The transport in oxides is studied by the use of gas phase analysis (GPA). An experimental method to identify transported species of gases and their contribution to the overall transport of gases in oxides and an experimental method to evaluate the parameters diffusivity, concentration, permeability of gases in oxides and effective pore size in oxides are developed, respectively. Pt has two effects on the thermal oxidation of metals. One is to enhance the oxidation of metals which takes place at the oxide-metal interface by promoting a high concentration gradient of dissociated oxygen across the oxide layer. The other effect is to suppress the oxidation of metals by decreasing the contact area between metal and oxygen. The overall effect of Pt on the oxidation of metals depends on the mechanism of oxide growth in the absence of Pt. It is suggested that an appropriate amount of Pt coating induces a balanced oxide growth resulting from stoichimetrical inward oxygen flux to outward metal flux, which leads to a reduced oxidation rate. The diffusion of diatomic gases in oxides such as vitreous silica and yttria stabilized zirconia (YSZ) takes place in both molecular and dissociated (atomic or/and ionic) form. The fraction of transport of molecular species decreases with temperatures, and the fraction of transport of dissociated species increases with temperatures. Measured permeabilities of diatomic gases in vitreous silica are higher than the expected permeabilities of their molecules, which are explained by diffusion of molecules combined with a retardation of dissociated species in reversible traps. The diffusion of hydrogen in vitreous silica is concentration dependent and increases with local concentration. Transport paths are shared among transported species and gases at all temperatures in YSZ. Helium shares transport path with molecular oxygen and nitrogen at low temperatures; whereas helium shares transport path with dissociated oxygen and also dissociated nitrogen at high temperatures. / QC 20100705

No description available.

La fibrilación auricular es una de las arritmias cardíacas más comunes observadas en la práctica clínica. Por lo tanto, es de vital importancia desarrollar nuevas tecnologías destinadas a diagnosticar y acabar con este tipo de arritmia, para mejorar la calidad de vida de los pacientes y reducir los costes de los sistemas nacionales de salud. En los últimos años ha aumentado el uso de las nuevas técnicas de mapeo auricular, basadas en sistemas multi-electrodo para mapear la actividad eléctrica en humanos. Dichas técnicas permiten localizar y ablacionar los impulsores de la fibrilación auricular, como son las fuentes focales o los rotores. Sin embargo, todavía existe incertidumbre sobre su precisión y los procedimientos experimentales para su análisis están limitados debido a su carácter invasivo. Por lo tanto, las simulaciones computacionales son una herramienta muy útil para superar estas limitaciones, al permitir reproducir con fidelidad las observaciones experimentales, dividir el problema bajo estudio en sub-estudios más simples, y realizar investigaciones preliminares imposibles de llevar a cabo en el práctica clínica. Esta tesis doctoral se centra en el análisis de la precisión de los sistemas de mapeo multi-electrodo a través de modelos y simulaciones computacionales. Para ello, desarrollamos modelos realistas multi-escala con el objetivo de simular actividad eléctrica auricular reentrante, en primer lugar en una lámina de tejido auricular, y en segundo lugar en las aurículas completas. Posteriormente, analizamos los efectos de las configuraciones geométricas multi-electrodo en la precisión de la localización de los rotores, mediante el uso de agrupaciones multi-electrodo con distancias inter-electrodo equidistantes, así como a través de catéteres de tipo basket con distancias inter-electrodo no equidistantes. Después de calcular los electrogramas unipolares intracavitarios, realizamos mapas de fase, detecciones de singularidad de fase para rastrear los rotores, y mapas de frecuencia dominantes. Finalmente, descubrimos que la precisión de los sistemas de mapeo multi-electrodo depende de su posición dentro de la cavidad auricular, de la distancia entre los electrodos y el tejido, de la distancia inter-electrodo, y de la contribución de las fuentes de campo lejano. Además, como consecuencia de estos factores que pueden afectar a la precisión de los sistemas de mapeo multi-electrodo, observamos la aparición de rotores falsos que podrían contribuir al fracaso de los procesos de ablación de la fibrilación auricular. / Atrial fibrillation is one of the most common cardiac arrhythmias seen in clinical practice. Therefore, it is of vital importance to develop new technologies aimed at diagnosing and terminating this kind of arrhythmia, to improve the quality of life of patients and to reduce costs to national health systems. In the last years, new atrial mapping techniques based on multi-electrode systems are increasingly being used to map the atrial electrical activity in humans and localise and target atrial fibrillation drivers in the form of focal sources or rotors. However, significant concerns remain about their accuracy and experimental approaches to analyse them are limited due to their invasive character. Therefore, computer simulations are a helpful tool to overcome these limitations since they can reproduce with fidelity experimental observations, permit to split the problem to treat into more simple substudies, and allow the possibility of performing preliminary investigations impossible to carry out in the clinical practice. This PhD thesis is focused on the analysis for accuracy of the multielectrode mapping systems through computational models and simulations. For this purpose, we developed realistic multiscale models in order to simulate atrial electrical reentrant activity, first in a sheet of atrial tissue and, then, in the whole atria. Then, we analysed the effects of the multi-electrode geometrical configurations on the accuracy of localizing rotors, by using multi-electrode arrays with equidistant inter-electrode distances, as well as multi-electrode basket catheters with non-equidistant inter-electrode distances. After computing the intracavitary unipolar electrograms, we performed phase maps, phase singularity detections to track rotors, and dominant frequency maps. We finally found out that the accuracy of multi-electrode mapping systems depends on their position inside the atrial cavity, the electrode-to-tissue distance, the inter-electrode distance, and the contribution of far field sources. Furthermore, as a consequence of these factors, false rotors might appear and could contribute to failure of atrial fibrillation ablation procedures. / La fibril·lació auricular és una de les arítmies cardíaques més comuns observades en la pràctica clínica. Per tant, és de vital importància desenvolupar noves tecnologies destinades a diagnosticar i acabar amb aquest tipus d'arítmia, per tal de millorar la qualitat de vida dels pacients i reduir els costos dels sistemes nacionals de salut. En els últims anys, ha augmentat l'ús de les noves tècniques de mapeig auricular, basades en sistemes multielèctrode per a mapejar l'activitat elèctrica auricular en humans. Aquestes tècniques permeten localitzar i ablacionar els impulsors de la fibril·lació auricular, com són les fonts focals o els rotors. No obstant això, encara hi ha incertesa sobre la seua precisió i els procediments experimentals per al seu anàlisi estan limitats a causa del seu caràcter invasiu. Per tant, les simulacions computacionals són una eina molt útil per a superar aquestes limitacions, en permetre reproduir amb fidelitat les observacions experimentals, dividir el problema sota estudi en subestudis més simples, i realitzar investigacions preliminars impossibles de dur a terme en el pràctica clínica. Aquesta tesi doctoral es centra en l'anàlisi de la precisió del sistemes de mapeig multielèctrode mitjançant els models i les simulacions computacionals. Per a això, desenvolupàrem models realistes multiescala per tal de simular activitat elèctrica auricular reentrant, en primer lloc en una làmina de teixit auricular, i en segon lloc a les aurícules completes. Posteriorment, analitzàrem els efectes de les configuracions geomètriques multielèctrode en la precisió de la localització dels rotors, mitjançant l'ús d'agrupacions multielèctrode amb distàncies interelèctrode equidistants, així com catèters de tipus basket amb distàncies interelèctrode no equidistants. Després de calcular els electrogrames unipolars intracavitaris, vam realitzar mapes de fase, deteccions de singularitat de fase per a rastrejar els rotors, i mapes de freqüència dominants. Finalment, vam descobrir que la precisió dels sistemes de mapeig multielèctrode depèn de la seua posició dins de la cavitat auricular, de la distància entre els elèctrodes i el teixit, de la distància interelèctrode, i de la contribució de les fonts de camp llunyà. A més, com a conseqüència d'aquests factors, es va observar l'aparició de rotors falsos que podrien contribuir al fracàs de l'ablació de la fibril·lació auricular. / Martínez Mateu, L. (2018). Mapping of the electrical activity of human atria. Multiscale modelling and simulations [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/104604

Concrete, one of the world’s most important building materials is formed when cement is mixed with aggregates and reacts with water. The reaction is called hydration. Production of cement involves conversion of limestone and clay minerals into cement clinker in a kiln at high temperatures. The process requires high amounts of energy and causes substantial carbon emissions due to calcination of limestone and combustion of fuels, and the need for carbon neutral clinker products have never been greater. Heidelberg Materials Cement Sverige AB has multiple ongoing projects to reduce the carbon footprint of their clinker products. In essence, this is made possible by diluting the clinker with supplementary cementitious materials (SCM), electrification of the kiln, and carbon capture and storage (CCS). During tests of such applications in pilot and industrial scales it is necessary to evaluate the cement clinker manufactured for its ability to act as a binder in concrete. Such properties are collectively termed hydraulic reactivity and depend on the rate and extent to which the anhydrous components (alite, belite, aluminate, ferrite) in the cement react with water to form structural strength. The primary hydration products are Calcium-silicate-hydrate (C-S-H) and portlandite (CH). Due to lack of routines for clinker reactivity testing, especially for small batches, new methods and guidelines for reactivity tests has become highly sought after. Therefore, this work has aimed to develop a method for laboratory grinding of clinkers and then to study their hydration reactions by isothermal conductive calorimetry (ICC), Rietveld refinement quantitative x-ray diffraction (XRD) and thermogravimetric analysis (TGA). The goal of the work has been to provide a grinding method for laboratory cement preparation and a protocol for clinker reactivity evaluation. A fundamental requirement has been that the results of the methods must be comparable with Heidelberg Materials’ conventional standard methods. The work was initiated with a literature review on cement clinker manufacture, its hydration kinetics and reactivity tests. Industrial reference clinkers were used to develop the grinding method, and finally, reactivity tests with ICC, XRD and TGA were conducted on multiple clinkers of different origins. The grinding method developed in this work gave a fineness resembling the conventional grinding method but slightly coarser. Consequently, the heats measured in ICC for the clinkers studied were also comparable to previous analyses by conventional methods. This was a direct result of the reactivity being dependent on the specific surface area of the cement particles. Thanks to this, the newly developed grinding method and reactivity test by ICC may be incorporated into Heidelberg Materials standard methods. Hydrates formation and clinker mineral consumption were studied in XRD and TGA. The two techniques were used as cross-validation of one another. In summary, these yielded more in-depth information about the hydration of cements than provided by ICC and gave insights into what minerals and reactions were responsible for each clinker’s reactivity. However, the XRD and TGA results contained significant errors at some times, and further development is necessary before using them as part of a standard routine. This was mainly due to errors tied to sample preparation. Some necessary improvements are better Rietveld refinement, prevention of XRD sample carbonation, and addition of a separate ettringite analysis in TGA. Despite this, the methods show great promise, as highly correlating results were reached between methods when the sources of error were managed. For future work, it is suggested that the protocol is expanded and applied to also evaluate SCM’s. / Betong är ett av världens viktigaste byggmaterial och bildas när cement blandat med aggregat reagerar med vatten. Reaktionen kallas hydratation. Cement i sin tur tillverkas genom omvandling av kalksten och lermineraler till cementklinker vid hög temperatur i en roterugn. Denna process är mycket energikrävande och genererar stora koldioxidutsläpp från råmaterialen och bränslet. Till följd av detta har ett starkt och omedelbart behov av klimatvänliga klinkerprodukter uppstått. Heidelberg Materials Cement Sverige AB arbetar ständigt med att hitta nya lösningar till produktionen för att minska dess klimatavtryck. En viktig del i denna minskning är att späda ut klinkern med alternativa bindemedel (SCM), elektrifiering av bränningsprocessen och uppfångning samt lagring av koldioxid (CCS). Förändringar i den industriella processen förändrar dock klinkern vilket kan påverka cementets förmåga att agera som bindemedel i betong. Dessa egenskaper kallas kollektivt för hydraulisk reaktivitet, och beror på både hastigheten och i vilken utsträckning klinkermineralerna alit, belit, aluminat och ferrit hydratatiseras för att bilda calcium-silikat-hydrat (C-S-H) och portlandit (CH) och på så vis skapa tryckhållfasthet. I och med försök på industriell- och pilotnivå har det blivit önskvärt att kunna utvärdera reaktiviteten hos klinker. Eftersom det idag delvis fattas rutiner för detta, så har detta arbete syftat till att utveckla en metod för laboratoriemalning av klinker i små batcher, samt att studera hydratationen av den malda klinkern med isotermisk konduktions kalorimetri (ICC), kvantitativ röntgendiffraktion med Rietveld metoden (XRD) och termogravimetrisk analys (TGA). Projektets mål har varit att färdigställa en sådan malningsmetod och att förse företaget med ett protokoll för utvärdering av reaktiviteten. Ett grundläggande krav för de utvecklade metoderna är att deras resultat ska vara jämförbara med Heidelberg Materials konventionella standardmetoder. Arbetet sjösattes med en litteraturstudie på ämnet klinkerproduktion, cementhydratation och reaktivitetstester av cement och alternativa bindemedel. Därefter utvecklades malningsmetoden med hjälp av industriell referensklinker. Slutligen testades dessa och ett antal andra klinkers, både framställda i laboratorieugn och industriellt, för reaktivitet med ICC, XRD och TGA. Malningsmetodens resultat blev något grövre, men ändå i hög grad jämförbart med dagens konventionella metod. Denna skillnad är dock liten och förutsägbar. Därför blev också uppmätt värme i ICC jämförbart med tidigare värden från den konventionella metoden. På grund av den något grövre malningen, vilket leder till mindre reaktionsyta för cementet-vatten-fasen, så blev värmeutvecklingen i ICC alltid något lägre jämfört med den konventionella metoden, dock aldrig utanför gränserna för vad standardmetodens reproducerbarhet är. Tack vare detta dras slutsatsen att protokollet kommer vara relevant och lämpligt för introduktion i industrin. Cementens reaktivitet studerades också i högre detalj med hjälp av TGA och XRD, vilka användes för extern validering av varandra. Medan dessa metoder ger viktig information om varje enskild fas i den åldrande pastan, så är slutsatsen att de är i fortsatt behov av utveckling. Detta har mest att göra med provberedningen. Nödvändiga förbättringar är bättre Rietveld kvantifiering med fler prover och försiktigare provberedning för att förhindra karbonatisering av cementpastorna. TGA metoden kan enkelt förbättras och uppnå avsevärt bättre resultat endast genom införandet av en separat analys av ettringit. Trots detta så visar de två metoderna hög korrelation mellan varandra då provberedningen fungerat som avsett, vilket är lovande och innebär att man med dessa enkla förslag kan skapa en metod som ger information om ett cements reaktivitet i mycket högre detalj än vad som är möjligt med dagens standardmetoder. Som förslag till framtida arbeten ges att protokollet bör utökas till att även bedöma prestandan av alternativa bindemedel vid spädning av klinker. / Cemzero

Since Galileo Galilei invented the first thermometer, researchers have tried to understand the complex dynamics of ocean and atmosphere by means of scientific methods. They observe nature and formulate theories about the climate system. Since some decades powerful computers are capable to simulate the past and future evolution of climate.<br><br> Time series analysis tries to link the observed data to the computer models: Using statistical methods, one estimates characteristic properties of the underlying climatological processes that in turn can enter the models. The quality of an estimation is evaluated by means of error bars and significance testing. On the one hand, such a test should be capable to detect interesting features, i.e. be sensitive. On the other hand, it should be robust and sort out false positive results, i.e. be specific. <br><br> This thesis mainly aims to contribute to methodological questions of time series analysis with a focus on sensitivity and specificity and to apply the investigated methods to recent climatological problems. <br><br> First, the inference of long-range correlations by means of Detrended Fluctuation Analysis (DFA) is studied. It is argued that power-law scaling of the fluctuation function and thus long-memory may not be assumed a priori but have to be established. This requires to investigate the local slopes of the fluctuation function. The variability characteristic for stochastic processes is accounted for by calculating empirical confidence regions. The comparison of a long-memory with a short-memory model shows that the inference of long-range correlations from a finite amount of data by means of DFA is not specific. When aiming to infer short memory by means of DFA, a local slope larger than $alpha=0.5$ for large scales does not necessarily imply long-memory. Also, a finite scaling of the autocorrelation function is shifted to larger scales in the fluctuation function. It turns out that long-range correlations cannot be concluded unambiguously from the DFA results for the Prague temperature data set. <br><br> In the second part of the thesis, an equivalence class of nonstationary Gaussian stochastic processes is defined in the wavelet domain. These processes are characterized by means of wavelet multipliers and exhibit well defined time dependent spectral properties; they allow one to generate realizations of any nonstationary Gaussian process. The dependency of the realizations on the wavelets used for the generation is studied, bias and variance of the wavelet sample spectrum are calculated. To overcome the difficulties of multiple testing, an areawise significance test is developed and compared to the conventional pointwise test in terms of sensitivity and specificity. Applications to Climatological and Hydrological questions are presented. The thesis at hand mainly aims to contribute to methodological questions of time series analysis and to apply the investigated methods to recent climatological problems. <br><br> In the last part, the coupling between El Nino/Southern Oscillation (ENSO) and the Indian Monsoon on inter-annual time scales is studied by means of Hilbert transformation and a curvature defined phase. This method allows one to investigate the relation of two oscillating systems with respect to their phases, independently of their amplitudes. The performance of the technique is evaluated using a toy model. From the data, distinct epochs are identified, especially two intervals of phase coherence, 1886-1908 and 1964-1980, confirming earlier findings from a new point of view. A significance test of high specificity corroborates these results. Also so far unknown periods of coupling invisible to linear methods are detected. These findings suggest that the decreasing correlation during the last decades might be partly inherent to the ENSO/Monsoon system. Finally, a possible interpretation of how volcanic radiative forcing could cause the coupling is outlined. / Seit der Erfindung des Thermometers durch Galileo Galilei versuchen Forscher mit naturwissenschaftlichen Methoden die komplexen Zusammenhänge in der Atmosphäre und den Ozeanen zu entschlüsseln. Sie beobachten die Natur und stellen Theorien über das Klimasystem auf. Seit wenigen Jahrzehnten werden sie dabei von immer leistungsfähigeren Computern unterstützt, die das Klima der Erdgeschichte und der nahen Zukunft simulieren. <br><br> Die Verbindung aus den Beobachtungen und den Modellen versucht die Zeitreihen­analyse herzustellen: Aus den Daten werden mit statistischen Methoden charak­teristische Eigenschaften der zugrundeliegenden klimatologischen Prozesse geschätzt, die dann in die Modelle einfliessen können. Die Bewertung solch einer Schätzung, die stets Messfehlern und Vereinfachungen des Modells unterworfen ist, erfolgt statistisch entweder mittels Konfidenzintervallen oder Signifikanztests. Solche Tests sollen auf der einen Seite charakteristische Eigenschaften in den Daten erkennen können, d.h. sie sollen sensitiv sein. Auf der anderen Seite sollen sie jedoch auch keine Eigenschaften vortäuschen, d.h. sie sollen spezifisch sein. Für die vertrauenswürdige Untermauerung einer Hypothese ist also ein spezifischer Test erforderlich. <br><br> Die vorliegende Arbeit untersucht verschiedene Methoden der Zeitreihenanalyse, erweitert sie gegebenenfalls und wendet sie auf typische klimatologische Frage­stellungen an. Besonderes Augenmerk wird dabei auf die Spezifizität der jeweiligen Methode gelegt; die Grenzen möglicher Folgerungen mittels Datenanalyse werden diskutiert.<br><br> Im ersten Teil der Arbeit wird studiert, wie und ob sich mithilfe der sogenannten trendbereinigenden Fluktuationsanalyse aus Temperaturzeitreihen ein sogenanntes langes Gedächtnis der zugrundeliegenden Prozesse herleiten lässt. Solch ein Gedächtnis bedeutet, dass der Prozess seine Vergangenheit nie vergisst, mit fundamentalen Auswirkungen auf die gesamte statistische Beurteilung des Klimasystems. Diese Arbeit konnte jedoch zeigen, dass die Analysemethode vollkommen unspezifisch ist und die Hypothese “Langes Gedächtnis” gar nicht abgelehnt werden kann. <br><br> Im zweiten Teil werden zunächst Mängel einer sehr populären Analysemethode, der sogenannten kontinuierlichen Waveletspetralanalyse diskutiert. Diese Methode schätzt die Variabilität eines Prozesses auf verschiedenen Schwingungsperioden zu bestimm­ten Zeiten. Ein wichtiger Nachteil der bisherigen Methodik sind auch hier unspezi­fische Signifikanztests. Ausgehend von der Diskussion wird eine Theorie der Wavelet­spektralanalyse entwickelt, die ein breites Feld an neuen Anwendungen öffnet. Darauf basierend werden spezifische Signifikanztests konstruiert.<br><br> Im letzten Teil der Arbeit wird der Einfluss des El Niño/Southern Oscillation Phäno­mens auf den Indischen Sommermonsun analysiert. Es wird untersucht, ob und wann die Oszillationen beider Phänomene synchron ablaufen. Dazu wird eine etablierte Methode für die speziellen Bedürfnisse der Analyse von typischerweise sehr unregel­mäßigen Klimadaten erweitert. Mittels eines spezifischen Signifikanztests konnten bisherige Ergebnisse mit erhöhter Genauigkeit bestätigt werden. Zusätzlich konnte diese Methode jedoch auch neue Kopplungsintervalle feststellen, die die Hypothese entkräften konnten, dass ein neuerliches Verschwinden der Kopplung ein beisspielloser Vorgang sei. Schliesslich wird eine Hypothese vorgestellt, wie vulkanische Aerosole die Kopplung beeinflussen könnten.

[pt] A análise de sistemas de medição consiste do exame da adequação do sistema quanto ao operador, ao instrumento e a outras fontes de variação, bem como da comparação da variância do erro de medição com a variância natural do processo. Nesse aspecto, esta pesquisa teve por objetivo a análise das incertezas da quantificação de fase pelo método de Rietveld em análise de pó. Os efeitos de vários fatores na quantificação de fase foram avaliados utilizando técnicas estatísticas de planejamento experimental e de análise multivariada, com a utilização de materiais de alto nível de rastreabilidade na realização dos experimentos, no Laboratório de difração de raios X do Departamento de Ciências de Materiais e Metalurgia da PUC-Rio. Através da determinação do construto de variação do processo, constatou-se que a quantificação das fases analisadas sofre influência das condições de medição de forma diferenciada de material para material, impossibilitando a obtenção de uma fórmula geral para cálculo dos erros de quantificação, embora os erros possam ser determinados por uma análise de repetitividade e reprodutibilidade apropriadamente conduzida. / [en] The analysis of measurement systems is done by the examination of the adequacy of the system according to the operator, the instrument and other sources of variability, as well as by the comparison of the measurement error variance with the natural process variance. This research consisted in the evaluation of the uncertainties of phase quantification in powder analysis by the Rietveld method. The evaluation of the effects of several factors on the phase quantification was performed using statistical techniques of design of experiments and of multivariate analysis, with the use of materials of high level of traceability for the conduction of the experiments, in the Laboratory of X-ray Diffraction of the Pontifícia Universidade Católica do Rio de Janeiro. Through the determination of the variational structure of the process it was verified that the analyzed phases suffer influence of the measurement conditions in a differentiated way, which prevents the obtention of a general formula for calculation of the quantification error, although the errors can be determined by a repeatability and reproducibility analysis properly conducted.

This work is devoted to establishment of the chemical composition and conditions of formation and stability of the amorphous phase arising in the Fe-Si-Cu-Mn-Mg-O system in the course of high-temperature annealing. The materials used for research cold rolled strips 0,70 mm of alloy thick, containing were used (in % on weight): Si – 3,1, Cu – 0,5, Mn – 0,3, other iron and inevitable impurity. The main methods used of a research the high-temperature x-ray phase analysis, the scanning electronic microscopy with electron probe analyses. Upon studying the processes occurring on the surface of a Fe-3%Si-0,5%Cu alloy sample with a heat resistant MgO coating during continuous annealing at a temperature range of 600…1060 °C, the formation of an amorphous phase in the form of a Fe-based solid solution was observed using the non-ambient XRD technique. This phenomenon was observed in a layer composed of α-Fe and (MgFe)2SiO4, (MgFe)O, SiO2 oxides upon heating in the temperature range corresponding to α→γ transformation, that is, 920…960 °C. The amorphous state of the thin film was preserved during the subsequent annealing, both during heating and during cooling to a temperature of 20 °C. / Данная работа посвящена установлению химического состава и условий формирования стабильной аморфной фазы, возникающей в системе Fe-Si-Cu-Mn-Mg-O в процессе высокотемпературного отжига. В качестве материала для исследования использовались холоднокатаные полосы толщиной 0,70 мм сплава, содержащего (в % по массе): Si – 3,1, Сu – 0,5, Mn – 0,3, остальное железо и неизбежные примеси. В качестве основных методов исследования использовались высокотемпературный рентгеновский фазовый анализ, сканирующая электронная микроскопия с электронно-зондовым (МРСА) анализами. Интегральный химический анализ слоев материала от поверхности вглубь образцов проводился с применением анализатора тлеющего разряда GDA-750. При исследовании процессов, происходящих на поверхности сплава Fe-3%Si-0,5%Cu c термостойким покрытием MgO, при непрерывном отжиге в интервале температур 600…1060°C методом терморентгенографии обнаружено образование аморфной фазы в виде твердого раствора на основе Fe. Эффект наблюдался в слое, состоящем из α-Fe, оксидов (MgFe)2SiO4, (MgFe)O, SiO2, при нагреве в температурном интервале, соответствующем α→γ превращению: 920…960 °C. Аморфное состояние тонкого слоя сохраняется в процессе дальнейшего отжига, как при повышении температуры, так и при охлаждении до 20°C.

In Gasturbinenbrennern kommen Nickelbasiswerkstoffe für thermisch hoch belastete Komponenten standardmäßig zum Einsatz. Die Bauteile liegen strömungstechnisch vor der stattfindenden Verbrennung, wodurch es zu einer stark einseitigen thermischen Belastung kommt. Ein wirtschaftlich effizienter Einsatz von Nickelbasiswerkstoffen kann daher in Kombination mit kostengünstigen warmfesten Stählen für die weniger stark thermisch belasteten Bauteilbereiche erreicht werden. Ziel der vorliegenden Arbeit ist die Prozessentwicklung zum Hochtemperaturlöten von im Brennerbau häufig verwendeten Nickelbasislegierungen und dem niedriglegierten warmfesten Stahl 16Mo3 (1.5415). Im Entwicklungsprozess wurden die Mikrostruktur der Verbunde charakterisiert, die Auswirkungen thermischer Ausdehnungsunterschiede evaluiert und die erreichbare Festigkeit erfasst. An einem Demonstrator wurden die Erkenntnisse im Rahmen der industriellen Fertigung getestet.:1 Einführung 1.1 Einleitung und Motivation 1.2 Stand von Wissenschaft und Technik 1.3 Schlussfolgerungen und Zielsetzung 2 Technologische Grundlagen 2.1 Der Hochtemperaturlötprozess 2.2 Thermische Ausdehnung 2.3 Diffusion 2.4 Metallurgische Prozesse 3 Experimentelle Durchführung 3.1 Grund- und Lotwerkstoffe 3.2 Lötprozesse und Probengeometrien 3.3 Mikrostrukturelle, thermische und mechanische Charakterisierung 4 Ergebnisse und Diskussion 4.1 Mikrostrukturcharakterisierung 4.1.1 Grundwerkstoffe 4.1.2 Lötsystem 16Mo3 – INCONEL 625 4.1.3 Lötsystem 16Mo3 – Nimonic 75 4.1.4 Lötsystem 16Mo3 – Hastelloy X 4.1.5 Lötsystem 16Mo3 – INCONEL 718 4.1.6 Normalisierungsgefüge von 16Mo3 4.1.7 Zusammenfassung der Mikrostrukturcharakterisierung 4.2 Thermische Ausdehnung 4.2.1 Maßänderung 4.2.2 Eigenspannungen 4.3 Mechanische Eigenschaften 4.3.1 Zugversuch 4.3.2 Zugscherversuch 4.3.3 Ermittlung der kritischen Überlapplänge 4.4 Demonstrator 5 Zusammenfassung und Ausblick / Nickel-base alloys for thermally high loaded components are widely used for gas turbine burner parts. By means of flow direction burner parts are located prior to the combustion. They are therefore one-sided thermally loaded. An economical efficient use of nickel based alloys can be achieved in combination with low alloyed steels for thermally less loaded components. The aim of this work is the development of brazing processes for GT-burner manufacturing related nickel based alloys and the low alloyed steel 16Mo3 (1.5415) using nickel based filler materials. The development includes a microstructural characterization of the brazed compounds, the evaluation of thermal expansion behavior and the maximum strength. A final test examines the feasibility by means of industrial manufacturing.:1 Einführung 1.1 Einleitung und Motivation 1.2 Stand von Wissenschaft und Technik 1.3 Schlussfolgerungen und Zielsetzung 2 Technologische Grundlagen 2.1 Der Hochtemperaturlötprozess 2.2 Thermische Ausdehnung 2.3 Diffusion 2.4 Metallurgische Prozesse 3 Experimentelle Durchführung 3.1 Grund- und Lotwerkstoffe 3.2 Lötprozesse und Probengeometrien 3.3 Mikrostrukturelle, thermische und mechanische Charakterisierung 4 Ergebnisse und Diskussion 4.1 Mikrostrukturcharakterisierung 4.1.1 Grundwerkstoffe 4.1.2 Lötsystem 16Mo3 – INCONEL 625 4.1.3 Lötsystem 16Mo3 – Nimonic 75 4.1.4 Lötsystem 16Mo3 – Hastelloy X 4.1.5 Lötsystem 16Mo3 – INCONEL 718 4.1.6 Normalisierungsgefüge von 16Mo3 4.1.7 Zusammenfassung der Mikrostrukturcharakterisierung 4.2 Thermische Ausdehnung 4.2.1 Maßänderung 4.2.2 Eigenspannungen 4.3 Mechanische Eigenschaften 4.3.1 Zugversuch 4.3.2 Zugscherversuch 4.3.3 Ermittlung der kritischen Überlapplänge 4.4 Demonstrator 5 Zusammenfassung und Ausblick