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Robert W. Birkmire - One of the best experts on this subject based on the ideXlab platform.
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Controlling Growth Chemistry and Morphology of Single-Bath Electrodeposited Cu ( In , Ga ) Se2 Thin Films for Photovoltaic Application
Journal of The Electrochemical Society, 2006Co-Authors: M. Estela Calixto, Kevin D. Dobson, Brian E. Mccandless, Robert W. BirkmireAbstract:Single-Bath electrodeposition of polycrystalline Cu(In,Ga)Se 2 thin films for photovoltaic applications is described. Cu(In,Ga)Se 2 was deposited onto Mo electrodes from low concentration aqueous Baths containing CuCl 2 , InCl 3 , GaCl 3 , and H 2 SeO 3 . Buffering the solutions to pH ∼ 2.5 stabilized Bath Chemistry and improved Cu(In,Ga)Se 2 film composition. Bath concentrations were shown to affect composition of deposited films, with a Bath [Se 4+ ]/[Cu 2+ ] ratio of 1.75 required to maintain suitable deposited Se and Cu levels, while [In 3+ ] could be adjusted to control deposited In and Ga. Deposited films initially exhibited significant cracking, which was prevented by lowering the [Se 4+ ] in the Bath, and contained Cu 2-x Se as secondary phases, resembling cauliflower florets, embedded in the film surfaces. The formation of these secondary phases was overcome by pretreating the Mo electrodes with a short 1 min deposition from the Cu(In,Ga)Se 2 Bath. This, coupled with a multipotential deposition regime, led to growth of smooth, compact, crack-free films of near stoichiometric values. Mechanisms of film growth and morphology control are discussed. All as-deposited films exhibit low crystallinity, and for device processing require recrystallization by annealing in an H 2 Se atmosphere. Promising preliminary results of electrodeposited Cu(In,Ga)Se 2 devices are presented.
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Single Bath electrodeposition of CuInSe/sub 2/ and Cu(In,Ga)Se/sub 2/ for thin film photovoltaic cells
Conference Record of the Thirty-first IEEE Photovoltaic Specialists Conference 2005., 1Co-Authors: M.e. Calixto, Kevin D. Dobson, Brian E. Mccandless, Robert W. BirkmireAbstract:In this paper, an electrodeposition (ED) process for growth of CuInSe/sub 2/ and Cu(In,Ga)Se/sub 2/ films from single Baths is presented. The use of buffered Baths and careful selection of Bath concentrations allows good control of the composition of the deposited films. Prior to cell processing, CuInSe/sub 2/ and Cu(In,Ga)Se/sub 2/ films require recrystallization by annealing in H/sub 2/Se/Ar. Promising results have been obtained for ED CuInSe/sub 2/- and ED Cu(In,Ga)Se/sub 2/-based devices. Optimization of the selenization treatment and a better understanding of the Bath Chemistry and film growth mechanism are expected to lead to significant improvements in cell performance.
Jean-françois Bilodeau - One of the best experts on this subject based on the ideXlab platform.
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Chemical Degradation of the Cathodic Electrical Contact Between Carbon and Cast Iron in Aluminum Production Cells
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2017Co-Authors: Martin Brassard, Martin Désilets, Gervais Soucy, Jean-françois Bilodeau, Martin FortéAbstract:The cathodic carbon to cast iron electrical contact degradation is one of the factors to consider in the cathode voltage drop (CVD) increase over the lifetime of aluminum production cells. Lab-scale experiments were carried out to study the cast iron to carbon interface chemical degradation and the impact of important cell parameters like temperature and Bath Chemistry. Laboratory degradation results were compared with industrial samples. A thermoelectric Ansys numerical model was then used to predict the effect of cast iron surface degradation over CVD. Results show that the aluminum formation on the cast iron surface and its subsequent diffusion creates an immiscible mixture of Fe-Al metal alloy and electrolytic Bath. Disparities were also observed between industrial samples taken from two different technologies, suggesting that the degradation can be slowed down. Thermoelectric calculations finally revealed that the impact of the contact resistance augmentation is by far greater than the cast iron degradation.
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study of the structure and thermophysical properties of the side ledge in hall heroult cells operating with modified Bath composition
Light Metals, 2015Co-Authors: Sandor Poncsak, Laszlo I Kiss, Alexandre Belley, Sebastien Guerard, Jean-françois BilodeauAbstract:Recently, there are efforts to change Bath Chemistry used for aluminium electrolysis, in order to decrease operation temperature, cell voltage, etc. Such modifications have a significant impact on the whole Hall-Heroult process, including the composition, the structure, and the thermal properties of the protecting side ledge. Consequently, the heat balance of the cell can be shifted and thus the optimal parameters of the cell operation can be modified. This paper presents some observations and a few results obtained with side ledge of a semi-industrial cell, operating with modified Bath composition. Results show that the main components of the continuous phase in the side ledge remain the cryolithe mixed with some chiolite. However, the apparition of new compounds increases the inhomogeneity, resulting in a slight decrease of the thermal conductivity of side ledge.
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Light Metals 2015 - Study of the Structure and Thermophysical Properties of the Side Ledge in Hall‐Héroult Cells Operating with Modified Bath Composition
Light Metals 2015, 2015Co-Authors: Sandor Poncsak, Laszlo I Kiss, Alexandre Belley, Sebastien Guerard, Jean-françois BilodeauAbstract:Recently, there are efforts to change Bath Chemistry used for aluminium electrolysis, in order to decrease operation temperature, cell voltage, etc. Such modifications have a significant impact on the whole Hall-Heroult process, including the composition, the structure, and the thermal properties of the protecting side ledge. Consequently, the heat balance of the cell can be shifted and thus the optimal parameters of the cell operation can be modified. This paper presents some observations and a few results obtained with side ledge of a semi-industrial cell, operating with modified Bath composition. Results show that the main components of the continuous phase in the side ledge remain the cryolithe mixed with some chiolite. However, the apparition of new compounds increases the inhomogeneity, resulting in a slight decrease of the thermal conductivity of side ledge.
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structural characterisation and thermophysical properties of the side ledge in hall heroult cells
Light Metals, 2014Co-Authors: Sandor Poncsak, Laszlo I Kiss, Sebastien Guerard, Remi Stpierre, Jean-françois BilodeauAbstract:In the modern Hall-Heroult cells, a frozen Bath layer — the side ledge — protects the sidewalls from the very corrosive liquid Bath. This frozen Bath layer has a significant impact on the heat balance of the cells as well as on the Bath Chemistry. For this reason, the geometry, the structure, the distribution of the chemical composition and certain physical properties of the side ledge must be studied. Those characteristics are important to the development of a mathematical model for the Hall-Heroult cells. Despite of all the research efforts invested, only a few results are available in the published literature. This paper presents a few results and observations, obtained by the analysis of side ledge samples, extracted from post-mortem cells. The results show a very inhomogeneous structure and a strong dependence of the thermophysical properties on material structure and temperature.
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Light Metals 2014 - Structural Characterisation and Thermophysical Properties of the Side Ledge in Hall-Héroult Cells
Light Metals 2014, 2014Co-Authors: Sandor Poncsak, Laszlo I Kiss, Sebastien Guerard, Rémi St-pierre, Jean-françois BilodeauAbstract:In the modern Hall-Heroult cells, a frozen Bath layer — the side ledge — protects the sidewalls from the very corrosive liquid Bath. This frozen Bath layer has a significant impact on the heat balance of the cells as well as on the Bath Chemistry. For this reason, the geometry, the structure, the distribution of the chemical composition and certain physical properties of the side ledge must be studied. Those characteristics are important to the development of a mathematical model for the Hall-Heroult cells. Despite of all the research efforts invested, only a few results are available in the published literature. This paper presents a few results and observations, obtained by the analysis of side ledge samples, extracted from post-mortem cells. The results show a very inhomogeneous structure and a strong dependence of the thermophysical properties on material structure and temperature.
Barry J Welch - One of the best experts on this subject based on the ideXlab platform.
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Essential Readings in Light Metals: Aluminum Reduction Technology, Volume 2 - Current Efficiency Studies in a Laboratory Aluminium Cell Using the Oxygen Balance Method
Essential Readings in Light Metals, 2016Co-Authors: Mark Dorreen, Margaret Hyland, Barry J WelchAbstract:There have been many studies investigating the effects of various parameters on the current efficiency in aluminium smelting cells. One of the most important and most widely debated of these parameters is alumina concentration, because of its implications in feed strategies and cell management. This paper presents the results from a study investigating the effects of alumina concentration, Bath Chemistry, current density and anode-cathode spacing on current efficiency. Gas emissions from a laboratory scale cell were measured by on-line mass spectrometry, current efficiency was determined by an oxygen balance method.
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reduction of hf emissions from the trimet aluminum smelter optimizing dry scrubber operations and its impact on process operations
Essential Readings in Light Metals: Aluminum Reduction Technology Volume 2, 2013Co-Authors: Martin Iffert, Markus Kuenkel, Maria Skyllaskazacos, Barry J WelchAbstract:Aluminum smelters worldwide are challenged by increasing ecological and economical pressure. Higher line amperages gain production output but increase the HF load on dry scrubbers. Another important factor today is the tight alumina market, hence it is necessary to accommodate dry scrubber and potline operations to different alumina sources and qualities regarding their HF generation and scrubbing efficiency as well as its impact on Bath Chemistry. The TRIMET smelter optimized dry scrubber operations by the use of a laser based HF measuring system in each of the 20 filter modules. Based on the HF level in the outlet of each filter the alumina flow to each filter is pulse-duration modulated, thus tightly control the HF emission level in the outlet gas. This paper describes the application of the new measuring and control principle and its impact on HF scrubbing efficiency and Bath Chemistry.
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Essential Readings in Light Metals: Aluminum Reduction Technology, Volume 2 - Reduction of HF Emissions from the TRIMET Aluminum Smelter (Optimizing Dry Scrubber Operations and Its Impact on Process Operations)
Essential Readings in Light Metals, 2013Co-Authors: Martin Iffert, Markus Kuenkel, Maria Skyllas-kazacos, Barry J WelchAbstract:Aluminum smelters worldwide are challenged by increasing ecological and economical pressure. Higher line amperages gain production output but increase the HF load on dry scrubbers. Another important factor today is the tight alumina market, hence it is necessary to accommodate dry scrubber and potline operations to different alumina sources and qualities regarding their HF generation and scrubbing efficiency as well as its impact on Bath Chemistry. The TRIMET smelter optimized dry scrubber operations by the use of a laser based HF measuring system in each of the 20 filter modules. Based on the HF level in the outlet of each filter the alumina flow to each filter is pulse-duration modulated, thus tightly control the HF emission level in the outlet gas. This paper describes the application of the new measuring and control principle and its impact on HF scrubbing efficiency and Bath Chemistry.
Guido Grundmeier - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and characterisation of surface gradient thin conversion films on zinc coated steel
Electrochimica Acta, 2006Co-Authors: C. Stromberg, Peter Thissen, I. Klueppel, Nicole Fink, Guido GrundmeierAbstract:Abstract Surface gradient layers on hot-dip galvanised steel were synthesised in order to determine the barrier properties and corrosion resistance of thin amorphous conversion coatings as a function of layer thickness and processing time. For this purpose, a dip coating procedure was established that yields well-defined gradient layers. As a model system for conversion film formation on zinc coated steel, a zirconium based Bath Chemistry was used. The synthesised zirconium oxyhydroxide gradient films were characterised by localised electrochemical techniques, such as Scanning Kelvin Probe (SKP) and electrochemical impedance spectroscopy using an electrochemical capillary cell. Microscopic infrared reflection absorption spectroscopy (μ-FT-IRRAS) measurements and small-spot X-ray photo electron spectroscopy (XPS) were used as complementary surface analytical techniques. The applied analysing techniques provide a spatial resolution of 100–1600 μm. Thereby, a complete variation of thin film properties, such as thickness, barrier properties, corrosion resistance and chemical composition can be measured as function of the time of film growth on a sample with a length of a few centimetres. This approach allows a precise and accurate determination of structure-to-property relationships of thin conversion films. Moreover, it could be shown that a surface gradient film analysis significantly rationalises experimental time and increases the reliability of the experimental results.
Roberto Celio Limao De Oliveira - One of the best experts on this subject based on the ideXlab platform.
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simulations on the Bath Chemistry variables using neural networks
Light Metals, 2016Co-Authors: Patrizia R S Chermont, Fabio M Soares, Roberto Celio Limao De OliveiraAbstract:In this work we present a single layer neural network based model for Bath Chemistry variables in the aluminum smelting process. This model is designed to be simulated with real data as if it worked online in parallel with the process. The model is built using a very fast machine learning algorithm, the Extreme Learning Machines, which provides excellent results in regression problems in a very short time. Also we applied statistical analysis for data collection, preprocessing and filtering and for validation we performed several simulations to attest the neural model’s capability to respond to new data. A comparison of this model against linear and traditional nonlinear structures is performed to show how single layer neural networks can be applied on the Bath Chemistry modeling.
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Light Metals 2016 - Simulations on the Bath Chemistry Variables Using Neural Networks
Light Metals 2016, 2016Co-Authors: Patrizia R S Chermont, Fabio M Soares, Roberto Celio Limao De OliveiraAbstract:In this work we present a single layer neural network based model for Bath Chemistry variables in the aluminum smelting process. This model is designed to be simulated with real data as if it worked online in parallel with the process. The model is built using a very fast machine learning algorithm, the Extreme Learning Machines, which provides excellent results in regression problems in a very short time. Also we applied statistical analysis for data collection, preprocessing and filtering and for validation we performed several simulations to attest the neural model’s capability to respond to new data. A comparison of this model against linear and traditional nonlinear structures is performed to show how single layer neural networks can be applied on the Bath Chemistry modeling.
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a mimo modeling strategy for Bath Chemistry
Light Metals, 2013Co-Authors: Fabio M Soares, Roberto Celio Limao De OliveiraAbstract:The Bath Chemistry is very complex for analytical modeling due to its sensitivity to disturbances from other processes. The control of the electrolyte also represents a great challenge, provided that any change in the heat and mass balance may affect current efficiency and pot life. In order to test a good control strategy, a process model is very helpful. The model allows process experts to design and test process control strategies without compromising reduction cells. In addition a model allows simulations on the process for a long time. In this work we developed a neural-based strategy to model Bath Chemistry variables in a Multiple Input Multiple Output (MIMO) approach using a data-driven design. The achieved results are very acceptable for the process engineering staff of the industry where this work was performed.
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Light Metals 2013 - A MIMO Modeling Strategy for Bath Chemistry
Light Metals 2013, 2013Co-Authors: Fabio M Soares, Roberto Celio Limao De OliveiraAbstract:The Bath Chemistry is very complex for analytical modeling due to its sensitivity to disturbances from other processes. The control of the electrolyte also represents a great challenge, provided that any change in the heat and mass balance may affect current efficiency and pot life. In order to test a good control strategy, a process model is very helpful. The model allows process experts to design and test process control strategies without compromising reduction cells. In addition a model allows simulations on the process for a long time. In this work we developed a neural-based strategy to model Bath Chemistry variables in a Multiple Input Multiple Output (MIMO) approach using a data-driven design. The achieved results are very acceptable for the process engineering staff of the industry where this work was performed.
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IDEAL - Soft sensor for fluoridated alumina inference in gas treatment centers
Intelligent Data Engineering and Automated Learning - IDEAL 2012, 2012Co-Authors: Alan M. F. De Souza, Fabio M Soares, Carolina M. Affonso, Roberto Celio Limao De OliveiraAbstract:The Gas Treatment Center performs a key role in the aluminum smelting process, since it strongly influences the chemical and thermal stability of the electrolytic Bath through fluoridated alumina. Therefore this variable should be considered to keep the Bath Chemistry under control. However, the fluorine concentration measurement in fluoridated alumina is very time-consuming and that information becomes available only after a while. By using Artificial Neural Network we developed a Soft Sensor capable to estimate the fluorine concentration in fluoridated alumina, and to provide that information to plant engineers in a timely manner. This paper discusses the methodology used and the results of an implemented Soft Sensor using Neural Networks on fluorine estimation in fluoridated alumina from a Gas Treatment Center in an important Brazilian Aluminum Smelter.