Diamonds are commonly present in an ore called kimberlite. Kimberlites vary extensively in mineralogy and therefore can complicate the processing and the extraction of diamonds. Weathering of kimberlite was investigated in this study and refers to the rapid physical breakdown of the kimberlite material. Kimberlite weathering by organic molecule adsorption was investigated utilising organic solutions; ethanol, formamide, n-hexane, oxalic acid, urea, pentanoic acid and acetic acid, was investigated. The extent of weathering was measured by XRD, TGA and FTIR analysis as well as by evaluating changes in the particle size distribution. The idea to predict the susceptibility of weathering of kimberlite based on TGA analysis was discredited as it was found that there was no correlation between the smectite content and the % weight loss from TGA analysis. In XRD analysis studies to relate the d-spacing to the extent of weathering, it was found that the technique was not sensitive enough to enable direct prediction of weathering behaviour. Organic solutions at 0.5 M generally did not significantly alter the d-spacing. In the case of utilising pure organic solutions, it was observed that switching from diluted to pure organic solutions did not increase the d-spacings but rather lowers the space. Cation pretreatment prior to organic weathering resulted in d-spacings up to 2 water layers (12.6 Å being equal to 1 water layer, 15.6 Å equal to 2 layers and 18.6 Å equal to 3 layer). The general trend was that the divalent cations Mg2+ and Ca2+ increased the d-spacings whereas monovalent cations Na+ and K+ decreased the spacing. In the case of pre-organic treatment prior to organic weathering, it was observed that the resulting d-spacing increased to 2 and 3 water layers. TGA analysis confirmed that the kimberlite structure did absorb organic reagents during weathering. It was observed that the amount of organic reagents adsorbed decrease in the following order: oxalic acid > urea > pentanoic acid > formamide > ethanol > n-hexane > acetic acid, with oxalic acid having been adsorbed the greatest. In addition, it was also shown that the extent of inorganic cation adsorption was more than that of organic solutions. The analysis also showed that organic pretreatments yielded promising results and the order followed was dimethyldioctadecylammonium chloride > cetylpyridium chloride > dodecylamine > pyridine in encouraging subsequent organic adsorption. FTIR analysis results indicated the mechanism by which organic molucules attached onto the mineral surface. It was observed that there was a disturbance of the bond between water in the interlayer and the silicate structure by a stronger H-bond gained through organic molecule attachment. Oxalic acid was observed to cause a structural change due to proton attack of the silicate structure. It was found that kimberlite weathering, in essence, occurred in the first 24 hours of contact with the solution. Oxalic acid was found to be the most effective weathering agent compared to the rest of the tested organic solutions. The effect of the tested solutions, at 0.5 M concentration, on kimberlite weathering followed the series Cu2+ > oxalic acid > ethanol > acetic acid > formamide > n-hexane > distilled water. This study therefore showed that the accelerated weathering of kimberlite utilising organic solutions was not as efficient as the Cu2+ solution. Comparing Cu2+ and oxalic acid treatments, results showed that 67 % of the particles passed 12 mm screen size due to Cu2+ weathering as opposed to 48 % in oxalic acid. In investigating the effects of variables, it was found that time of exposure had a small effect in the weathering of kimberlite. Increasing the organic concentration from 0.025 M to 0.5 M saw an increase in the amount of particles passing the 12 mm screen size by~20 %. There was however no improved weathering when the solution temperature was increased from approximately 25 °C to 40 °C. In the study of kinetics involved during organic weathering utilising oxalic acid and comparing with Cu2+ medium, a high mineral dissolution was observed in the first 24 hours of contact with the weathering solution. However, different weathering mechanisms were observed between Cu2+ and oxalic acid. Inorganic solutions foster weathering by interlayer cation exchange which results in the reduction of the surface energy and this encourages further crack propagation. Oxalic acid weathering mechanism was by proton attack of the structural cations which was then limited thereafter by oxalate salts precipitation. Al3+ and Mg2+ were the dominant cations in solution during weathering (reaching 40 mmol/L) at higher oxalic acid concentration. This indicated that the dissolution of the clay‟s octahedral structure occurred, making oxalic acid a more effective agent than the rest of the tested organic solutions. An alternative method to transform non-swelling clay minerals to swelling in kimberlites was highlighted. It was observed that cation exchange treatment in conjunction with acid and oxidation treatments on kimberlites containing non-swelling minerals: mica or forsterite that are at least 30 % in quantity may result in the presence of swelling clays after these treatments. Kimberlite that contained serpentine minerals was more resistant to alteration under these conditions. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Materials Science and Metallurgical Engineering / UPonly

In order to increase the efficiency of diesel particulate filter regeneration more knowledge about diesel soot and its reactivity is required. This thesis compares soot created during accelerated filter loading by lowered rail pressure, with soot from normal filter loading. Soot properties and their correlations to oxidation reactivity are also examined through thermogravimetric analysis, scanning electron microscopy, energy dispersive x-ray spectroscopy, BET nitrogen sorption, and FTIR spectroscopy. The usefulness of these analysis methods was also evaluated. The soot samples consisted of two carbon blacks for reference (Printex U and Vulcan XC 72), four accelerated soot samples and two non-accelerated samples. The results showed that the accelerated samples contained less volatile organic compounds than the non-accelerated soot and required slightly higher temperatures to oxidize in air. Soot with a high oxygen/carbon ratio and high levels of volatile organic compounds was found to be the most reactive. The most useful method for analyzing the soot was the thermogravimetric analysis. The scanning electron microscopy and energy dispersive x-ray spectroscopy were useful additions but the FTIR spectroscopy provided very little useful information. The usefulness of BET nitrogen sorption was not decisively concluded. / För att kunna förbättra regenereringen av dieselpartikelfilter krävs en ökad kunskap om dieselsot och dess reaktivitet. I detta examensarbete jämförs sot som skapas vid accelererad sotinlagring genom sänkt railtryck, med sot från normal sotinlagring. Hur sotets egenskaper påverkar dess reaktivitet undersöks också genom termogravimetrisk analys, svepelektronmikroskopi, energidispersiv röntgenspektroskopi, BET-kväveadsorption och FTIR-spektroskopi. Hur väl dessa analysmetoder lämpar sig för analys av sot utvärderades också. Sotproverna utgjordes av två så kallade ”carbon black” för referens (Printex U och Vulcan XC 72), fyra accelererade sotprov och två icke-accelererade prov. Resultaten visade att de accelererade proverna innehöll mindre flyktiga organiska föreningar än icke-accelererade sot och krävde något högre temperaturer för att oxideras i luft. Sot med ett högt syre/kol-förhållande och höga nivåer av flyktiga organiska föreningar visade sig vara mest reaktivt. Den mest användbara metoden för att analysera sot var den termogravimetriska analysen. Svepelektronmikroskopi och energidispersiv röntgenspektroskopi var användbara som komplementerande metoder men FTIR-spektroskopi gav väldigt lite användbar information. Ingen konkret slutsats drogs gällande nyttan av BET-kväveadsorption.

Among the latest achievements in gasification technology, one may list the development of a method to preheat gasification agents using switched ceramic honey combs. The best output from this technology is achieved with use of water steam as a gasification agent, which is heated up to 1600 °C. The application of these temperatures with steam as a gasification agent provides a cleaner syngas (no nitrogen from air, cracked tars) and the ash melts into easily utilised glass-like sludge. High hydrogen content in output gas is also favourable for end-user applications.Among the other advantages of this technology is the presumable application of fixed-bed-type reactors fed by separately produced and preheated steam. This construction assumes relatively high steam flow rates to deliver the heat needed for endothermic reactions involving biomass. The biomass is to be heated uniformly and evenly in the volume of the whole reactor, providing easier and simpler control and operation in comparison to other types of reactors. To provide potential constructors and exploiters of these reactors with the kinetic data needed for the calculations of vital parameters for both reactor construction and exploitation, basic experimental research of high-temperature steam gasification of four types of industrially produced biomass has been conducted.Kinetic data have been obtained for straw and wood pellets, wood-chip charcoal and compressed charcoal of mixed origin. Experiments were conducted using two experimental facilities at the Energy and Furnace Division of the Department of Material Science and Engineering (MSE) at the School of Industrial Engineering and Management (ITM) of the Royal Institute of Technology (KTH) and at the Combustion Laboratory of the Mechanical Engineering Department of the University of Maryland (UMD), USA. The experimental facility at the Energy and Furnace Division has been improved with the addition of several constructive elements, providing better possibilities for thermo-gravimetric measurements.The obtained thermo-gravimetric data were analysed and approximated using several models described in the literature. In addition, appropriate software based on the Scilab package was developed. The implementation of the isothermal method based on optimisation algorithms has been developed and tested on the data obtained under the conditions of a slow decrease of temperature in experiments with the char gasification in small-scale experimental facilities in the Energy and Furnace Division.The composition of the gases generated during the gasification of straw and wood pellets by high-temperature steam has been recorded and analysed for different experimental conditions. / <p>QC 20101124</p> / Study of ignition and kinetics of biomass/solid waste thermal conversion with high-temperature air/steam

No description available.

An experimental study on the effect of fuel mixing on the products resulting from hydrothermal liquefaction (HTL) was conducted. The feedstocks used were kraft lignin (KL), GROT (GT) and microalgae cultivated in wastewater (MA). Three sets of mixtures were prepared, each containing two types of feedstocks with a 1:1 ratio: KLGT, MAKL, and MAGT. The experiments were performed using a pilot-scale continuous HTL-system. Elemental analysis CHNO and thermogravimetric analysis were used to determine the ultimate and proximate composition of the samples. Scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) was used to further analyse the elemental distribution on the hydrochars’ surface. The co-liquefaction effect (CE) was evaluated by comparing the experimental results found for the mixtures with the theoretical values calculated as the average of the respective pure components. The results showed that the yield of light oil was not significantly affected for any mixture. However, the mixtures containing KL showed a lower yield of heavy oil than the predicted value, while a higher yield was found for MAGT. All heavy oils had higher carbon content than expected from the predicted values. Every mixture had a significantly larger yield of hydrochar than what was expected. The increased yield of hydrochar for KLGT was insufficient to compensate for the loss of heavy oil and thus the overall product yield was decrease showing antagonistic interactions in the mixture. The hydrochar from MAGT had the highest ash content, and upon closer inspection with SEM/EDS it showed a much larger phosphorus content than any other hydrochar, even compared to the predicted value. This suggests that an interaction between MA and GROT causes the hydrochar to bind more contaminants and enables it to collect more ash than what would have been achieved from liquefying the components individually. Thus, MAGT showed synergetic effects overall, MAKL had increased carbon recovery but at the cost of heavy oil yield making in a poor choice for HTL, and KLGT showed antagonistic effects in the form of lower yield of biocrude and overall recovery of products. The study highlights that co-liquefaction can potentially have a larger impact on the hydrochar than it does on the biocrude, and that evaluation of hydrochar should be included when examining co-liquefaction

En los últimos años, el calzado fabricado en España, y en la Unión Europea en general, camina hacia nuevos conceptos en los que la sostenibilidad y la incorporación de los elementos "activos" van a tener un importante papel como valor añadido y elemento de competitividad. Este hecho obliga a los fabricantes de calzado y componentes a reinventarse y desarrollar nuevos productos que cumplan con las exigencias tanto del mercado como de los consumidores. Con los últimos avances en el campo de los materiales funcionales y/o activos se abre una nueva vía para el desarrollo de productos que presenten propiedades funcionales dirigidas a los diversos grupos de usuarios con características y necesidades específicas. En ese sentido, la tecnología de microencapsulación es una herramienta prometedora para este sector tan tradicional, ya que permite transformar el calzado en un nuevo soporte para proporcionar tanto un cuidado estético y sanitario del pie como para mejorar el confort del mismo, entre otras muchas posibilidades. La incorporación de sustancias microencapsuladas en los materiales o componentes del calzado permitirá dotar al calzado de nuevas prestaciones y alcanzar el concepto de calzado activo, el cual contribuirá a mejorar la calidad de vida del usuario, satisfaciendo las necesidades y expectativas de los mismos. El objetivo general de este trabajo se centra en la microencapsulación de sustancias activas tales como agentes antimicrobianos y aromas y su posterior incorporación en los materiales de calzado para lograr obtener un nuevo calzado funcional que permita un cuidado activo del pie de los usuarios durante su uso. Para lograr dicho objetivo, este trabajo se ha estructurado en cinco capítulos. En la introducción se detallan las necesidades del sector calzado y se presentan las tecnologías emergentes capaces de proporcionar un salto cualitativo en cuanto a sus perspectivas futuras. En el segundo capítulo se describe y se detallan los objetivos específicos perseguidos con el desarrollo de este trabajo de investigación. En el tercer capítulo se describen los materiales utilizados para llevar a cabo este trabajo, así como las diferentes técnicas instrumentales empleadas para la síntesis, funcionalización y caracterización de microcápsulas y materiales de calzado empleados. El capítulo de resultados y discusión consta de un compendio de 6 publicaciones fruto del trabajo de investigación de investigación realizado en esta tesis. Se ha realizado un estudio de la microbiota del pie sano, así como una revisión de las técnicas en el campo de la nanotecnología que junto con la microencapsulación presentan un gran desafío en cuanto a su aplicación en el sector calzado. Además y fundamentalmente, se ha estudiado la microencapsulación de sustancias mediante la técnica de polimerización in situ para encapsular un aceite esencial con reconocidas propiedades antimicrobianas como es el aceite de Melaleuca alternifolia. Mediante estudios de Termogravimetría (TGA), Espectroscopía Infrarroja (FTIR) y Microscopía Electrónica de Barrido (SEM) principalmente, se ha profundizado en el mecanismo de encapsulación y liberación de los aceites esenciales estudiados, tanto en lo relativo a la formación de microcápsulas como en las posibles interacciones fisicoquímicas entre la resina y el aceite, así como su efecto en la liberación del aceite esencial en tratamientos combinados que simulan las condiciones de uso de estos productos. Los resultados obtenidos han demostrado que la relación resina:aceite determina en gran medida la eficiencia de encapsulación así como que existe un valor crítico que determina las propiedades de las microcápsulas sintetizadas y las posibles interacciones fisicoquímicas con los componentes del aceite esencial. Los ensayos de simulación de uso en calzado mostraron que el sudor influye en el perfil de liberación del aceite del núcleo y que la acción combinada de sudor y presión además modifica las características de las microcápsulas. El diseño de microcápsulas con resistencias y diferentes perfiles de liberación de la sustancia activa permite obtener un efecto más prolongado del aroma y/o efecto antimicrobiano en el calzado.

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No description available.

Results of this research are available online in two published papers. / The main focus of this research was to synthesize and then to characterize the potential high-performance thermoelectric materials. In this regard, we have prepared a series of pure RECuSe2 (with RE = Pr, Sm, Gd, Dy and Er) and RECuTe2 (with RE = Er, Dy and Gd) and analyzed their crystal structure, electronic and physical properties. We used powder and single crystal X-ray diffraction techniques to analyze their crystal structures and employed energy dispersive X-ray spectrometry (EDS) to verify their chemical compositions. The temperature stability of the synthesized samples was examined by differential thermal and gravimetrical analysis. The high-purity consolidated pellets were prepared for physical properties measurements. We analyzed the relationship between their crystal structures and pertinent electronic properties through the LMTO calculations. The RECuSe2 phases adopt two structures, monoclinic and trigonal. The monoclinic structure (P21/c, z = 4) is observed for lighter rare earths (RE = Pr, Sm and Gd) and Cu-disordered trigonal structure for heavier rare earths (P m1, z = 1, RE = Dy and Er). The resistivity and Seebeck coefficient measurements indicate that the studied selenides are p-type semiconductors with relatively small activation energies (0.045-0.12 eV). However, their electrical resistivities are too high (0.49-220 Ohmcm at room temperature) to make them competitive thermoelectric materials. Electronic structure calculations indicate presence of a band gap in the RECuSe2 phases. The synthesized RECuTe2 phases (RE = Er, Dy and Gd) adopt a monoclinic-distorted variant (C2/m, z = 2) of the trigonal structure (P m1, Z= 1) observed for the RECuSe2 (with RE = Dy, Er). While such disorder may be beneficial for lowering their thermal conductivity, large values of electrical resistivity (0.02-0.87 Ohmcm at room temperature) make these phases unsuitable for practical applications. Comparing to the corresponding semiconducting selenides, the tellurides have lower resistivities, and display a metallic type resistivity. Such behavior stems from the closure of band gaps, which is verified by the electronic structures calculations. Structurally the RECuTe2 phases (with RE = Er, Dy and Gd) are similar to RECuSe2 with the P m1 structure. The monoclinic distortion in RECuTe2 is driven by Cu displacement inside the larger tetrahedral voids in the hexagonal close packing of the Te atoms. Most likely, Cu shifts to one side of the Te tetrahedra to optimize the Cu-Te interactions. / Thesis / Candidate in Philosophy

The work presented in this thesis is divided into two research areas. In part I, the synthesis and guest intercalation of inorganic-organic metal halide ammonium layered perovskites is discussed. Comparisons are made between the solid matrix before and after the intercalations, and all solids are characterized using thermogravimetric analysis (TGA) and powder X-ray diffraction (XRD). In part II, “templateree” hydrothermal synthesis of tin oxide spheres in the presence of different ortho-substituted anilines is discussed. The aim is to determine whether there are differences in the structures, shapes and surface morphology of the tin oxide spheres that correspond to the identity/shape of the ortho-substituent on the anilines. Solids were characterized by XRD, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques.