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Die Methode ist entscheidend - Optimierung der Herstellungsstrategien für Ti3C2Tx-Nb2CTx-MXene-Hybridbeschichtungen
No full textTribologische Kontakte leisten einen wesentlichen Beitrag zum globalen Energieverbrauch und zu den damit verbundenen CO2-Emissionen, vor allem durch Reibungsverluste und verschleißbedingtes Bauteilversagen. Die Verbesserung von Effizienz und Lebensdauer solcher Kontakte ist daher von großem technologischem Interesse, insbesondere in Anwendungen, in denen konventionelle Flüssigschmierstoffe ungeeignet sind. Unter den neuartigen Festschmierstoffen haben zweidimensionale Übergangsmetallcarbide und -nitride (MXene) aufgrund ihrer geschichteten Struktur, ihrer einstellbaren Oberflächenchemie und ihrer vorteilhaften tribologischen Eigenschaften besondere Aufmerksamkeit erlangt. Während Ti3C2Tx MXene intensiv untersucht wurden, sind Nb2CTx MXene sowie hybride MXen-Systeme bislang wenig erforscht.Diese Arbeit untersucht das tribologische Verhalten hybrider Ti3C2Tx–Nb2CTx-MXen- Beschichtungen sowie den Einfluss von Herstellungs- und Konsolidierungsstrategien auf deren Stabilität und Lebensdauer. Der Fokus liegt auf binderfreien Prozessrouten, bei denen die Leistungssteigerung durch Optimierung der Herstellung statt durch chemische Modifikation erreicht wird. Hybride Beschichtungen mit Massenverhältnissen von 25:75, 50:50 und 75:25 (Ti3C2Tx:Nb2CTx) sowie Referenzbeschichtungen aus einzelnen MXenen wurden mittels LuftsprühverfahrenVerfahren oder Tropfguss auf spiegelpolierte X5CrNi18-10-(1.4301-)Edelstahlsubstrate aufgebracht und anschließend kalt- oder heißgepresst.Die Beschichtungen wurden mittels Laser-Scanning-, Rasterelektronen- und Transmissionselektronenmikroskopie sowie energiedispersiver Röntgenspektroskopie charakterisiert. Tribologische Untersuchungen wurden in linearen reziproken Gleitversuchen gegen einen Al2O3-Gegenkörper bei 1 N Normalkraft durchgeführt, entsprechend einem maximalen Hertz’schen Kontaktdruck von etwa 0,7 GPa. Diese vergleichsweise hohen Belastungen dienten der Bewertung der Haftung und der Tribofilmstabilität. Die Ergebnisse zeigen, dass vor allem die Beschichtungshaftung und strukturelle Integrität die Dauerhaftigkeit bestimmen, während die Schichtdicke eine untergeordnete Rolle spielt.Hybride Beschichtungen, insbesondere mit Nb2CTx-Anteil, zeigten eine höhere Stabilität als Einzel-MXen-Beschichtungen. Eine mechanische Konsolidierung erwies sich als entscheidend, da vorkompaktierte Schichten eine deutlich erhöhte Beständigkeit unter hohen Kontaktpressungen aufwiesen. Damit wird gezeigt, dass allein durch geeignete Herstellungs- und Konsolidierungsstrategien die tribologische Leistungsfähigkeit binderfreier MXen-basierter Schmierstoffe für anspruchsvolle Einsatzbedingungen deutlich verbessert werden kann.Tribological contacts are major contributors to global energy consumption and associated CO2 emissions, primarily due to frictional losses and wear-induced component failure. Enhancing the efficiency and durability of these contacts is of significant technological interest, especially in scenarios where conventional liquid lubricants are ineffective or impractical. Among emerging solid lubricants, two-dimensional transition-metal carbides and nitrides (MXenes) have garnered considerable attention. Their layered structure, tuneable surface chemistry, and advantageous tribological properties render them promising candidates. Although Ti3C2Tx MXenes have been extensively studied, Nb2CTx MXenes and hybrid combinations of various MXene compositions remain relatively unexplored.This thesis investigates the tribological behaviour of hybrid Ti3C2Tx–Nb2CTx MXene coatings and evaluates the influence of fabrication and consolidation strategies on coating stability and durability. The research emphasises binder-free processing routes to enhance coating performance through fabrication optimisation rather than chemical modification. Hybrid coatings with defined mass ratios (25:75, 50:50, and 75:25 Ti3C2Tx:Nb2CTx), along with single-MXene reference coatings, were deposited on mirror-polished X5CrNi18-10 (1.4301) stainless-steel substrates. Deposition methods included air-spraying and drop-casting, followed by cold- and hot-pressing as consolidation steps.Coating morphology and structural integrity were characterised using laser scanning microscopy, scanning electron microscopy, and transmission electron microscopy, complemented by energy-dispersive X-ray spectroscopy. Tribological testing involved linear reciprocating sliding experiments against an Al2O3 counterbody at a normal load of 1 N, corresponding to a maximum Hertzian contact pressure of approximately 0.7 GPa. These conditions represent more demanding wear and contact-pressure regimes than those typically reported in MXene tribology and were chosen to assess coating adhesion and tribofilm stability. The results indicate that coating adhesion and structural integrity are the primary factors determining durability and lifetime, while coating thickness plays a secondary role. Hybrid coatings, particularly those containing Nb2CTx, exhibited greater stability than single-MXene coatings. Mechanical consolidation proved critical; pre-compacted coatings, such as drop-cast layers followed by cold or hot pressing, demonstrated enhanced resistance to failure under high contact pressures. These findings establish that fabrication and consolidation strategies alone can improve tribological performance, offering a systematic foundation for the development of binder-free MXene-based lubricants suitable for demanding conditions
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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