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The oxygen exchange and diffusion kinetics of SOFC electrodes studied by Time-of-Flight SIMS
No full textProtection of public interest in civil procedure.
No full textProtection of Public Interest in Civil Procedure Protection of public interest is the procedure which safeguards the most significant public value. Even though there might be an impression that this doctrine has been widely discussed and as a result it may lack scientific sensitivity, the author does not agree with that. The significance and characteristics of public interest are challenges themselves and as a consequence, they determine the importance of continuous investigation in the field of public interest. Legal regulation changes, inconsistency of judicial practice and lack of systematic analysis of specific doctrines are of great importance for this investigation and reveal a wide range of research problems. However, the most important aspect of this research is that the author does not limit himself only to the field of the usual public interest research (for example, the doctrine of public interest or the concept of public interest). On the contrary, the author chooses new directions meanwhile paying attention to the important issues that previously have not been analysed. As a result, the problem of justifying the efficiency, the prosecutor's supervisory role and the legal basis of the state and municipalities are the areas that demonstrate the uniqueness of this very research. On the other hand, the researcher is not only a passive observer. After analysing scientific positions, the author looks for new arguments in order to deny or support the theories and discuss and justify his own position. Finally, the researcher comes to the conclusions that allow one to decide on: 1) the prevailing concept of the shared values in Lithuania and the possible duality of the concepts; 2) the criterion on the justification of the public interest; 3) the approval of prosecutor´s supervisory role; 4) the duties of the state and municipalities; 5) the groundlessness of the court, as an entity, protecting the public interest; and other aspects important for the protection of public interest in civil proceedings
Oxygen exchange and diffusion kinetics in grains and grain boundaries of La0.8Sr0.2MnO3 thin films measured by Secondary Ion Mass Spectrometry
No full textIonentransport an hetero- und homophasigen Grenzflächen von Yttrium-dotierten Zirconiumdioxid (YSZ) Dünnschichten
Get PDFZahlreiche Forschungsaktivitäten auf dem Gebiet der Festkörperionik (solid state ionics) befassten sich mit der ionischen Leitfähigkeit in Nanomaterialien, einschließlich Dünnschichten. Starke Abweichungen von makroskopischen Eigenschaften im Volumen der Materialen wurden gefunden sind aber oft nur teilweise verstanden. Viele Studien wurden an Yttrium stabilisiertem Zirconiumdioxid (YSZ) durchgeführt, aber nur in Volumenproben von YSZ können Korn- und Korngrenzleitfähigkeiten leicht separiert werden. Auch für ein besseres Verständnis der Leitfähigkeitsmechanismen in dünnen Filmen wird die Trennung von Korn- und Korngrenzleitfähigkeiten benötigt, die jedoch bisher durch die Streukapazität des Substrats verhindert wurde. In dieser Arbeit wird ein Verfahren vorgeschlagen, welches die Korn- und Korngrenzleitfähigkeit in nanokristallinen YSZ Dünnschichten durch eine optimierte Elektrodengeometrie trennt. Als weitere Eigenschaft wird in dieser Arbeit die Anisotropie der Leitfähigkeit von YSZ Dünnschichten diskutiert. Dabei wird die Leitfähigkeit von dünnen Schichten senkrecht und entlang der Dünnschichtebene (in-plane) gemessen. Beide Arten von Messungen sind wichtig, zeigen mögliche Anisotropien der Leitfähigkeit und können gewöhnlich nur separat gemessen werden. Für die senkrechten Messungen werden Substrate mit einem geringen spezifischen Widerstand als YSZ benötigt, während für die in-plane Messungen Substrate mit höherem Widerstand verwendet werden. Darüber hinaus können senkrechte Messungen schwierig auf sehr dünnen Schichten durchgeführt werden, da dies oft zu Kurzschlüssen aufgrund kleiner Löcher in der Schicht führt. Hier wird ein neues Verfahren vorgestellt, um diese Probleme durch Leitfähigkeitsmessungen von dünnen YSZ Schichten auf Silizium zu überwinden. Siliziumsubstrate haben in der Regel eine native Siliziumdioxidschicht, die für Leitfähigkeitsmessungen ausgenutzt werden kann. Für senkrechte Leitfähigkeitsmessungen wurden Impedanz-Spektren mit kreisförmigen Mikroelektroden auf der YSZ-Schicht und einer Gegenelektrode an der Unterseite einer Probe bestimmt. Die Siliziumoxidschicht wirkt dabei als Sperrkapazität für niedrige Frequenzen und vermeidet Kurzschlüsse, während sie für die hohen Frequenzen stromdurchlässig bleibt. Es wird belegt, dass unterschiedliche Elektrodendurchmesser und Schichtdicken die YSZ Impedanzspektren beeinflussen. Leitfähigkeiten und Kapazitäten von Siliziumoxid und YSZ Dünnschichten (bis 20 nm Schichtdicke) konnten im Temperaturbereich von 200 °C - 400 °C erfolgreich untersucht werden. Die Schichtdicke zeigt einen geringen Einfluß auf die senkrechte Leitfähigkeit der YSZ Schichten, welche nur geringfügig niedriger ist als die Leitfähigkeit einer polykristallinen YSZ-Probe. Experimentelle Ergebnisse von senkrechten Leitfähigkeitsmessungen werden durch Finite-Elemente-Simulationen (COMSOL) unterstützt. Die in-plane Messungen wurden mit parallelen Streifenelektroden auf YSZ durchgeführt. Der hohe Gleichstromwiderstand der Siliziumoxid-Zwischenschicht bewirkt stark frequenzabhängige Stromverteilungen und erlaubt deswegen die Bestimmung der in-plane und senkrechten YSZ Leitfähigkeiten aus einen einzigen Impedanzspektrum. Der hochfrequente Teil eines Impedanzspektrum entspricht Experimenten mit senkrechtem Stromfluss, während der niederfrequente Teil die Leitfähigkeitsergebnisse einer in-plane Probengeometrie zeigt. Die Gültigkeit dieser Analyse wurde durch Variieren der Elektrodengeometrie bezüglich Breite und Abstand der Elektroden bewiesen. Es wird auch gezeigt, dass die gemessene Leitfähigkeit in der Ebene (in-plane Geometrie) etwa eine Größenordnung niedriger ist als die senkrecht gemessene Leitfähigkeit. Diese Anisotropie wird auf die Sperrwirkung der Korngrenzen in den säulenförmig strukturierten dünnen YSZ Schichten zurückgeführt. Die experimentellen Ergebnisse werden durch zusätzliche Finite-Elemente-Simulationen (COMSOL) unterstützt. Schließlich wurde das isolierende Oxid auf Si variiert (ZrO2, Al2O3 und Y2O3 statt SiO2) und der Einfluss auf die Leitfähigkeiten (senkrecht un in-plane) analysiert.Numerous recent research activities in solid state ionics dealt with the ionic conductivity in nanomaterials, including thin films. Strong deviations from bulk properties are often found but only partly understood. Many studies were performed on yttria stabilized zirconia (YSZ), but only on YSZ bulk materials grain and grain boundary conductivity can easily be separated. For a better understanding of the conductivity mechanisms in thin films, separation of grain and grain boundary conductivities is needed, which becomes highly sophisticated and limited by the stray capacitance of the substrate. In this thesis a method is introduced which allows grain and grain boundary conductivity separation in nanocrystalline YSZ thin films by an optimized electrode geometry. The other important property discussed in the thesis is the anisotropy of the conductivity of YSZ thin films. The conductivity of thin layers can be measured perpendicular and lateral to the thin film plane. Both types of measurements are important and reveal any potential anisotropy of the conductivity. Usually YSZ in- and across-plane conductivities are measured separately, because for in-plane measurements substrates with a higher resistivity than YSZ are needed while for across-plane measurements it is vice versa. Moreover, across-plane measurements are very difficult to be done on very thin layers, since this usually leads to short-circuits due to pin holes in the layer. Here a novel method is presented to overcome these problems by deposition of YSZ thin films on silicon. Silicon substrates usually have a native silica layer, which can be made use of in conductivity measurements. For across-plane conductivity measurements impedance spectra were obtained with circular microelectrodes on top of the YSZ layer and a counter electrode at the bottom side of the sample. The silica layer acts as a blocking capacitance for low frequencies, which helps to avoid short circuit, while for the high frequencies it is transmittable. The contribution of YSZ is identified by varying diameter of the electrodes and layer thickness. Silica and YSZ conductivities and capacitances can be successfully separated in the temperature range from 200 °C - 400 °C for YSZ films as thin as 20 nm. The across-plane conductivity of the YSZ films does not significantly depend on the layer thickness and is only slightly lower than the bulk conductivity of a YSZ polycrystalline sample. Experimental results of across-plane conductivity measurements are supported by finite element simulations (COMSOL). The in-plane measurements on silicon substrates are done with parallel stripe electrodes on YSZ. The high dc resistance of the silica interlayer causes strongly frequency dependent current lines and allows determination of the in- and across-plane conductivity of the YSZ film from a single impedance spectrum. The high frequency part of the impedance spectrum corresponds to an across-plane measurement geometry while the low frequency part is governed by in-plane current flow. Validity of this analysis is proven by varying electrode width and distance between the electrodes. It is shown that the measured in-plane conductivity is about one order of magnitude lower than the across-plane bulk conductivity. This anisotropy is attributed to the blocking effect of grain boundaries in the columnar structured YSZ films. Again the experimental results are well supported by finite element simulations (COMSOL). This insulating oxide on silicon was varied (ZrO2, Al2O3 and Y2O3 instead of SiO2) and its effect on in- and across-plane conductivity was analysed
In- and across-plane conductivities of YSZ layers obtained from a single impedance measurement
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Elektrochemische Charakterisierung von (La,Sr,Ca)2Co2-xMnxO6-δ als Kathodenmaterial in Festoxidbrennstoffzellen
Get PDFIntermediate temperature fuel cells, with a working temperature between 500 °C and 700 °C, suffer from the slow reduction kinetics of oxygen at the cathode side which is responsible for most of the resistive losses. The aim of this work was the investigation of the electrical properties, oxygen exchange kinetics and diffusion processes of 18O tracer ions in advanced cathode materials, such as perovskites with the generalized structure (La,Ca,Sr)2Co2-xMnxO6-¿. First, targets materials were synthesized by a Pechini-type method. Subsequently thin films of different compositions were grown by pulsed laser deposition (PLD) under various p(O2) on three different single crystal substrates, since the background pressure in the PLD chamber and the used substrate have a massive impact on the thin film structure and properties. For ionic conductivity determination, some of the samples were microstcructured by UV-lithography and impedance spectroscopy was performed. The electrical properties of bulk and thin film samples were investigated by van der Pauw method. Keeping the Co/Mn ratio 1:1, a higher conductivity for Ca and Sr doped samples is observed due to p-type doping. Moreover, by changing the relative amount of Co without A-site doping conductivity can also be enhanced. All produced and investigated bulk samples possess a lower electrical conductivity and higher activation energy than La0.8Sr0.2MnO3 (LSM). For applicable cathode materials, a good oxygen diffusion is crucial. Hence, La2CoMnO6 thin film were investigated by performing 18O exchange experiments and ToF-SIMS depth profiling. With these techniques, the diffusion coefficient D* and the surface exchange coefficient k* were determined. In La2CoMnO6 samples, grain boundary diffusion plays a vital role. Diffusion coefficients of the grain boundaries are one to two orders of magnitude higher than the bulk diffusion coefficients and stay constant when p(O2) in the PLD-chamber during thin film growth is increased. Additionally, a high p(O2) leads to an additional diffusion process and is most likely related to the dislocation concentration. For the determination of the ionic area specific resistance of La2CoMnO6 impedance spectroscopy was carried out. Activation energies below 550 °C indicate a triple phase boundary path of oxygen reduction. If the samples were heated for the first time above 500 °C irreversible changes took place and the activation energies and resistivity rose tremendously in further measurements
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