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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Graphol and vanadia-link zin doped lithium manganese silicate nanoarchitectonic platforms for supercapatteries

Ndipingwi, Miranda Mengwi January 2020 (has links)
Doctor Educationis / Energy storage technologies are rapidly being developed due to the increased awareness of global warming and growing reliance of society on renewable energy sources. Among various electrochemical energy storage technologies, high power supercapacitors and lithium ion batteries with excellent energy density stand out in terms of their flexibility and scalability. However, supercapacitors are handicapped by low energy density and batteries lag behind in power. Supercapatteries have emerged as hybrid devices which synergize the merits of supercapacitors and batteries with the likelihood of becoming the ultimate power sources for multi-function electronic equipment and electric/hybrid vehicles in the future. But the need for new and advanced electrodes is key to enhancing the performance of supercapatteries. Leading edge technologies in material design such as nanoarchitectonics become very relevant in this regard. This work involves the preparation of vanadium pentoxide (V2O5), pristine and zinc doped lithium manganese silicate (Li2MnSiO4) nanoarchitectures as well as their composites with hydroxylated graphene (G-ol) and carbon nanotubes (CNT). / 2023-12-02
2

Von "chiralen" Superhelices zu achiralen Nanostrukturen

Ouart, André 28 September 2000 (has links)
In dieser Arbeit wurden spektroskopische und strukturelle Untersuchungen an chiralen und achiralen supramolekularen Nanoarchitekturen von J-Aggregaten achiraler Cyaninfarbstoffe durchgeführt. Als Modellsysteme wurden Tetrachlorobenzimidacarbocyanin- Farbstoffe mit unterschiedlichen 1,1´-Dialkyl- und 3,3´-Bis-acidoalkyl-Gruppen verwendet. Zur Charakterisierung der Nanostrukturen wurden statische spektroskopische Methoden - UV/Vis-Spektroskopie, Circulardichroismus (CD)- und Fluoreszenzspektroskopie -, Röntgenkristallstrukturanalyse,sowie kryogene Transmissionselektronenmikroskopie (Cryo-TEM) verwendet. Die delikate Balance der Wechselwirkungskräfte, wie z. B. hydrophobe Wechselwirkung, Dispersionswechselwirkung, sowie Wasserstoffbrücken, führt bei der J-Aggregation von strukturell ähnlichen achiralen Chromophoren zu "chiralen" Superhelices und achiralen nanoskopischen Bändern. Durch Kombination der hydrophoben und hydrophilen Eigenschaften von Tensiden mit den unikalen Eigenschaften von J-Aggregaten entstehen Nanoröhren und Vesikel. Diese Nanostrukturen sind daher vielversprechende Kandidaten für künstliche Lichtsammel- und Antennensysteme. / In this work spectroscopic and structural investigations were performed on chiral and achiral supramolecular nanoarchitectures of J-aggregates of achiral cyanine dyes. Tetrachlorobenzimidacarbocyanine dyes with different 1,1´-Dialkyl- and 3,3´-Bis-acidoalkyl- substituents were used as model systems. To characterize these nanoarchitectures static spectroscopic methods - UV/vis-spectroscopy, circular dichroism (CD)- and fluorescence-spectroscopy -, x-ray crystal structure analysis, as well as cryogenic transmission electron microscopy (cryo-TEM) were used. The delicate balance of intermolecular forces, like hydrophobic interaction, dispersion forces, as well as hydrogen bonds, leads by J-aggregation of structural similar achiral chromophores to "chiral" superhelices and achiral nanoscopic ribbons. By combination of the hydrophobic and hydrophilic properties of surfactants with the unique properties of J-aggregates nanotubules and vesicles are built. These nanostructures are hopeful candidates for artificial antenna and light harvesting systems.
3

Reconfigurable Logic Architectures based on Disruptive Technologies / Architectures logiques reconfigurables utilisant les propriétés de l'électronique moléculaire

Gaillardon, Pierre-Emmanuel 15 September 2011 (has links)
Durant les quatre dernières décennies, l’industrie des semi-conducteurs a connu une croissance exponentielle. En accord avec l’ITRS et à mesure de l'approche vers le nanomètre, les promesses sont énormes et les composants sont réduits à leurs limites physiques et économiques ultimes. L’objectif principal de cette thèse est d’explorer les opportunités offertes par les technologies émergentes pour la conception d’architectures reconfigurables. Tout d’abord, la thèse se centre sur l’architecture FPGA traditionnelle et étudie des améliorations structurelles apportées par des technologies en ruptures. Tandis que les structures de configuration et de routage occupent la majeure partie de la surface d’un FPGA et limitent ces performances, l’intégration 3-D apparait comme une bonne opportunité pour déplacer ces circuits dans les niveaux métalliques. Des circuits de configuration et de routage utilisant des mémoires résistives compatibles back-end, un procédé d’intégration 3-D ou encore un procédé de réalisation de transistors verticaux seront introduits et évalués dans un contexte architectural complet. Par la suite, la thèse présente de nouvelles propositions architecturales pour la logique à grain ultra-fin. La taille des éléments logiques peut être réduite grâce aux propriétés inhérentes de certaines technologies, telles que l’arrangement en structures entrecroisées de nanofils ou la polarité contrôlable des transistors carbones. Considérant le changement de granularité des opérateurs logiques, des topologies d’interconnexions fixes sont nécessaires afin d’éviter l’important surcoût dû à l’interconnexion programmable. Afin d’étudier les possibilités de cette organisation, un flot d’évaluation est présenté et utilisé pour explorer l’espace de conception relatif aux architectures à grain ultra-fin. / For the last four decades, the semiconductor industry has experienced an exponential growth. According to the ITRS, as we advance into the era of nanotechnology, the traditional CMOS electronics is reaching its physical and economical limits. The main objective of this thesis is to explore novel design opportunities for reconfigurable architectures given by the emerging technologies. On the one hand, the thesis will focus on the traditional FPGA architecture scheme, and survey some structural improvements brought by disruptive technologies. While the memories and routing structures occupy the major part of the FPGAs total area and mainly limit the performances, 3-D integration appears as a good candidate to embed all this circuitry into the metal layers. Configuration and routing circuits based on back-end compatible resistive memories, a monolithic 3-D process flow and a prospective vertical FETs process flow are introduced and assessed within a complete architectural context. On the other hand, the thesis will present some novel architectural schemes for ultra-fine grain computing. The size of the logic elements can be reduced thanks to inherent properties of the technologies, such as the crossbar organization or the controllable polarity of carbon electronics. Considering the granularity of the logic elements, specific fixed and incomplete interconnection topologies are required to prevent the large overhead of a configurable interconnection pattern. To evaluate the potentiality of this new architectural scheme, a specific benchmarking flow will be presented in order to explore the ultra-fine grain architectural design space.
4

Graphol and vanadia-linkedzink-doped lithium manganese silicate nanoarchitectonic platforms for supercapatteries

Ndipingwi, Miranda Mengwi January 2020 (has links)
Philosophiae Doctor - PhD / Energy storage technologies are rapidly being developed due to the increased awareness of global warming and growing reliance of society on renewable energy sources. Among various electrochemical energy storage technologies, high power supercapacitors and lithium ion batteries with excellent energy density stand out in terms of their flexibility and scalability. However, supercapacitors are handicapped by low energy density and batteries lag behind in power. Supercapatteries have emerged as hybrid devices which synergize the merits of supercapacitors and batteries with the likelihood of becoming the ultimate power sources for multi-function electronic equipment and electric/hybrid vehicles in the future. But the need for new and advanced electrodes is key to enhancing the performance of supercapatteries. Leading-edge technologies in material design such as nanoarchitectonics become very relevant in this regard. This work involves the preparation of vanadium pentoxide (V2O5), pristine and zinc doped lithium manganese silicate (Li2MnSiO4) nanoarchitectures as well as their composites with hydroxylated graphene (G-ol) and carbon nanotubes (CNT). / 2023-12-01

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