Browsing by Author "Machkova M."
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Item Assessment of Nd2-xSrxNIO4-d as a cathodic material for solid oxide fuel cell applications(2013-05-21) Simeonov S.; Kozhukharov S.; Grenier J.; Machkova M.; Kozhukharov V.The features and performance of each device and equipment is directly related to its composing materials. The efficiency and durability of the Solid Oxide Fuel Cells (SOFC) also depend on their composing elements. Other important factors for the SOFC behavior are the working conditions (compositions, and humidity of the fuel and oxidant gaseous mixtures, temperature, pressure, etc.). These facts predetermine the necessity for detailed investigation of the behavior of each composing layer of SOFC. For this reason, the electrical characteristics of Nd2-xSrxNiO4-d as SOFC cathodic material were evaluated by high temperature electrochemical methods, durability tests, and posterior XRD and SEM characterization. As a result, the optimal composition and working conditions for the investigated material in assembled SOFC were determined. The obtained material reveals excellent durability and compatibility with the rest SOFC components.Item Ceramic materials for SOFCs: Current status(2002-01-01) Kozhukharov V.; Brashkova N.; Ivanova M.; Carda J.; Machkova M.It is well known that the main parts of Solid Oxide Fuel Cells (SOFCs) are build from ceramic materials. Namely the ceramic materials and composites, used for SOFCs manufacturing, are objects of the overview in the present work. The analysis carried out covers the last current publications in the field discussed. Special attention and examination in details have been done on patents state-of-the-art. After a background and short classification of the ceramic SOFCs materials the attention is focused on cathode, electrolyte, anode, interconnection and sealing materials. Their requirements, structure, thermal stability, composition control and behavior, processing and performance are the object of overview. A correlation has been made between the phase diagrams oxygen incorporation and transport, and SOFC advantages, generally for materials of lanthanum- base perovskite family. In order to analyze the innovative investigations regarding the patent branch of the SOFCs development and application, an object of review was patents from Japan, USA, Germany and European Union. Some examples of the inventions with accent on the ceramic materials are shown. In addition the tendency regarding R&D activities of SOFCs development materials from the leading companies in the world is analyzed. On the base of the most important technological and economical parameters of cell cathode/electrolyte/anode materials an attempt for evaluation and correlation has been made and innovative conceptions are shown.Item Ceramic materials for SOFCs: Current status(2002-01-01) Kozhukharov V.; Brashkova N.; Ivanova M.; Carda J.; Machkova M.It is well known that the main parts of Solid Oxide Fuel Cells (SOFCs) are build from ceramic materials. Namely the ceramic materials and composites, used for SOFCs manufacturing, are objects of the overview in the present work. The analysis carried out covers the last current publications in the field discussed. Special attention and examination in details have been done on patents state-of-the-art. After a background and short classification of the ceramic SOFCs materials the attention is focused on cathode, electrolyte, anode, interconnection and sealing materials. Their requirements, structure, thermal stability, composition control and behavior, processing and performance are the object of overview. A correlation has been made between the phase diagrams oxygen incorporation and transport, and SOFC advantages, generally for materials of lanthanum- base perovskite family. In order to analyze the innovative investigations regarding the patent branch of the SOFCs development and application, an object of review was patents from Japan, USA, Germany and European Union. Some examples of the inventions with accent on the ceramic materials are shown. In addition the tendency regarding R&D activities of SOFCs development materials from the leading companies in the world is analyzed. On the base of the most important technological and economical parameters of cell cathode/electrolyte/anode materials an attempt for evaluation and correlation has been made and innovative conceptions are shown.Item Ceramic materials for SOFCs: Current status(2002-01-01) Kozhukharov V.; Brashkova N.; Ivanova M.; Carda J.; Machkova M.It is well known that the main parts of Solid Oxide Fuel Cells (SOFCs) are build from ceramic materials. Namely the ceramic materials and composites, used for SOFCs manufacturing, are objects of the overview in the present work. The analysis carried out covers the last current publications in the field discussed. Special attention and examination in details have been done on patents state-of-the-art. After a background and short classification of the ceramic SOFCs materials the attention is focused on cathode, electrolyte, anode, interconnection and sealing materials. Their requirements, structure, thermal stability, composition control and behavior, processing and performance are the object of overview. A correlation has been made between the phase diagrams oxygen incorporation and transport, and SOFC advantages, generally for materials of lanthanum- base perovskite family. In order to analyze the innovative investigations regarding the patent branch of the SOFCs development and application, an object of review was patents from Japan, USA, Germany and European Union. Some examples of the inventions with accent on the ceramic materials are shown. In addition the tendency regarding R&D activities of SOFCs development materials from the leading companies in the world is analyzed. On the base of the most important technological and economical parameters of cell cathode/electrolyte/anode materials an attempt for evaluation and correlation has been made and innovative conceptions are shown.Item Elucidation of the contribution of modified titania films over the performance of thin film humidity sensors(2013-05-21) Kozhukharov S.; Nenova Z.; Nenov T.; Ivanov S.; Machkova M.The present research focuses on comparative measurements of the influence of complex additives on the sensitivity of humidity sensors, prepared by the sol-gel metrhod. Three different dopants were added to the primary mixture in order to improve the properties of the films, expressed in water uptake capability, as follows: Bismuth acetate (CH3COO)3Bi, Vanadium-2,4 pentadionate (C15H21O6V), and Sodium tert-butoxide (CH3)3CONa. The properties of the obtained sensors were evaluated by determination of their electrical resistances in a chamber with controlled humidity. As a result, it was experimentally established that the most significant positive effect over both the increase of sensitivity and the measurement range enlargement come from V(III)-2,4 pentadionate with Sodium tert-butoxide.Item Influence of ce(iii)/ce(iv)-supplements on the characteristics of humidity sensors with tio2 films prepared via a sol-gel method(2013-03-01) Kozhukharov S.; Nenova Z.; Nenov T.; Machkova M.; Kozhukharov V.Humidity sensors have been prepared via a sol-gel method to deposit TiO2 films with additions of Ce-compounds on alumina substrates, with interdigitated silver palladium electrodes. Observations by scanning electron microscopy (SEM) were performed in order to determine the surface morphology of the respective layers. Structural and compositional characterization was done by X-ray diffraction analysis (XRD), and energy dispersive X-ray spectroscopy (EDX) for investigation of the relation between the film structures and the parameters of the respective sensors. The influence of Ce-compounds on the electrical characteristics of the samples as humidity sensing elements has been evaluated by an impedance analyzer.Item Nanomaterials and nanotechnology: European initiatives, status and strategy(review)(2013-05-21) Kozhukharov V.; Machkova M.The aim of the present work is to present a short overview regarding European initiatives, state-of-the-art and RTD strategy in the field of nanomaterials and nanotechnologies. The idea is to mark the national action plans of the leading European countries, to analyse and to discuss their activities, in order to synchronize to the EU nano-initiatives, regarding R&D and social aspects in the field of nanoscience and technoloiesy. Object of discussion are the most important industrial countries in the European Union. Since the field is too broad, some countries are selected and the overview is done by dividing ofEuropean Union relatively in two parts: West Europe (e.g. Germany, UK, France, Italy, Spain, Scandinavian countries, Switzerland, etc.) and East Europe (e.g. Poland, Bulgaria, Russia). Adequate conclusions are extracted.Item Reproducibility of the corrosion parameters for AA2024-T3 aluminium alloy in chloride solution after different preliminary treatment procedures(2015-01-01) Matter E.A.; Kozhukharov S.; Machkova M.; Kozhukharov V.The reproducibility of the superficial morphology and corrosion parameters of AA2024 alloy in 0.6 M NaCl solution under different preliminary treatment procedures have been studied. It was achieved by applying optical metallographic microscopy (OMM), atomic force microscopy (AFM) and electrochemical methods as linear voltammetry (LVA) and electrochemical impedance spectroscopy (EIS). Four different preliminary treatment procedures are investigated. Statistic methods are used for the reproducibility evaluation of each measured parameter. The results revealed that the approach of etching with a slightly alkaline solution after mechanical grinding increases the reproducibility, and the best reproducibility was achieved in the approach of mechanical grinding.Item Surface analysis of doped lanthanide cobalt perovskites by X-ray photoelectron spectroscopy(1996-10-01) Kozhukharov V.; Machkova M.; Ivanov P.; Bouwmeester H.J.M.; Van Doorn R.