul
    Boliden Mineral AB.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Modelling and process optimisation of antimony removal from a complex copper concentrate2012Inngår i: Transactions of Nonferrous Metals Society of China, ISSN 1003-6326, E-ISSN 2210-3384, Vol. 22, nr 3, s. 675-685Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The modelling and optimization for the alkaline sulphide leaching of a complex copper concentrate containing 1.69% Sb and 0.14% Sn were studied. Response surface methodology, in combination with central composite face-centred design (RSM-CCF), was used to optimise the operating parameters. The leaching temperature, sulphide ion concentration and solid concentration werechosen as the variables, and the response parameters were antimony and tin recovery, and the time required to achieve 90% Sb dissolution. It was confirmed that the leaching process was strongly dependent on the reaction temperature as well as the sulphide ion concentration without any significant dependence on the solid concentration. Furthermore, a mathematical model was constructed tocharacterise the leaching behaviour. The results from the model allow identification of the most favourable leaching conditions. The model was validated experimentally, and the results show that the model is reliable and accurate in predicting the leaching process.

  • 307.
    Awe, Samuel Ayowole
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Lennartsson, Andreas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mostaghel, Sina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Samuelsson, Caisa
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Wise process routes for varying feedstock in base metal extraction2011Inngår i: Proceedings, European Metallurgical Conference EMC 2011: Process Metallurgy, Recycling/Waste Treatment and Prevention, Germany: GDMB , 2011, Vol. 4, s. 1315-1322Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In Sweden, there are several large but low-grade ore deposits that have not been extracted so far. The main reason is presence of impurities such as arsenic and antimony that increase the overall cost of the process and make the extraction uneconomical. In-depth experimental studies, plant data and theoretical modelling and innovations are needed to develop new techniques for an efficient use of the resources. Besides, recycling of metals from end of life scrap and metal containing waste, e.g. waste electric and electronic equipment (WEEE), is an important part of a metal production plant. Most of these secondary raw materials contain mixtures of different metals together with various plastics and ceramics that may adversely affect products and by-products of the metallurgical opera-tion. Therefore, a thorough study on how to control possible changes of properties is required. The aim of the research is to develop an optimum combination of hydro- and pyro- metallurgical path-ways to bleed out impurities from the metal extraction chain and/or convert them into valuable by-products. The first part of the current paper focuses on impurity removal from a complex copper concentrate as an upgrading stage. It is shown that by selective dissolution of tetrahedrite in alkaline sulphide solution, antimony and arsenic would be eliminated and the concentrate can be treated in pyro-metallurgical processes. In the second part of the paper, influences of one of the most common and significant compounds that is included in most of the secondary raw materials, alumina Al2O3, on properties of a copper production slag are explained. Results show that increased alumina content of the slag will cause formation of a new phase and rises the liquidus temperature, while its leaching properties are not adversely affected.

  • 308. Awe, Samuel Ayowole
    et al.
    Samuelsson, Caisa
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Dissolution kinetics of tetrahedrite mineral in alkaline sulphide media2010Inngår i: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 103, nr 1-4, s. 167-172Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present study investigates the dissolution kinetics of tetrahedrite in aqueous alkaline sodium sulphide solutions. Effect of reaction temperature, mineral particle size, sodium sulphide and sodium hydroxide concentrations on antimony and arsenic dissolution rate from tetrahedrite were studied. It was found that the rate of reaction increases with increase in reaction temperature, sodium sulphide concentration, and sodium hydroxide concentration and with decrease in mineral particle size. The kinetic study indicates that the rate of tetrahedrite leaching in the lixiviant under selected conditions is chemically controlled through the particle surface reaction. The estimated activation energies were found to be 81 kJ/mol and 75 kJ/mol, respectively, for antimony and arsenic dissolution from tetrahedrite, which are in agreement with the values of activation energies reported for the chemically controlled reaction process

  • 309.
    Awe, Samuel Ayowole
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Samuelsson, Caisa
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Elimination and recovery of antimony from copper resources2013Konferansepaper (Fagfellevurdert)
    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.

    Fulltekst (pdf)
    FULLTEXT01
  • 310.
    Awe, Samuel Ayowole
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Electrowinning of antimony from model sulphide alkaline solutions2013Inngår i: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 137, s. 60-67Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 311. Awe, Samuel Ayowole
    et al.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Leaching mechanism of tetrahedrite in alkaline sulfide solution2010Inngår i: Conference in Minerals Engineering: Luleå, 2 -3 februari 2010, Luleå tekniska universitet, 2010, s. 13-24Konferansepaper (Annet vitenskapelig)
    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.

    Fulltekst (pdf)
    FULLTEXT01
  • 312. Awe, Samuel Ayowole
    et al.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Selective leaching of arsenic and antimony from a tetrahedrite rich complex sulphide concentrate using alkaline sulphide solution2010Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 23, nr 15, s. 1227-1236Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 313.
    Awe, Samuel Ayowole
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Tratamiento hidro-electrometalúrgicos de un concentrado de cobre con contenido de tetraedrita2014Inngår i: Mineria, ISSN 0026-4679, Vol. 439, s. 46-52Artikkel i tidsskrift (Fagfellevurdert)
    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.

    Fulltekst (pdf)
    FULLTEXT01
  • 314.
    Awe, Samuel Ayowole
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Upgrading of an impure copper concentrate for pyrometallurgical processing2011Inngår i: Proceedings, European Metallurgical Conference EMC 2011: Copper/ General Pyrometallurgy/ Vessel Integrity/ Process Gas Treatment, Dusseldorf, Germany: GDMB , 2011, Vol. 1, s. 15-31Konferansepaper (Fagfellevurdert)
    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.

  • 315.
    Awe, Samuel Ayowole
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sundkvist, Jan-Eric
    Boliden Mineral AB.
    Bolin, Nils-Johan
    Boliden Mineral AB.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Process flowsheet development for recovering antimony from Sb-bearing copper concentrates2013Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 49, s. 45-53Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 316.
    Awe, Samuel Ayowole
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sundkvist, Jan-Eric
    Boliden Mineral AB.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Formation of sulphur oxyanions and their influence on antimony electrowinning from sulphide electrolytes2013Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 53, s. 39-47Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 317.
    Axelsson, Hans
    et al.
    Alfa Laval Separation AB.
    Westberg, Törbjörn
    Alfa Laval Separation AB.
    Wiese, Karin
    Luleå tekniska universitet.
    Våtklassering med centrifug vid höga koncentrationer1995Inngår i: Konferens i mineralteknik: Luleå, 14-16 februari 1995 / [ed] Marianne Thomaeus; Eric Forssberg, MinFo , 1995, s. 213-223Konferansepaper (Annet vitenskapelig)
  • 318.
    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 tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Paul, Jan
    Leaching of radioactive isotopes from ash2003Konferansepaper (Annet vitenskapelig)
    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

    Fulltekst (pdf)
    FULLTEXT01
  • 319.
    Ayyala, Sekhar
    Luleå tekniska universitet.
    Influence of hydrodynamics on hydrophobic flocculation of galena1995Licentiatavhandling, monografi (Annet vitenskapelig)
  • 320.
    Ayyala, Sekhar
    et al.
    Luleå University of Technology.
    Pugh, R.J.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Aggregate characteristics in coagulation and flocculation1995Inngår i: Mineral Processing and Extractive Metallurgy Review, ISSN 0882-7508, E-ISSN 1547-7401, Vol. 12, nr 2-4, s. 165-165Artikkel i tidsskrift (Fagfellevurdert)
  • 321.
    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 tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Effect of corrosion inhibitors on grinding and flotation of a lead-zinc ore1993Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 6, nr 8, s. 929-935Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 322.
    Azadian, S.
    et al.
    Luleå tekniska universitet.
    Liu-Ying, Wei
    Luleå tekniska universitet.
    Niklasson, F.
    Warren, Richard
    Luleå tekniska universitet.
    Precipitation in spray-formed IN 7182001Inngår i: Superalloys 718, 625, 706 and various derivatives: proceedings of the International Symposium on Superalloys 718, 625, 706 and Various Derivatives ; held June 17 - 20, 2001, Warrendale, Pa: Minerals, Metals & Materials Society, 2001, s. 617-626Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The precipitation of the γ', γ'' and δ phases in a spray-formed version of IN 718 has been studied by hardness measurement and metallographic examination of samples subjected to solution treatment at 1025°C followed by isothermal treatments between 620 and 1010°C up to 100 h. The precipitation processes were compared to those in a wrought (ring-rolled) version of the alloy subjected to the same heat treatments. Time-temperature-hardness diagrams for the two alloys were constructed. Small differences were observed between the two materials but these can at least partly be attributed to differences in composition. For the spray-cast material the δ-phase solvus temperature was determined and the growth kinetics of the γ'' phase established

  • 323. Azadian, S.
    et al.
    Wei, L-Y.
    Warren, Richard
    Luleå tekniska universitet.
    Delta phase precipitation in inconel 7182004Inngår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 53, nr 1, s. 7-16Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The precipitation and dissolution kinetics of the δ-phase were studied in three wrought versions and one spray-formed (SF) version of the nickel alloy, Inconel 718. The precipitation in the spray-formed version and one wrought version was followed during isothermal ageing for up to 100 h between 700 and 1000°C. The δ-phase precipitates in the form of nonuniformly distributed thin platelets and an alternative method of measuring volume fraction of this precipitate morphology is proposed. At and above 800°C, the precipitation was measured quantitatively in terms of the volume fraction and platelet thickness distribution. The maximum rate of precipitation occurred at approximately 900°C. The solvus temperature lay between 1005 and 1015°C for Nb contents of 5.06 and 5.41 wt.%, respectively. A study was made of the dissolution of the δ-phase in all four alloys using isochronal treatments and this confirmed the above solvus temperature range. The effect of δ-phase and its dissolution on the grain growth of the alloys was also determined.

  • 324.
    Azadian, Saied
    Luleå tekniska universitet.
    Aspects of precipitation in alloy Inconel 7182004Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    A study was made of the microstructure of the Ni-base alloy Inconel 718 with emphasis on the precipitation and stability of intermetallic phases as affected by heat treatments. In addition the effect of the precipitation on selected mechanical properties namely hardness, creep notch sensitivity and hot ductlity were investigated. The materials studied were a spray-formed version and three wrought versions of the alloy. The spray-formed version of the alloy was of interest since it exhibited a superior compositional homogeneity to more conventional forms of the alloy. To characterise the precipitation kinetics and to determine the associated hardening, a series of isothermal ageing treatments were carried out on both spray-formed and ring rolled material at selected temperatures between 600°C and 1025°C for up to 100h. The results were presented in the form of TTH diagrams for the two alloys. The heat treated specimens were then studied using optical microscopy, scanning electron microscopy and transmission electron microscopy. Where possible these were supplemented with quantitative metallographic measurements of volume fraction and precipitates size.The three main intermetallic precipitation phases in IN 718 are (i) gamma’ having a composition Ni3(Al,Ti), a cubic crystal structure and cubic or spherical particle shape (ii) gamma” having a composition Ni3Nb, a bct crystal structure and a lens-like disc shape (iii)delta having composition Ni3Nb, an orthorhombic crystal structure and forming as grain boundary particles and films as well as thin plates extending long distances into the grains. In thermomechanically processed material the delta-phase can also occur as shorter platelets and particles resulting from fragmentation of the original plates. In this work the rates of precipitation and the temperature ranges of their existence were determined qualitatively. Moreover the coarsening of the ganmma" precipitates was determined quantitatively. The kinetics of precipitation and dimensional coarsening of the delta-phase were also established quantitatively. Similarly, the dissolution kinetics of the delta-phase were measured in the spray-formed and three wrought versions of the alloy leading to a determination of the effect of Nb-content on the delta solvus temperature. After a standard heat treatment, the spray-formed IN 718 was found to be creep notch sensitive according to an SAE-AMS standard rupture test. It was found that notch ductility could be restored to the alloy by inserting a delta-phase precipitation treatment at 875°C-900°C prior to the standard heat treatment. This could be attributed to the formation of a more favourable delta-phase morphology than that formed during the solution treatment at 954°C in the standard heat treatment cycle. A study was made of high temperature tensile properties of a wrought version of IN 718 in particular in relation to the problem of hot cracking in repair welding. Measurements were made of the strength loss temperature on heating and the strength and ductility return temperatures on cooling. These properties provide an indication of the sensitivity of the alloy to hot cracking due to liquation. The tests were made on the alloy after various heat treatments designed to produce microstructures with two different grain sizes with and without delta-phase precipitation. Hot tensile tests were also performed on the in-situ solidified alloy in order to describe the weld metal ductility and properties. The grain size and the presence of large fractions of delta-phase precipitated at 900°C had only small effects on the strength loss temperature and brittle-ductile transition of the alloy. On the other hand, a small fraction of delta-phase precipitated in the grain boundaries at 960°C reduced the brittle-ductile transition temperature significantly. It is proposed that the reduction was associated with interaction between the grain boundary delta-phase and grain boundary boron segregation that was observed in all the heat treated materials.

    Fulltekst (pdf)
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  • 325.
    Azizoğlu, Yağız
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik. Luleå University of Technology.
    Modeling of Cold Pilgering of Tubes2017Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Cold pilgering is a challenging tube forming process in terms of modeling due to the complexity in kinematic of tools, friction condition and material behavior. The process development has mostly been based on simple formulas and costly full-scale tryouts. The aim in this study is to develop validated Finite element models of cold pilgering to increase the understanding of influence of the process parameters on the produced tubes.

    In the course of this thesis, three-dimensional mechanical and thermo-mechanical Finite element models of cold pilgering were developed. The commercial code MSC.Marc was used in the simulations. General 3D models are needed to be able to capture asymmetric deformation in cold pilgering. It was found that tool deflections together with elastic deformation of roll dies have considerable influence on the rolling force. Furthermore, the strain rate and temperature effects on the response of the material and thereby on the rolling force were evaluated.

    Fulltekst (pdf)
    fulltext
  • 326.
    Azizoğlu, Yağız
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gärdsback, Mattias
    Sandvik Materials Technology, R&D, Sandviken.
    Sjöberg, Bengt
    Sandvik Materials Technology, R&D, Sandviken.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Finite Element Analysis of cold pilgering using elastic roll dies2017Inngår i: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 207, s. 2370-2375Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A finite element model of cold pilgering with elastic roll dies have been developed and used to investigate the influence of roll die deformation on the material flow, contact region, roll separating force and tube dimensions. Full scale experiments were performed to validate the contact surface and tube dimensions. The results show that the influence of roll die flattening is not significant on the contact length. However, elastic deformation of roll die has strong influence on both the wall thickness reduction and roll separating force. Thus it is recommended to consider elasticity of roll dies when forces and tube dimensions are estimated.

    Fulltekst (pdf)
    fulltext
  • 327.
    Azizoğlu, Yağız
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gärdsback, Mattias
    Sandvik Mat Technol, R&D, SE-81181 Sandviken.
    Sjöberg, Bengt
    Sandvik Mat Technol, R&D, SE-81181 Sandviken.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Finite element modeling of tube deformation during cold pilgering2016Inngår i: NUMIFORM 2016: The 12th International Conference on Numerical Methods in Industrial Forming Processes / [ed] Saanouni, K; Chenot, JL; Duval, JL, 2016, Vol. 80, s. 1-8, artikkel-id 15004Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A three-dimensional finite element model of cold pilgering of stainless steel tubes is developed in this paper. The objective is to use the model to increase the understanding of forces and deformations in the process. The focus is on the influence of vertical displacements of the roll stand and axial displacements of the mandrel and tube. Therefore, the rigid tools and the tube are supported with elastic springs. Additionally, the influences of friction coefficients in the tube/mandrel and tube/roll interfaces are examined. A sensitivity study is performed to investigate the influences of these parameters on the strain path and the roll separation force. The results show the importance of accounting for the displacements of the tube and rigid tools on the roll separation force and the accumulative plastic strain.

  • 328.
    Azizoğlu, Yağız
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gärdsback, Mattias
    Dalarna University.
    Sjöberg, Bengt
    Dalarna University.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Finite Element Modelling of Cold Pilgering of Tubes2015Inngår i: Computational Plasticity XIII: Fundamentals and Applications - Proceedings of the 13th International Conference on Computational Plasticity - Fundamentals and Applications,held in Barcelona, Spain, 1-3 September 2015 / [ed] E. Oñate; D.R.J. Owen; D. Peric; M. Chiumenti, Barcelona: International Center for Numerical Methods in Engineering (CIMNE), 2015, s. 716-726Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Cold pilgering is a cold forming process used during manufacturing of seamless tubes. The tube with a mandrel inside is fed forward and rotated in stepwise increments, while the roll stand moves back and forth. The total plastic deformation of the tube is such that the cross-sectional area of the tube decreases and the length of the tube increases during the process. However, this is performed in many small incremental steps, where the direction of deformation in a material point changes at each stroke. Most published models of cold pilgering use simplified material models. In reality, the flow stress is dependent on temperature, strain rate, strain history and microstructure. In this work, temperature and strain rate distributions are computed, using a 3D thermo-mechanical FE model, and the influence of temperature and strain rate on the rolling force is investigated. The Johnson-Cook model is employed to describe the flow stress using isotropic hardening. The results show that strain rate and temperature have a significant influence on the roll separation force

  • 329.
    Babu, Bijish
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Dislocation density based constitutive model for Ti-6Al-4V at low strain rates2007Inngår i: Ti-2007 : science and technology: proceedings of the 11th World Conference on Titanium (JIMIC 5), held at Kyoto International Conference Center, Kyoto, Japan, 3 - 7 June 2007 / [ed] M. Niinomi, Kyoto: Japan Institute of Metals , 2007, s. 311-314Konferansepaper (Fagfellevurdert)
  • 330.
    Babu, Bijish
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Dislocation density based constitutive model for Ti-6Al-4V: including recovery and recrystallisation2007Inngår i: Computational plasticity: Fundamentals and Applications / [ed] Eugenio Onate; Roger Owen; Benjamin Suarez, International Center for Numerical Methods in Engineering (CIMNE), 2007, s. 631-634Konferansepaper (Fagfellevurdert)
  • 331.
    Babu, Bijish
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Dislocation density model for plastic behaviour of Ti-6-42006Inngår i: WCCM VII: 7th World Congress on Computational Mechanics ; Los Angeles, California, USA ; July 16 - 22, 2006, MAdison, Wis: Omnipress , 2006Konferansepaper (Annet vitenskapelig)
  • 332.
    Babu, Bijish
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik. Swerea MEFOS AB.
    Mechanism-based flow stress model for Ti-6Al-4V: applicable for simulation of additive manufacturing and machining2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Ti-6Al-4V has remarkable properties such as high specific mechanical properties (viz. stiffness, strength, toughness, fatigue resistance), corrosion resistance, biocompatibility etc. These properties make it attractive for applications in aerospace, chemical industry, energy production, surgical implants, etc. Many of these applications have to satisfy high requirements on mechanical properties, which are directly affected by the microstructure. Therefore, it is essential to understand as well as to model the microstructure evolution during manufacturing as well as in-service. Furthermore, this alloy has a narrow temperature and strain rate window of workability.

    This work was initiated as part of a project aimed at performing finite element simulations of a manufacturing process chain involving hot forming, welding, machining, additive manufacturing and heat treatment of Ti-6Al-4V components within the aerospace industry. Manufacturing process chain simulations can compute the cumulative effect of the various processes by following the material state through the whole chain and give a realistic prediction of the final component. Capacity to describe material behavior in a wide range of temperatures and strain rates is crucial for this task.

    A material model based on the dominant deformation mechanisms of the alloy is assumed to have a more extensive range of validity compared to an empirical relationship. Explicit dislocation dynamics based models are not practically feasible for manufacturing process simulation, and therefore the concept of dislocation density, (length of dislocations per unit volume) developed by (Kocks1966; Bergström, 1970) is followed here. This mean field approach provides a representation of the average behavior of a large number of dislocations, grains, etc. Conrad (1981) studied the influence of various factors like solutes, interstitials, strain, strain rate, temperature, etc., on the strength and ductility of titanium systems and proposed a binary additive relationship for its yield strength. The first component relates to long-range interactions and second short-range relates to lattice resistance for dislocation motion. For high strain rate deformation, this short-range term is extended to include the effects of a viscous drag given by phonon and electron drag (Lesuer et al. 2001).  Immobilisation of dislocation by pile-ups gives hardening and remobilization/annihilation by dislocation glide and climb gives restoration. Globularization is also considered to restore the material. The material model is calibrated using isothermal compression tests at a wide range of temperatures and strain rates. Compression tests performed using Gleeble thermo-mechanical simulator is used at low-strain rates and split-Hopkins pressure bar is used at high strain rates for calibration.

    During additive manufacturing depending on the temperature, heating/cooling rates, Ti-6Al-4V undergoes allotropic phase transformation. This transformation results in a variety of textures that can give different mechanical properties.  Based on the texture (Semiatin et al., 1999b; Seetharaman and Semiatin, 2002; Thomas et al., 2005) identified few microstructural features that are relevant to the mechanical properties. The three separate alpha phase fractions; Widmanstatten,  grain boundary, Martensite, and the beta-phase fraction are included in the current model. However, since the strengthening contributions of these individual alpha phases are not known, a linear rule of mixtures for the total alpha-beta composition is developed. This model is calibrated using continuous cooling tests performed by Malinov et al. 2001 with differential scanning calorimeter at varying cooling rates.  

    This mechanism-based model is formulated in such a way that it can be implemented in any standard finite element software. In the current work, this is implemented as subroutines within MSC Marc and used for simulation of hot-forming and additive manufacturing. 

    Fulltekst (pdf)
    fulltext
  • 333.
    Babu, Bijish
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Physically based model for plasticity and creep of Ti-6Al-4V2008Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Albeit Ti-6Al-4V has numerous salient properties, its usage for certain applications is limited due to the challenges faced during manufacturing. Understanding the dominant deformation mechanisms and numerically modelling the process is the key to overcome this hurdle. This work investigates plastic deformation of the alloy at strain rates from 0.001/s to 1/s and temperatures between 20 and 1100 Celsius. Pertinent deformation mechanisms of the material when subjected to thermo-mechanical processing is discussed. A physically based constitutive model based on the evolution of immobile dislocation density and excess vacancy concentration is developed. Parameters of the model are obtained by calibration using isothermal compression tests. Model is compared with relaxation test data to demonstrate its validity.

    Fulltekst (pdf)
    FULLTEXT01
  • 334.
    Babu, Bijish
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Dislocation density based model for plastic deformation and globularization of Ti-6Al-4V2013Inngår i: International journal of plasticity, ISSN 0749-6419, E-ISSN 1879-2154, Vol. 50, s. 94-108Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although Ti-6Al-4V has numerous salient properties, its usage for certain applications is limited due to the challenges faced during manufacturing. Understanding the dominant deformation mechanisms and numerically modeling the process is the key to overcoming this hurdle. This paper investigates plastic deformation of the alloy at strain rates from 0.001s−1 to 1s−1 and temperatures between 20° C and 1100° C. Pertinent deformation mechanisms of the material when subjected to thermo-mechanical processing are discussed. A physically founded constitutive model based on the evolution of immobile dislocation density and excess vacancy concentration is developed. Parameters of the model are obtained by calibration using isothermal compression tests. This model is capable of describing plastic flow of the alloy in a wide range of temperature and strain rates by including the dominant deformation mechanisms like dislocation pile-up, dislocation glide, thermally activated dislocation climb, globularization, etc. The phenomena of flow softening and stress relaxation, crucial for the simulation of hot forming and heat treatment of Ti-6Al-4V, can also be accurately reproduced using this model.

  • 335.
    Babu, Bijish
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lundbäck, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Dislocation density based constitutive model for Ti-6Al-4V used in simulation of metal deposition2007Inngår i: Svenska Mekanikdagar 2007: Program och abstracts / [ed] Niklas Davidsson; Elianne Wassvik, Luleå: Luleå tekniska universitet, 2007, s. 84-Konferansepaper (Annet vitenskapelig)
    Fulltekst (pdf)
    FULLTEXT01
  • 336. Babu, Bijish
    et al.
    Lundbäck, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Physically based constitutive model for Ti-6Al-4V used in the simulation of manufacturing chain2009Inngår i: Computational Plasticity X: fundamentals and applications ; proceedings of the X International Conference on Computational Plasticity - fundamentals and applications held in Barcelona, Spain, 02 - 04 September 2009 / [ed] E. Onate; D.R.J. Owen; B. Suarez, International Center for Numerical Methods in Engineering (CIMNE), 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Simulations of manufacturing process chain involving forming, welding and heat treatment are complex because of the varying length and time scales and the range of temperatures which trigger the different associated deformation mechanisms. This paper demonstrates the use of a physically based constitutive model in simulation of a manufacturing chain.

  • 337.
    Babu, Bijish
    et al.
    Swerim AB, Heating and Metalworking, Luleå, Sweden.
    Lundbäck, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Simulation of Ti-6Al-4V Additive Manufacturing Using Coupled Physically Based Flow Stress and Metallurgical Model2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 23, artikkel-id 3844Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Simulating the additive manufacturing process of Ti-6Al-4V is very complex due to the microstructural changes and allotropic transformation occurring during its thermomechanical processing. The α -phase with a hexagonal close pack structure is present in three different forms—Widmanstatten, grain boundary and Martensite. A metallurgical model that computes the formation and dissolution of each of these phases was used here. Furthermore, a physically based flow-stress model coupled with the metallurgical model was applied in the simulation of an additive manufacturing case using the directed energy-deposition method. The result from the metallurgical model explicitly affects the mechanical properties in the flow-stress model. Validation of the thermal and mechanical model was performed by comparing the simulation results with measurements available in the literature, which showed good agreement

  • 338.
    Babushkin, O.
    et al.
    Luleå tekniska universitet.
    Harrysson, Ralph
    Luleå tekniska universitet.
    Herbertsson, H.
    Luleå tekniska universitet.
    Lindbäck, Ture
    Morphological effect of Al2O3 additives on sinterability of wear-resistant AlN ceramics1990Inngår i: Structural ceramics processing, microstructure and properties: proceedings of the 11th Risø International Symposium on Metallurgy and Materials Science, 3-7 September 1990 / [ed] J.J. Benzen, Roskilde: Risø National Laboratory , 1990, s. 175-180Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the present study on AlN-based ceramic materials, an attempt was made to show the morphological influence of the precursors on the phase relationships during sintering as well as the microstructural development of the material. An investigation has been done of the phase transformations during pressureless sintering of wear-resistant ceramics based on the AlN-Al2O3-Y2O3 system in the AlN-rich field as well as a study of the effect of different precursors, such as Al2O3, AlCl3 and Al(NO3)3, on the sequence of phase transitions in the low temperature field (800-1400°C). The peculiarities of phase transitions in dynamic and isothermal schedules have also been discussed.

  • 339.
    Babushkin, O.
    et al.
    Luleå tekniska universitet.
    Harrysson, Ralph
    Luleå tekniska universitet.
    Lindbäck, Ture
    Tegman, R.
    Luleå tekniska universitet.
    High-temperature graphite furnace for X-ray powder diffraction1993Inngår i: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 4, nr 8, s. 816-819Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A modified computer-controlled high-temperature x-ray diffractometer with good stability and an upper temperature limit of more than 2300 K is described. A critical test of the system, determining the thermal expansion of Pt, Ni and AlN, showed close agreement with dilatometric and literature data. Lattice thermal expansion data of CrB2 and TiB2 up to 2100 K were also determined

  • 340.
    Babushkin, O.
    et al.
    Luleå tekniska universitet.
    Lindbäck, Ture
    Brooks, Keith
    École Polytechnique Fédérale de Lausanne.
    Setter, Nava
    École Polytechnique Fédérale de Lausanne.
    PZT phase formation monitored by high-temperature X-ray diffractometry1997Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 17, nr 6, s. 813-818Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The crystallisation kinetics of amorphous sol-gel PZT thin films were investigated using high-temperature X-ray diffraction. Crystallisation for different isotherms was monitored as a function of time. Phase transformation data were obtained from integrated X-ray peak intensities which were calibrated based on image analysis of the surface microstructure of the samples at the end of the isothermal treatments. An activation energy of 310 kJ/mol was obtained without assuming a specific kinetic model. From the transformation data, a TTT diagram was constructed for the ranges studied.

  • 341.
    Babushkin, O.
    et al.
    Luleå tekniska universitet.
    Lindbäck, Ture
    Holmgren, A.
    Jianguo, Li
    Hermansson, L.
    Thermal expansion of hot isostatically pressed hydroxyapatite1994Inngår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 4, nr 3, s. 413-415Artikkel i tidsskrift (Fagfellevurdert)
  • 342.
    Babushkin, O.
    et al.
    Luleå tekniska universitet.
    Lindbäck, Ture
    Luc, J.-C.
    Quartz et Silice Research Institute.
    Leblais, J.-Y.
    Quartz et Silice Research Institute.
    Kinetic Aspects of the Formation of Lead Zirconium Titanate1996Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 16, nr 12, s. 1293-1998Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The kinetics of the second calcination step in the formation of PZT solid solution (with perovskite ABO3 lattice) has been investigated by using two different particle sizes of the B-site precursor (1·91 and 5·08 μm), the finer size being obtained by prolonged milling. In-situ analysis performed by high-temperature X-ray diffractometry in a non-isothermal mode (20-800°C) revealed a reduction of the calcination temperature by 100°C with a decrease in particle size of the precursor. In order to clarify the mechanism of the solid-state reaction to PZT, isothermal heat treatment of the mixtures was performed in the temperature range 540-700°C. The activation energies for the fine and the coarse powders were estimated as 150 and 210 kJ mol 1 respectively, and the reaction was found to follow the Jander model for diffusion-controlled solid-state reaction kinetics

  • 343.
    Babushkin, O.
    et al.
    Luleå tekniska universitet.
    Lindbäck, Ture
    Warren, Richard
    Luleå tekniska universitet.
    Sprumont, M.
    Diffusionless phase transition in the ZrO2-TiO2 system1994Inngår i: Solid-solid phase transformations: proceedings of the International Conference on Solid-to-Solid Phase Transformations in Inorganic Materials, PTM'94, held at Nemacolin Woodlands, Farmington, Pennsylvania, U.S.A., July 17 - 22, 1994 / [ed] William C. Johnson; James H. Howe, Warrendale, Pa.: Minerals, Metals & Materials Society, 1994, s. 743-748Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Stable and metastable phase relationships in the ZrO2-TiO2 system were investigated using homogeneous samples with ZrO2 particles of different surface area. Phase analysis associated with the diffusionless and reversible monoclinic-tetragonal transition has been performed with high temperature X-ray diffractometry. The rate of the phase transition, depending on powder morphology, is presented. The character of the hysteresis loop associated with the martensitic phase change for pure ZrO2 and for the ZrO2-TiO2 system is discussed

  • 344.
    Babushkin, Oleg
    et al.
    Luleå tekniska universitet.
    Harrysson, Ralph
    Luleå tekniska universitet.
    Lindbäck, Ture
    Effect of sintering atmosphere and alumna precursors on the sequence of solid state reactions i the AlN-Y2O3-Al2O3 system1993Inngår i: Third Euro-ceramics conference: Madrid; 12-17 Sept. 1993 / [ed] P. Duran; J.F. fernandez, Faenza Editrice Iberica , 1993, Vol. vol. 1, s. 1079-1084Konferansepaper (Fagfellevurdert)
    Abstract [en]

    High temperature x-ray diffraction was used to investigate the evolution of phases at 1050 C in three AlN-based ceramic powder mixtures containing Al2O3 and Y2O3 additives. The overall composition was 87.5 mol% AlN, 10% Al2O3 and Y2O3 2.5%; the alumina precursors in the three mixtures were Al2O3, AlCl3 and Al(NO3)3 respectively. The effects of the tape of precursor and the heat treatment atmosphere (vacuum or nitrogen) on the phases formed and the sequence of their formation over a period of two hours, are presented and discussed.

  • 345.
    Babushkin, Oleg
    et al.
    Luleå tekniska universitet.
    Lindbäck, Ture
    Luc, J.-L
    Quartz et Silice Research Institute.
    Lebalis, J.-Y. M.
    Quartz et Silice Research Institute.
    Reaction sequence in the formation of perovskite Pb(Zro0.48Ti0.52)O3-Pb(Nb2/3Ni1/3)O3 solid solution: Dynamic heat-treatment1998Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 18, nr 7, s. 737-744Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The sequence of the solid state reactions in the PbOZrO 2-TiO2-Nb2O5-NiO system has been investigated. The oxide mixing route utilised in sample preparation was selected in order to determine the basic reaction path in the formation of the PZTPNN perovskite phase. It has been established that the main intermediate phases formed prior to PZTPNN are PbTiO3 and pyrochlore Pb-Nb-based phases. The sequence in the pyrochlore formation was from tetragonal Pb3Nb2O8 (500 °C) to rhombohedral Pb2Nb2O7 (600-750 °C) and finally to cubic Pb3Nb4O13 (650-850 °C). The formation of the perovskite phase proceeded from mutual solubility of PbTiO3 and pyrochlore Pb3Nb4O13 phases, accompanied by dissolving of residuals (PbZrO3 and NiO) in the perovskite solid solution formed

  • 346.
    Bachinger, A.
    et al.
    Composite Structures, Swerea SICOMP AB.
    Marklund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Composite Structures, Swerea SICOMP AB.
    Rössler, J.
    Hellström, Pär
    Composite Structures, Swerea SICOMP AB.
    Asp, Leif
    Composite Structures, Swerea SICOMP AB.
    Stiffness-modifiable composite for pedestrian protection2014Inngår i: 16th European Conference on Composite Materials, ECCM 2014: Seville, Spain, 22 - 26 June 2014, European Conference on Composite Materials, ECCM , 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A novel functional material allowing stiffness-reduction upon external stimulation was developed. Implementation of such technology in the design of a car front has high potential to result in increased protection of vulnerable road users (VRUs). The composite material is obtained by coating carbon fibres with a thermoplastic polymer in a continuous process, followed by infusion with an epoxy resin. The process is scalable for industrial use. The coating process was optimized regarding coating efficiency, energy consumption, risks involved for operating personnel and environment, and tailored to gain the optimal coating thickness obtained from numerical calculations. A drastic decrease in transversal stiffness could be detected for the composite material by dynamic mechanical thermal analysis (DMTA), when the temperature was increased above the glass transition temperature of the thermoplastic interphase. The ability of the material to achieve such temperature and associated reduction in stiffness by the application of current was verified using a special 3-point bending setup developed for this task.

  • 347.
    Backman, A.C.
    et al.
    Luleå tekniska universitet.
    Lindberg, Henrik
    Luleå tekniska universitet.
    Differences in wood material responses for radial and tangential direction as measured by dynamic mechanical thermal analysis2001Inngår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 36, nr 15, s. 3777-3783Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wood is a complex cellular structure with different properties in the radial and tangential direction. Many researchers have measured dynamic properties in the longitudinal direction and a few in the radial direction but very little data can be found in the literature on dynamic mechanical properties in the tangential direction. The purpose of the work presented in this paper was to investigate the dynamic mechanical behaviour in the radial and tangential directions of wood (Pinus sylvestris). Testing was done in tension at 1 Hz with a Dynamic Mechanical Thermal Analyser. Properties in radial and tangential direction were different. The radial direction showed a higher elastic modulus and lower loss factor levels at temperatures between -120°C and 80°C. The tangential direction had on average a higher peak temperature than the radial direction for a loss factor peak around -80°C. It is the opposite of synthetic composites where the stiffer direction has a higher peak temperature. A loss factor peak at around 0°C was seen, most significantly in the tangential direction. This peak has scarcely been reported in the literature before. The distance between annual rings did not significantly affect the dynamic behaviour in the tangential direction.

  • 348.
    Backman, A.C.
    et al.
    Luleå tekniska universitet.
    Lindberg, K.A.H.
    Luleå tekniska universitet.
    Interaction between wood and polyurethane-alkyd lacquer resulting in a decrease in the glass transition temperature2002Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 85, nr 2, s. 595-605Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The long-term properties of paint and glue are of great interest to both manufacturers and users of these materials. If a good bond is achieved, the surface between the wood and the paint or glue will be less susceptible to degradation. Thus, the wood and polymer must be compatible and develop some kind of bonding force between them. A high degree of interaction between wood and commercial polyurethane-alkyd lacquer was shown as a decrease by 10°C of the glass transition temperature (Tg) for the lacquer on wood compared to the pure lacquer. The lacquer also demonstrated good adhesion to wood at a microscale. The interaction was investigated with dynamic mechanical thermal analysis and scanning electron microscopy fractography. The reason for the decrease in Tg is probably because of the lacquer having a higher free volume when applied to the wood, most likely due to it being subjected to tensile forces developed during the drying of the lacquer. Results from investigations of wood impregnated with two different acrylates, a polymethylmethacrylate and a more hydrophilic acrylate, support the suggestion that a decrease in Tg will occur if the polymer adheres to wood, but that poor interaction with little or no adhesion will result in no decrease in Tg. This article also presents results of the dynamic mechanical behavior of Scots Pine in the tangential direction

  • 349.
    Bahrami, Ataallah
    et al.
    Department of Mining Engineering, Urmia University, Urmia, Iran.
    Ghorbani, Yousef
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    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 Flotation2019Inngår i: Mining, metallurgy & exploration, ISSN 2524-3462, Vol. 36, nr 2, s. 409-421Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 350.
    Bahrami, Ataallah
    et al.
    Department of Mining EngineeringUrmia UniversityUrmiaIran.
    Ghorbani, Yousef
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    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 cyclone2018Inngår i: International journal of coal science & technology, ISSN 2095-8293, Vol. 5, nr 3, s. 374-384Artikkel i tidsskrift (Fagfellevurdert)
    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.

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