Thesis (PhD)--University of South Australia, 1995

No description available.

Nanostructured materials have potential technological applications due to their characteristic dimensions. The material performance will depend on the atomic structure, and composition of these materials. This thesis focuses on proposing a reliable method for fabricating nanoporous alumina and palladium nanoparticles inside the templates.Palladium nanoparticles were synthesized in commercial porous alumina templates using electrodeposition. Pores within these nanoporous membranes act as templates for the synthesis of nanostructures of the desired material. Electrodeposition is achieved using a three-terminal set-up and a potentiostat. Different types of deposition techniques were investigated to improve the distribution of the deposit. The nanoparticles were characterized by SEM/EDX for composition. The commercial templates have high aspect ratio, but are not hexagonally ordered. Hence porous alumina was fabricated in the laboratory by anodization of aluminum.

The thin-layer flow-cell incorporated an array of 32 gold strip electrodes in a serial configuration opposite a platinum counter electrode. The cell body was made of Macor glass ceramic. A photolithographic procedure for etching the Macor and a simple method of applying a gold ink was devised. Resistive feedback current-to-voltage converters independently controlled the potential difference between the electrodes of the array and the common counter electrode. A microcomputer and a customized high speed data acquisition interface recorded the current response of each electrode. An expression for the faradaic response of a single electrode within a rectangular flow channel was modified to predict the behavior of the multi-electrode flow-cell. The quinone/hydroquinone redox system was used to evaluate the performance of the detector. Summing the signals from the array when all electrodes were held at the same potential improved the signal-to-noise ratio. Hydrodynamic curves were reconstructed from the currents measured at each electrode when a ramp potential profile was applied to the array.

abstract: Microbial fuel cells(MFC) use micro-organisms called anode-respiring bacteria(ARB) to convert chemical energy into electrical energy. This process can not only treat wastewater but can also produce useful byproduct hydrogen peroxide(H2O2). Process variables like anode potential and pH play important role in the MFC operation and the focus of this dissertation are pH and potential control problems. Most of the adaptive pH control solutions use signal-based-norms as cost functions, but their strong dependency on excitation signal properties makes them sensitive to noise, disturbances, and modeling errors. System-based-norm( H-infinity) cost functions provide a viable alternative for the adaptation as they are less susceptible to the signal properties. Two variants of adaptive pH control algorithms that use approximate H-infinity frequency loop-shaping (FLS) cost metrics are proposed in this dissertation. A pH neutralization process with high retention time is studied using lab scale experiments and the experimental setup is used as a basis to develop a first-principles model. The analysis of such a model shows that only the gain of the process varies significantly with operating conditions and with buffering capacity. Consequently, the adaptation of the controller gain (single parameter) is sufficient to compensate for the variation in process gain and the focus of the proposed algorithms is the adaptation of the PI controller gain. Computer simulations and lab-scale experiments are used to study tracking, disturbance rejection and adaptation performance of these algorithms under different excitation conditions. Results show the proposed algorithm produces optimum that is less dependent on the excitation as compared to a commonly used L2 cost function based algorithm and tracks set-points reasonably well under practical conditions. The proposed direct pH control algorithm is integrated with the combined activated sludge anaerobic digestion model (CASADM) of an MFC and it is shown pH control improves its performance. Analytical grade potentiostats are commonly used in MFC potential control, but, their high cost (>$6000) and large size, make them nonviable for the field usage. This dissertation proposes an alternate low-cost($200) portable potentiostat solution. This potentiostat is tested using a ferricyanide reactor and results show it produces performance close to an analytical grade potentiostat. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2018

Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2017-02-20T15:45:15Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - Alexandre K. P. Souza.pdf: 3464696 bytes, checksum: e78461b89f866435b0635d96ae2a3f7d (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2017-02-20T15:45:30Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - Alexandre K. P. Souza.pdf: 3464696 bytes, checksum: e78461b89f866435b0635d96ae2a3f7d (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2017-02-20T15:46:53Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - Alexandre K. P. Souza.pdf: 3464696 bytes, checksum: e78461b89f866435b0635d96ae2a3f7d (MD5) / Made available in DSpace on 2017-02-20T15:46:53Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - Alexandre K. P. Souza.pdf: 3464696 bytes, checksum: e78461b89f866435b0635d96ae2a3f7d (MD5) Previous issue date: 2016-12-16 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Electronic devices for applications in the field of electronic instrumentation in the offshoot of analytical chemistry research have great interest in the field of research related to the academic environment, as well as in the industrial environment. With the objective of extracting information and relevant data of chemical compounds, both from the qualitative point of view, as well as from the quantitative point of view, it is necessary in electrochemical analyzes, the presence of specific electrochemical sensors connected to electronic circuits, thus forming Electrochemical systems designed with the purpose of processing and extracting data information related to the physico-chemical effects occurring on the surface of the sensor due to reactions in the chemical substance or compound of interest in a particular analysis. This work deals with the research, study and development of topologies of electronic circuits, known as potentiostat, having as main objective, the task of conditioning of electrical signals from an electrochemical sensor, called electrochemical cell of three electrodes. The results demonstrated in this work are concentrated in the graphs of electrical voltages and currents, directly related to the chemical parameters of a sample under analysis, being these results obtained through experimental tests, applying the cyclic voltammetry method. Experimental tests were performed with circuit topologies connected to a cell, for the analysis of data obtained and validation of proposed potentiostat circuit topologies. / Dispositivos eletrônicos voltados para aplicações na área de instrumentação eletrônica no ramo de pesquisas em química analítica possuem grande interesse de desenvolvimento, nos campos de pesquisas relacionados ao meio acadêmico, assim como, no ambiente industrial. Com o objetivo de extrair informações e dados relevantes de compostos químicos, tanto do ponto de vista qualitativo, bem como do ponto de vista quantitativo, faz-se necessário em análises eletroquímicas, à presença de sensores eletroquímicos específicos conectados a circuitos eletrônicos, formando desta maneira sistemas eletroquímicos, projetados com a função de processar e extrair informações de dados relacionados aos efeitos físico-químicos, que ocorrem na superfície do sensor, devido a reações na substância ou composto químico de interesse em determinada análise. Este trabalho aborda a pesquisa, estudo e desenvolvimento de topologias de circuitos eletrônicos, conhecidos como potenciostato, tendo por tarefa o condicionamento de sinais elétricos provenientes de um sensor eletroquímico, designado de célula eletroquímica de três eletrodos. Os resultados demonstrados neste trabalho estão concentrados no levantamento de gráficos de sinais elétricos de tensões e correntes, relacionados diretamente a parâmetros químicos de uma amostra em análise, sendo estes resultados obtidos através de testes experimentais, aplicando o método de voltametria cíclica. Foram realizados testes experimentais com as topologias de circuitos conectados a uma célula, para a análise dos dados obtidos e validação das topologias de circuitos de potenciostatos propostos

This work deals with issues of lead detection in solder irons used in electrotechnics. The general aim is to study principles of quantitative heavy metal detection by the electrochemical methods, optimal method selection and construction of detecting instrument.

The work deals with n-channel system enabling many sample analysis at sort time from sensor array using electrochemical methods. The 8x12 sensor arrays are formed from 3 electrodes system created on PCB which can be used for heavy metal analysis and toxic substances determination. The control unit switches each 3 electrode sensor to 8 channel precise potentiostat which was designed for electrochemical analysis with current sensitivity below 10 pA. The potentiostat can synchronize with control unit. Developed system is able to measure up to eight single inputs and may be simply converted to measure other nonchemical values. Measured data will be sent to user-friendly application in computer and analyzed or saved consequently.

No description available.

Compared to other instruments for chemical analyses, electrochemical analyzers are relatively simple, inexpensive, easy to miniaturize and require little-to-no maintenance. However, like all commercially available instruments, commercial electrochemical analyzers like potentiostats primarily operate as black boxes with manufacturers providing little or no information about internal circuitry and programming. This practice can limit a researcher’s ability to develop new techniques or adapt an instrument for applications outside its typical use. In contrast, creators of open-source instruments release all the necessary information for reproduction of the hardware and software – minimizing such barriers to innovation in chemical analyses. Here, we report a low-cost, compact potentiostat based on an open-source Arduino microcontroller capable of performing electrochemical analyses such as cyclic and linear sweep voltammetry with an operating range of ± 208 𝜇A and ± 2.5 V. Performance of the potentiostat is investigated with low-cost pencil graphite electrodes and compared to a commercial potentiostat.