The potential use of sodium propionate as a corrosion inhibitor for mild steel in aqueous media is investigated using a range of electrochemical and surface analytical techniques. The use of sodium propionate for the inhibition of mild steel corrosion is discussed, and the effective pH range of sodium propionate using various buffers is investigated. The effectiveness of sodium propionate as an inhibitor for mild steel pitting corrosion in the presence of various concentrations of CI- is studied. The effect of some oxidants, IO3-, BrO3-, NO32- on the anodic behaviour of mild steel in deaerated 0.01M carboxylate solutions of acetate, propionate, formate, succinate and salicylate is investigated. The critical temperature for effective inhibition of mild steel corrosion with sodium propionate is established, and the chemical composition of the film formed on mild steel surface in sodium propionate solution is studied using surface sensitive Fourier transform infrared spectroscopy FTIR. The efficiency of sodium propionate is compared to that of conventional inhibitors and a mechanism for the inhibition of mild steel corrosion with sodium propionate is proposed. / Doctor of Philosophy (PhD)

This research is to synthesize polyaniline (PANI) thin film for polymer solar cells as a hole transport layer by using potentiostatic deposition of electrochemical method. In our previous studies, we have shown that the power conversion efficiencies of the solar cell device were improved for the slow polymerization rate. We choose the potentiostatic deposition method to improve the polymerization rate of PANI for the application in industry. In this study, we investigated optical transmittance, absorption spectrum, Highest Occupied Molecular Orbital (HOMO), surface roughness, and surface morphology of the PANI thin film by changing voltages and to discuss the factors on device efficiency. Then, we compared the device structures with hole transport layer PEDOT: PSS by spin-coating process. We found PANI thin films synthesized from different voltages, and the transmittance measurement results were similar. In addition, we found HOMO, surface roughness, and surface morphology of PANI thin film that varies with different voltages. The power conversion efficiencies of the device mainly were affected by the surface roughness and morphology of PANI thin film surface. Comparing to other parameters, PANI thin film polymerized at 0.8V owns the most appropriate surface roughness and surface morphology. The power conversion efficiency was up to 1.52% under AM 1.5G illumination based on ITO (150 nm) / PANI (75 nm) / P3HT: PCBM (100 nm) / Al (200 nm), and the device area of 0.16 cm2.

Ensaios cronogalvanométricos, análises por difração de raios -X, microscopia eletrônica de varredura (MEV) e curvas de polarização potenciostáticas foram usadas com o propósito de caracterizar os filmes formados sobre o aço API T95 em soluções alcalinas de sulfeto de sódio (Na2S 0,02M). As características destes filmes foram analisadas em função do pH da solução. O pH usado em cada caso (entre 8 e 11) foi obtido através da injeção de gás sulfídrico (H2S) na solução previamente desarejada. As curvas de polarização potenciostáticas mostram o aparecimento de uma região passiva ou pseudo-passiva para os pHs mais elevados (1 O e 11 ). As curvas cronogalvanométricas permitiram verificar uma queda de densidade de corrente nestes mesmos pHs, evidenciando a melhor proteção contra a corrosão dos filmes de sulfeto formados nestas condições. / Chronogalvanometric electrochemical essays, X - ray diffraction analysis, scanning electron microscopy (SEM) and potentiostatic curves were used with the pourpose of characterizing the sulfide films formed on API T95 steel in alkaline sodium sulfide (Na2S 0,02M) environments. The characterization of these films were followed by pH measurements and the potential at witch they were formed. The pH of the used environments was varied between 8 and 11 through hydrogen sulfide (H2S) injection in the previously deaerated solution. Potentiostatic polarization curves indicate a pseudopassive or passive area in the highest pH values (1 O and 11 ). The chronogalvanometric curves show a decrease of current density, at the same pH, characterizing a better corrosion protection of the films formed in these conditions.

Ensaios cronogalvanométricos, análises por difração de raios -X, microscopia eletrônica de varredura (MEV) e curvas de polarização potenciostáticas foram usadas com o propósito de caracterizar os filmes formados sobre o aço API T95 em soluções alcalinas de sulfeto de sódio (Na2S 0,02M). As características destes filmes foram analisadas em função do pH da solução. O pH usado em cada caso (entre 8 e 11) foi obtido através da injeção de gás sulfídrico (H2S) na solução previamente desarejada. As curvas de polarização potenciostáticas mostram o aparecimento de uma região passiva ou pseudo-passiva para os pHs mais elevados (1 O e 11 ). As curvas cronogalvanométricas permitiram verificar uma queda de densidade de corrente nestes mesmos pHs, evidenciando a melhor proteção contra a corrosão dos filmes de sulfeto formados nestas condições. / Chronogalvanometric electrochemical essays, X - ray diffraction analysis, scanning electron microscopy (SEM) and potentiostatic curves were used with the pourpose of characterizing the sulfide films formed on API T95 steel in alkaline sodium sulfide (Na2S 0,02M) environments. The characterization of these films were followed by pH measurements and the potential at witch they were formed. The pH of the used environments was varied between 8 and 11 through hydrogen sulfide (H2S) injection in the previously deaerated solution. Potentiostatic polarization curves indicate a pseudopassive or passive area in the highest pH values (1 O and 11 ). The chronogalvanometric curves show a decrease of current density, at the same pH, characterizing a better corrosion protection of the films formed in these conditions.

Ensaios cronogalvanométricos, análises por difração de raios -X, microscopia eletrônica de varredura (MEV) e curvas de polarização potenciostáticas foram usadas com o propósito de caracterizar os filmes formados sobre o aço API T95 em soluções alcalinas de sulfeto de sódio (Na2S 0,02M). As características destes filmes foram analisadas em função do pH da solução. O pH usado em cada caso (entre 8 e 11) foi obtido através da injeção de gás sulfídrico (H2S) na solução previamente desarejada. As curvas de polarização potenciostáticas mostram o aparecimento de uma região passiva ou pseudo-passiva para os pHs mais elevados (1 O e 11 ). As curvas cronogalvanométricas permitiram verificar uma queda de densidade de corrente nestes mesmos pHs, evidenciando a melhor proteção contra a corrosão dos filmes de sulfeto formados nestas condições. / Chronogalvanometric electrochemical essays, X - ray diffraction analysis, scanning electron microscopy (SEM) and potentiostatic curves were used with the pourpose of characterizing the sulfide films formed on API T95 steel in alkaline sodium sulfide (Na2S 0,02M) environments. The characterization of these films were followed by pH measurements and the potential at witch they were formed. The pH of the used environments was varied between 8 and 11 through hydrogen sulfide (H2S) injection in the previously deaerated solution. Potentiostatic polarization curves indicate a pseudopassive or passive area in the highest pH values (1 O and 11 ). The chronogalvanometric curves show a decrease of current density, at the same pH, characterizing a better corrosion protection of the films formed in these conditions.

Direct ethanol fuel cells are of interest due to the high energy density, ease of distribution and handling, and low toxicity of ethanol. Difficulties lie in finding a catalyst that can completely oxidize ethanol and resist poisoning by intermediate reaction species. Degradation of the catalyst layer over time is also an issue that needs to be addressed. In this work, niobium doped-titanium dioxide (Nb-TiO2) is investigated as a platinum (Pt) support due to its increased resistance to corrosion compared to the common catalyst support, carbon. It has also been seen in the literature that TiO2 is able to adsorb OH and assist in freeing Pt sites by further oxidizing COad to CO2 and thereby increasing the catalytic activity of catalysts toward ethanol oxidation. The TiO2 support is mixed with carbon, forming Nb-TiO2-C, in order to increase the conductivity throughout the support. The electrochemical activity and direct ethanol fuel cell (DEFC) performance of this novel catalyst is investigated and compared to that of two common catalysts, carbon supported Pt (Pt/C) and carbon supported platinum-tin (PtSn/C). While the conductivity of the Pt/Nb-TiO2-C electrodes was low compared to that of the carbon supported electrodes, the overall catalytic activity and performance of the TiO2 supported catalyst was comparable to that of the Pt/C catalyst based on the electrochemically active surface area. / Master of Science

Ceramic metal composites, or cermets, currently have widespread applications in the chemical, automotive and oil and gas sectors, due to their combination of high wear resistance, and aqueous corrosion resistance. In the present study, a family of novel titanium carbide (TiC)-stainless steel cermets has been produced as potential materials for use as erosion and corrosion resistant materials. The development of the TiC-stainless steel cermets is based on a simple melt infiltration technique, with the stainless steel “binder” contents varied from 5 to 30 vol.%, using the austenitic grades 304L and 316L, and the martensitic grade 410L. These materials have subsequently been evaluated for their wear and corrosion response, as well as characterisation of their basic mechanical properties and microstructure. Results from wear and corrosion studies show an improvement in wear and corrosion resistance of the cermets at lower steel binder content . / The original abstract from thesis is below. Ceramic metal composites, or cermets, currently have widespread applications in the chemical, automotive and oil and gas sectors, due to their combination of high wear resistance, and aqueous corrosion resistance. In the present study, a family of novel titanium carbide (TiC)-stainless steel cermets has been produced as potential materials for use as erosion and corrosion resistant materials. The development of the TiC-stainless steel cermets is based on a simple melt infiltration technique, with the stainless steel “binder” contents varied from 5 to 30 vol.%, using the austenitic grades 304L and 316L, and the martensitic grade 410L. These materials have subsequently been evaluated for their wear and corrosion response, as well as characterisation of their basic mechanical properties and microstructure. Reciprocating wear tests involved a ball-on-flat geometry (using a WC-Co counter face sphere), with loads varied from 20 to 80 N, for up to 120 minutes. The wear tracks were assessed using a high-resolution optical profilometer, in order to determine the wear volume. The specific wear rate of the cermets was found to increase with both the applied load and the steel binder content. To investigate the morphology of worn surfaces, scanning electron microscopy (SEM), and associated energy dispersive x-ray spectroscopy (EDS) were used, in order to fully understand the operative wear mechanisms. A transition from two- to three-body abrasive wear was observed, together with the formation of a oxygen-rich tribolayer, indicating that adhesive wear was also occurring on the cermets. In order to assess the electrochemical behaviour of the cermets in a simulated seawater environment, the samples were evaluated using potentiodynamic, cyclic and potentiostatic polarisation tests, with basic corrosion parameters and rates subsequently determined through Tafel extrapolation and weight loss measurement. Each stage of electrochemical assessment was then evaluated by characterising the corroded surfaces and solution using SEM, EDS and inductively coupled plasma optical emission spectrometry. Microstructural observations using SEM images revealed significant degradation of the samples, with steel binder preferentially dissolved while TiC remained relatively unaffected. The corrosion rate of the cermets increases with steel binder content, which is attributed to the preferential dissolution of the binder.

In realizing a portable chemical analysis system, adequate partitioning of a reusable component and a disposable is required. For successful implementation of micromachined sensors in an instrument, reliable methods for interconnection and interface are in great demand between these two major parts. This thesis work investigates interconnection methods of micromachined chip devices, a hybrid fluidic interface system, and measurement circuitry for completing instrumentation. The interconnection method based on micromachining and injection molding techniques was developed and an interconnecting microfluidic package was designed, fabricated and tested. Alternatively, a plug-in type design for a large amount of sample flow was designed and demonstrated. For the hybrid interface, sequencing of the chemical analysis was examined and accordingly, syringe containers, a peristaltic pump and pinch valves were assembled to compose a reliable meso-scale fluidic control unit. A potentiostat circuit was modeled using a simulation tool. The simulated output showed its usability toward three-electrode electrochemical microsensors. Using separately fabricated microsensors, the final instrument with two different designs--flow-through and plug-in type was tested for chlorine detection in water samples. The chemical concentration of chlorine ions could be determined from linearly dependent current signals from the instrument.

No description available.

A corrosão seletiva de fases de dois tipos de aços inoxidáveis fundidos foi analisada, ao serem submetidos a vários valores constantes de potencial, a partir da região catódica para a anódica da curva de polarização. Os aços estudados foram: austenítico (ACI CF-3M) solubilizado e martensítico (ACI CA-6NM) normalizado e revenido. As curvas de polarização foram traçadas potenciodinamicamente, a uma velocidade de varredura de 0,16 m.V.s-1 em solução aerada contendo H2SO4 1M e NaCl 1M, pH 0,35, à temperatura ambiente. Vários valores de potencial foram selecionados, previamente localizados nas regiões catódica, ativa, passiva e transpassiva da curva de polarização. Potenciostaticamente, foram atingidos os valores de potencial selecionados, sendo eles mantidos fixos por 1800 s. Após o ataque potenciostático, as aparências metalográficas dos aços foram verificadas, desde a região catódica até a anódica. Por microssonda eletrônica, foram quantificados os elementos químicos presentes nas fases dos aços. Para melhor avaliar o início de propagação de pite, foi determinada a porcentagem de íons liberados para o eletrólito, após a imposição de valores de potencial críticos de pite predeterminados pelas curvas de polarização, pelas aparências metalográficas e pelas curvas de densidade de corrente em função do tempo. / The selective corrosion of phases present in two types of cast stainless steels was analyzed, when submitled to several constant values of potential, starting from the cathodic to the anodic regions of the polarization curve. The cast stainless steels were: austenitic (ACI CF-3M) solubilized and martensitic (ACI CA-6NM) normalized and tempered. The polarization curves were obtained at a scanning rate of 0.16 mV.s-1 in 1M H2S04 and 1M NaCI solution, pH 0.35 and at room temperature. Several potential values were selected, previously located in the cathodic, active, passive and transpassive regions of the polarization curve. The values of the selected potential were maintained fixed for 1800 s. After the potentiostatic etching, the metallographic appearances of the steels were verified, from the cathodic to the anodic region. Through electronic microprobe analysis, the present chemical elements were quantified in the phases of the steels. For betler evaluating the beginning of pitling propagation in the studied steels, liberated ion percentage for the solution was determined, after the imposition of critic pitting potential values predetermined from the polarization curves, through the metallographic appearances obtained after potentiostatic etching of the samples and the current density curves as a function of time.