In this research the environmental effects related to the position of a redox moiety with the electrochemical double layer were studied. This project was made possible with the synthesis of a series of lengths of ferrocene derived alkanethiols, a series of lengths of ferrocene derived norbornylogous bridges and a series of lengths of anthraquinone derived norbornylogous bridges. The series of ferrocene derived alkanethiols were used to study the effect of gradually varying the polarity of the self-assembled monolayers (SAMs) surface on the standard electron transfer rate constant and formal potential. This was achieved by varying the portion of hydroxyl to methyl terminated alkanethiol diluent in the SAM preparation step. It was found that the formal potential increased with a decreasing proportion of hydroxyl terminated diluent and increasing length of the diluent. For pure hydroxyl terminated diluent the formal potential was relatively independent of length. It was found that the rate constant increased for short alkane chain lengths with decreasing proportion of hydroxyl terminated diluent. However, it decreased in magnitude with long alkane chain lengths for low proportions of hydroxyl terminated diluent. The norbornylogous bridges were shown to stand proud above the diluent with a similar tilt angle as the alkanethiol diluent. The ferrocene derived norbornylogous bridges showed hydroxyl terminated monolayers had a slower rate constant then methyl terminated diluents independent of length and that it is highly probable that an alkane bridged redox moiety is located very close to the surface of the monolayer. SAMs were created with the ferrocene of the ferrocene derived norbornylogous bridges located at various heights above the monolayers surface. This was done by using various lengths of hydroxyl terminated diluent. It was found that the rate constant and the formal potential decreased with height above the surface. Interfacial potential distribution was used to account for this and to estimate a ??true?? formal potential. The anthraquinone derived norbornylogous bridges were tested at various pH values and heights above the surface. It was found that an accurate estimate for the electron transfer mechanism can not be made for surface bound species due to the effects of interfacial potential distribution. They demonstrated a novel technique for estimating the point of zero charge of the electrode.

Thesis (Ph.D.)--University of Melbourne, School of Chemistry, 2006. / Typescript. Includes bibliographical references.

abstract: Scarcity of potable water is one of the major problems faced in the world today. Majority of this problem can be solved if technology is developed to obtain potable water from brackish or saline water. The present desalination methods face challenges such as high costs in terms of energy consumption and infrastructure, physical size of the system, requirement of membrane and high pressure systems and hence have been facing various issues in implementation of the same. This research provides a new low pressure, low energy, portable method to desalinate water without the need for separation membranes, heat or chemical reactions. This method is energy efficient, cost effective, compact, environment friendly and suitable for portable desalination units. This technology, named as Polyphase Alternating current Bi-Ionic Propulsion System (PACBIPS) makes use of polyphase alternating current source to create a gradient in salt concentration. The gradient in salt concentration is achieved due to the creation of a traveling wave which attracts anions on its positive peak (crests) and cations on its negative peak (troughs) and travels along a central pipe thereby flushing the ions down. Another method of PACBIPS is based on Helmholtz capacitor which involves the formation of an electric double layer between the electrode and electrolyte consisting of equal and opposite ions which can be approximated as a capacitor. Charging and discharging this capacitor helps adsorb the ions onto a carbon electrode which has high surface area and electrical conductivity. This desalinates seawater and provides pure water. Mathematical modeling, analysis and implementation of the two methods have been presented in this work. The effects of zeta potential, electric field screening, electric mobility on desalination have been discussed. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2014

O aÃo ABNT 1045 tem aplicaÃÃo em diversos componentes utilizados na indÃstria do petrÃleo. Devido Ãs condiÃÃes severas de serviÃo, a ocorrÃncia de quebras e desgastes nestes equipamentos à freguente. A recuperaÃÃo à feita utilizando-se um processo de soldagem. PorÃm, aÃos com mÃdio teor de carbono exigem cuidados, pois o ciclo tÃrmico de soldagem promove uma microestrutura de elevada dureza e baixa tenacidade. Considerando-se este problema, aplicou-se as TÃcnicas da Dupla e Tripla Camadas, na soldagem do aÃo ABNT 1045, com eletrodos revestidos AWS E 7018-1 e AWS E 307-16. Para viabilizar o procedimento de soldagem multipasses os resultados obtidos foram aplicados na execuÃÃo de juntas do tipo semi-V. Realizou-se o amanteigamento em duas camadas, utilizando-se quatro relaÃÃes de energia (5(5, 5/10, 10/5, 10/10 kJ/cm) para o eletrodo AWS E 307-16 e cinco (5/5, 5/10, 10/5, 10/10, 10/16 kJ/cm) para o eletrodo AWS E 7018-1. Para o eletrodo inoxidÃvel foi realizado tambÃm o amanteigamento com trÃs camadas utilizando-se trÃs relaÃÃes de energia (5/5/5, 5/10/10 e 10/10/10 kJ/cm). Foi feito o levantamento do perfil de microdureza da ZAC da primeira camada do amanteigamento para cada corpo de prova semi-V. Para avaliar a eficiÃncia da tÃcnica quanto à tenacidade foi realizado o ensaio de impacto Charpy-V da ZAC a temperatura ambiente nas condiÃÃes como soldado e com TTPS. O entalhe dos corpos de prova Charpy foi posicionado na ZAC-GG da primeira camada a 1 mm da zona de ligaÃÃo (regiÃo mais critica). Foi realizado, tambÃm, ensaio de impacto Charpy no metal de solda, localizando o entalhe na regiÃo com maior relaÃÃo percentual entre as zonas colunar e recristalizada. Concluiu-se que as TÃcnicas da Dupla e da Tripla Camada mostraram-se eficientes, pois para toda as relaÃÃes de energias aplicadas, utilizando-se os dois tipos de eletrodos, alcanÃou-se tenacidade semelhante à obtida nos corpos de prova com Tratamento TÃrmico PÃs Soldagem e muito superior a tenacidade do metal de base / The AISI 1045 has application in various components used in the petroleum industry. Due to the harsh conditions of service, the occurrence of breakage and wear such equipment is freguente. Recovery is performed using a welding process. However, steels having average carbon contents require care, since the thermal cycle of welding promotes a microstructure with high hardness and low tenacity. Considering this problem, we applied the techniques of double and triple layers in welding of AISI 1045 with coated electrodes AWS and AWS E 7018-1 E 307-16. To enable the multipass welding procedure results were applied in the execution of joints in the semi-V. The buttering is carried out in two layers, using four energy ratios (five (5, 5/10 10/5, 10/10 kJ / cm) for the electrode AWS E 307-16 and five (5/5 , 5/10 10/5 10/10 10/16 kJ / cm) to the electrode and AWS 7018-1. For steel electrode was also performed with the buttering three layers using three energy ratios (5 / 5/5, 10/05/10 and 10/10/10 kJ / cm). was made of the profile of the hardness of HAZ of the first layer of the buttering for each specimen semi-V. To evaluate the efficiency of technique and the toughness test was performed Charpy-V impact of HAZ at room temperature under the conditions as welded and PWHT. The notch Charpy the samples was placed in HAZ-GG of the first layer 1 mm of the bonding zone ( most critical region). was carried out, also, Charpy impact test in the weld metal, locating the notch in the region with the highest ratio between columnar and recrystallized zones. It was concluded that the techniques of Double and Triple Layer proved efficient, because for all the relations of energy applied, using both types of electrodes was reached toughness similar to that obtained in specimens with Post Weld Heat Treatment and much higher than the toughness of base metal

This works begins by providing motivation for additional research and political interest in the use of passenger railway systems as a method of ‘green’ transportation. Additional motivation for the adoption of energy saving methods within new and existing railway systems is also provided. This motivation stems from the relatively small carbon dioxide emissions per passenger kilometer and large quantity of electrical energy used in association with passenger railway systems. In specific cases, both theoretical analyses and experimental implementations of energy storage in railway systems have shown a reduction in electrical energy use and/or vehicle performance gains. Current railway energy storage systems (ESS) commonly make use of battery or electric double layer capacitor (EDLC) cells. A review of select energy storage technologies and their application in railway systems is provided. For example, the developing Qatar Education City People Mover system makes use of energy dense batteries and power dense EDLCs to provide the range and power needed to operate without a conventional railway power source between stations, formally called catenary free operation. As an alternative to combining two distinct energy storage technologies, this work looks at experimentally characterizing the performance of commercially available lithium ion capacitors (LiCs); a relatively new energy storage cell that combines characteristics of batteries and EDLCs into one cell. The custom cell testing apparatus and lab safety systems used by this work, and others, is discussed. A series of five tests were performed on two EDLC cells and five LiC cells to evaluate their characteristics under various electrical load conditions at multiple temperatures. The general conclusion is that, in comparison to the EDLC cells tested, the LiC cells tested offer a superior energy density however, their power capabilities are relatively limited, especially in cold environments, due to larger equivalent series resistance values. The second topic explored in this work is the development of a MATLAB based DC powered passenger vehicle railway simulation tool. The simulation tool is connected to the experimental analysis of EDLC and LiC cells by comparing the volume and mass of an energy storage system needed for catenary free (no conventional DC power supply) operation between train stations using either energy storage technology. A backward facing modelling approach is used to quantify the drive cycle electrical power demands as a function of multiple vehicle parameters and driving parameters (eg. acceleration rate, travel distance and time). Additional modelling methods are provided as a resource to further develop the simulation tool to include multiple vehicles and their interactions with the DC power supply. Completion of the multi-vehicle simulation tool with energy storage systems remains a task for future work. / Thesis / Master of Applied Science (MASc)

The properties of electrochemical interfaces are studied using Fourier transform infrared spectroscopy. Potential difference infrared spectroscopy (PDIRS) was used in the investigation of carbon monoxide adsorbed on polycrystalline platinum electrodes. It is found that the infrared peak position of adsorbed carbon monoxide is linearly dependent on the applied electrode potential, and that the Stark tuning rate is a function of system temperature. The change in Stark tuning rate is the result of the variation of the interfacial dielectric constant with temperature. Self-assembled alkoxyalkanethiol monolayers were formed on gold substrates as surface modifiers of low dielectric constant designed to influence the interfacial capacitance. Polarization modulation infrared spectroscopy (PMIRS), ellipsometry, interfacial wetting, and cyclic voltammetry were conducted to characterize the modified interfaces. The interfacial capacitance is greatly reduced due to the adsorption of w-mercapto ethers on substrates. It was found that the solvation of the monolayer by solution is capable of improving the mass transport to maintain the Faradaic current while lowering the interfacial capacitance. The oxygen group in w-mercapto ethers at the monolayer-water interface interacts with water molecules to improve the monolayer solubility in water. The w-mercapto ether monolayers were found to be fluid-like in structure, giving better freedom to undergo structural change. The repulsion from the oxygen atoms in adjacent w-mercapto ether molecules adsorbed on the substrate introduces structural disorder to the alkyl chains in the monolayer, allowing better solvent permeation. This relieves some of the current blocking character of long chain alkanethiol monolayers. The interfacial contact angle to water for the w-mercapto ether monolayers is dependent on the oxygen position in the monolayer. 12-Methoxydodecanethiol has the lowest contact angle among all the w-mercapto ethers studied while 12-butoxydodecanethiol through 12-hexoxydodecanethiol have similar contact angles due to the ether oxygen being buried beneath several layers of methylene groups. The film thickness is roughly proportional to the total number of methylene groups in the two alkyl chains on w- mercapto ethers. w-Mercapto ethers that have a longer alkyl chain between the oxygen and thiol tend to form thicker monolayers on the substrates. In situ PMIRS measurements show that w-mercapto ether monolayers do not undergo structural change in the alkyl chains when in contact with either water or acetonitrile. The terminal methyl group, however, suffers from a shift in infrared peak position to lower frequency, and a decrease in peak height as the result of solvent load. / Ph. D.

Ionomeric polymer transducers consist of an ion-exchange membrane plated with conductive metal layers on its outer surfaces. Such materials are known to exhibit electromechanical coupling under the application of electric fields and imposed deformation (Oguro et al., 1992; Shahinpoor et al., 1998). Compared to other types of electromechanical transducers, such as piezoelectric materials, ionomeric transducers have the advantage of high-strain output (> 9% is possible), low-voltage operation (typically less than 5 V), and high sensitivity in the charge-sensing mode. A series of experiments on actuators with various ionic polymers such as Nafion and novel poly(Arylene ether disulphonate) systems (BPS and PATS) and electrode composition demonstrated the existence of a linear correlation between the strain response and the capacitance of the material. This correlation was shown to be independent of the polymer composition and the plating parameters. Due to the fact that the low-frequency capacitance of an ionomer is strongly related to charge accumulation at the electrodes, this correlation suggests a strong relationship between the surface charge accumulation and the mechanical deformation in ionomeric actuators. The strain response of water-hydrated transducers varies from 50 μstrain/V to 750 μstrain/V at 1Hz while the strain-to-charge response is between 9 ^μstrain_{^c_m²} and 15 ^μstrain_{^c_m²}. This contribution suggests a strong correlation between cationic motion and the strain in the polymer at the ionomer-conductor interface. A novel fabrication technique for ionic polymer transducers was developed for this dissertation for the purpose of quantifying the relationship between electrode composition and transducer performance. It consists of mixing an ionic polymer dispersion (or solution) with a fine conducting powder and attaching it to the membrane as an electrode. The Direct Assembly Process (DAP) allows the use of any type of ionomer, diluent, conducting powder, and counter ion in the transducer, and permits the exploration of any novel polymeric design. Several conducting powders have been incorporated in the electrode including single-walled carbon nanotubes (SWNT), polyaniline (PANI) powders, high surface area RuO2, and carbon black electrodes. The DAP provided the tool which enabled us to study the effect of electrode architecture on performance of ionic polymer transducers. The DAP allows the variation in the electrode architecture which enabled us to fabricate dry transducers with 50x better performance compared to transducers made using the state of the art impregnation-reduction technique. DAP fabricated transducers achieved a strain of 9.4% at a strain rate of 1%/s. Each electrode material had an optimal concentration in the electrode. For RuO2, the optimal loading was approximately 45% by volume. This study also demonstrated that carbon nanotubes electrodes have an optimal performance at loadings around 30 vol%, while PANI electrodes are optimized at 95 vol%. Extensional actuation in ionic polymer transducers was first reported and characterized in this dissertation. An electromechanical coupling model presented by Leo et al. (2005) defined the strain in the active areas as a function of the charge. This model assumed a linear and a quadratic term that produces a nonlinear response for a sine wave actuation input. The quadratic term in the strain generates a zero net bending moment for ionic polymer transducers with symmetric electrodes, while the linear term is canceled in extensional actuation for symmetric electrodes. Experimental results demonstrated strains on the order of 110 μstrain in the thickness direction compared to 1700 μstrain peak to peak on the external fibers for the same transducer, could be achieved when it is allowed to bend under +/-2V potential at 0.5 Hz. Extensional and bending actuation in ionic polymer transducers were explained using a bimorph active area model. Several experiments were performed to compare the bending actuation with the extensional actuation capability. The active area in the model was assumed to be the high surface area electrode. Electric double layer theory states that ions accumulate in a thin boundary layer close to the metal-polymer interface. Since the metal powders are evenly dispersed in the electrode area of the transducer, this area is expected to actuate evenly upon voltage application. This active area model emphasizes the importance the boundary layer on the conductor-ionomer interfacial area. Computing model parameters based on experimental results demonstrated that the active areas model collapses the bending data from a maximum variation of 200% for the strain per charge, to less than 68% for the model linear term. Furthermore, the model successfully predicted bending response from parameters computed using thickness experimental results. The prediction was particularly precise in estimating the trends of non-linearity as a function of the amount of asymmetry between the two electrodes. / Ph. D.

The electrical potential differences which arise across the length of capillary tubes containing 1 N perchloric acid and mercury drops are studied experimentally and theoretically for constant acceleration and different lengths of the drops of mercury. A relatively simple theory explains many features of the voltage on the experimental parameters. The results suggest that surface modes exist on the mercury drops which, in association with the Gibbs-Thompson effect, is the coupling between the mechanical and electrochemical phenomena. / Ph. D.

The present study presents the current status of research into the production of active carbons from environmental applications using waste newspaper. A number of studies have been performed to investigate the pyrolysis of waste paper ash to carbon gel.Although several studies report the production of carbon from waste tyre, bamboo, coconut shell, this study is first of its kind that for the first time, the waste newspapers have been used as a raw material for supercapacitor electrodes. A cheap raw material, and a simple method of preparation make this carbon gel more economically attractive. By carbonizing a waste paper a new carbon-carbon composite as electrode material was prepared through RF gel. The surface morphology and electrochemical characteristics of the carbon composite were investigated by Scanning Electron Microscopy, Cyclic Voltammetry, Electrochemical impedance spectroscopy and galvanostatic charge-discharge cycle tests with various current densities. The SEM study reveals that the connectivity between the grains increases during cycling thus enhances the cyclic stasitity. The CV’s suggests that there is simultaneous redox and capacitive behavior and these behaviors are highly reversible even after 8 lakh cycles. The reversibility was still maintained even in the range – 3 V to + 3 V. The charge/discharge cycle tests reveal the cycle stasitity and delivered more then 8 lakh cycles at 100 mA/cm2. The maximum specific capacitance of 300 F/g was obtained at 150 mA/cm2 current density. These results imply that this newspaper based carbon gel be used as potential candidate for supercapacitors.

Environmental separation processes such as removal of heavy metals from aqueous solutions, electrosorption in groundwater remediation, and capacitive desalination, as well as energy storage in supercapacitors, are based on the electrical double layer (EDL) formation within nanoporous carbon materials. This research is focused on the nano-scale phenomena of EDL formation inside the confined space of nanopores. The electrosorption behavior of nanoporous carbon materials was characterized by measuring the double-layer capacitance using cyclic voltammetry. The presence of micropores results in the occurrence of EDL overlapping, corresponding to a considerable loss of the double-layer capacitance. Hence, pore size distribution plays an important role in determining the double-layer capacitance. EDL formation has significant influence on ion transport and sorption inside nanopores. The data obtained by simple diffusion and electrochemically-aided diffusion experiments demonstrated the size-exclusion effects on pore accessibility by ions. A larger ion-exclusion volume prevents larger ions from penetrating inside the pores. Batch equilibrium electrosorption experiments using nanoporous carbon materials showed that selective electrosorption, imposed by the difference in the size of hydrated ions, occurs in a competitive environment. Molecular modeling based on Monte Carlo methods was developed to simulate the EDL formation in a slit-type nanopore. Simulation results indicated that the competition in asymmetries of ion charge and size not only determines the screening of surface charge but also affects the electrolyte distribution within charged pores. In a mixture of electrolytes, the charge/size competitive effects can dominate pore accessibility. Multivalent counterions with large size have the energetic advantage of screening surface charge. On the other hand, small monovalent counterions present a ¡§size affinity¡¨ to access the pores. Therefore, electrosorption selectivity of counterions with different properties is a result of a counterbalance between minimization of potential energy and size-exclusion effects. Manipulation of electrosorption selectivity to separate ions could in principle be achieved via tuning the EDL formation inside the pores. The findings of the thesis have several significant implications for the development of advanced techniques for selective separation of ions in environmental systems and energy storage.