<p>A high temperature electrochemical technique has been developed, to continuously monitor the oxygen activity in iron based melts.</p> <p>The electrochemical cell used, can be represented as:</p> <p>Mo | Cr(s) -Cr₂O₃(s) | Calcia stabilised zirconia | Fe-M-O(ℓ) |Mo-ZrO₂, Mo cermet</p> <p>The electrolyte was in the form of a crucible to hold the metallic melt.</p> <p>The standard free energy change for the reactions:</p> <p>FeNb₂O₆(s) ⇆ 2NbO₂(s) + Fe(ℓ) + 2O lw/o</p> <p>FeNb₂O₄(s) ⇆ Al₂O₃(s) + Fe(ℓ) + O lw/o</p> <p>and the influence of manganese content of the melt on the oxygen activity for the equilibrium:</p> <p>(Fe1-x, Mnx)O.Al₂O₃(s) ⇆ Al₂O₃(s) + (1-x)Fe(ℓ) + xMn lw/o + O lw/o</p> <p>were determined using the technique at a temperature range of 1550 - 1600ºC.</p> <p>The results can be summarized as:</p> <p>(a) ΔGºT[FeNb₂O₆(s) - NbO₂(s)] = 105870 - 42.64ºT (±600) cal/mole FeNb₂O₆ [1550ºC - 1600ºC]</p> <p>(b) ΔGºT[FeAl₂O₄(s) - Al₂O₃(s)] = 49910 - 21.50 T(±300) cal/mole FeAl₂O₄ [1550ºC - 1600ºC]</p> <p>(c) Increasing the manganese content in the melt decreases the value of logh₀ in equilibrium with the transition reaction.</p> <p>The nature of the deoxidation inclusions of the liquid systems Fe-Nb-O, Fe-Al-O and Fe-Al-Mn-O were studied by X-ray analysis and their morphology by scanning electron microscopy. In the Fe-Nb-O system the inclusions were identified as NbO₂ and FeNb₂O₆ and appeared to form agglomerates of small crystallites.</p> <p>In the Fe-Al-O and Fe-Al-Mn-O the inclusions were identified as Al₂O₃ clusters along with FeAl₂O₄ or (Fe,Mn) Al₂O₄ respectively. The thermodynamic data obtained by the present technique are believed to be of high accuracy and the method significantly contributes in the studies of complex deoxidation systems at steelmaking temperatures.</p> <p>An attempt was made to use the present electro-chemical technique in studying the liquid Fe-Ti-O system at high oxygen potentials. Further research is suggested to fully resolve the results.</p> / Doctor of Philosophy (PhD)

<p>The thermodynamics of rare earth-oxygen-sulfur systems was studied at high temperatures using the following four types of oxygen concentration cells.</p> <p>Type I Cells:</p> <p>[equation removed]</p> <p>Type II Cells:</p> <p>[equation removed]</p> <p>Type III Cells:</p> <p>[equation removed]</p> <p>Type IV Cells:</p> <p>[equation removed]</p> <p>Type I and II cells were used to yield the standard free energy changes corresponding to the reaction</p> <p>[equation removed]</p> <p>at two different sulfur partial pressures. Type III cells were used to determine the standard free energy changes for the reaction.</p> <p>[equation removed]</p> <p>Type IV cells were used to determine the standard free energy changes for the reaction</p> <p>[equation removed]</p> <p>Combining the experimental results for the above three-reactions with the values of ΔGfº for Cu₂S and Ag₂S, the standard free energies of formation of La₂O₂SO₄, Pr₂O₂SO₄, Nd₂O₂SO₄, Sm₂O₂SO₄, Eu₂O₂SO₄, Gd₂O₂SO₄, La₂O₂S, Pr₂O₂S, Nd₂O₂S, Sm₂O₂,S, Eu₂O₂S, Gd₂O₂S, Y₂O₂S and Ce₂O₂S were determined at high temperatures. In addition, the standard free energy changes for oxidation of Tb₂O₂S and Dy₂O₂S to Tb₂O₂SO₄ and Dy₂O₂SO₄ were determined.</p> <p>The above data were used to construct the phase stability diagrams for the rare earth-oxygen-sulfur systems at high temperatures.</p> / Doctor of Philosophy (PhD)

<p>This thesis presents the results of a study of two aspects of peritectic alloy solidification: 1. an experimental<br />and theoretical study of the phenomenon of banding (alternate<br />deposition of layers of primary (α) and peritectic (β) phases)<br />during plane front solidification and 2. a theoretical study<br />of microsegregation during the non-isothermal diffusion<br />controlled peritectic transformation in an alloy system where<br />the solute diffusivities differ greatly, ie. Fe-C-Mn.</p> <p>Plane front solidification experiments using Sn-Cd<br />alloys produced specimens which solidified as metastable α<br />phase. The β phase was observed in only those specimens which<br />were purposely disturbed during solidification; the α phase<br />did not re-nucleate at the interface once β phase<br />solidification was established. Banding was observed in one of<br />these specimens, however, the α phase never entirely<br />disappeared from the interface. Mathematical model predictions<br />of the growth transient of the β phase and nucleation<br />considerations showed that the α phase would not be renucleated<br />at the β/liquid interface. It is thus expected that<br />when banding occurs in Sn-Cd peritectic alloys, α is never<br />completely removed from the growth front.</p> <p>The treatment of microsegregation during the non-isothermal<br />diffusion controlled peritectic transformation used<br />in this work exposed several aspects of the problem which are<br />obscured by some of the more sophisticated mathematical<br />treatments of this problem; the transformation was modelled as<br />a series of non-isothermal steps. For the binary Fe-C system,<br />these calculations showed that, while cooling rate and solute<br />diffusivity are important, closure of the δ-ferrite/austenite<br />two phase field ultimately determines the temperature at which<br />the transformation ends and what phases exist at that point.<br />In the ternary case, Fe-C-Mn, the combined influence of<br />constitutional and diffusional solute interactions promotes<br />the following: 1. the concentration gradient of the fast<br />diffusing solute in austenite is minimized with a<br />corresponding greater segregation of the slow diffusing solute<br />in all phases, compared to predictions based on no diffusion<br />in the austenite or complete diffusion in all phases. 2.<br />diffusional solute interaction may increase or decrease the<br />effect of constitutional solute interaction on<br />microsegregation. 3. At the liquid/austenite interface, the<br />possibility of metastable austenite solidification or<br />nucleation of δ-ferrite exists throughout the transformation.</p> / Doctor of Philosophy (PhD)

Структура магистерской диссертации включает в себя введение, три главы, заключение, список использованных источников и приложения. В первой главе рассмотрены аспекты инвестиционной деятельности, общая характеристика инвестиционных проектов и влияние реальных инвестиций на деятельность предприятий. Во второй главе проанализированы отрасль черной металлургии и влияние инвестиционной деятельности на финансовое состояние коммерческого предприятия. В третьей главе произведена оценка финансовой и инвестиционной деятельности предприятий черной металлургии после завершения сделок по слиянию и поглощению. В заключении сформированы основные выводы. / The structure of the master's thesis includes an introduction, three chapters, a conclusion, a list of references and applications. The first chapter deals with aspects of investment activity, general characteristics of investment projects and the impact of real investment on the activities of enterprises. The second chapter analyzes the ferrous metallurgy industry and the impact of investment activity on the financial condition of a commercial enterprise. In the third chapter, an assessment was made of the financial and investment activities of ferrous metallurgy enterprises after the completion of mergers and acquisitions. In conclusion, the main conclusions are formed.

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Depuis de nombreuses années, la société est de plus en plus consommatrice d’énergie. Cette augmentation va de pair avec les progrès d’accès à l’énergie, une croissance démographique mondiale continue, l’amélioration de la qualité de vie et le développement de nouvelles technologies. D’après l’agence internationale de l’énergie, une hausse de cette consommation de l’ordre de 30% est prévue d’ici 2040. Près de 40% de cette consommation additionnelle pourrait être satisfaite par l’électricité ; ce qui aura un fort impact sur la distribution d’énergie. Pour la société Schneider Electric, spécialiste mondial de la gestion de l’énergie et des automatismes, la distribution d’énergie électrique est principalement assurée par des barres et des fils en cuivre. Ce métal est très largement utilisé pour de nombreux organes de raccordement, appelés objets 2D, qui servent à connecter et déconnecter les appareils. Le principal problème de ces éléments est leur dissipation d’énergie par effet Joule lors du passage du courant électrique. Ce travail de thèse a ainsi consisté à l’élaboration et l’étude d’une nouvelle génération de conducteur électrique et/ou thermique plan (2D) dans l’objectif de palier à ce problème. Pour cela, une nouvelle méthodologie de fabrication de matériaux composites Cu/C 2D a été développée. Elle est composée d’une étape de pré-traitement des poudres, d’une nouvelle technique de mélange et d’une mise en forme du matériau par compression uniaxial à chaud. Différents types de poudres métalliques (cuivre dendritique et cuivre plaquette) et poudres carbonées (graphite, graphène multi-couches, oxyde de graphène) ont été étudiés. L’orientation du renfort au sein de la matrice métallique et l’interface entre ces deux composants ont été optimisées. Cette méthodologie, associée aux caractérisations physico-chimiques des matériaux et à des modèles théoriques, a permis de mieux comprendre les paramètres clés pour l’obtention d’un matériau possédant des propriétés physiques améliorées. Ainsi, les matériaux Cu/C 2D élaborés au cours de cette thèse présentent, suivant le type renfort, une augmentation des propriétés mécaniques (allant de 36% à 120% pour la dureté Vickers), une amélioration de la conductivité thermique (variant de 8% à 56%) et une résistivité électrique cohérente en regard des propriétés du cuivre, matériau de référence. / Since several years, society has become more and more energy-consuming. This increase goes hand in hand with the progress of access to energy, continuous world population growth, the improvement of life quality and the development of new technologies. According to the International Energy Agency, an increase of this consumption of the order of 30 % is planned before 2040. About 40 % of this additional consumption could be satisfied by electricity; what will have a strong impact on the distribution of energy. For the company Schneider Electric, world specialist of the management of energy and automatisms, the distribution of electrical energy is mainly assured by copper bars and wires. This metal is widely used for many connecting organs, called 2D objects, which are used to connect and disconnect devices. The main problem of these elements is their dissipation of energy by Joule effect when passing electric current. Thus, this thesis work consisted in the elaboration and study of a new generation of electrical and/or thermal plane (2D) conductor in the objective to overcome this problem. To this end, a new methodology for manufacturing Cu/2D C composite materials has been developed. It consists of a powders pre-treatment step, a new mixing technique and a shaping of the material by uniaxial hot compression. Various types of metal powders (dendritic copper and copper platelet) and carbonaceous powders (graphite, multi-layer graphene, graphene oxide) were studied. The orientation of reinforcement within the metal matrix and the interface between these two components have been optimized. This methodology, combined with physico-chemical characterizations of materials and theoretical models, provided a better understanding of the key parameters for obtaining a material with improved physical properties. Thus, the Cu/2D C materials developed during this thesis show, depending on the type of reinforcement, an increase in mechanical properties (from 36% to 120% for the Vickers hardness), an improvement in thermal conductivity (from 8% to 56%) and an electrical resistivity consistent with the properties of copper, the reference material.

This thesis investigates aspects of the technology and organisation of Early Bronze Age (EBA) Cycladic copper production based primarily on an analytical examination of metallurgical remains identified in two different contexts: the slag heaps of Seriphos and the settlement of Daskaleio-Kavos on Keros. The Cyclades show intense prominence during this period and the identification of local metal production raises important archaeological questions. A geological reconnaissance on Seriphos established the existence of copper minerals on the island. Five occurrences were identified, sampled and characterised. The slag heaps of Kephala and Phournoi on Seriphos were dated to the third millennium BC by thermoluminescence of furnace fragments. Examination of a substantial suite of slags from these sites showed that unalloyed copper was produced estimates of several key process parameters for the smelting operations were obtained. No indications for other metallurgical activities aside from smelting were recognised. A preliminary study of material from the still undated Avessalos slag heap was also undertaken. Analyses of the Daskaleio-Kavos finds gave evidence for two copper-producing activities, resulting in unalloyed and arsenical copper metal, respectively. Identification of a single litharge specimen raises the possibility that cupellation was additionally carried out. The copper slag heaps identified on Seriphos conform to a pattern known also from neighbouring Kythnos, where relatively large-scale EBA copper smelting is attested, isolated from any known contemporaneous settlements and within a metal-rich area. The dispersed distribution of these slag heaps and several technological characteristics suggest a largely uncentralised production. The finds from Daskaleio-Kavos showed that some small-scale metal production was also carried out within some of the settlements these activities show several differences compared to those associated with the western Cycladic slag heaps. The thesis highlights the importance of appropriate technological studies in understanding the role and organisation of copper metallurgy in the EBA Cyclades.

Powder metallurgy (PM) is usually used in manufacturing parts with complex geometries, such as gears and structural parts. The main attractions of PM are the high rate of material utilization, environmental friendliness of production, economic advantages (especially for complex geometries), and possibility of obtaining lighter components. To find a wide range of applications and compete with regular steel gears, PM gear transmissions should have good transmission efficiency and wear properties. Furthermore, they should have low contact noise and adequate surface fatigue properties. Because of the porosity structure of PM gears both on gear flanks and in the body, the friction and wear properties of PM gear flank contacts differ somewhat from those of regular steel gears.    This doctoral thesis examines the efficiency and wear properties of PM gears. Paper A compares the wear, friction, and damage mechanism properties of two sintered gear materials with those of a standard gear material. Paper B deals with the gear mesh torque loss mechanism of PM and regular steel gears by combining both pin-on-disc frictional and FZG efficiency tests. Paper C comparatively examines the efficiency of PM and regular steel gears by conducting FZG gear efficiency tests. Paper D focuses on the wear and friction properties of PM and regular steel gear materials treated using the triboconditioning process. Paper E studies the friction and wear properties attributable to different pore sizes in PM gear materials.    The results indicate that regular steel meshed with PM gear material and PM meshed with PM gear material are good candidate combinations for gear transmissions. This is because the porosities of PM material can lower the friction coefficient while the wear rate can be the same as or even better than that of regular steel contacts. The triboconditioning process enhances the wear resistance and reduces the friction coefficient of the PM gear material. The friction and wear coefficients of PM meshed with PM gear material display increasing trends with increasing pore size. The friction and wear coefficients of regular steel meshed with PM gear material display decreasing trends with increasing pore size. / <p>QC 20160523</p>

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