The thesis aims to develop an ISFET chip compatible miniaturized planar reference. Such planar reference electrode will be constructed by: silica / silica oxide / titanium / palladium / silver / silver chloride / saturated KCl agar / silica nitride / silica. For the size of the reference electrode is only 10mm (length), 5mm (width) and 1mm (height), which is diminished of hundred-fold to the traditional reference electrode. In addition to develop the fabrication techniques of the electrodes, this thesis will be devoted to systematic measuring and analyzing their stability, AC impedence, cyclic voltammery and electrochemical noise characteristics. The results show that the stability is inside 1mV, offset voltage is about -9 mV and the resistance of AC impedence is 400

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.

This study aimed synthesizing hydroxylapatite (HA) and Zn2+, F- and Cl- doped HA by solution precipitation method. The synthesized compounds were sintered at 1100&deg / C for 1h. For structural characterization, density of the samples were measured by Archimedes&rsquo / method. It was observed that Zn2+ addition increased the density significantly whereas F- caused a decrease and Cl- increased the density with a little amount. XRD was applied to the samples and it was found that co-doping of Zn2+ and F- ions decreased the unit cell volume of HA with F- addition. Other compositions gave fluctuated results in terms of unit cell volumes. HA phase and a little amount of CaO phase were detected in some samples. FTIR spectroscopy was used to detect whether Zn2+, F- and Cl- ions were incorporated to the HA structure or not by observing the bands corresponding to the bonds in the molecules. The amount of addition was also detected by FTIR. Results showed that ion incorporation to the HA structure was done successfully. SEM images were v analyzed and grain sizes of samples were calculated by Rietvelt analysis. Grain sizes of the samples increased by Cl- addition and decreased by Zn2+ and/or F- addition. For mechanical characterization, Vickers microhardness test was applied. Fracture toughness was calculated from Vickers microhardness results. According to the results, the highest microhardness values were found for F- and Zn2+ co-doped samples. It was also shown that fracture toughness decreased by Zn2+ addition. However, Zn2+ and F- co-doped samples gave higher fracture toughness results when compared with pure HA. Cl- addition also decreased the fracture toughness. The best compositions in terms of structural and mechanical properties was chosen as Zn2+ and F- co-doped samples and biological characterization was applied to these samples. Saos-2 cell line was used in biological examinations. For biological characterizations, Alamar Blue&trade / assay to detect viability and alkaline phosphatase activity (ALP) assay to detect differentiation were done. It was observed that 2 mol.% Zn2+ addition increased the cell viability and alkaline phosphatase activity. 1 mol.% F- addition also improved cell viability and alkaline phosphatase activiy. SEM images were analyzed to observe the morphology of the cells on HA and selected doped HA discs. In accordance with Alamar Blue&trade / assay and alkaline phosphatase activity assay, cells showed dendritic shapes on 2 Zn and 2 Zn 1 F sample which was the indicator of good material-cell interaction. Dissolution test was also applied by immersing the samples in simulated body fluid (SBF). pH change and SEM images for Ca2+ deposition were investigated. Increase in pH change with time was observed. F- included samples gave the lowest pH change results, especially 2 Zn 1 F. Dissolution pits and some apatitic formations were observed in SEM images.

In this study, the synthesis of 5-ferrocenyl/aryl-4-(phenylselenyl)-1H-pyrazole derivatives was investigated since the integration of ferrocenyl and selenium moieties into pyrazole derivatives may increase their current biological activities. Initially, the starting propargyl aldehydes were synthesized from corresponding acetylenes. Subsequently, propargyl aldehydes were reacted with hydrazines to yield corresponding hydrazones. Then the in situ synthesized hydrazones were subjected to electrophilic cyclization with phenylselenyl chloride, which afforded 5-ferrocenyl/aryl-4-(phenylselenyl)-1H-pyrazoles in one-pot manner. Subsequently, reaction conditions were optimized in terms of electrophile, base, temperature and solvent. Best results were obtained with phenylselenyl chloride and NaHCO3 at room temperature in DCM for ferrocenyl substituted pyrazoles and DCE for aryl substituted pyrazoles. In summary, by employing the electrophilic cyclizations of in situ synthesized acetylenic hydrazones, a variety of 5-ferrocenyl/aryl-4-(phenylselenyl)-1H-pyrazole derivatives were synthesized in one-pot way in moderate to good yields.

High strength wastewater (HSWW) generated in food processing industries is characterized by high organic carbon and nitrogen content, and thus high oxygen demand. Biological nitrogen removal (BNR) is a technology widely used for the treatment of HSWW. Food processing facilities practice sanitation to keep food contact surfaces clean and pathogen-free. Benzalkonium chlorides (BACs) are cationic quaternary ammonium antimicrobial compounds (QACs) common in industrial antimicrobial formulations. BAC-bearing wastewater generated during sanitation applications in food processing facilities is combined with other wastewater streams and typically treated in BNR systems. The poor selectivity and target specificity of the antimicrobial BACs negatively impact the performance of BNR systems due to the susceptibility of BNR microbial populations to BAC. Objectives of the research were: a) assessment and quantification of the inhibitory effect of QACs on the microbial groups, which mediate BNR in HSWW treatment systems while treating QAC-bearing HSWW; b) evaluation of the degree and extent of the contribution of QAC adsorption, inhibition, and biotransformation on the fate and effect of QACs in BNR systems. A laboratory-scale, multi-stage BNR system was continuously fed with real poultry processing wastewater amended with a mixture of three benzalkonium chlorides. The nitrogen removal efficiency initially deteriorated at a BAC feed concentration of 5 mg/L due to complete inhibition of nitrification. However, the system recovered after 27 days of operation achieving high nitrogen removal efficiency, even after the feed BAC concentration was stepwise increased up to120 mg/L. Batch assays performed using the mixed liquors of the BNR system reactors, before, during, and post BAC exposure, showed that the development of BAC biotransformation capacity and the acquisition of resistance to BAC contributed to the recovery of nitrification and nitrogen removal. Kinetic analysis based on sub-models representing BNR processes showed that BAC inhibition of denitrification and nitrification is correlated with BAC liquid-phase and solid-phase concentrations, respectively. Simulations using a comprehensive mathematical BNR model developed for this research showed that BAC degradation and the level of nitrification inhibition by BAC were dynamic brought about by acclimation and enrichment of the heterotrophic and nitrifying microbial populations, respectively. The fate and effect of BACs in the BNR system were accurately described when the interactions between adsorption, inhibition, and resistance/biotransformation were considered within the conditions prevailing in each reactor. This work is the first study on the fate and effect of antimicrobial QACs in a continuous-flow, multi-stage BNR system, and the first study to quantify and report parameter values related to BAC inhibition of nitrification and denitrification. Results of this study enable the rational design and operation of BNR systems for the efficient treatment of QAC-bearing wastewater. The outcome of this research provides information presently lacking, supporting the continuous use of QACs as antimicrobial agents in food processing facilities, when and where needed, while avoiding any negative impacts on biological treatment systems and the environment.

Corrosion and stress corrosion cracking of structural components cost an estimated $300 billion annually in the United States alone and are a safety concern for a number of industries using hot alkaline environments. These process environments may contain different amounts of sulfide and chloride; however, the combined role of these ions on the stress corrosion cracking of duplex stainless steels, which are widely used because of their generally reliable performance, had never been studied. This study shows that chlorides in sulfide-containing caustic environments actually have a significant influence on the performance of these alloys. A mechanism for stress corrosion cracking of duplex stainless steels in hot alkaline environments in the presence of sulfide and/or chloride was proposed. Microstructural and environmental aspects were studied using mechanical, electrochemical, and film characterization techniques. The results showed that selective corrosion of the austenite phase depended on percent sulfidity, alkalinity, and chloride content. Chlorides enhanced crack initiation and coalescence along the austenite/ferrite phase boundaries. Unstable passivity of duplex stainless steels in hot alkaline-sulfide environments was due to anion adsorption on the surface leading to defective film formation. Chlorides and sulfide available at the electrolyte/film surface reduced the charge transfer resistance and shifted the response of the films to lower frequencies indicating the films became more defective. The surface films consisted of an outer, discontinuous layer, and an inner, barrier layer. Fe, Mo, and Mn were selectively dissolved in alkaline and alkaline-sulfide environments. The onset of stress corrosion cracking was related to the extent of selective dissolution and was consistent with a film breakdown and repair mechanism similar to slip-step dissolution. Recommendations for reducing the susceptibility of duplex stainless steels to stress corrosion cracking in sulfide-containing caustic environments include reducing the chloride to hydroxide ratio and alloying with less Mo and Mn. The results will impact the petrochemical, pulp and paper, and other process industries as new duplex grades can be developed with optimal compositions and environments can be controlled to extend equipment life.

The UV-Visible spectra of a-C composites and nano composites have provided a very useful information about the electronic states and band structure. The UV-Visible spectra of a-C as well as nanoparticle are qualitatively similar. They do not show any absorption cutoff in wavelength (_max). In fact they are good absorbers of UV-Visible light in whole range. Composites show some absorptions which could be the combined effect of filler as we as host matrix. Since there is no _max, hence it is very unlikely to define any optical band gap. The nanoparticle is a good absorber in midinfrared compared to a-C. That may be due to presence of complicated kind of vibrational modes of carbon cased nanoparticle.Besides Fe3C also produces some additional modes. With kind of spectrum we have it is difficult to identify the different modes unambiguously for nanoparticle. The combined effects of filler as well as host polymer are reflected in both sets of composites. A new absorption is observed in a-C as well as in nanoparticle composites at 2370 cm−1 and 3462 cm−1 respectively. This peak may arise in composites due to interaction between filler and host matrix. The thermo gravimetric analysis is a useful characterization techniques for polymer and composites. It gives the information about the stability, phase change, degradation, chemical reaction and many more. The a-C composites as well as nano composites are stable up to 200_ C. These composites can be safely used for any practical purpose below this temperature. During the synthesis of composites the filler does not take part in any reaction. This fact is reflected in the DTG curve. The composites degrade in the way host polymer degrades.

<p>The local corrosion behavior of duplex stainless steel (DSS)is affected by a wide variety of factors. Localized corrosionof DSS frequently starts at micrometer scale inclusions orprecipitates, which are often segregated in theaustenite-ferrite boundary regions. Moreover, due to thepartitioning of the key alloying elements of ferrite (Cr andMo) and austenite (N and Ni), the local interactions betweenthe phases must also be considered.</p><p>The aim of this doctoral study was to increase the knowledgeabout the local dissolution behavior of DSS in acidic-chlorideenvironments. The recent developments of new local probingtechniques have opened a new frontier in corrosion science,providing valuable local information not accessible in thepast. The local techniques used include electrochemicalscanning tunneling microscopy (EC-STM), scanning probe forcemicroscopy (SKPFM), magnetic force microscopy (MFM), andscanning Auger electron Spectroscopy (SAES), all withmicrometer or sub-micrometer resolution.</p><p>With EC-STM, it was possible to monitor local dissolutionprocesses on DSS in situ, and in real time. MFM was capable ofimaging the phase distribution in DSS without the need of thetraditional surface etching, while SKPFM revealed that theVolta potential difference between the two phases wasmeasurable and significant. SAES showed that the compositiongradient at the phase boundaries is narrower than 2µm.</p><p>Different types of DSSs have been studied, from low-alloyedDSS to superduplex. Higher contents of Cr, Mo and Nstrengthened both phases as well as the phase boundaries,resulting in phases having similar corrosion resistance thatshowed a more uniform dissolution behavior. However, the Voltapotential difference between the phases proved to be of thesame order for all the DSSs studied. Austenite was in generalassociated to regions displaying a more noble Volta potentialthan ferrite, resulting in a higher dissolution rate of theferrite next to the austenite phase.</p><p><b>Key words:</b>In situ, local dissolution, electrochemical,STM, SKPFM, MFM, SAES, duplex stainless steel, acidic-chloridesolution.</p>

<p>A road in operation along with its traffic can pose aserious pollutant threat to groundwater and surface water inits vicinity. Examples of pollutants are metals from thecorrosion of vehicles, rails and poles and the wear of roadsurfaces and tyres; hydrocarbons from the wear of roadsurfaces, tyres, exhausts, oils; sodium chloride from roadsalt; and hazardous goods discharged in accidents. Eventuallypollutants that are not degraded or retarded in soil will reachgroundwater and surface water. The chloride ion in deicing saltis a good tracer. It is conservative and highly soluble and notsubject to retardation or degradation. If the chlorideconcentration has increased in groundwater or surface water inthe vicinity of a deiced road, other road-related pollutantsmight also be present in the water.</p><p>Increased chloride concentrations have been observed inseveral water supplies, in groundwater as well as in surfacewater, since the 1970s. The number of affected water supplieshas also increased. The increase in chloride concentration inwaters is concurrent with the increase in deicing saltapplication and it is clear that most of the increase is due tothe application of deicing salt.</p><p>The thesis presents a simple tool that quantified theincrease in chloride concentration for water in a catchmentarea, based on a steady-state water balance. The data wereefficiently processed and presented as maps with GIS. At aregional catchment area scale, substantially increased chlorideconcentrations were calculated. The variation between catchmentareas was verified by a national monitoring programme of lakes.Deicing salt application was estimated to account for more thanhalf of the total chloride load for a catchment area in the midsouth of Sweden.</p><p>A distributed dynamic method was used to evaluate thetemporal and spatial variation of the chloride concentration inan aquifer. The distributed dynamic approach integrated thespreading of deicing salt from the road with the infiltrationin the unsaturated zone in the soil, which in turn wasintegrated with the groundwater flow. The simulation was runfor a 40-year period and showed a potential to describe aspecific system.</p><p><b>Keywords:</b>road, deicing salt, monitoring, chloride,catchment area, river basin, simulation, GIS, groundwater,surface water</p>

<p>In the chlorate process, natural convection arises thanks to the hydrogen evolving cathode. This increases the mass transport of the different species in the chlorate electrolyte. There is a strong connection between mass transport and the kinetics of the electrode reactions. A better knowledge about these phenomena and their interactions is desirable in order to understand e.g. the reasons for deactivation of anode coatings and what process conditions give the longest lifetime and the highest efficiency.</p><p>One of the aims of his work was to understand how the chlorate process has to be run to avoid exceeding the critical anode potential (<em>E</em>_cr) in order to keep the potential losses low and to achieve a long lifetime of the DSAs. At <em>E</em>_cr anodic polarisation curves in chlorate electrolyte bend to higher Tafel slopes, causing increasing potential losses and accelerated ageing of the anode. Therefore the impact on the anode potential and on <em>E</em>_cr of different electrolyte parameters and electrolyte impurities was investigated. Additionally, the work aimed to investigate the impact of an addition of chromate on oxygen evolution and concentration profiles under conditions reminiscent of those in the chlorate process (high ionic strength, 70 °C, ruthenium based DSA, neutral pH), but without chloride in order to avoid hypochlorite formation. For this purpose a model, taking into account mass transport as well as potential- and concentration-dependent electrode reactions and homogeneous reactions was developed. Water oxidation is one of the side reactions considered to decrease the current efficiency in chlorate production. The results from the study increase the understanding of how a buffer/weak base affects a pH dependent electrode reaction in a pH neutral electrolyte in general. This could also throw light on the link between electrode reactions and homogeneous reactions in the chlorate process.</p><p>It was found that the mechanism for chloride oxidation is likely to be the same for potentials below <em>E</em>_cr as well as for potentials above <em>E</em>_cr. This was based on the fact that the apparent reaction order as well as α_a seem to be of the same values even if the anode potential exceeds<em> E</em>_cr. The reason for the higher slope of the polarisation curve above <em>E</em>_cr could then be a potential dependent deactivation of the active sites. Deactivation of active ruthenium sites could occur if ruthenium in a higher oxidation state were inactive for chloride oxidation.</p><p>Concentration gradients of H⁺, OH^-, CrO₄ ^2- and HCrO₄ ^-during oxygen evolution on a rotating disk electrode (RDE) were predicted by simulations. The pH dependent currents at varying potentials calculated by the model were verified in experiments. It was found that an important part of the chromate buffering effect at high current densities occurs in a thin (in the order of nanometers) reaction layer at the anode. From comparisons between the model and experiments a reaction for the chromate buffering has been proposed. Under conditions with bulk pH and chromate concentration similar to those in the chlorate process, the simulations show that the current density for oxygen evolution from OH^- would be approximately 0.1 kA m^-2, which corresponds to about 3% of the total current in chlorate production.</p>