The main part of this work has been a literature survey, reviewing scientifical reports forinformation on how steel cleanness is evaluated today, and also how the steel cleanness is related tothe fatigue performance of clean steels.

In the present study, magnetite pellets with the additives olivine, calcite and quartzite were isothermally reduced in a tubular furnace to study the interaction between iron oxides and the additives. Exaggerated amounts of additives were used in order to enable analyses of phases that do not otherwise occur in sufficient amounts for X-ray diffraction and EDS-analyses. The reduction was set to yield either magnetite or wüstite in the temperature range 500-1300ºC. For olivine, reduction tests were also performed to allow metallization in the range 1000-1300ºC. The mineralogical phases which had formed were studied after oxidation as well as after reduction. The results showed that it was possible to identify, by X-ray diffraction, the main phases formed by the additives in all samples, after oxidation as well as reduction.In the olivine sample, the forsteritic olivine particles react partly during the oxidation pre-treatment to form magnesioferrite and vitreous silica along the particle corona. This breakdown of the olivine particles during oxidation liberates magnesium from the particles, which do not react until temperatures of above 1150°C in reducing atmosphere. When the hematite in the sample is reduced, and when temperature is high enough to allow solid-state diffusion at ~800ºC, the magnesium of the magnesioferrite redistributes so that the magnesium concentration approaches the same level throughout the structure. For magnetite, this does not occur below 800°C. At 1000°C, this magnesium reacts further with the silica in the glassy slag phase, which crystallizes into fayalitic olivine. At this temperature the magnesium diffuses over distances more than 600µm from the olivine particles. From this point the binding media to resist the swelling tensions in the pellet is mainly solid fayalite. The metallization front concentrates the MgO in the remaining wustite which can lead to MgO levels of up to 10% locally. The melting point of the fayalite is raised from 1145ºC to a melting range of 1238-1264ºC due to the MgO-increase, as estimated based on the phase diagram tuned to the pellets tested. Much of the olivine which remained unaltered in the oxidation process will be encapsulated by iron before the magnesium begin to dissolve in reducing conditions, and therefore play no role in the reduction before final melting of the particles occur.The quartzite particles are not affected by the oxidation pre-treatment. The binding strength of quartzite pellets therefore comes from the sintering of quartzite particles to neighboring hematite as well as the glassy slag resulting from the acid gangue and the bentonite. Substantial reaction of the quartzite particles during reduction did not occur before 1000ºC even though the process has occurred to a very low extent already at 900ºC. Also the glassy slag crystallizes into fayalite in the presence of quartzite. From this point fayalite represents the binding media in the pellet. Pure fayalite melts already at 1177ºC and can at this temperature dissolve up to 76wt% FeO. This leads to early softening, which is one of the main concerns for the softening/melting properties of the pellet. In the pellets with calcite, CaO reacts with Fe2O3 during induration to form a low-melting calcium ferrite slag in the pellet that melts to react with silica in the pellets. If more calcium is added than what is required to react with the silica, calciumferrites becomes part of the binding mass together with the dicalciumsilicate. The calciumferrites forming in pellets with larger additions of calcite are weak to resist the tensions arising due to the low-temperature reduction of hematite and are associated with low temperature disintegration. As the reduction proceeds to wustite, the calcium from the ferrite dissolves in the wustite so that porous calciumwustite forms. The dicalciumsilicate remain stable during the entire reduction until reaction and melting of the phase begin at 1283ºC. / Godkänd; 2013; 20130411 (parsem); Tillkännagivande disputation 2013-05-20 Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Pär Semberg Ämne: Processmetallurgi/Process Metallurgy Avhandling: Interactions Between Iron Oxides and the Additives Olivine, Quartzite and Calcite in Magnetite Pellets Opponent: Professor Abdel-Hady Abdel-Hady El-Geassy, CMRDI, Cairo, Egypt Ordförande: Professor Bo Björkman, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Måndag den 10 juni 2013, kl 10.00 Plats: F531, Luleå tekniska universitet

Coal is the single largest fossil fuel used world-wide and accounts for more than 60% of the total commercial energy consumed. Between 60 to 80% of this coal is used for electric power generation and most of which through a system of pulverised coal combustion. Major portion of the coal used for such power generation is not clean enough to maintain environmental standards. This problem is attributed to high sulphur content in coal used in most of the western countries or ash as is the case in countries like India. In India at present nearly 200 million tonnes per year of coal is used for power generation and the average ash in coals used is invariably above 40%. A substantial portion of ash is liberated as it enters the boiler from the mill. It is crucial to reduce the amount of ash going from the mill to the boilers not only to improve the performance of power generation and increase the life of the boilers but also became mandatory due to environmental regulations. Thus the main objective of the work is to develop a dry tribo-electrostatic process for the separation of ash forming inorganic matter from coal material with a thorough understanding of the response and behaviour of coal and non-coal matters to contact electrification and in electric field. This work is financially supported by the Department for Research Cooperation of the Swedish International Development Cooperation Agency (SIDA). The literature on dry coal preparation processes has been reviewed and the advantages of triboelectric process compared to other processes have been highlighted and further research needs to make it a viable industrial technology are outlined. Three Indian coal samples from three different major coal fields, i.e., Ramagundam, Ib-valley and Talcher, have been collected and characterised for macerals and mineral composition by microscopic and XRD analyses. The beneficiation potential at different size fractions of the coal samples is judged by the washability studies. The charge polarity and magnitude of pure quartz, kaolinite, illite and carbon after contact electrification with different tribo-charging media have been measured by Faraday cup method using Keithley electrometer. The predicted work functions of the tribo charging material and mineral phases agree closely with the reported values. The electron accepting and donating (acid-base) property of mineral phases determined by Krüss Tensiometer through polar and non-polar liquid contact angles on solids also corroborated the acquired charge polarity in contact electrification with copper, aluminium and brass materials underlying their work functions. This methodology is being applied for the choice of organic acidic/basic solvents treatment of coal material to enlarge the difference in work functions between the tribo-charger and mineral phases, and to achieve greater separation efficiency of inorganic matter from coal. The coal samples have been tested for the separation between coal and non-coal matters in a laboratory in-house built tribo electric separator and the influence of equipment and process variables have been evaluated. The results showed that the ash content was reduced from 45% to about 18%, and a clean coal product as judged by the washability studies can be obtained. / Godkänd; 2006; 20070110 (haneit)

Slag is a vital part of metal production since it removes impurities from the metal. As slag is continuously produced, the options are either to dispose slag in landfill or acknowledge slag as a product. Slag can be used in many different applications, ranging from fertilizer to construction material; in some cases, the properties of slag make it a superior alternative to virgin stone materials. The properties and thereby the field of application is determined by the mineralogical composition of the slag. Slag is considered an environmentally friendly material as long as the leaching of certain elements stay below specified thresholds, for leaching of chromium the limit is at 0.5 mg/kg for slag to be considered inert material. The most common leaching approach is to compare leaching analyses from slag samples to deduce which elements and/or phases contribute or prevent leaching of specific elements. With this method each slag need to be investigated separately and the result may only apply for that specific slag type. In this thesis the approach is different: individual minerals are synthesized and dissolved separately at various pH to accurately assess their dissolution capabilities. By studying the dissolution of individual minerals the leaching of any type of slag with known mineralogical composition can be anticipated. Slag leaching can then be tailored, for example, chromium leaching can be eliminated if all chromium containing phases are removed or not capable of dissolving. In this thesis the dissolution of akermanite, β- and γ-dicalciumsilicate, merwinte, monticellite, pseudowollastonite and magnesiowüstite with varying FeO/MgO ratios are studied. Leaching tests of magnesiowüstite with 4 wt% Cr2O3 were also included. The dissolution of each mineral is calculated by the acid addition required to maintain a constant pH with 50 mg of mineral in 100 ml water. As expected, the dissolution decreases as pH increases, with exception of the dicalcium silicates which dissolved completely at pH 4 to 10. The dissolution of the minerals is largely connected to the elemental composition. In the silica based minerals a high Ca ratio promotes dissolution while a high Si ratio impedes the dissolution rate. Both dissolution and chromium leaching of magnesiowüstite depends on the FeO content, with increasing FeO content the dissolution and leaching decreases, magnesiowüstite with at least 60 wt% FeO does not dissolve at pH 10. None of the magnesiowüstite compositions were close to the chromium leaching limit of inert material, 0.5 mg/kg, as the highest leaching sample, with 52 wt% FeO, leached 0.069 mg/kg.

No description available.

This thesis focuses on the analytical properties of the acoustic vibrations and applications of metallic nanoparticles. With regard to the analytical properties of the acoustic vibrations, we focus on nanoparticle acoustic resonance enhanced four-wave mixing (FWM) as an in situ characterization technique for characterizing nanoparticles’ shape, size, and size distribution. The nonlinear optical response of metallic nanoparticles is resonantly driven by the electrostriction force which couples to the acoustic vibrations of nanoparticles. Information about nanoparticles’ shape, size, and size distribution can be obtained by analyzing the resonant peak position and linewidth in the FWM signal which carries the information about the vibrational modes. We characterize different nanoparticle solutions of different materials, shapes, and sizes using this FWM technique. Information obtained from the FWM characterization agrees well with the scanning electron microscopic examination, indicating the FWM technique can serve as an in situ nanoparticle characterization tool. We also demonstrate the FWM technique can be used for monitoring nanoparticle growth in situ. iii With regard to the applications of metallic nanoparticles, we focus on quantification of an exogenous cancer biomarker Acetyl Amantadine using surface-enhanced Raman scattering (SERS). Raman spectroscopy can provide unique fingerprint information of molecules, which can be used as a chemical detection and identification technique. The intrinsically weak Raman signal caused by the small scattering cross section presents a barrier for trace chemical detection. Localized surface plasmon resonance of metallic nanoparticles can provide large local field enhancement, which can be utilized to enhance the intrinsically weak Raman signal. In order to achieve higher local field enhancement, we focus on using the gap structures formed between nanoparticles instead of using discrete nanoparticles. Molecules should locate within the hot spots of the gap structures to experience the largest enhancement. This requires that molecules should be extracted from volume onto the metallic surface. Based on these guidelines, two SERS platforms are designed using gold nanoparticles (nanorods and nanospheres) combined with different surface functionalization techniques. The performance of these two platforms are characterized by investigating the sensitivity and limit of detection (LOD). 16 ng/mL and 0.4 ng/mL LODs are achieved for nanorod and nanosphere platforms, respectively. / Graduate

M.Tech. / The mining industry exerts ever increasing demand for components with high wear resistance to the extent that plain ferrous alloys are falling short. Innovative metal-matrix composites nonferrous metals have been widely researched and used. Casting composites based on ferrous alloys pose monumental challenges in casting. Firstly, the density differential results in large resistant forces on the ceramic such that unless a rigid structure is configured, the less dense ceramic floats on the metal stream. Secondly, the poor wetting properties between metal and ceramic will result in inferior bonding of the matrix, hence separation of solids in service.This study presents the feasibility of manufacturing ceramic based metal matrix composites (MMC) for multi-purpose industrial application including wettability and the bonding between the matrix and the composite. The cold rods of alumina positioned in the mould prior to casting cracked as soon as they came in contact with hot metal. Because of the density difference between ceramic and liquid metal the alumina tended to float under the influence of Ferro static pressure. Infiltration of zirconia (ZrO2) and alumina (Al2O3) in ferrous matrix was investigated. Infiltration of liquid metal in ceramic filters increased with porosity of filters i.e. greater infiltration occurred in filters with larger pore volume fraction measured in terms of number of pores per linear inch (ppi). Thus, there was high infiltration in casting with 10ppi followed by 30ppi and there was poor infiltration in 50ppi ceramics. Infiltration increased with increasing temperature of the ceramics. A temperature of 1000oC was found to be superior to 800oC. The wetting behaviour of molten iron on the substrates of Al2O3 was investigated. Titanium in high chromium white cast iron was found to improve the wetting characteristics on alumina. The wetting angle decreased with increased titanium content. The wear properties of ferrous alloys used were not significantly improved by the ceramic used to make the composite. Filters are produced by a deposition process and hence are not densified for the purpose of manufacturing hard composites

The performance of a growing sulphate reducing bacteria consortium for Sr2+, Co2+ and Cs+ removal from solution in a batch sulphidogenic bioreactor was investigated. Metal removal by the growing bacterial consortium, and microbial culture growth and metabolic activities (biological sulphate removal) were continuously monitored in the bioreactors over the duration of the treatment period. On the other hand, diversity changes within the bacterial consortium before and after bioreactor operation (28 days) were performed using the partial 16S rRNA fingerprinting method. In the original bacterial consortium, Enterococcus and Staphylococcus sp. were the dominant bacterial species. However, the presence of Sr2+, Co2+ and Cs+ in the growth media, resulted in the emergence of new bacterial species belonging to the Citrobacter, Paenibacillus, and Enterococcus and Stenotrophomonas genera, respectively. The Citrobacter and Paenibacillus sp. demonstrated high tolerance towards the presence of the divalent cations, Sr2+ and Co2+, respectively, while the Enterococcus and Stenotrophomonas sp., demonstrated Cs+ high tolerance. The bacterial growth and sulphate removal rate were significantly decreased at initial metal ion concentrations ≥100 mg/L. The toxicity and inhibitory effects of the metals on the present SRB consortium was observed in the order Sr>Co>Cs. The metal uptake capacity (qτ) of the bacterial consortium decreased with increasing initial metal concentration, and complete Sr2+, Co2+ and Cs+ removal was observed at initial metal concentrations ≤75 mg/L. Overall, the present SRB consortium demonstrated a superior Sr2+ removal capacity (qmax= 405 mg/g), and the least for Cs2+, where qmax = 192 mg/g. The present SRB culture exhibited a superior Sr+ and Cs+ binding capacity, compared to other studies in literature. Results from Sr2+, Co2+ and Cs+ biosorption kinetics indicate that initial concentration and solution pH played a vital role in determining the rate of metal removal kinetics. The experimental data was successfully analysed by the pseudo-second-order rate model, demonstrating that chemisorption is the main rate limiting step for the removal of Sr2+, Co2+ and Cs+ from solution. In this study, the adsorption behaviour of protons and of Sr2+, Co2+ and Cs+ onto the bacterial consortium cell surfaces was evaluated under anaerobic conditions as a function of pH (4-10), ionic strength (0.01, 0.05, 0.1M) and temperature (25, 50 and 75°C). Acid-base titrations of the bacterial suspension indicated that the titration data could be adequately described by a four site non-electrostatic model, with pKa values of 4.41, 6.69, 8.10 and 10. The Sr2+, Co2+ and Cs+ adsorption data could be fitted with a two site non-electrostatic model, involving the type 1 and 2 sites (carboxylic and phosphoryl sites). Increasing the ionic strength had a negative effect on the adsorption of metal ions from solution. There was no observed temperature dependence on the adsorption of Co2+ and Cs+ from solution. In summary, results obtained in this study have shown that the processes involved in microbial Sr2+, Co2+ and Cs+ removal from contaminated sources is a direct function of the microbial characteristics and efficiency, mass transfer and surface complexation effects under varying environmental conditions. One important goal to be achieved in future studies will be the determination of the intrinsic stability constants and the structure of the formed metal complexes species. These constants can be used directly in risk assessment programs. / Thesis (PhD(Eng))--University of Pretoria, 2011. / Chemical Engineering / unrestricted

The first objective of the thesis was to reveal the characteristic magnetic behaviour of natural weakly magnetic minerals (such as hematite and chromite), and the size limits of the particles recoverable by the existing modem high intensity and high gradient magnetic separators. The second objective was to enhance the particle aggregation andlor the magnetic response for wet magnetic concentration of the ultrafines which escaped from the separators. It was observed that weakly magnetic natural minerals (hematite and chromite) exhibited variations in the magnetic behaviour with respect to magnetizing field, temperature and even particle size, It was indicated that high gradient magnetic separation with industrial matrices was efficient for weakly magnetic minerals as small as 10 um, but below this size, poor separation efficiency was obtained. In this thesis, modifications to the existing magnetic technology or alternative methods were investigated for the efficient recovery of particles below 10 gm. The technology or methods included "carrier" or "piggy-back" method, aggregation with magnetic bonding (with permanent or fieldinduced magnetic moment), and hydrophobic magnetite seeding. The thesis discusses the theoretical aspects of the problem and the experimental work. It was clearly demonstrated that wet magnetic concentration was more efficient for the ultrafine fractions whereas other methods could be used to increase the effective particle size dimensions andlor the magnetic susceptibilities. / Godkänd; 1993; 20070426 (ysko)

A comparative study on bioleaching of a pyrite concentrate using ten different industrial oxidic by-products as neutralising agent has been performed with a commercial grade slaked lime chemical serving as reference material. The acid produced during oxidation of pyrite was neutralised by regular additions of neutralising agent whenever needed to maintain a pH of 1.5. Bioleaching was conducted as batch experiments in 1-L scale reactors, with a mixed mesophilic culture at a temperature of 35º C. The different industrial oxidic by-products used were steel slag, ashes, dust and lime sludge. The aim of the study was to investigate the possibility to replace normally used lime or limestone with oxidic by-products, considering their neutralising capacities and possible negative impact on the bacterial activity. The bioleaching efficiency was found to be equally good or better, when by-products were used for neutralisation instead of slaked lime, and the bioleaching yields of pyrite were in the range 69-80%, except the Waste ash, which had a leaching yield of 59%. Some of the by-products used contained potentially toxic elements for the bacteria, like fluoride, chromium and vanadium, but no negative effect of these elements could be observed on the bacterial activity. The Waste ash contained a large number potentially toxic elements and a high chloride concentration of 11%, which had a negative effect as observed on the lower redox potential and leaching yield. Slags originating from stainless steel production should be avoided for environmental reasons, due to the presence of chromium. The electric arc furnace (EAF) dust has a good potential to be used as neutralising agent in bioleaching processes for zinc recovery from zinc sulphides, due to the high content of zinc, however the chlorides present should be removed prior to its use. The neutralising capacity, as determined by the amount needed for neutralisation during bioleaching, were rather high for all the steel slags, EAF dust, Bioash and Mesalime with a range of 16-37 g as compared with 22 g needed for slaked lime. However, Waste ash and Coal & Tyres ash had lower neutralising capacities with 81 g and 57 g needed, respectively. Hence, it is concluded that considerable savings in operational costs can be obtained by replacement of lime or limestone with steel slag, ash, dust or sludge without negative impact on bioleaching efficiency. Use of industrial oxidic by-products would provide opportunities to recycle elements present in them as for example zinc rendering an eco-friendly process and a means for sustainable use of natural resources. / Godkänd; 2008; 20080519 (ysko)