Dissertations / Theses on the topic 'Manufacturing ceramic materials'

Ceramic manufacturing is an expensive process with long lead times between the initial design and final manufactured part. This limits the use of ceramic as a viable material unless there is a large project budget or high production volume associated with the part. Ceramic stereolithography is an alternative to producing low cost parts through the mixing of a photo curable resin and ceramic particles. This is an additive manufacturing process in which each layer is built upon the previous to produce a green body that can be sintered for a fully dense ceramic part. This thesis introduces a new approach to ceramic stereolithography with a top mask projection light source which is much more economical compared to current vector scanning methods. The research goes through the design and development of a stereolithography printer prototype capable of handling ceramics and the testing of different mixtures to provide the best printing results with varying viscosities. The initial testing of this printer has created a starting point for top mask projection as an economical alternative to current ceramic manufacturing techniques.

The goal of this work is to develop and characterize a manufacturing process that is able to create metal matrix composites with complex cellular geometries. The novel manufacturing method uses two distinct additive manufacturing processes: i) fabrication of patternless molds for cellular metal castings and ii) printing an advanced cellular ceramic for embedding in a metal matrix. However, while the use of AM greatly improves the freedom in the design of MMCs, it is important to identify the constraints imposed by the process and its process relationships. First, the author investigates potential differences in material properties (microstructure, porosity, mechanical strength) of A356 — T6 castings resulting from two different commercially available Binder Jetting media and traditional 'no-bake' silica sand. It was determined that they yielded statistically equivalent results in four of the seven tests performed: dendrite arm spacing, porosity, surface roughness, and tensile strength. They differed in sand tensile strength, hardness, and density. Additionally, two critical sources of process constraints on part geometry are examined: (i) depowdering unbound material from intricate casting channels and (ii) metal flow and solidification distances through complex mold geometries. A Taguchi Design of Experiments is used to determine the relationships of important independent variables of each constraint. For depowdering, a minimum cleaning diameter of 3 mm was determined along with an equation relating cleaning distance as a function of channel diameter. Furthermore, for metal flow, choke diameter was found to be significantly significant variable. Finally, the author presents methods to process complex ceramic structure from precursor powders via Binder Jetting AM technology to incorporate into a bonded sand mold and the subsequently casted metal matrix. Through sintering experiments, a sintering temperature of 1375 °C was established for the ceramic insert (78% cordierite). Upon printing and sintering the ceramic, three point bend tests showed the MMCs had less strength than the matrix material likely due to the relatively high porosity developed in the body. Additionally, it was found that the ceramic metal interface had minimal mechanical interlocking and chemical bonding limiting the strength of the final MMCs.
Ph. D.

The goal of this work is to develop and characterize a manufacturing process that is able to create metal matrix composites with complex cellular geometries. The novel manufacturing method uses two distinct additive manufacturing processes: i) fabrication of patternless molds for cellular metal castings and ii) printing an advanced cellular ceramic for embedding in a metal matrix. However, while the use of AM greatly improves the freedom in the design of MMCs, it is important to identify the constraints imposed by the process and its process relationships. First, the author investigates potential differences in material properties (microstructure, porosity, mechanical strength) of A356 — T6 castings resulting from two different commercially available Binder Jetting media and traditional 'no-bake' silica sand. It was determined that they yielded statistically equivalent results in four of the seven tests performed: dendrite arm spacing, porosity, surface roughness, and tensile strength. They differed in sand tensile strength, hardness, and density. Additionally, two critical sources of process constraints on part geometry are examined: (i) depowdering unbound material from intricate casting channels and (ii) metal flow and solidification distances through complex mold geometries. A Taguchi Design of Experiments is used to determine the relationships of important independent variables of each constraint. For depowdering, a minimum cleaning diameter of 3 mm was determined along with an equation relating cleaning distance as a function of channel diameter. Furthermore, for metal flow, choke diameter was found to be significantly significant variable. Finally, the author presents methods to process complex ceramic structure from precursor powders via Binder Jetting AM technology to incorporate into a bonded sand mold and the subsequently casted metal matrix. Through sintering experiments, a sintering temperature of 1375 °C was established for the ceramic insert (78% cordierite). Upon printing and sintering the ceramic, three point bend tests showed the MMCs had less strength than the matrix material likely due to the relatively high porosity developed in the body. Additionally, it was found that the ceramic metal interface had minimal mechanical interlocking and chemical bonding limiting the strength of the final MMCs.
Ph. D.

Processing of ceramics has always been difficult due to how hard and brittle the material is. Fused Deposition of Ceramics (FDC) is a method of additive manufacturing which allows ceramic parts to be built layer by layer, abetting more complex geometries and avoiding the potential to fracture seen with processes such as grinding and milling. In the process of FDC, a polymeric binder system is mixed with ceramic powder for the printing of the part and then burned out to leave a fully ceramic part. This experiment investigates a new combination of materials, zirconia and acrylic binder, optimizing the process of making the material into a filament conducive to the printer system and then performing trials with the filament in the printer to assess its feasibility. Statistical analysis was used to determine optimal parameter levels using response surface methodology to pinpoint the material composition and temperature yielding the highest quality filament. It was discovered that although the mixture had adequate melting characteristics to be liquefied and printed into a part, the binder system did not provide the stiffness required to act as a piston to be fed through the printer head. Further studies should be completed continuing the investigation of zirconia and acrylic binder, but with added components to increase strength and rigidity of the filament.

Thesis (M.S.)--Worcester Polytechnic Institute.
Keywords: process based cost model; cost model; fuel cell; PBCM; multi-layer ceramics; sofc; solid oxide fuel cell. Includes bibliographical references.

In the diploma thesis dividing of ceramic materials is made, their bonds and other attributions, which define ceramic materials. There is also described how ceramic materials are manufactured and the thesis is including information about machining ceramic materials. In the experimental part sample of ceramic material R-S67K was machined by milling. During the experiment cutting forces were measured and roughness of surface after finishing, these data were finally evaluated.

Water is a critical resource to the human race, yet half the planet's population experiences water scarcity and 780 million people do not have access to clean water sources year round. For those with no other choice but to drink from contaminated water sources, they are at risk of contracting a broad range of diseases, most commonly diarrhoea, which the second largest killer of children under the age of five. Residents living in rural areas of developing countries are primarily at risk, lacking access to basic water infrastructure and medical services. To provide clean water to those in need requires culturally appropriate technology that is simple to construct and local made. Ceramic Water Filter Pots (CWFPs) consist of porous clay that acts as a filter, which is coated with silver nanoparticles creating a system capable of removing 99.995% of bacterial pathogens from drinking water and built in any community in the world. Working with a nationally recognized NGO based in Nicaragua, Potters for Peace (PfP), this study aimed to determine the limiting factors of production of CWFP by examining the materials used in three factories in Nicaragua, and the business model used in Guatemala based EcoFiltro. Field work was conducted in three factories in Nicaragua, and one factory in Guatemala. Visual observations of the production methods, testing protocols and business practices were documented visually and used to contrast the facilities production and businesses practices. Clay samples were collected from the Maysuta (n=2) and Filtron (n=3) factories to be analyzed at the University of British Columbia. The Atterberg limits were determined on the samples and X-ray diffraction analysis was used to determine the mineral makeup of the five samples and the percentage and type of clay in each. This study outlines the limits of clay composition, specifically montmorillonite, which can be used to manufacture ceramic water filters that make a viable ceramic filter, and contrasts the business models of two ceramic water manufacturers.
Applied Science, Faculty of
Graduate

One of the greatest obstacles to clinical translation of bone tissue engineering is the inability to effectively and efficiently vascularise scaffolds. This limits the size of defects that can be repaired, as blood perfusion is necessary to provide nutrient and waste exchange to tissue at the core of scaffolds. The goal of this work was to systematically explore whether architecture, at a scale of hundreds of microns, can be used to direct the growth of microvessels into the core of scaffolds. A pipeline was developed for the production of hydroxyapatite surfaces with controlled architecture. Three batches of hydroxyapatite were used with two different particle morphologies and size distributions. On sintering, one batch remained phase pure and the other two batches were biphasic mixtures of α-tricalcium phosphate (α-TCP) and hydroxyapatite. Sample production methods based on slip casting of a hydroxyapatite-gelatin slurry were explored. The most successful of these involved the use of curable silicone to produce moulds of high-resolution, three dimensional (3D) printed parts with the desired design. Parts were dried and sintered to produce patterned surfaces with higher resolution than obtainable through conventional 3D printing techniques. Given the difficulties associated with the structural reproducibility of concave pores architectures in 3D reported in the literature, in this work, a 2.5D model has been developed that varies architectural parameters in a controlled manner. Six contrasting architectures consisting of semi-circular ridges and grooves were produced. Grooves and ridges were designed to have widths of 330 μm and 660 μm, with periodicities, respectively, of 1240 μm and 630 μm. Groove depth was varied between 150 μm and 585 μm. Co-cultures of endothelial cells and osteoblasts were optimised and used to grow microcapillary-like structures (referred to as "microvessels") on substrates. Literature shows that these precursors to microcapillaries contain lumina and can produce functional vasculature, demonstrating their clinical promise. The effects of the composition and surface texture of grooved samples on microvessel formation were studied. It was found that surface microtopography and phase purity (α-TCP content) did not affect microvessel formation. However, hydroxyapatite architecture was found to significantly affect microvessel location and orientation. Microvessels were found to form predominantly in grooves or between convexities. Two metrics - the degree of alignment (DOA) and the degree of containment (DOC) - were developed to measure the alignment of endothelial cell structures and their localisation in grooves. For all patterned samples, the CD31 (an endothelial cell marker) signal was at least 2.5 times higher along grooves versus perpendicular to grooves. In addition, the average signal was at least two times higher within grooves than outside grooves for all samples. Small deep grooves had the highest DOA and DOC (6.13 and 4.05 respectively), and individual, highly aligned microvessels were formed. An image analysis method that compares sample X-ray microtomography sections to original designs to quantify architectural distortion was developed. This method will serve as a useful tool for improvements to architectural control for future studies. This body of work shows the crucial influence of architecture on microvessel self-assembly at the hundreds of micron scale. It also highlights that microvessel formation has a relatively low sensitivity to phase composition and microtopography. These findings have important implications for the design of porous scaffolds and the refinement of fabrication technologies. While important results were shown for six preliminary architectures, this work represents a toolkit that can be applied to screen any 2.5D architecture for its angiogenic potential. This work has laid the foundations that will allow elucidating the precise correspondence between architecture and microvessel organisation, ultimately enabling the "engineering" of microvasculature by tuning local scaffold design to achieve desirable microvessel properties.

Polymeric materials have provided pathways to products that could not be manufactured otherwise. A new technology which merges the benefits of ceramics into these polymer products has created materials ideally suited to many different industries, like food packaging. Nano Scale Surface Systems, Inc. (NS3), a company which coats polymers with ceramic oxides like SiO2 through a process known as plasma enhanced chemical vapor deposition (PECVD), was interested in the feasibility of an in line measurement system for monitoring the deposited films on various polymer products. This project examined two different coated polymer products, polyethylene terephthalate (PET) beverage containers and biaxially oriented PET food packaging, commonly known as plastic wrap in an effort to determine the feasibility of an ellipsometry based measurement system for NS3’s purpose. Due to its extensive use in the semiconductor industry for monitoring films deposited on silicon, a measurement systems known as ellipsometry, adept at monitoring the thickness and refractive index of thin films deposited on various substrates, appeared to be an ideal system for the measurement of ceramic oxides deposited on various polymer substrates. This project set out to determine the feasibility of using an ellipsometry based measurement system to monitor ceramic films, specifically silicon oxides (SiOX), deposited on polymer products. A preliminary experiment determined linearly polarized light could induce a discernible change in polarized light traversing a coated beverage container relative to an uncoated container. However, the experiment lacked repeatability due to the measurement apparatus’ cheap setup, prompting the construction of a null (conventional) ellipsometer for further research. The curved surface of the beverage containers under study unnecessarily complicated the feasibility study so further research examined PECVD SiOX on biaxially oriented PET instead. Characterization of the PECVD SiOX-PET material was divided into three experiments, with the first two analyzing the SiOX film and PET substrate separately while the third analyzed them together. To assist with the characterization experiments, NS3 provided samples, both SiOX coated and uncoated, of various deposition thicknesses on silicon and biaxially oriented PET substrates. Null ellipsometry was used in conjunction with spectroscopic reflectometry to characterize the refractive index and thickness of the deposited films. The combined measurement systems found the refractive index of the deposited SiOX films to be between 1.461 and 1.465. The measured thicknesses resulting from the two measurement systems coincided well and were usually 10-20 nm thicker than the predicted thicknesses by the deposition processing parameters. Abeles’ method and monochromatic goniometry were attempted; however, the results had to be discarded due to irrecoverable errors discovered in the reflectance measurement. X-ray photoelectron spectroscopy (XPS) data provided by NS3 showed the deposited SiOX films to be homogeneous with stoichiometries between 2.15 and 2.23. Characterization of the uncoated biaxially oriented PET required numerous measurement systems. From spectroscopic transmission, trirefringent anisotropy was discovered, intertwined with thickness variations in the PET foil. Goniometry measurements displayed distinct interference curves resulting from rear interface reflections interfering with front interface reflections from the PET sample. Subsequent goniometric models produced multiple solutions due to an unknown optical phenomenon, probably scattering, which degraded the reflection measurements. However, a combined measurement technique utilizing goniometry and differential scanning calorimetry (DSC) determined the refractive indices of the polymer to be NX = 1.677, NY = 1.632 and NZ = 1.495 with a thickness of 11.343 μm and a volume fraction crystallinity of 35-41%. Utilizing the measured refractive indices, ellipsometric models produced only an adequate fit of the measured data due to the presence of depolarization caused by non-uniform PET thickness and scattering resulting from embedded microscopic crystallites. The majority of the error in the ellipsometric data was observed in the Δ measurement. XPS measurements of SiOX deposited on polypropylene (PP) provided by NS3 showed a heterogeneous interphase layer between the deposited oxide and the polymer substrate where the composition of the layer was continually changing. A similar region, which violates the homogenous assumption the ellipsometric model relied on, was anticipated for the SiOX-PET samples under investigation. The use of an effective medium approximation (EMA) to represent the interphase region was attempted, but failed to provide a decent model fit of the measured data. Depolarization and high optical anisotropy caused by the polymer substrate in combination with a heterogeneous interphase region and the effects of the deposited SiOX layer all interacted to prevent ellipsometric modelling of the null ellipsometry measurements conducted. Goniometry measurements were conducted on the thickest deposited SiOX film (approximately 100 nm) which allowed for the refractive index of the film to be approximated through Abeles’ method (n = 1.46); however the validity of this approximation was questionable given the presence of interference fringes resulting from interference between reflections at both the front and rear interfaces of the material. From the experiments conducted, it was concluded that null ellipsometry with conventional ellipsometric models could not adequately measure a SiOX film’s refractive index or thickness when deposited on biaxially oriented PET. The reasons for the failure were interactions between multiple sources of error which led to both measurement errors and inaccurate model assumptions. Use of generalized ellipsometry, possibly with spectroscopic ellipsometry, may overcome the failures of conventional ellipsometry when studying this complex optical material.

Copper zinc tin sulfide (Cu2ZnSnS4 or CZTS) kesterite compound has attracted much attention in the last years as a new abundant, low cost, and environmentally benign material with desirable optoelectronic properties for Photovoltaic (PV) thin film solar cell applications. Among various synthesis routes for CZTS thin films, sol-gel processing is one of the most attractive routes to obtain CZTS films with superior quality and low cost. In this study, sol-gel sulfurization process parameters for CZTS thin films were systematically investigated to identify the proper process window. In addition, temperature dependent Raman spectroscopy was employed to monitor the CZTS sulfurization process in real time and gain fundamental information about the phase formation and degradation mechanisms of CZTS under the relevant processing conditions. It was found that CZTS thin films with different Cu stoichiometry can be prepared using parts-per-million (ppm) level of hydrogen sulfide (H2S) gas as opposed to high percentage level of H2S (e.g., ≥ 5%) in all previous studies. Samples sulfurized at lower temperatures of ~350°C and 125°C revealed the formation of CZTS phase as confirmed by XRD, Raman micro-spectroscopy, and sheet resistance measurement. Local EDS analysis indicates that CZTS films prepared at those low temperatures have a near-stoichiometric composition and are sometimes accompanied by the formation of Cu2-xS phase(s). Also, stoichiometric and Cu-rich precursor solutions tend to yield CZTS samples with better crystallinity and superior optical properties compared with the Cu-deficient solution. Moreover, in situ Raman monitoring of phase formation of CZTS material was carried out from room temperature up to 350°C in a 100 ppm H2S+4%H2+N2 gas mixture. The results showed that CZTS phase formed in about 30 min via a direct reaction between the metal oxide precursor film and the H2S-H2 gas mixture at an intermediate temperature of 350°C and remained stable upon extended exposure. In comparison, at a lower temperature (170°C), the oxide precursor film had to be reduced first (e.g., in 4% H2/N2 forming gas) and then the CZTS phase emerged. However, continued sulfurization at a lower temperature (e.g., 170°C) led to the disintegration of CZTS and the formation of CuS impurity, which remains stable upon cooling the sample down to room temperature. Furthermore, results of in situ Raman monitoring of CZTS films in an oxygen-rich atmosphere at elevated temperatures up to 600°C suggested that CZTS oxidizes first at ~400°C to form tin oxide (SnO2) and binary sulfides of mainly copper sulfide (Cu2-xS) and zinc sulfide (ZnS). Then, at temperatures higher than 400°C, the remaining sulfides oxidize to form zinc oxide (ZnO). The outcomes of the current study set the directions for optimizing the CZTS film structure and stoichiometry toward developing low cost and high-performance CZTS solar cells in future.

La fabrication directe de moules en matériaux réfractaires est une opération difficile, délicate et couteuse. C’est pourquoi nous avons cherché à développer un procédé de fabrication assistée par ordinateur (FAO) d'objets en trois dimensions. Ce procédé de prototypage rapide comprend deux étapes: la première est la fabrication de l'objet en agglomérant couche par couche une pâte céramique avec un laser CO2; la deuxième consiste en un frittage à température élevée afin de compléter cette opération et d'améliorer les propriétés mécaniques. Nous avons étudié des matériaux adaptés à ce procédé. La pâte céramique retenue se compose d'une poudre d'alumine et d'un liant qui est du silicate de sodium aqueux. Le mécanisme de la solidification de cette pâte pendant le balayage par le faisceau laser et celui du frittage ont été étudiés. La pièce finale est un composé d'alumine et de néphéline. Nous avons également étudié la résistance mécanique et la rugosité de surface des objets obtenus. Ceci permet d'optimiser les paramètres du procédé à savoir la puissance du faisceau laser, la vitesse de balayage, l'épaisseur d'une couche et l'intervalle entre deux passages du faisceau. Il n'y a cependant pas de corrélation simple entre les propriétés mécaniques et les paramètres du procédé. La résistance à la flexion des objets est supérieure à 10 MPa et cette valeur est comparable à celle des autres procédés de prototypage rapide des céramiques

Les techniques d’élaboration de matériaux par fabrication additive (FA) sont en plein essor [1]. Elles permettent de fabriquer des pièces par ajout de matière, en opposition avec les techniques traditionnelles par soustraction de matière (usinage). Il existe à l’heure actuelle de nombreux procédés de FA, adaptés à différentes applications : fusion ou frittage par faisceau d’électrons ou par laser, dépôt de matière direct ou en lit de poudre… Ces procédés ont été bien développés pour des matériaux polymères puis métalliques. Des techniques de FA de matériaux céramiques via des polymères chargés ont également vu le jour, mais celles-ci nécessitent des traitements postérieurs (cycles de déliantage, frittage) [2]. Les matériaux céramiques denses sont encore peu développés en fabrication additive en raison de la fissuration de ces matériaux lors de leur élaboration.La technologie CLAD (Construction Laser Additive Directe), développée par IREPA-LASER, permet la fabrication de pièces par dépôt de matière fondue. Le matériau sous forme de poudre est acheminé via une buse laser et projeté dans le faisceau. Il est ainsi porté à la température de fusion. La fusion successive de plusieurs couches permet l’obtention de la pièce. Cette technique, en plus de n’utiliser que la matière nécessaire (contrairement aux techniques de fabrication par lit de poudre), permet la fabrication de pièces de grandes dimensions, voire en multi-matériaux. Cette technologie est, pour l’heure, dédiée aux matériaux métalliques.L’objet de ce sujet de thèse, en partenariat entre l’ONERA et IREPA-LASER dans le cadre du projet inter-Carnot CLADIATOR, est d’étudier la FA de matériaux céramiques denses par le procédé CLAD®. Cette étude porte ainsi sur le procédé dans son ensemble, des matières premières aux pièces finales, en passant par l’adaptation du moyen de fabrication aux contraintes spécifiques liées aux matériaux céramiques.Les matières premières exigent d’être adaptées au procédé ; les deux principales difficultés étant la coulabilité de la poudre, nécessaire pour son acheminement dans la buse, et l’absorption de la source laser par le matériau pour sa montée en température. En parallèle de la caractérisation des matières premières (granulométrie, MEB, dilatométrie, DRX…), des essais d’atomisation par séchage seront effectués pour optimiser la coulabilité des poudres [3]. Ce procédé d’atomisation permet d’obtenir des poudres sous forme d’agglomérats sphériques de plus petites particules ; leur forme est régulière, mais elles restent poreuses. L’ajout de dopants sera étudié pour améliorer l’absorption du signal, en adéquation avec une éventuelle adaptation du laser. Les matériaux considérés sont l’alumine, la zircone ainsi que des compositions eutectiques d’alumine-zircone.La principale difficulté de ce sujet réside dans la sensibilité à la fissuration des matériaux céramiques, en raison du fort gradient thermique induit par le chauffage local du laser et le refroidissement de la pièce. Des solutions de chauffage de la pièce et/ou du matériau avant et après le dépôt seront étudiées pour limiter les contraintes thermomécaniques subies par le matériau [3,4].La machine devra également être modifiée pour supporter les températures élevées nécessaires à l’élaboration de céramiques (températures de fusion et dispositif de pré/post chauffage). L’étude et l’optimisation de ces solutions seront effectuées à l’aide de modélisations multi physiques sur le logiciel COMSOL en collaboration avec IREPA-LASER.Enfin, l’influence du procédé d’élaboration sur l’état des pièces réalisées sera étudiée grâce à des caractérisations microscopiques, mécaniques, thermiques…
This work, in partnership between the ONERA Materials and Composite Structure Department (DMSC) and IREPA Laser within the CLADIATOR project, is based on the study of direct additive manufacturing of dense ceramic materials by direct melt deposition (also known as laser cladding) process. This process enables high dimensions or even multi-materials part manufacturing.It will deal with the adaptation of raw materials (ceramic powders) to the existing machine, especially in the case of powder flowability and optical absorption. Indeed, the powder flowability enables its transportation up to the laser nozzle, while the optical absorption of the laser signal is necessary to allow its melting.In parallel, the existing machine also needs to be adapted to ceramic materials : the main difficulty of this work will be the occurence of cracks during the manufacturing. This phenomena is due to the local heating by the laser and the materials brittleness. That’s why some secondary heating solutions, before or after the melt, will have to be defined to decrease the thermal gradient in the material while processing. Those solutions will be discussed between Onera and Irepa Laser, based on FEM simulations established with COMSOL Multiphysics software.Finally, the elaboration process influence on the manufactured ceramics parts will be investigated with microscopy, mechanical and thermal characterization

A l'aide d'une methode originale de microsoudure par ultra-sons, nous placons un fil-electrode de part et d'autre d'un joint de grains, permettant ainsi d'effectuer toutes les etudes experimentales de ce dernier. En se basant sur les differentes caracteristiques i(v) mesurees de plusieurs joints, nous proposons 3 modeles de simulation relatifs a la caracteristique i(v) globale d'une varistance. Les calculs mettent en evidence l'influence du pourcentage optimal de "bons joints" sur les proprietes electriques (coefficient de non-linearite, courant de fuite, tension de seuil, regime de saturation) des varistances zno a basse tension de seuil. Realisation et caracterisation de varistances a gros grains (100 um-200 um) a partir d'une technique de grains germes

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Global warming and the high energy demands of fossil fuel in industries have led governments to implement legislation aimed towards developing more energy efficient and sustainable processes. In the brickwork industry, the burning of coal and natural gas provides the energy to fire clay bricks in the 900-1200 oC range into high quality building materials. Microwaves powered by renewable energy sources have been suggested as a sustainable alternative to fossil fuels. Microwave heating has been considered a promising technique for the processing of clays due to the potential energy consumption and carbon footprint reductions, and for its volumetric heating nature, which enables the fast and uniform heating of a load. This could result in improving the mechanical properties of the fired products. The aims of this project were to develop an understanding of how microwaves interact with clays in order to show whether they could be used to fire clay-based building materials, and to understand how this could be achieved and the parameters that affect it. The composition of Danish clays was quantified, i.e. quartz, calcite, albite, orthoclase, kaolinite, montmorillonite and muscovite, and their thermal evolution was studied across the firing range. The dielectric properties of clays were measured at 912-2470 MHz and 20-950 oC in order to investigate the microwave/clay interaction, assess the effects of changing composition, temperature, frequency and material's density on their potential for microwave processing, and provide critical information on the design and scale up of this technology. Relating the mineralogy of a material and its evolution during heating to changes on the dielectric property trends, and thus microwave processability, was examined for the first time in this thesis. Insight into the influence of individual components on the potential for microwave heating was gained from an analogous study on clay constituents. While the dielectric constants of clays were found to be relatively stable during heating, their loss factors fluctuated with temperature. Free and physically bound water were the dominant dielectric species near room temperature, while their removal halved the loss factors until 350 oC. Beyond this temperature, a steady increase in the loss factors concurred with the mineral dehydroxylations. The loss factors sharply rose beyond 800 oC due to sintering effects, while calcite decomposition partially counteracted this growth. Montmorillonite and muscovite were the most microwave absorbing mineral species due to their water affinity and interlayer cation content, enabling the microwave treatment of the whole clay. On the other hand, a frequency shift from 2470 MHz to 912 MHz resulted in a loss factors increase. This is mainly due to the frequency shifting towards the dipolar dispersion area of physically bound water and the zone in which ionic conductivity heating effects dominate. Mixing rules were used to relate each single mineral to dielectric property variations, and thus rapidly gain knowledge of the microwave processability of any clay across the firing range based on its composition. Böttcher model provided accurate estimations when compared to experimental measurements, and with the same degree of uncertainties at the 912-2470 MHz frequencies and 0.56-0.37 void fraction ranges. The model was expanded for different compositions with clays from Spain, England and Netherlands. This was the first time that mixing rules were successful in estimating mixtures of more than three constituents. A microwave system was developed with the aim of firing clay products of comparable quality to conventional specimens. The basis of design focused on maximising the thermal uniformity of the clay load. The process design steps involved remodelling the clay load, building heat transfer models of the load, carrying out trials to study whether clays behave as expected from their dielectric properties, i.e. volumetric or selective heating, minimising thermal gradients, and assessing alternative methods for the control of the holding stage. Microwave firing cycles manufactured clays with a thermal uniformity at the height of firing of 1050±55 oC and reduced processing times to < 3 h. This is 92% faster than in brickworks, where conventional samples could not match the heating rates without cracking. High temperature (>800 oC) mineral reactions went unfinished due to the reduced holding time of the microwave treatment (30 min), which resulted in dimmer surface colorations. Enhanced thermal uniformity and reduced time for densification resulted in specimens with a 12% higher compressive strength, 38% larger water absorption and 7% higher void fraction. Clay samples three times as big were fired to gain an insight into the scale up of the technique. A tighter process control and higher reproducibility were reported, which is promising for potentially allowing longer holding times in scaled up processes, but the product quality improvement did not change. Looking into an industrial scale up, further work would be required to assess possible design concepts, and an optimal microwave firing process may require complete redesign of the furnace configuration, where several challenges need to be considered, such as brick arrangement, power availability and applicator size and shape. For the purposes of assessing the possible economic and environmental impact of implementing microwave clay firing at industrial scale, one of the most straightforward designs, i.e. retrofitting of an industrial tunnel kiln for microwave processing, was considered. Although energy expenditures would decrease from 11.6 GJ fuel/h to 6.1 GJ electricity/h when using a microwave system for the same throughput, the higher cost of electricity and microwave equipment over conventional burners made the conventional technique more economically feasible. The substitution of natural gas by electricity powered by green energy sources resulted in carbon footprint reductions of >95%, and agreed with the energy policies of numerous countries and supranational organisations worldwide.

During firing, the deformation of ceramic articles under their own weight may be problematic particularly in the sanitary ware industry where articles are large. A model has been developed that predicts the viscoelastic deformation of a range of vitreous china testpieces during the firing process. The model constitutes a novel application of the transmission line modelling technique to viscoelastic deformation. The applicability of the model to the sanitary ware industry is addressed.

The aim of this research was to develop a novel thermal treatment technology able to transform the problematic fine fraction of incinerator bottom ash (IBA) into an inert material suitable for the production of ceramics. In this project two different problematic fractions of fine IBA have been used. The less than 1mm fraction of processed fine IBA dust was obtained from the dry discharge system for IBA used in the Energy from Waste (EfW) plant at Monthey, Zurich. The dry discharged fine IBA dust from the Monthey plant is currently disposed of to landfill at high cost. The second fine IBA fraction was supplied by Day Group who process wet discharge IBA from the Lakeside and the Newhaven EfW facilities in the South of England. There are currently no beneficial uses for the fine fraction which is either blended back into coarser fractions or disposed of to landfill. The conclusion from the research is that the fine fractions of IBA generated from both discharge techniques can be transformed into an inert material suitable for the production of hard, dense ceramics. Processing involves the addition of glass, wet ball milling and calcining, pressing and sintering. The addition of glass aids liquid phase sintering and improves the appearance of the ceramic body formed, milling increases sintering reactivity and calcining limits the loss of volatiles and shrinkage during firing. This transforms the major crystalline phases present in the fine IBA fraction from quartz (SiO2), calcite (CaCO3), gehlenite (Ca2Al2SiO7) and hematite (Fe2O3), to the pyroxene group minerals diopside (CaMgSi2O6) and clinoenstatite (MgSi2O6), together with some andradite (Ca3Fe2Si3O12). Processed calcined powders can be pressed and sintered to form dense (>2.5 g/cm3), hard ceramics that exhibit low firing shrinkage (<7%), zero water absorption and minimal leaching. Calcining the IBA: glass powders before processing was able to minimize the linear shrinkage observed compared to samples produced using uncalcined powders. Calcining also had the effect of reducing the leaching of metals of environmental concern present in the fine IBA fraction by over 95%. These are encapsulated within the glassy phases present in the calcined and sintered materials.

L’étude d'un matériau céramique a base d'argiles, en fonction de la température et de l'atmosphère de cuisson, nécessite une bonne connaissance de sa composition minéralogique. Les minéraux argileux et non argileux ont été analysés qualitativement et quantitativement avant et après les traitements thermiques. Les oxydes de fer sont parmi les principaux agents de coloration des matériaux céramiques cuits non émaillés, leur étude a permis d'une part de localiser les ions fe**(2+) dans les aluminosilicates, les ions fe**(3+) dans la goethite, l'hématite et les aluminosilicates, d'autre part de montrer que la formation de la magnétite n'a pas lieu à 1250**(o)c, à moins de conditions très réductrices. Une étude des transformations minéralogiques au cours de la cuisson a permis de mettre en évidence la formation de la mullite à 1100**(o)c environ et celle de la cristobalite à 1200**(o)c environ.

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Bachelors
Engineering and Computer Science
Engineering

Dans le cadre de ce travail, nous avons fabriqué des composites céramiques renforcés par des plaquettes céramiques par des techniques classiques de dispersion et de mise en forme et par frittage sous pression. Ces techniques ont permis d'obtenir des matériaux denses avec une dispersion homogène des plaquettes et une microstructure des grains constituant la matrice comparable dans le cas du matériau monolithique et du composite. Un choix judicieux des couples matrice-plaquettes a permis d'étudier l'influence des contraintes générées lors de la descente en température du frittage suite à la différence de coefficient de dilatation entre la matrice et les plaquettes et de la nature de l'interface sur les propriétés mécaniques du composite. Pour chacun des systèmes étudiés, les mécanismes de renforcement à température ambiante se sont avérés multiples. La contribution de chacun de ces mécanismes au renforcement est fonction des contraintes résiduelles et de la nature de l'interface. Cependant dans tous les cas les plaquettes constituent le défaut critique. L'évolution des mécanismes de renforcement avec la température peut être déterminée par les contraintes présentes à haute température (cas du système ZrO2-SiC), mais également par la présence d'une phase liquide à haute température (cas des systèmes Si3N4-SiC et ZrO2-Al2O3). Nous avons également démontré dans le cas du système Si3N4-SiC que le composite présente une meilleure résistance à la propagation sous-critique à haute température par rapport au matériau monolithique et, dans le cas du système ZrO2-Al2O3, que le composite, comme le matériau monolithique, est superplastique

Les outils de coupe ceramiques permettent, par l'augmentation des vitesses de coupe, l'amelioration des rendements d'usinage. Ce travail a consiste a developper un composite a matrice alumine 80- oxynitrure d'aluminium 20 vol. Pourcents renforce par du carbure de silicium sous deux morphologies: poudre et plaquette. Les etudes ont porte sur les ameliorations du procede de fabrication et l'evaluation du comportement en frottement et en coupe d'un acier dur (z38cdv5) et un superalliage base nickel (inconel 718). Outre l'interet de la formation in situ de l'oxynitrure d'aluminium (reaction alumine-nitrure d'aluminium) au cours du frittage sur la densification finale, il est montre qu'une homogeneisation par attrition conduit a un certain renforcement de la matrice. Les proprietes mecaniques du materiau a poudre optimise sont maintenues jusqu'a 1000c. Concernant le composite a plaquette, on observe une reactivite identique a celle du composite a poudre, mais a une temperature plus basse. On obtient les valeurs maximales de tenacite (7 mla. M) pour un diametre de moyen de 8 microns et une teneur en plaquettes de 20 vol. Pourcents. Dans les conditions de frottement testees (faible pression), l'usure des composites face a l'acier est negligeable, face a l'inconel l'usure n'est plus negligeable et depend de la granularite de sic et du taux d'oxynitrure. Les essais de coupe, realises a l'ecole centrale de nantes, laboratoire materiaux, montrent l'interet des composites renforces par la poudre pour le tournage d'acier de haute dureté

碩士
國立臺北科技大學
製造科技研究所
90
In this study, iron, copper, nickel, titanium and zinc materials will be machined to manufacture nano-size powders by using Electric-Discharge-Machining (EDM). Iron metal nano-size powders will be synthesized to form ferric oxide powders by oxidation process among these powders. Therefore, it is suggested that this manufacturing method is useful to produce nano-size ceramic powders. These nano-size ceramic powders are multi-function materials in industry. In this research, XRD and EDS apparatus will be used to examine the powder crystallization and chemical composition, and SEM and TEM will also be used to observe the powder morphology and crystal structure. The experimental results showed that the crystallization of these powders is composed of metal and its oxides, and the grain-size is within nano-size dimension. For these reasons, using EDM method to manufacture the nano-size metal and its oxides powders is workable. The experimental results showed that the magnetic ferric oxide nano-size powders Fe3O4 and γ-Fe2O3 can be obtained when the iron metal nano-size powders oxidized through 1 day air oxidation treatment at room temperature, and Fe3O4 and γ-Fe2O3 powders can be stored in deionized water because no more transformation is found during 10 days air oxidation treatment. The experimental results showed that Fe3O4 and γ-Fe2O3 powders can be obtained when oxidized below temperature of 300 ℃ heat treatment, and transform to be α- Fe2O3 phase above temperature of 300℃, and a stable α-Fe2O3 phase can be obtained at temperature of 500℃ heat treatment.

碩士
國立臺北大學
不動產與城鄉環境學系
93
Since 1980’s accelerated development of economic globalization, along with the achievements of ITC development, the increasing trans-strait economic activities in both quality and quantity have attracted many attentions from policy-makers and scholars. It is not only relating to the production systems between the both sites cross the strait, but also accelerates the reconstructing of Taiwanese production and economic system. However since China carried out economic reformation, immediately the demand on building materials progressively rising, the enormous business pulled lots of Taiwan building materials industry in. It also causes the anxiety of the “hollowing of industry” and the negative impacts on socio-economic structure in Taiwan. Therefore there is sure to need understanding the meanings of trans-border production network. This research try to understand the culture of governing mechanism by analyze the actors’ relationships and interaction in the trans-border production network of Taiwan ceramic building material and ceramic toilet products manufacturing in cross-strait in terms of glocalization theory, and discuss how it governance effectively trans-border production network. This research displays the Taiwan ceramic building material and ceramic toilet products manufacturing developed gradually the “localization” and the “vendor quality assurance” and the “credit line assurance” to govern the trans-border production network in the process of connecting with localized production system and consumption system, however it didn’t depend excessively on the socio-trust in the interpersonal relationship liked used to be. Moreover, the construction of trans-border production network accompanied the R&D function diffusing. The purposes of the diffusion of the R&D function are to shorten the time of responding to demand and to improve or develop product according to reflection of the various localized demand in time, and to enhance the effect of the technological guidance upon the vendors in the localized production system. In brief, the Taiwan ceramic building material and ceramic toilet products manufacturing grasp the ability of the Integrating and governing the global production chain in the construction of the trans-border production network in cross-strait, and then proceeding industry structure transformation and upgrade.

The past few years have delivered a great deal of development in the area of Layered Manufacturing. The challenge is to apply the existing technologies to existing and/or new manufacturing systems, thereby adding value to these systems. The advances in the field of Layered Manufacturing range from the process of slicing to the actual building process. The main achievements in the arena of slicing have been in the advances of Adaptive Slicing. By not using a uniform slice thickness, not only is the stair stepping effect minimized, but the build time is also shortened. Many advances have been made in terms of the actual materials used and the process of building, thereby expanding the range of uses for the technology as a whole. With the extension in the variety of materials available for use with the technology, new uses become more than mere possibility and actually become viable. The use of Layered Manufacturing in the case of the CSIR was not the focus of the original experiment, but was a method to test the results of their main experiments – namely, research into the properties of ceramic materials and their use in the realm of medicine. The research of the CSIR focuses on the use of ceramic materials for the purpose of bone implants, which is a problem area in medicine. The machine they built in order to test the properties of the new materials they invent, uses Layered Manufacturing as a building process. What the CSIR lacks are the backend systems to enable the building of more complex experimental parts, as they have no way of going from design to a full build. This research project focuses on proving that the technologies involved in Layered Manufacturing will add value to the CSIR’s research. By implementing a system that takes advantage of existing software, and by using custom software to make it applicable to the environment the CSIR is currently operating in, their research could be speeded up tremendously without putting too much strain on their budget. What has been achieved is a simple system which employs the use of available technologies and software packages, and which requires no changes to the hardware of the current process used, such as the Rapid Prototyping machine.
Ehlers, E.M., Prof.

abstract: This dissertation aims at developing novel materials and processing routes using alkali activated aluminosilicate binders for porous (lightweight) geopolymer matrices and 3D-printing concrete applications. The major research objectives are executed in different stages. Stage 1 includes developing synthesis routes, microstructural characterization, and performance characterization of a family of economical, multifunctional porous ceramics developed through geopolymerization of an abundant volcanic tuff (aluminosilicate mineral) as the primary source material. Metakaolin, silica fume, alumina powder, and pure silicon powder are also used as additional ingredients when necessary and activated by potassium-based alkaline agents. In Stage 2, a processing route was developed to synthesize lightweight geopolymer matrices from fly ash through carbonate-based activation. Sodium carbonate (Na2CO3) was used in this study to produce controlled pores through the release of CO2 during the low-temperature decomposition of Na2CO3. Stage 3 focuses on 3D printing of binders using geopolymeric binders along with several OPC-based 3D printable binders. In Stage 4, synthesis and characterization of 3D-printable foamed fly ash-based geopolymer matrices for thermal insulation is the focus. A surfactant-based foaming process, multi-step mixing that ensures foam jamming transition and thus a dry foam, and microstructural packing to ensure adequate skeletal density are implemented to develop foamed suspensions amenable to 3D-printing. The last stage of this research develops 3D-printable alkali-activated ground granulated blast furnace slag mixture. Slag is used as the source of aluminosilicate and shows excellent mechanical properties when activated by highly alkaline activator (NaOH + sodium silicate solution). However, alkali activated slag sets and hardens rapidly which is undesirable for 3D printing. Thus, a novel mixing procedure is developed to significantly extend the setting time of slag activated with an alkaline activator to suit 3D printing applications without the use of any retarding admixtures. This dissertation, thus advances the field of sustainable and 3D-printable matrices and opens up a new avenue for faster and economical construction using specialized materials.
Dissertation/Thesis
Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2019

Ceramics have been extensively used in aerospace, automotive, medical, and energy industries due to their unique combination of mechanical, thermal, and chemical properties. The objective of this thesis is to develop an extrusion based ceramic 3D printing process to digitally produce a casting mold. To achieve the objective, an in-house designed ceramic 3D printer was developed by converting a filament based plastic 3D printer. For mold making applications, zircon was selected because it is an ultra-high temperature ceramic with high toughness and good refractory properties. Additionally, alumina, bioglass, and zirconia slurries were formulated and used as the feedstock material for the ceramic 3D printer.

The developed 3D printing system was used to demonstrate successful printing of special feature parts such as thin-walled high aspect ratio structures and biomimetically inspired complex structures. Also, proof of concept with regard to the application of 3D printing for producing zircon molds and casting of metal parts was also successfully demonstrated.

To characterize the printed parts, microhardness test, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses were conducted. The zircon samples showed an increase in hardness value with an initial increase in heat treatment temperature followed by a drop due to the development of porosity in the microstructure, caused by the decomposition of the binder. The peak hardness value for zircon was observed to be 101±10 HV0.2. Similarly, the microhardness values of the other 3D printed ceramic specimens were observed to increase from 37±3 to 112±5 HV0.2 for alumina, 23±5 to 35±1 HV0.2 for bioglass, and 22±5 to 31±3 HV0.2 for zirconia, before and after the heat-treatment process, respectively.

Finally, a system model for the ceramic 3D printing system was developed through the application of the model-based systems engineering (MBSE) approach using the MagicGrid framework. Through the system engineering effort, a logical level solution architecture was modeled, which captured the different system requirements, the system behaviors, and the system functionalities. Also, a traceability matrix for the system from a very abstract logical level to the definition of physical requirements for the subsystems was demonstrated.

Dissertação de Mestrado Integrado em Engenharia Química apresentada à Faculdade de Ciências e Tecnologia
The present work is framed in the field of additive manufacturing, also known as 3D printing. The Robocasting technology, employed in this work, is one of the categories of additive manufacturing. It allows the processing of several types of materials, giving rise to a wide variety of items with complex geometries.The aim of this dissertation is to develop pastes of Al2O3 to apply in a Robocasting printer, the Wasp Extruder, in order to enable the printing of ceramic pieces at room temperature. The formulations are based on the cold mixture of a solvent, additives and the inorganic powder, being the final purpose the building of ceramic items with good properties, comparable to other objects produced by different AM technologies.Two different types of alumina pastes were selected to be studied. In the pastes of the 1st type, two different types of aluminium oxide with distinct particle size (D50 ≈ 4 µm and 0,7 µm) were tested. Either Zuzoplast C92 or arabic gum were used as a binder and the influence of a lubricant, glycerin, on the pastes was also tested. Water was always used as the solvent.For the 2nd type of pastes, only one type of aluminium oxide was used and water was kept as solvent. The major difference between this type of paste and the previous one is that, in this case, two binders, PVA and powdered sugar, were used in the same formulation. Moreover, an additional additive was used, oleic acid, with high affinity to alumina.The analysis of the rheological behaviour of the alumina pastes was carried out in a capillary rheometer (Thermo Haake Rheoflixer HT). A predominance of the pseudoplastic behaviour (where the viscosity decreases as the shear rate increases) was observed in the two types of formulations analysed. The viscosity increases as the particle size of the inorganic powder decreases. Several properties of sintered samples obtained from these two types of pastes were evaluated, with regard to their density, porosity and mechanical bending strength. Concerning the densification of the fabricated items, it is observed that the finest particles lead to a higher degree of packing, resulting in denser and less porous pieces. The values of the bending strength still are far from those that can be expected for the two types of pastes here studied.After characterizing the best pastes, these were tested in the Robocasting printer. Based on the results, it was observed that the best formulation for printing belongs to the 2nd type of paste. Notably, in spite of presenting good properties for application in the 3D printer, it gives rise to pieces with worse mechanical properties than the pastes of the 1st type.One of the aims of this work was achieved, the printing of Al2O3 pastes in the Robocasting printer. However, the pieces that were built do not exhibit yet the desired properties, namely in terms of densification level and strength. Therefore, further work will be needed for the optimization of conditions and tuning of formulations to achieve improved properties of the sintered items.
O presente trabalho insere-se na temática da fabricação aditiva ou também denominada de impressão 3D. A tecnologia robocasting está contida numa das categorias de fabricação aditiva e apresenta-se capaz de processar diferentes tipos de materiais e de originar uma ampla variedade de peças com geometrias complexas. Esta é a tecnologia usada no presente trabalho.O objetivo desta dissertação passa por desenvolver pastas em Al2O3 para aplicação numa impressora robocasting, a WASP Extruder, de maneira a que seja possível imprimir peças cerâmicas à temperatura ambiente. Estas formulações baseiam-se na mistura a frio de um solvente, aditivos e de um pó inorgânico, e deseja-se construir peças com boas propriedades, podendo ser comparadas com outros objetos originados por diferentes tecnologias AM.De acordo com o estudo prévio realizado optou-se por estudar dois tipos de pastas de alumina.Nas pastas do 1º tipo foram experimentados dois tipos de óxidos de alumínio com granulometrias distintas (D50 ≈ 4 µm e 0,7 µm). Como ligantes usou-se o Zuzoplast C92 ou a goma arábica, testando ainda a influência de um lubrificante nas pastas, a glicerina. Como solvente usou-se a água.Para o segundo tipo de pastas formuladas aplica-se apenas um tipo de óxido de alumínio, mantendo-se a água enquanto solvente. A grande distinção ente este tipo de pastas e o anterior é que, neste caso, são usados dois ligantes na mesma formulação, o PVA e o açúcar em pó, bem como um aditivo adicional, o ácido oleico, caracterizado pela sua grande afinidade com o pó inorgânico, alumina.Um dos principais pontos estudados nas formulações prende-se com a análise do comportamento reológico, tendo-se usado um reómetro capilar (Thermo Haake Rheoflixer HT). Verificou-se que o comportamento pseudoplástico (onde a viscosidade diminui com o aumento da taxa de corte) predomina entre os dois tipos de formulações analisadas. A viscosidade é tanto maior quanto menor a granulometria do pó inorgânico.Avaliaram-se ainda várias propriedades de provetes sinterizados obtidos com estes dois tipos de pastas, ao nível das massas volúmicas, porosidades e resistência mecânica à flexão. Relativamente à densificação das peças, verifica-se que as partículas mais finas conduzem a um maior grau de empacotamento, resultando peças mais densas e menos porosas. Os valores relativos às resistências à flexão alcançados ficam ainda muito aquém do espectável para ambos os tipos de pastas analisadas.Depois de caracterizadas as melhores pastas, testam-se na impressora robocasting. Com base nos resultados, verifica-se que a melhor formulação para impressão resulta do 2º tipo de pastas estudadas (Al1_PVA_A12). É de notar que apesar de apresentar boas propriedades para aplicação na impressora 3D, gera peças com piores propriedades mecânicas que as pastas do 1º tipo.Um dos objetivos do trabalho foi atingido, a impressão de Al2O3 em robocasting. No entanto, as peças construídas não possuem as propriedades desejadas, quer ao nível de densificação, quer ao nível da resistência, havendo ainda um longo caminho a percorrer.