Control of single-walled carbon nanotube dispersion properties is of substantial interest to the scientific community. In this work, we sought to investigate the effect of a macrocycle, the pillar[5]arene, on the dispersion properties of a polymer-nanotube complex. Pillar[5]arenes are a class of electron-rich macrocyclic hosts capable of forming inclusion complexes with electron-poor guests, such as alkyl nitriles. A hydroxyl-functionalized pillar[5]arene derivative was coupled to the alkyl bromide side-chains of a polyfluorene, which was then used to coat the surface of single-walled carbon nanotubes. Differentiation of semiconducting and metallic SWNT species was analyzed by a combination of UV-Vis-NIR, Raman, and fluorescence spectroscopy. Raman spectroscopy confirmed that the concentrated nanotube dispersion produced by the macrocycle-containing polymer was due to well-exfoliated nanotubes, rather than bundle formation. The polymer-nanotube dispersion was investigated using 1H-NMR spectroscopy, and it was found that host-guest chemistry between pillar[5]arene and 1,6-dicyanohexane occurred in the presence of the polymer-nanotube complex. Utilizing the host-guest capability of pillar[5]arene, the polymer-nanotube complex was incorporated into a supramolecular organogel. / Thesis / Master of Science (MSc)

The laws of classical mechanics show that mechanical properties are independent of sample sizes. However, based on extensive theoretical work and experimentation, it is believed that reducing the size of materials to the submicron scale can result in different mechanical properties than those found in bulk quantities. This size effect was explained by the strain gradient. Atomic simulations have shown that yield stress depends on size even in the absence of the strain gradient. All of the experiments done on material creep behaviour, reported in the literature, have been conducted in the presence of strain gradient. This thesis focuses on the fabrication methods of freestanding indium pillar samples created by two unique methods; focused ion beam (FIB) and the micro-fabrication approach. The low melting point indium metal limits the application of FIB to form the sub-micron pillars. As a result, two different micro-lithography techniques, ultra-violet radiation and electron-beam lithography, were developed to fabricate these nano-pillars. In order to monitor the creep mechanism, which was dominant in this testing, the samples were then divided into two groups: polycrystalline and single-crystal pillars, each in different sizes. These pillars will later be compressed by a nano-indenter using a flat punch. Compressive stress, strain, and stiffness of the pillars will be measured to verify if the indium mechanical behavior deviates from the bulk in the absence of strong strain gradient.

The laws of classical mechanics show that mechanical properties are independent of sample sizes. However, based on extensive theoretical work and experimentation, it is believed that reducing the size of materials to the submicron scale can result in different mechanical properties than those found in bulk quantities. This size effect was explained by the strain gradient. Atomic simulations have shown that yield stress depends on size even in the absence of the strain gradient. All of the experiments done on material creep behaviour, reported in the literature, have been conducted in the presence of strain gradient. This thesis focuses on the fabrication methods of freestanding indium pillar samples created by two unique methods; focused ion beam (FIB) and the micro-fabrication approach. The low melting point indium metal limits the application of FIB to form the sub-micron pillars. As a result, two different micro-lithography techniques, ultra-violet radiation and electron-beam lithography, were developed to fabricate these nano-pillars. In order to monitor the creep mechanism, which was dominant in this testing, the samples were then divided into two groups: polycrystalline and single-crystal pillars, each in different sizes. These pillars will later be compressed by a nano-indenter using a flat punch. Compressive stress, strain, and stiffness of the pillars will be measured to verify if the indium mechanical behavior deviates from the bulk in the absence of strong strain gradient.

The viscoelastic and creep properties of salt create challenges in the design of salt mines. Salt undergoes steady state creep for a long period of time, and the time of failure is not easily predicted. Developing functions for creep behavior is important in predicting the deformation of salt pillars. Through literature reviews, it was found that there are many relationships to determine the deformation rate of salt specimens through constitutive models. Mine panels have also been modeled to understand the stress and deformational behavior of the pillars. The purpose of this was project was to develop a relationship that determines the convergence rate from knowing the pillar width to pillar height ratio and thickness of the salt strata immediately above and below the mine. The third power law was adopted in the modeling of salt pillars, which is applicable to low stresses of less than 10 MPa that is typical of salt mine conditions. The finite difference software, FLAC3D was used for the simulations of salt pillar models. A square pillar was modeled using four pillar width to pillar height ratios from 1.5 to 4.6. In mining practices, the pillar width to pillar height ratios are designed to be 1.0 to 5.0. Three sets of pillar dimensions were used for each pillar width to pillar height ratio, this was done to determine whether different room and pillar dimensions for each pillar width to pillar height ratio resulted in different convergence rates. Eight salt thicknesses of 0 m to 26 m were modeled for each set of pillar dimensions, which was sufficient to determine the effect of salt thickness on convergence rate. From the modeled results, general trends among the various pillar width to pillar height ratios were observed. The convergence rate increased as the pillar width to pillar height ratio decreased. In addition, an exponential relationship was found between the convergence rate and the pillar width to pillar height ratio. There was a strong correlation between convergence values calculated from the developed function and the modeled values for the power law exponent of three. The developed expression can be used to estimate the convergence rate due to pillar compression and room convergence.

Due to the micro-pillar-structured electrodes were made in the gas diffusion layer (GDL) of the proton exchange membrane fuel cell (PEMFC), the cell performance was raised significantly; the study therefore aims to understand whether the same cell performance can be achieved if the micro-pillar-structures were made in the direct methanol fuel cell (DMFC) of the anode. At room temperature and naturally breathed air, the performance of the micro-pillar-structured electrodes was the same as the conventional electrodes. The performance of the electrodes does not rely on the surface area between the micro porous layers and the catalyst. The experimental results inference indicates that no efficiency can be completed. The study then changed the experimental condition, i.e. increased the temperature of the methanol-water solution to 50¢J and reduced the methanol concentrations to 0.5M. The purpose was to carry out the reaction of the surface between the methanol and the catalyst layer. However, the experimental result shows no variation between the micro-pillar- structured electrodes and the conventional electrodes. Because of the test of the current density of the DMFC was carried out in a small power (0~25mW/cm2). The current density of the PEMFC was carried out in a high power (400mW/cm2 ~). The study proposed that the cell operating temperature can be raised and the oxygen can be put in the cathode, the performance of the micro-pillar-structured electrodes can thus be enhanced if the reaction was in a high current density. At the finals, the study tried to compare the efficiency between self-made electrodes and commercial electrodes (E-TEK). The result showed that both max power densities can reach 17mW/cm2 at room temperature and naturally breathed air.

The viscoelastic and creep properties of salt create challenges in the design of salt mines. Salt undergoes steady state creep for a long period of time, and the time of failure is not easily predicted. Developing functions for creep behavior is important in predicting the deformation of salt pillars. Through literature reviews, it was found that there are many relationships to determine the deformation rate of salt specimens through constitutive models. Mine panels have also been modeled to understand the stress and deformational behavior of the pillars. The purpose of this was project was to develop a relationship that determines the convergence rate from knowing the pillar width to pillar height ratio and thickness of the salt strata immediately above and below the mine. The third power law was adopted in the modeling of salt pillars, which is applicable to low stresses of less than 10 MPa that is typical of salt mine conditions. The finite difference software, FLAC3D was used for the simulations of salt pillar models. A square pillar was modeled using four pillar width to pillar height ratios from 1.5 to 4.6. In mining practices, the pillar width to pillar height ratios are designed to be 1.0 to 5.0. Three sets of pillar dimensions were used for each pillar width to pillar height ratio, this was done to determine whether different room and pillar dimensions for each pillar width to pillar height ratio resulted in different convergence rates. Eight salt thicknesses of 0 m to 26 m were modeled for each set of pillar dimensions, which was sufficient to determine the effect of salt thickness on convergence rate. From the modeled results, general trends among the various pillar width to pillar height ratios were observed. The convergence rate increased as the pillar width to pillar height ratio decreased. In addition, an exponential relationship was found between the convergence rate and the pillar width to pillar height ratio. There was a strong correlation between convergence values calculated from the developed function and the modeled values for the power law exponent of three. The developed expression can be used to estimate the convergence rate due to pillar compression and room convergence.

No description available.

No description available.

Research and experience using various types of mine backfill - hydraulic, rock, paste, and blended - has indicated several benefits to the mining industry. Backfill is a general term that refers to any waste material that is placed into underground mine workings. Paste backfill in particular has shown environmental and economic benefits. Paste fill is generally produced from total mine tailings, meaning that it can include waste rock, sands, and clay-sized particles. It also contains no free water, meaning that water will not flow freely through it after placement causing post filling shrinkage. These characteristics make it the most environmentally "friendly" backfill option currently available. In addition, paste backfill is non-segregating and stackable, containing about 80% solids by weight, and having the consistency of medium-slump concrete, containing a cementitious content. These characteristics make paste backfill the best option for post-mining ground control in room and pillar coal mines. There are two main bodies of research regarding paste backfill. The first studies its composition, application, and performance in past and present mining environments; the second studies its theoretical application for both mine support and waste disposal. While this research has provided much for the burgeoning technology of paste backfill, little has been done to investigate its economic application to the industry in room and pillar coal mines. At present, surface disposal of waste is generally cheaper than underground disposal. The goal of this thesis is to initiate discourse investigating the hypothesis that paste backfill may be used in such a way as to allow for increased coal extraction, which may then not only cover the additional costs of underground waste disposal, but potentially increase overall mine profitability. Inherent to this discourse will be a consideration of the following issues: * The potential for increased extraction. * The preservation of long-term pillar stability. * Improved floor stability. * Diminished environmental impact at surface. * The cost benefits associated with all of the above. Data from three Illinois Basin room and pillar coal mines were collected and used for this thesis. Theoretical computer modeling using LaModel and Phase2, empirical analysis of mine stability, physical testing using simulated paste backfill models, and comparative cost analyses considering current and hypothetical mining scenarios were conducted to identify these potential benefits and their consequences, both theoretical and practical.

Ingeniero Civil de Minas / Las metodologías utilizadas actualmente para la estimación de las dimensiones requeridas para la explotación mediante el método de Post-Pillar constan básicamente del cálculo del tamaño de pilares a emplear mediante fórmulas de limitada aplicación, dejando fuera restricciones sobre tamaño de paneles, altura de pilares en caso de falla por desprendimiento del techo u otras consideraciones operativas. El presente trabajo propone una nueva metodología de diseño para el método en cuestión. Utilizando como base herramientas tradicionales como metodologías analíticas y empíricas, el modelamiento numérico en FLAC3D permite integrar parte de esta metodología tradicional logrando un estudio con mayor nivel de detalle, mejorando las estimaciones. En base a las propiedades geomecánicas de la roca intacta, del macizo rocoso y condiciones de esfuerzo, es posible determinar las dimensiones de un pilar cuya resistencia se puede estimar a través de modelamiento numérico mediante la selección de un material de relleno. Por otra parte, es posible calcular las dimensiones del panel de explotación, altura máxima de este y el tamaño del pilar barrera en caso de ser necesario. Los resultados del modelamiento numérico muestran que la resistencia peak de los pilares con relleno aumenta con respecto a la resistencia sin relleno para todos los valores de GSI estudiados. Sin embargo, la contribución del relleno es considerablemente mayor para macizos de menor calidad llegando a aumentos de hasta un 500% en el mejor de los casos. Para valores de GSI de 60, 70 y 80, hay una clara tendencia a la disminución de la resistencia con relleno a medida que el pilar incrementa su altura. Para el GSI de 50 en cambio, la resistencia con relleno tiende a estabilizarse en un valor que depende de la geometría del pilar. Con respecto a las variables que influyen en su valor, esta presenta dependencia del ancho del pilar, del GSI del macizo rocoso y de las propiedades del relleno. Del trabajo realizado se desprende además la importancia de la etapa de modelamiento numérico como parte de la metodología considerando que esta herramienta permite integrar factores que la metodología empírica de estimación de resistencia de pilares deja fuera. Sin embargo se debe tener cuidado con ciertos aspectos. El criterio de falla de Hoek y Brown escogido para los pilares presenta en general buenos resultados para el GSI de 80 pero a medida que se disminuye este valor la calidad de los resultados también disminuye. Por otra parte, los métodos seleccionados para la secuencia de diseño responden a los elementos críticos identificados en el diseño del Post-Pillar, pero en este caso se deben plantear ciertas variantes para su uso. Las recomendaciones a futuro se relacionan con la estimación del tamaño de la losa cuando los pilares alcancen las alturas recomendadas y con el estudio de estallido de pilares integrando parámetros post-peak al modelamiento numérico.