704 research outputs found
Advanced Materials and Technologies in Nanogenerators
This reprint discusses the various applications, new materials, and evolution in the field of nanogenerators. This lays the foundation for the popularization of their broad applications in energy science, environmental protection, wearable electronics, self-powered sensors, medical science, robotics, and artificial intelligence
Edoardo Benvenuto Prize. Collection of papers
The promotion of studies and research on the science and art of building in their historical development constitutes the objective that the Edoardo Benvenuto Association has set itself, since its establishment, in order to honor the memory of Edoardo Benvenuto (1940-1998). The Association in recent years has achieved interesting results by developing various activities such as: organization of national and international meetings, conferences, study days; collaborations with national and foreign research institutions; promotion of the editorial series âBetween Mechanics and Architecture"; activation of the portal Bibliotheca Mechanica Architectonica, first âopen sourceâ digitized library dedicated to historical research on mechanical and architectural texts. But perhaps the most qualifying initiative was the institution of the Edoardo Benvenuto Prize, arrived in 2019 in its twelfth edition, reserved for young researchers in the field of historical studies on science and the art of building. The awarding of the Prize takes place after an in-depth examination of the texts received by the Association by an international commission of experts. The purpose of this book is to collect and present the most recent studies and publications produced by the winners of the various editions of the Edoardo Benvenuto Prize
Advances in Micro- and Nanomechanics
This book focuses on recent advances in both theoretical and experimental studies of material behaviour at the micro- and nano-scales. Special attention is given to experimental studies of nanofilms, nanoparticles and nanocomposites as well as tooth defects. Various experimental techniques were used. Magneto- and thermoelastic coupling were considered, as were nonlocal models of thin structures
Using experiment and first-principles to explore the stability of solid electrolytes for all-solid-state lithium batteries
Cotutelle entre l'UniversitĂ© de MontrĂ©al et l'UniversitĂ© catholique de LouvainLes batteries aux ions lithium (BIL) sont considĂ©rĂ©es comme la technologie la plus prometteuse en matiĂšre de stockage dâĂ©nergie. Elles possĂšdent les plus hautes densitĂ©s dâĂ©nergie connues, permettant la miniaturisation constante des appareils Ă©lectroniques commercialisĂ©s. La recherche dans le domaine des BIL sâest plus rĂ©cemment tournĂ©e vers leur implĂ©mentation dans les vĂ©hicules Ă©lectriques, qui nĂ©cessitera de plus hautes densitĂ©s dâĂ©nergie et de puissance . Une maniĂšre concrĂšte dâaugmenter la densitĂ© dâĂ©nergie dâune BIL est dâen augmenter le voltage de cellule. Pour se faire, la nouvelle gĂ©nĂ©ration de batteries sera composĂ©e de matĂ©riaux dâĂ©lectrode positive Ă haut potentiel (tel que LiMn1.5Ni0.5O4 avec un potentiel de 4.7 V vs. Li+ /Li) et de lithium mĂ©tallique en Ă©lectrode nĂ©gative. NĂ©anmoins, lâintroduction de ces matĂ©riaux dâĂ©lectrode positive Ă haut potentiel est limitĂ©e par la stabilitĂ© Ă©lectrochimique de lâĂ©lectrolyte liquide conventionnel, composĂ© dâun sel de lithium et de solvants organiques (typiquement LiPF6 + EC/DEC), qui sâoxyde autour de 4.2 V vs. Li+/Li , . Lâutilisation du lithium mĂ©tallique comme Ă©lectrode nĂ©gative est entravĂ©e par la nature liquide de lâĂ©lectrolyte conventionnel, qui nâoffre pas assez de rĂ©sistance mĂ©canique pour empĂȘcher la formation de dendrites de lithium, causant Ă terme le court-circuit de la batterie. De tels courts-circuits prĂ©sentent un risque dâincendie car les Ă©lectrolytes liquides sont composĂ©s de solvants organiques inflammables Ă basse tempĂ©rature, posant un sĂ©rieux problĂšme de sĂ©curitĂ©.
Les Ă©lectrolytes solides, de type cĂ©ramique ou polymĂšres, sont dĂ©veloppĂ©s en alternative aux Ă©lectrolytes liquides. Ils ne contiennent aucun solvant inflammable et sont stables Ă haute tempĂ©rature. Ils constituent lâĂ©lĂ©ment clĂ© dâune nouvelle gĂ©nĂ©ration de batteries au lithium dite batteries au lithium tout-solide. Ces derniĂšres sont dĂ©veloppĂ©es pour rĂ©pondre Ă des attentes Ă©levĂ©es en termes de sĂ©curitĂ©, de stabilitĂ© et de haute densitĂ© dâĂ©nergie. Les Ă©lectrolytes solides doivent satisfaire un certain nombre d'exigences avant de pouvoir ĂȘtre commercialisĂ©s, notamment possĂ©der une conductivitĂ© ionique Ă©levĂ©e, une large fenĂȘtre de stabilitĂ© Ă©lectrochimique et une conductivitĂ© Ă©lectronique nĂ©gligeable. Ces propriĂ©tĂ©s constituent les critĂšres les plus importants Ă prendre en compte pour la sĂ©lection de matĂ©riaux dâĂ©lectrolytes solides. Cependant, on remarque dans la littĂ©rature que la majoritĂ© des Ă©tudes se concentre sur la conductivitĂ© ionique des Ă©lectrolytes solides, relĂ©guant au second plan lâexploration de leurs stabilitĂ© Ă©lectrochimique et conductivitĂ© Ă©lectronique. La fenĂȘtre de stabilitĂ© Ă©lectrochimique a longtemps Ă©tĂ© annoncĂ©e comme Ă©tant trĂšs large chez les Ă©lectrolytes solides cĂ©ramiques (au moins de 0 Ă 5 V vs. Li+/Li). NĂ©anmoins, des Ă©tudes plus rĂ©centes tendent Ă dĂ©montrer que la valeur de cette fenĂȘtre dĂ©pend grandement de la mĂ©thode Ă©lectrochimique utilisĂ©e pour la mesurer, et quâelle est de surcroit souvent surestimĂ©e. Dans ce contexte, le premier objectif de cette thĂšse a Ă©tĂ© de dĂ©velopper une mĂ©thode pertinente pour dĂ©terminer la fenĂȘtre de stabilitĂ© des Ă©lectrolytes solides avec prĂ©cision. Cette mĂ©thode a Ă©tĂ© optimisĂ©e et validĂ©e sur des Ă©lectrolytes solides cĂ©ramiques phare comme Li1.5Al0.5Ge1.5(PO4)3, Li1.3Al0.3Ti1.7(PO4)3 et Li7La3Zr2O12. Quant Ă la conductivitĂ© Ă©lectronique, elle est rarement Ă©tudiĂ©e dans les Ă©lectrolytes solides, qui sont considĂ©rĂ©s comme isolants Ă©lectroniques compte tenu de leur large bande interdite. Cela dit, de rĂ©centes Ă©tudes Ă ce sujet prouvent que malgrĂ© leur bande interdite, les Ă©lectrolytes solides peuvent gĂ©nĂ©rer de la conductivitĂ© Ă©lectronique par le biais de dĂ©fauts, et que celle-ci, mĂȘme faible, peut Ă©ventuellement mettre lâĂ©lectrolyte en Ă©chec. Pour cette raison, le second objectif de ce projet de thĂšse a Ă©tĂ© dâexplorer la formation de dĂ©fauts dans les Ă©lectrolytes solides afin de dĂ©terminer leur effet sur la gĂ©nĂ©ration de conductivitĂ© Ă©lectronique. Pour avoir une vision dâensemble, les premiers-principes ont Ă©tĂ© utilisĂ©s pour Ă©tudier six Ă©lectrolytes solides largement utilisĂ©s notamment LiGe2(PO4)3, LiTi2(PO4)3, Li7La3Zr2O12, et Li3PS4.Lithium-ion batteries (LIBs) are considered the most promising energy storage technology. LIBs electrode materials have the highest known energy densities, allowing the constant miniaturization of commercial electronic devices. Research in the field of LIBs has more recently turned to their implementation in electric vehicles, which will require higher energy and power densities . A concrete way to increase the energy density of LIBs is to increase the cell voltage. To do so, the new generation of batteries will be composed of high potential positive electrode materials (such as LiMn1.5Ni0.5O4 with a potential of 4.7 V vs. Li+/Li) and metallic lithium in the negative electrode. Nevertheless, the introduction of these high potential positive electrode materials is limited by the electrochemical stability of conventional liquid electrolytes, composed of a lithium salt and organic solvents (LiPF6 + EC/DEC), which gets oxidized around 4.2 V vs. Li+/Li , . The use of metallic lithium as the negative electrode is also hindered by the liquid nature of the conventional electrolyte, which does not offer enough mechanical resistance to prevent the formation of lithium dendrites, ultimately causing a short-circuit of the battery. Such short-circuits are likely to lead to thermal runaway because liquid electrolytes are composed of organic solvents that are flammable at low temperature, posing a serious safety issue.
Solid electrolytes, based on ceramics or polymers, are developed as an alternative to liquid electrolytes. They contain no flammable solvents and are stable at high temperatures. They are the key element of a new generation of lithium batteries called all-solid-state lithium batteries. These are developed to meet high expectations in terms of safety, stability and high energy density. Solid electrolytes must satisfy a number of requirements before they can be commercialized, including possessing a high ionic conductivity, a wide electrochemical stability window and negligible electronic conductivity. These properties are the most important criteria to consider when selecting solid electrolyte materials. However, the majority of studies found in the literature focuses on the ionic conductivity of solid electrolytes, overshadowing the exploration of their electrochemical stability and electronic conductivity. The electrochemical stability window has long been reported to be very wide in ceramic solid electrolytes (at least from 0 to 5 V vs. Li+/Li). Nevertheless, more recent studies tend to show that the value of this window depends greatly on the electrochemical method used to measure it, and that it is often overestimated. In this context, the first objective of this thesis was to develop a relevant method to determine the stability window of solid electrolytes with precision. This method was optimized and validated on flagship ceramic solid electrolytes such as Li1.5Al0.5Ge1.5(PO4)3, Li1.3Al0.3Ti1.7(PO4)3 and Li7La3Zr2O12. As for the electronic conductivity, it is scarcely studied in solid electrolytes, which are considered as electronic insulators given their wide band gaps. That being said, more recent studies on this subject proved that despite their band gap, solid electrolytes can generate electronic conductivity through defects, and that electronic conductivity, even if it is weak, can eventually cause the failure of the electrolyte. For this reason, the second objective of this thesis project was to explore the formation of defects in solid electrolytes in order to determine their effect on the generation of electronic conductivity. To get a better overview, first-principles were used to investigate six widely used ceramic solid electrolytes, including LiGe2(PO4)3, LiTi2(PO4)3, Li7La3Zr2O12, and Li3PS4
Towards a mesoscale rheology model for aqueous particulate suspensions
Particulate suspensions are ubiquitous and diverse; pharmaceutical formulations, biological fluids, magma and foodstuffs are just few of numerous examples. In many cases, the flow behaviour (rheology) of the suspension is critical to its function. A key rheological property is viscosity; a measure of a substanceâs resistance to flow. This work aims to understand molecular-level mechanisms responsible for determining flow behaviour in moderately dense suspensions; 35% particles by volume (i.e., volume fraction 0.35). The industrial application of interest to this thesis is catalysis; namely, the âwashcoatâ, a key component in the performance of catalytic converters. A typical washcoat formulation is an aqueous suspension, comprising a high surface-area support powder, an active catalyst material, together with organic additives and certain salts used to optimise properties of the washcoat; including its flow behaviour. Of these components, this work investigates âsalt-specific effectsâ; i.e. the influence of differing salt-types. Investigation is conducted at molecular and macroscopic resolution via simulations and experiments, respectively. The research approach probes the constituents of a suspension: the aqueous phase, the particle-aqueous phase interface, and particle interactions. Molecular dynamics simulations are employed as the foundation of this analysis, with experiments - rheology, nuclear magnetic resonance and dynamic light scattering - utilised alongside. A final set of rheology experiments is conducted on particulate suspensions of 35% volume fraction, in pure water and the aqueous salt solutions of interest. At all stages of analysis, results suggest that macroscopic behaviours are a cumulative manifestation of phenomena at molecular resolution. However, such phenomena are varied; the challenge lies in identifying which mechanisms are relevant to the behaviour of interest, how they work together, and how they manifest cumulatively. Towards a mesoscale rheology model for aqueous particulate suspensions, results are discussed in terms of input for such a model, which would predict rheology as a function of particle loading, ionic strength and possibly other factors, in future work
Modelling bacterial biofilms in spatially heterogeneous environments
Biofi lms are communities of one or more species of microorganism which have
adhered both together and to a surface. Biofi lms are ubiquitous in nature,
with up to 80% of bacterial life on earth estimated to be found in a biofi lm.
Bacterial biofi lms are far more resilient to both chemical and physical methods of
removal than their planktonic counterparts, which presents numerous challenges
in both clinical and industrial scenarios. Therefore, further research into the
underlying mechanisms of how these biofi lms develop and survive is essential.
This thesis aims to do so via the implementation of various computational
modelling techniques.
Currently, most computational modelling of biofi lms is done under somewhat
idealised conditions, such as uniform antibiotic concentrations and mono-species
bio lms, which do not always reflect the complex conditions found in vivo.
This thesis therefore also aims to address this problem by using computational
models to understand how biofi lms proliferate and resist methods of removal
in spatially heterogeneous environments, such as chemical gradients of nutrients
and antibiotics, or non-uniform
flow fi elds. The thesis takes the form of three
distinct projects, which are linked together by this common theme of spatial
non-uniformity.
Presented fi rst is an investigation into the coupling between nutrient availability
and growth-dependent antibiotic susceptibility. This project uses a simple 1D
Monte-Carlo model to simulate the advancement of a bacterial population along a
spatial antibiotic concentration gradient. Bacterial replication consumes nutrients
which in turn lowers the local growth rate, altering the antibiotic susceptibility.
The results highlight the differing outcomes for antibiotics which target either
slow-growing or fast-growing cells.
Following this, the next project investigates the initial stages of biofi lm formation
on a surface. This chapter involves a pair of complementary models, a
deterministic one, involving a system of differential equations; and a stochastic
one, where the individual bacteria are simulated using a modifi ed Î-leaping
algorithm, both again in 1D. By modifying the rates for certain actions
which the bacteria undertake, the models predict that under certain conditions
biofi lm formation is highly predictable, but for other parameter regimes, bio lm
formation becomes more stochastic.
In the third project, the stochastic biofi lm formation model described above
is extended to develop a model for the formation of biofi lms on a surface
which leaches an antimicrobial compound into the surrounding environment,
similar to current antifouling coatings used to prevent marine biofouling in the
shipping industry. A key difference in this model is the inclusion of multiple
bacterial species, each with differing resistances to the applied biocide, intended
to represent the biodiversity found in a typical marine environment.
Finally, a computational
fluid dynamics model is presented, which is used to
model the interaction between a micro-structured surface featuring shark skin-like
riblets and an enveloping biofi lm, when exposed to an external
flow fi eld
of various incident
flow angles. These riblets are a contemporary solution to
reducing hydrodynamic drag, e.g., on ship hulls, but are only effective when their
physical shape is unobstructed. Investigating how misaligned riblets can impede,
or even prevent, the sloughing of bio lm matter is therefore crucial to optimising
their performance
PhD studentsÂŽday FMST 2023
The authors gave oral presentations of their work online as part of a Doctoral Studentsâ Day held on 15 June 2023, and they reflect the challenging work done by the students and their supervisors in the fields of metallurgy, materials engineering and management. There are 82 contributions in total, covering a range of areas â metallurgical technology, thermal engineering and fuels in industry, chemical metallurgy, nanotechnology, materials science and engineering, and industrial systems management. This represents a cross-section of the diverse topics investigated by doctoral students at the faculty, and it will provide a guide for Masterâs graduates in these or similar disciplines who are interested in pursuing their scientific careers further, whether they are from the faculty here in Ostrava or engineering faculties elsewhere in the Czech Republic. The quality of the contributions varies: some are of average quality, but many reach a standard comparable with research articles published in established journals focusing on disciplines of materials technology. The diversity of topics, and in some cases the excellence of the contributions, with logical structure and clearly formulated conclusions, reflect the high standard of the doctoral programme at the faculty.Ostrav
Liquid Metal Printing with Scanning Probe Lithography for Printed Electronics
In den letzten Jahren hat das âInternet der Dingeâ (Englisch Internet of Things, abgekĂŒrzt IoT), das auch als Internet of Everything (Deutsch frei âInternet von Allemâ) bezeichnet wird, mit dem Aufkommen der âIndustrie 4.0â einen Strom innovativer und intelligenter sensorgestĂŒtzter Elektronik der neuen Generation in den Alltag gebracht. Dies erfordert auch die Herstellung einer riesigen Anzahl von elektronischen Bauteilen, einschlieĂlich Sensoren, Aktoren und anderen Komponenten. Gleichzeitig ist die herkömmliche Elektronikfertigung zu einem hochkomplexen und investitionsintensiven Prozess geworden. In dem MaĂe, wie die Zahl der elektronischen Bauteile und die Nachfrage nach neuen, fortschrittlicheren elektronischen Bauteilen zunimmt, steigt auch die Notwendigkeit, effizientere und nachhaltigere Wege zur Herstellung dieser Bauteile zu finden. Die gedruckte Elektronik ist ein wachsender Markt, der diese Nachfrage befriedigen und die Zukunft der Herstellung von elektronischen GerĂ€ten neu gestalten könnte. Sie erlaubt eine einfache und kostengĂŒnstige Produktion und ermöglicht die Herstellung von GerĂ€ten auf Papier- oder Kunststoffsubstraten. FĂŒr die Herstellung gibt es dabei eine Vielzahl von Methoden. Techniken auf der Grundlage der Rastersondenlithografie waren dabei schon immer Teil der gedruckten Elektronik und haben zu Innovationen in diesem Bereich gefĂŒhrt. Obwohl die Technologie noch jung ist und der derzeitige Stand der gedruckten Elektronik im industriellen MaĂstab, wie z. B. die Herstellung kompletter integrierter Schaltkreise, stark limitiert ist, sind die potenziellen Anwendungen enorm.
Im Mittelpunkt der Entwicklung gedruckter elektronischer Schaltungen steht der Druck leitfĂ€higer und anderer funktionaler Materialien. Die meisten der derzeit verfĂŒgbaren Arbeiten haben sich dabei auf die Verwendung von Tinten auf Nanopartikelbasis konzentriert. Die Herstellungsschritte auf der Grundlage von Tinten auf Nanopartikelbasis sind komplizierte Prozesse, da sie das AusglĂŒhen (Englisch Annealing) und weitere Nachbearbeitungsschritte umfassen, um die gedruckten Muster leitfĂ€hig zu machen. Die Verwendung von Gallium-basierten, bei/nahe Raumtemperatur flĂŒssigen Metallen und deren direktes Schreiben fĂŒr vollstĂ€ndig gedruckte Elektronik ist immer noch ungewöhnlich, da die Kombination aus dem Vorhandensein einer Oxidschicht, hohen OberflĂ€chenspannungen und ViskositĂ€t ihre Handhabung erschwert.
Zu diesem Zweck zielt diese Arbeit darauf ab, Methoden zum Drucken von Materialien, einschlieĂlich FlĂŒssigmetallen, zu entwickeln, die mit den verfĂŒgbaren Druckmethoden nicht oder nur schwer gedruckt werden können und diese Methoden zur Herstellung vollstĂ€ndig gedruckter elektronischer Bauteile zu verwenden. Weiter werden Lösungen fĂŒr Probleme wĂ€hrend des Druckprozesses untersucht, wie z. B. die Haftung der Tinte auf dem Substrat und andere abscheidungsrelevante Aspekte. Es wird auch versucht, wissenschaftliche Fragen zur StabilitĂ€t von gedruckten elektronischen Bauelementen auf FlĂŒssigmetallbasis zu beantworten.
Im Rahmen der vorliegenden Arbeit wurde eine auf Glaskapillaren basierenden Direktschreibmethode fĂŒr das Drucken von FlĂŒssigmetallen, hier Galinstan, entwickelt. Die Methode wurde auf zwei unterschiedlichen Wegen implementiert: Einmal in einer âHochleistungsversionâ, basierend auf einem angepassten NanolithographiegerĂ€t, aber ebenfalls in einer hochflexiblen, auf Mikromanipulatoren basierenden Version. Dieser Aufbau erlaubt einen on-the-fly (âim Flugeâ) kapillarbasierten Druck auf einer breiten Palette von Geometrien, wie am Beispiel von vertikalen, vertieften OberflĂ€chen sowie gestapelten 3D-GerĂŒsten als schwer zugĂ€ngliche OberflĂ€chen gezeigt wird. Die Arbeit erkundet den potenziellen Einsatz dieser Methode fĂŒr die Herstellung von vollstĂ€ndig gedruckten durch FlĂŒssigmetall ermöglichten Bauteilen, einschlieĂlich WiderstĂ€nden, Mikroheizer, p-n-Dioden und Feldeffekttransistoren. Alle diese elektronischen Bauelemente werden ausfĂŒhrlich charakterisiert. Die hergestellten Mikroheizerstrukturen werden fĂŒr temperaturgeschaltete Mikroventile eingesetzt, um den FlĂŒssigkeitsstrom in einem Mikrokanal zu kontrollieren. Diese Demonstration und die einfache Herstellung zeigt, dass das Konzept auch auf andere Anwendungen, wie z.B. die bedarfsgerechte Herstellung von Mikroheizern fĂŒr in-situ Rasterelektronenmikroskop-Experimente, ausgeweitet werden kann.
DarĂŒber hinaus zeigt diese Arbeit, wie PMMA-Verkapselung als effektive Barriere gegen Sauerstoff und Feuchtigkeit fungiert und zusĂ€tzlich als brauchbarer mechanischer Schutz der auf FlĂŒssigmetall basierenden gedruckten elektronischen Bauteile wirken kann. Insgesamt zeigen der alleinstehende, integrierte Herstellungsablauf und die FunktionalitĂ€t der GerĂ€te, dass das Potenzial des FlĂŒssigmetall-Drucks in der gedruckten Elektronik viel gröĂer ist als einzig die Verwendung zur Verbindung konventioneller elektronischer Bauteile.
Neben der Entwicklung von Druckverfahren und der Herstellung elektronischer Bauteile befasst sich die Arbeit auch mit der Korrosion und der zusĂ€tzlichen Legierung von konventionellen Metallelektroden in Kontakt mit FlĂŒssigmetallen, welche die StabilitĂ€t der Bauteil beintrĂ€chtigen könnten. Zu diesem Zweck wurde eine korrelierte Materialinteraktionsstudie von gedruckten Galinstan- und Goldelektroden durchgefĂŒhrt. Durch die kombinierte Anwendung von optischer Mikroskopie, vertikaler Rasterinterferometrie, Rasterelektronenmikroskopie, Röntgenphotonenspektroskopie und Rasterkraftmikroskopie konnte der Ausbreitungsprozess von FlĂŒssigmetalllinien auf Goldfilmen eingehend charakterisiert werden. Diese Studie zeigt eine unterschiedliche Ausbreitung der verschiedenen Komponenten des FlĂŒssigmetalls sowie die Bildung von intermetallischen Nanostrukturen auf der umgebenden GoldfilmoberflĂ€che. Auf der Grundlage der erhaltenen zeitabhĂ€ngigen, korrelierten Charakterisierungsergebnisse wird ein Modell fĂŒr den Ausbreitungsprozess vorgeschlagen, das auf dem Eindringen des FlĂŒssigmetalls in den Goldfilm basiert. Um eine ergĂ€nzende Perspektive auf die interne Nanostruktur zu erhalten, wurde die Röntgen-Nanotomographie eingesetzt, um die Verteilung von Gold, Galinstan und intermetallischen Phasen in einem in das FlĂŒssigmetall getauchten Golddraht zu untersuchen. Schlussendlich werden Langzeitmessungen des Widerstands an FlĂŒssigmetallleitungen, die Goldelektroden verbinden, durchgefĂŒhrt, was dazu beitrĂ€gt, die Auswirkungen von Materialwechselwirkungen auf elektronische Anwendungen zu bewerten
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