Copper losses to slag are generally between 0.7-2.3% during the copper matte smelting stage. In this study, the aim was to reduce these losses in the slag phase. For this purpose, usage of some additives (especially calcined colemanite labeled as CC, boric oxide-B2O3 and calcium oxide-CaO as well) as flux material was investigated. The flash furnace matte-slag (FFM-FFS) obtained from Eti Copper Inc. and a master matte-slag (MM-MS) produced synthetically were used as starting materials. Additives were tested in various amounts under two different atmospheres (N2 and low Po2 obtained by mixture of CO2/CO gases). Temperature and duration were also used as experimental variables. Experimental results have indicated that 2 hours was sufficient to obtain a low copper content in slag about 0.3% and 0.4% for FFS and MS, respectively. It was also seen that the copper content in slag decreased with increasing CC addition at all oxygen partial pressures and at all temperatures. Furthermore, the addition of all additives up to 4% had great influence in lowering the copper content in the final slags (~0.3%Cu). From FactSage calculations, it could be concluded that the colemanite addition decreased the liquidus temperature which led to early melting of slag and allowed enough duration for settling of matte particles within the slag without substantial changing its viscosity, which resulted in less mechanical copper losses to the slag. By using colemanite in copper production, it was possible that a new application area for boron compounds which are produced in Turkey could be created.

In this thesis work, a high grade chromite concentrate obtained from PinarbaSi, Kayseri region of Turkey was reacted with sulfuric acid solution to determine the optimum conditions of leaching of chromite ores. Conventional methods for producing chromium are still valid in industry. The main process in production includes soda melting and taking it into solution in the form of chemical compounds such as sodium dichromate. Three and six valence states of chromium have importance in production. Trivalent chromium, chrome ore or chromite have no harmful effects. However, compounds of hexavalent chromium show toxic, irritating and corrosive action to people and environment. In the mentioned conventional method, main products consist of hexavalent chromium compounds. In this study, only trivalent chromium remained in the leach solution and did not change to hexavalent state. Obtained product after leaching was chromium(III) sulfate. The maximum extraction of chromium in the absence of perchloric acid was 94.1 % under the conditions of 175 &deg / C, 6 hours and 84.6 wt % sulfuric acid. The maximum extraction of chromium in the presence of perchloric acid was 98.7 % under the conditions of 175 &deg / C, 2 hours, 84.6 wt % sulfuric acid and &frac12 / perchloric acid / chromite ratio. The latter one was also the highest recovery value obtained during the experiments. Moreover, in none of the analyzed samples, appreciable amounts of hexavalent chromium was found during analyses.

Main reason for the current losses in electrolytic magnesium production is the reaction between electrode products. Present study was devoted to effective separation of chlorine gas from the electrolysis environment by a new cell design and thus reducing the extent of back reaction between magnesium and chlorine to decrease energy consumption values. The new cell design was tested by changing temperature, cathode surface, current density, anode cathode distance and electrolyte composition. Both the voltages and the current efficiencies were considered to be influenced by the amount and hydrodynamics of chlorine bubbles in inter-electrode region. Cell voltages were also found to be affected from the nucleation of magnesium droplets and changes in electrolyte composition that took place during the electrolysis. A hydrodynamic model was used to calculate net cell voltage by including the resistance of chlorine bubbles on anode surface to theoretical decomposition voltage during electrolysis. Good correlations were obtained between experimental and calculated voltages. The same model was used to calculate current efficiencies by considering chlorine diffusion from bubble surfaces. A general agreement was obtained between calculated and experimental current efficiencies. Desired magnesium deposition morphology and detachment characteristics from cathode were obtained when MgCl2-NaCl-KCl-CaCl2 electrolytes were employed. Current efficiencies higher than 90% could be achieved using the above electrolyte. The cell consumes around 8 kWh&amp / #903 / kg-1 Mg at 0.43 A&amp / #903 / cm-2 as a result of high chlorine removal efficiency and capability of working at low inter-electrode distances. Furthermore, the cell was capable of producing magnesium with less than the lowest energy consumption industrially obtained, at about double the commonly practiced industrial current density levels.

In the present study / the effects of the powder metallurgical parameters such as the mixing method, compaction pressure, initial tungsten (W) particle size, composition, sintering temperature and sintering time on the sintering behavior of selected high density W-Ni-Cu alloys were investigated. The alloys were produced through conventional powder metallurgy route of mixing, cold compaction and sintering. The total solute (Ni-Cu) content in the produced alloys was kept constant at 10 wt%, while the copper concentration of the solutes was varied from 2.5 wt% to 10 wt%. Mainly liquid phase sintering method was applied in the production of the alloys. The results of the study were based on the density measurements, microstructural characterizations including optical and scanning electron microscopy and mechanical characterizations including hardness measurements. The results showed that the nature of the mixing method applied in the preparation of the powder mixtures has a considerable effect on the final sintered state of W-Ni-Cu alloys. Within the experimental limits of the study, the compaction v pressure and initial W particle size did not seem to affect the densification behavior. It was found that the sintering behavior of W-Ni-Cu alloys investigated in this study was essentially dominated by the Ni content in the alloy and the sintering temperature. A high degree of densification was observed in these alloys with an increase in the Ni content and sintering temperature which was suggested to be due to an increase in the solubility and diffusivity of W in the binder matrix phase with an increase in these parameters, leading to an increase in the overall sintering kinetics. Based on the results obtained in the present study, a model explaining the kinetics of the diffusional processes governing the densification and coarsening behavior of W-Ni-Cu alloys was proposed.

The aim of this work is to nondestructively characterize the industrial dual phase (ferritic-martensitic) steels (DPS) by the Magnetic Barkhausen Noise (MBN) method. By quenching of AISI 8620 steel specimens having two different starting microstructures, from various intercritical annealing temperatures (ICAT) in the ferrite-austenite region, the microstructures consisting of different volume fractions of martensite and morphology have been obtained. The microstructures, strength properties and hardness values were determined by conventional metallographic and mechanical tests. The measurements of the Magnetic Barkhausen Noise (MBN) were performed by using both Rollscan and &amp / #956 / SCAN sensor connectors. A good correlation between the martensite volume fraction, hardness and MBN signal amplitude has been obtained. MBN emission decreased as the ICAT, therefore the volume fraction of martensite increased. Moreover, MBN emission decreased as the martensite morphology become thinner. It has been concluded that MBN method can be used for nondestructive characterization of industrial dual phase steels.

With constant miniaturization of integrated circuits, the current densities experienced in interconnects in electronic circuits has been multiplied. Aluminum, which is widely used as an interconnect material, has fast diffusion kinetics under low temperatures. Unfortunately, the combination of high current density and fast diffusion at low temperatures causes the circuit to fail by electromigration (EM), which is the mass transport of atoms due to the momentum transfer between conducting electrons and diffusing atoms. In the present study, the effect of alloying elements in aluminum on the diffusion behavior is investigated using a non equilibrium molecular dynamics method (NEMD) under the effect of electromigration wind force. The electromigration force was computed by the use of a pseudopotential method in which the force depends on the imperfections on the lattice. 1.125 at% of various elements, namely Cu, Mg, Mn, Sn and Ti were added into aluminum. The electromigration force was then calculated on the alloying elements and the surrounding aluminum atoms and these forces incorporated into molecular dynamics using the non-equilibrium formalism. The jump frequencies of aluminum in these systems were then computed. Cu, Mn and Sn impurities were found to be very effective in lowering the kinetics of the diffusion under electromigration conditions. Cu was known experimentally to have such an effect on aluminum for several years, but the Mn and Sn elements are shown here for the first time that they can have a similar effect.

ABSTRACT DISCUSSION AND EVALUATION OF MINING AND ENVIRONMENT LAWS OF TURKEY WITH REGARD TO EU LEGISLATION Turkey is trying to become a member of the European Union. Within this frame, studies are proceeding for harmonization of the Turkish legislation with the EU legislation. European legislation might have positive or negative impact on the mineral extraction industry and national mining law. Since there is no title directly related to mining policy in the EU legislation the mining policy of EU was evaluated especially under the titles&ldquo / energy&rdquo / and &ldquo / environment&rdquo / . In this thesis, the Turkish mining regulations and the environmental aspects of the mining activities have been investigated and discussed in comparison with those of EU. The latest developments about mining sectors of Turkey and EU have been evaluated and the comparison between EU directives and Turkish laws and regulations about mining have been made. In this study, modifications that should be realized in laws and regulations and measures that should be taken by Turkey as a candidate country for EU discussed and some proposals have been made.

In this study, maghemite (&amp / #947 / -Fe2O3) thin films were prepared by chemical solution deposition on glass and quartz substrates. The solution was prepared by using 0.3 M iron (III) nitrate [Fe(NO3)3 - 9H2O] as precursor and dissolved in a mixture of 2-methoxyethanol and acetylacetone in a molar ratio of 20:2, by stirring the solution at RT for 2 hours. Substrates were prepared by either piranha etching method or ultrasonic cleaning method. The solution was spin coated on glass and quartz substrates at 1400 and 4000 rpm for 1 minute. The resultant film thickness was found as 65 and 80 nm by SEM. Viscosity of the main solution was found to be approximately as 0.0035 Pa.s by viscosity measurement. TGA/DTA analyses showed that, to produce maghemite thin film, heat treatment should be done between 330 &deg / C and 440 &deg / C. Homogeneous and crack free maghemite thin films were observed by Energy Dispersive Spectrometry (EDS) and Scanning Electron Microscope (SEM) methods. TEM studies verified maghemite thin film formation by using electron diffraction and SAED (selected area electron diffraction) method. Thin film characteristics were evaluated by changing the experimental parameters which are annealing temperature, annealing time and thickness of the films using XRD (x-ray diffraction) method. Optical band gap of maghemite thin films were found as approximately 2.64 eV by UV-VIS Spectrophotometer. Magnetic properties of maghemite thin films were also examined by VSM (vibrating sample magnetometer).

In this study, an attempt has been made to hydrometallurgical extraction of cobalt and nickel by atmospheric pressure sulphuric acid leaching and a pug-roast-leach process using two stage roasting for lateritic ore. The ore used in the study was obtained from &Ccedil / aldag Lateritic Ore, Manisa, Turkey. The metal contents of the ore are 2.1 % Ni, 0.12 % Co, 32.45 % Fe, 1.01 % Mn, 2.58 % Cr, 0.78 % Mg and 1.01 % Al. The reserve of lateritic ore deposit is approximately 40 million tonnes. In the study, first sulphuric acid leaching was applied at atmospheric pressure for leaching the &Ccedil / aldag lateritic ore. The effect of various parameters, such as leaching time, leaching temperature, particle size, pulp density and acid strength on Ni and Co extractions were determined. By leaching at 80oC for 40 wt % H2SO4 addition of ore, 1/3 pulp density, Ni and Co extractions were found 44.49 % and 53.03 % respectively, yielded a pregnant solution containing 3.11 g/L Ni and 0.12 g/L Co. But the result of atmospheric pressure sulphuric acid leaching was considered insufficient from the recovery point of view. In the pug-roast-leach process, which is consisted of a two stage roasting followed by water leaching, decomposition temperature differences of sulphates of cobalt, nickel and iron are exploited. In this process, amount of acid, sulphatization and decomposition temperature, sulphatization and decomposition time, leaching temperature and time, solid/liquid ratio, and the effect of water addition during pugging were optimized. Under the optimized conditions (sulphuric acid: 25 wt % of ore / moisture: 20 wt % of ore / sulphatization temperature: 450oC / sulphatization time: 30 minutes / decomposition temperature: 700oC / decomposition time: 60 minutes / leaching temperature: 70oC / leaching time: 30 minutes and solid-liquid ratio: 1/4 by weight), Co and Ni extractions were found 91.4 and 84.4 percent, respectively. A pregnant solution containing 3.084 g/L Ni and 0.185 g/L Co was obtained. These results were considered sufficient for the leaching of lateritic nickel ores.

Titanium-nickel is a unique class of material known as Shape Memory Alloy (SMA). A thermoelastic martensitic phase transformation is responsible for its extraordinary properties such as shape memory effect and superelasticity. The near equiatomic Ti-Ni alloys are the commercially most exploited SMAs because of the unique combination of these properties and superior ductility, strength, fatigue resistance and corrosion resistance. The properties of Ti-Ni SMAs are very sensitive to composition and the processing parameters. The properties of Ti-Ni SMAs can be modified to a great extent by choice of composition, mechanical working and heat treatment. Thermo-mechanical treatments are required to strengthen the matrix and improve the shape memory characteristics. Plastic deformation and subsequent annealing is the common way to improve shape memory properties. In the present study, Ti- 50 at% Ni wire specimens are produced and used for the investigation of the effect of different heat treatment and cold working processes on shape memory characteristics. To investigate the thermomechanical behavior of differently processed wire specimens, a fully computerized servo hydraulic thermomechanical testing machine was designed and constructed. Testing machine was capable to perform different types of tests that are selected by the user. It can both heat and cool the specimen automatically according to the testing sequence by applying DC current directly through the SMA wire or by sending liquid nitrogen into the cooling chamber. Temperature is measured by a K-type thermocouple directly mounted on the wire specimen with a glass tape. Force that is applied to the specimen is produced by hydraulic power unit with a double action cyclinder and it is controlled by a controller which takes the feedback from the loadcell and LVDT (Linear Variable Distance Transducer). During performig thermomechanical-tests all the data of loadcell, LVDT and thermocouple are collected by a data acqusition system integrated with a host computer that operates the program XPC Target. Ti-Ni alloy with equiatomic composition is prepared in vacum induction furnace. Specimen cast in the form of rod was then hot swaged. Subsequent to swaging, cold wire drawing, intermediate annealing at 500 &amp / #61616 / C and water quenching was applied to obtain SMA wire with a diameter of 1.52 mm. Ti-Ni wires produced were subjected to four different processes. All the samples were initially solution heat treated at 925 &amp / #61616 / C for 30 minutes prior to water quenching. Some of the samples were further treated by an intermediate anneal at 500 &amp / #61616 / C. To see the effect of cold working / prior to intermediate annealing, 20 % or 40 % cold work was applied to another group of specimens. To study the shape memory characteristics of specimens subjected to the above mentioned processes, four types of test, namely constant stress free recovery test, constant strain free recovery test, constant stress constrained recovery test and constant strain constrained recovery test, were designed and applied cyclically. The tests have shown that the stress plateau observed in the first cycle of the tests disappear upon cycling and the shape memory characteristics improve and stabilize with cycling. Once trained by cycling, fractional free recovery was observed to reach to 100 % and recovery stress to reach 120% of the applied stress if shape recovery is prevented.