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ÖgeDesign and evaluation of high-k dielectric materials for low-power 'green' OFET-based sensors(Graduate School, 2024-10-17)This thesis aims to design and focus on the exploration of OFET-based sensors using solution-processed polymeric dielectrics and organic semiconductors. It also investigates the potential of synthetic and natural polymeric dielectrics blended with nanoparticles on capacitors. The thesis is organised into five chapters: The first twochapters consist of the published review articles on OFET and OPT devices. They provide a comprehensive background on these devices, supported by examples from literature, along with explanations of the mechanisms of the devices. The third and fourth chapters present the experimental research findings related to capacitors and OFET devices, offering new insights and data. The last chapter summarises the results, evaluates the research, discusses the challenges encountered, and concludes the thesis with planned recommendations for future work
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ÖgeProduction and characterization of al-CoCrFeNi-M (M=Mo, Cu, Mn) high entropy alloys by combustion synthesis method(Graduate School, 2024-10-16)This thesis demonstrates the successful synthesis of high-entropy alloys (HEAs) such as AlxCoCrFeNi, AlxCoCrFeNiCuy, AlxCoCrFeNiMoy, and AlxCoCrFeNiMn using a metallothermic non-centrifugal Self-Propagating High-Temperature Synthesis (SHS) method. This process employed relatively low-cost oxide raw materials like Co3O4, Cr2O3, Fe2O3, NiO, MoO3, and MnO2, with metallic aluminum as a reductant, achieving synthesis within seconds with minimal energy input. The introduction of metallic copper was found effective in promoting exothermic reactions in Cu-containing alloys. Thermochemical simulations using FactSageTM's "Equilib" module were highly effective in predicting SHS outcomes, despite slight deviations due to reactor lid sealing issues and gas release. Experimental results closely matched theoretical predictions, with minor fluctuations attributed to experimental conditions and measurement errors. These simulations were particularly accurate in representing SHS under adiabatic conditions, even though real experiments exhibited some heat loss and scattering. The slag phase separation from alloys was relatively easy, though small amount of slag and inclusions were present within the alloys. The lack of a reliable correlation between adiabatic temperatures or charge mixture compositions and reaction yields was noted due to scattering and gasification. Larger scale experiments are recommended to better assess SHS scalability, as gaseous products and scattering effects may diminish with increased batch sizes. Mn loss in the AlxCoCrFeNiMn system could be mitigated by optimizing the use of Al2O3 as a heat suppressant, reducing MnO2 waste and increasing yield. However, excessive Al2O3 can form MnAl2O4 spinel, lowering manganese reduction efficiency. Optimizing the heat suppressant amount through thermochemical simulations is crucial, with 12 g of Al2O3 found to be optimal for a 150 g charge mixture. Al content influences adiabatic temperature and alloy phase composition. Excess Al absorbs heat without participating in reduction reactions, lowering adiabatic temperature. Reducing Al content below x=0.5 proved difficult, as Al tends to dissolve into the liquid to achieve the desired Cr content. Al's impact extends to altering the crystal structure from FCC to BCC in CoCrFeNi-based HEAs due to atomic radius differences and valence electron concentration. High Al content leads to the formation of BCC phases, including the ordered BCC-B2 phase rich in Al-Ni and the disordered BCC-A2 phase rich in Fe-Cr. This phase transformation, consistent with phase diagram calculations, results in increased alloy hardness, particularly with higher Al content. The addition of Cu to the AlxCoCrFeNi system introduces another FCC phase rich in Cu, with its fraction depending on the Cu content. Low Al and Cu content (e.g., Al0.5CoCrFeNiCu0.5) results in lower secondary FCC phase fractions, while higher Cu and Al content leads to complex duplex FCC+BCC microstructures. The hardness of these alloys varies, with Cu and Al content. Mo addition to AlxCoCrFeNi primarily results in the formation of a brittle sigma phase. As Al content increases, complex microstructures comprising A2, B2, and sigma phases emerge. The hardness of Mo-containing alloys increases with Al content, peaking for the Al1.0Mo1.0 alloy, then decreasing due to the reduced sigma phase fraction at higher Al levels. In the Mn system, SHS alloys typically consist of FCC (A1) and BCC (A2+B2) crystal structures. Increasing Al content leads to a transition from a dual-phase structure to a fully BCC structure, with corresponding increases in hardness. The addition of Mn and Cr enhances hardness in the FCC Al0.5CoCrFeNiMn alloy. Arc-remelted and suction-casted SHS alloys exhibit similar microstructures but are generally porosity-free and contain fewer inclusions. Suction casting results in finer microstructures due to higher cooling rates, with notable differences in dendritic arm spacing observed in Cu-containing alloys. The hardness of these alloys is influenced by the phase fractions present, with BCC phases contributing to higher hardness. FCC-based alloys showed higher cold deformability than BCC alloys, with the Al0.5CoCrFeNi alloy achieving a 131% reduction in area and a 109% increase in hardness after cold rolling. The addition of Cu further enhanced cold deformability in Al0.5CoCrFeNiCu0.5 and Al0.5CoCrFeNiCu alloys, reaching 145% and 170% true reduction in area, respectively, along with significant work hardening. Hot deformability was lower in FCC alloys due to the precipitation of B2 and sigma phases, which increased flow stress through precipitation hardening and dislocation pinning mechanisms. However, increasing the hot deformation temperature could improve hot formability by preventing B2 and sigma precipitation, though temperatures above 1000°C might cause issues like liquefaction of Cu-rich phases. BCC alloys exhibited poor hot deformability, likely due to equipment limitations and high hardness. Annealing the cold-rolled alloys reduced hardness through static recrystallization or recovery, but also resulted in improved hardness and substantial area reduction. Notably, cold rolling followed by annealing produced an equiaxed single-phase FCC structure in Al0.5CoCrFeNiCu0.5, which could be important for corrosion resistance, suggesting further investigation into the corrosion properties of this alloy is warranted. It was found out that introduction of Mo to the AlCoCrFeNi alloy system decreases the high-temperature oxidation resistance (at 800 ºC). Consistent with the CALPHAD simulations, SEM and Raman analyses, the reason for this that presence of low Al and high Mo in the Al1.0Mo01.0 alloy, leads to a thick intermixed oxide layer consisting of spinel and MoOx oxides, before the stabilizaiton of thick protective M2O3 layer (M=Cr, Al). Increasing the Al/Mo ratio, allows the formation of thick protective M2O3 layer and protects and/or slows from further oxidation. Adding Mn to the AlxCoCrFeNi alloy system boosts its saturation magnetization, achieving 83 emu/g (552.4 kA/m) at a density of 6.63 g/cm³. However, this magnetization level is highly influenced by the distribution and ordering of the A2/B2 phases. When the Al content is increased, as in the Al1.5Mn1.0 alloy, the saturation magnetization drops to 147.2 kA/m despite a lower density of 6.40 g/cm³ due to a higher proportion of the ordered B2 phase. The presence of Cr-rich regions near grain boundaries, which are likely paramagnetic due to Cr's antiferromagnetic properties, further diminishes magnetization. To enhance the alloy's soft-magnetic properties, removing Cr could be beneficial. Moreover, the coercivity, which is crucial for minimizing hysteresis loss, rises in alloys with Cr-rich phases and inclusions, with values of 43 Oe (3421 A/m) and 54 Oe (4297 A/m) observed in the Al1.0Mn1.0 and Al1.5Mn1.0 alloys, respectively.
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ÖgeInvestigation of the catalytic performance of tin nanowires produced by aluminum anodic oxide template method for electrochemical CO2 reduction(Graduate School, 2023-10-17)Climate change causes various dramatic situations, including the melting of the ice mass, flooding, and drought, and it affects even the daily life of human beings. The increased amount of anthropogenic CO2 gas in the atmosphere is one of the driving forces for global warming and climate change. Therefore, mitigation of CO2 gas has become mandatory to eliminate the harmful effects of global warming. There are mainly two mitigation methods: carbon capture-storage and carbon capture-utilization. By the utilization of carbon dioxide, not only the amount of CO2 is reduced, but also it is used as an input for value-added chemical production. Among the utilization methods, electrochemical CO2 reduction over heterogeneous metallic electrocatalyst steps forward thanks to its several advantages, such as high number of available catalysts, its ability to work at ambient conditions, scalability, and the utilization of renewable energy sources. Several products, including organic acids, hydrocarbons, and fuels, can be obtained via electrochemical CO2 reduction reactions. The techno-economic analysis performed for the feasible CO2 reduction systems have shown that formic acid is the most practical chemical to be produced via electrochemical CO2 reduction. Formic acid is used as input in various industrial areas such as agriculture, food, textile, and pharmaceutical. However, recent studies have indicated that formic acid is also a strong candidate for modern engineering applications. For instance, formic acid has an extraordinary capacity to carry H2 gas (590 l per l). This storage performance of formic acid enables the advance in the H2 driven cars. Moreover, formic acid can be used as feed for formic acid fuel cells to generate electricity. The conventional production methods of formic acid require high energy consumption and include highly complex process steps. Hence, the production of formic acid via electrochemical CO2 reduction utilizing renewable energy sources such as wind, solar, etc., is in high demand. The metallic electrocatalysts that produce formic acid or formate (depending on the pH) are Sn, Cd, Tl, In, Pb, Bi, and Hg. Among these metals, tin is one of the most studied electrocatalysts since it has low toxicity, is abundant in nature, and is cost-friendly. Tin is known to produce only formic acid as liquid product under the electrochemical CO2 reduction in liquid environment at ambient conditions. Although high Faradaic efficiency has been achieved for formic acid, there are challenging problems in scaling up the CO2 reduction system. These problems can be listed as low current density, low stability, high overpotentials, and by-product formation. Specifically, low current density due to the low solubility of CO2 in the aqueous solutions and low catalytic activity is a crucial disadvantage. To overcome the low current density, flow-cell systems, gas diffusion electrodes, and gas-phase reduction structures have been proposed since the low solubility problem of CO2 can be outframed. To increase the catalytic activity of the catalysts, meso- and nano-structured electrodes have been proposed rather than using bulk electrodes. Especially nanostructured electrodes, such as nano-rods, wires, tubes, sheets, etc., have shown promising results in terms of efficiency and activity thanks to their unique structure. In the literature, there are several studies on the production of tin-based nanostructured electrodes, tin nanowires have yet to be investigated extensively compared to the other structures. Nanowires can be a great candidate for electrocatalytic CO2 reduction since they offer high surface to volume ratio and enhanced charge and mass transfer. In recent years, a few studies on tin nanowire electrocatalysts have been published, yet the suggested production methods in these works are highly complex. To commercialize the electrochemical CO2 reduction system, the production technique is also crucial, besides the performance of the electrocatalyst. The ideal production method should be simple, low-cost, and scalable. Also, significant structural changes should be obtained by easily altering the working parameters such as potential and duration. In this study, the catalytic performance of tin nanowire electrodes produced via the AAO template method toward formate production under electrochemical CO2 reduction is investigated. By choosing AAO template method, most of the desired properties of the catalyst production technique are provided. A self-standing, interconnected, and branched-like 3D nanowire network was achieved via simple AAO template technique. Moreover, anodic oxidation in alkaline solution was applied to the as-produced tin nanowires to increase the active surface area and improve catalytic performance by increasing the oxide-related content on the electrode surface. The first of the tin nanowire production was the formation of AAO template. To obtain AAO pattern, the aluminum substrate was anodically oxidized in 0.3 M oxalic acid solution at 70 V for 30 min. Then, the zincating process was applied to make the AAO template electrodepositable. The main drawback of the AAO template method is the formation of a non-conductive barrier layer at the bottom of the pores, which prevents the direct usage of the template for electrodeposition. By fast and easy zincating step, AAO templates can be prepared for the electrolytic solutions without any significant change and/or loss of structure. Tin was electrodeposited into the AAO template in tin sulphate-containing bath under constant potential. Then, AAO template and the remnant aluminum were dissolved in 3 M NaOH solution at 60°C until the vigorous H2 gas evolution stops. The obtained tin nanowire electrodes were characterized by SEM and Raman analysis. The catalytic performance tests were conducted in a custom-made H-cell filled with 0.1 M KHCO3 at potentiostatic mode for 1 h. The catalytic behavior was expressed as Faradaic efficiency toward formate. To compare the performance, high purity tin foil was subjected to similar reduction experiments. The SEM analysis showed that tin nanowire electrodes possessed highly ordered and interconnected branched-like structure, including nanowires having 7 µm length and 150 nm diameter. Moreover, it was found via Raman analysis that the surface contained poor crystalline and non-stoichiometric oxide structures. The reduction experiments indicated that tin nanowire electrodes achieved 10 times higher current density values than tin foil at every reduction potential. However, the increase in formate production was not as high as current density values, and only 6-fold higher production amount was observed. Moreover, Faradaic efficiency values reached only 30% on the tin nanowire electrodes, while 60% efficiency was obtained over tin foil. This result indicated that a significant portion of the total charge is consumed by side reactions, i.e., CO and H2 formation rather than formate. The low efficiency values obtained over tin nanowire electrodes were attributed to the destruction of the oxide content on the nanowires during the AAO removal in the concentrated NaOH solution. Since the oxide layer has been proved as the key catalytic part for the formate production over tin-based catalysts by in-situ and in-operando studies, the removal of the oxide content results in the decay of the catalytic performance toward formate. In concentrated alkaline solutions, tin oxides can dissolve, and the electrode ends up containing mostly metallic tin. To further prove this phenomenon, tin foil was immersed in 3 M NaOH solution at 60°C for 2 hours, and then CO2 reduction experiment was run over this electrode. The result showed that the efficiency reduced from 60 to 15% after etching in alkaline solution. To reform the destructed oxide layer, anodic oxidation in 1 M NaOH at room temperature was performed. The applied potential was set to 4 V to obtain a crack-free porous oxide structure over tin nanowires. For comparison, tin foil was also anodically oxidized. The SEM analysis showed that anodically oxidized tin nanowires enlarged approximately 50 nm, and pores formation on the wires with 30-40 nm diameter was observed. Raman analysis gave peaks of the crystalline SnO2 structure along with the SnO and Sn3O4. The catalytic performance was enhanced significantly, and 87% Faradaic efficiency with ca. 15 mA.cm-2 current density at -1.6 V vs. Ag/AgCl was achieved over anodically oxidized tin nanowire electrodes. Moreover, 9- and 12-times higher formate production was achieved over anodically oxidized tin nanowire electrode compared to anodically oxidized tin foil and untreated tin foil, respectively. However, current density values for both tin nanowire and tin foil decreased after anodic oxidation due to the semi-conductive character of the tin oxide structures. The improvement in the catalytic behavior after anodic oxidation was attributed to the increased surface area and oxide layer formation on the electrode surface; the latter was more dominant. The ECSA calculations showed that anodically oxidized tin nanowire electrode possessed only 4-fold higher active area than anodically oxidized tin foil. The formate production amount was much higher than the surface area increase, therefore the improved catalytic activity was not only related to the active surface area. Furthermore, the kinetics of the electrochemical CO2 reduction reactions was faster over anodically oxidized tin nanowire electrodes since lower polarization resistance value was obtained via EIS analysis. As an important indicator for the catalytic performance, stability was tested over both anodically oxidized tin nanowire and tin foil electrodes for 12 h at -1.5 V vs. Ag/AgCl. Within the first 30 min, the oxide layer over the tin foil flaked off from the surface; therefore, the experiment was not continued. The anodically oxidized tin nanowire electrode preserved its structural integrity throughout the experiment and gave ca. 64% Faradaic efficiency. However, after 5 hours, a slight decline was observed in the current density values. The SEM images revealed the enlargement of the nanowires and fillings between the nanowires. The current density loss was related to the decline in the surface area. The Raman analysis indicated the absence of the crystalline SnO2 related peaks but the intensified of the already existing peaks for SnOx structures and new peak formation for SnO structure. These results concluded that the survival of the metastable oxide structures over tin nanowires is crucial for preserving the efficiency value toward formate even if the current density is lost.
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ÖgeTiB2 coating on different substrates via dual process:CA-PDV and CRTD-Bor(Graduate School, 2024-01-22)Boriding process is a surface modification technique that enhances the mechanical properties of industrial components including stiffness, hardness, strength, and wear/corrosion resistance, resulting in enhancements in their lifetime and efficiency. Among the transitional metal borides, titanium diboride (TiB2) is one of the hardest metallic-ceramic phases with its excellent electrical and thermal conductivities, good thermal oxidation resistance, high melting point, and good chemical stability. In bulk form, titanium diborides are used as thermal evaporation crucibles, armors, and as a cathode in electrochemically reducing alumina to aluminum metal. TiB2 is also applied as a coating for cutting and forming aluminum alloys and improving titanium alloys' oxidation and wear resistance. Various boriding methods such as pack/paste boriding, salt-bath boriding, fluidized bed boriding, plasma boriding, and gas phase are used to form TiB2 layers on titanium-based substrates. In addition, the TiB2 layer can be grown as a coating on metallic substrates using vacuum-based techniques (CVD and PVD). However, all these procedures have at least one of these drawbacks: the high cost of chemicals and materials, the requirement of expensive equipment, long processing time, toxic emissions and by-products, and the consumption of a large amount of energy. In the current study, to overcome the above-mentioned problems, a dual process consisting of a very common and undemanding PVD coating technique, cathodic arc-physical vapor deposition (CA-PVD), and rapid, environmentally friendly, and cost-effective cathodic reduction and thermal diffusion-based boriding (CRTD-Bor) is used. Ti layers on different substrates are produced with CA-PVD that are then converted into titanium borides with CRTD -Bor process. The advantages of the preferred route to form TiB2 on different substrates are as follows: Eliminate the use of expensive TiB2 cathodes Stoichiometric TiB2 coatings growth Overcome the adhesion problems of TiB2 coatings on substrate materials Eliminate the need for expensive equipment and starting materials Use of stabile oxide-based chemicals No toxic raw materials Eliminate greenhouse gas emissions Multiple useability of stable electrolytes with periodic chemical additions Shortening the boriding process time resulting in an increased TiB2 formation rate In the first part of the study, the growth of the TiB2 layer on the Cu substrate, which is used as spot welding electrode material, was targeted. Naked copper electrodes do not function properly and create serious problems such as welded material and electrode tip adhesion and electrode deterioration, resulting in reduced electrode life and weld quality during spot welding of galvanized steel and aluminum because of the high chemical reactivity of zinc and aluminum with copper. Relying on the limited reactivity of TiB2 with Zn and Al, copper electrode surfaces were initially Ti coated using CA-PVD and then borided via CRTD-Bor to convert the Ti layer into a TiB2 structure. Because the boriding temperature is above the eutectic reaction temperature between Ti and Cu (at 875 °C), an Nb interlayer was applied between Ti coating and Cu substrate to prevent local melting and disbonding problems that may occur at the Cu-Ti interface. The coating architecture consisted of 2.6 - 3.2 micron thick Nb and 4 - 5 micron Ti. Boriding experiments were carried out at different temperatures (950 and 900 °C) for various durations (10-90 min.) at a consistent current density (200 mA/cm2) in the molten salt containing 90% sodium tetraborate and 10% sodium carbonate. As a result, the proposed ~1.3 m Ti-boride layers were produced at idealized conditions (i.e., 900 °C and 30 minutes) with high adhesion strength to the substrate (HF1). Lab scale spot welding tests showed the positive role of the boride layer and spot welding performance of copper electrodes. In the second part of the study, improving the wear resistance issues associated with M2 high-speed steel (HSS) was aimed. This was achieved by surface modification through the formation of a TiB2/TiC multilayer via the combined process. CRTD-Bor was applied to the CA-PVD Ti-deposited HSS substrate. During the boriding process, TiB2 growth occurred at the top layer due to boron diffusion at the interface of the substrate (cathode) and the electrolyte. Simultaneously, the TiC layer formation took place as carbon in the steel diffused from the substrate to the Ti layer, ultimately resulting in the production of a TiB2/TiC multilayer. To determine the effects of boron and carbon, diffusion on the nature of grown multilayer, boriding experiments were conducted at various temperatures (from 900 to 1000°C) for 15-60 minutes with a constant current density (200 mA/cm2). According to the characterization results, both the boride and carbide layers' thickness increased as the boriding times and temperatures increased and it obeyed the Parabolic Law. Empirical equations are derived for estimating the thickness of layers at different times and temperatures. These equations could be used in the temperature range of 1173 to 1273 K at the current density of 200 mA/cm2 with the Ti layer having a thickness of 8.5 µm. d_(TiB2 )=86.60√(exp(-17573/T).t) d_TiC=425.44√(exp(-22529/T).t) Where d is the thickness of the modified layer's thickness (µm), T is the boriding temperature (K), and t is the boriding time (sec.). Moreover, based on the kinetic investigations, the activation energies (Q) and pre-exponential factors (K0) were calculated as 146.10 kJ/mol and 7.50 × 10−9 m2/s for the formation of TiB2 as well as 187.31 kJ/mol and 1.81 × 10−7 m2/s for TiC layers respectively. Furthermore, according to the micro-indentation investigations as a function of the penetration depth, the surface hardness value was measured as 41 ± 5 GPa which is consistent with the reported value for the TiB2 hardness. However, in the mixed TiB and Ti regions (at deeper penetration depth), the hardness values declined to 24 ± 2 GPa and 13 ± 1 GPa and then raised to 20 ± 1 GPa because of the TiC contribution to the total hardness. Also, all treated samples exhibited excellent adhesion properties (HF1) as determined by the Daimler-Benz Rockwell C test. In the final stage, ball-on-disk sliding wear tests were conducted for the samples against an alumina ball to assess and compare the tribological performance of the borided sample and M2 HSS. The outcomes of the tribological investigation demonstrated an eightfold enhancement in the wear resistance of the boride sample compared to the untreated sample.
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ÖgeEffect of electrolyte and electrical parameters on the anodic oxidation of ti to improve photocatalytic performance of TiO2 nanotube structures(Graduate School, 2023-11-02)TiO2 is a semiconductor material that, when stimulated by photons with energy sufficient to overcome its band gap (3.0-3.2 eV), generates electron-hole pairs. By interacting with one another or through a succession of redox reactions, these charge carriers eventually have the capacity to mineralize a wide range of organic compounds, including dyes, surfactants, aromatics, and alkanes. This property makes various TiO2 forms (powder, nanotube, nanorod, etc.) appropriate for a variety of applications in the energy and environmental domains, such as solar cells, hydrogen production, water purification, air purification, and others. This thesis study was undertaken to investigate production, characterization and photocatalytic performance of TiO2 nanostructures as a very promising semiconducter photocatalyst. Anodic oxidation process utilized for production of TiO2 nanostructures from comercially pure titanium foils. Various electrolytes and elecrtrical parameretes explored to investigate their effect on the surface preperad. Produced nanostructures characterized by surface morphology analyses with optical and electron microscopy, surface phase and structure analyses with XRD, XRF and Raman, optical properties analyses with photoluminescence and UV-DRS, and with organic contaminant degradation tests. One of the anodic oxidation parameters studied in the scope the thesis was cyclic bipolar voltage. In this work group different duty cycle and frequency values was experimented and nano structures succesfully produced on titanium foils. Results showed that the increasing positive pulse duration, number of successive positive pulses and neutral period of the cycle could increase nanotube diameter. Also, application of negative voltage clearly deterioriated the nanotube morphology and produced a sponge like structure at the surface. Effect of pre-deformation mode and strain level on the photocatalytic performance of TiO2 nanotubes produced by anodic oxidation on titanium foils were also investigated. In this study set, three different amounts of tensile and compression strains applied to titanium foil prior to anodic oxidation. Results showed that pre-deformation on titanium foils could have a strong effect on photacatalytic performance of TiO2 nanotubes produced from these foils. Especially cold rolling deformation was quite successful in improving photacatalytic performance. On the other hand, critical amount of tensile deformation did improve photocatalytic performance, where further deformation amount detoriated it. One other anodic oxidation parameter studied in the thesis was effect of carbon structure, namely carbon nanotubes, addition to electrolyte. Different amounts of carbon nanotubes was added to anodic oxidation electrolyte since, in term of impoving xviii photocatalytic performance, carbon is a very effective dopant for TiO2 structutres. Results showed that deposition of carbon structures on TiO2 nanotubes was successful and photocatalytic performance of these doped samples were better than un-doped ones. However due to clustering and covering up effect of carbon structures, with the increase at the carbon concentration in electrolyte, photocatalytic performance decreased. Prior to anodic oxidation experiments, a surface preparation method named electropolsihing and a surface coating method named hot-dip aluminizing also studied. Electropolishing of titanium foils was experimented to produce smooth surfaces for further proceses. Succesfuly electropolished titanium surfaces were preperad after trials with various process parameters and these surfaces used in anodic oxidation trials. Alumizing of titanium foils were investigated to produce intermetalic surfaces for further procesess/applications. Intermetallics of aluminum and titanium succesfully produced with this method and these structures greatly improved high temperature oxidation resistance of titanium foils. Anodic oxidation of these surfaces was not undertaken in the scope of this thesis, however formation of nanostructures on intermetallics could be a very interesting further study. As a whole, thesis study investigated electropolishing, aluminizing and anodic oxidation of titanium foils. Succesfull parameters for electropolishing of commercially pure titanium was established. Additionally, various ways to improve photocatalytic performance of a TiO2 nanostructures demonstrated. In this context, outputs of the thesis study could be useful in two very strategically important and urgent fields namely, energy and envioroment.