The Mo-Ni-Re system is one of the important subsystems of the Ni based superalloys engineered for use in high temperature applications. Considering the contradictions among previously reported information, the present study was devoted to the complete experimental determination of the phase equilibria in the Mo-Ni-Re system, structural characterization of its intermetallic phases and thermodynamic modeling of the system with the help of the CALPHAD method. The experimental investigation of phase equilibria was carried out with the help of equilibrated alloys and phase diagrams of the Ni-Re and Mo-Ni-Re system (at 1200°C and 1600°C) were proposed. In comparison with previous investigations, the Ni-Re phase diagram determined during the present study showed significant difference in terms of homogeneity domains, freezing ranges and peritectic reaction temperature. The 1200°C isothermal section of the Mo-Ni-Re system proposed during the present study showed large extension of the Mo-Re σ phase and Mo-Ni δ phase in the ternary region. In addition, presence of two previously unknown ternary phases was also observed. The isothermal section of the Mo-Ni-Re system at 1600°C also showed large extension of σ phase in the ternary region whereas extension of the Mo-Re χ phase in both isothermal sections was restricted to narrow composition range. The presence of the ternary phases observed in the 1200°C isothermal was not evidenced in 1600°C isothermal section. On the other hand, partial investigations of phase boundaries in the Mo-Ni and Mo-Re binary systems and determination of liquidus projection of the Mo-Ni-Re system was also carried out. The liquidus projection of the Mo-Ni-Re system proposed during present study also showed largely extended primary crystallization fields of the Mo-Re σ phase and Re solid solution in the ternary region. Since isothermal sections of the Mo-Ni-Re system showed largely extended homogeneity domain of σ, structural characterization of the Mo-Ni-Re σ with particular emphasis on determination of site occupancy trends as a function of composition was carried out by combined Rietveld refinement of the X-ray and neutron diffraction data. The experimental results gathered during the present study along with the information available in the literature were used as input for thermodynamic modeling of the Mo-Ni-Re system. The thermodynamic description of the Mo-Re system was taken from literature whereas thermodynamic modeling of the Mo-Ni, Ni-Re and Mo-Ni-Re system was carried out during the present study with the help of the CALHAD method.Keywords: Mo-Ni; Mo-Re; Ni-Re; Mo-Ni-Re; phase diagram; isothermal section; structural characterization; thermodynamic modeling; CALPHAD method

Solid oxide fuel cells (SOFCs) are promising power generation devices due to its high efficiency and low pollutant emissions. SOFCs operate with a wide range of fuels from hydrogen (H2) to hydrocarbons, and are mainly intended for stationary power generation. Compared to combustion systems, SOFCs have significantly lower environmental impacts. However, the full scale commercialization of SOFCs is impeded by high cost and problems associated with long-term performance and durability. The cell performance can be affected by various internal losses, involving cathode, anode and electrolyte. Anodic losses make a significant contribution to the overall losses, practically in anode-supported cells. Therefore, it is desirable to reduce the anodic losses in order to enhance the overall cell performance. Knowledge of the actual elementary reaction steps and kinetics of electrochemical reactions taking place on the anode is critical for further improvement of the anode performance. Since H2 and carbon monoxide (CO) are the primary reforming products when hydrocarbons are used as SOFC fuels, investigation of electrochemical reactions involving H2 and CO should provide a better understanding of SOFC electrochemical behavior with hydrocarbon feeds. However, still exist uncertainties concerning both H2 and CO electrochemical reactions. The overall objective of this research is to investigate the mechanistic details of H2 and CO electrochemical reactions on SOFC anodes. To achieve this objective, Ni/YSZ pattern anodes were used in the experimental study and as model anodes for the simulation work due to their simplified 2-D structure. The Ni/YSZ pattern anodes were fabricated using a bi-layer resist lift-off method. Imaging resist nLOF2035 and sacrificial resist PGMI SF11 were found to be effective in the bi-layer photolithographic process. Suitable undercut size was found critical for successful pattern fabrication. A simple method, involving taking microscopic photographs of photoresist pattern was developed, to check if the undercut size is large enough for the lift-off; semi-circle wrinkles observable in photographs indicate whether the undercut is big enough for successful pattern anode fabrication. The final product prepared by this method showed straight and clear Ni patterns. A systematic study was performed to determine the stable conditions for Ni/YSZ pattern anode performance. The microstructure and electrochemical behavior changes of the pattern anode were evaluated as a function of Ni thickness, temperature and H2O content in H2 environment. Ni/YSZ pattern anodes with 0.5 µm thick Ni were tested in dry H2 at 550°C without significantly changing the TPB line. Ni/YSZ pattern anodes with Ni thickness of 0.8 µm were tested at 550°C under dry and humidified H2 (3-70% H2O) conditions without TPB line change. For 0.8 µm thick patterns, the TPB length showed pronounced changes in the presence of H2 with 3-70% H2O at 700°C. Significant increase in TPB length due to hole formation was observed at 800°C with 3% and 10% H2O. Ni/YSZ pattern anodes with 1.0 µm thick Ni were stable in H2 with 3% H2O in the range 500-800°C, with only slight changes in the TPB line. Changes of TPB line and Ni microstructure were observed in the presence of 3-70% H2O above 700C. Stabilization of the pattern anode performance depends on temperature. To accelerate stabilization of the cell, pre-treatment of the cell in H2 with 3% H2O for ~22 hrs at 750°C or 800°C could be performed. In addition, comprehensive data sets for H2 and CO electrochemical oxidation reactions on Ni/YSZ pattern anodes were obtained under stable test conditions. For the H2/H2O system, the polarization resistance (Rp) increases as temperature, overpotential, H2 partial pressure, TPB length decreases. Rp is also dependent on H2O content. When the H2O content is between 3% and 30-40%, Rp decreased with increasing H2O content. However, Rp is less affected with further increases in H2O content. For the CO/CO2 system, polarization resistance depends on partial pressure of CO and CO2, temperature and overpotential. Moreover, the polarization resistance decreases when the partial pressure of CO2 and temperature increase. The partial pressure of CO has a positive effect on the polarization resistance. The polarization resistance decreases to a minimum when the overpotential is 0.1 V. For both H2 and CO electrochemical oxidations, charge transfer reactions contribute to the rate limiting steps. A 1-D dynamic SOFC half-cell model considering multiple elementary reaction kinetics was developed. The model describes elementary chemical reactions, electrochemical reactions and surface diffusion on Ni/YSZ pattern anodes. A new charge transfer reactions mechanism proposed by Shishkin and Ziegler (2010) based on Density Functional Theory (DFT) was investigated through kinetic modeling and pattern anode experimental validation. This new mechanism considers hydrogen oxidation at the interface of Ni and YSZ. It involves a hydrogen atom reacting with the oxygen ions bound to both Ni and YSZ to produce hydroxyl (charge transfer reaction 1), which then reacts with the other hydrogen atom to form water (charge transfer reaction 2). The predictive capability of this reaction mechanism to represent our experimental results was evaluated. The simulated Tafel plots were compared with our experimental data for a wide range of H2 and H2O partial pressures and at different temperatures. Good agreements between simulations and experimental results were obtained. Charge transfer reaction 1 was found to be rate-determining under cathodic polarization. Under anodic polarization, a change in rate-limiting process from charge transfer reaction 1 to charge transfer reaction 2 was found when increasing the H2O partial pressure. Surface diffusion was not found to affect the H2 electrochemical performance.

Directionally solidified Rene 80 (DS R80) and polycrystalline Inconel 738(IN 738) Superalloys were tested in thermo-mechanical fatigue (TMF) over the temperature range of 500-900°C and plastic strain range from 0.1 to 0.8% using a DSI Gleeble thermal simulator. Thermo-mechanical testing was carried out on the parent material (baseline) in the conventional solution treated and aged condition (STA), as well as gas tungsten arc welded (GTAW) with an IN-738 filler, followed by solution treatment and ageing. Comparison of the baseline alloy microstructure with that of the welded and heat treated alloy showed that varying crack initiation mechanisms, notably oxidation by stress assisted grain boundary oxidation, grain boundary MC carbides fatigue crack initiation, fatigue crack initiation from sample surfaces, crack initiation from weld defects and creep deformation were operating, leading to different “weakest link” and failure initiation points. The observations from this study show that the repaired samples had extra crack initiation sites not present in the baseline, which accounted for their occasional poor fatigue life. These defects include lack of fusion between the weld and the base metal, fusion zone cracking, and heat affected zone microfissures.

I was interested in history while I was in school and I pursued this interest as a history student at the University of Tabriz where I graduated in history in 1973. Apart from a major part of our studies in history, which were about the Iranian and foreign dynasties, we had to study a great deal about the lives of individual Kings; but hardly any space was allocated to the history of social and political movements in Iran. The names of patriots and political thinkers such as K̲h̲iyābānī were not, for political reasons, mentioned. These movements, however, no matter how briefly they were covered in our history books, were still able to arouse my curiosity and interest in discovering more about these movements and their leaders. In 1977 I decided to undertake research in modern history. My decision coincided with social and political upheavals in Iran which resulted in the revolution of 1979. This by itself strengthened my conviction that we must study and understand our history in its particular social and political content. That is to say revolts and revolutions are not something which appear suddenly, but are the product and result of historical developments in which peoples, as a living force, have taken part. These revolts and revolutions are, in fact, the manifestations of longstanding social injustices and oppressions which have been imposed on the people by despotic kings, irresponsible governments and reactionary rulers. In recent social upheavals of Iran I witnessed how thousands of sincere people and patriots gave their lives and wished to free their country from age old backwardness. This reflected the continuation of the constitutional revolution and K̲h̲iyābānī's uprising (1910-1920). Since my grandfather Mīrzā Muḥammad Tagī Ṭabāṭabā'ī K̲h̲ātambak̲hs̲h̲ was involved in the constitutional revolution and K̲h̲iyābānī's uprising and I naturally had heard a lot about K̲h̲iyābānī through my relatives, both personal curiosity and historical interest made me choose K̲h̲iyābānī as the subject of my research. Some books and articles have been written about K̲h̲iyābānī which are either very superficial or based on misrepresentation. They are superficial because they have not attempted to explain why and how K̲h̲iyābānī's uprising began and the reasons for its success and failure and the role of central government in Tehran in this event is not examined. K̲h̲iyābānī's original speeches and works have not been studied in depth. The opposition to K̲h̲iyābānī's uprising has misrepresented him in different ways. The most striking aspect of this is the fact that he has been accused by his political opponents over and over again of being a "separatist". Some historians have even either spelt K̲h̲iyābānī's name wrongly or copied the errors of others. I came to Edinburgh and was accepted as a postgraduate student in October 1979, and then went to London where I studied and examined the British Foreign office archives and also studied in the British Library. Through the Edinburgh University Library I received some books and newspapers in Russian, French, English, Persian and Azari. Three times I travelled to Iran where I could consult the Iranian Parliamentary documents, newspapers, books and interviewed a number of Iranians who either participated in or had valuable memories of K̲h̲iyābānī's uprising. It is hoped, therefore, that the present study will shed a great deal of light upon a hitherto much-neglected episode in modern Iranian history.

Nowadays, the development of novel materials involves diverse branches of science as a consequence of the new requirements imposed by modern society. This includes aspects ranging from the optimization of the manufacturing processes to the durability of the materials themselves. Ideally, some synergism should exist between the durability, the properties of interest in the material. Although metals in their pure state are often desired, the best properties or combination of properties often cannot be satisfactorily achieved with a single metal. In these situations, the desired properties can be attained by the formation of alloys of these metals with others. Ni-Co alloys are no exceptions and so have received considerable attention especially in microsystem technology due to the magnetic properties of cobalt and the corrosion and wear resistance of nickel. Moreover, this interest has been further stimulated by its use in the manufacture of sensors, magnetic devices, microrelays, inductors, actuators, memory devices and hard drives. The fabrication of these alloys (particularly coatings) via electroplating has been shown to be techno-economically feasible in comparison with other processes: capability of high volume production, low cost and the ability to coat thin layers on non-planar substrates. In addition, the materials fabricated by this technology exhibit excellent characteristics such as refined grain structure, smoothness, low residual stress and coercivity, etc., making them advantageous to materials produced by other physical methods of deposition. Nevertheless, one of the biggest problems faced during the formation of Ni-Co alloys is its anomalous behavior whereby cobalt preferentially deposits over nickel under most conditions, even when the Ni(II) concentration is significantly higher than that of Co(II). This problem has complicated the prediction and control of the metal composition in these alloys during their production and as a consequence the ability to obtain the desirable properties associated with high nickel content. Although this problem is not recent, the studies that have been carried out so far to analyze this system have not always been as comprehensive as they could be in terms of the experimental conditions investigated or the reaction mechanisms and mathematical models developed to describe its behavior. Consequently, the origin of this behavior is still not completely understood. Thus, this work presents a contribution in terms of the analysis of the reaction mechanisms for single metal deposition of nickel and cobalt and for the formation of Ni-Co alloys in sulphate media with the intention of gaining a better understanding of the phenomena controlling the anomalous behavior of this system. Analyses of the single metal deposition of nickel and cobalt are first carried out to better understand their reaction mechanisms. Such an approach should allow the contributions of the reduction of each metal ion and interactions between the two systems during alloy co-deposition to be more clearly understood. In order to analyse the aforementioned systems, both steady state and transient techniques are employed. Among these techniques, electrochemical impedance spectroscopy (EIS) is employed since it is a robust and powerful method to quantitatively characterize the various relaxation phenomena occurring during the electrodeposition of metals. The experimental data acquired from this technique are analyzed with comprehensive physicochemical models and the electrochemical processes are quantified by fitting the models to these data to determine the kinetic parameters. During the development of the physicochemical models, several assumptions (e.g. neglect of convection, homogeneous reactions and single electron-transfer steps) made in former models are relaxed in order to investigate their combined impact on the predicted response of the system. Estimates of the kinetic parameters determined by EIS for the deposition of the single metals reveals that the first step of Co(II) reduction is much faaster tha the corresponding step of Ni(II) reduction. Some limitations of the EIS technique (i.e. analysis at high overpotentials) are exposed and compared in the case of the nickel deposition using linear sweep voltammetry (LSV). Likewise, physicochemical models accounting for most of the important phenomena are derived and fitted to experimental data. Ni-Co alloy formation is analyzed using LSV and steady state polarization experiments for different pH, current density and electrolyte composition. Current efficiencies for metal depsoition and alloy composition are also evaluated. To date, no experimental study considering all these variables has been reported in the literature. Then a steady state model is presented to describe the electrode response during alloy formation and used to provide insight into the anomalous behavior of this system. This model is based on information obtained from previous studies reported in the literature and from the current research. After being fitted to the experimental data, the model reveals that the anomalous behavior observed for this alloy is likely caused by the much faster charge-transfer of Co(II) reduction than that of Ni(II) reduction and not by other previously proposed mechanisms such as competition between adsorbed species for surface sites, formation of aqueous hydroxides (MeOH+) or mixed intermediate species (NiCo(III)ads) on the surface of the electrode.

Sungur Bey Mosque and the Tomb adjacent to it were built in Nigde in the first half of the 14th century. In many respects, the Mosque is a traditional Anatolian building in terms of its architecture and decoration. Nevertheless, some of the architectural forms observed on the Mosque point to possible foreign interactions. The aim of this thesis is to take a critical look at the sources of the foreign architectural forms observed on the Sungur Bey Mosque and to question how such interactions could be possible in the 14th century Anatolia. In this context, the foreign architectural elements of the Mosque are compared vis-a-vis contemporary examples from Europe, Eastern Crusader States, Cyprus, Armenia and Anatolia. In addition, Crusades, trade relations and traveling artists are considered among possible interactions which could be influential in the transmission of these architectural forms. Thus, Sungur Bey Mosque is evaluated in a different viewpoint, which considers historical events and a number of possible interactions.

Ethylene hydrogenation on Ni(111) / equilibrium geometry calculations for Ni2 dimer, Ni13 and Ni55 nanoclusters / and ethylene adsorption on Ni(100), Ni(111), Ni2, and Ni13 were studied quantum mechanically by means of energetic and kinetic differences. Ethylene hydrogenation on Ni(111) was simulated by use of DFT/B3LYP/6-31G** formalism. The reaction mechanism was mainly composed of three elementary steps. Firstly, ethylene adsorption on bare Ni(111) surface was performed. Second step and third step were the formation of ethane from adsorbed ethylene by use of two types of hydrogen atom, bulk and surface. During the hydrogenation reaction of ethylene on Ni(111), bulk hydrogen atom, representing for hydrogen atoms emerging from the bulk of Ni metal, was determined to be rather reactive than surface hydrogen atom, as suggested by experimental findings. Small Ni clusters, Ni2 and Ni13, were investigated by means of DFT/B3LYP/modified-6-31G**. Equilibrium geometry calculations resulted in Ni2 binding energy of 1.078eV/atom, showing good agreement with experimental value. Ni13 was found to have a structure of icosahedral, suggested experimentally, and binding energy of 2.70eV/atom. Ni55 was, also, studied by semi-empirical PM3 formalism, resulting in expected icosahedral structure. Finally, DFT/B3LYP/6-31G** investigation of ethylene adsorption was performed on Ni(111), Ni(100) and Ni13 surfaces which were selected according to their nickel atom coordination numbers of 9, 8 and 6, respectively. Comparison of adsorption energies of -18.00kcal/mol, -31.4kcal/mol and -43.42kcal/mol, respectively, indicated that the change in energies for ethylene adsorption on different nickel surfaces was directly proportional to coordination number of the nickel atoms constructing the surfaces.

Im Legierungssytem Ni-Mn-Ga tritt bei Zusammensetzungen nahe der stöchiometrischen Zusammensetzung Ni2MnGa der magnetische Formgedächtniseffekt auf. Darunter versteht man die Dehnung durch Bewegung von Zwillingsgrenzen im Magnetfeld. Einkristalle aus Ni-Mn-Ga mit einer tetragonalen 5M-Martensitstruktur zeigen magnetisch erzeugbare Dehnungen von bis zu 6 %. Diese großen Dehnungen verbunden mit der schnellen Schaltfrequenz von Magnetfeldern machen den Effekt interessant für technische Anwendungen z. B. als Aktoren. Derartige Einkristalle sind schwierig und teuer herzustellen, weshalb für technische Anwendung Polykristalle von Interesse sind. Diese lassen sich im Allgemeinen leichter und preiswerter herstellen. Um den magnetischen Formgedächtniseffekt in Polykristalle einzustellen, werden grobkörnige, texturierte Proben mittels des Verfahrens der gerichteten Erstarrung hergestellt. Die Gefügeuntersuchungen erfolgen mit metallographischen Schliffen und die Kornorientierungen werden mit der EBSD-Technik bestimmt. Um das Gefüge zu vergröbern, werden Glühungen nach einer aufgebrachten Warmverformung untersucht. Zur Verringerung der für die Bewegung der Zwillingsgrenzen notwendigen Spannung (Zwillingsspannung) werden die Proben im Druckversuch mechanisch trainiert. Dabei kann die Zwillingsspannung teilweise unter die magnetisch erzeugbare Spannung auf die Zwillingsgrenzen (Magnetospannung) abgesenkt werden. Eine weitere Absenkung der Zwillingsspannung wird durch eine plattenförmige Probengeometrie mit Dicken im Bereich der Korndurchmesser erreicht. An derartigen Proben wird magnetisch rückstellbare freie Dehnung durch Zwillingsgrenzenbewegung erzielt.

As a global climate phenomenon, the El Ni??o-Southern Oscillation (ENSO) involves the coupling of the ocean and the atmosphere. Most climate prediction studies have, by far, only investigated the teleconnections between global climatic anomalies and the ???surface??? predictors of ENSO. The prediction models resulting from these studies have generally suffered from inadequate, if not the lack of, skill across the so-called boreal ???spring barrier???. This is illustrated in the first part of this thesis where the applicability of the SOI phase for long-lead rainfall projections in Australia is discussed. With the increasing availability of subsurface ocean temperature data, the characteristics of the Pacific Ocean???s heat content and its role in ENSO are now better understood. The second part of this thesis investigated the predictability of ENSO using the thermocline as a predictor. While the persistence and SST-based ENSO hindcasts dropped in skill across the spring barrier, the thermocline-based hindcasts remained skillful even up to a lag of eighteen months. Continuing on the favorable results of ENSO prediction, the third part of this thesis extended the use of the thermocline in the prediction of Australia???s rainfall and streamflow. When compared to models that use ???surface??? predictors, the model that incorporated thermocline information resulted in more skillful projections of rainfall and streamflow especially at long lead-times. More importantly, significant increases in skill of autumn and winter projections demonstrate the ability of the subsurface ocean to retain some climatic memory across the predictability barrier. This resilience can be attributed to the high persistence of the ocean heat content during the first half of the year. Based on weighting, the model averaging exercise also affirmed the superiority of the ???subsurface??? model over the ???surface??? models in terms of streamflow projections. The encouraging findings of this study could have far-reaching implications not only to the science of ENSO prediction but also to the more pragmatic realm of hydrologic forecasting. What this study has demonstrated is an alternative predictor that is suitable for the long range forecasting of ENSO, rainfall and streamflow. With better hydrologic forecasting comes significant improvement in the management of reservoirs which eventually leads to an increase in the reliability and sufficiency of water supply provision.

Les poudres d'alliages aluminium-nickel produites par atomisation peuvent être traitées pour préparer du nickel de Raney, un catalyseur utilisé dans de nombreux procédés industriels. L'activité du catalyseur dépend fortement du déroulement des multiples réactions de solidification pendant l'atomisation. Un modèle de microségrégation pour la solidification d'alliages métalliques est alors développé. En considérant des flux de diffusion finis, des cinétiques de réactions dendritique, péritectique et eutectique et des surfusions de germination, une alternative plus évoluée est proposée aux modèles de Gulliver-Scheil ou de la loi des leviers. Le couplage avec des calculs d'équilibre thermodynamique est effectué pour évaluer les compositions des interfaces et les termes d'enthalpie dans le bilan d'énergie. Le modèle est appliqué à un alliage binaire, avec des densités de phases constantes, pour simuler le procédé d'atomisation de gouttes d'alliage Al-Ni. Un modèle dédié est choisi pour les conditions aux limites d'échange de chaleur. Les résultats sont comparés à des mesures expérimentales obtenues par diffraction de neutron. Des interprétations sont alors établies sur les comportements non triviaux des alliages Al-Ni solidifiés rapidement. Le modèle proposé permet ainsi d'appréhender les effets concurrents des différentes cinétiques (diffusion chimique, bilan d'énergie, vitesse croissance des microstructures, etc.) lors de la solidification hors équilibre. Les principaux développements envisageables autour de ce travail incluent : l'extension aux alliages multicomposés, l'inclusion de densités variables, le couplage avec des calculs macroscopiques.