• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2
  • Tagged with
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 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

Multimaterial Fibers And Tapers A Platform For Nonlinear Photonics And Nanotechnology

Shabahang, Soroush 01 January 2014 (has links)
The development of optical sources and components suitable for the mid-infrared is crucial for applications in this spectral range to reach the maturity level of their counterparts in the visible and near-infrared spectral regimes. The recent commercialization of quantum cascade lasers is leading to further interest in this spectral range. Wideband mid-infrared coherent sources, such as supercontinuum generation, have yet to be fully developed. A mid-infrared supercontinuum source would allow for unique applications in spectroscopy and sensing. Over the last decade, it has been shown that high-index confinement in highly nonlinear fibers pumped with high-peak-power pulses is an excellent approach to supercontinuum generation in the visible and near-infrared. Nonlinear waveguides such as fibers offer an obvious advantage in increasing the nonlinear interaction length maintained with a small cross section. In addition, fiber systems do not require optical alignment and are mechanically stable and robust with respect to the environmental changes. These properties have made fiber systems unique in applications where they are implemented in a harsh and unstable environment. In extending this approach into the mid-infrared, I have used chalcogenide glass fibers. Chalcogenide glasses have several attractive features for this application: they have high refractive indices for high optical-confinement, have a wide transparency window in the mid-infrared, and have a few orders-of-magnitude higher nonlinearity than silica glass and other mid-IR glasses. Producing chalcogenide glass fiber tapers offer, furthermore, the possibility of dispersion control and stronger field confinement and hence higher nonlinearity, desired for supercontinuum generation.
2

Magnetically Ordered Bimettalic Oxide-Composite Pseudocapacitive Materials for Supercapacitors Applications / FERRIMAGNETIC OXIDE-COMPOSITE MATERIALS FOR SUPERCAPACITORS

MacDonald, Michael January 2024 (has links)
This thesis contains the research performed on novel magnetically ordered pseudocapacitive materials (MOPCs) which display interesting and unique capacitive properties. These properties are a result of the strong magneto-capacitive and magneto-electric coupling characteristics that MOPC materials possess at room temperature. The purpose of this research is to investigate the unique capacitive properties of NiFe2O4 (NFO) and SrFe12O19(SFO) by examining the effects that the high energy ball milling procedure, the addition of a charge transfer mediation and biomimetic dispersing agent called gallocyanine dye, and the formation of composite electrodes at varying mass ratios with pseudocapacitive conducting polypyrrole polymer have on the capacitance of NFO and SFO. / The enhanced cycle stability, cycle lifetime, capacitance retention, and power densities of electrochemical capacitors make them an increasingly attractive option for modern energy storage needs, including grid level energy storage systems, mobile electronics, heavy construction equipment, military communication devices, power tools, public transportation, electric vehicles and capacitive water deionization systems to name a few. Recently, materials that displayed magnetoelectric coupling phenomena leading to enhanced magneto-capacitive properties are of particular interest, specifically ferrimagnetic spinels and hexagonal ferrites. This thesis is aimed at improving the capacitive performance of NiFe2O4 (NFO) and SrFe12O19 (SFO) based magnetically ordered pseudocapacitor electrodes by elucidating the effects of various nanomaterials preparation techniques on capacitance. The nanomaterials preparation techniques explored in this body of work include the addition of biomimetic dispersing agents, application of high energy ball milling, and forming composites using n-doped conducting pseudocapacitive polypyrrole polymers. Project 1 explored how the addition of gallocyanine dye (GCD) dispersing agent affects the capacitance of NFO. Additionally, the effects of the high energy ball milling (HEBM) process on capacitance were explored and these results were combined with the optimized gallocyanine dye results. Lastly NFO composites with Tiron-doped PPy were prepared at varying mass ratios and combined with optimized HEBM results to achieve the best capacitance results. Project 2 utilized the optimized GCD mass ratios with HEBM to enhance the capacitance of SFO. Tiron doped PPy was used with HEBM SFO at varying mass ratios to achieve the best performing composite electrode. Lastly, the best electrode composition from project 2 was used as anode in an aqueous asymmetric cell using MnO2 as the cathode, proving to be a viable anode chemistry in practical electrochemical capacitor applications. / Thesis / Master of Applied Science (MASc) / The global power demand has been increasing rapidly since the advent of the industrial era, unfortunately human civilization has mostly relied upon fossil fuels to provide the necessary energy for the function of society resulting in vast quantities of greenhouse gases being released into the atmosphere, having a global warming effect on the planet. Recently renewable energy production technologies have been developed but many are intermittent in nature and require efficient energy storage devices to properly hold that energy. Additionally, with countless industries requiring varying quantities of energy or power, the solution for adequate energy storage is a complex multifaceted one that cannot be solved by one energy storage technology alone. For this reason, additional energy storage technology must be developed. The main goal of this work is to develop electrochemical capacitor (ECs) technology, an energy storage solution with greater capacitance retention, cycle stability and cycle lifetime attributes at high charge-discharge rates relative to current battery technology, meaning that ECs can outperform batteries in high power demand applications such as; regenerative breaking, hand-held power tools, heavy construction equipment and even the large energy fluctuations associated with grid level energy storage. Materials with novel magnetic properties were explored to be developed for high active mass loaded electrodes using advanced nano-materials preparation techniques to enhance capacitance. Doing so increased the performance of these energy storage devices drastically, overcoming the poor intercalation attributes associated with high active mass loaded electrodes, making them viable for practical energy storage applications.

Page generated in 0.1078 seconds