Dissertations / Theses: 'Metallurgical and Materials Science'

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Jenkins, Neil Travis 1973. "Chemistry of airborne particles from metallurgical processing." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/17033.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2003.
Vita.
Includes bibliographical references.
Airborne particles fall into one of three size ranges. The nucleation range consists of nanoparticles created from vapor atom collisions. The decisive parameter for particle size and composition is the supercooling of the vapor. The accumulation range, which comprises particles less than 2 micrometers, consists of particles formed from the collision of smaller primary particles from the nucleation range. The composition of agglomerates and coalesced particles is the same as the bulk vapor composition. Coarse particles, the composition of which is determined by a liquid precursor, are greater than 1 micrometer and solidify from droplets whose sizes are controlled by surface, viscous, and inertial forces. The relationship between size and composition of airborne particles could be seen in welding fume, a typical metallurgical aerosol. This analysis was performed with a cascade impactor and energy dispersive spectrometry with both scanning electron microscopy (SEM-EDS) and scanning transmission electron microscopy (STEM-EDS). Other methods for properly characterizing particles were discussed. In the analysis, less than 10% of the mass of fume particles for various types of gas metal arc welding (GMAW) were coarse, while one-third of flux cored arc welding (FCAW) fume particles were coarse. Coarse particles had a composition closer to that of the welding electrode than did fine particles. Primary particles were not homogeneous. Particles larger than the mean free path of the carrier gas had the same composition as that of the vapor, but for particles 20 to 60 nanometers, smaller particles were more enriched in volatile metals than larger particles were. This was explained by the cooling path along the bubble point line of a binary phase diagram.
(cont.) Particles were not necessarily homogenous internally. Because nanoparticles homogenize quickly, they may form in a metastable state, but will not remain in that state. In this analysis, the presence of multiple stable immiscible phases explains this internal heterogeneity. The knowledge contained herein is important for industries that depend on the properties of nanoparticles, and for manufacturing, where industrial hygiene is important because of respirable particle by-products, such as high-energy-density metallurgical processing.
by Neil Travis Jenkins.
Ph.D.

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2

King, Matthew Joseph. "Control and optimization of metallurgical sulfuric acid plants." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/284812.

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The pyrometallurgical processing of copper concentrates produces SO₂-bearing offgas. SO₂ in the offgas is catalytically oxidized to SO₃ and absorbed into a ∼98.5% H₂SO₄-H₂O mixture in a sulfuric acid plant. This research provides an analysis of a copper smelter sulfuric acid plant and discusses the control and optimization necessary to attain the following goals: (a) minimize smelter SO₂ emissions; (b) maximize acid plant capacity and availability. The objectives of this work are to: (a) prepare mathematical descriptions of sulfuric acid plant operations; compare the mathematical predictions with plant data; (c) use the mathematical descriptions to: (i) predict acid plant behavior with varying feed SO₂ strengths and gas flow rates; (ii) determine control strategies to minimize smelter SO₂ emissions; (iii) evaluate requirements for an existing acid plant to accommodate future increased feed gas flows and SO₂ strengths.

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Bernardis, Sarah. "Engineering impurity behavior on the micron-scale in metallurgical-grade silicon production." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/101457.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2012.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 127-137).
Impurities are detrimental to silicon-based solar cells. A deeper understanding of their evolution, microscopic distributions, and oxidation states throughout the refining processes may enable the discovery of novel refining techniques. Using synchrotron-based microprobe techniques and bulk chemical analyses, we investigate Fe, Ti, and Ca starting from silicon- and carbon bearing raw feedstock materials to metallurgical grade silicon (MG-Si), via carbothermic reduction. Before reduction, impurities are present in distinct micron- or sub-micron-sized minerals, frequently located at structural defects in Si-bearing compounds. Chemical states vary, they are generally oxidized (e.g., Fe²+, Fe³+). Impurity concentrations are directly correlated to the geological type of quartz: pegmatitic and hydrothermal quartz have fewer impurities than quartzite. Particles containing Cr, Mn, Fe, Ni, Cu, K, and/or Zn are also detected. In carbon-bearing compounds, Ca typically follows wood veins. In wood, Fe and Ti are diffused uniformly. In contrast, charcoal samples can contain particles of Fe, Ti, and/or Ca. The overall impurity content in the pine charcoal sample is higher than in the pine woodchip, suggesting that the charcoalization process introduces unintentional contamination. During reduction, silica evolution is analyzed in parallel to Fe. Fe is predominantly clustered in minerals which influence its oxidation state. Here, Fe is embedded in muscovite with predominance of Fe℗đ+. Initially, Fe is affected by the decomposition of muscovite and it is found as Fe²+; as muscovite disappears, Fe diffuses in the molten silica, segregating towards interfaces. Contrary to thermodynamic expectation, Fe is oxidized until late in the reduction process as the silica melt protects it from gases present in the furnace, hence minimizing its reduction, only partially measured at high temperatures. After reduction, the initial low- to sub- ppmw concentrations measured in the precursor quartz increase drastically in the MG-Si. The refining process is responsible for the increased contamination. Yet, most impurities are clustered at grain boundaries and a leaching process could remove them. Electrical fragmentation and a leaching treatment are tested as a method to expose grain boundaries of "dirty" quartzite and to remove impurities. The selective fragmentation proves to be a very important step in removing impurities via leaching.
by Sarah Bernardis.
Ph. D.

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Papakirillou, Ismini. "A metallurgical study of West African iron monies from Cameroon and Liberia." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55263.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 200-202).
The aim of this thesis is to make a contribution to the study of West African iron monies through examination and analysis of a group of these objects in the collection of the Peabody Museum of Archaeology and Ethnology at Harvard University. The selection of objects from the collection includes five distinct types, representing different sizes and shapes that have been identified as monies/exchange mediums. All of these object types were originally part of a bundle or remain in bundled form; all share a provenience in West Africa, four groups in present day Cameroon and one in Liberia. The research corpus of material has dates ranging from the late nineteenth to the early twentieth century. My metallurgical studies of West African iron monies are the first such investigations to have been carried out. The results will contribute to the appreciation of the ways in which iron 'monies' functioned within late nineteenth - early twentieth century West African societies.
by Ismini Papakirillou.
S.M.

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Cooney, Elizabeth Myers. "Bronze metallurgy in Iron Age central Europe : a metallurgical study of Early Iron Age bronzes from Stična, Slovenia." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39480.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (v. 2, p. 375-377).
The Early Iron Age (750-450 BCE) marks a time in the European Alpine Region in which cultural ideologies surrounding bronze objects and bronze production were changing. Iron was becoming the preferred material from which to make many utilitarian objects such as weapons and agricultural tools; this change can be clearly seen in the different treatments of bronze object deposits from the Late Bronze Age to the Early Iron Age. The Early Iron Age hillfort settlement of Sticna in what is now southeastern Slovenia was one of the first incipient commercial centers to take advantage of the new importance placed on iron, conducting trade with Italy, Greece, the Balkans, and northern Europe. This metallurgical study of bronze funerary objects from Sticna identifies construction techniques, use patterns, and bronze metallurgical technologies from the ancient region of Lower Carniola. This information is then used to explore the cultural importance of bronze at Early Iron Age Sticna and to compare the bronze work of Lower Carniola with that of other regions in central Europe and Italy from this time of great change in Iron Age Europe.
S.M.

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Payton, Eric John. "Characterization and Modeling of Grain Coarsening in Powder Metallurgical Nickel-Based Superalloys." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250265477.

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Jönsson, Martin. "The Atmospheric Corrosion of Magnesium Alloys : Influence of Microstructure and Environments." Doctoral thesis, KTH, Kemi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4545.

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The low density and high specific strength of magnesium alloys have created a great deal of interest in the use of these alloys in the automotive and aerospace industries and in portable electronics. All of these industries deal with applications in which weight is extremely important. However, an obstacle to overcome when using magnesium alloys in engineering applications are their unsatisfactory corrosion properties. This thesis is devoted to the atmospheric corrosion of the two magnesium alloys AZ91D and AM50, in particular the ways the microstructure and exposure parameters of these alloys influence their corrosion behaviour. The work includes both laboratory and field studies. The results obtained show that the microstructure is of vital importance for the corrosion behaviour under atmospheric conditions. The microstructure of magnesium-aluminium alloys contains different intermetallic phases, e.g. Al8Mn5 and β-Mg17Al12. The local nobility of these intermetallic phases was measured on a submicron level in an atmospheric environment. It was shown that particles of the Al-Mn type exhibit the highest Volta potential among the microstructure constituents of the AZ91D magnesium alloy. Further, it was shown that the Volta potential was highly dependent on the aluminium content of the magnesiumaluminium phases in the surface layer. When thin electrolyte layers are present, CO2 diffuses readily to the surface forming magnesium carbonate, hydromagnesite. The CO2 lowers the pH in areas on the surface that are alkaline due to the cathodic reaction. This stabilises the aluminium-containing surface film, the result being increased corrosion protection of phases rich in aluminium. Both in the laboratory and under field conditions the corrosion attack was initiated in large α-phase grains, which is explained by the lower aluminium content in these grains. The thin electrolyte film, which is formed under atmospheric conditions, decreases the possibility of galvanic coupling of alloy constituents located at larger distances from each other. Thus the cathodic process is in most cases located in the eutectic α-/β phase close to the α-phases, instead of in intermetallic Al-Mn particles, even though the driving force for the initiation of the corrosion attack in Al-Mn particles should be high, due to their high nobility.

QC 20100802

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Duffey, Matthew James. "Metallurgical Characterization and Weldability Evaluation of Ferritic and Austenitic Welds in Armored Steels." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1460910681.

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Boster, Connor M. Boster. "Metallurgical Characterization and Testing of Dissimilar Metal Welds for Service in Hydrogen Containing Environments." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524179509481363.

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10

Semykina, Anna. "Recovery of iron and manganese values from metallurgical slags by the oxidation route." Doctoral thesis, KTH, Materialens processvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-24534.

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In the modern practice, a sustainable development strategy in a domain of wasteutilization is shifting its focus from a general completeness of recycling to a morespecific attention to efficiently utilize elements in the wastes. This is well-illustrated bythe steelmaking slag industries. The major waste product from the steelmaking practiceis slag and its main constituents are: CaO, SiO2, Al2O3, MnO, FeO and so on. The mainfield of application for the steelmaking slags is civil engineering, especially for road andwaterway construction. However, a significant amount of the slag remains in the dumps,damaging the environment as well as requiring a land for secure storage. Efficientrecycling of these materials is of increasing interest worldwide as a result of increasingsustainability in processes with respect to increasing raw material costs and wastereduction.In order to find a practical solution, joint efforts are currently made at the RoyalInstitute of Technology, Sweden and National Metallurgical Academy of Ukraine. Theconcept is based on transformation of non-magnetic wüstite (FeO) to magneticmagnetite (Fe3O4) using an oxidizing atmosphere was proposed.In order to verify the feasibility of the proposed way of slag utilization, experiments onthe ternary CaO-FeO-SiO2 and quaternary CaO-FeO-SiO2-MnO slags systems,accompanied by thermodynamic and kinetic modelling, were performed. The crystalprecipitation during synthetic slag oxidation was observed by Confocal Scanning LaserMicroscopy (CSLM). Precipitated phases were found to be magnetite and manganeseferrite in the spinel form.Obtained magnetite and manganese ferrite can be separated from the slag by magneticseparation.The formation of nanosize manganese ferrite from the CaO-FeO-SiO2-MnO slag systemduring oxidation was investigated. Experiments were conducted in a horizontalresistance furnace in an oxidizing atmosphere (air). The final product was analysed by Xraydiffraction (XRD). The particles size of the manganese ferrite was estimated by theScherrer formula and was found to be of the order of 23-25 nm. In order to get anunderstanding of the magnetic properties of the manganese ferrite recovered from slagtreatment, it was necessary to synthesize a reference compound from pure precursors.The MnFe2O4 nanopowder was synthesized by the oxalate route. The size effects on themagnetic properties of manganese ferrite particles were investigated.IIThe potential way of the magnetite particles separation from liquid slags was investigatedby cold model studies. The experimental technique of mobilising non-conducting,nonmagnetic particles in conducting liquid in crossed electric and magnetic fields wasinvestigated in order to find the way of the particle separation from the liquidsteelmaking slags. The effects of the current density, magnetic field, size and shape ofthe particle on the particle velocity under action of the electromagnetic buoyancy force(EBF) in the electrolyte were analyzed.
QC 20100916

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Muwanguzi, Abraham Judah Bumalirivu. "Characterisation of Muko iron ores (Uganda( for defferent routes of iron production." Licentiate thesis, KTH, Materialvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-25037.

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Iron and its products, especially the various forms of steel, have been and still are a vital material in many sectors of life. It is utilized in many industrial activities ranging from production of heavy duty mechanical equipment to light electrical appliances and home appliances. With the world‟s iron ore consumption estimated to stand at 1.3 billion tonnes by 2025, exploitation of any existing natural deposits is of increasing importance to meet the demands of the expanding world economy. Large deposits of iron ore exist in Uganda in the eastern (Tororo) regions and south-western (Kisoro-Kabale) regions of the country. The ore deposits of Kisoro-Kabale consist of an iron-rich hematite grade with less deleterious impurities as compared to that of Tororo. Prospective quantification puts the deposits at 30-50 million tonnes of raw-ore reserves. To date the deposits lay unexploited, with small holder black smith activities taking place in the area. This work involves understanding the occurrence, quantity and quality of the ore plus its properties and characteristics in a bid to pave way for its exploitation for economic use in Uganda and beyond. Characterisation was done on the samples collected from the deposits, to establish its physical, chemical and metallurgical properties. Literature detailing the natural occurrence of the deposits plus the genesis of the parent rocks and ore and the prospective tonnage is included. The economic situation in Uganda as far as demand and consumption of iron and steel is concerned is also briefly highlighted. The chemical, physical and metallurgical characteristics that could facilitate the initial exploitation of the ore are examined with conclusive results from the representative samples examined. The results present Muko ore as a high grade of hematite with an Fe content averaging 68%. The gangue content (SiO 2+Al2O3) of 5 of the 6 samples investigated is < 4%, which is within the tolerable limits for the dominant iron production processes, with its S and P contents being < 0.1% and 0.07% respectively. Thus, Muko iron ore can be reduced in the furnace without presenting major difficulties. With respect to mechanical properties, Muko ore was found to have a Tumble Index value > 85 wt%, an Abrasion Index value < 4 wt% and a Shatter Index value < 2.5 wt%. This implies that the ore holds its form during the processes of mining, transportation, screening and descent when loaded in the furnace for reduction. Its reducibility index was found to be 0.868%/min. This is well within the desired reduction limits for the major iron reduction processes. It implies that a high productivity (in terms of iron reduced) can be realised in the reduction processes in a given period of time. Muko iron ore was found to meet most of the feed raw material requirements (physical, chemical and metallurgical) for the blast furnace and the major direct reduction processes (Midrex, HYL III and SL/RN). Furthermore, for those desired for sinter and pellet making. It can thus serve well as a feed raw material for smelting reduction and direct reduction processes.
QC 20101007
Sustainable Technological Development in the Lake Victoria Region

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Zhang, Zhi. "A study of flow fields during filling of a sampler." Licentiate thesis, KTH, Materials Science and Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10693.

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More and more attention has been paid to decreasing the number and size of non-metallic inclusions existing in the final products recently in steel industries. Therefore, more efforts have been made to monitor the inclusions' size distributions during the metallurgy process, especially at the secondary steelmaking period. A liquid sampling procedure is one of the commonly applied methods that monitoring the inclusion size distribution in ladles, for example, during the secondary steelmaking. Here, a crucial point is that the steel sampler should be filled and solidified without changing the inclusion characteristics that exist at steel making temperatures. In order to preserve the original size and distributions in the extracted samples, it is important to avoid their collisions and coagulations inside samplers during filling. Therefore, one of the first steps to investigate is the flow pattern inside samplers during filling in order to obtain a more in-depth knowledge of the sampling process to make sure that the influence is minimized.

The main objective of this work is to fundamentally study the above mentioned sampler filling process. A production sampler employed in the industries has been scaled-up according to the similarity of Froude Number in the experimental study. A Particle Image Velocimetry (PIV) was used to capture the flow field and calculate the velocity vectors during the entire experiment. Also, a mathematical model has been developed to have an in-depth investigate of the flow pattern in side the sampler during its filling. Two different turbulence models were applied in the numerical study, the realizable k-ε model and Wilcox k-ω model. The predictions were compared to experimental results obtained by the PIV measurements. Furthermore, it was illustrated that there is a fairly good agreement between the measurements obtained by PIV and calculations predicted by the Wilcox k-ω model. Thus, it is concluded that the Wilcox k-ω model can be used in the future to predict the filling of steel samplers.

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Kero, Ida. "Ti3SiC2 synthesis by powder metallurgical methods." Licentiate thesis, Luleå tekniska universitet, Materialvetenskap, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17858.

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The MAX phases constitute a group of ternary ceramics which has received intense attention over the last decade due to their unique combination of properties. The Ti3SiC2 is the most well studied MAX phase to date and it has turned out to be a promising candidate for high temperature applications. It is oxidation resistant, refractory and not susceptible to thermal shock, while at the same time it can be machined with conventional tools which is of great technological importance. Most attempts to synthesize bulk Ti3SiC2 have involved pure titanium in the starting powder mixtures, but Ti powder is oxidising and requires an inert atmosphere throughout the synthesis process which makes the procedures unsuitable for large scale production. The aim of the first part of this study was to delineate the influence of sintering time and temperature on the formation of Ti3SiC2 from a starting powder which does not contain pure titanium. Titanium silicon carbide MAX phase was synthesised from ball milled TiC/Si powders, sintered under vacuum for different times and temperatures. After heat treatment the samples were evaluated using scanning electron microscopy (SEM) and x-ray diffraction (XRD). This study showed that TiC was always present in the final products whereas TiSi2 was an intermediate phase to the Ti3SiC2 formation. The highest amount of Ti3SiC2 was achieved for short holding times of 2-4 hours, at high temperatures, 1350-1400¢ªC. More elevated temperatures or extended times resulted in silicon loss and decomposition of Ti3SiC2. In the second part of this study the sintering reactions and the mechanisms of formation of Ti3SiC2 were investigated by x-ray diffractometry, thermodilatometry, thermogravimetry, differential scanning calorimetry and mass spectrometry. TiC/Si powders of the different ratios; 3:2 and 3:2.2, were heated to different temperatures under flowing argon gas in a dilatometer and examined by XRD. The TiC/Si powder samples of the ratio 3:2 were further investigated by the other thermal analysis methods. The results confirmed the presence of the intermediate phase TiSi2. From 1500¢ªC silicon evaporation and MAX phase decomposition were observed, and the results show that the MAX phase formation may be concurrent with the melting of silicon. TiC was always present in the final products, either as a reactant or as a decomposition product. The extra silicon of the 3:2.2 TiC/Si powder significantly increased the Ti3SiC2 conversion and no intermediate phases were observed for this powder mixture. The Si of these samples did not melt or evaporate, and only minor decomposition was observed even at 1700¢ªC. These results indicate that the silicon content of the initial powder mixture is decisive to the reaction mechanisms of the sintering process.

Godkänd; 2007; 20070523 (ysko)

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Wang, Haijuan. "Investigations on the Oxidation of Iron-chromium and Iron-vanadium Molten Alloys." Doctoral thesis, KTH, Materialens processvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12955.

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With the progress of high alloy steelmaking processes, it is essential to minimize the loss of valuable metals, like chromium and vanadium during the decarburization process, from both economic as well as environmental view points. One unique technique to realize this aim, used in the present work, is the decarburization of high alloy steel grades using oxygen with CO2 in order to reduce the partial pressure of oxygen. In the present work, the investigation on the oxidation of iron-chromium and iron-vanadium molten alloys under CO2-O2 mixtures was carried out and presented in this dissertation. For oxidation study on Fe-Cr molten alloy with CO2-O2 mixtures, on the basis of thermodynamic analysis, energy balance calculation and modeling results, experimental validation in laboratory was carried out, and later on, the oxidation kinetics of Fe-Cr and Fe-Cr-C melts under controlled partial pressure of oxygen was investigated. Thermodynamics calculation and energy balance estimation demonstrated that, it is possible to use CO2 or CO2-O2 mixtures as decarburizers during EAF process and high initial carbon contents in the steel can be adopted at the beginning in order to reduce the cost. A generic model has been developed to describe the overall process kinetics prevailing in metallurgical reactors containing liquid metal and gas bubbles. This model is general and can be extended further to consider any gas liquid reactions in any chemical engineering reactor, and especially the metallurgical ones, like AOD. In the present dissertation, the model is applied in predicting the evolution of Cr and C contents in a Fe-C-Cr melt during injection of different O2-CO2 mixtures. The related simulation results illustrated that CO2 is efficient in Cr retention. In order to verify the modeling results, 1kg induction furnace experiments were carried out in the present laboratory. The results indicated that the predictions of the model are in good agreement with the experimental results. Meanwhile, the experimental results indicated that the Cr-losses can be significantly lowered by replacing the oxygen with CO2 in the injected gas, specifically for Fe-Cr-C melts with carbon levels higher than about 0.8 mass%. Subsequently, the oxidation kinetics of Fe-Cr and Fe-Cr-C melts was investigated under different CO2-O2 mixtures. It is indicated that, the oxidation rate is controlled by the chemical reaction at the initial stage and the reaction rate can be expressed as at the Cr range of 11-21 mass% in the Fe-Cr melt. For oxidation study on Fe-V liquid alloy, the investigation of the oxidation kinetics was carried out under CO2-O2 mixtures, which is followed by the study on thermodynamic properties of vanadium containing slags. During oxidation of Fe-V melt, in the case of alloys with vanadium contents exceeding 10 mass%, there exists an incubation period before the chemical reactions prevail the process. In addition, the ‘incubation time’ increased with the increase of temperature and the vanadium content, whereas it decreased with the increase of oxygen partial pressure in the oxidant gas. High-temperature mass spectrometric method was used to determine the activity of the vanadium oxide in CaO-MgO-Al2O3-SiO2-V2O3 slags, whereas, the oxidation states of vanadium in the CaO-MgO-Al2O3-SiO2-VOxslag system was studied by XANES method. The results indicated that, higher basicities stabilize higher vanadium oxidation state, whereas, higher temperature stabilizes lower vanadium oxidation state. The present work, which was carried out within the ECO-STEELMAKING project funded by MISTRA via Jernkontoret is expected to lead to implementation of some modifications in high alloy steel production based on fundamental concepts towards more environment-friendly steel processing.

QC20100628

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Donald, Jeffrey Richard. "Surface interactions between non-ferrous metallurgical slags and various refractory materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ27913.pdf.

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Rigual, David Andrés. "Metallurgical characterization of self catalytic structural materials for sulfuric acid decomposition." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34654.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2005.
Includes bibliographical references (p. 276-279).
Eight heats of material with base alloy chemistries of Alloys 800 HT or 617 with platinum additions of 2, 5, 15, or 30 wt% have been characterized according to their microstructural features. The goals of characterization were to determine metallurgical stability for service as self-catalytic structural materials. The results presented herein will be useful to the development of a material for the construction of a heat exchanger designed for sulfuric acid decomposition. This type of heat exchanger is a key component to hydrogen generation by the thermochemical sulfur-iodine water-splitting process, a future technology that promises efficient hydrogen production if coupled to a Generation IV nuclear reactor heat source. Characterization of each material was carried out in the cast and wrought conditions with optical and SE microscopy, electron dispersive spectrometry, chemical composition analysis, and thermodynamic modeling. Materials have been characterized according to grain size and morphology, precipitate features, twinning characteristics, and platinum composition effects. Results indicate that platinum and carbon compositions have the greatest effect on the development of microstructural features.
(cont.) Increasing platinum compositions in both base alloy chemistries fosters the presence of annealing twins, which indicates that platinum additions reduce stacking fault energy within the alloy systems. Platinum additions appear to cause the development of larger grain structures as well as increase corrosion resistance. With the exception of the Alloy 800 HT - 30 wt% Pt system, the alloy systems characterized herein were melted with carbon contents between 1.2 - 3.6 times higher than the maximum specified compositions for the base chemistries. Excessive inter and intra-granular carbide precipitation resulted, which leads to compromised corrosion resistance and mechanical properties. Inter-granular attack due to sensitization is observed in the Alloy 800 HT - 2, 5 wt% Pt systems. SEM micrographs of the Alloy 617 - Pt systems show that these systems are less prone to inter-granular attack. The grain structures of each base alloy - Pt system are much finer than those of the respective base alloy systems included for comparison. Fine grain structures are detrimental to overall ductility and high temperature creep strength. On average, the Alloy 800 HT - Pt systems developed larger grains than the Alloy 617 - Pt systems.
(cont.) A two phase microstructure that resembles pearlite developed in the Alloy 617 - 30 wt% Pt system. This alloy system will be excluded from further characterization for self catalytic structural application due to expected poor mechanical and corrosion resistance properties. The most important microstructural improvements for the development of a self-catalytic structural material include a reduction of carbon content and an increase in grain size. Further characterization of catalytic, corrosion resistance, and mechanical properties are required for selection of the optimum platinum addition to the base chemistries of Alloys 800 HT and 617 for sulfuric acid decomposition service.
by David Andrés Rigual.
S.M.

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Andersson, Emil. "Online Metallurgical Mass Balance and Reconciliation." Thesis, Umeå universitet, Institutionen för fysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-185252.

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In mineral processing, one of the most important and versatile separation methods is flotation. Flotation utilizes the different surface properties of the valuable minerals in the ore to separate them from the less valuable gangue material in the ore. Crushed and ground ore is mixed with water and fed into flotation tanks. In the flotation tanks, the particles of valuable mineral are made hydrophobic. That way, they can be floated by attaching to air bubbles and gather on top of the flotation tank as froth. This froth, containing higher concentrations of valuable mineral, is recovered and then processed further. The flotation circuit is controlled and maintained using measurements on the mass flows and grades of different materials. Due to economical, practical, and technological limitations, these measurements are performed at a chosen number of points in the circuit and at discrete points in time. Poor measurement data can have devastating consequences if the operators are left with limited information and errors in the circuit remain undetected. The accuracy of the acquired measurements is improved by performing mass balance and reconciliation. Traditionally, mass balance uses the sum of the total mass flows and the average grades over long times to avoid including the internal mass of the circuit in the calculations. It is desirable to perform mass balance directly to allow for faster intervention if any failures occur in the circuit during the on-line process. This report describes an on-line dynamic approach towards mass balancing and reconciliation of the mass flows and grades in a flotation circuit. Here, physical models of the flotation circuit are used to construct mass balance constraints using interpolation and test functions and the mass balance problem is posed as an optimization problem. The optimization problem is to adjust the assay such that the residual, the difference between the measured and the adjusted assay, is minimized while maintaining mass balance. An implementation in MATLAB and tests on synthetic data show that the dynamic formulation of mass balance does adjust 'erroneous' measurements such that mass balance is fulfilled. Given this result, there are still important aspects of the implementation that have to be addressed. The model uses the unknown and cell specific parameters flotation rate and recovery. Thus, these must be found or properly modeled. This report proposes a possible model for flotation rate as well as a strategy to find the recovery. The requirements of accuracy and speed of the implementation are also discussed. Possible next steps of this project is to further confirm a time effective implementation using synthetic data. Consequently, the implementation can be adapted for natural data in order to verify correctness of models.
I malmanrikning, är flotation en av de viktigaste och mest mångsidiga metoderna. Flotation utnyttjar de fysikaliska ytegenskaperna som partiklar av värdemineral har för att separera dessa från det mindre värdefulla gråberget i malmen. Krossad och mald malm blandas med vatten och matas in i flotationstankar. I flotationstankarna görs partiklarna av värdemineral hydrofobiska. På så vis kan de fästa sig vid luftbubblor och flyta till ytan och bilda ett skum. Detta skum samlas sedan ihop och behandlas vidare eftersom det innehåller en högre koncentration av värdemineral. Flotationskretsen styrs och underhålls med hjälp av mätningar av massflödena och halterna av de olika ämnena som finns i kretsen. På grund av ekonomiska, praktiska, och teknologiska hinder kan dessa mätningar bara göras på ett utvalt antal punkter i kretsen samt bara vid diskreta tillfällen. Felaktigt data kan ha förödande konsekvenser om operatörerna lämnas med begränsad information och processen fortlöper med oupptäckta fel. Mätsäkerheten kan förbättras med hjälp av massbalansering och haltjustering. Traditionellt görs massbalansering genom att summera den totala massan som löpt genom kretsen samt medelvärden av halterna över lång tid för att undvika att räkna in den interna massan i systemet. Det är önskvärt att utföra massbalansering direkt för att möjliggöra snabbare ingrepp ifall fel uppstår i kretsen under den fortlöpande processen. Denna rapport beskriver en dynamisk lösning för massbalansering och justering av massflöden och halter i en flotationskrets. Här används fysikaliska modeller av kretsen för att konstruera bivillkor för massbalans med hjälp utav interpolation och testfunktioner och massbalanseringsproblemet ställs upp som ett optimeringsproblem. Optimeringen sker genom att justera mätserien så att residualen, skillnaden mellan det uppmätta värdet och det justerade värdet, minimeras under uppfyllande av mass balans. En implementation i MATLAB och tester på syntetisk data visar att den dynamiska formuleringen av massbalans justerar de felaktiga mätvärdena så att massbalans uppfylls. Med det resultatet i åtanke, finns det fortfarande viktiga aspekter av implementationen som bör tas hänsyn till. Modellen använder de okända och cellspecifika parametrarna flotationshastighet och utbytet och dessa måste kunna bestämmas för att denna modell ska kunna användas. Ett förslag på modellering av flotationshastigheten föreslås i rapporten. Dessutom ges förslag på strategier att hitta utbytet. Kraven på noggrannhet och snabbhet diskuteras också. Möjliga nästa steg för projektet är att vidareutveckla en tidseffektiv implementation genom att använda syntetiska data. Därefter kan en implementation för naturligt data verifiera modellerna.

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18

Ma, Taoran. "Powder-metallurgical processing and phase separation in ternary transition metal carbides." Doctoral thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-207839.

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Ternary transition metal cubic carbides have high hardness and are potential carbides in cemented carbide and cermet tools, as well as hard coatings used to improve metal cutting performance. In the present work, (Ti,Zr)C, (V,Nb)C, and (V,Ta)C ternary cubic carbides were synthesized using traditional powder-metallurgical methods. The effect of synthesis temperature and starting materials on synthesis is investigated, and the microstructure evolution during aging is studied. (Ti,Zr)C was found to decompose into lamellae upon aging at the temperature range from 1150 to 1800 °C. A similar microstructure was observed in (V,Ta)C and (V,Nb)C- 0.5 wt% Fe. All of these structures were found to form through discontinuous precipitation.The grain misorientation distribution of (Ti,Zr)C aged at 1400 °C is investigated. It was found that decomposition tends to occur at high-angle grain boundaries above 25°. The hardness of as-synthesized (Ti,Zr)C powder was found to be 41±6 GPa. Fully decomposed (Ti,Zr)C particles were found to be slightly harder than the undecomposed counterpart. On the other hand, in (V,Nb)C-0.5 wt% Fe, the decomposed structure formed upon aging at 1200 °C was found to have a hardness of 26±2 GPa, which is basically the same as the unaged alloy.Furthermore, the sintering behavior of (Ti,Zr)C with WC-Co is investigated. There are two γ-phases in the final microstructure, one TiC-rich and one ZrC-rich. (Ti,Zr)C was found to decompose at an early stage of sintering, and the final grain size of WC and the two γ-phases was found to be 10% smaller than that in a reference WC-TiC-ZrC-Co composite.

QC 20170529

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19

Stella, Piergiorgio. "Powder metallurgy: investigation of metallurgical and technological aspects and potential applications for critical components of turbomachineries." Doctoral thesis, Università degli studi di Trento, 2016. https://hdl.handle.net/11572/369124.

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The application of powder metallurgy (PM) technologies to the manufacturing of Oil & Gas turbomachineriesâ€™ components was investigated in the course of research collaboration with the Material and Processes Engineering Department of General Electric Oil & Gas (Italy). The thesis focused on the study of the pressure-assisted Hot Isostatic Pressing technology for the processing of the corrosion resistant Ni-base alloy N07626. The densification behaviour of the N07626 metal powder in condition of pressure assisted sintering was investigated by experiments conducted on a small scale by uniaxial hot pressing condition using a Spark Plasma Sintering (SPS) machine in the aim of extending the result to the initial stage of densification of HIP. The SPS exepriments demonstrated that the densification rate is strongly affected by the process temperature and it is less sensitive to the variation of applied pressure. The microstructure and mechanical properties of full-dense HIPped N07626 alloy, produced according to a fixed proprietary cycle and several experimental deviations were analyzed. The microstructure was studied by Optical Metallography, Scanning Electron Microscopy, Energy Dispersed X-Ray Spectroscopy and Electron Backscatter Diffraction. The mechanical properties of the alloy were assessed by tensile testing, conventional and instrumented Charpy V-Notch testing, JIC fracture toughness tests and fatigue crack growth rate testing. The tensile and impact toughness properties resulted sensitive to the local accumulation of oxygen in Oxygen Affected Zones (OAZs), that leads to a ductile to brittle transition in the impact toughness of the material. Two models for formation of OAZs were proposed based on the phase transformation and the oxidation/reduction reactions taking place in the HIP. The mechanical properties were discussed on the base of the microstructure of the Prior Particle Boundaries (PPBs) interface, focusing of the phase transformation products, represented by a thin layer of submicrometric oxides and carbides. The fracture mode was explained by the analogy with models of ductile micro-mechanisms of void nucleation and coalescence and with fracture models of particulate reinforced metal-matrix-composite. The Charpy impact toughness and the fracture toughness were correlated to the oxygen concentration and to the density of inclusions. The fatigue crack propagation behavior was discussed focusing on the effect of clustering of inclusions on the crack propagation path. A relation between the Paris slope with the impact toughness was found. Finally the increase of processing temperature (HIP and heat treatment) was found significanty beneficial for the toughness. This effect was investigate by grain-size analysis and was proposed to be related to a reduction of density of PPBs inclusions.

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20

Stella, Piergiorgio. "Powder metallurgy: investigation of metallurgical and technological aspects and potential applications for critical components of turbomachineries." Doctoral thesis, University of Trento, 2016. http://eprints-phd.biblio.unitn.it/1688/1/PhD_tesi_STELLA.pdf.

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The application of powder metallurgy (PM) technologies to the manufacturing of Oil & Gas turbomachineries’ components was investigated in the course of research collaboration with the Material and Processes Engineering Department of General Electric Oil & Gas (Italy). The thesis focused on the study of the pressure-assisted Hot Isostatic Pressing technology for the processing of the corrosion resistant Ni-base alloy N07626. The densification behaviour of the N07626 metal powder in condition of pressure assisted sintering was investigated by experiments conducted on a small scale by uniaxial hot pressing condition using a Spark Plasma Sintering (SPS) machine in the aim of extending the result to the initial stage of densification of HIP. The SPS exepriments demonstrated that the densification rate is strongly affected by the process temperature and it is less sensitive to the variation of applied pressure. The microstructure and mechanical properties of full-dense HIPped N07626 alloy, produced according to a fixed proprietary cycle and several experimental deviations were analyzed. The microstructure was studied by Optical Metallography, Scanning Electron Microscopy, Energy Dispersed X-Ray Spectroscopy and Electron Backscatter Diffraction. The mechanical properties of the alloy were assessed by tensile testing, conventional and instrumented Charpy V-Notch testing, JIC fracture toughness tests and fatigue crack growth rate testing. The tensile and impact toughness properties resulted sensitive to the local accumulation of oxygen in Oxygen Affected Zones (OAZs), that leads to a ductile to brittle transition in the impact toughness of the material. Two models for formation of OAZs were proposed based on the phase transformation and the oxidation/reduction reactions taking place in the HIP. The mechanical properties were discussed on the base of the microstructure of the Prior Particle Boundaries (PPBs) interface, focusing of the phase transformation products, represented by a thin layer of submicrometric oxides and carbides. The fracture mode was explained by the analogy with models of ductile micro-mechanisms of void nucleation and coalescence and with fracture models of particulate reinforced metal-matrix-composite. The Charpy impact toughness and the fracture toughness were correlated to the oxygen concentration and to the density of inclusions. The fatigue crack propagation behavior was discussed focusing on the effect of clustering of inclusions on the crack propagation path. A relation between the Paris slope with the impact toughness was found. Finally the increase of processing temperature (HIP and heat treatment) was found significanty beneficial for the toughness. This effect was investigate by grain-size analysis and was proposed to be related to a reduction of density of PPBs inclusions.

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21

Moosberg-Bustnes, Helena. "Fine particulate by-products from mineral and metallurgical industries as filler in cement-based materials /." Luleå, 2003. http://epubl.luth.se/1402-1544/2003/36.

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22

Saeed, Mohazzam. "Exploring effects of hydrodynamic flotation variables on their respective metallurgical responses through laboratory scaling up." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-87078.

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To meet the increasing demand for raw materials, higher throughput of mineral separation through froth flotation is becoming important. This higher throughput can be achieved by increasing the size of flotation equipment termed scaling up. Flotation performance is greatly affected by the size of flotation machines and remains an important research area to correlate flotation behavior between small and larger flotation machines. The Outotec GTK LabCell®, a mechanical flotation machine, has been used as a benchmark for many industrial pre-feasibility studies around the world for the past decade. This study deals with the scale-up assessment in terms of flotation rate constant between 2 L and 7.5 L flotation cells of the Outotec GTK LabCell®, machine. The design of these lab scale flotation machines is comparable to other Outotec industrial scale flotation equipment considering rotor and impeller design, and the main difference is in scale. The influence of the hydrodynamic parameters on the flotation performance in both the cells was investigated by varying the impeller tip speed and superficial gas velocity. Particle size distribution analysis indicated concentrate product was finer at smaller cell size at all combinations of impeller tip speed and superficial gas velocity. The results showed for both cells, mass and water recovery increased with an increase in the impeller tip speed and superficial gas velocity until a certain value, after which they decreased. Maximum mass and water recovery were achieved using an impeller tip speed of 3.1 m/s and superficial gas velocity of 0.21 cm/s. Flotation kinetic analysis indicated scaling up of flotation cells was possible at different impeller tip speed by keeping the superficial gas velocity at 0.21 cm/s.

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23

Lotfian, Samira. "Alternative reducing agents in metallurgical processes : Experimental study of thermal characterization of shredder residue material." Licentiate thesis, Luleå tekniska universitet, Mineralteknik och metallurgi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26641.

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Coal used in metallurgical processes can participate in reduction reactions to produce metals and alloys from oxides. Base metals production leads to generation of slag, which contains valuable metals that can be recovered and recycled. There are several options to treat the slag, depending on the metal content in the slag. One is slag fuming, which is a well-established process that is traditionally used to vaporize zinc from zinc containing slags, mainly lead blast furnace slag, but is applied in a few plants for copper smelting slags. In this process reduction is achieved using pulverized coal, lump coal or natural gas. Conventionally pulverized coal injected to the furnace is utilized both to participate in reduction reactions and also to supply heat. On the other hand, the amount of possible alternative reducing agents such as residue plastic material is increasing steadily and the issue of sustainable disposal management of these materials has arisen. As carbon and hydrogen are major constituents of the residue plastic-containing materials, they have the potential to be an auxiliary source of reducing agents, to partially replace conventional sources such as coal. Shredder Residue Material (SRM) is a plastic-containing residue material after separation of main metals. Utilization of SRM as an alternative reducing agent, would lead to not only decreased dependency on primary sources such as coal but also to an increase in the efficiency of utilization of secondary sources. This calls for systematic scientific investigations, wherein these secondary sources are compared with primary sources with respect to e.g., devolatilization characteristics, gasification characteristics and reactivity. As a first step, devolatilization characteristics of SRM are compared with those of coal using thermogravimetric analysis. To study the reduction potential of the evolved materials, composition of evolved off-gas was continuously monitored using quadrupole mass spectroscopy. To gain a better understanding of possible interaction of plastics in a mixture, the devolatilization mechanisms and the volatile composition of three common plastics; polyethylene, polyurethane and polyvinylchloride and their mixture have been studied. Furthermore, gasification characteristics and reactivity of char produced from SRM is compared with coal char. The effect of devolatilization heating rate on gasification rate of char was investigated. Proximate analysis has shown that SRM mainly decomposes by release of volatiles, while coal shows high fixed carbon content, which is reported to contribute to reduction reactions. The composition of volatiles shows H2, CO and hydrocarbons which are known to have reduction potential. Therefore, it is essential that SRM be used in a process that could utilize the evolved volatiles for reduction. The results confirm the interaction between the plastics within the binary and ternary mixtures, which suggests that similar phenomenon may occur during devolatilization of SRM. Although the char produced from SRM contains lower amounts of fixed carbon compared to coal char, it has a porous structure and high surface area, which makes it highly reactive during gasification experiments. In addition to physiochemical properties, the catalytic effect of ash content of SRM char contributes to its higher reactivity and lower activation energy value compared to coal char. Moreover, the gasification reactivity of char produced at fast devolatilization heating rate was highest, due to less crystalline structure of produced char.

Godkänd; 2016; 20160517 (samlot); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Samira Lotfian Ämne: Processmetallurgi /Process Metallurgy Uppsats: Alternative Reducing Agents in Metallurgical Processes Experimental Study of Thermal Characterization of Shredder Residue Material Examinator: Professor Caisa Samuelsson, Institutionen för samhällsbyggnad och naturresurser, Avdelning: Mineralteknik och metallurgi, Luleå tekniska universitet. Diskutant: PhD Noureddine Menad, BRGM, Geoscience for Sustainable Earth, France. Tid: Fredag 17 juni, 2016 kl 10.00 Plats: F343, Luleå tekniska universitet

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24

Erkers, Louise, and Felicia Fröjd. "Metallurgical Analysis of Viking Age Amulet Rings : and Comparison With Cutting Tools." Thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209778.

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Artefacts known as amulet rings, a kind of Viking age jewellery, have often been encountered during archaeological excavations of Viking Age sites. The rings do not appear to have any practical use, but are rather considered to be of cultural or religious importance. Their exact function is however unclear, as are the details regarding the production and material choices for the rings.This study mainly examines the microstructure of samples from Viking Age amulet rings found in Dalecarlia, Sweden. To be able to conclude how much effort that was put into the rings a comparison with medieval cutting tools was conducted. Thus, the knives were made with more care in order to obtain the material properties required to give the knives the sharpness and hardness they need to function. The analysis shows that the amulet rings were made from heterogeneous low-carbon steel, indicating little or no welding and a poor-quality starting material. Were as the microstructure of the knives had homogeneous microstructures often involving perlite, showing decent carbon content.Thus, it appears that the Viking Age smiths forged the amulet rings without putting too much effort into the process.This study also involved the manufacturing of a new knife from low-carbon steel, this was done to see if it was possible to redeem carbon into the surface while forging. This however, was difficult when not having todays technical equipment at hand, thus the result was insufficient.
Historiska föremål, kallade amulett ringar vilket är ett slags vikingatida smycken, har hittats vid arkeologiska utgrävningar av vikingatida boplatser. Man har inte hittat något praktiskt användningsområde för ringarna, utan de tros vara av kulturell eller religiös betydelse. Deras funktion är dock oklar, likaså detaljerna angående tillverkningen och materialvalet för ringarna.Denna studie undersöker mikrostrukturen av amulett ringar från Dalarna i Sverige. För att kunna dra slutsatser om hur mycket arbete som lades på ringarna genomförs en jämförelse med medeltida eggverktyg. Eftersom eggverktyg gjordes med omsorg för att få rätt materialegenskaper för att vara vassa och hårda kan man jämföra dessa med ringarna. Analyserna visade att amulett ringarna var gjorda av lågkolhaltigt heterogent stål som indikerar enbart lite eller ingen vällning och ett dåligt utgångsmaterial. Tillskillnad från eggverktygen som uppvisade en homogen mikrostruktur som ofta innehöll perlit vilket tyder på relativt hög kolhalt. Följaktligen framstår det som att vikingatida smeder inte la ned särskilt mycket tid i smidesprocessen vid tillverkningen av amulett ringar.Denna studie innefattar också smidet av en ny kniv från ett lågkolhaltigt stål för att se om det är möjligt att lösa in kol i ytan genom smidet. Detta var dock svårt att göra utan dagens tekniska utrustning vilket gjorde att resultatet inte visade någon uppkolning.

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25

Martello, Robert 1968. "Paul Revere's metallurgical ride : craft and proto-industry in early America." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/109637.

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Nordgren, Eric. "The effect of metallurgical structure on the chloride-induced corrosion of archaeological wrought iron." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/97535/.

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Archaeological wrought iron artefacts are subject to damaging corrosion while in the burial environment and when subjected to environmental changes after excavation. The role of water, oxygen, and chloride corrosion accelerators are central to iron corrosion processes. Intrinsic factors such as the amount and distribution of slag in wrought iron may also play a role in corrosion processes. This study examined a range of factors that impact on understanding conservation desalination treatments to mitigate corrosion by removing chlorides. While examining the effect of slag on corrosion rate and chloride content formed the core of this project, cracking morphologies within corrosion product layers and their influence on corrosion rates measured by oxygen consumption produced outcomes of interest for designing the practicalities of treatment procedures. The slag content of the wrought iron objects examined in this study did not correlate with either their corrosion rate or their chloride content. In line with other authors, clustering of chloride around slag inclusions was identified. This confirmed slag does act as a focus for developing corrosion centres, which will offer challenges for chloride removal and hence provide opportunity for post-treatment corrosion. The alkaline sulphite washing applied to the iron nails produced results that aligned with those reported in other studies and confirmed its relative efficiency for removing chloride. Of major relevance to conservators designing alkaline washing techniques is assigning treatment time and specifying treatment environment. These decisions are aided by evidence provided in this study, which showed that immersing the chloride ii containing corrosion product β-FeOOH in alkaline sulphite entirely transformed it to other iron oxides in only 30 days. During this process it will release its chloride, which will be available for diffusion into the wash solution making a more complete desalination process possible.

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Ogwuda, Olisanwendu Ikechukwuka. "Materials science appraisal of recycled construction materials for roadways." Thesis, Abertay University, 2007. https://rke.abertay.ac.uk/en/studentTheses/70d295b3-60d9-427e-a012-c9cc05ac83e1.

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This thesis reports on a materials science appraisal for recycled construction materials in roadways, that supports engineering decision-making. Inconsistent performance criteria for roadway materials and the variable nature of material source have prompted the need for this research. The aim of the study is to investigate the application of a materials science appraisal to recycled construction materials for use in roadways. The investigation is undertaken through a literature review of roadways, conceptual development of the materials science appraisal methodology, and demonstration of the application of the materials science appraisal to recycled construction materials; and how this supports engineering decision-making. The literature review revealed that there are numerous and proven uses of recycled and secondary materials in roadway applications but there was a lack of necessary integration of materials into categories by material-type, which can better describe behaviour in an engineering situation. Three novel fundamental material types (ceramic, metallic, and polymeric) have been described. The conceptual development of the innovative and novel materials science appraisal, based on material-type, has defined how materials science through a systematic step-by-step procedure can be used to achieve engineering sustainability in roadways and provide support in engineering decision-making. The application of the novel concept of the materials science appraisal to recycled construction materials is shown through the essence of laboratory testing. The results from the materials science appraisal, together with sensitivity analysis, give an informed engineering decision on product choice. The appraisal is novel in that it is proposing a new theory on materials science and developed a paradigm shift in the evaluation of recycled construction materials. The appraisal overcomes the absence of materials science thinking in the field of roadway engineering. The materials science appraisal is of benefit to various stakeholders (client, consultant, supplier and contractor) as it provides a method for addressing material uncertainties. A system now exists for introducing into designs and any contract the principles of the materials science appraisal that will be of great benefit to industry.

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Fischbein, Ellinor, and Felicia Larsson. "Metallurgical analysis of some osmund iron from Sweden and Estonia : A short historical review of medieval iron production and export." Thesis, KTH, Materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298414.

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During the Middle Ages, Sweden was a coveted exporter of high-quality iron in Europe. Bloomery furnaces could have produced osmund iron. However, most osmund iron was produced in blast furnaces. The iron was then treated in the finery process and cut into pieces. Previous studies establish osmund iron’s definition regarding properties, microstructure and trace elements. They were often slag-rich and varied greatly in carbon content, proportion of inclusions, corrosion and microstructure. The report examined osmund iron as related to medieval iron production, exports and quality. This was done by comparing the microstructures and slag inclusions in Swedish and Estonian pieces of medieval iron, through analyses by SEM-EDS and under an optical microscope. The Estonian samples had more slag inclusions. The samples with corroded inclusions/slag were rejected. The varying microstructure can be linked to the cooling rate and the actual production in the blast furnace, bloomery furnace and finery process. It gave materials with poor properties. A large proportion of the samples had one side with a higher carbon content while the other had lower carbon content. The iron with lower carbon content could be connected to come from the bloomery furnace and the higher to the blast furnace. The samples containing higher levels of silica, magnesium and calcium could be connected to the blast furnace. In summary, the Swedish samples were of better quality than the Estonian ones and all pieces were considered to come from the blast furnace.
Under medeltiden var Sverige en eftertraktad exportör av högkvalitativt järn i Europa. Osmundjärn kunde produceras i en blästerugn, men det mesta osmundjärnet framställdes i masugnen. Därefter färskades järnet och höggs upp i delar. Tidigare analyser definierar osmundjärns utseende, egenskaper, mikrostruktur och spårämnen. De var ofta slaggrika och varierade mycket i kolhalt, andel inneslutningar, mikrostruktur och mängd korrosion. I den här studien analyserades osmundjärn relaterat till medeltida järnframställning, export och kvalité. Det gjordes genom att jämföra mikrostrukturer och slagginneslutningar i svenska och estniska prover av medeltida järn, genom analyser i SEM-EDS och i ljusmikroskop. De estniska proverna hade mer slagginneslutningar. Proverna med korroderade inneslutningar/slagg uteslöts ur analysen. Den varierande mikrostrukturen kan kopplas till kylningshastigheten och själva produktionen i masugnen, blästerugnen och färskningsprocessen. Det gav material med dåliga egenskaper. En stor andel prover hade en sida med högre kolhalt och den andra delen hade lägre kolhalt. Järnet med lägre kolhalt kan kopplas till att komma från blästerugnen och det med högre kolhalt till masugnen. De proverna som innehöll högre halter kiseldioxid, magnesium och kalcium kan kopplas till masugnen. De svenska proverna hade sammanfattningsvis bättre kvalité än de estniska och alla bitar ansågs komma från masugnen.

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Forclaz, A. "Variational methods in materials science." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249532.

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Three problems are being investigated in this thesis. The first two relate to the modelling and analysis of martensitic phase transitions, while the third is concerned with some mathematical tools used in this setting. After a short introduction (Chapter 1) and overviews of the calculus of variations and martensitic phase transformations (Chapter 2), the research part of this thesis is divided into three chapters. We show in Chapter 3 that for the two wells $\mathrm{SO}(3)U$ and $\mathrm{SO}(3)V$ to be rank-one connected, where the $3\times 3$ symmetric positive definite $U$ and $V$ have the same eigenvalues, it is necessary and sufficient that $\mathrm{det}(U-V)=0$, a result that does not hold in higher dimensions. Using this criterion and a result of Gurtin, formulae for the twinning plane and the shearing vector are obtained, which yield an extremely simple condition for the occurrence of so-called compound twins. Our results also provide a simple classification of the twinning mode of the two wells by looking at the crystallographic properties of the eigenvectors of the difference $U-V$. As an illustration, we apply our results to cubic-to-tetra gonal,tetragonal-to-monoclinic and cubic-to-monoclinic transitions. Chapter 4 focuses on the mathematical analysis of biaxial loading experiments in martensite, more particularly on how hysteresis relates to metastability. These experiments were carried out by Chu and James and their mathematical treatment was initiated by Ball, Chu and James. Experimentally it is observed that a homogeneous deformation $y_1(x)= U_1x$ is the stable state for `small' loads while $y_2(x)=U_2x$ is stable for `large' loads. A model was proposed by Ball, Chu and James which, for a certain intermediate range of loads, predicts crucially that $y_1(x)=U_1x$ remains metastable i.e., a local - as opposed to global - minimiser of the energy). This result explains convincingly the hysteresis that is observed experimentally. It is easy to get an upper bound for when metastability finishes. However, it was also noticed that this bound (the Schmid Law) may not be sharp, though this required some geometric conditions on the sample. In this chapter, we rigorously justify the Ball-Chu-James model by means of De Giorgi's $\Gamma$-convergence, establish some properties of local minimisers of the (limiting) energy and prove the metastability result mentioned above. An important part of the chapter is then devoted to establishing which geometric conditions are necessary and sufficient for the counter-example to the Schmid Law to apply. Finally, Chapter 5 investigates the structure of the solutions to the two-well problem. Restricting ourselves to the subset $K=\{H\}\cup \mathrm{SO}(2)V \subset\mathrm{SO}(2)U\cup\mathrm{SO}(2)V$ and assuming the two wells to be compatible, we let $T_1$ and $T_2$ denote the two (not necessarily distinct) twins of $H$ on $\mathrm{SO}(2)V$ and ask the following question: if $\nu_x$ is a non-trivial gradient Young measure almost everywhere supported on $K$, does its support necessarily contain a pair of rank-one connected matrices on a set of positive measure? Although we do not provide a solution for the general case, we show that this is true whenever (a) $\nu_x\equiv \nu$ is homogeneous and $\mathrm{supp}\nu\cap \mathrm{SO}(2)V$ is connected, (b) $\nu_x\equiv \nu$ is homogeneous and $T_1=T_2$ i.e., when the two wells are trivially rank-one connected) or (c) $\mathrm{supp}\nu_x \subset F$ a.e., for some finite set $F$. We also establish a more general case provided a strong `rigidity' conjecture holds.

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Rouet-Leduc, Bertrand. "Machine learning for materials science." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/267987.

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Machine learning is a branch of artificial intelligence that uses data to automatically build inferences and models designed to generalise and make predictions. In this thesis, the use of machine learning in materials science is explored, for two different problems: the optimisation of gallium nitride optoelectronic devices, and the prediction of material failure in the setting of laboratory earthquakes. Light emitting diodes based on III-nitrides quantum wells have become ubiquitous as a light source, owing to their direct band-gap that covers UV, visible and infra-red light, and their very high quantum efficiency. This efficiency originates from most electronic transitions across the band-gap leading to the emission of a photon. At high currents however this efficiency sharply drops. In chapters 3 and 4 simulations are shown to provide an explanation for experimental results, shedding a new light on this drop of efficiency. Chapter 3 provides a simple and yet accurate model that explains the experimentally observed beneficial effect that silicon doping has on light emitting diodes. Chapter 4 provides a model for the experimentally observed detrimental effect that certain V-shaped defects have on light emitting diodes. These results pave the way for the association of simulations to detailed multi-microscopy. In the following chapters 5 to 7, it is shown that machine learning can leverage the use of device simulations, by replacing in a targeted and efficient way the very labour intensive tasks of making sure the numerical parameters of the simulations lead to convergence, and that the physical parameters reproduce experimental results. It is then shown that machine learning coupled with simulations can find optimal light emitting diodes structures, that have a greatly enhanced theoretical efficiency. These results demonstrate the power of machine learning for leveraging and automatising the exploration of device structures in simulations. Material failure is a very broad problem encountered in a variety of fields, ranging from engineering to Earth sciences. The phenomenon stems from complex and multi-scale physics, and failure experiments can provide a wealth of data that can be exploited by machine learning. In chapter 8 it is shown that by recording the acoustic waves emitted during the failure of a laboratory fault, an accurate predictive model can be built. The machine learning algorithm that is used retains the link with the physics of the experiment, and a new signal is thus discovered in the sound emitted by the fault. This new signal announces an upcoming laboratory earthquake, and is a signature of the stress state of the material. These results show that machine learning can help discover new signals in experiments where the amount of data is very large, and demonstrate a new method for the prediction of material failure.

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Hartmann, Markus. "Lattice models in materials science." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2006. http://dx.doi.org/10.18452/15432.

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In der vorliegenden Arbeit wurden drei unabhängige Problemfelder moderner biophysikalischer und materialwissenschaftlicher Forschung untersucht: Diffusion in binären Legierungen, der Umbauprozess in trabekulärem Knochen und die Voraussage mechanischer Eigenschaften, insbesonders der Biegesteifigkeit, selbstorganisierender, amphiphiler Membrane. Für alle drei Problemfelder wurden Gittermodelle gewählt, um ausgesuchte Fragestellungen zu untersuchen. Für den Fall der Diffusion in Legierungen war dies, inwieweit sich der Diffusionprozess, der sich auf atomarer Ebene als diskrete Platztäusche zwischen Atomen und Leerstellen manifestiert, auf einer größeren, makroskopischen, Ebene mit Hilfe einer kontinuumstheoretischen Theorie beschreiben lässt. Im Fall der Beschreibung des Umbauprozesses in in trabekulärem Knochen wurde die die spongiöse Architektur des Knochens auf ein Gitter abgebildet und mittels einer vereinfachten mechanischen Beschreibung die lokale Belastung in jedem Knochenelement bestimmt. Die zeitliche Entwicklung des Systems wurde mittels eines stochastischen Umbaugesetzes gesteuert, das die Wahrscheinlichkeit für Knochenan- bzw. -abbau als Funktion der lokalen Volumenänderung vorgab. Es wurde gezeigt, dass ein nicht-lineares Umbaugesetz bessere Übereinstimmung mit experimentellen Ergebnissen zeigt, als ein rein lineares. Weiters wurde das Krankheitsbild der Osteoporose untersucht und es konnte eine Unterscheidung zwischen einem normalen Alterungsprozess der Knochenstruktur und einer krankhaften Veränderung gezogen werden. Um die mechanischen Eigenschaften selbstorganisierender Membrane zu bestimmen, wurden linear elastische Federkräfte zwischen benachbarten Molekülen angenommen. Die volle elastische Matrix und daraus die gewünschten Eigenschaften wurden für unterschiedliche Zusammensetzungen der Membrane bestimmt. Es wurde gezeigt, dass die Biegesteifigkeit solcher Membrane in einem begrenzten Konzentrationsbereich um mehrere Größenordnungen variieren kann.
This thesis presents the results of investigations on three independent research topics of modern biophysical and materials science research: substitutional diffusion in binary alloys, the remodelling process in trabecular bone and the prediction of mechanical properties of self assembling, amphiphilic bilayers. The basic description of all three projects is based on lattice models, a highly successful class of models that are used in several fields of modern physics to describe physical processes. For the diffusional process in alloys, which on a microscopic scale manifests in a discrete site exchange between one atom and a neighbouring vacancy, it was investigated how this microscopic description can be reconciled with a macroscopic continuum model. For the investigations on remodelling of trabecular bone, the architecture of bone was mapped onto a lattice and the local mechanical state of each element was determined by a simplified mechanical model. A stochastic description was chosen to model the time evolution of the system, relating the probability of bone formation and resorption, respectively, to the local volume changes of the bone elements. It was shown that a non-linear remodelling law is a better candidate to describe the remodelling process in real bone than a linear one. Furthermore, applying the model to osteoporosis - a wide spread bone disease - it was shown that in the features attributed to osteoporosis one has to distinguish between normal ageing of bone''s architecture and additional changes that stem from pathological alterations in the regulatory system. A simple concept was introduced to model the mechanical properties of self-assembled membranes. The molecules forming the membrane are assumed to occupy a triangular lattice, nearest neighbours are connected by linear elastic springs. It was shown that the bending rigidity exhibits a pronounced concentration dependence, varying over orders of magnitude in a narrow concentration regime.

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Perez, Demydenko Camilo. "Static and dynamic disorder in nanocrystalline materials." Doctoral thesis, Università degli studi di Trento, 2019. https://hdl.handle.net/11572/368145.

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Peak profiles in X-ray Diffraction (XRD) patterns from nanocrystalline materials are affected by static and dynamic disorder which is specific of the size and shape of the nanocrystalline domains. Owing to their intrinsic differences, the two types of disorder can be separated, providing independent information from the modelling of the XRD patterns. In the present thesis a model for the static strain created by the nanoparticle surface is proposed. The model is built within the frame of the Whole Powder Pattern Modelling (WPPM) approach for XRD line profile analysis, developed at the University of Trento in the past 20 years. The WPPM approach is decribed in details. Based on a complex Fourier Transform of the diffraction profiles, the model leads to general equations to be used with the WPPM approach to represent the distorted atomic configuration with respect to the reference bulk one. The model was also implemented in TOPAS, a commercial and very popular software, developing a specific macro allowing a larger community of users to benefit of this new opportunity of studying nanocrystalline materials. The thesis work also extended to a more traditional and general description of strain broadening of XRD peak profiles, involving invariant forms under the Laue group symmetry operations of the material under study. As for the dynamic strain, the fundamentals of the Thermal Diffuse Scattering (TDS) contribution to the peak profiles are reviewed. Starting from the original work of B.E. Warren, the theory is generalized to account for surface effects, leading to a particular model developed recently at the University of Trento. This model was thoroughly reviewed and corrected. To test the model a parallel computer code in C was written, exploiting Molecular Dynamics simulations for obtaining reliable and independent estimates of static and dynamic disorder in nanocrystals.

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Perez, Demydenko Camilo. "Static and dynamic disorder in nanocrystalline materials." Doctoral thesis, University of Trento, 2019. http://eprints-phd.biblio.unitn.it/3636/1/CAMILO_PEREZ_DEMYDENKO_thesis_PhD.pdf.

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Peak profiles in X-ray Diffraction (XRD) patterns from nanocrystalline materials are affected by static and dynamic disorder which is specific of the size and shape of the nanocrystalline domains. Owing to their intrinsic differences, the two types of disorder can be separated, providing independent information from the modelling of the XRD patterns. In the present thesis a model for the static strain created by the nanoparticle surface is proposed. The model is built within the frame of the Whole Powder Pattern Modelling (WPPM) approach for XRD line profile analysis, developed at the University of Trento in the past 20 years. The WPPM approach is decribed in details. Based on a complex Fourier Transform of the diffraction profiles, the model leads to general equations to be used with the WPPM approach to represent the distorted atomic configuration with respect to the reference bulk one. The model was also implemented in TOPAS, a commercial and very popular software, developing a specific macro allowing a larger community of users to benefit of this new opportunity of studying nanocrystalline materials. The thesis work also extended to a more traditional and general description of strain broadening of XRD peak profiles, involving invariant forms under the Laue group symmetry operations of the material under study. As for the dynamic strain, the fundamentals of the Thermal Diffuse Scattering (TDS) contribution to the peak profiles are reviewed. Starting from the original work of B.E. Warren, the theory is generalized to account for surface effects, leading to a particular model developed recently at the University of Trento. This model was thoroughly reviewed and corrected. To test the model a parallel computer code in C was written, exploiting Molecular Dynamics simulations for obtaining reliable and independent estimates of static and dynamic disorder in nanocrystals.

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Aldén, Rickard. "Metallurgical investigation in weldability of Aluminium Silicon coated boron steel with different coating thickness." Thesis, KTH, Materialvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171209.

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Hot-pressed aluminium and silicon coated boron steel is used in the car industry where high tensile strength is of great importance, such as in the safety cage of a car where deformation has to be kept to a minimum in case of a collision. After hot-pressing the AlSi-boron steel shows excellent properties with high tensile strength, minimal spring back and also shows good protection against corrosion. A thickness of the AlSi coating of 150 [g/m2] for AlSi coated boron steel is typically used by the car industry today. However the coating thickness would be desirable to be minimized to 80 [g/m2]. Welding of this boron steel with 80 [g/m2]have shown difficulties; and it’s not clear why this occurs. In this report the metallurgical properties of the different coating layers will be investigated, simulations with Thermocalc module Dictra will be used, SEM/EDS will be used to characterize phases in coating layers and correlate to weldability. Resistance spot welding tests will also be performed where the welding parameters of pre-pulse, pulse time, time in between pulses and current will be varied to achieve desirable weld plug diameter without expulsion. Hardness testing in form of micro Vickers will executed. The Materials used will be USIBOR® 1500, AS80 with four different annealing times and one sample of AS150.

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Maguire, John F. "Contributions to materials science and engineering." Thesis, Ulster University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515891.

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Stoleriu, Iulian. "Integro-differential equations in materials science." Thesis, University of Strathclyde, 2001. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21413.

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This thesis deals with nonlocal models for solid-solid phase transitions, such as ferromagnetic phase transition or phase separation in binary alloys. We discuss here, among others, nonlocal versions of the Allen-Cahn and Cahn-Hilliard equations, as well as a nonlocal version of the viscous Cahn-Hilliard equation. The analysis of these models can be motivated by the fact that their local analogues fail to be applicable when the wavelength of microstructure is very small, e. g. at the nanometre scale. Though the solutions of these nonlocal equations and those of the local versions share some common properties, we find many differences between them, which are mainly due to the lack of compactness of the semigroups generated by nonlocal equations. Directly from microscopic considerations, we derive and analyse two new types of equations. One of the equations approximately represents the dynamic Ising model with vacancy-driven dynamics, and the other one is the vacancy-driven model obtained using the Vineyard formalism. These new equations are being put forward as possible improvements of the local and nonlocal Cahn-Hilliard models, as well as of the mean-field model for the Ising model with Kawasaki dynamics.

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Behera, Balaram Bijayakumar, and Neeraj Vimal Prasad. "Erosion wear of materials." Thesis, 2007. http://ethesis.nitrkl.ac.in/4192/1/Erosion_Wear_of_Materials.pdf.

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Wear is damage to a surface as a result of relative motion with respect to another substance. One key point is that wear is damage and it is not limited to loss of material from the surface. However, loss of material is definitely one way in which a part can experience wear. Another way included in this definition is by movement of material without loss of mass. An example of this would be the change of geometry or dimension of a part as a result of plastic deformation (e.g., from repeated hammering). There is also a third mode implied, which is damage to a surface that does not result in mass loss or dimensional changes. An example of this third mode might be development of network of cracks in a surface. This might be of significance in applications where maintaining optical transparency is a prime engineering concern. Lens and aircraft windows are examples where this is an appropriate definition of wear. In the older definitions of wear there used to be a greater stress on the “loss of material”, however now-a-days the newer and more general definitions of wear is very natural to the design or device engineer , who thinks of wear in terms of a change to a part that effects its performance. The focus is on the change which may be translated to damage. The implication of this generalization will be further explored in the discussion of wear measures. Previously wear was defined as damaged to a surface. The most common form of that damage is loss or displacement of material and volume can be used as a measure of wear—volume of material removed or volume of material displaced. For scientific purposes this is frequently the measure used to quantify wear. In many studies, particularly material investigations, mass loss is frequently the measure used instead of volume. This is done because of the relative ease of performing a weight loss measurement. However there are some problems in using mass as primary measure of wear. Direct comparison of materials can only be done if their densities are same. For bulk material this is not a major obstacle, since the density is either known or easily determined. In the case of coatings however, this can be a major problem. The other problems are more intrinsic ones. A mass measurement does not measure displaced materials. In addition it is sensitive to wear debris and transferred material that becomes attached to the surface and can not be removed. This material does not necessarily have to be from the same surface; it can from the counter face as well. From the above it can be seen that volume is the fundamental measure for wear when wear is calculated with loss or displacement of material. However, in engineering applications, is generally with the loss of a dimension, the increase in clearance or change in contour not the volume loss. Volume, mass loss and a dimension are not the only measures for wear that are used in engineering. Life, vibration level, roughness, appearance, friction level, and degree of surface crack or crazing are some of the operational measures that are encountered.

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Noecker, Fredrick F. II. "Metallurgical investigation into ductility dip cracking in nickel based alloys." 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3285743.

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Islam, Rashed Adnan. "Composition - microstructure - property relationships in dual phase bulk magnetoelectric composite." 2008. http://hdl.handle.net/10106/957.

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Dutta, Surajeet Kumar. "Study of the Chemical Composition and Energy value of Woody Biomass Species." Thesis, 2008. http://ethesis.nitrkl.ac.in/121/1/surajeet.pdf.

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In spite of its natural sources, India depends on other countries in terms of energy production, and a transfer from conventional fossil sources to sustainable energy sources is strongly necessary because due to the increasing demand of the energy. Among the sustainable energy sources, biomass is the subject of this study. The characteristics, logistic aspects, environmental aspects, economical, legal and technical aspects are investigated in order to show that the possible biomass co-firing is very important for the construction of economic, sustainable and environmentally friendly energy systems. The aim of the present project work is to determine the calorific value and the proximate analysis of different component of the woody biomass species such as eucalyptus and chakunda. The calorific value and the proximate analysis of the different component of the biomass will help in estimating its future utilization in different industries such as thermal power plant, iron making industries, other metallurgical industries, for generation of energy etc. The aims of the present project works have been to analyze the proximate analysis and calorific value of the woody biomass species. From the proximate analysis we came to the conclusion that ash content of the woody biomass is very low and the volatile matter content is very high as compared to Indian Coal. The calorific value of the biomass species is quite comparable to that of the coal. Any approach towards utilizing the woody biomass species would be positive step towards the energy and environmental crisis.

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Mishra, Barun, and Sandeep Kumar Baliarsingh. "Kinetics of Iron Ore Reduction by Coal and Charcoal." Thesis, 2008. http://ethesis.nitrkl.ac.in/124/1/10404014.pdf.

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In the present investigation, an attempt has been done to study the simultaneous effects of the major processing variables on the extent of reduction of iron ore pellets surrounded by coal or charcoal fines in an externally heated cylindrical steel container (diameter 5cm and height 10cm) placed in muffle furnace. The project goal is to compare the reduction potential of coal and charcoal in reduction of iron ore pellets. Wood charcoal contains very low levels of gangue, sulphur and volatile matter therefore, presenting itself as a very desirable reductant for the reduction of iron ore. The variables studied are time and temperature. The reduction was done at temperatures 8500C, 9000C, 9500C and 10000c. The percentage (degree) of reduction of pellets was calculated at 15, 30, 45, 60 and 90 minutes, after the furnace reached the predetermined reduction temperature. The experiments were statistically designed such that the effect of each variable can be quantitatively assessed and compared. The results showed that, there is an increase in degree of reduction with increase in time and temperature and use of charcoal instead of coal also increased the degree of reduction due to higher fixed carbon content of charcoal. The percentage of swelling showed a random variation with time and temperature. The activation energy for the reduction of iron ore pellet was found to be higher in case of coal as compared to that of in case of charcoal; this indicates that reduction of iron ore by charcoal will be more favorable in case of charcoal.

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Krishnan, Tintula, and Subhram Keshary Singh. "Reduction Kinetics of iron ore pellets and the effect of Binders." Thesis, 2008. http://ethesis.nitrkl.ac.in/125/1/10404011.pdf.

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Reduction of Iron Ore Pellets with a particular percentage of binders i.e. 2% of Dextrine and 2% of Bentonite was carried out for the temperature range 900 to 1050°C. In reduction kinetic study the most satisfactory model was to taken, the slope of the initial linear region of fractional reduction vs. time curve was measured, which gives the rate constant (k). Ln k vs. 1/T plots were straight line from which Activation Energy was calculated. Pellets having different percentages of binders were reduced and compared to find the effect of binders

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Gaur, Ankur. "Effect of Strain Ageing On Welded or Nonwelded Low Carbon Steel." Thesis, 2009. http://ethesis.nitrkl.ac.in/1157/1/strain_ageing.pdf.

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An investigation has been performed on the strain ageing of welded and non-welded specimen of low carbon steel. It was determined that the low carbon steel were susceptible to strain ageing in interstitial solutes. The increase in yield strength, tensile strength and elongation because of strain ageing has been compared between welded and non-welded specimen. At high level of prestrain, the percentage loss in ductility was observed. Increase in the strain-ageing temperature the value of ΔY increased, increase the time of ageing has also got influence on value of ΔY. However the influence of temperature of ageing is much more pronounced than the affect of time of ageing. The change in yield stress due to strain ageing in welded specimen was observed less than the non welded specimen. this increase in yield stress is attributed to the fact that the dislocation density of welded sample is higher than non-welded sample.

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Arvind, K. "J-R Behaviour of 20MnMoNi55 Pressure Vessel Steel." Thesis, 2009. http://ethesis.nitrkl.ac.in/1395/2/bmdthesis.pdf.

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Material of Reactor Pressure Vessel (RPV) should have good fracture toughness to ensure safe operation of nuclear reactor. In order to be on safe side the fracture characteristics of RPV material have to be quantified. In this present work the fracture characteristics of 20MnMoNi55 steel – the material used for Indian PHWR – have been found using J-Integral test. The microstructures of the steel and its relevant mechanical properties such as hardness and tensile properties have been characterized. Monotonic J-R curves of the material have been determined in the temperature of and . Fracture behaviour under quasi-static tearing load has been studied through fracture toughness tests on 20MnMoNi55 steel using Compact Tension(CT) specimens of Width(W)=50 mm and thickness(B)=20 mm. J-R curves were obtained from specimens precracked to. The single specimen unloading compliance method have been used for generating J-R curves. Stretch zone widths (SZW) were measured on the fractured surfaces of broken specimens. The stretch zone dimensions that were determined have been used in conjunction with the experimentally derived J-R curve to obtain a value of the ductile fracture toughness parameter . The initiation toughness, , obtained at the intersection of the blunting line and the power-law fit to the J-R curve, and the critical toughness, , determined following the procedure of the ASTM standard, were estimated. The results of fracture studies under monotonic loading infer: (a) the material exhibits high fracture resistance at room temperature (b) the fracture resistance of the steel deteriorates at a temperature of as compared to room temperature, the deterioration in the fracture properties has been attributed that steel exhibits embrittlement tendencies operative in this temperature. (c) The stretch zone formation is very prominent and starting/ending points are clearly discernible in 20MnMoNi55 steel. The correlation of , critical toughness, and initiation toughness, , has been examined with a view to ascertain the applicability of the stretch zone dimension for measurement of fracture toughness.

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Akarapu, Ashok. "Surface Property Modification of Copper by Nanocomposite Coating." Thesis, 2011. http://ethesis.nitrkl.ac.in/2778/1/Ashok_thesis_final.pdf.

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Copper has high electrical and thermal conductivities, good corrosion resistance at ambient temperature, excellent malleability/workability and reproducibility, apart from these it is cheap and abundantly available metal other than good conducting metals like Silver. But has poor mechanical properties such as hardness and wear resistance. Some applications like Contacts in electrical switches necessitate the improvements in the mechanical properties without much loss of electrical and thermal conductivities. Bulk modification / alloying have been tried but limitations in alloying and adversely decrease in its electrical and thermal conductivities has been reported. Another way to improve its mechanical properties is with Surface modification by developing composite coating on its surface. In the present work we employed Electrodeposition process to develop a composite coating with Cu matrix and Ceramic oxide particles TiO2 (particle size ~202 nm), Al2O3 (particle size ~287 nm) as reinforcements. The coatings were developed with 10 g/l, 30 g/l and 0 g/l (unreinforced) concentrations in bath, at four different current densities (5, 8, 11, 14 A/dm2) with using copper sulfate bath in order to study the effect of Current density and particle concentration in bath, on structure and properties of the coatings developed. The crystallite size was averagely 50-65 nm and a strong (220) texture was obtained in composite coatings and unreinforced Cu coatings determined from the XRD data. The composition and surface morphology of coatings were studied by using EDS and SEM. Hardness and Wear resistance of the coatings were determined by using microhardness tester and ball on plate wear tester, improved hardness and wear resistance of composite coatings were observed compared to the unreinforced copper coatings.

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Madhukar, Poloju. "Synthesis and Characterization of ZnO Nanostructures and Synthesis of Zn/Al2O3 Nanocomposite by Mechanical Alloying Route." Thesis, 2011. http://ethesis.nitrkl.ac.in/2785/1/madhukar_thesis.pdf.

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We report simple methods to synthesize Zinc oxide nanostructures, without using catalysis with less complicity. This was done by oxidation of zinc foil at various temperatures (200oC-1000oC) and various times (1-3h) and also we find that the nanostructures size and shape depends on heating rate, temperature and heating time. Apart from oxidation of zinc we also find zinc oxide nanostructures in Zn-C dry battery. This nanostructure is formed on inner surface of Zn container (which acts as anode). These nanostructures are formed due reaction between electrolyte (mixture composed of manganese (IV) dioxide (MnO2), ammonium chloride (NH4Cl) and zinc chloride (ZnCl2)) and Zn container. In Zn–C cell we find hierarchical and rod like structures. From oxidation of Zn we find rod and leaf like nanostructures. These oxide structures were characterized by SEM, EDX, XRD and DSC. We also synthesized the Zn/Al2O3 metal matrix composite by mechanical alloying method, in this we use oxidized Zn at 800oC for 2h and Al powder in the stoichiometric ratio. The ZnO and Al is milled in planetary ball milling for 30h. During milling displacement reaction takes place and forms Zn/Al2O3 nanocomposite. This nanocomposite is characterized by XRD, SEM, EDX and DSC.

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Verma, Preeti. "Ratcheting Fatigue Behaviour and Post-fatigue Tensile Properties of Commercial Aluminium." Thesis, 2011. http://ethesis.nitrkl.ac.in/2788/1/Final_thesis-Preeti.pdf.

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This investigation examines the ratcheting fatigue behaviour and post-fatigue tensile properties of commercial aluminium in annealed and normalised condition. Ratcheting is the phenomena of progressive accumulation of permanent deformation when a component is subjected to asymmetric cyclic loading which also causes variation in their mechanical properties. One set of commercial aluminium rods were annealed by soaking the as received rods at 200°C for 30 minutes prior to machining and other set were normalised up to same temperature with same soaking time. The microstructural examinations were carried out with the help of optical microscope as well as by scanning electron microscope. Hardness measurements were done using a Vickers hardness tester by applying 3kg load with dwell time of 15 s. Specimen for fatigue test were designed with test section diameter of 10mm and reduced gauge length of 20mm. stress controlled fatigue test were carried out at room temperature up to 150 cycle under different combination of mean stress and stress amplitude in servo-hydraulic testing machine. In annealed condition mean stress is 40, 45, 50 MPa and stress amplitude is 175, 185 MPa, while in normalised condition mean stress is 30, 35, 40 MPa and stress amplitude is 170, 180 MPa. Fatigue test were done at a constant stress rate of 50 MPa/s. In addition a series of specimens were first subjected to 150 cycles of loading prior to carrying out tensile test on these specimens using nominal strain rate 0.83 x 10-5 s-1. Fractographic studies were carried out on the broken samples by using SEM. Hardness was measured after post-fatigue tensile test. The results highlight that accumulation of ratcheting strain increases with increasing mean stress and stress amplitude in both annealed and normalised condition. In normalised condition strain accumulation is less in comparison to annealed. Strain accumulation get saturated after about 40 cycles in annealed condition and 30 cycles in normalised condition for any of the selected test parameters. Post-fatigue tensile strength increases with mean stress and stress amplitude but with associated reduced ductility. It is observed that dimple size decreases with increase in strain accumulation. Hardness also increases with increase in strain accumulation. The increase in strain accumulation is explained by the phenomenon of increased dislocation density during asymmetric cyclic loading, whereas the increase in tensile strength and decrease in ductility are attributed to cyclic hardening.

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48

Mallik, Manila. "Effect of microstructure on the indentation creep behaviour of 2.25Cr-1Mo and its comparison with modified 9Cr-1Mo ferritic steel." Thesis, 2011. http://ethesis.nitrkl.ac.in/2891/1/manila_final_thesis.pdf.

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2.25Cr-1Mo and modified 9Cr-1Mo are extensively used for super heater and reheater tube, header pipe in large-scale thermal and nuclear power plant. Some of the important factors to be considered for selection of such steels are resistance to creep deformation, resistance to environmental attack, corrosion resistance, oxidation resistance. Long term exposure at elevated temperature and pressure can result in microstructural changes. The effective strength, i.e. load bearing capacity of the tubes due to microstructural damages decreases. The failure occurs when it falls below a critical level determined by component geometry and loading. The objective of the investigation is to study the effect of microstructure on the indentation creep behaviour of 2.25Cr-1Mo and its comparison with modified 9Cr-1Mo. Indentation creep tests for 2.25Cr-1Mo ferritic steel and modified 9Cr-1Mo steel were carried out at different temperature and different load by using Spranktronics indentation creep testing machine. The microstructural examinations and phase analysis were carried out with the help of an image analyser. The microstructural examinations and EDAX were taken by SEM. Hardness measurements were done using a Vickers hardness tester by applying 500g load with dwell time of 15 s. The plates of two alloy steels were first normalised at 950°C for 2hrs. Indentation creep tests for 2.25Cr-1Mo ferritic steel were carried out at different temperature (4800C, 5000C, 5200C) and different load (10 Kg, 20Kg). The indentation creep test of modified 9Cr-1Mo ferritic steel was done at 5200C with a load of 10kg. The results highlight that creep of 2.25Cr-1Mo ferritic steel was load and temperature dependent, larger load and higher temperature resulted in a larger creep deformation. It was also found that higher load and higher temperature caused higher creep rate .Creep rate for all temperature and loads had a maximum value at the initial creep stage and it decreased dramatically after a period of holding time. The value of activation energy was found to be 95kJ/mol. From the microstructural analysis it was revealed out that with increase in temperature there is a decline in creep strength because there is a reduction in the amount of bainite with the progress of temperature. Modified 9Cr-1Mo steel shows best compressive behaviour than 2.25Cr-1Mo.Because it contains more amount of alloying element.

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49

Nath, Chirag Ranjan, and Sanup Kumar Panda. "Fatigue Life Estimation of Pre-corroded 7075 Aluminium Alloy." Thesis, 2012. http://ethesis.nitrkl.ac.in/3211/1/Final_B.Tech_Thesis.pdf.

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Heterogeneous microstructures of aluminium alloys such as 7075, which are extensively used in aircraft structures, render them highly susceptible to corrosion. Corrosion can adversely affect aircraft structural integrity since fatigue cracks can nucleate from corrosion pits and grow at an accelerated rate in corrosive environment. During its service life, an aircraft structure typically experiences corrosion between flights and fatigue loading during flight, thus pointing to the need for quantifying the effects of ‘prior corrosion’ on fatigue behaviour. This phenomenon, termed corrosion-fatigue, has an especially detrimental effect on the longevity of structures and leads to the premature failure of a component in service. In this work the fatigue life of as-received (pristine) specimens were determined at various stress levels. Specimens were also corroded in two conditions viz. 3.5% NaCl for 50 h and applying variable potential at a constant scan rate in same 3.5% NaCl solution. The fatigue life of pre-corroded specimens were also determined and correlated with that of the as-received specimens. Scanning Electron Microscopy was conducted for observation and analysis of fracture surface and corrosion pits. The average pit size, depth and density were also calculated. It was confirmed that corrosion pits and constituent particles act as preferential sites for crack nucleation. Fine non-critical cracks on the corroded surface were also observed.

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50

Gupta, Mukul, and Himanshu Baghel. "Reduction and Swelling Behaviour of Fired Iron Ore Pellets." Thesis, 2012. http://ethesis.nitrkl.ac.in/3268/1/Final_Edit.pdf.

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The present project work on “Reduction and Swelling Behaviour of Fired Iron Ore Pellets” was undertaken with a view to promote the effective utilization of iron ore and coal fines in sponge iron making. Presently, India has become the world leader in sponge iron production and the production of steel by DR-EAF route is increasing day by day. In the present project work, the effect of addition of concentrated sugarcane juice binder on the physical properties of fired iron ore pellets was investigated. The crushing strength and drop number were found to be maximum at 2% binder addition, followed by a decrease with further increase in binder concentration. A reverse trend was observed in the case of porosity, i.e. porosity of fired pellets increased with rise in binder concentration from 2% to 6%. The pellets fired at 13000C were processed for reduction and swelling studies in different types of coal. The degree of reduction of fired iron ore pellets increased with increase of reduction temperature and time up to the range studied. The extent of swelling in fired iron ore pellets during their production increased with increase of reduction time, most probably due to the structural changes and fibrous growth of iron particles. SEM images of few reduced iron ore pellets were also taken.

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Dissertations / Theses on the topic 'Metallurgical and Materials Science'

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