8,149 research outputs found

    Graduate Catalog of Studies, 2023-2024

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    Positive electrode materials for high energy rechargeable batteries

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    With the growth of environmental concerns, rechargeable batteries – lithium ion batteries (LIBs) and sodium ion batteries (SIBs) - have been employed in a large number of different applications. To meet the market needs in terms of their performance, positive electrode materials with high energy density are in high demand. The aim of this thesis work is to provide strategies which enhance electrochemical performance of LiCoPO₄ as a high voltage positive electrode material for LIBs (chapter 3 and chapter 4) and an insight into the mechanism which triggers oxygen redox activity of P3-type Na₀.₆₇M₀.₂Mn₀.₈O₂ (M= Mg and Ni in chapter 5 and 6, respectively) as potential candidates for high capacity positive electrode materials in SIBs. Studies on the improvement of cyclability of LiCoPO₄ were carried out using aqueous binders, of which, sodium carboxymethyl cellulose (CMC) permits more stable cycling performance and better rate capability with respect to the conventional organic solvent-soluble binders. In addition, substitution of magnesium for cobalt was investigated, which demonstrates that doping with magnesium can be one of the solutions to obtain stable capacity on extended cycling. Both P3-type Na₀.₆₇Mg₀.₂Mn₀.₈O₂ and Na₀.₆Ni₀.₂Mn₀.₈O₂ were synthesised by a co-precipitation method and studied to understand the origin of abnormal capacity on the first charge. Careful electrochemical and structural characterisation combined with bulk and surface spectroscopic techniques (XAS, XPS) reveal the oxygen redox activity in Na0.67Mg0.2Mn0.8O2. As a consequence of vacancies in the transition metal layers of Na₀.₆₇Mg₀.₂Mn₀.₈O₂ prepared under oxygen, reversible oxygen redox is enhanced. Subsequently, substitution of nickel for manganese was carried out to increase capacity using the Ni²⁺/Ni⁴⁺ redox couple of nickel. The presence of oxygen redox activity in Na₀.₆Ni₀.₂Mn₀.₈O₂ is also demonstrated by using a range of spectroscopic techniques (XAS, SXAS, RIXS), which is stabilised by reduction of nickel through the reductive coupling mechanism

    Radiation-directed production of chemical reagents and petroleum additives from waste organic feedstocks

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    Nuclear cogeneration is the collation of co-processes that aims to improve the sustainability, overall efficiency, and profitability of nuclear power by producing alternative products alongside electricity. A range of existing cogeneration processes explores the use of waste stream process heat for a variety of processes including district heating and desalination. However, the direct application of under-utilized ionization energy has yet to be fully realized. This thesis is a study on the potential application of ionizing radiation from nuclear facilities towards the radiolytic production of organic chemicals derived from waste renewable feedstocks. Here we show that glycerol, a notable waste feedstock from biodiesel production can be converted into acetol (hydroxyacetone) or solketal which are textile and biofuel additives, respectively using ionizing radiation from a 250-kW research fission reactor. The radical-initiated chain reaction for hydroxyl acetone (acetol) production is optimised to produce the highest G value (2.7 ± 0.4 µmol J−1) and mass productivity (~1 %) to be reported in the available radiolysis literature. A previously unreported radiolytic product, solketal, which is a valuable biofuel additive is produced radiolytically using ternary glycerol, acetone, and water mixtures with G-values of 1.5 ± 0.2 µmol J−1 at 50 kGy. Empirical data showed a preference for low LET, low dose rate, γ-ray emissions such as those from spent fuel was found to be favourable for acetol and solketal production. Simulating three production scenarios with MCNP models for preferential solketal production found that a spent fuel facility consisting of ~1710 elements showed the largest production capacity at 57.4 ± 5.6 t year−1 due to the high volume available to be irradiated. Extrapolating to a theoretical European production network involving ~180 equivalent SFP facilities based on relative reactor power, a total of (1.3 ± 0.1) × 104 t year−1 of solketal could be produced, contributing to (2.5 ± 0.2) × 108 litres year−1 to a (95% petroleum, 5% solketal) fuel blend. While this represents only ~0.3 % of total transport fuels consumed within the EU, it presents a pioneering process that could be feasible if G-values and mass productivities were improved upon

    Synthesis of modified lithium iron phosphate and its electrochemical properties

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    Abstract. Lithium-ion batteries (LIBs) are used to power portable electronic devices and electric vehicles (EVs). Cobalt has been an essential element on popular cathode active materials of LIBs since the commercialization of LiCoO2 (LCO) by Sony in 1991. However, most cobalt reserves and processing facilities are in Democratic Republic of Congo (DRC) and China. This creates geopolitical risks and restricts supply expansion. On top of that, child labour is used to mine cobalt in DRC. Consequently, cobalt free and low-cobalt materials should be and are developed and used for commercial applications. One of the common cobalt free materials used today is lithium iron phosphate, also known as LiFePO4 (LFP). LFP was identified as a cathode material for LIBs by Padhi, Nanjundaswamy, and Goodenough in 1997. Main advantages of LFP are its flat voltage profile, low cost, abundant material supply, environmental friendliness (nontoxic and cobalt free), and thermal stability. The downsides include relatively low theoretical capacity, low energy density, low electronic conductivity, and low ionic diffusivity. This study focuses on synthesis of modified LFP and its electrochemical properties. Common and novel synthesis methods are reviewed shortly. Especially, performance increasing modifications are reviewed. These include coating, control of particle size and particle morphology, and doping in which ions are used to replace atoms in LFP. Effects of the modifications are discussed through the paper with most time spent on doping and comparison of the effects induced by doping with different elements. In the end the dopants are ranked according to their effects on performance, price, and sustainability of a battery. To understand the modifications and their effect on electrochemical performance the structure of the material must be studied and understood. Because of this a chapter to crystallography and structure of LFP is included. Similarly, some basic information about common electrochemical characterization techniques is included to help the reader understand the plots and values produced by them. These include cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), electrode setups, and terminology

    Beam scanning by liquid-crystal biasing in a modified SIW structure

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    A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

    Systemic Circular Economy Solutions for Fiber Reinforced Composites

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    This open access book provides an overview of the work undertaken within the FiberEUse project, which developed solutions enhancing the profitability of composite recycling and reuse in value-added products, with a cross-sectorial approach. Glass and carbon fiber reinforced polymers, or composites, are increasingly used as structural materials in many manufacturing sectors like transport, constructions and energy due to their better lightweight and corrosion resistance compared to metals. However, composite recycling is still a challenge since no significant added value in the recycling and reprocessing of composites is demonstrated. FiberEUse developed innovative solutions and business models towards sustainable Circular Economy solutions for post-use composite-made products. Three strategies are presented, namely mechanical recycling of short fibers, thermal recycling of long fibers and modular car parts design for sustainable disassembly and remanufacturing. The validation of the FiberEUse approach within eight industrial demonstrators shows the potentials towards new Circular Economy value-chains for composite materials

    Organic-Inorganic Nanomaterial Based Highly Efficient Flexible Nanogenerator for Self-Powered Wireless Electronics

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    As the world progresses towards artificial intelligence and the Internet of Things (IoT), self‐powered sensor systems are increasingly vital for sensing and detection. Nanogenerators, a new technology in energy research, enable the harvesting of normally wasted energy from the environment. This technology scavenges a wide range of ambient energies, meeting the ever-expanding energy demands as conventional fossil fuel sources are depleted. This research involves designing and fabricating high-performance flexible piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs), using novel organic-inorganic hybrid nanomaterials for wireless electronics. Structural health monitoring (SHM) is crucial in the aerospace industry to enhance aircraft safety and consistency through reliable sensor networks. PENGs are promising for powering wireless sensor networks in aerospace SHM applications due to their sustainability, durability, flexibility, high performance, and superior reliability. This research demonstrated a self-powered wireless sensing system based on a porous PVDF (polyvinylidene fluoride)-based PENG, which is ideal for developing auto-operated sensor networks. The porous PVDF film-based PENG, enhanced output current by ~ 11 times and output voltage by ~ 8 times, respectively, compared to a pure PVDF-based PENG. The PENG device generated sufficient electrical energy to power a customized wireless sensing and communication unit and transfer sensor data every ~ 4 minutes. This PENG could harness energy from automobile vibration, reflecting the potential for real-life SHM systems. Subsequently, a novel, self-assembled, highly porous perovskite (FAPbBr2I)/polymer (PVDF) composite film was designed and developed to fabricate high-performance piezoelectric nanogenerators (PENGs). The porous structure enlarged the bulk strain of the piezoelectric composite film, resulting in a 5-fold enhancement of the strain-induced piezo potential and a 15-fold amplification of the output current. This highly-efficient PENG achieved a peak output power density of 10 µW/cm2 and enabled to run a self-powered integrated wireless electronic node (SIWEN). The PENG was applied to real-life scenarios including wireless data communication, efficient energy harvesting from automobile vibrations as well as biomechanical motion. This low-temperature, full-solution synthesis approach could lead to a paradigm shift in sustainable power sources, expanding the realms of flexible PENGs. One of the remaining concerns is the highly soluble lead component, which is one of the constituents of the PENGs that poses potential adversary impacts on human health and the environment. To address this concern, lead-free organic-inorganic hybrid perovskite (OIHP) based flexible piezoelectric nanogenerators (PENGs) have been developed. The excellent piezoelectric properties of the FASnBr3 NPs was demonstrated with a high piezoelectric charge coefficient (d33) of ~ 50 pm/V through piezoelectric force microscopy (PFM) measurements. The device’s outstanding flexibility and uniform distribution properties resulted in a maximum piezoelectric peak-to-peak output voltage of 94.5 V, peak-to-peak current of 19.1 μA, and output power density of 18.95 μW/cm2 with a small force of 4.2 N, outperforming many state-of-the-art halide perovskite-based PENGs. For the first time, a self-powered RF wireless communication between smartphones and a nanogenerator solely based on a lead-free PENG was demonstrated and serves as a stepping-stone towards achieving self-powered Internet of Things (IoT) devices using environment-friendly perovskite piezoelectric materials. Likewise, triboelectric nanogenerators (TENGs) are also promising energy-harvesting devices for powering the next generation of wireless electronics. TENGs’ performance relies on the triboelectric effect between the tribonegative and tribopositive layers. In this study, a natural wood-derived lignocellulosic nanofibrils (LCNF) tribolayer was reported to have high tribonegativity (higher than polytetrafluoroethylene (PTFE)) due to the presence of natural lignin on its surface and its nanofibril morphology. LCNF nanopaper-based TENGs produced significantly higher voltage (160%) and current (120%) output than TENGs with PTFE as the tribonegative material. Assembling LCNF nanopaper into a cascade TENG generated sufficient output to power a wireless communication node to send a radio-frequency signal to a smartphone every 3 mins. This study demonstrates the potential of using LCNF as a more environmentally friendly alternative to conventional tribonegative materials based on fluorine-containing petroleum-based polymers. Overall, this thesis explores the design and development of highly efficient and flexible nanogenerators for self-powered wireless electronics. By combining highly electroactive nanomaterials with flexible polymer matrix structures, NGs with high electric output performance and flexibility were successfully obtained. The synthesizing process for the electroactive nanomaterials was carefully designed and adopted to sustain the inherent advantages of flexible electronics. The various type of high performance flexible NGs developed in this research work, including ZnO/PVDF porous PENGs, FAPbBr2I/PVDF based PENGs, FASnBr3/PDMS based PENGs, and LCNF nanopaper-based TENGs, provide promising solutions for energy harvesting and self-powered sensing

    Sensing Collectives: Aesthetic and Political Practices Intertwined

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    Are aesthetics and politics really two different things? The book takes a new look at how they intertwine, by turning from theory to practice. Case studies trace how sensory experiences are created and how collective interests are shaped. They investigate how aesthetics and politics are entangled, both in building and disrupting collective orders, in governance and innovation. This ranges from populist rallies and artistic activism over alternative lifestyles and consumer culture to corporate PR and governmental policies. Authors are academics and artists. The result is a new mapping of the intermingling and co-constitution of aesthetics and politics in engagements with collective orders

    Precision mass measurements for the astrophysical rp-process and electron cooling of trapped ions

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    Precision mass measurements of rare isotopes with decay half-lives far below one second are of importance to a variety of applications including studies of nuclear structure and nuclear astrophysics as well as tests of fundamental symmetries. The first part of this thesis discusses mass measurements of neutron-deficient gallium isotopes in direct vicinity of the proton drip line. The reported measurements of 60-63Ga were performed with the MR-TOF-MS of TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN) in Vancouver, Canada. The measurements mark the first direct mass determination of 60Ga and yield a 61Ga mass value three times more precise than the literature value from AME2020. Our 60Ga mass value constrains the location of the proton dripline in the gallium isotope chain and extends the experimentally evaluated IMME for isospin triplets up to A=60. The improved precision of the 61Ga mass has important implications for the astrophysical rapid proton capture process (rp-process). Calculations in a single-zone model demonstrate that the improved mass data substantially reduces uncertainties in the predicted light curves of Type I X-ray bursts. TITAN has demonstrated that charge breeding provides a powerful means to increase the precision and resolving power of Penning trap mass measurements of radioactive ions. However, the charge breeding process deteriorates the ion beam quality, thus mitigating the benefits associated with Penning trap mass spectrometry of highly charged ions (HCI). As a potential remedy for the beam quality loss, a cooler Penning trap has been developed in order to investigate the prospects of electron cooling the HCI prior to the mass measurement. The second part of this thesis reports exploratory studies of electron cooling of singly charged ions in this cooler Penning trap. Comparison of measured ion energy evolutions to a cooling model provides a detailed understanding of the underlying cooling dynamics. Extrapolation of the model enables the deduction of tentative estimates of the expected cooling times for radioactive HCI
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