Corosion behaviour of stainless steel in seawater : master thesis

Utjecaj temperature i koncentracije sulfidnih iona na korozijsko ponašanje nehrđajućih čelika 304L i 316L u morskoj vodi istraživan je različitim elektrokemijskim metodama. Tijekom istraživanja korištena su mjerenja potencijala otvorenog kruga, metode linearne i potenciodinamičke polarizacije. Utvrđeno je da se brzina korozije povećava s povećanjem temperature morske vode, a također i koncentracije sulfidnih iona. Analiza površine svjetlosnim mikroskopom i optičkim profilometrom nakon mjerenja potenciodinamičke polarizacije otkrila je da se broj i dubina jamica također povećavaju na isti način.The effect of temperature and concentration of sulphide ions on the corrosion behaviour of 304L and 316L stainless steels in seawater has been investigated by different electrochemical methods. Open circuit potential measurements, linear and potentiodynamic polarization methods have been employed during the investigation. It has been found that the corrosion rate increases with the seawater’s increasing temperature and the concentration of sulphide ions. Surface analysis with a light microscope and optical profilometer after potentiodynamic polarization measurements reveal that the number and depth of pits also increase in the same way

Nacija u krizi - privatnost i sigurnost kroz hollywoodski film

The goal of this analysis is to study the phenomena of the construction of national identity in the context of cultural representation, antagonization and demonization through the framework of Hollywood spy-movies and movies focused on the matters of mass surveillance and security. For this analysis, two movies based on real events (Snowden, Bridge of Spies) and two fictional movies were used in order to depict certain elements that are crucial in the portrayal of collective identity. Within this context the emphasis is placed on Benedict Anderson's concept of "imagined communities" along with other associated concepts of numerous other authors which were used in this analysis. Through the context of these cultural processes and phenomena the movie is interpreted as an "ideological machine" which enforces, promotes and perpetuates collective perception and values of a certain community, in this case, the United States of America.Cilj ove analize jest proučiti fenomen konstrukcije nacionalnog identiteta u kontekstu kulturne reprezentacije, antagonizacije, te demonizacije kroz okvir Hollywoodskih špijunskih filmova, te filmova fokusiranih na pitanja masivnog nadziranja i sigurnosti. Za ovu analizu su korištena dva filma temeljena na istinitim događajima (Snowden, Bridge of Spies), te dva fiktivna filma (Enemy of the State,The Pelican Brief) u svrhu oslikavanja određenih elemenata koji su ključni u prikazivanju i analizi kolektivnog identiteta. Unutar tog okvira se stavlja naglasak na koncept "zamišljenih zajednica" Benedicta Andersona, te na povezane koncepte mnogobrojnih drugih autora koji su korišteni unutar ove analize. Kroz kontekst ovih kulturnih procesa i fenomena se film postavlja kao svojevrsni "ideološki stroj" koji podupire, primjenjuje, te ovjekovječuje kolektivnu percepciju i vrijednosti određene zajednice, u ovom slučaju, Sjedinjenih Američkih Država

Corosion behaviour of stainless steel in seawater : master thesis

Utjecaj temperature i koncentracije sulfidnih iona na korozijsko ponašanje nehrđajućih čelika 304L i 316L u morskoj vodi istraživan je različitim elektrokemijskim metodama. Tijekom istraživanja korištena su mjerenja potencijala otvorenog kruga, metode linearne i potenciodinamičke polarizacije. Utvrđeno je da se brzina korozije povećava s povećanjem temperature morske vode, a također i koncentracije sulfidnih iona. Analiza površine svjetlosnim mikroskopom i optičkim profilometrom nakon mjerenja potenciodinamičke polarizacije otkrila je da se broj i dubina jamica također povećavaju na isti način.The effect of temperature and concentration of sulphide ions on the corrosion behaviour of 304L and 316L stainless steels in seawater has been investigated by different electrochemical methods. Open circuit potential measurements, linear and potentiodynamic polarization methods have been employed during the investigation. It has been found that the corrosion rate increases with the seawater’s increasing temperature and the concentration of sulphide ions. Surface analysis with a light microscope and optical profilometer after potentiodynamic polarization measurements reveal that the number and depth of pits also increase in the same way

Corosion behaviour of stainless steel in seawater : master thesis

Utjecaj temperature i koncentracije sulfidnih iona na korozijsko ponašanje nehrđajućih čelika 304L i 316L u morskoj vodi istraživan je različitim elektrokemijskim metodama. Tijekom istraživanja korištena su mjerenja potencijala otvorenog kruga, metode linearne i potenciodinamičke polarizacije. Utvrđeno je da se brzina korozije povećava s povećanjem temperature morske vode, a također i koncentracije sulfidnih iona. Analiza površine svjetlosnim mikroskopom i optičkim profilometrom nakon mjerenja potenciodinamičke polarizacije otkrila je da se broj i dubina jamica također povećavaju na isti način.The effect of temperature and concentration of sulphide ions on the corrosion behaviour of 304L and 316L stainless steels in seawater has been investigated by different electrochemical methods. Open circuit potential measurements, linear and potentiodynamic polarization methods have been employed during the investigation. It has been found that the corrosion rate increases with the seawater’s increasing temperature and the concentration of sulphide ions. Surface analysis with a light microscope and optical profilometer after potentiodynamic polarization measurements reveal that the number and depth of pits also increase in the same way

Effect of concentration of sodium chloride solution on liquid diffusion coefficient : bachelor thesis

Prijenos tvari je integralni dio brojnih procesa u kemijskom procesnom inženjerstvu. Ovisno o hidrodinamičkim uvjetima u sustavu taj prijenos se može odvijati molekularnim ili vrtložnim mehanizmom. U ovom radu se analizirala brzina prijenosa tvari isključivo molekularnim tj. difuzijskim mehanizmom. Sagledao se utjecaj koncentracije otopine natrijeva klorida, koja difundira kroz demineraliziranu vodu na vrijednost koeficijenta difuzije. Koeficijenti difuzije, čije numeričke vrijednosti daju direktan uvid u brzinu prijenosa difundirajuće tvari, u ovom slučaju određeni su eksperimentalno i primjenom jednadžbe Wilke-Changa. Rezultati eksperimentalnih mjerenja, za razliku od teorijskih, ukazuju da s povećanjem koncentracije otopine NaCl-a koeficijent difuzije poprima veću vrijednost. Eksperimentalno i teorijski određene numeričke vrijednosti tog koeficijenta ne pokazuju dobru podudarnost. Mogući razlozi navedenih odstupanja mogu biti eksperimentalne prirode, ali i u korištenju neodgovarajućeg analitičkog izraza u slučaju kada se radi o otopinama koje su po svojoj prirodi jaki elektroliti. Glavni uzroci eksperimentalnih pogrešaka mogu biti: nedovoljna izmiješanost otopine čija je provodnost određivana, temperaturne varijacije tijekom eksperimenta, pojava zračnih mjehurića u difuzijskoj ćeliji, konduktometrijska mjerenja koja su izvedena samo na jednoj lokaciji u posudi za miješanje, te eventualne pogreške pri pripravi otopina. U daljnjem radu bilo bi korisno svesti navedene eksperimentalne pogreške na najmanju moguću mjeru, te kod teorijskog određivanja koeficijenta difuzije primijeniti neki drugi izraz koji detaljnije uzima u obzir prirodu analizirane otopine.Mass transfer is an integral part of numerous processes in chemical engineering. Depending on the hydrodynamic conditions within the system, that transfer can occur through molecular diffusion or convection mechanism. In this thesis, mass transfer rate was analysed, focusing exclusively on molecular diffusion mechanism. The effect of concentration of sodium chloride solution on the diffusion coefficient was examined. Diffusion coefficients, whose numerical values give a direct insight in the mass transfer rate, in this work were determined experimentally and using Wilke-Chang’s equation. The results of the experimental measurements, as opposed to the theoretical values obtained, indicate that, with increasing NaCl solution concentration, the value of the diffusion coefficient increases as well. Experimentally and theoretically determined numerical values of the diffusion coefficient do not display an adequate congruence. The possible reasons for said deviation can be of experimental nature, but also caused by the utilization of an unsuitable equation, in the case of solutions which are strong electrolytes. The main causes of experimental errors could be: inadequate mixing of the solution whose electrical conductivity is being measured, variation in temperature during the experiment, the occurrence of air bubbles within the diffusion cell, conductometric measurements which were taken in only one position in the mixing vessel and eventual mistakes during the preparation of the solutions. In future work, it would be useful to minimize the effect of the said experimental mistakes, and to utilize a more suitable equation for the calculation of the theoretical diffusion coefficient, which takes into consideration the nature of the analysed solution in a more strict manner

Effect of concentration of sodium chloride solution on liquid diffusion coefficient : bachelor thesis

Prijenos tvari je integralni dio brojnih procesa u kemijskom procesnom inženjerstvu. Ovisno o hidrodinamičkim uvjetima u sustavu taj prijenos se može odvijati molekularnim ili vrtložnim mehanizmom. U ovom radu se analizirala brzina prijenosa tvari isključivo molekularnim tj. difuzijskim mehanizmom. Sagledao se utjecaj koncentracije otopine natrijeva klorida, koja difundira kroz demineraliziranu vodu na vrijednost koeficijenta difuzije. Koeficijenti difuzije, čije numeričke vrijednosti daju direktan uvid u brzinu prijenosa difundirajuće tvari, u ovom slučaju određeni su eksperimentalno i primjenom jednadžbe Wilke-Changa. Rezultati eksperimentalnih mjerenja, za razliku od teorijskih, ukazuju da s povećanjem koncentracije otopine NaCl-a koeficijent difuzije poprima veću vrijednost. Eksperimentalno i teorijski određene numeričke vrijednosti tog koeficijenta ne pokazuju dobru podudarnost. Mogući razlozi navedenih odstupanja mogu biti eksperimentalne prirode, ali i u korištenju neodgovarajućeg analitičkog izraza u slučaju kada se radi o otopinama koje su po svojoj prirodi jaki elektroliti. Glavni uzroci eksperimentalnih pogrešaka mogu biti: nedovoljna izmiješanost otopine čija je provodnost određivana, temperaturne varijacije tijekom eksperimenta, pojava zračnih mjehurića u difuzijskoj ćeliji, konduktometrijska mjerenja koja su izvedena samo na jednoj lokaciji u posudi za miješanje, te eventualne pogreške pri pripravi otopina. U daljnjem radu bilo bi korisno svesti navedene eksperimentalne pogreške na najmanju moguću mjeru, te kod teorijskog određivanja koeficijenta difuzije primijeniti neki drugi izraz koji detaljnije uzima u obzir prirodu analizirane otopine.Mass transfer is an integral part of numerous processes in chemical engineering. Depending on the hydrodynamic conditions within the system, that transfer can occur through molecular diffusion or convection mechanism. In this thesis, mass transfer rate was analysed, focusing exclusively on molecular diffusion mechanism. The effect of concentration of sodium chloride solution on the diffusion coefficient was examined. Diffusion coefficients, whose numerical values give a direct insight in the mass transfer rate, in this work were determined experimentally and using Wilke-Chang’s equation. The results of the experimental measurements, as opposed to the theoretical values obtained, indicate that, with increasing NaCl solution concentration, the value of the diffusion coefficient increases as well. Experimentally and theoretically determined numerical values of the diffusion coefficient do not display an adequate congruence. The possible reasons for said deviation can be of experimental nature, but also caused by the utilization of an unsuitable equation, in the case of solutions which are strong electrolytes. The main causes of experimental errors could be: inadequate mixing of the solution whose electrical conductivity is being measured, variation in temperature during the experiment, the occurrence of air bubbles within the diffusion cell, conductometric measurements which were taken in only one position in the mixing vessel and eventual mistakes during the preparation of the solutions. In future work, it would be useful to minimize the effect of the said experimental mistakes, and to utilize a more suitable equation for the calculation of the theoretical diffusion coefficient, which takes into consideration the nature of the analysed solution in a more strict manner

Effect of concentration of sodium chloride solution on liquid diffusion coefficient : bachelor thesis

Prijenos tvari je integralni dio brojnih procesa u kemijskom procesnom inženjerstvu. Ovisno o hidrodinamičkim uvjetima u sustavu taj prijenos se može odvijati molekularnim ili vrtložnim mehanizmom. U ovom radu se analizirala brzina prijenosa tvari isključivo molekularnim tj. difuzijskim mehanizmom. Sagledao se utjecaj koncentracije otopine natrijeva klorida, koja difundira kroz demineraliziranu vodu na vrijednost koeficijenta difuzije. Koeficijenti difuzije, čije numeričke vrijednosti daju direktan uvid u brzinu prijenosa difundirajuće tvari, u ovom slučaju određeni su eksperimentalno i primjenom jednadžbe Wilke-Changa. Rezultati eksperimentalnih mjerenja, za razliku od teorijskih, ukazuju da s povećanjem koncentracije otopine NaCl-a koeficijent difuzije poprima veću vrijednost. Eksperimentalno i teorijski određene numeričke vrijednosti tog koeficijenta ne pokazuju dobru podudarnost. Mogući razlozi navedenih odstupanja mogu biti eksperimentalne prirode, ali i u korištenju neodgovarajućeg analitičkog izraza u slučaju kada se radi o otopinama koje su po svojoj prirodi jaki elektroliti. Glavni uzroci eksperimentalnih pogrešaka mogu biti: nedovoljna izmiješanost otopine čija je provodnost određivana, temperaturne varijacije tijekom eksperimenta, pojava zračnih mjehurića u difuzijskoj ćeliji, konduktometrijska mjerenja koja su izvedena samo na jednoj lokaciji u posudi za miješanje, te eventualne pogreške pri pripravi otopina. U daljnjem radu bilo bi korisno svesti navedene eksperimentalne pogreške na najmanju moguću mjeru, te kod teorijskog određivanja koeficijenta difuzije primijeniti neki drugi izraz koji detaljnije uzima u obzir prirodu analizirane otopine.Mass transfer is an integral part of numerous processes in chemical engineering. Depending on the hydrodynamic conditions within the system, that transfer can occur through molecular diffusion or convection mechanism. In this thesis, mass transfer rate was analysed, focusing exclusively on molecular diffusion mechanism. The effect of concentration of sodium chloride solution on the diffusion coefficient was examined. Diffusion coefficients, whose numerical values give a direct insight in the mass transfer rate, in this work were determined experimentally and using Wilke-Chang’s equation. The results of the experimental measurements, as opposed to the theoretical values obtained, indicate that, with increasing NaCl solution concentration, the value of the diffusion coefficient increases as well. Experimentally and theoretically determined numerical values of the diffusion coefficient do not display an adequate congruence. The possible reasons for said deviation can be of experimental nature, but also caused by the utilization of an unsuitable equation, in the case of solutions which are strong electrolytes. The main causes of experimental errors could be: inadequate mixing of the solution whose electrical conductivity is being measured, variation in temperature during the experiment, the occurrence of air bubbles within the diffusion cell, conductometric measurements which were taken in only one position in the mixing vessel and eventual mistakes during the preparation of the solutions. In future work, it would be useful to minimize the effect of the said experimental mistakes, and to utilize a more suitable equation for the calculation of the theoretical diffusion coefficient, which takes into consideration the nature of the analysed solution in a more strict manner

Nacija u krizi - privatnost i sigurnost kroz hollywoodski film

The goal of this analysis is to study the phenomena of the construction of national identity in the context of cultural representation, antagonization and demonization through the framework of Hollywood spy-movies and movies focused on the matters of mass surveillance and security. For this analysis, two movies based on real events (Snowden, Bridge of Spies) and two fictional movies were used in order to depict certain elements that are crucial in the portrayal of collective identity. Within this context the emphasis is placed on Benedict Anderson's concept of "imagined communities" along with other associated concepts of numerous other authors which were used in this analysis. Through the context of these cultural processes and phenomena the movie is interpreted as an "ideological machine" which enforces, promotes and perpetuates collective perception and values of a certain community, in this case, the United States of America.Cilj ove analize jest proučiti fenomen konstrukcije nacionalnog identiteta u kontekstu kulturne reprezentacije, antagonizacije, te demonizacije kroz okvir Hollywoodskih špijunskih filmova, te filmova fokusiranih na pitanja masivnog nadziranja i sigurnosti. Za ovu analizu su korištena dva filma temeljena na istinitim događajima (Snowden, Bridge of Spies), te dva fiktivna filma (Enemy of the State,The Pelican Brief) u svrhu oslikavanja određenih elemenata koji su ključni u prikazivanju i analizi kolektivnog identiteta. Unutar tog okvira se stavlja naglasak na koncept "zamišljenih zajednica" Benedicta Andersona, te na povezane koncepte mnogobrojnih drugih autora koji su korišteni unutar ove analize. Kroz kontekst ovih kulturnih procesa i fenomena se film postavlja kao svojevrsni "ideološki stroj" koji podupire, primjenjuje, te ovjekovječuje kolektivnu percepciju i vrijednosti određene zajednice, u ovom slučaju, Sjedinjenih Američkih Država

Corrosion Behavior of Stainless Steel in Seawater in the Presence of Sulfide

The effect of temperature (from 288 to 308 K) and concentration of sulfide ions (up to 40 ppm) on the corrosion behavior of AISI 304L and AISI 316L stainless steels in seawater was studied with measurements of open-circuit potential, linear and potentiodynamic polarization, and electrochemical impedance spectroscopy. An increase in temperature and pollutant concentration negatively affects the corrosion stability of stainless steels at the open circuit (the resistance, compactness, and thickness of the surface layer decrease and the corrosion current increases), in the passive region (the passivation current increases, the depassivation potential decreases, and the passive potential region narrows), and in the transpassive potential region (the rate of metal dissolution increases). The occurrence of pitting corrosion on the surface of the samples was confirmed with optical microscopy and a non-contact 3D profilometer. A few large pits (depth 80–100 μm and width 100 μm) were formed on the surface of AISI 304L steel, while several smaller pits (depth 40–50 μm and width 50 μm) were formed on the surface of AISI 316L steel. With increasing temperature and sulfide ion concentration, the width, depth, and density of the pits increased on both steel samples. In the studied temperature and concentration range of sulfide ions, the AISI 316L steels exhibited higher corrosion resistance. Overall, the influence of sulfide ions on steel corrosion was more pronounced than the influence of temperature