Dissertations / Theses: 'Metal and abrasive particles'

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Weber, Xavier. "Elaboration par dépôt électrolytique de revêtements composites métal/particules pour la réalisation de fils abrasifs." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI059.

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Le passage de la technologie au slurry à celle au fil diamanté sur les machines à fils de découpe des blocs de silicium en wafers est motivé par des enjeux économiques et environnementaux. Depuis peu, cette transition de technologie dans l’industrie photovoltaïque s’est accélérée avec la commercialisation d’une nouvelle génération de machines. Afin de profiter de cette transition et de son avenir prometteur, Thermocompact s’est engagé dans le développement de fils diamantés. Le procédé choisi pour le dépôt des particules et du liant métallique enchâssant les particules à la surface du fil est la voie électrochimique. Les premiers essais de fabrication de fils diamantés ont révélé un manque de maîtrise du procédé d’élaboration et un échec pour atteindre les caractéristiques techniques demandées pour la découpe du silicium. Les travaux de cette thèse se sont donc axés dans un premier temps sur la relation entre le bain électrolytique, les conditions de dépôt et ses propriétés, puis sur le comportement des particules à la fois dans le bain jusqu’à leur incorporation à la surface du fil. L’étude s’est poursuivie sur la relation complexe entre les caractéristiques du fil produit, la matière à découper et la machine de découpe utilisée (design, paramètres utilisés). Ce travail a abouti à produire un fil diamanté de diamètre 70µm conforme aux exigences des usineurs pour la découpe à l’échelle industrielle du silicium monocristallin sur des machines de nouvelle génération. Les résultats de découpe vont permettre désormais de démarcher des clients potentiels dans l’industrie photovoltaïque The change of technology from slurry to diamond wires in the wafer slicing machines is motivated by economic and environmental issues. Only recently, this transition of technology in the photovoltaic industry has ramped up with the commercialization of a new generation of wafering machines. So as to take advantage of this situation, Thermocompact has launched the development of diamond wires. The selected process is an electrochemical codeposition of metal and diamond particles embedded on the wire surface.The first tests of diamond wire production have shown a lack of process control and a failure to reach the technical characteristics requested by its use. The studies in this thesis are based on the relationship between the electrolytic bath, the coating conditions and the coating properties, then on the behavior of particles both in the bath and up to their incorporation on the wire surface. The researches continued afterwards on the complex link between the characteristics of diamond wire, the material to slice and the machine used for slicing (design, recipe). This work has succeeded in defining a diamond wire with a diameter of 70µm in compliance with customer requirement for the industrial slicing of single crystalline silicon with the new generation of machines. These results will be now used for prospecting new customers in the photovoltaic industry

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Khan, Kirity Bhusan. "Processing And Characterization Of B4C Particle Reinforced Al-5%Mg Alloy Matrix Composites." Thesis, Indian Institute of Science, 2000. https://etd.iisc.ac.in/handle/2005/182.

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Metal matrix composites (MMCs) are emerging as advanced engineering materials for application in aerospace, defence, automotive and consumer industries (sports goods etc.). In MMCs, a metallic base material is reinforced with ceramic fiber, whisker or particulate in order to achieve a combination of properties not attainable by either constituent individually. Aluminium or its alloy is favoured as metallic matrix material because of its low density, easy fabricability and good engineering properties. In general, the benefits of aluminium metal matrix composites (AMCs) over unreinforced aluminium alloy are increased specific stiffness, improved wear resistance and decreased coefficient of thermal expansion. The conventional reinforcement materials for AMCs are SiC and AI2O3. In the present work, boron carbide (B4C) particles of average size 40μm were chosen as reinforcement because of its higher hardness (very close to diamond) than the conventional reinforcement like SiC, AI2O3 etc. and of its density (2.52 g cm"3) very close to Al alloy matrix. In addition, due to high neutron capture cross-section of 10B isotope, composites containing B4C particle reinforcement have the potential for use in nuclear reactors as neutron shielding and control rod material. Al-5%Mg alloy was chosen as matrix alloy to utilize the beneficial role of Mg in improving wettability between B4C particles and the alloy melt. (Al-5%Mg)-B4C composites containing 10 and 20 vol% B4C particles were fabricated. For the purpose of inter-comparison, unreinforced Al-5%Mg alloy was also prepared and characterized. The Stir Cast technique, commonly utilized for preparation of Al-SiC, was adapted in this investigation.The Composites thus prepared was subsequently hot extruded with the objective of homogenization and healing minor casting defects. Finally the unreinforced alloy and its composites were characterized in terms of their microstructure, mechanical and thermo-physical properties, sliding wear behaviour and neutron absorption characteristics. The microstructures of the composites were evaluated by both optical microscope and scanning electron microscope (SEM). The micrographs revealed a relatively uniform distribution of B4C particles and good interfacial integrity between matrix and B4C particles. The hot hardness in the range of 25°C to 500°C and indentation creep data in the range of 300°C to 400°C show that hot hardness and creep resistance of Al-Mg alloy is enhanced by the presence of B4C particles. Measurement of coefficient of thermal expansion (CTE) of composites and unreinforced alloy upto 450°C showed that CTE values decrease with increase in volume fraction of reinforcement. Compression tests at strain rates, 0.1, 10 and 100 s-1 in the temperature range 25 - 450 °C showed that the flow stress values of composites were, in general, greater than those of unreinforced alloy at all strain rates. These tests also depicted that the compressive strength increases with increase in volume fraction of reinforcements. True stress values of composites and unreinforced alloy has been found to be a strong function of temperature and strain rate. The kinetic analysis of elevated temperature plasticity of composites revealed higher stress exponent values compared to unreinforced alloy. Similarly, apparent activation energy values for hot deformation of composites were found to be higher than that of self-diffusion in Al-Mg alloy. Tensile test data revealed that the modulus and 0.2% proof stress of composites increase with increase in volume fraction of the reinforcements. Composites containing 10%BUC showed higher ultimate tensile strength values (UTS) compared to unreinforced alloy. However, composites with 20%B4C showed lower UTS compared to that of the unreinforced alloy. This could be attributed to increased level of stress concentration and high level of plastic constraint imposed by the reinforcing jparticles or due to the presence solidification-induced defects (pores and B4C agglomerates ). Sliding wear characteristics were evaluated at a speed of 1 m/s and at loads ranging from 0.5 to 3.5kg using a pin-on-disc set up. Results show that wear resistance of Al-5%Mg increases with the addition of B4C particles. Significant improvement in wear resistance of Al-5%Mg is achieved with the addition of 20% B4C particles. SEM examination of worn surfaces showed no pull-out of reinforcing particles even at the highest load of 3.5 kg, thus confirming good interfacial bonding between dispersed B4C particles and Al alloy matrix. The neutron radiography data proved that (Al-5%Mg)-B4C composites possess good neutron absorbing characteristics. From the experimental data evaluated in the "study, it may be concluded that (Al-5%Mg)-B4C composites could be a candidate material for neutron shielding and control rod application. The enhanced elevated temperature-strength and favourable neutron absorption characteristics of these composites are strong points in favour of this material.

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Khan, Kirity Bhusan. "Processing And Characterization Of B4C Particle Reinforced Al-5%Mg Alloy Matrix Composites." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/182.

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Metal matrix composites (MMCs) are emerging as advanced engineering materials for application in aerospace, defence, automotive and consumer industries (sports goods etc.). In MMCs, a metallic base material is reinforced with ceramic fiber, whisker or particulate in order to achieve a combination of properties not attainable by either constituent individually. Aluminium or its alloy is favoured as metallic matrix material because of its low density, easy fabricability and good engineering properties. In general, the benefits of aluminium metal matrix composites (AMCs) over unreinforced aluminium alloy are increased specific stiffness, improved wear resistance and decreased coefficient of thermal expansion. The conventional reinforcement materials for AMCs are SiC and AI2O3. In the present work, boron carbide (B4C) particles of average size 40μm were chosen as reinforcement because of its higher hardness (very close to diamond) than the conventional reinforcement like SiC, AI2O3 etc. and of its density (2.52 g cm"3) very close to Al alloy matrix. In addition, due to high neutron capture cross-section of 10B isotope, composites containing B4C particle reinforcement have the potential for use in nuclear reactors as neutron shielding and control rod material. Al-5%Mg alloy was chosen as matrix alloy to utilize the beneficial role of Mg in improving wettability between B4C particles and the alloy melt. (Al-5%Mg)-B4C composites containing 10 and 20 vol% B4C particles were fabricated. For the purpose of inter-comparison, unreinforced Al-5%Mg alloy was also prepared and characterized. The Stir Cast technique, commonly utilized for preparation of Al-SiC, was adapted in this investigation.The Composites thus prepared was subsequently hot extruded with the objective of homogenization and healing minor casting defects. Finally the unreinforced alloy and its composites were characterized in terms of their microstructure, mechanical and thermo-physical properties, sliding wear behaviour and neutron absorption characteristics. The microstructures of the composites were evaluated by both optical microscope and scanning electron microscope (SEM). The micrographs revealed a relatively uniform distribution of B4C particles and good interfacial integrity between matrix and B4C particles. The hot hardness in the range of 25°C to 500°C and indentation creep data in the range of 300°C to 400°C show that hot hardness and creep resistance of Al-Mg alloy is enhanced by the presence of B4C particles. Measurement of coefficient of thermal expansion (CTE) of composites and unreinforced alloy upto 450°C showed that CTE values decrease with increase in volume fraction of reinforcement. Compression tests at strain rates, 0.1, 10 and 100 s-1 in the temperature range 25 - 450 °C showed that the flow stress values of composites were, in general, greater than those of unreinforced alloy at all strain rates. These tests also depicted that the compressive strength increases with increase in volume fraction of reinforcements. True stress values of composites and unreinforced alloy has been found to be a strong function of temperature and strain rate. The kinetic analysis of elevated temperature plasticity of composites revealed higher stress exponent values compared to unreinforced alloy. Similarly, apparent activation energy values for hot deformation of composites were found to be higher than that of self-diffusion in Al-Mg alloy. Tensile test data revealed that the modulus and 0.2% proof stress of composites increase with increase in volume fraction of the reinforcements. Composites containing 10%BUC showed higher ultimate tensile strength values (UTS) compared to unreinforced alloy. However, composites with 20%B4C showed lower UTS compared to that of the unreinforced alloy. This could be attributed to increased level of stress concentration and high level of plastic constraint imposed by the reinforcing jparticles or due to the presence solidification-induced defects (pores and B4C agglomerates ). Sliding wear characteristics were evaluated at a speed of 1 m/s and at loads ranging from 0.5 to 3.5kg using a pin-on-disc set up. Results show that wear resistance of Al-5%Mg increases with the addition of B4C particles. Significant improvement in wear resistance of Al-5%Mg is achieved with the addition of 20% B4C particles. SEM examination of worn surfaces showed no pull-out of reinforcing particles even at the highest load of 3.5 kg, thus confirming good interfacial bonding between dispersed B4C particles and Al alloy matrix. The neutron radiography data proved that (Al-5%Mg)-B4C composites possess good neutron absorbing characteristics. From the experimental data evaluated in the "study, it may be concluded that (Al-5%Mg)-B4C composites could be a candidate material for neutron shielding and control rod application. The enhanced elevated temperature-strength and favourable neutron absorption characteristics of these composites are strong points in favour of this material.

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4

Dube, Nokuthula. "Aspects of wear by free abrasive particles." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615027.

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Popa, Mihaela. "Tooth cleaning : abrasive particles but no abrasion." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI034.

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En 1997 Stuard L. Fischman a dit « Certainement on mange bien, on parle bien, on a l'air bien et on « sent frais » - mais on a aussi la plaque dentaire, la gingivite et les caries dentaires. Le lecteur peut déterminer les progrès réalisés en réfléchissant à son état de santé bucco-dentaire personnel! ». Vingt ans plus tard cette affirmation reste valide. L'acte le plus commun d'hygiène buccale est de se nettoyer les dents par brosse à dents, eau et dentifrice. Le rôle principal de la brosse à dents et du dentifrice est d'éliminer le biofilm dentaire responsable des maladies buccales. Il est largement admis que le biofilm dentaire est éliminé au moyen de particules de nettoyage trouvés dans la composition du dentifrice. Puisque le mécanisme des particules nettoyantes est couramment supposé abrasif, la recherche sur le nettoyage des dents a été principalement conduite du point de vue « abrasif », elles sont ainsi appelées « particules abrasives ». Néanmoins, le nettoyage des dents est un processus complexe impliquant plusieurs mécanismes (biochimiques, physico-chimiques et mécaniques), chacun activé par des facteurs à la fois internes (comme l'environnement oral individuel et les habitudes individuelles d'hygiène buccale) et externes La conception de la brosse à dents et la composition de dentifrice). Ce travail a commencé à partir de l'idée que le nettoyage des dents ne peut pas être réduit à un processus d'abrasion; par conséquence, afin d'acquérir une connaissance plus profonde du comportement réel des particules nettoyantes, il est nécessaire de comprendre la contribution de chaque mécanisme d'action impliqué. Un système biomimétique a été développé pour reproduire la brosse à dents, l'émail dentaire, la pellicule exogène acquise et le dentifrice (une suspension simplifiée à base de silice). Le système a été analysé d'un point de vue tribologique, en adoptant la théorie du « troisième corps » et en utilisant différentes techniques expérimentales (spectroscopie infrarouge, microscopie à force atomique, la microscopie électronique à balayage). On a déterminé la contribution de la mécanique et de la physico-chimie de la surface de l'émail dentaire, de la chimie du dentifrice et de la mécanique de la brosse à dents. Les résultats ont montré que la pellicule exogène acquise biomimétique n'a pas été rayée pendant le nettoyage des dents, mais plutôt lissée ou enlevée, ce qui suggère que l'abrasion n'est pas le mécanisme «gouvernant» du processus de brossage des dents. En effet, un mécanisme de «lubrification fractionnée» est supposé intervenir, favorisant la formation des agglomérats de silice supportent la charge normale dans des zones de contact localisées. L'efficacité du processus de nettoyage des dents est censée être contrôlée par la taille des agglomérats de silice, qui dépend à son tour de la mécanique et la physico-chimie de la surface de l’émail dentaire, de la chimie du dentifrice et de la mécanique de la brosse à dents In 1997, Stuart L. Fischman wrote “We certainly eat well, speak well, look fine and ‘smell fresh’—but we also have plaque, gingivitis and dental caries. The reader can determine how much progress has been made by reflecting on his or her personal oral health status!” Two decades later, this affirmation is still valid. The most common act of oral hygiene is to clean one’s teeth via toothbrush, water, and dentifrice. The main role of toothbrush and dentifrice is to remove the dental biofilm responsible for oral diseases. Over the years, several studies have focused on improving toothbrushing techniques, toothbrush design, and dentifrice composition, often leading to conflicting results. It is largely accepted that dental biofilm is removed by means of cleansing particles, which can be found in many dentifrice compositions. Since the mechanism of the cleansing particles is commonly believed to be abrasive, research on teeth cleaning has been mainly conducted from an ‘abrasive’ point of view, so much so that cleansing particles are frequently referred to as ‘abrasive particles’. Nonetheless, teeth cleaning is a complex process involving several mechanisms (bio-chemical, physico-chemical, and mechanical), each one activated by factors that are both internal (such as individual oral environment and individual oral hygiene habits) and external (such as toothbrush design and dentifrice composition). This work started from the idea that teeth cleaning cannot be reduced to an abrasion process; consequently, in order to gain deeper knowledge about the actual behavior of the cleansing particles, it is necessary to understand the contribution of each mechanism involved. A biomimetic system was developed to reproduce toothbrush, dental enamel, acquired enamel pellicle, and dentifrice (modeled as a silica-based slurry). The system was analyzed from a tribological point of view, adopting the ‘third-body approach’ and employing different experimental techniques such as infrared spectroscopy, atomic force microscopy, and environmental scanning electron microscopy. The contribution of the dental enamel surface mechanics and physico-chemistry, of the dentifrice chemistry, and of toothbrush mechanics was assessed. Results showed that the biomimetic acquired enamel pellicle was not scratched during teeth cleaning, but rather smoothened or removed, suggesting that abrasion is not the governing mechanism of the toothbrushing process. Indeed, a ‘fractionated lubrication’ mechanism is believed to take part, promoting the formation of silica agglomerates that bear normal load at localized contact areas. The effectiveness of the teeth cleaning process is believed to be controlled by the size of the silica agglomerates, which in turn depends on dental enamel surface mechanics and physico-chemistry, dentifrice chemistry, and toothbrush mechanics

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Jayawardane, Dammika Nilanthi. "Characterization of abrasive boron nitride hard particles." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619783.

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Wang, Aiguo. "Abrasive wear of metal matrix composites." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305516.

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Born, Melanie P. (Melanie Providencia) 1975. "Ice and abrasive particles : an alternative CMP polishing technique." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9570.

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Chinyamakobvu, Oswald Simbarashe. "Metal matrix composites for abrasive wear resistance." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/46998.

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Rose, Christopher. "Investigating the efficacy of novel abrasive particles in oral hygiene." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/12048/.

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This thesis is concerned with the abrasive particles used within toothpastes for oral care products. The dynamic and abrasive characteristics of different particles is analysed using a variety of experimental and observational techniques, in order to discern their suitability as an abrasive agent upon sensitive human tissue such as dentine. It is of particular interest to companies working within Oral Care, to develop an abrasive formula that is both adept at removing surface detritus such as plaque, but does not cause damage to the underlying tissues of the tooth such as enamel and dentine. Further to their role as an abrasive agent for detrital removal, particles are also utilised to act as an aid against dental hypersensitity, by infiltrating and sealing off dentinal tubules. The main focus of this thesis is to study both the individual and collective behaviour of the particles in order to better understand the practicality and influence particles can introduce within oral care and why. The efficacy of the particles is analysed from 3 key perspectives: 1. The abrasive performance of particles under a variety of tribological testing. Particular attention was paid to the wear characteristics of the particles upon key dental tissue. 2. Visualising and understanding the dynamic characteristics of the particles when motivated in an effort to relate these findings to wear observations. 3. To investigate the positive role of some key particles as an aid in dental hypersensitity. It was found that subtle variation in particle size and shape can have a significant effect upon the magnitude of the wear. This shape can affect the abrasive properties in more than one way, either by having a more aggressive shape leading to increased scratching and material removal; or by augmenting the affinity of the particle to agglomerate and operate as an agglomeration when motivated. Nano-manipulation techniques are employed to discern the dynamic characteristics of the particles. Being able to directly observe the particles when manipulated rather than attempt to derive suppositions from wear tracks, leads to a much improved understanding of a particles dynamic traits as well as the characteristics of particle breakdown. A comparison is made between the occlusive efficacies of bespoke precipitated calcium carbonate versus typical ground particles. Clear differences between the particles were observed, highlighting a delicate relationship with the presence of water. The aim of this research is to contribute further understanding of the important role that abrasive particles play within oral care, and to draw conclusions as to what factors play a key role in making a particle aggressive or sympathetic to a substrate surface.

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Ramakrishnan, Easwar Vinayak. "An Investigation into 'Squeezing'or Three-Body Wear caused by Abrasive Particles." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-283552.

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Material wear is an ever present phenomenon and can never be completely removed in systems of moving parts. There will always be friction between materials, causing degradation of these materials and eventually the material will be worn out and have to be replaced. In industrial applications, the cost of failure of a material is severe and thus it is important to understand how long a material will operate at a certain working condition. Thus in order to be able to predict the life of a material, the wear mechanisms of the application need to be understood. Squeezing wear or three body wear is a phenomenon occurring when abrasive particles are rolling between two material surfaces. This is not a well researched field, especially when it concerns two steel surfaces with abrasives present between them. Thus the objective of this study was to observe the effect of abrasive particles on the wear of the materials. For this purpose, pin and disk wear tests were conducted both in the presence and absence of abrasive particles. The results show that the abrasive particles act as a buffer between the two materials and hence the specific wear rate observed when the abrasive particles are present is far lesser than the specific wear rate in their absence. Thus this confirms previous research findings that the rate of wear in three body abrasion is lower than the wear rate in two body abrasion. Adhesive wear was observed in one of the material combinations in the absence of abrasive particles. This is a severe type of wear and occurs at far higher rate than observed for two-body or three-body abrasion. Materialslitage är ett ständigt närvarande fenomen och kan aldrig tas bort helt i system med rörliga delar. Det kommer alltid att finnas friktion mellan material, vilket orsakar nedbrytning av dessa och så småningom kommer materialet att bli utslitet och måste bytas ut. I industriella applikationer är kostnaden för att materialet går sönder stora och det är därför viktigt att förstå hur länge ett material kommer att fungera vid ett visst arbetsförhållande. För att kunna förutsäga livslängden för ett material måste således slitagemekanismerna för applikationen förstås. Klämslitage eller slitage på tre kroppar är ett fenomen som uppstår när slipande partiklar rullar mellan två materialytor. Detta är inte ett välundersökt område, speciellt när det gäller två stålytor med slipmedel närvarande mellan dem. Således var målet med denna studie att observera effekten av slipande partiklar på materialets slitage. För detta ändamål utfördes ”pinne på disk” förslitningstester, både i närvaro och frånvaro, av slipande partiklar. Resultaten visar att de slipande partiklarna fungerar som en buffert mellan de två materialen och följaktligen är den specifika nötningshastigheten som observeras när de slipande partiklarna är närvarande mycket lägre än den specifika nötningshastigheten i deras frånvaro. Detta bekräftar sålunda tidigare forskningsresultat att slitaget vid trekropparsnötning är lägre än vid tvåkropparsnötning. Adhesiv nötning observerades i en av materialkombinationerna i frånvaro av slipande partiklar. Detta är en allvarlig typ av slitage och uppträder i mycket högre takt än observerat för nötning mellan två eller tre kroppar.

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Awan, Muhammad Rizwan. "Specific energy consumption of metal cutting with thin abrasive discs." Doctoral thesis, Universitat Politècnica de Catalunya, 2021. http://hdl.handle.net/10803/672919.

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The aim of this research is to provide an in-depth understanding of energy consumption in abrasive disc cutting processes. The specific energy consumed in cutting is measured,analysed, and then characterised in to three components. To this end, an experimental device is built using an Arduino-controlled grinder to measure the specific energy consumed by cutting at different feed rates. Using a model, the experimental data is validated and the Specific Energy Consumed is separated into three energy components: sliding, ploughing and specific cutting energy. Furthermore, the influence of cutting conditions and material properties significantly influenced the specific energy consumption and its components. To analyse the effect of grain shape and the relative dependence of the different components of the Specific Energy Consumed as a function of material removal rate, integral models of specific ploughing energy, specific sliding energy and specific cutting energy are developed. Conventional and super abrasive cubitron abrasive grains were used. Cutting with pyramidal abrasive discs (cubitron) was used for the determination of the relative components of the specific energy consumed. It was found that the specific ploughing energy is more sensitive to the change in material removal rate compared to the sliding energy. Due to the fast shearing and precisely shaped cubitron grains, the transition from sliding to a specific shear regime was so fast for some materials that the magnitude of the ploughing energy was found to be negligible.However, the model implementation for some materials showed that the absence or presence of ploughing energy also depends on the rate of material removed. Finally, the development of a cutting grain model is presented which will allow the study of the chip compression ratio which is not possible to characterise by means of a single cutting grain in metal cutting with thin abrasive discs. This latest development is the beginning of a study of chip formation in the primary cutting zone of an abrasive grain. This research provides a machine and a methodology to characterise cutting with commercially available abrasive discs in terms of the Specific Energy Consumed parameter. El objetivo de esta investigación es proporcionar un conocimiento profundo sobre el consumo de energía en los procesos de corte con discos abrasivos. Se mide y analiza la energía específica consumida en el corte, caracterizando dicha energía en tres componentes. Para ello se construye un dispositivo experimental que utiliza una amoladora controlada por un Arduino, para medir la energía específica consumida por el corte a diferentes velocidades de alimentación. Utilizando un modelo, se validaron los datos experimentales y se separa la Energía Específica Consumida en tres componentes energéticos: deslizamiento, arado y energía de corte específica. Además, la influencia de las condiciones de corte y las propiedades del material influyeron significativamente en el consumo de energía específico y sus componentes. Para analizar el efecto de la forma del grano y la dependencia relativa de las diferentes componentes de la Energía Específica Consumida en función de la tasa de remoción de material. Se desarrollan modelos integrales de energía de arado específica, energía de deslizamiento específica y energía de corte específica. Se utilizaron granos abrasivos convencionales y súper abrasivos de Cubitrón. El corte con discos abrasivos de granos piramidales (cubitron) se utilizaron para la determinación de las componentes relativas de la energía específica consumida. Se encontró que la energía de arado específica es más sensible al cambio en la tasa de remoción de material en comparación con la energía de deslizamiento. Debido a los granos de Cubitrón de corte rápido y de forma precisa, la transición de deslizamiento a un régimen de corte específico fue tan rápida para algunos materiales que la magnitud de la energía de arado resultó ser insignificante. Sin embargo, la implementación del modelo para algunos materiales demostró que la ausencia o presencia de energía de arado también depende de la tasa de material removido. Por último se presenta el desarrollo de un modelo de grano de corte que permitirá estudiar la relación de compresión de la viruta que no es posible caracterizar a través de un solo grano de corte en el corte de metales mediante discos abrasivos delgados. Este último desarrollo es el comienzo de un estudio de la formación de viruta en la zona primaria de corte de un grano abrasivo. Esta investigación proporciona una máquina y una metodología para caracterizar el corte con disco abrasivos, disponibles comercialmente, en términos del parámetro Energía Específica Consumida. Enginyeria mecànica, fluids i aeronàutica

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Mashloosh, K. M. "Abrasive wear with particular reference to digger teeth." Thesis, Brunel University, 1987. http://bura.brunel.ac.uk/handle/2438/7883.

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Abrasive wear occurs when a contact associated with stress between a metal surface and a herd particle (frequently of mineral origin) leads to friction between the two. In a very wide range of industrial applications, abrasive wear is the main reason for component and equipment repair or replacement. In most of these applications, especially those of earth moving, construction and mining equipment, digger teeth are used to improve equipment performance. Digger teeth can be produced in different shapes and sizes (mainly by casting) and a wide range of materials are used. This project is concerned with both a field trial of the wear of digger teeth fixed to the front of a bucket used in a gravel pit, and also a laboratory investigation of abrasive wear mechanisms. It was found that the wear of digger teeth increased with increasing working hours, but the wear rate eventually decreased. The dimensions and shape of the front of the tooth changed and gravel removal became more inefficient. Plastic deformation and phase transformation were observed in the worn surfaces of the teeth. In the laboratory study, many parameters were investigated utilising a pin-on disc technique. Wear rate increases linearly with load and decreases with sliding distance. The effect of attack angle on abrasive wear showed that wear volume increases with increasing attack angle up to a certain value (90°) and then decreases. Corrosion increases the initial wear rate, and the amount of material removed in the wet corrosive test was higher than the corresponding dry test. It was difficult to reproduce the same results from the field trial in the laboratory because of the difference in the conditions in the two cases. Optical and scanning electron microscopy were used to study the worn surfaces, abrasive papers and wear debris. Different abrasive wear mechanisms were observed throughout this investigation. A cutting mechanism associated with spiral debris was observed during short pin-on disc tests and with higher attack angles. A ploughing action associated with plate-like debris was observed during longer tests and at lower attack angles. Fragmentation was observed in brittle materials.

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Zorcolo, Alberto. "Study of the interaction among abrasive particles, applicator and cleaning surfaces in household and tooth cleaning." Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.575867.

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Tooth cleaning and household cleaning are common tasks people undertake on a daily basis and they share significant analogies. Both rely on the combined action of a detergent - usually a fluid which may contain abrasive particles - and an applicator on a cleaning surface. While scientific information covers some of the aspects related to abrasive tooth cleaning, such as the main tooth wear mechanisms and the influence of dental care products on tooth cleaning and wear, household cleaning has not been covered in such detail. The aim of this work was to investigate abrasive tooth cleaning and abrasive household cleaning from a tribological perspective in terms of the interactions between human/applicator, applicator/abrasive particles and abrasive particles/substrate, in order to expand the knowledge on both subjects and gather information useful to improve the design of current cleaning products. A study has been carried out by means of a hand operated friction rig to measure the loads applied by human subjects while performing simulated abrasive cleaning operations in order to better understand the interaction between human test subject and applicator. The analysis investigated the loads applied during tooth cleaning processes and household cleaning processes, and the results (from 180g to 4230g for tooth cleaning tests and from 290g to 4.3Skg for household cleaning tests) helped Unilever in developing their friction analysis techniques. Particle entrainment into the contact area between the applicator and the surface has been analysed using two types of test rig- one with a unidirectional motion and the other a reciprocating motion - and an optical apparatus featuring a microscope and a camera for image and video capturing. The scratches produced by abrasive particles were studied with an optical microscope and a Scanning Electron Microscope in order to understand how they scratch the surface during abrasive cleaning processes. The investigation helped to gather information on how abrasive particles were trapped at the tip of the toothbrush filaments and between the cloth fibres and the observation of the scratched surfaces led to identify grooving abrasion as the main wear mechanism taking place in both abrasive tooth cleaning and household cleaning. A friction analysis of both tooth cleaning and household cleaning processes was carried out using the hand operated rig and a friction rig on which the applicators were mounted, to study the connection between the friction coefficient )l and the ability of the particles to remove material from the test surface. It was found that under the adopted experimental conditions, the lubricating action exerted by the carrying fluids in both tooth cleaning and household cleaning is mainly based on boundary lubrication. The values of the friction coefficient determined from the experiments ranged from around 0.20 (in wet condition, without abrasive particles) to 0.37 (in dry condition, without abrasive particles) for brushing tests, and from around 0.20 (in lubricated condition, with 5 urn Calcium Carbonate particles) to 0.66 (in dry condition, without abrasive particles) for cloth tests. The influence of the applied load, the particle size and concentration on friction coefficient was also investigated. Finally, a semi-empirical model was developed to estimate the rate of material removal during a simulated household cleaning process, in order to gather information useful to improve the ability of cleaning fluids to remove stain while reducing the damage to the cleaning surfaces. Results from the modelling were compared with data from reciprocating cleaning tests. Although the model often overestimated the amount of material removed from the test surface due to the assumptions made in order to simplify its implementation, it produced results of the same magnitude order of those obtained from material removal experiments within the ranges of applied loads, particle sizes and concentrations. lJ

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Knott, Ryan Christopher. "High temperature durability of metals for use in a particle heating receiver for concentrated solar power." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53117.

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An experimental investigation is presented on a novel High Temperature Falling Particle Receiver for Concentrated Solar Power (CSP) to quantify the extent of erosion of the receiver structural materials by the flowing particulate matter. The current receiver design uses a series of metal wire mesh screens to slow down the particulate flow through the receiver in order to increase their residence time thereby achieving the desired temperature rise within the receiver without the need for particulate recirculation. The solid particulates are gravity fed through the receiver where they absorb the incident thermal energy before flowing to a high temperature storage bin upstream of a heat exchanger where the heat stored in the particulate material is transferred to the working fluid for the power cycle. To assess the effective life of the receiver, this experimental investigation is undertaken. This thesis includes the development of an apparatus to test wire meshes under high temperature and particle abrasion conditions, and the presentation and analysis of these results.

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Catelas, Isabelle. "Characterization and biological effects of wear particles from metal-metal hip implants." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38163.

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Polyethylene wear particles have been the main culprit in initiating osteolysis and aseptic failure of conventional metal-polyethylene total hip arthroplasties. There has been a revived interest in metal-metal (MM) bearings, made of CoCrMo alloys; because of their very high wear resistance compared with conventional bearings. The work that forms the basis of this thesis attempts to examine MM bearings as one potential solution to the problem of osteolysis. The results provide important new information on MM particle characteristics and their effects on tissue, as well as the effects of their corrosion products (Co2+ and Cr3+) on macrophage response in vitro. An enzymatic protocol for isolation and characterization of metal particles was first developed in order to minimize particle changes due to the reagents. Metal particles isolated from a hip simulator and from human tissues around MM implants using this protocol were found to be mainly round to oval and more occasionally needle-shaped, extremely small (&sim;50 nm), and surprisingly, mostly chromium oxides. In vitro and in vivo run-in wear periods did not exactly correlate, but MM wear particles from both sources were quite similar at specific periods of comparison. Alloy composition and number of running cycles in vitro influenced the overall characteristics of the particles, although the observed differences were relatively small and would probably not induce a difference in the biological response. Tissue response to metal wear particles revealed the presence of IL-1beta and IL-6, two major inflammatory mediators implicated in periprosthetic osteolysis. There was also a high correlation between the amount of these cytokines and the quantity of metal particles. The amounts of cytokines decreased when the quantities of particles increased, most likely due to the high toxicity of the metal particles when present in larger quantities. There was more IL-6 than IL-1beta and TNF-alpha remained at low levels. Apoptosis was clearly observed in some tissues from the patients analyzed, but results were highly variable depending on the tissues analyzed. More patients would be necessary to complete this study on apoptosis. In vitro, Co2+ and Cr3+ ions induced the secretion of TNF-alpha, another major inflammatory mediator implicated in periprosthetic osteolysis, and macrophage mortality in a dose- and time-dependent manner. Co2+ was more toxic than Cr 3+. Macrophage apoptosis was predominant at 24h with both ions, and with the lowest concentrations at 48h. Necrosis was more prevalent with the highest concentrations at 48h. The implication of caspase-3 pathway was also identified in macrophage apoptosis. These results suggest how specific therapeutic treatments could modulate macrophage response to these ions.

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Thomas, Liam. "Oxidation catalysis on metal particles : a theoretical study." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/100725/.

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Oxygen adsorption and subsequent activation on unsupported gold, palladium and gold/ palladium particles were investigated using computational methods. For all particles studied the route to dissociation is via adsorption on (100) facets followed by dissociation into adjacent (111) facets, this indicates particle morphology plays a significant role in the activity of the particles towards oxygen. Calculated reaction barriers confirm 0.40 eV ,0.04 eV and 0.12 eV is required to dissociate O2 on Au38, Pd38 and Au6Pd32 respectively. Further studies conclude it is not feasible to dissociate more than one molecular oxygen on Au38 – this is due to a calculated secondary adsorption energy being significantly weaker than the 0.5 eV required to dissociate the second species (the secondary adsorption energy is the calculated adsorption energy of the second O2 molecule on a cluster with a pre-adsorbed species) This result is in sharp contrast to Pd38 and Au6Pd32 where full adsorption and dissociation of O2 occurs until particle saturation. Hydroxymethylfurfural – metal particle interaction is found to occur via the furan ring – (100)/ (111) junction. Adsorption energies are found to be greatest on sub nanometre Au13 and Pd13. For larger nanometre sized particles (Au38, Pd38 & Au6Pd32) the interaction with hydroxymethylfurfural can be up to 75 kJ mol-1 weaker than sub nanometre counterparts. Nudged elastic band calculations indicate a barrier to O-H activation in hydroxymethylfurfural to be 106 kJ mol-1 and 137 kJ mol-1 for Pd13 and Au13 respectively. The presence of pre adsorbed and dissociated oxygen destabilises the interaction with HMF however it can lower O-H activation barriers in the case of Pd13. The presence of a Pd10 particle on the surface of (0001) Fe2O was found to lower surface oxygen vacancy defect energies by as much as 1.12 eV. This defect energy can be reduced further by substituting the Pd atoms with Au. If Au10 is supported the oxygen vacancy defect energies are dramatically reduced (1.44 eV) even at defect site distances greater than 3 Å from the particle.

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Grygla, Michael S. "An investigation of methods to homogeneously entrain and suspend abrasive particles in a low pressure dental water jet /." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1693.pdf.

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Grygla, Michael Sean. "An Investigation of Methods to Homogeneously Entrain and Suspend Abrasive Particles in a Low Pressure Dental Water Jet." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1303.

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During the past several decades, the water jet cutting concept has developed from a novel concept into a well-accepted machine cutting tool. With the addition of abrasive particles and the improvement of high pressure pumps, the water jet stream is currently capable of cutting through metal, concrete, and composite materials. Water jet systems have been utilized at a wide range of different pressures. Research performed at Brigham Young University has revealed that low pressure water jets have the ability to cut human teeth. Experiments have shown that when abrasive particles are added to the water jet stream, an greater amount of tooth material can be removed at lower input pressures. Many different methods have been proposed to entrain and suspend particles in a high pressure water jet system. The abrasive particles can be entrained before the water is pressurized, while the water is being pressurized, or after the water jets stream exits the pressurized system. Each method has its advantages and disadvantages. Unfortunately, keeping abrasive particles homogeneously entrained and suspended in a water jet stream has proven to be difficult. Research at Brigham Young University has encountered similar problems. Researchers are attemping to place abrasive particles in a low pressure water jet stream, but have not been able to maintain a suspended homogeneous slurry. It is the objective of this research to investigate and suggest several possible methods to entrain and suspend abrasive particles into a low pressure water jet system intended for a dental cutting application. A broad review of methods to entrain abrasives in high pressure water jet systems was performed. A list of methods and concepts as possible solutions to entrain abrasives in a low pressure system has been generated. Product design principles were applied to screen, score, and rank these generated concepts to narrow down the list to the most viable concepts for BYU's low pressure dental water jet. Several tests and experiments were also performed to validate the suggested concepts and to provide useful information for future research. It is anticpated that one or more of these methods will be applicable for the proposed dental application as well as other similar applications.

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Midander, Klara. "Metal release from powder particles in synthetic biological media." Licentiate thesis, Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4039.

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Merolla, Luciano L. P. "Bioreactivity of metal components found in air pollution particles." Thesis, Cardiff University, 2006. http://orca.cf.ac.uk/55440/.

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A correlation was found between individual metal content and in vitro bioreactivity of particulate samples (in both ambient PM samples from Port Talbot and ROFA samples). Global factors such as particulate origin and seasonal variation were also identified as playing a role. A bioreactivity hierarchy of metals was then established: Fe2+Cu2+Fe3+VO2+Zn 2+ As3+=Pb2+=VO3- indicating the importance of oxidation state and suggesting a role for redox mechanisms. Strong synergistic effects were observed between Zn 2+ and various bioreactive metal ions (Cu2+, Fe 3+, VO2+) in vitro. However, this effect was limited to ions which could be readily reduced to a more active form (no synergy with Fe2+). In vivo, the surrogate water-soluble metal mixtures gave rise to a transient (7-14 day) metal ion concentration and valence dependent increase in lung:body weight ratio, protein levels (pulmonary oedema) and differential cell counts (inflammation) in a dose and time dependent manner. Light microscopy of the lung tissue revealed an acute phase response to the installation of the metal mixture with peripheral damage and inflammation followed by bronchiolisation, hyperplasia and increased collagen deposition in repair. There was evidence of organ-specific changes in RNA production in both the heart and lung. In both organs, the primary responses revolved around up regulating redox-specific, stress mechanisms and metabolism pathways, suggesting activation of xenobiotic biotransformation systems.

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Kirkland, Angus Ian. "High resolution electron microscopic studies of colloidal metal particles." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317850.

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Goddy, Biodun. "Electrokinetic concentration of aqueous dispersions of metal oxide particles." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46315.

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Heard, Christopher James. "Structural and electronic characterisation of sub-nanometre metal particles." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5542/.

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Electronic structure calculation methods, coupled with unbiased global optimization schemes are developed and employed, for the exploration of the energy landscape of subnanometre scale metallic clusters of noble metals. Structure prediction, along with statistical analysis of the potential energy surfaces for ultrasmall metallic and bimetallic particles of the coinage metals (Cu, Ag, Au) and platinum group metals (Pd, Pt) is undertaken, to determine favourable cluster geometries. Prediction of energetic and electronic properties, including charge distributions, electronic and configurational densities of states, binding, adsorption and mixing energies are made, in order to support the predictions of novel experimental work on a potential catalytic and optoelectronic systems. The environment of the particle is a focus, with surface-bound, ligated and gas phase clusters all considered, in addition to modelling of the adsorption of small molecules. Subnanoscale metal systems show promise in a range of reactive and electronic roles, and by producing accurate theoretical predictions of optical, binding and electronic properties, we contribute to the rational design of such new materials.

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Gibson, Fredrick W. Jr. "Stabilization of Submicron Metal Oxide Particles in Aqueous Media." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30645.

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An investigation into the parameters that define a good anchor block for a copolymer steric stabilizer was performed. The study focused on the effects of different functional groups on the adsorption properties of polymers. In addition, the effect of chain architecture as well as the impact of a hydrophobic end-group on polymer adsorption properties was determined. To complement the adsorption studies, a streaming potential instrument was built for use in measuring the adsorbed layer thickness of nonionic polymers on SiO2. The research concluded with an examination of the effect of thermally induced insolubility on adsorption of a hydrogen-bonding polymer. Functional group effects were studied by measuring the adsorption isotherms of poly(2-ethyl-2-oxazoline), PEOX, poly(ethylene oxide), PEO, poly(vinyl alcohol), PVOH, and poly(ethylene imine), PEI, which was modified such that a 1,3-butanediol substituent replaced its imine hydrogens, on SiO2, TiO2, and Al2O3. PEOX and PEO, relatively basic polymers compared to PVOH were observed to adsorb only on the most acidic metal oxide, SiO2. PVOH, however, was observed to adsorb on all three metal oxides, but to a lesser degree on SiO2 as compared to the more basic PEOX and PEO. These initial results were indicative of hydrogen-bonding mechanisms, a form of acid-base interaction. The most significant observation in the adsorption studies was that the linear hydroxyl modified PEI materials and their dendritic analogs adsorb on the metal oxides both above and below the i.e.p. This indicates that both electrostatic and hydogen-bonding mechanisms are driving the adsorption. The dendritic polymers, particularly a 4th generation dendrimer based on diaminopropane with a molecular weight of 16,640 g/mol adsorbed at a higher level when compared to the 41.3K g/mol PVOH and 30K g/mol PEOX. In addition to the dual adsorption mechanism, it was determined that the dendritic architecture appears to facilitate adsorption, as does the presence of the hydrophobic endgroup. The level of adsorption for all of the hydroxyl containing linear PEI and dendritic materials on the three metal oxides was high enough for them to be considered as anchor blocks in a copolymer steric stabilizer. The streaming potential instrument used to measure the adsorbed layer thickness on SiO2. Adsorbed layer thickness of PEOX Mw = 10K and 30K g/mol were measured at approximately 1nm and 4.4 nm, respectively. In the case of the PEOX Mw = 30K g/mol homopolymer, the measured layer thickness was higher than that for a 23K g/mol PEO homopolymer. The degree of polymerization of the PEO is approximately 525, while for the PEOX it was only 300. This result was not expected. Finally, adsorption of PEOX was studied at the cloud point to determine whether insolubility could promote adsorption, while hydrogen-bonding, the room temperature driving force for adsorption, would decrease. Adsorption isotherm measurements were performed at 72 Â°C, and 75 Â°C, as the cloud point of the 30K PEOX was determined to be 73 Â°C. It was apparent that the adsorption decreased as temperature increased, indicating that without hydrogen bonding, thermally induced insolubility does not drive adsorption. Ph. D.

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Rose, Klint A. "Microfluidic manipulation and detection methods for metal microbarcode particles /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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Milum, Kristen Marie. "In Situ Remediation of Heavy Metal Contaminated Sediments Using Emulsified Zero-Valent Metal Particles." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3305.

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Sediments can act as both a sink for pollutants and a source for aquatic contaminants. Natural and human disturbances of the sediments can release the contaminants to the overlying water where bottom dwelling, or benthic, organisms may be exposed through direct contact, ingestion of sediment particles, or uptake of dissolved contaminants present in the water. Dredging, the most common remediation technology for heavy metals, exacerbates this process. The in situ use of emulsified metal has been studied for its ability to pull heavy metals from aqueous solution and from saturated soils. It has proven successful in the laboratory with removal of lead, cadmium, copper, nickel, and uranium from aqueous solution and removal of lead and cadmium from saturated spiked soils. The use of zero-valent metal particles, particularly those of zero-valent iron (Fe0), as an in situ remediation technique, is currently undergoing evaluation. The basic mechanism for removal appears to be reduction of contaminant metals followed by the subsequent precipitation of their insoluble forms. This is accompanied by the oxidation of the zero-valent metal. In the case of iron, Fe0 undergoes oxidation to Fe2+ and then to the Fe3+ state. Particulate Fe0 has been shown to precipitate Cr6+ to Cr3+ and Pb2+ undergoes reduction to Pb0. Initially, zero-valent iron filings were used to reduce the metal contaminants, but it has been shown that smaller size iron particles, such as nano-scale iron, have higher initial reduction rates as well as a higher concentration of contaminant removal per mole of iron. Emulsion liquid membrane (ELM) technology has been employed as a remediation technique for the removal of metals from wastewater where extraction and stripping processes are performed in a single operation. The ELMs are made by forming an emulsion between two immiscible liquids, such as oil and water, and are often stabilized by a surfactant. We have attempted to demonstrate the application of the combination of these two technologies through the use of emulsified zero-valent metal (EZVM) to treat sediments with heavy metal contamination. Emulsions were prepared using vegetable oil, water, Span 85, and either nanoscale Fe, 1-3 [micro]m Fe, 4 [micro]m Mg, or a 20 wt % Fe-Mg mixture. The results presented in this study demonstrate that EZVM is a viable technique for in situ remediation of heavy metals in sediments. Laboratory scale studies have shown high levels of removal of lead and cadmium from solution using emulsified zero-valent iron. Additionally, the use of emulsified magnesium has shown the ability for high levels of removal of copper, cadmium, nickel, lead, and uranium from solution. A variety of solution matrices were also explored for a lead solution including seawater, the presence of complexing agents and humic acids. Small-scale laboratory studies have shown 65% removal of lead and 45% removal of cadmium from saturated, spiked soils. A bench scale test to demonstrate the applicability of this technique in the environment revealed similar results for the removal of lead. M.S. Department of Chemistry Arts and Sciences Industrial Chemistry

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Chabrol, Virginie. "Functionalized latex particles as substrates for metal mediated radical polymerization." Phd thesis, Université Claude Bernard - Lyon I, 2012. http://tel.archives-ouvertes.fr/tel-01012004.

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Le sujet de cette thèse consiste à incorporer une couronne de polymère hydrophile à la surface de particules de latex par amorçage et croissance en utilisant la polymérisation radicalaire contrôlée par transfert d'atome induite par les métaux. Les particules de latex, obtenues par, polymérisation radicalaire en émulsion ont été fonctionnalisées avec un " inimère ", monomère comportant une fonction halogénée capable de jouer le rôle d'amorceur dans l'étape de greffage. Cette étape de greffage a ensuite été effectuée en présence de CuBr2, PMDETA et d'un métal à valence zéro tel que le cuivre, àtempérature ambiante à partir de latex non post-purifiés (présence de tensio-actif et d'amorceur résiduels et à taux de solide élevés). Au cours du processus, l(incorporation de l'inimère et de la couronne hydrophile a été vérifée par ToF-SIMS (time-of-light secondary ion mass spectrometry), par FTIR et par l'étude des propriétés colloïdales des latex greffés.

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Da, Silva Adrien. "Laser-induced recoil pressure on metal drops and powder particles." Licentiate thesis, Luleå tekniska universitet, Produkt- och produktionsutveckling, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-83629.

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Additive Manufacturing became a major research topic and part of industrial production in the past years. Numerous techniques now allow to build 3D structures with a wide choice of materials. When it comes to processing of metals, a laser beam is often used as a heat source to melt either a wire or powder, where the trajectory of spatters and powder particles can be affected by the laser beam radiation. Laser beam irradiation is partly absorbed by the material, and is then converted to heat, which can cause melting and even vaporization. The vaporization of material induces a recoil pressure on the melt pool, which affects its geometry and dynamics. However, the effects of the recoil pressure on airborne objects such as drops and powder particles are still relatively unknown. Their different sizes and boundary conditions compared to a melt pool might affect their behaviour under high laser beam radiation. Therefore, this thesis aims at better understanding the effects of the recoil pressure on metal drops and powder particles, as well as their impacts on Additive Manufacturing processes, especially Directed Energy Deposition and Laser Metal Wire Deposition. In the three adjoined papers, high-speed imaging was used to observe (i) powder blown through a laser beam, (ii) drops falling in a laser beam, and (iii) drops detaching from a wire in a laser beam. The videos enabled to calculate the acceleration of powder particles and drops of different sizes, the density map of the powder stream, and the detachment direction of the drops. The experimental results were completed with theoretical calculations of thermodynamics, recoil pressure and surface tension. These studies allowed to conclude that the acceleration induced by the recoil pressure on a drop or a powder particle increases with decreased size. Moreover, the recoil pressure causes a slight deviation of the powder stream in Directed Energy Deposition that can induce a better powder focusing. The recoil pressure can also cause the disintegration of powder particles in the laser beam. Finally, it was shown that the recoil pressure can be used to detach drops on demand from a wire and accelerate them towards the substrate where they can be strategically deposited for building additive structures.

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Cuthbert, A. "Positronium binding to metal surfaces." Thesis, University of Sussex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382489.

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Bandyopadhyay, Mahuya. "Synthesis of mesoporous MCM-48 with nanodispersed metal and metal oxide particles inside the pore system." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=974056669.

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Uppenbrink, Julia. "Some aspects of the structure and dynamics of small particles." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241125.

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Fujiwara, Atsushi. "Controlling Adsorption Properties of Metal-Organic Framework Particles through Synthesis Protocols." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263694.

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Giarollo, Daniela Fátima. "Influência do metal de adição na resistência ao desgaste abrasivo de dois aços estruturais." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/178798.

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O presente trabalho teve por objetivo realizar ensaios de desgaste abrasivo em juntas soldadas pelo processo MAG, em dois aços estruturais de alta resistência e baixa liga utilizados no transporte ferroviário de minério, os quais apresentavam diferentes propriedades mecânicas. No aço de menor resistência (Aço A) foram utilizados os metais de adição AWS ER70S-G (Aço A-70) e AWS ER80S-G (Aço A-80), enquanto no aço de maior resistência (Aço B) os metais de adição AWS ER80S-G (Aço B-80) e AWS ER110S-G (Aço B-110). Os conjuntos soldados foram caracterizados quanto às suas microestruturas, dureza e resistência ao desgaste abrasivo em ensaios de degaste roda de borracha e ensaios de desgaste por deslizamento a seco e com adição de um meio corrosivo (NaCl 0,05M, água arti cial ). Os resultados obtidos a partir dos ensaios de desgaste roda de borracha mostraram que para o Aço A a junta soldada do Aço A-70 apresentou melhor resistência ao desgaste, enquanto para o Aço B a maior resistência ao desgaste foi obtida na junta soldada Aço B-110. Dos resultados dos ensaios de desgaste por deslizamento a seco, as zona afetada pelo calor de grãos grosseiros (ZAC-GG) foram as regiões que apresentaram a maior resistência ao desgaste. Das condições soldadas no Aço A, o metal base (MB) apresentou a menor resistência ao desgaste, entre os metais de solda (MS), o MS do Aço A-80 apresentou a maior resistência ao desgaste. No Aço B, o MS do Aço B-80 apresentou a menor resistência ao desgaste, e o MS do Aço B-110 apresentou a resistência ao desgaste similar ao MB. Foi observado um maior desgaste para as amostras que foram submetidas ao ensaio de desgaste por deslizamento com solução, comparativamente às amostras submetidas aos ensaios a seco, o que, de acordo com a literatura, está associado ao efeito sinérgico entre corrosão e desgaste. The present work had the objective perform abrasive wear tests on GMA welded joints in two high strength low alloy structural steels used in rail transport of ore, which presented di erent mechanical properties. The AWS ER70S-G and AWS ER80S-G wires were used in the lower strength steel (Steel A), whereas the AWS ER80S-G and AWS ER110S-G wires were used in the higher strength steel (Steel B). The welded joints were characterized in terms of their microstructures, hardness and abrasive wear resistance in dry sand/rubber wheel tests and sliding wear tests dry and with a corrosive medium (0.05M NaCl, arti cial water ). The results obtained from the dry sand/rubber wheel tests showed that for Steel A the welded joint with the wire AWS ER70S-G showed better wear resistance, while for Steel B the highest wear resistance was obtained with the AWS ER110S-G wire. From the results of dry sliding wear tests, the coarse grained heat a ected zone were the regions that presented the highest wear resistance. In Steel A, the base metal (BM) showed the least resistance, and between the weld metals (WM), the WM Steel A-80 showed the highest wear resistance. In Steel B, WM Steels B-80 showed the least wear resistance, while the WM Steels B-110 showed the wear resistance similar to BM. It was observed a higher wear for the samples that were submitted to the sliding wear test with solution, compared to the samples submitted to the dry wear test, which, according to the literature, is associated with the synergic e ect between corrosion and wear.

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Gilzad, Kohan Mojtaba. "Plasmonic Effect of Metal Nanoparticles Deposited on Wide-Band Gap Metal Oxide Nanowire Substrate." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-64762.

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The application of nanowires (NWs) in solar cells (SCs) is of great interest due to their new promising aspects established in nanoelectronics. Semiconductors associated with plasmonic metal nanoparticles (NPs) such as Silver (Ag), Gold (Au) and Copper (Cu), show enhanced performance in solid state light absorbing SCs owing to plasmonic characteristic of noble metal NPs. Plasmonic NPs presented a significant role in development of visible light harvesting for many applications such as photocatalytic materials, photodynamic in Surface Enhanced Raman Spectroscopy (SERS) and photovoltaics (PVs). Integration of plasmonic NPs in semiconductor materials have opened the routes to expand new PV systems with high efficiency light absorption. In this project, we introduce the synthesis ZnO and TiO2 NWs used as N-type semiconducting substrates and various methods for isolating plasmonic metal NPs, which are later deposited on the semiconducting substrates. Vertically aligned ZnO and TiO2 NWs arrays were grown on the fluorine-doped tin oxide (FTO) conductive glass substrates via hydrothermal method at low temperature and the plasmonic NPs were synthesized by wet chemistry procedures and finally decorated on the NW films by using electrophoretic deposition. The impact of metal NPs loaded on the ZnO and TiO2 NWs substrates was studied by means of UV-vis spectroscopy and Photoluminescence (PL) spectroscopy. The absorbance spectra of individual NPs were recorded. Remarkably, the reflectance spectra of produced samples presented an enhancement in light absorption of the substrates after uptake of NPs on the ZnO and TiO2 NWs. The optical properties of the as grown ZnO NWs films decorated with Ag NPs (I) in direct contact with substrate and (II) in presence of an Al2O3 insulating spacer layer have been investigated. Both systems exhibited an enhancement in the UV band-edge emission from the ZnO when excited at 325 nm. In contrast, the broad bend defect emission of the samples did not have a significant change compare to bare ZnO substrates. The observed results suggested that the ZnO and TiO2 NWs decorated with plasmonic nanoparticles can boost the optical properties of MOs NWs substrates and hence effectively enhance the separation of photoexcited electron-hole pairs and photo-conversion applications.

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Meldrum, Fiona C. "Nanoscale synthesis in organised organic assemblies." Thesis, University of Bath, 1992. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305061.

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Li, Xue. ""Cage" Nano and Micro-particles for Biomedical Applications." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS316/document.

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Les systèmes à délivrance de médicaments sont des technologies conçues pour administrer des molécules actives de façon optimisée afin d’améliorer leurs effets thérapeutiques tout en minimisant les effets secondaires. En effet, ces systèmes permettent une libération au niveau d’une cible thérapeutique. Les particules de type «cage» ont récemment attiré une attention particulière en raison de leur capacité accrue à (co)incorporer et à protéger des molécules actives vis-à-vis de dégradations in vivo. Les cyclodextrines (CDs) sont des exemples type de molécules "cage", possédant une cavité hydrophobe et une surface extérieure hydrophile. Nous avons élaboré tout d’abord des assemblages supramoléculaires à base de CDs d'environ 100 nm par une méthode douce consistant à mélanger deux solutions aqueuses de polymères neutres : 1) polymère de β-CD et 2) dextrane greffé avec la benzophénone, molécule invitée formant des complexes d’inclusion avec les CDs. La procédure de préparation « verte» en une seule étape rend la formulation attractive, malgré sa relativement faible capacité d’encapsulation (5%pds). Afin d'améliorer cete charge, nous avons élaboré des particules hybrides organiques-inorganiques (MOFs) à base de CDs. Avantageusement, les CD-MOF comportent non seulement des cavités de CD, mais aussi de larges pores engendrés lors l’auto-assemblage de CDs. Le lansoprazole a été incorporé avec succès (23%pds) dans les CD-MOFs et nous avons montré que chaque CDs était capable d’accueillir une molécule de principe actif. Cependant, l’inconvénient majeur des CD-MOFs est leur faible stabilité en milieu aqueux, limitant leur domaine d’application. Une modification de surface est apparue donc nécessaire pour améliorer leur stabilité. Notre stratégie a été d’incorporer les CD-MOFs dans des matrices d'acide polyacrylique (PAA). Des microsphères composites d’environ 650 nm ont été élaborées avec succès et ont permis une bonne stabilité et une libération prolongée sur plus de 48 h. Avantageusement, ces particules composites n’étaient pas toxiques in vitro même à des concentrations élevées. Ainsi, nous nous sommes orientés vers l’étude comparative de MOFs plus stables dans l’eau, à base de trimesate de fer. Les MIL-100 (Fe) (Material of Institute Lavoisier) figurent parmi les premiers MOF étudiés en tant que nanomédicaments (nanoMOFs). Ces particules, parfaitement stables dans l'eau, se dégradent dans des milieux contenant des phosphates en perdant rapidement leur caractère cristallin et leurs ligands constitutifs. De façon étonnante, nous avons constaté que malgré leur dégradation, ces MOFs conservent leur taille intacte. Une analyse approfondie basée sur la microscopie de Raman a permis d’obtenir des informations pertinentes sur la morphologie et la composition chimique de particules individuelles. Ainsi, il a été montré qu’un front d'érosion délimitait nettement un cœur intact et une coquillé inorganique érodée. Cependant, ni l’encapsulation ni la modification de surface des MOFs n’altérait leur intégrité. Enfin, nous avons étudié la co-encapsulation de deux molécules actives utilisées en combinaison (amoxicilline et clavulanate de potassium) dans les nanoMOFs stables à base de MIL-100 (Fe). Les antibiotiques ont été incorporées par imprégnation et chaque molécule s’est localisée préférentiellement dans un compartiment (large ou petite cage) corroborant parfaitement les simulations par modélisation moléculaire. De plus, il a été découvert, de manière surprenante, qu’un grand nombre de nanoMOFs se localisait au voisinage des bactéries (S.aureus) dans des cellules infectées. En se dégradant dans ces cellules, les nanoMOFs contenant les antibiotiques ont réduit de manière importante la charge bactérienne intracellulaire. Ces études révèlent le potentiel des particules de type «cage» pour une incorporation efficace de molécules actives et leur libération contrôlée et ouvrent de nombreuses possibilités d’application Drug delivery systems are engineered technologies to administer pharmaceutical ingredients to improve their therapeutic effects, aiming at minimizing their side effects by means of targeted delivery and/or controlled release. “Cage” particles recently drew special attention since they could act as “drug containers” which potentially load large amount of drugs, improve their stability and offer the possibilities to co-encapsulate synergetic drugs. Cyclodextrins (CDs) are typical “cage” molecules with a hydrophobic cavity and a hydrophilic outer surface. Taking advantage of the host-guest interactions between β-CD and benzophenone (Bz), CD based nanoparticles (CD-NPs) were the first formulation investigated. CD-NPs of around 100 nm were instantaneously produced by mixing two aqueous solutions of neutral polymers: 1) poly-CD containing β-CDs, and 2) Bz grafted Dex (Dex-Bz). The “green” and facile preparation procedure makes it attractive formulation, whereas its limitation lies on the low drug payloads (~ 5 wt%). In order to improve the drug loading capacity of CDs, porous CD based metal organic frameworks (CD-MOFs) were synthesized, which contain not only CD cavities, but also large pores built up by CDs self-assembly. Lansoprazole (LPZ) was incorporated in CD-MOF microcrystals (~ 6 µm) reaching payloads as high as 23.2 ± 2.1% (wt). Remarkably, each CD cavity was able to host a drug molecule, offering new opportunities for the use of CD-MOFs for drug delivery purposes. However, these particles disassembled in aqueous media, which limits their application for oral and intravenous administration. Surface modification is therefore necessary to improve their stability in water. The drug loaded CD-MOF nanocrystals (~ 650 nm) were successfully embedded in polyacrylic acid (PAA) polymer matrices. The composite microspheres exhibited spherical shapes and sustained drug release over a prolonged period of time (over 48 h). Drug loaded MOF/PAA composite microspheres were not toxic in vitro (cell viability ~ 90%) even at very high concentrations up to 17.5 mg/mL. MOF/PAA composite microspheres constitute an efficient and pharmaceutically acceptable MOF-based carrier for sustained drug release. However, the process of surface modification was complicated and lead to larger particles and reduced drug payloads. Water-stable MOFs are a novel type of hybrid particles, showing a high potential as drug carriers. Iron trimesate MOFs, namely, MIL-100 (Fe) (MIL stands for Material of Institute Lavoisier) was among the first nano-scaled MOFs used for drug delivery. These particles were stable in water but degraded in phosphate buffer saline (PBS) losing their crystallinity and constitutive trimesate linkers. However, it was discovered that they kept their morphology intact. A thorough analysis based on Raman microscopy was carried on to gain insights on both the morphology and chemical composition of individual particles. It was evidenced the formation of a sharp erosion front during particle degradation. Noteworthy, the MOFs did not degrade during drug loading nor surface modification. Co-encapsulation of two synergic antibiotics (amoxicillin and potassium clavulanate) in MIL-100 (Fe) nanoMOFs was achieved following a “green” procedure by soaking nanoMOFs in aqueous solutions of both drugs. Molecular modelling showed that each drug preferentially located in a separate nanoMOF compartment. Surprisingly, nanoMOFs were prone to co-localize with bacteria once internalized in infected macrophages. NanoMOFs acted synergistically with the entrapped drugs to kill intracellular S. aureus, in vitro. These results pave the way towards the design of engineered nanocarriers in which each component synergistically plays a role in fighting the disease. These studies unravel the potential of “cage” particles for efficient drug entrapment and controlled release and open numerous possibilities for applications

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38

Tanguay, Vincent. "Combustion of reactive metal particles in high-speed flow of detonation products." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32579.

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It is common practice to add reactive metal particles to high-explosive formulations in order to increase the total energy output. The present study is an effort to increase the understanding of metal particle combustion in detonation products. Aluminum and magnesium particles ranging from 2 to 100 μm are subjected to the flow of detonation products of a stoichiometric mixture of hydrogen and oxygen. Luminosity emitted from the reacting particles is used to determine the reaction delay and duration. It is found that the reaction duration increases as d^n with n ≈ 0.5, more consistent with kinetically controlled reaction rather than the classical diffusion controlled regime. Emission spectroscopy is used to estimate the combustion temperature, which is found to be well below the flow temperature. This fact also suggests combustion in the kinetic regime. Finally, the flow field is modelled with a CFD code and the results are used to model analytically the behaviour of the aluminum particles. Furthermore, a simple analytical model is developed to predict ignition of magnesium particles in nitromethane detonation products. The flow field is simplified by considering the detonation products as a perfect gas expanding in a vacuum in a planar geometry. This simplification allows the flow field tobe solved analytically. A single particle is then introduced in this flow field. Its trajectory and heating history are computed. It is found that most of the particle heating occurs in the Taylor wave and in the quiescent flow region behind it, shortly after which the particle cools. By considering only these regions, thereby considerably simplifying the problem, the flow field ca Il est maintenant courant d'ajouter des particules de métaux réactifs aux formulations d'explosifs pour augmenter l'énergie libérée. Cette étude vise une meilleure compréhension de la combustion de métaux dans les produits de détonation. Des particules d'aluminium et de magnésium de 2 à 100 μm sont exposées à l'écoulement des produits de la détonation d'un mélange d'hydrogène et d'oxygène. La lumière émise par les particules est utilisée pour déterminer le délai et la durée de la réaction. La durée de la réaction augmente selon d^n avec n ≈ 0.5. Ces résultats suggèrent un régime de combustion cinétique plutôt que le régime diffusif classique. La température de combustion est mesurée à l'aide de spectroscopie d'émission. La température mesurée est plus basse que celle de l'écoulement, ce qui est également cohérent avec un régime de combustion cinétique. Finalement, l'écoulement est modélisé avec un code Euler, dont les résultats sont utilisés pour modéliser analytiquement le comportement des particules. Dans un deuxième temps, un modèle analytique simple est développé pour prédire l'ignition de particules de magnésium dans les produits de détonation de nitrométhane. L'écoulement est simplifié en traitant les produits comme gaz parfaits, qui prennent de l'expansion dans le vide dans une géométrie planaire. Ces simplifications permettent de résoudre l'écoulement analytiquement. Ensuite, la trajectoire et la température d'une seule particule introduite dans l'écoulement sont calculées. La particule est chauffée principalement dans le "Taylor wave" et dans la région quiescente derrière celle-ci. En ne

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39

Gupta, Puneet. "Regenerable metal oxide Composite particles and their use in novel chemical processes." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1143225336.

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40

McCabe, Ryan M. "Solid hydrocarbon assisted reduction: a new process of generating micron scale metal particles." Thesis, Monterey, California: Naval Postgraduate School, 2015. http://hdl.handle.net/10945/45222.

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Approved for public release; distribution is unlimited The goal of this research is to test a central hypothesis: that gas species generated by the thermal and/or catalytically assisted decomposition of hydrocarbons in an inert atmosphere can reduce metal oxides to a metallic state. It is postulated that the decomposition releases gas phase radicals that can bind with oxygen in the metal oxides, forming volatile, stable oxides such as CO2 and water. This research consisted of thermally decomposing several types of solid hydrocarbon, including wax and low-grade coal, both with and without catalysts, in a nitrogen environment at >600 °C, located immediately below beds of micron scale particles of either NiO or Fe3O4. X-ray diffraction and scanning electron microscopy analysis showed, in support of the hypothesis, both metal oxides reduced to some extent. Nickel oxide reduced fully in many cases, but iron oxide never fully reduced and the extent of reduction was found to be a function of hydrocarbon, catalyst and temperature. These results suggest solid hydrocarbon assisted reduction (SHAR) with further testing and development may be a practical means to make sub-micron particles suitable in terms of price and quality for use in particle injection molding and 3D manufacturing of precision metal parts.

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41

Zhang, Yuan. "Optical spectra of molecular complexes and molecular junctions coupled to metal nano-particles." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17356.

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Diese Arbeit präsentiert eine vollständige quantenmechanische Beschreibung eines Systems bestehend aus einem Molekül und einem metallischem Nanopartikel (MNP) in der Gegenwart eines Strahlungsfeldes. Zuerst wird ein System aus einem Molekül und einem Gold-MNP betrachtet. Das Emissionsund Absorptionsspektrum zeigt viele scharfe molekulare Schwingungssatelliten auf einem breiten Plasmonmaximum. Eine Verstärkung der Schwingungssatelliten um drei Größenordnungen ist auf effiziente Absorption und Emission durch die MNP zurückzuführen. Dann wird ein System aus einer molekularen Kette mit einem Gold-MNP untersucht. Alle zuvor genannten Phänomene treten auch hier auf, jedoch werden die Schwingungssatelliten durch das Exzitonenband der molekularen Kette ersetzt. Anschließend wird ein Nano-Laser aus vielen Molekülen und einem Gold-MNP betrachtet. Die Moleküle werden durch inkohärentes optisches Pumpen angeregt. Dabei wird eine starke Plasmonanregung durch die gemeinsame Kopplung an die Moleküle erreicht. Die Photonenemission des Lasers zeigt, dass die Intensität ansteigt, während die Linienbreite schmaler wird. Die Korrelationsfunktion in zweiter Ordnung für die Photonen in Verbindung mit der schmaler Emission könnte dabei sogar einen Hinweis auf Lasing geben. Zuletzt wird eine Nanoverbindung aus einem Molekül und zwei sphärischen metallischen Elektroden betrachtet. Das Molekül wird durch den sequentiellen Ladungstransfer angeregt. Durch die Kopplung an die Moleküle werden die Elektrodenplasmonen angeregt. Die Photonenemission der Verbindung zeigt, dass die scharfen molekularen Schwingungssatelliten um das Tausendfache verstärkt werden. Anschließend ist ein System aus zwei pyramidalen Elektroden, die seitlich von zwei Gold-MNP eingeschlossen werden, untersucht. Hier können die Schwingungssatelliten einzeln verstärkt werden, indem der Abstand zwischen den MNP variiert wird. Wir zeigen auch, dass das Lasing in einer Verbindung aus vielen Molekülen theoretisch möglich ist. This thesis presents a unified quantum description of the combined molecule-metal nano-particle system in the presence of a radiation field. Firstly, a single molecule coupled to a gold nano-sphere is investigated. The emission and absorption spectrum show many sharp molecular vibrational satellites over one broad plasmon peak. The three orders of magnitude enhancement of the vibrational satellites is due to the great ability of the sphere to absorb and emit photons. Secondly, a molecular chain coupled to a gold nano-sphere is investigated. All the phenomena mentioned above appear also for such system, except that the vibrational satellites are replaced by the Frenkel exciton band of the molecular chain. Thirdly, a plasmonic nano-laser consisting of many dye molecules and a gold nano-sphere is considered. The molecules are initially excited by incoherent optical pump. The strong plasmon excitation of the sphere is achieved due to the concerted coupling with the molecules. The emission of the laser shows that the intensity is enlarged while the line-width is reduced. The second-order correlation function of photons together with the emission narrowing can be utilized to determine lasing operation. Finally, a nano-junction formed by a molecule and two spherical metallic leads is investigated. The molecule is excited through sequential electron transfer. The lead plasmons get excited due to the coupling with the excited molecule. The emission of the junction shows that the molecular vibrational satellites are about one thousand times enhanced by the lead plasmons. Then, a junction with two pyramidal metallic leads sandwiched by two gold nano-spheres is investigated. The simulations show that the molecular vibrational satellites can be selectively enhanced by varying the inter-sphere distance. It is also proved that the lasing can be realized by a junction with many molecules.

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Washim, Hossain. "Surface Enhanced Raman Spectroscopic Study of Some Functional Molecules Adsorbed on Noble Metal Nano Particles." Thesis, University of North Bengal, 2019. http://hdl.handle.net/123456789/2833.

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Liu, Yi. "Metal release of stainless steel particles in artificial lung fluid: complexation and synergistic effects." Thesis, KTH, Skolan för kemivetenskap (CHE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-33047.

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Numerous metal release data have been published by the Div. Surface and Corrosion Science and the AISI 316L stainless steel particles’ behavior in artificial lysosomal fluid (ALF). This study aims to evaluate the effect of chemical components in ALF on metal release from stainless steel particles with a bottom-up methodology. Two sizes of 316L stainless steel particles were used to assess the particle size influence on the metal release in detail. The results show that organic complexing agents e.g. lactate, tartrate and citrate are responsible for the high metal release rate in ALF. Correlations between the metal release rate and the number of carboxyl groups of the organic ligand were observed. Moreover, metal release data in this study indicates no synergistic effects in ALF solution, and continued research is on-going to study the synergistic effects further. No quantitative rules of iron, chromium and nickel release from the same stainless particles could be found which may indicate that these metals are released through different pathways e.g. diffusion or chemical dissolution. In different solutions with different chemical components, one or more metal release mechanisms dominate over others and make the metal release rate unpredictable.

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Mondin, Giovanni. "Functionalization of particles and selective functionalization of surfaces for the electroless metal plating process." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-156739.

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Electroless plating is a metal deposition technique widely used in the coating industry. It is the method of choice to plate substrates with complex geometries and nonconductive surfaces, such as polymers and ceramics, since it is based on a chemical reduction in solution rather than on an external electrical energy source like the electroplating method. Among others, examples of well-established applications are the electroless deposition of decorative metal coatings such as gold and silver, wear and corrosion resistant nickel coatings, particularly to coat drive shafts, rotors, and bathroom fixtures, as well as the electroless deposition of copper in electronic devices as diffusion barriers and conductive circuit elements. In the academic research, electroless plating is extensively used thanks to its low cost, simple equipment and versatility that allow rapid prototyping. Two common applications are the coating of small particles and the selective plating of flat surfaces. Metal coated ceramic particles are of enormous interest in many scientific fields, e.g. fluorescent diagnostics in biochemistry, catalysis, and fabrication of photonic crystals. Metal coated ceramic nanoparticles and microparticles are also gaining attention as potential candidates in the fabrication of higher quality metal matrix Composites, which is one of the applications addressed by this work. Metal coated ceramic particles are easier to integrate in metal matrix composites, avoiding aggregation caused by the low wettability of the particles by the matrix metal, and are potentially shielded from oxidation and undesired chemical reactions that take place at the interface between the particles and the metal Matrix. Electroless plating is an autocatalytic process, meaning that the deposited metal atoms catalyze the deposition of further metal. In order to achieve the first stable metal seeds on a surface, the latter has to be functionalized. Without this functionalization the metal ions in the electroless plating bath are not reduced or are simply reduced to metal nanoparticles in solution. The traditional activation step for nonconductive surfaces is performed by immersion of the substrate in palladium based solutions, which is very time-consuming and extremely expensive. In particular for nanoparticles, previous work showed that at least 1015 Pd atoms/cm2 are required for a uniform activation of a surface, meaning that in the case of nanoparticles with a surface area of about 100 m2/g are necessary 6.4 g of palladium for each gram of substrate. Assuming a price of about 150 €/g (laboratory scale) for palladium nanoparticles and palladium precursors used for surface activation, it results that the activation of 1 g of nanoparticles costs around 1000 €. Such costs are suboptimal considering the typical production scale, and therefore alternative functionalization methods are desired. In this work, new organic-based functionalization methods based on (3-mercaptopropyl)triethoxysilane to functionalize oxide particles, 3-aminopropylphosphonic acid to activate carbide particles and a substrate-independent method based on the bioinspired polydopamine are developed and investigated in detail, together with the respective electroless plating baths, which often have to be specifically tailored regarding the different reactivity of the different molecules and substrates. Furthermore, in the fabrication of metallic patterns on substrates by electroless plating, new, simple, and cost-effective activation and metal deposition processes are desired. In this work, two new methods are presented, one based on the printing of (3-mercaptopropyl)triethoxysilane by microcontact printing, the other based on the capillary force lithography of polymethylmethacrylate.

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45

Stahl, Sarah M. "An Investigation of Electrostatic Interactions Between Organically Functionalized Silica Particles, Surfaces, and Metal Ions." OpenSIUC, 2012. https://opensiuc.lib.siu.edu/dissertations/529.

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This research focuses on the electrostatic interactions between silica particles and either coated surfaces or metal ions. This work has two objectives: to begin a preliminary investigation into particle-surface systems that may be ideal for further investigation as a sensor and to investigate metal-ligand interactions for the potential use of metal ions to aid in the self assembly of silica particles. Silica particles with various organic functionalizations were synthesized from trialkoxysilane precursors using variations of the Stöber synthesis method, a well-known colloidal suspensions technique. The functional groups that were used in this work include mercaptopropyl (MPTMS), ethylenediamine (enTMOS), and aminopropyl groups (APTES). The aminopropyl functionalized particles were synthesized by varying the mol% of APTES in a tetraethoxyorthosilicate (TEOS) particle formulation. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) were used to analyze the particles for size, shape, and composition. Silica particles with all three functionalizations were used for the particle-surface study, whereas only MPTMS particles were used in the metal-ligand study. The coatings used for the particle-surface study were synthesized using standard sol gel chemistry with trialkoxysilane precursors as well. The functional groups used in this study include methyl (MTMOS) and aminopropyl groups (TEOS/APTES). Sol gel coatings incorporating carboxy and ammonium groups were also investigated but were not suitable for further study. FTIR was used to analyze the MTMOS and TEOS/APTES coatings. The adsorption of the MPTMS particles onto TEOS/APTES coatings and enTMOS or TEOS/APTES particles onto MTMOS coatings over time was monitored using fluorescence spectroscopy. Since silica particles are not fluorescent in the visible light range, a fluorescent dye was incorporated into the particles, either rhodamine (MPTMS particles) or pyranine dye (enTMOS, TEOS/APTES particles). The enTMOS and TEOS/APTES particles were protonated to increase the charge of the particles; the increased charge was verified with titration curves of the particles before and after protonation. Two types of MPTMS particles were used for the metal-ligand investigation. The first was the same MPTMS particles (without fluorescent dye) used in the first study. The second was 10 mol% MPTMS concentration in a TEOS particle formulation, similar to the APTES functionalized particles used in the first study. Lead(II) and zinc(II) solutions of varying concentrations was added to the particles, and the self assembly of the particles with no metal ions along with the various concentrations was analyzed using SEM. The nature of the metal-ligand binding was investigated using both mercaptopropyl functionalized particles by adding zinc(II), copper(II), silver(I), and lead(II) solutions to the particles in varying concentrations and analyzing the metal ion binding location using FTIR analyses.

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46

Benia, Hadj Mohamed. "Spatially resolved optical measurements on supported metal particles and oxide surfaces with the STM." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2008. http://dx.doi.org/10.18452/15862.

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In der vorliegenden Arbeit wurde mit Hilfe eines Photon-STM die Korrelation zwischen optischen Eigenschaften und der lokalen Morphologie an zwei unterschiedlichen Systemen untersucht. Hierfür wurden zum einem oxidgetragene Ensemble von Silber-Partikeln präpariert, wobei sowohl die Partikelform (Kuppel- und Scheibenform) als auch die deponierte Partikeldichte variiert werden konnte. Neben der Präparation solcher Partikel auf Al10O13/NiAl, konnten sphärische Silber-Kolloide geordnet, als auch ungeordnet auf HOPG aufgebracht und untersucht werden. Dabei zeigte sich, dass das Verhältnis von Höhen zu Breiten nicht nur einen signifikanten Einfluss auf die Mie-Resonanz des einzelnen Partikels hat, sondern auch die elektromagnetische Kopplung der Partikel in einem Ensemble stark kontrolliert. Die energetische Lage der Mie-Resonanz zeigt im Fall der kuppelförmigen Ag-Partikel eine starke Abhängigkeit vom Intepartikel-Abstand, was sich in einer Verschiebung zu höheren Energien für eine steigende Partikeldichte äußert. Eine solche Abhängigkeit konnte bei den Ensembles der scheibenförmigen Partikel nicht beobachtet werden. Des weiteren zeigte sich, dass, verglichen mit den ungeordneten Ensembles, die selbstorganisierte langreichweitige Ordnung der Silber-Kolloide auf HOPG nur einen schwachen Einfluss auf die energetische Position der Mie Resonanz hat.Das zweite hier untersuchte System sind dünne MgO Filme unterschiedlicher Dicken auf einem Mo(001) Substrat. Diese zeigen ein reichhaltiges Wachstumsverhalten, welches durch eine Differenz in den Gitterkonstanten von 5.3% begründet ist und erst ab etwa 25 ML zu einem flachen und defektarmen Film führt. Die so induzierte Spannung relaxiert bis zu einer Dicke von etwa 7 ML in einer periodischen Überstruktur die aus abwechselnd flachen und verkippten Ebenen an der MgO-Mo Grenzschicht hervorgeht. Für MgO Filme mit einer Dicke von etwa 12 ML werden dann Schraubenversetzungen, ausgedehnte verkippte Ebenen und Stufenkanten mit einer Orientierung entlang der Richtung beobachtet. Die optische Charakterisierung durch Feldemission von Elektronen aus der STM-Spitze in den MgO-Film wird dominiert von zwei Emissionsmaxima bei Energien von 3.1 eV und 4.4 eV. Die kontrollierte Nukleation von Gold Partikeln und die Erzeugung von Farbzentren im MgO Film erlaubten eine Zuordnung dieser Emissionen zu strahlenden Zerfällen von Exitonen an Ecken, Kinken bzw. Stufen des Magnesiumoxids. Solche Emissionsprozesse konnten allerdings nur unter Einstellungen beobachtet werden, bei denen ein gleichzeitiges Rastern der Oberfläche unmöglich ist. Bei moderaten Einstellungen war auch eine ortsaufgelösten Spektroskopie möglich, wobei dann neue Emissionsmechanismen beobachtet wurden. Dabei sind zwei Prozesse wesentlich; zum einen die Ausbildung von sog. Spitzen-induzierten Plasmonen im Bereich zwischen Spitze und dem Mo-Substrat, zum anderen strahlende Elektronenübergänge zwischen sog. Feldemissionsresonanzen, die sich im Spitze/MgO-Film System ausbilden. In this thesis, the correlation between the optical properties and the local morphology of supported silver nanoparticle ensembles and MgO thin films deposited on Mo(001) systems is explored by means of Photon-STM. In the first section, dome and disk shaped Ag nanoparticle ensembles with increasing density on an alumina film on NiAl(110) were analyzed as well as ordered and disordered ensembles of Ag nanocolloids on HOPG. The aspect ratio of the Ag nanoparticles was found to have a significant influence not only on the Mie plasmon resonance of a single particle, but also on the electromagnetic coupling within the nanoparticle ensembles. The Mie resonance in the ensemble of dome shaped Ag nanoparticles shows a strong dependence on the interparticle distance, where it shifts to higher energies with increasing particle density, due to destructive interference effects. In the disk-like Ag ensembles, however, the plasmon energy is independent of particle-particle separation. The long-range lateral ordering of size-selected Ag nanocolloids is found to induce a high dipole-dipole coupling within the ensemble. This is mainly reflected by the enhancement of the spectral intensity of the in-plane Mie mode, due to constructive coupling. However, ensembles with either well-ordered or disordered arrangements reveal no important difference in their optical properties, reflecting the weak influence of the long-range order in the particle ensemble. Thin MgO films with different thicknesses were grown on a Mo(001) surface. The stress resulting from the 5.3% lattice mismatch between the MgO(001) and the Mo(001) lattice parameters is found to control the surface morphology of the MgO film until thicknesses of around 25ML at which flat and defect-poor films are obtained. The relaxation of the stress induces a periodic network in the first 7ML of the MgO film, consisting of alternated flat and tilted mosaics. The presence of screw dislocations, steps oriented along the MgO directions, and tilted planes is observed when the MgO films are approximately 12ML thick. In addition, an increase of the MgO work function around these new surface features is revealed from STM spectroscopy. The photon emission induced by field-emitted electron injection from the STM tip into the MgO films is dominated by two emission bands located at 3.1eV and 4.4eV. To check the origin of these bands, further experiments, namely, nucleation of Au particles and creation of F-centers on the MgO surface, have been performed. The nucleation of Au particles at the low coordinated sites is found to quench the MgO optical signal, while the creation or annihilation of F-centers does not alter the MgO emission bands. The 3.1eV and the 4.4eV bands are therefore assigned to the radiative decay of MgO excitons at corner and kink sites, and step sites, respectively. Besides, spatially resolved optical measurements in the tunneling mode of the STM revealed different light emission mechanisms. These radiative processes are mainly related to tip-induced plasmons that form between the tip and the Mo support and to electron transitions between field-emission-resonance states in the STM tip-MgO film junction. The signal from exciton decays at corners and kinks of the MgO surface is however only observed at excitation conditions where the spatial resolution is already strongly reduced.

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Klingstedt, Miia. "Characterizing cavity containing materials using electron microscopy : A study of metal oxides, mesoporous crystals and porous material containing nanosized metal-particles." Doctoral thesis, Stockholms universitet, Institutionen för material- och miljökemi (MMK), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-64164.

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This thesis concerns the characterization of novel materials by utilizing electron microscopy techniques. The examined materials contain cavities with certain attributes that enables desired properties for applications such as gas separation, catalysis and fuel cells. The specimens concerned herein belong to the following groups of materials: Metal oxides in the Sb-W-Mo-O system; ordered mesoporous silicas and carbons; hollow spheres containing Au-nanoparticles; zeolite LTA incorporated with mesopores; metal organic frameworks doped with nickel. With scanning electron microscopy (SEM) and transmission electron microscopy (TEM) you get vast possibilities within the field of characterization. This thesis utilizes conventional electron microscopy techniques such as imaging, energy-dispersive spectroscopy and electron diffraction as well as reconstruction techniques, such as exit-wave reconstruction, electron tomography and electron crystallography. Furthermore, the sample preparation technique cross-section polishing has been used in conjunction with low voltage SEM studies. The scientific approach is to gain knowledge of nano-sized cavities in materials, in particular their shape, size and content. The cavities often have irregularities that originates from the synthesis procedure. In order to refine the synthesis and to understand the properties of the material it is required to carefully examine the local variations. Therefore average characterization techniques such as crystallography needs to be combined with local examination techniques such as tomography. However, some of the materials are troublesome to investigate since they to some extent bring limitations to or gets easily damaged by the applied characterization technique. For the development of novel materials it is essential to find means of overcoming also these obstacles. At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 6: Submitted.

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Panov, Nikita. "Microwave-Assisted Solvothermal Synthesis and Optical Characterization of M(RE)F4 (M – Alkali Metal; RE – Rare-Earth Metal) Nano- and Microscale Particles." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40590.

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Interest in rare-earth-doped crystalline materials, e.g., M(RE)F4 (M – alkali metal, RE – rare-earth metal), featuring unique optical properties such as light upconversion and downshifting is experiencing a surge due to the broad spectrum of applications that these photonic systems are facilitating. The development of reliable synthetic methods that grant rapid access to these materials is therefore of great importance. Microwave-assisted synthesis is appealing in this regard, because microwave radiation enables rapid and uniform heating of the reaction mixture and allows for rigid control of the reaction conditions, factors that facilitate the production of high-quality materials within minutes. Surprisingly, the investigation around microwave-assisted synthesis of M(RE)F4 materials featuring upconversion and downshifting luminescence is limited. Methods that have already been developed predominately target Na-based systems, despite the evidence that the Li-based analogues also display excellent optical properties. In fact, only a single microwave-assisted approach toward a nanoscale Li-based system has been reported to date, while to my knowledge, no report of a microwave-assisted synthesis of a microscale Li-based system existed prior to the commencement of the work presented in this thesis. The challenge lies in the fact that access to Li(RE)F4 is not easily achieved through a simple substitution of the alkali metal source in the established protocols that yield Na(RE)F4; rather, a complete re-optimization of the synthesis method is required. This particular challenge was successfully addressed in this work. Presented and discussed in Chapter 3 of this thesis is a rapid microwave-assisted solvothermal synthesis approach toward both upconverting and downshifting LiYF4:RE3+ microparticle systems. More specifically, it is detailed how the rigorous optimization of the reaction temperature/duration profile, initial reaction mixture pH, and ratio of the metal precursors was necessary in gaining control over the crystalline phase, morphology, and size of the microparticles under microwave-induced solvothermal conditions. Importantly, a materials growth mechanism involving the depletion of a Li-free crystal phase, followed by a particle ripening process is also proposed. Moreover, the versatility of the developed method is highlighted by showcasing how it can be extended toward the synthesis of other relevant Li- and Na-based M(RE)F4 nano- and microscale materials (i.e., LiYbF4, NaYF4, and NaGdF4) featuring upconversion luminescence. Lastly, potential challenges associated with microwave-assisted synthesis are discussed, and appropriate solutions are proposed. The upconversion and downshifting luminescence of the M(RE)F4 materials attained via the developed synthesis approach is investigated in Chapter 4. The first part of the chapter provides a general assessment of the characteristic luminescence generated by the M(RE)F4 materials featuring various RE3+ dopant systems. The second part of the chapter is devoted to a much more thorough single-particle investigation of the anisotropic luminescence behaviour exhibited by the LiYF4:RE3+ microparticles via hyperspectral imaging, polarized emission spectroscopy, and optical trapping. It is my hope that you, the reader, will find the work presented in this thesis stimulating from two vantage points – from the development of the most rapid microwave-assisted solvothermal synthesis of upconverting and downshifting M(RE)F4 nano/microscale materials reported to date, as well as from the utilization of specialized luminescence characterization techniques to provide fundamental insight into a seldom-considered luminescence property of crystalline materials such as LiYF4.

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Lu, Gang. "Thermal and photoinduced behaviour of palladium particles and transition metal carbonyls on TiOâ†2(110)." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296183.

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Bowen, James M. "Physicochemical characterization of discrete weapons grade plutonium metal particles originating from the 1960 BOMARC incident." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1384850163.

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