Дисертації з теми "High energy density electrodes"
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1
Reck, James Nicholas. "Thin film techniques for the fabrication of nano-scale high energy density capacitors." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Reck_09007dcc805c0c2a.pdf.
Анотація:
Thesis (Ph. D.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed March 18, 2009) Includes bibliographical references.
2
Partridge, James M. "Development of a micro-retarding potential analyzer for high-density flowing plasmas." Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-111005-142414/.
Анотація:
Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: Ion Energy Distribution; Current Collection Theory; Energy Diagnostic; Retarding Potential Analyzer; Electric Propulsion. Includes bibliographical references. (p.91-95)
3
Armutlulu, Andac. "Deterministically engineered, high power density energy storage devices enabled by MEMS technologies." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54270.
Анотація:
This study focuses on the design, fabrication, and characterization of deterministically engineered, three-dimensional architectures to be used as high-performance electrodes in energy storage applications. These high-surface-area architectures are created by the robotically-assisted sequential electrodeposition of structural and sacrificial layers in an alternating fashion, followed by the removal of the sacrificial layers. The primary goal of this study is the incorporation of these highly laminated architectures into the battery electrodes to improve their power density without compromising their energy density. MEMS technologies, as well as electrochemical techniques, are utilized for the realization of these high-power electrodes with precisely controlled characteristic dimensions. Diffusion-limited models are adopted for the determination of the optimum characteristic dimensions of the electrodes, including the surface area, the thickness of the active material film, and the distance between the adjacent layers of the multilayer structure.
The contribution of the resultant structures to the power performance is first demonstrated by a proof-of-concept Zn-air microbattery which is based on a multilayer Ni backbone coated with a conformal Zn film serving as the anode. This primary battery system demonstrates superior performance to its thin-film counterpart in terms of the energy density at high discharge rates. Another demonstration involves secondary battery chemistries, including Ni(OH)2 and Li-ion systems, both of which exhibit significant cycling stability and remarkable power capability by delivering more than 50% of their capacities after ultra-fast charge rates of 60 C. Areal capacities as high as 5.1 mAh cm-2 are reported. This multilayer fabrication approach is also proven successful for realizing high-performance electrochemical capacitors. Ni(OH)2-based electrochemical capacitors feature a relatively high areal capacitance of 1319 mF cm-2 and an outstanding cycling stability with a 94% capacity retention after more than 1000 cycles.
The improved power performance of the electrodes is realized by the simultaneous minimization of the internal resistances encountered during the transport of the ionic and electronic species at high charge and discharge rates. The high surface area provided by the highly laminated backbone structures enables an increased number of active sites for the redox reactions. The formation of a thin and conformal active material film on this high surface area structure renders a reduced ionic diffusion and electronic conduction path length, mitigating the power-limiting effect of the active materials with low conductivities. Also, the highly conductive backbone serving as a mechanically stable and electrochemically inert current collector features minimized transport resistance for the electrons. Finally, the highly scalable nature of the multilayer structures enables the realization of high-performance electrodes for a wide range of applications from autonomous microsystems to macroscale portable electronic devices.
4
Luo, Jingru. "Electrode and Electrolyte Design for High Energy Density Batteries:." Thesis, Boston College, 2020. http://hdl.handle.net/2345/bc-ir:108928.
Анотація:
Thesis advisor: Udayan MohantyThesis advisor: Dunwei Wang
With the fast development of society, the demand for batteries has been increasing dramatically over the years. To satisfy the ever-increasing demand for high energy density, different chemistries were explored. From the first-generation lead–acid batteries to the state-of-the-art LIBs (lithium ion batteries), the energy density has been improved from 40 to over 200 Wh kg⁻¹. However, the development of LIBs has approached the upper limit. Electrode materials based on insertion chemistry generally deliver a low capacity of no more than 400 mAh/g. To break the bottleneck of current battery technologies, new chemistries are needed. Moving from the intercalation chemistry to conversion chemistry is a trend. The conversion electrode materials feature much higher capacity than the conventional intercalation-type materials, especially for the O₂ cathode and Li metal anode. The combination of these two can bring about a ten-folds of energy density increase to the current LIBs. Moreover, to satisfy the safety requirements, either using non-flammable electrolytes to reduce the safety risk of Li metal anode or switch to dendrite-free Mg anode is a good strategy toward high energy density batteries. First, to enable the conversion-type O₂ cathode, a wood-derived, free-standing porous carbon electrode was demonstrated and successfully be applied as a cathode in Li-O₂ batteries. The spontaneously formed hierarchical porous structure exhibits good performance in facilitating the mass transport and hosting the discharge products of Li₂O₂. Heteroatom (N) doping further improves the catalytic activity of the carbon cathode with lower overpotential and higher capacity. Next, to solve the irreversible Li plating/stripping and safety issues related with Li metal anode, we introduced O₂ as additives to enable Li metal anode operation in non-flammable triethyl phosphate (TEP) electrolyte. The electrochemically induced chemical reaction between O₂- derived species and TEP solvent molecules facilitated the beneficial SEI components formation and effectively suppressed the TEP decomposition. The promise of safe TEP electrolyte was also demonstrated in Li-O₂ battery and Li-LFP battery. If we think beyond Li chemistries, Mg anode with dendrite-free property can be a promising candidate to further reduce the safety concerns while remaining the high energy density advantage. Toward the end of this thesis, we developed a thin film metal–organic framework (MOF) for selective Mg²⁺ transport to solve the incompatibility issues between the anode and the cathode chemistry for Mg batteries
Thesis (PhD) — Boston College, 2020
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
5
Ihrfors, Charlotte. "Binder-free oxide nanotube electrodes for high energy and power density 3D Li-ion microbatteries." Thesis, Uppsala universitet, Strukturkemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-227451.
Анотація:
This thesis covers synthesis and characterisation of TiO2 nanotubes and TiO2 / Li4Ti5O12 composite nanotubes. The aim was to build batteries with high areal capacity and good rate capability. TiO2 nanotubes were synthesized by two step anodization of titanium metal foil and the composite electrodes were synthesized through electrochemical lithiation of TiO2 nanotubes. To improve the battery performance the TiO2 nanotubes were annealed at 350 °C in air atmosphere, while the composite electrodes were annealed in argon at 550 °C. The longest TiO2 nanotubes were measured to 42.5 μm. The 40 μm long nanotubes displayed an areal capacity of 1.0 mAh/cm2 and a gravimetric capacity of 89 mAh/g. Nanotubes having a length of 10 μm had an areal capacity of 0.33 mAh/cm2 and a gravimetriccapacity of 130 mAh/g. When cycled at high rates, 10C, the capacity of the 40 μm nanotubes was 0.25 mAh/cm2, using a current density of 9.3 mA. The capacity of the 40 μm long nanotubes were higher than for the 10 μm long, but the increase was not proportional to the increase in length. A composite electrode was successfully synthesized and was found to have a capacity of 0.25 mAh/cm2 at a rate of C/5.
6
Lim, Tongli. "Fabrication of high energy density tin/carbon anode using reduction expansion synthesis and aerosol through plasma techniques." Thesis, Monterey, California: Naval Postgraduate School, 2017. http://hdl.handle.net/10945/53011.
Анотація:
Approved for public release; distribution is unlimitedThe aim of this study was to fabricate tin/carbon (Sn/C) battery anodes using a novel approach, reduction expansion synthesis (RES), and test their performance as electrodes in lithium or sodium batteries. A second preparation route, the Aerosol-Through-Plasma (ATP) method, was also employed for comparison. The specimens generated were characterized, before and after cycling, using techniques such as X-ray diffraction, scanning, and transmission electron microscopy. The RES technique was successful in creating remarkably small (ca. <5 nm) nano-scale particles of tin dispersed on the carbon support. The use of the electrodes as part of coin cell batteries resulted in capacitance values of 320 mAh/g and 110 mAh/g for lithium-ion and sodium-ion batteries, respectively. Nano-sized Sn particles were found before and after cycling. It is believed that bonds between metal atoms and dangling carbon produced via the reduction of the carbon surface during RES were responsible for the materials' ability to withstand stresses during lithiation, avoid volumetric expansion, and prevent disintegration after hundreds of cycles. When tin loading in Sn/C was increased from 10% to 20%, an increase of capacitance from 280 mAh/g to 320mAh/g was observed; thus, increased tin loading is recommended for future studies. Tin/carbon produced using ATP presented morphology consistent with stable electrodes, although battery testing was not completed because of the difficulty of producing the material in sufficient quantity.
Military Expert 5, Republic of Singapore Navy
7
Breitenbach, Rene. "Development of Free-standing Nanostructured Iron Oxide Electrodes for High Energy and Power Density 3D Li-ion Microbatteries." Thesis, Uppsala universitet, Strukturkemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-301338.
8
Jenicek, David P. (David Pierre). "Improvements on carbon nanotube structures in high-energy density ultracapacitor electrode design." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93063.
Анотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 125-134).
Ultracapacitors are a class of electrochemical energy storage device that is gaining significant industrial traction due to their high charging rate and cycle life compared to rechargeable batteries; however, they store significantly less energy on a per-volume basis. The quest to find an electrode material that could bridge the gap between energy and power density in electrochemical storage devices has been the object of significant industrial and academic research efforts over the past two decades. One promising material, and the focus of this research, is a dense forest of vertically-aligned carbon nanotubes (CNTs). Previous work at MIT has projected that such structures could augment the energy density of ultracapacitors by a factor of five over existing packaged devices. This thesis is an investigation into the electrode fabrication techniques that approach this goal. Carbon nanotube forests are synthesized on thin tungsten substrates by chemical vapor deposition (CVD) to form porous, high-surface area electrodes. We demonstrate that the capacitance of CNT electrodes is very highly correlated to the morphological and geometrical features of the CNT forest. These features, such as areal density, mean nanotube diameter, and nanotube length, are shown to be tunable and a series of pre- and post-treatment steps are examined to achieve two specific goals: an increased electrode specific surface area (m²/cm³ ) and an improved differential capacitance ([mu]F/cm² of CNT surface). Substrates are prepared for CVD by depositing a thin sub-nanometer film of catalytically active material via magnetron sputtering. Electrodes we fabricated using this conventional technique did not exhibit a specific surface area large enough to provide the high capacitance required for energy-dense electrodes. Numerous enhancements to this "standard" procedure are explored, such as varying the material deposition rate and substrate temperature, adding reactive gases during deposition, and depositing multiple catalyst layers. A nearly 5x increase in specific surface area is achieved. Furthermore, the surface properties of as-grown CNTs are modified by exposure to reactive plasmas and other high-energy environments; these treatments result in over a 2 x increase in differential capacitance. Compounded, the fabrication methods explored in this thesis provide a nearly 10x performance increase over conventional CNT electrodes, with a demonstrated cell capacitance of 56 mF using two 1 cm² electrodes. Finally, some key arguments are presented that assess the commercial viability of CNT-based ultracapacitors.
by David P. Jenicek.
Ph. D.
9
Ho, Bryan Y. "An experimental study on the structure-property relationship of composite fluid electrodes for use in high energy density semi-solid flow cells." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/101864.
Анотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, February 2012.Cataloged from PDF version of thesis.
Includes bibliographical references.
A novel electrochemical energy storage device, the semi-solid flow cell (SSFC), has recently been demonstrated. The device features a complex fluid composite as its anode and cathode. Both electrodes incorporate particles of a lithium storage compound suspended in a carbon black electrolyte gel. This design of a mixed conductor gel host and electrochemically active filler allows for fluid electrodes to be pumped, from storage tanks, through reaction cells. The de-coupling of energy and power capacity in a high energy density device opens up new opportunities for low cost, high performance energy storage. This thesis explores the microstructure of these fluid composites and establishes links to macroscopic properties that determine the device's energy and power density, efficiency, and cycle life. The rapid agglomeration of colloidal carbon black aggregates leads to gelation by diffusion limited cluster aggregation. The low density, percolating network of carbon provides conduction paths for both ions and electrons. The gel's yield stress stably suspends density mismatched particles of lithium storage compounds, which can readily access the electrochemical reactants via the gel matrix. Application of shear reversibly destroys the gel network, allowing for flow. Flow-induced heterogeneities are also investigated and methods of maintaining macroscopic homogeneity are presented.
by Bryan Y. Ho.
Ph. D.
10
Krygier, Andrew. "On The Origin of Super-Hot Electrons in Intense Laser-Plasma Interactions." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1365724528.
11
Ngirmang, Gregory Kodeb. "Particle-in-Cell Simulations of the Acceleration of Electrons from the Interaction of a Relativistic Laser Reflecting from Solid Density Targets." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1514985418694386.
12
Feister, Scott. "Efficient Acceleration of Electrons by an Intense Laser and its Reflection." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461225902.
13
Palmer, Michael. "High voltage positive electrodes for high energy lithium-ion batteries." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/398001/.
Анотація:
Lithium-ion high voltage cathode materials are discussed within this thesis, with LiCoPO4 as a composite electrode evaluated for use as the active compound within lithium half-cells. A comprehensive literature review on lithium containing cathode materials with a focus on high voltage materials is provided. The majority of the materials within this work were synthesised using solvothermal techniques, which were characterised through XRD and SEM. Composite type electrodes were prepared through mainly using PTFE as the binder material, and different electrolytes were also investigated. Composite electrodes were electrochemically evulated with competitive capacites obtained compared to the literature. The performance of the LiCoPO4 composite electrodes was found to be significantly different and attributed to the use of different synthesis solvents and heating conditions used for synthesis. The rate performance and electrochemical cycling was found to depend highly on the surface area and particle size of the composite electrode. XANES and in-situ XRD was performed at Diamond Light Source (UK synchrotron), where the LiCoPO4 charge profile was fully characterised. It was found that LiCoPO4 undergoes transient lattice parameter changes during charging, and that phase recovery during any relaxations was observed.
14
Kim, Hyea. "High energy density direct methanol fuel cells." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37106.
Анотація:
The goal of this dissertation was to create a new class of DMFC targeted at high energy density and low loss for small electronic devices. In order for the DMFC to efficiently use all its fuel, with a minimum of balance of plant, a low-loss proton exchange membrane was required. Moderate conductivity and ultra low methanol permeability were needed. Fuel loss is the dominant loss mechanism for low power systems. By replacing the polymer membrane with an inorganic glass membrane, the methanol permeability was reduced, leading to low fuel loss. In order to achieve steady state performance, a compliant, chemically stable electrode structure was investigated. An anode electrode structure to minimize the fuel loss was studied, so as to further increase the fuel cell efficiency. Inorganic proton conducting membranes and electrodes have been made through a sol-gel process. To achieve higher voltage and power, multiple fuel cells can be connected in series in a stack. For the limited volume allowed for the small electronic devices, a noble, compact DMFC stack was designed. Using an ADMFC with a traditional DMFC including PEM, twice higher voltage was achieved by sharing one methanol fuel tank. Since the current ADMFC technology is not as mature as the traditional DMFCs with PEM, the improvement was accomplished to achieve higher performance from ADMFC. The ultimate goal of this study was to develop a DMFC system with high energy density, high energy efficiency, longer-life and lower-cost for low power systems.
15
Olsson, Robbie Stefan Ian. "High energy density physics in cluster media." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/18394.
Анотація:
Gases comprised of atomic clusters have in the past been shown to exhibit extremely strong absorption of high-intensity laser pulses. By using this target medium, it is possible to use laser systems with only modest energies to create High Energy Density Plasmas. Not only are the plasmas created in this way of interest in themselves, but when properly designed, these experiments can be used as a platform for Laboratory Astrophysics studies of radiative blast waves. This thesis describes experiments which investigate the evolution of radiative blast waves, the interaction of relativistic laser pulses with large atomic clusters and the nature of the post laser-cluster interaction upstream medium into which the shock propagates. Experiments were carried out to diagnose the properties of the upstream medium into which radiative shocks launched by the laser-cluster interaction propagate. This experiment was conducted using the Blackett Laboratory Laser Consortium Nd:Glass laser system with a novel perpendicular heating beam geometry. By introducing a time delay between the perpendicular beams, it was possible to track the propagation of a ballistic cluster disassemble wave. This wave was shown to be the product of ~200 keV ions ejected by the initial laser cluster-interaction. Also discussed in this thesis are the results of the first laser-cluster experiment to be conducted on the Central Laser Facility's Astra-Gemini system. Here the interaction of large atomic clusters with relativistic laser pulses is investigated. X-Ray pinhole camera images have been captured of the early time plasma created by the laser-clusters interaction. For the first time the absorption properties of large atomic clusters irradiated by a femtosecond high energy, ~14 J, laser pulse have been studied. Furthermore, the temporal evolution of radiative blast waves launched from the laser-cluster interaction is described. In the past the Vulcan laser system at RAL was used to launch blast waves which displayed velocity domain oscillations driven by the radiation emitted by the blast wave. This instability has again been observed in the work reported here and the threshold for onset has been investigated.
16
Chung, Kang Ko. "Heteroatom-containing carbons for high energy density supercapacitor." Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2014/6982/.
Анотація:
The supercapacitor is one of the most important energy storage devices as its construction allows for addressing many of the drawbacks related to batteries, but the low energy density of current systems is a major issue. In this doctoral dissertation, with a view to attaining high energy density supercapacitor systems that can be comparable to those for batteries, new heteroatom-containing carbons in the form of particles and three-dimensional films were investigated. A nitrogen-containing material, acrodam, was chosen as the carbon precursor due to the inexpensiveness, high carbonization yield, oligomerizability, etc. The carbon particles were prepared from acrodam together with caesium acetate as a meltable flux agent, and disclosed excellent properties in hydroquinone-loaded sulphuric acid electrolyte with high energy densities (up to 133.0 Wh kg–1) and sufficient cycle stabilities. These properties are already now comparable to those of batteries. Besides, conductive carbon three-dimensional films were fabricated using acrodam oligomer as the precursor by the inexpensive spin coating method. The films were found to be homogeneous, flat, void- and crack-free, and high conductivities (up to 334 S cm–1) could be obtained at the carbonization temperature of 1000 ºC. Furthermore, a porous carbon three-dimensional film could be formed using an organic template at the first attempt. This finding demonstrates the film’s potentiality for various applications such as supercapacitor electrode; the essential absence of contact resistance within the network should contribute to effective transportation of electron within the electrode. The progress made in this dissertation will open a new way to further enhancement of energy density for supercapacitor as well as other applications that exceeds the current properties.Der Superkondensator ist einer der wichtigsten Energiespeicher da seine Konstruktion die Lösung vieler Nachteile von Batterien erlaubt. Allerdings weisen derzeitige Systeme noch zu geringe Energiedichten auf. Um Superkondensatoren mit Energiedichten vergleichbar zu Batterien zu ermöglichen, wurden in der vorliegenden Dissertation neue, heteroatomhaltige Kohlenstoffe in Form von Partikeln und Filmen untersucht. Aufgrund geringer Kosten, hohen Ausbeuten, Polymerisierbarkeit usw. wurde die stickstoffhaltige Substanz Acrodam als Kohlenstoffvorstufe verwendet. Die Kohlenstoffpartikel wurden ausgehend von Acrodam zusammen mit Cäsiumacetat als schmelzbares Flussmittel hergestellt und wiesen ausgezeichnete Eigenschaften in Hydrochinon geladenen Schwefelsäure-Elektrolyten mit hohen Energiedichten (bis zu 133,0 Wh kg–1) und guten Zyklusstabilitäten auf. Diese Eigenschaften sind bereits jetzt vergleichbar mit denen von Batterien. Weiterhin wurden unter Verwendung von Acrodamoligomeren als Vorstufe und mit Hilfe der kostengünstigen Rotationsbeschichtung leitfähige, dreidimensionale Kohlenstofffilme hergestellt. Bei einer Karbonisierungstemperatur von 1000 °C konnten die Materialien als homogene, flache, Hohlraum-und Riss-freie Filme erhalten werden, die eine hohe Leitfähigkeit (bis zu 334 S cm–1) aufwiesen. Darüber hinaus konnte mit einem organischen Templat ein dreidimensionaler, poröser Kohlenstoff geformt werden. Dies zeigt das Potential der Filme für verschiedene Anwendungen wie Superkondensatorelektroden; die Abwesenheit von Übergangswiderständen im Netzwerk sollte zu einem effizienten Transport von Elektronen in der Elektrode beitragen. Die Ergebnisse dieser Dissertation werden neue Wege zur Verbesserung der Energiedichte von Superkondensatoren sowie weiteren Anwendungen eröffnen.
17
Guillaud, Mathilde. "Neutrino oscillations at very high energy/matter density." Thesis, KTH, Fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-292510.
Анотація:
Neutrino oscillations in matter can be studied in different regimes, depending on the energy of the incoming neutrinos and the matter density of the medium. In this thesis we investigate neutrino oscillations in dense matter at very high energy (TeV-PeV range), taking into account the absorption that the neutrinos may undergo in such dense media. This absorption phenomenon is relevant for neutrino telescope measurements of astrophysical neutrinos. We begin with a brief reminder on neutrino oscillations in vacuum and the construction of the PMNS matrix. Then, we proceed with calculations for dense matter. We then explore the accuracy of the resulting effective 2-neutrino mixing formulas. They present a good accuracy for Earth-like densities in our range of energies. We develop the calculations for oscillation probabilities in dense matter with absorption through charged-current inelastic scattering for both the two-neutrino and three-neutrino case. We find that in dense media, astrophysical neutrinos indeed undergoabsorption, which reduces signicantly the fluxes for each flavor, with a resonant absorption of electron-anti-neutrinos around E_{res}\simeq 6.3PeV. We discuss the impact of neutrino absorption in the Earth for neutrino telescopes measurements. We find that solar and lunar shadowing is not problematic for current telescopes but could be a good angular resolution indicator for new telescopes to come.Neutrinooscillationer i materia kan studeras i olika regimer beroende på inkommande neutrinernas energi och densiteten hos det bakomliggande mediet. I detta examensarbete undersöker vi neutrinooscillationer i gränsen av tät materia och mycket hög energi (TeV-PeV-intervall), och tar hänsyn till den absorption av neutriner som då kan inträffa i sådant materia. Detta absorptionsfenomen är relevant för neutrino-teleskopmätningar av astrofysiska neutriner. Vi börjar med att kort påminna oss om neutrinooscillationer i vakuum och konstruktionen av PMNS-matrisen. Vi försätter sedan med beräkningar av neutrinooscillationer i tät materia. Vi undersöker noggrannheten i resulterande effektiva 2-neutrino-blandningsformlerna. De uppvisar en god noggrannhet i jordlika materieprofiler i vårt intervall av energier. Vi utvecklar beräkningarna av oscillationssannolikheterna i tät materia inklusive absorption genom laddad ström oelastisk spridning i båda två- och tresmaksfallen. Vi finner att astrofysiska neutriner i tät materia absorberas, vilket minskar betydligt flödena för varje smak, med en resonansabsorption av elektron-antineutrino omkring E_res\simeq 6.3PeV. Vi diskuterar sedan effekterna av neutrinoabsorption på jorden för neutrino-teleskopmätningar. Vi finner att sol- och månskuggning är inte problematisk för nuvarande teleskop och kunde vara en bra vinkelupplösningsindikator för kommande teeskop.
18
Lyu, Xiaofeng. "High-Power-Density Converter for Renewable Energy Application." Diss., North Dakota State University, 2017. https://hdl.handle.net/10365/26345.
Анотація:
Due to the energy crisis and environmental pollution, renewable sources are more and more important. Power electronics technology is widely applied in these emerging applications and its function is to make the power conversion. The efficiency of power converters is very important and also the size of power converters is more and more concerned. Therefore, high efficiency and high power density with little power loss and light weight are a trend for power converters. In this research work, light-emitting diode (LED) drivers are first investigated and advanced concaved current control is applied in AC-DC linear LED drivers, which can achieve high power density and high efficiency for indoor applications. Also, high-power-density single-phase DC-AC inverter with power decoupling function is a very hot topic in Photovoltaic (PV) applications. The research proposed an in-series and in-parallel power decoupling method to minimize the passive dc-link capacitance. Furthermore, an instantaneous pulse power compensator (IPPC) is proposed. When compared with the existing methods, it can achieve higher system power density. Besides, grid-tied controller is designed and tested. What?s more, three-phase inverter is investigated for the segmented motor in electric vehicle (EV) and hybrid electric vehicle (HEV) applications. Interleaved control methods are applied with different control schemes. High-power-density and high-efficiency three-phase inverter systems are compared. Finally, DC-DC switched-tank resonant converter is studied for 48V data center application. The proposed converter can achieve ultra-high efficiency and high power density. The planar inductor is designed and simulated with Maxwell software. The prototype is made and tested.
19
Locke, Jacob. "Silicon nanowires for high energy lithium-ion battery negative electrodes." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/384922/.
Анотація:
Samples of silicon nanowire materials, produced by Merck KGaA via a batched supercritical fluid method, were evaluated within composite electrodes for use as the active component in future lithium-ion battery negative electrodes. A comprehensive literature review of silicon based negative electrodes with a focus on silicon based composite type electrodes is provided. Characterisation of the nanowire materials was conducted via electron microscopy. Composite type electrodes were prepared utilising poly-acrylic acid as a binder material. Insight into the interaction of poly-acrylic acid with batch-1 nanowire material was achieved via a FTIR spectroscopy study, evidence for the formation of a binding interaction was observed. Composite electrodes containing nanowire material were electrochemically evaluated via the use of half-cells. The performance of the nanowire material samples was found to be significantly different and attributed to the use of differing precursor chemicals for synthesis. The structural variation of silicon nanowire particles within a composite electrode was investigated throughout an initial cycle and extended cycling. The electrochemical performance of composite electrodes containing the nanowire materials was found to depend critically on the composite electrode formulation and the electrolyte solution used. The rate performance was also observed to be influenced by the electrode formulation, suggesting the electronic and ionic conductivity of the composite electrode to be the rate limiting factors of the composite electrodes tested. Through the optimisation of composite electrode formulation and electrolyte, extended cycling at a capacity of over 600 mA h g-1(Composite) for 200 electrochemical cycles at a C-rate of C/10 was achieved, the highest number of cycles reported for SFLS silicon nanowire materials to date.
20
Kokan, Timothy Salim. "Characterizing High-Energy-Density Propellants for Space Propulsion Applications." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14626.
Анотація:
There exists wide ranging research interest in high-energy-density matter (HEDM) propellants as a potential replacement for existing industry standard fuels for liquid rocket engines. The U.S. Air Force Research Laboratory, the U.S. Army Research Lab, the NASA Marshall Space Flight Center, and the NASA Glenn Research Center each either recently concluded or currently has ongoing programs in the synthesis and development of these potential new propellants.
In order to perform conceptual designs using these new propellants, most conceptual rocket engine powerhead design tools (e.g. NPSS, ROCETS, and REDTOP-2) require several thermophysical properties of a given propellant over a wide range of temperature and pressure. These properties include enthalpy, entropy, density, viscosity, and thermal conductivity. Very little thermophysical property data exists for most of these potential new HEDM propellants. Experimental testing of these properties is both expensive and time consuming and is impractical in a conceptual vehicle design environment.
A new technique for determining these thermophysical properties of potential new rocket engine propellants is presented. The technique uses a combination of three different computational methods to determine these properties. Quantum mechanics and molecular dynamics are used to model new propellants at a molecular level in order to calculate density, enthalpy, and entropy. Additivity methods are used to calculate the kinematic viscosity and thermal conductivity of new propellants.
This new technique is validated via a series of verification experiments of HEDM compounds. Results are provided for two HEDM propellants: quadricyclane and 2-azido-N, N-dimethylethanamine (DMAZ). In each case, the new technique does a better job than the best current computational methods at accurately matching the experimental data of the HEDM compounds of interest.
A case study is provided to help quantify the vehicle level impacts of using HEDM propellants. The case study consists of the National Aeronautics and Space Administrations (NASA) Exploration Systems Architecture Study (ESAS) Lunar Surface Access Module (LSAM). The results of this study show that the use of HEDM propellants instead of hypergolic propellants can lower the gross weight of the LSAM and may be an attractive alternative to the current baseline hypergolic propellant choice.
21
Saeed, Rasha. "Design and characterisation of a high energy-density inductor." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/49726/.
Анотація:
Power electronics is an enabler for the low-carbon economy, delivering flexible and efficient control and conversion of electrical energy in support of renewable energy technologies, transport electrification and smart grids. Reduced costs, increased efficiency and high power densities are the main drivers for future power electronic systems, demanding innovation in materials, component technologies, converter architectures and control. Power electronic systems utilise semiconductor switches and energy storage devices, such as capacitors and inductors to realise their primary function of energy conversion. Presently, roughly 50% of the volume of a typical power electronic converter is taken up by the energy storage components, so reducing their weight and volume can help to reduce overall costs and increase power densities. In addition, the energy storage densities of inductors are typically much lower than those of capacitors, providing a compelling incentive to investigate techniques for improvement. The main goal of this research was to improve the design of an inductor in order to achieve higher energy densities by combining significantly increased current densities in the inductor windings with the ability to limit the temperature increase of the inductor through a highly effective cooling system. Through careful optimisation of the magnetic, electrical and thermal design a current density of 46 A/mm2 was shown to be sustainable, yielding an energy storage density of 0.537 J/ kg. A principal target for this enhanced inductor technology was to achieve a high enough energy density to enable it to be readily integrated within a power module and so take a step towards a fully-integrated “converter in package” concept. The research included the influence of the operating dc current, current ripple, airgap location and operating frequency on the inductor design and its resulting characteristics. High frequency analysis was performed using an improved equivalent circuit, allowing the physical structure of the inductor to be directly related to the circuit parameters. These studies were validated by detailed small-signal ac measurements. The large signal characteristics of the inductor were determined under conditions of triangular, high-frequency current as a function of frequency, current (flux) ripple amplitude and dc bias current (flux) and a model developed allowing the inductor losses to be predicted under typical power electronic operating conditions.
22
Palanisamy, Asha. "High Energy Density Battery for Wearable Electronics and Sensors." University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1480511507315736.
23
Cheng, Qingmei. "Materials Design toward High Performance Electrodes for Advanced Energy Storage Applications." Thesis, Boston College, 2018. http://hdl.handle.net/2345/bc-ir:108116.
Анотація:
Thesis advisor: Udayan MohantyRechargeable batteries, especially lithium ion batteries, have greatly transformed mobile electronic devices nowadays. Due to the ever-depletion of fossil fuel and the need to reduce CO2 emissions, the development of batteries needs to extend the success in small electronic devices to other fields such as electric vehicles and large-scale renewable energy storage. Li-ion batteries, however, even when fully developed, may not meet the requirements for future electric vehicles and grid-scale energy storage due to the inherent limitations related with intercalation chemistry. As such, alternative battery systems should be developed in order to meet these important future applications. This dissertation presents our successes in improving Li-O2 battery performance for electric vehicle application and integrating a redox flow battery into a photoelectrochemical cell for direct solar energy storage application. Li-O2 batteries have attracted much attention in recent years for electric vehicle application since it offers much higher gravimetric energy density than Li-ion ones. However, the development of this technology has been greatly hindered by the poor cycling performance. The key reason is the instability of carbon cathode under operation conditions. Our strategy is to protect the carbon cathode from reactive intermediates by a thin uniform layer grown by atomic layer depostion. The protected electrode significantly minimized parasitic reactions and enhanced cycling performance. Furthermore, the well-defined pore structures in our carbon electrode also enabled the fundamental studies of cathode reactions. Redox flow batteries (RFB), on the other hand, are well-suited for large-scale stationary energy storage in general, and for intermittent, renewable energy storage in particular. The efficient capture, storage and dispatch of renewable solar energy are major challenges to expand solar energy utilization. Solar rechargeable redox flow batteries (SRFBs) offer a highly promising solution by directly converting and storing solar energy in a RFB with the integration of a photoelectrochemical cell. One major challenge in this field is the low cell open-circuit potential, mainly due to the insufficient photovoltages of the photoelectrode systems. By combining two highly efficient photoelectrodes, Ta3N5 and Si (coated with GaN), we show that a high-voltage SRFB could be unassistedly photocharged and discharged with a high solar-to-chemical efficiency
Thesis (PhD) — Boston College, 2018
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
24
Tirumala, Sridhar. "Integration of Ferroelectric Materials into High Density Non-Volatile Random Access Memories." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/28800.
Анотація:
The characteristic polarization response of a ferroelectric material to an applied electric field enables a binary state device in the form of a thin film ferroelectric capacitor that can be used to store digital information. In a high density memory the capacitor is placed on the top of a poly-silicon plug which is connected to the drain of a transistor. Such a configuration poses constraints on the processing conditions of the ferroelectric capacitor in addition to the already existing reliability issues of a ferroelectric capacitor. The current research is an attempt to integrate the ferroelectric capacitor directly into a high density memory structure.
Pb1.1Zr0.53Ti0.47O₃ (PZT) and SrBi₂Ta₂O₉ (SBT) are two most promising materials for ferroelectric memory applications. PZT has excellent ferroelectric properties with wide operating temperature range. However, PZT exhibits a considerable loss of switchable polarization with cumulative switching cycles. This phenomenon is known as fatigue and is one of the critical problems affecting the life time of ferroelectric memories. In this research, Ir based electrodes are shown to improve fatigue characteristics of PZT based capacitors not only by enhancing a homogenous growth of perovskite phase of PZT but also by lowering the entrapment of oxygen vacancies at the interface. These Ir electrodes also acted as diffusion barriers for silicon, oxygen and lead. Additionally, Ir electrodes were found to be chemically stable at the processing temperatures of PZT capacitors. These features of Ir based electrodes could help in realization of a practical PZT based high density non volatile random access memories. SBT is an another promising ferroelectric material for ferroelectric memory applications. While SBT has a fatigue free nature, it has a very high processing temperature (>800 °C). Such a high processing temperature limits the choice of electrodes that could be used to integrate the ferroelectric capacitor into the high density memory structure. In this research, an attempt is made to lower the processing temperature and suitable electrodes are chosen accordingly, to enable the integration of SBT based capacitors into high density memories. Lowering the processing temperature was obtained by growing a-b oriented SBT crystallites rather than c-axis oriented crystallites. Additionally, reliability (degradation) and yield of SBT thin film capacitors was found to be correlated to the amount of segregated bismuth oxide in the films. Elimination of secondary phase bismuth oxide was found to result in dramatic improvement in the reproducibility of SBT thin films with a processing temperature close to 750 °C.
PtRh based electrodes were found to be quite suitable for integrating SBT capacitors into high density memory structures. These electrodes could withstand a processing temperature of 750 °C while preventing the interdiffusion of silicon, oxygen and bismuth. A solid solution of SBT and Bi₃TiNbO₉ (BTN) is made which reduced the processing temperature of the capacitor material from 750 °C to 650 °C while retaining the excellent fatigue and retention characteristics of SBT.Ph. D.
25
Weigand, Jan Josef. "High energy density materials based on tetrazole and nitramine compounds." Diss., lmu, 2005. http://nbn-resolving.de/urn:nbn:de:bvb:19-73576.
26
Turrell, Arthur Edward. "Processes driving non-Maxwellian distributions in high energy density plasmas." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/18083.
Анотація:
The purpose of this thesis is to explore the driving of non-Maxwellian distributions of particles in high energy density plasmas in a few select cases, with particular reference to efforts to produce a net gain in energy via inertial confinement fusion (ICF). Non-Maxwellian distributions are typically short-lived, as distributions are forced toward equilibrium by collisions, and are rarely static as a net transfer of energy must occur to sustain them. This makes non-Maxwellian distributions challenging to study with conventional approaches to plasma physics. The strategy adopted in this work to understand their evolution, and their effects, is a kinetic approach in which particles are individually accounted for. The specific cases presented are that of degenerate electrons during the heating of the cold fuel shell in hotspot ignition schemes, ion-ion inverse bremsstrahlung absorption of laser radiation, and large-angle Coulomb collisions. New computational algorithms based on the Monte Carlo technique are presented, and are capable of modelling the salient aspects of the phenomena explored. Important results which form part of this thesis include that conventional models underestimate degenerate electron temperatures long after the plasma ceases to be degenerate, that it may be possible to induce temperatures of keV in light-ion species with high power, short pulse lasers, and that consideration of large-angle collisions changes interactions in a plasma in several significant ways. Of most interest are the ability of large-angle collisions to decrease equilibration times, drive athermal tails on distribution functions, and increase the overall yield from fusion reactions relative to small-angle only simulations.
27
Österlund, Viking. "High Energy Density Lithium-Sulfur Batteries obtained using Functional Binders." Thesis, Uppsala universitet, Strukturkemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-260131.
28
Patankar, Siddharth. "High-power laser systems for driving and probing high energy density physics experiments." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/23893.
Анотація:
This thesis describes the construction of a hybrid OPCPA and Nd:Glass based laser system to provide advanced diagnostic capabilities for the MAGPIE pulsed power facility at Imperial College London. The laser system (named Cerberus) is designed to provide one short pulse 500 fs beam for proton probing and two long pulse beams, one for x-ray backlighting and one for Thomson scattering. The aim of this project is to accurately determine plasma parameters in a range of demanding experimental environments. The thesis is split into two sections; the first section provides details about the design and implementation of the laser system while the latter chapters present experimental data obtained on the MAGPIE facilty. The front end for the laser system is based on optically synchronised Optical Parametric Chirped Puled Amplification (OPCPA) which is supplemented by large aperture flashlamp pumped Nd:Glass power amplifiers in the latter stages to increase the energy to the Joule level. The use of optical parametric amplifiers (OPAs) in the pre-amplifier stages reduces gain narrowing, B-integral and improves contrast. Simulations of the dispersive optics for the Chirped Pulse Amplification (CPA) system are described in detail. Spatially resolved Thomson scattering was used to measure temperature and velocity of ablation streams in aluminium and tungsten cylindrical wire arrays. The measurements show a peak ow velocity of 120 km/s and agree well with 3D MHD simulations for the case of aluminium. There is discrepancy with the tungsten data caused by the difficulty in handling of collisionality calculations. Novel data showing the self-emission of ions from tungsten radial wire arrays is presented as a key step towards laser driven proton probing of MAGPIE. It is observed that the bulk of the emission corresponds to low energy protons with energies of ~ 100 keV. Protons with energy > 600 keV were observed to emanate from the collapsing magnetic jet using a coded aperture camera. These results offer interesting new prospects in diagnosing wire arrays.
29
Zhou, Xin Zhang Qiming. "High energy/capacitance density poly(vinylidene fluoride) based polymers for energy storage capacitor applications." [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4578/index.html.
30
Kang, Byoungwoo. "Designing materials for energy storage with high power and energy density : LiFePO₄ cathode material." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/59707.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, February 2010."February 2010." Cataloged from PDF version of thesis.
Includes bibliographical references.
LiFePO₄ has drawn a lot of attention as a cathode material in lithium rechargeable batteries because its structural and thermal stability, its inexpensive cost, and environmental friendliness meet the requirements of power sources for electric vehicles, except high power capability. Strategies to increase the rather sluggish rate performance of bulk LiFePO₄ have focused on improving electron transport in the bulk or at the surface of the material, or on reducing the path length over which the electron and Li* have to move by using nano-sized materials. However, recent evidence indicates LiFePO₄ is pure one dimensional lithium conductor. So, lithium transport is as important as electron transport. Strong anisotropic lithium diffusion results in limited transports of lithium ions in both the bulk and the surface. Reducing the particle size improves the transport of lithium ions in the bulk, and modification of the surface with a lithium-ion conducting material should enhance the transport of lithium ions on the surface. A poorly crystallized lithium phosphate phase on the surface of nanoscale LiFePO₄ is created by using proper off-stoichiometry (LiFeo.9Po.9504.3). The off-stoichiometric strategy leads to small particles less than 50 nm through grain growth restriction and a poorly crystallized lithium phosphate on the surface. The conducting surface phase can not only improve the transport of lithium ions on the surface but also facilitate the access of lithium ions to the surface by reducing anisotropic lithium diffusion on the surface induced by its amorphous nature. The off-stoichiometric material shows extremely high rate performance, achieving reasonable capacity even at 400C (9 s charge/discharge). In this thesis, the main finding is as follows: LiFePO₄ shows fast bulk kinetics and in itself does not limit the rate of charge and discharge. When bulk Li transport is very fast, the battery charging and discharging are limited by other factors such as the surface adsorption and surface transfer of lithium ions and the configuration of a cell. The off-stoichiometric strategy to improve surface transports addresses the right rate-limiting step and reveals the real capability of LiFePO₄.
by Byoungwoo Kang.
Ph.D.
31
Mecseki, Katalin. "An ultrafast optical parametric laser for driving high energy density science." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/23891.
Анотація:
This thesis describes the development of a multi-mJ, few-cycle, absolute-phase controlled laser system based on optical parametric chirped pulse amplification (OPCPA) operating at a kHz repetition rate. A laser system with these specifications will provide a table-top platform to enable a broad range of experiments in demanding research areas, including laser electron acceleration and the creation of exotic highenergy density plasmas from solid targets. The approach of the work is a combination of both experimental effort and numerical simulations used to guide and aid interpretation of laboratory studies. The non-collinear parametric gain stages of the laser have been optimised using detailed numerical simulations. A comparison is given on phase matching conditions in BBO and LBO crystals along with a novel nonlinear material BiBO. The production of 600 μJ pulses with a bandwidth that supports a transform limited temporal duration of 8.5 fs is presented in a three stage BBO based design. An all optical, low-jitter synchronisation scheme for the OPCPA pump and signal pulses has been designed and implemented by use of solitonic wavelength shifting in a photonic crystal fiber (PCF). Commercially available fibers with various core sizes have been assessed. The propagation of few-cycle pulses in the PCF has been studied by numerically solving the generalised Schrödinger equation with the splitstep Fourier method. An OPA pump laser with excellent spatial and temporal qualities has been developed. Amplification of the PCF output at 1053 nm is achieved in a regenerative diode pumped Nd:YLF amplifier and a multipass power amplifier. Self-phase modulation and gain narrowing is greatly reduced using a customised 500 μm low-finesse etalon in the regenerative amplifier cavity. Spectral modulation was found to increase both frequency doubling and parametric amplification efficiency and stability. The construction of an alternative 10 Hz, high-energy pump beam line is also presented.
32
Hare, Jack Davies. "High energy density magnetic reconnection experiments in colliding carbon plasma flows." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/49251.
Анотація:
This thesis presents a detailed study of magnetic reconnection in a quasi-two-dimensional pulsed-power driven laboratory experiment. These experiments were performed at the 1.4 MA, 240 ns rise time Magpie facility at Imperial College London. Initial experiments are presented which demonstrate the viability of carbon as a wire material, and the use of exploding wire arrays as a platform for laboratory astrophysics. In the reconnection experiments, two exploding carbon wire arrays are placed side-by-side and driven in parallel by the Magpie current pulse. The carbon wires become plasma, creating super-sonic, sub-Alfvénic flows which advect anti-parallel magnetic fields towards the mid-plane between the two arrays, where the fields mutually annihilate inside a thin current sheet. A suite of temporally and spatially resolved diagnostics are used to study the reconnection process, including optical fast-framing, laser interferometry, Faraday Rotation imaging and Thomson Scattering. These detailed measurements allow the structure and dynamics of the reconnection layer to be determined, along with the nature of the inflows and outflows and the detailed energy partition during the reconnection process. The layer is unstable, exhibiting the repeated formation and ejection of plasmoids which have an associated magnetic structure measured by magnetic probes. The number and growth rate of these plasmoids agrees well with the predictions of semi-collisional tearing instability theory, and represent the first experimental observation of plasmoids in this regime. High electron and ion temperatures are observed, far in excess of what can be attributed to classical (Spitzer--Braginskii) resistivity or viscosity. Some possible anomalous heating mechanisms are discussed, including kinetic turbulence, and the plasmoid instability. Preliminary measurements of the out-of-plane velocity and magnetic field are presented along with the outlook for future experiments.
33
Shahzad, Mohammed. "Investigating energy transport in high density plasmas using buried layer targets." Thesis, University of York, 2015. http://etheses.whiterose.ac.uk/10664/.
Анотація:
The work presented in this thesis investigates energy transport in laser irradiated solid targets containing a diagnostic buried iron layer. Energy transport in laser-plasmas is important to inertial confinement fusion and other applications, for example laser ablation, particle acceleration and x-ray production. The steep temperature and density gradients between the critical density (maximum penetration density for the laser) and ablation surface, plus the role of fast electron and radiation make energy transport in laser-plasmas a complex, non-linear issue. Laser energy can be transported into a solid target by thermal conduction, hot electron heating and radiation transport. To understand the in- terplay between these non-linear heating processes it is important to accurately characterise plasma conditions as the energy transport occurs. An experiment conducted at the Lawrence Livermore National Laboratory, USA irradiated buried iron layer targets using a 2 ps, 1017 Wcm−2 laser with the subsequent L-shell iron emission recorded using a high resolution (resolving power ≃ 500) grating spectrometer. The HYADES 1D hydrodynamic fluid code and the PrismSPECT collisional-radiative code were used to simulate the plasma conditions and the L-shell iron emission. A comparison between the simulated spectra and experi- mentally recorded L-shell emission suggests that the iron layer is heated instanta- neously by hot electrons and radiation transport and that this modifies thermal electron conduction. The thermal flux limiter and laser energy-hot electron conversion efficiency have been determined by comparing experimentally recorded L-shell emission to simulated synthetic spectra. As the iron layer expands and cools, the population of lower ionisation states increases. A novel technique has been developed to characterise the electron temperature and density from L-shell emission spectra using the Saha-Boltzmann equation and multiple line ratios of adjacent ionisation states. An experiment at the LASERIX facility, France used an extreme ultraviolet (EUV) laser as a back-lighter, to probe high density laser irradiated buried iron layer targets. The transmission through the iron layer was simulated using TOPS, PROPACEOS, IMP and HYADES opacity models. This investigation has found that higher opacities are required for plasmas at 20 eV and 0.3 gcm−3 in order to account for the drop in transmission at 20 ps after laser irradiation. Radiation transport dominates the heating of the buried iron layer when irradiated by a well defined prepulse. The expanding coronal preplasma efficiently produces hot electrons, however because of the larger stopping distance associated with ’superthermal’ electrons, the heating due to hot electrons is negligible compared to the radiation heating effect.
34
Dzelzainis, Thomas William John. "X-ray sources for the study of high energy density matter." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527690.
35
Cui, Han. "Constant-Flux Inductor with Enclosed-Winding Geometry for Improved Energy Density." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/34722.
Анотація:
The passive components such as inductors and capacitors are bulky parts on circuit boards. Researchers in academia, government, and industry have been searching for ways to improve the magnetic energy density and reduce the package size of magnetic parts. The â constant-fluxâ concept discussed herein is leveraged to achieve high magnetic-energy density by distributing the magnetic flux uniformly, leading to inductor geometries with a volume significantly lower than that of conventional products. A relatively constant flux distribution is advantageous not only from the density standpoint, but also from the thermal standpoint via the reduction of hot spots, and from the reliability standpoint via the suppression of flux crowding.
For toroidal inductors, adding concentric toroidal cells of magnetic material and distributing the windings properly can successfully make the flux density distribution uniform and thus significantly improve the power density.
Compared with a conventional toroidal inductor, the constant-flux inductor introduced herein has an enclosed-winding geometry. The winding layout inside the core is configured to distribute the magnetic flux relatively uniformly throughout the magnetic volume to obtain a higher energy density and smaller package volume than those of a conventional toroidal inductor.
Techniques to shape the core and to distribute the winding turns to form a desirable field profile is described for one class of magnetic geometries with the winding enclosed by the core. For a given set of input parameters such as the inductorâ s footprint and thickness, permeability of the magnetic material, maximum permissible magnetic flux density for the allowed core loss, and current rating, the winding geometry can be designed and optimized to achieve the highest time constant, which is the inductance divided by resistance (L/Rdc).
The design procedure is delineated for the constant-flux inductor design together with an example with three winding windows, an inductance of 1.6 µH, and a resistance of 7 mΩ. The constant-flux inductor designed has the same inductance, dc resistance, and footprint area as a commercial counterpart, but half the height.
The uniformity factor α is defined to reflect the uniformity level inside the core volume. For each given magnetic material and given volume, an optimal uniformity factor exists, which has the highest time constant. The time constant varies with the footprint area, inductor thickness, relative permeability of the magnetic material, and uniformity factor. Therefore, the objective for the constant-flux inductor design is to seek the highest possible time constant, so that the constant-flux inductor gives a higher inductance or lower resistance than commercial products of the same volume. The calculated time-constant-density of the constant-flux inductor designed is 4008 s/m3, which is more than two times larger than the 1463 s/m3 of a commercial product.
To validate the concept of constant-flux inductor, various ways of fabrication for the core and the winding were explored in the lab, including the routing process, lasing process on the core, etching technique on copper, and screen printing with silver paste. The most successful results were obtained from the routing process on both the core and the winding. The core from Micrometals has a relative permeability of around 22, and the winding is made of copper sheets 0.5 mm thick. The fabricated inductor prototype shows a significant improvement in energy density: at the same inductance and resistance, the volume of the constant-flux inductor is two times smaller than that of the commercial counterpart.
The constant-flux inductor shows great improvement in energy density and the shrinking of the total size of the inductor below that of the commercial products. Reducing the volume of the magnetic component is beneficial to most power. The study of the constant-flux inductor is currently focused on the dc analysis, and the ac analysis is the next step in the research.Master of Science
36
Zhang, Shuyuan. "AN ORGANIC IRON CATHOLYTE FOR A HIGH-ENERGY-DENSITY REDOX FLOW BATTERY." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1619646976982945.
37
Fischer, Dennis [Verfasser], and Thomas M. [Akademischer Betreuer] Klapötke. "High performing and nitrogen-rich high energy density materials / Dennis Fischer ; Betreuer: Thomas M. Klapötke." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/1155407849/34.
38
Bewlay, Stephen L. "Synthesis of novel high energy density cathode materials for lithium rechargeable batteries." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060731.161531/index.html.
39
Zhou, Yingying. "Design Principles for High Energy Density Cathode Materials Using Anionic Redox Activity." Kyoto University, 2020. http://hdl.handle.net/2433/253384.
Анотація:
Kyoto University (京都大学)0048
新制・課程博士
博士(人間・環境学)
甲第22548号
人博第951号
新制||人||226(附属図書館)
2019||人博||951(吉田南総合図書館)
京都大学大学院人間・環境学研究科相関環境学専攻
(主査)教授 内本 喜晴, 教授 田部 勢津久, 准教授 藤原 直樹
学位規則第4条第1項該当
40
Sladkov, Andrey. "Numerical modeling of magnetic reconnection in laser-induced high energy density plasmas." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS376.
Анотація:
Cette thèse est une étude numérique de la reconnexion magnétique dans les plasmas sans collision à l’aide d’un code cinétique. On peut étudier le processus de reconnexion magnétique lors d'expérience pour lesquels le plasma est créé par interaction d’un laser de puissance sur une cible solide. Durant cette thèse, nous avons inclus dans le code HECKLE les éléments permettant de rendre ces simulations plus réalistes pour les conditions lasers: les effets du tenseur complet des électrons ainsi que l’expansion super-Alfvénique du plasma. Nous avons ainsi mis en évidence le rôle du tenseur de pression pour réduire l’efficacité de la reconnexion, ainsi que les effets de température du plasma la rendant plus impulsionnelleThis thesis is a numerical study of the magnetic reconnection in collisionless plasmas using a kinetic code. We can study the magnetic reconnection process during experiments for which the plasma is created by interaction of a power laser on a solid target. During this thesis, we included in the HECKLE code the elements allowing to make these simulations more realistic for the laser conditions: the effects of the electron six-component pressure tensor as well as the super-Alfvénic expansion of the plasma. We have thus highlighted the role of the pressure tensor to reduce the efficiency of the reconnection, as well as the plasma temperature effects making it more impulsive
41
Doyle, Hugo William. "Creating and probing warm dense matter and high energy density blast waves." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9470.
Анотація:
Non-ideal plasmas are difficult to model numerically and achieve experimentally. Here I focus on reaching the warm dense matter (WDM) regime at one end of the energy scale and the high energy density (HED) regime at the other. Both regimes access common, yet hard to observe, features in planetary core physics and astrophysics respectively. We have implemented several experiments developing both ionic, isochoric heating of matter to HED states, and probing the release isentrope through the WDM regime. Using sub-picosecond, ~ 100 J laser pulses, ion beams were produced in a thin foil interaction and then used to rapidly and uniformly heat ~ 20 µm wires to ~15 eV temperatures before hydrodynamic expansion could occur. Thus the partially ionised, strongly coupled WDM regime was accessed and then explored using streaked XUV and UV imaging of the expansion into vacuum, together with measurement of the ion spectra deposited in the sample. The calibrated ion spectra indicates the energy deposition occurs over ~ 400 ps and as such further investigation of the stopping power of warm dense matter is required. The high absorption of these laser pulses in cluster gases (> 90%) was used to create HED blast waves. Under hydrodynamic scaling laws these blast waves can be used to model processes occurring within astrophysical phenomena. Schlieren, interferometry and ion probing methods have been used to spatially and temporally resolve the blast wave profiles. We describe high energy scaling experiments in the search for the thermal cooling instability, in which radiation from the blast wave modi es both its density profile and propagation dynamics. A unique perpendicular, time delayed colliding blast wave geometry has been used to identify up-stream characteristics of the front propagation and to pre-heat material leading to shock front acceleration. We show that ions of an energy greater than ~ 200 keV are required to probe the transient electromagnetic fields believed to occur at the shock front. The development and characterisation of low energy (0.1 - 10 MeV) proton beams was necessary for studies of both non-ideal plasma regimes, particularly for probing high density media and transient electromagnetic fields. The application of ions to recover stopping power is discussed for WDM and HED plasmas.
42
Maliehe, Nkhatamele B. "Density of states in finite normal-superconducting structures." Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298736.
43
Zhang, Yuhan. "POLYMER ELECTROLYTES FOR HIGH CURRENT DENSITY LITHIUM STRIPPING/PLATING TEST." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555090752890092.
44
Wang, Ruxi. "High Power Density and High Temperature Converter Design for Transportation Applications." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/28264.
Анотація:
The continual development of high-power-density power electronic converters is driven particularly by modern transportation applications like electrical vehicles and more electric aircraft where the space and carrier capability is limited. However, there are several challenges related to transportation applications such as fault tolerance for safety concern, high temperature operation in extreme environments and more strict electromagnetic compatibility requirement. These challenges will increase difficulties for more electrical system adoption in the transportation applications.
In this dissertation, comprehensive methodologies including more efficient energy storage solution, better power electronics devices capability, better packaging performance and more compact EMI filter design are analyzed and proposed for the goal of high power density converter design in transportation applications.Ph. D.
45
Patil, Sandeep Kesharsingh. "Modeling and simulations of diphasic composites for development of high energy density dielectrics." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Patil_09007dcc804e35ca.pdf.
Анотація:
Thesis (Ph. D.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 21, 2008) Includes bibliographical references.
46
Eagle, Walter Ethan. "Modeling of a high energy density combustion based aluminum and steam propulsion system." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7813.
Анотація:
Thesis (M.S.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Manuel, Mario John-Errol. "Characterization of mono-energetic charged-particle radiography for high energy density physics experiments." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45302.
Анотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2008.Includes bibliographical references (p. 75-76).
Charged-particle radiography, specifically protons and alphas, has recently been used to image various High-Energy-Density Physics objects of interest, including Inertial Confinement Fusion capsules during their implosions, Laser-Plasma Interactions, and Rayleigh-Taylorinstability growth. An imploded D23He-filled glass capsule - the backlighter - provides monoenergetic 15-MeV and 3-MeV protons and 3.6-MeV alphas for radiographing these various phenomena. Because the backlighter emits mono-energetic particles, information about areal density and electromagnetic fields in imaged systems can be obtained simultaneously. One of the most important characteristics of the backlighter is the fusion product yield, so understanding the experiment parameters that affect it is essential to the future of chargedparticle radiography. Empirical studies of backlighter performance under a variety of conditions are presented, along with proton yield parameterizations based on backlighter and laser parameters. In order to investigate the limits and capabilities of this diagnostic, the Geant4 Transport Toolkit is introduced as the supplementary simulation tool to accompany this novel diagnostic; benchmark simulations with experimental data are presented.
by Mario John-Errol Manuel.
S.M.
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Samant, Saumil. "Directed Self-Assembly of Block Copolymers for High Energy Density Polymer Film Capacitors." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1468449545.
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Goh, Ai Tee. "Courtyard housing in the UK : Potentials for high density-low energy urban housing." Thesis, University of Liverpool, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526861.
Анотація:
The Garden City Movement has been a trigger for the design development of the courtyard house for the working class single family in Northern Europe in the late-1920s. This house form was experimented with in the UK for three decades since the late-1950s, and has since been neglected as only few architects have explored its contemporary relevance. This research seeks to investigate the potential of reinterpreting the contemporary courtyard house for creating an urban housing that can adapt to the changing needs of its dwellers over time in the UK. Four main research problems have been identified: the lack of a comprehensive study of the courtyard house type in the UK; a mismatch between the kinds of house needed by a family throughout their life course and the house provided by the market; a paucity of knowledge regarding the concept for housing mobility; and the biased observations on the sustainability (thermal performance) of this house form in the UK. A holistic approach was used in this thesis to ensure that a greater insight can be developed in examining the potentials of courtyard housing in providing low rise high density and low energy housing in the UK. The research began with a literature review followed by a combination of different research method techniques such as content analysis, ordinance survey mastermap analysis and overt non-participant field observations to collect information about the contemporary courtyard house schemes in the UK. A post occupancy evaluation (POE) study was then carried out on three carefully selected recently completed courtyard housing schemes in the UK. A postal questionnaire survey, in-depth semi-structured face-to-face interviews and overt non-participant observation techniques were adopted to examine users' perceptions of the performance of this house according to a number of selected criteria. Next, the cross tabulations and logistic regression analysis techniques on data of censuses obtained from the Office for National Statistics Longitudinal Study (LS) were carried out to establish if there is any evidence to support the argument that design (housing and environmental) factors rather than economic ones influenced individuals' housing mobility. Finally, Ecotect, the thermal performance analysis tool was used to evaluate the thermal performance for different house forms in the UK. The tool was then used to investigate the best thermally performing courtyard house configuration in the UK. Furthermore, the case studies technique was adopted to examine architectural and environmental design strategies and approaches to design towards zero energy for space heating in a home. There are four key contributions in this research. Firstly, a systematic survey of courtyard housing schemes designed and/ or developed in the UK from 1950s to the present day was completed with the aim to provide a comprehensive database for designers, planners and policy makers. Secondly, the results from POE studies of three recently completed courtyard house schemes in the UK, show that the `Home' received the highest level of satisfaction in all cases. The evidence collected through the POE studies suggest that the courtyard house type (when it is well designed) is well suited for creating a contemporary family house in an urban area. Thirdly, the empirical evidence from the housing mobility study seem to suggest that design (housing and environment) constitutes one of the most important variable influencing individuals' housing mobility in the England and Wales. The best model to predict `house move' made by individuals between 1991 and 2001 Censuses in the England and Wales is a combination of variables from design/ environmental (accommodation type, population density and number of rooms in house), social (age, household type and number of person in house) and economic (social class). Last but not least, this study establishes that the long-narrow with the internal court configuration performed (thermally) better than L-, I-, Z- and T-shaped courtyard house. Careful planning and layout may improve its thermal performance to reach results that are better than terraced house. Additionally, nine architectural design principles were recommended to ensure low energy consumption for residential buildings in the UK.
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Dinca, Dragos. "Development of an Integrated High Energy Density Capture and Storage System for Ultrafast Supply/Extended Energy Consumption Applications." Cleveland State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=csu1495115874616384.