This dissertation presents the synthesis and characterization of new types of nanostructured materials for use in high-performance aqueous rechargeable batteries and supercapacitors. In the first chapter, nanostructured nickel cobalt sulfide (Ni4.5Co4.5S8) was prepared through pulse-electrodeposition method. In addition, iron oxide nanosheets were prepared from graphite-coated iron carbide/α-Fe in a two-step annealing/electrochemical cycling process. A full-cell battery with supercapacitor-like power behavior was assembled with Ni4.5Co4.5S8 and iron oxide nanosheets as the positive and negative electrodes, respectively. The full-cell device delivers a specific energy of 89 Wh kg−1 at 1.1 kW kg−1 with a rate performance of 61 Wh kg−1 at a very high specific power of 38.5 kW kg−1. In the second chapter, we propose a route towards developing asymmetric supercapacitor devices having high volumetric energy densities though the modification of commercially available current collectors (CCs): nickel foam (NF) and carbon fiber cloth (CFC). A soft templating/solvothermal treatment route was employed to generate NiO/NiOOH nanosheets on NF current collectors (as positive electrode). CFCs were also modified via an electrochemical oxidation/reduction route to generate an exfoliated core-shell structure followed by electropolymerization of pyrrole into the shell structure (as negative electrode). Combining the individual materials resulted in a full-device asymmetric supercapacitor that delivers volumetric energy densities in the range of 1.67-2.65 mWh cm−3 with corresponding power densities in the range of 5.9-273.6 mW cm−3. Such performance is comparable to lithium thin film (0.3-10 mWh cm−3) and better than some commercial supercapacitors (< 1 mWh cm−3). In the third chapter, we established a simple, precise, and reproducible method to construct carbon fiber ultramicroelectrodes (CF-UMEs) with tip radius r < 1 μm. CF-UMEs were successfully used as SECM-tips to examine the “crystal structure orientation-OER electrocatalytic activity” relationship of iridium/iridium oxide catalysts. In addition, CF-UMEs were used as a substrate electrode for the electrodeposition of pH-sensitive iridium oxide. The pH response of these micrometer-sized pH electrodes has a rapid response (< 5 s) over the pH range of 2-12 with a super-Nernstian slope of 65.3 mV/pH. The prepared pH-UMEs were successfully employed as a potentiometric SECM-tip to image the pH changes at different substrates.

No description available.

No description available.

In this work we propose two techniques for symmetric multiple description coding with reduced storage space decoder. The first technique is multiple description scalar quantizer with linear joint de-coders. We propose an optimal design algorithm similar to Vaishampayan's algo-rithm, to which we add an index assignment optimization step. We also solve an additional challenge in the decoder optimization, by proving that the problem is a convex quadratic optimization problem with a closed form solution (under some mild conditions). Our tests show that the new method has very good performance when the probability of description loss is sufficiently low. The other technique is an improvement to the traditional multiple description coding scheme based on uneven erasure protection. We evaluate the asymptotical performance of both schemes for a Gaussian memoryless source. The analysis reveals that the improvement reaches over 1 dB for up to ten descriptions and low probability of description loss. From our experiments we observe that the improved scheme is very competitive comparing to other multiple description techniques as well. / Thesis / Master of Applied Science (MASc)

In a world that relies heavily on electricity and portable energy, the development of high performing energy storage devices is crucial. The ongoing push for energy storage devices such as batteries and supercapacitors to store more energy and charge/discharge faster has become exponentially stronger over the past decade. In order to meet the high demands, new materials and processing techniques must be developed. A particle extraction through the liquid-liquid interface (PELLI) technique was used with a versatile extracting molecule, Octyl Gallate (OG). It was found that OG was able to extract a variety of materials including oxides, oxyhydroxides, and pure silver. The advantage of PELLI is that it circumvents the drying stage that occurs in many electrode synthesis techniques where metal oxides are synthesized in aqueous then dried and mixed with conductive additives dispersed in organic solvent. This drying stage causes a practically irreversible agglomeration which hinders mixing with conductive additives as well as reduces the surface area of the material, limiting its electrochemical performance. Using hydroxamates such as octanohydroxamic acid and bufexamac, a novel PELLI technique was developed based on the use of OHA as an extracting agent as well as a capping agent. In addition, a preliminary investigation was started on advanced negative electrode material for supercapacitors. FeOOH-based electrodes exhibit high capacitance but low cyclic stability. Zn2+ ions were introduced during synthesis forming a doped Zn/FeOOH electrode which showed a significant increase in cyclic stability. / Thesis / Master of Applied Science (MASc)

The expanding use of renewable and sustainable energy systems is at the forefront of the global effort to reduce CO2 emissions and mitigate climate change. Thermal energy storage has become a critical component of many of these new and innovative systems, and research in this field has expanded to meet their requirements. Water has been traditionally used as a storage medium because of its high heat capacity and low cost, but depending on the application, the storage volume requirements may be excessively large. Phase Change Materials (PCMs) offer an opportunity to reduce the storage volume through latent energy storage. However, energy storage in PCM presents new challenges, and careful design of thermal storage is required to realize the benefits. The design of PCM storage must consider the system operation, operating temperature range, PCM properties, encapsulation, and the heat transfer fluid. In the current state-of-the-art literature, there is no standard method for designing PCM thermal storage based on system requirements. The objective of this thesis is to deliver a methodology to assess the feasibility of using PCM for thermal energy storage in place of water. This is done by identifying which applications benefit from PCM, comparing the analytical and numerical performance of water-only to hybrid water-PCM storage, and developing a method to size PCM containment to achieve theoretical performance when PCM is beneficial. This research study develops analytical solutions for sizing PCM thermal energy storage based on system boundary conditions. These boundary conditions consist of the system itself (e.g. heat pump, absorption chiller), the energy source into the system, and the required load from the system (e.g. a building). The PCM is incorporated into a water tank such that the water acts as both a heat transfer fluid and an energy store. Analytical predictions of the total energy storage capacity in this hybrid water-PCM thermal storage unit are coupled to analytical predictions of the rate of melting and solidification to appropriately determine the required volume and encapsulation thickness of PCM thermal storage based on the system requirements. The results are verified against full-system numerical simulations based on case studies of solar absorption cooling and heat-pump heating. It is shown in this study that the total required volume of storage is a function of the temperature differential of the system, and the total mismatch in time between when energy is available and when it is required. A mathematical formulation is proposed which quantifies the required storage volume based on the temperature differential, the source and load profiles, and the percentage of PCM in the hybrid water-PCM storage unit. Furthermore, the rate of melting and solidification of the thermal storage is coupled to the overall storage size and required time for charging, and a mathematical formulation is proposed which solves for the PCM encapsulation thickness. The method assumes a conservative conduction-dominated domain and demonstrates how complete melting can be ensured before the system reaches its maximum allowable temperature. The map the region of applicability of PCM thermal storage is also presented which is defined in terms of the non-dimensional Biot and Stefan numbers, in which systems utilizing PCM thermal storage will benefit from volume reduction when compared to using water only. This region is characterized with a low Biot number, corresponding to a slender geometry acting as a lumped system, as well as a low Stefan number, corresponding to limited temperature differential and limited sensible energy storage. These characteristics favor the use of PCM thermal storage instead of water only. This thesis presents a novel contribution to the state-of-the-art literature in PCM thermal storage, which is established through the analytical methodology for sizing PCM thermal storage based on system boundary conditions. The details of the contribution are presented in the form of three journal publications that have been integrated into this sandwich Ph.D. thesis on PCM thermal energy storage. / Thesis / Candidate in Philosophy

No description available.

No description available.

Les applications modernes ont des tendances de diverger à la fois le profile I/O et les requiers du stockage. La liaison d'une application scientifique ou commerciale avec un system "general-purpose" produit probablement un résultât sous-optimale. Même sous la présence des systèmes "purpose specific" des application aux classes multiples de workloads ont encore besoin de distribuer du travail de calcul au correct system. Cependant, cette stratégie n'est pas triviale comme des plateformes différentes butent diversifier leur propos et par conséquence elles requièrent que l'application intégrée des chemins multiples de code. Le but de l'implémentation de ces chemins n'est pas trivial, il requiert beaucoup d'effort et des capacités de codage. Le problème devient vaste quand les applications ont besoin de bénéficier de plusieurs data-stores en parallèle. Dans cette dissertation, on va introduire les "storage containers" comme le prochain étape logique, mais révolutionnaire. Un "storage container" est une infrastructure virtuelle qui découple une application de ses data-stores correspondants avec la même manière que Docker découple l'application runtime des servers physiques. En particulier, un "storage container" est un middleware qui sépare des changements fait pour bouts de code des application par des utilisateurs scientifiques, de celui fait pour des actions de I/O par des développeurs ou des administrateurs.Pour faciliter le développement et déploiement d'un "storage container" on va introduire un cadre appelé Tromos. Parmi son filtre, tout qui est nécessaire pour qu'un architecte d'une application construite une solution de stockage est de modéliser l'environnement voulu dans un fichier de définition and laisser le reste au logiciel. Tromos est livré avec un dépôt de plugins parmi les quelles l'architecte peut choisir d'optimiser le conteneur pour l'application activée. Parmi des options disponibles, sont inclus des transformations des données, des politiques de placement des données, des méthodes de reconstruction des données, du management d'espace de noms, et de la gestion de la cohérence à la demande. Comme preuve de concept, on utilisera Tromos pour créer des environnements de stockage personnalisés facilement comparés à Gluster, un système de stockage bien établi et polyvalent. Les résultats vous montrent que les "storage containers" adaptés aux applications, même s'ils sont auto-produits, peuvent surpasser les systèmes "general purpose" les plus sophistiqués en supprimant simplement la surcharge inutile de fonctionnalités factices. / Modern applications tend to diverge both in the I/O profile and storage requirements. Matching a scientific or commercial application with a general-purpose system will most likely yield suboptimal performance. Even in the presence of purpose-specific' systems, applications with multiple classes of workloads are still in need to disseminate the workload to the right system. This strategy, however, is not trivial as different platforms aim at diversified goals and therefore require the application to incorporate multiple codepaths. Implementing such codepaths is non-trivial, requires a lot of effort and programming skills, and is error-prone. The hurdles are getting worse when applications need to leverage multiple data-stores in parallel. In this dissertation, we introduce "storage containers" as the next logical in the storage evolution. A "storage container" is virtual infrastructure that decouples the application from the underlying data-stores in the same way Docker decouples the application runtime from the physical servers. In other words, it is middleware that separate changes made to application codes by science users from changes made to I/O actions by developers or administrators.To facilitate the development and deployment of a "storage container" we introduce a framework called Tromos. Through its lens, all that it takes for an application architect to spin-up a custom storage solution is to model the target environment into a definition file and let the framework handles the rest. Tromos comes with a repository of plugins which the architect can choose as to optimize the container for the application at hand. Available options include data transformations, data placement policies, data reconstruction methods, namespace management, and on-demand consistency handling.As a proof-of-concept we use Tromos to prototype customized storage environments which we compare against Gluster; a well-estalished and versatile storage system. The results have shown that application-tailored "storage containers", even if they are auto-produced, can outperform more mature "general-purpose" systems by merely removing the unnecessary overhead of unused features.

Typescript. / Digitized by Kansas Correctional Industries