Dissertations / Theses on the topic 'Clay addition'

Thesis (MScIng)--University of Stellenbosch, 2007.
ENGLISH ABSTRACT: Due to economic and environmental constraints mining operations are placed under increasing pressure to effectively manage and operate tailings disposal operations. Restrictions imposed on water usage and tailings operations footprint have led to higher density and wider particle size distribution slurries conveyed to tailings areas. One means of efficiently disposing the tailings is co-disposal. In this method a concentrated fine vehicle slurry is used to convey a coarser fraction. This produces a higher density of tailings, with a number of advantages both upstream and downstream of the tailings process. Limited research has been conducted on the effect of coarse particles on the non-Newtonian rheological properties of these slurries. This lack of information complicates the design and reliable operation of these systems. This project aims at gaining a clearer understanding as to the mechanisms involved in the addition of coarse particles to a fine clay slurry vehicle; and to provide a means of estimating the measured slurry rheological properties. A number of experiments were designed to test the slurry (both Kaolin only, and Kaolin-coarse particle mixtures) rheological properties using a Couette viscometer (for the dynamic flow properties of yield stress and plastic viscosity) and a vane instrument (for the static yield stress measurements). The slurries were prepared in varying Kaolin clay solids concentrations with reverse osmosis water. Glass beads and two types of industrial sand were used as the coarse fractions. All of the coarse particles had a similar size but varied significantly in shape. Slurry pH and temperature readings were monitored throughout the tests. Tests were done initially on clay only slurries. The rheological properties of these slurries were repeatable, and no noticeable variations of properties with time were observed. The yield stress (both static and dynamic) and plastic viscosity data were well correlated with established relationships. Coarse particles were added to the clay only slurries, and then removed. The remaining clay only slurry exhibited the same rheological properties as the initial clay only slurry. The presence of coarse particles increased all the measured rheological properties (i.e. dynamic yield stress, Bingham viscosity, and static vane yield stress) in a fashion resembling the effect of adding clay to a clay only slurry. In addition, the change in measured rheological property by addition of coarse particle was independent of the clay fraction in the clay slurry. Furthermore, with both the clay only slurries and clay and coarse sand slurries, a constant linear relationship existed between the static and dynamic yield stress. Several correlations from the literature were found to provide reasonable prediction of the rheological property variations observed. These empirical and semi-empirical models however did little to explain the mechanisms involved in coarse particle addition. A new correlation has been proposed, Residual Clay Concentration, which predicts the change in rheological property based on an additional clay concentration, which in turn is a linear function of the coarse particle concentration. The accuracy of this model further strengthens the belief that the coarse particle acts in a similar fashion to a floc. By means of a case study example the importance of selecting an appropriate model for design was illustrated. The Residual Clay Concentration method provided the most conservative results. This combined with its theoretical basis strengthens the models recommendation for use in design.
AFRIKAANSE OPSOMMING: As gevolg van ekonomiese en omgewings beperkinge word mynwese nywerhede onder toenemende druk geplaas om doeltreffende afvalstroom bestuur en operasie toe te pas. Beperkinge geplaas op water gebruik en afvalstroom area-groote ly tot hoër digthede en wyer partikel-grooteverspreidings van flodders vervoer na afval areas. Een manier om van die afval doeltreffend ontslae te raak en te berg is deur medeberging. In die metode word ‘n gekonsentreerde fyn flodder gebruik as draer van ‘n growwer partikel-fraksie. Dit ly tot ‘n hoër digtheid flodder, met verskeie voordele in beide die op – en afstroom prosesse. Beperkte navorsing is gedoen op die effek van growwe partikels op die nie-Newoniese rheolgiese eienskappe van hierdie flodders. Hierdie tekort aan informasie maak die effektiewe, betroubare bedryf en operasie van die sisteme meer ingewikkeld. Hierdie projek is daarheen gemik om ‘n beter begrip te ontwikkel met betrekking tot die meganismes betrokke in die byvoeging van growwe partikels aan ‘n fyn klei-agtige flodder draer; en om ‘n manier te voorsien wat die rheologiese eienskappe kan beraam. Verskeie eksperimente was ontwerp om die flodders (beide slegs Kaolien, en Kaoliengrowwe partikel mengsels) se rheologiese eienskappe te toets deur die gebruik van ‘n Couette-viskometer. Die Couette viskometer was gebruik om die dinamiese eienskappe (van grens-spanning, en plastiese viskositet) te meet. ‘n Vaan apparaat is gebruik om die eienskap van statiese grens-spanning te meet. Die flodders was voorberei in verskeie Kaolien konsentrasies met tru-osmosis water. Glas krale en twee tipes industriële sand is gebruik as die growwe fraksies. Al die growwe partikels het soortgelyke groottes gehad, maar het grootliks verskil in vorm. Die flodder pH en temperatuur lesings is deurentyd nagegaan. Toetse was aanvanklik gedoen op die klei-alleenlike flodders. Die gemete reologiese eienskappe van die flodders was herhaalbaar, en geen opmerkbare veranderinge van die eienskappe met betrekking tot tyd is gemeet nie. Die grens-spanning (beide statiese en dinamiese) en plastiese viskositeit is goed gekorrelleer met gevestigde verhoudinge. Growwe partikels is aan die klei-alleenlike flodders bygevoeg, en daarnae verwyder. Die oorblywende klei-alleenlike flodder het dieselfde gemete rheologiese eienskappe getoon as die oorspronklike klei-allenlike flodder. Die teenwoordigheid van growwe partikels het na ‘n toename van al die gamete rheologiese eienskappe gelei wat fisies baie soortgelyk is aan die byvoeging van klei tot ‘n klei-alleenlike flodder. Verder, met beide die klei-alleenlike en klei-growwe partikel flodders het ‘n konstante liniëre funksie tussen die statiese en dinamiese grens-spannings bestaan. Verskeie verhoudings uit die literatuur het goeie korrelasie bewerkstellig met die waargenome rheologie veranderinge. Hierdie empiriese en semi-empiriese modelle doen egter min om die megansimes betrokke in die toevoeging van growwe partikels te verduidelik. ‘n Nuwe korrelasie is voorgestel, naamlik die Residu Klei Konsentrasie. Hierdie model voorspel die verandering in reologiese eienskappe gebaseer op ‘n addisionele klei konsentrasie, wat ‘n liniëre funkise is van die growwe partikel konsentrasie. Die goeie korrelasie gesien met die model versterk die idée dat die growwe partikel in ‘n soortgelyke manier as ‘n flok gedra in die teenwoordigheid van ander flokke. Deur middel van ‘n tipiese industriële voorbeeld is die belangrikheid in die keuse van die regte korrelasie geillustreer. Die Residu Klei Konsentrasie metode het die mees konservatiewe resultate gelewer. Hierdie feit gekombineerd met die model se soliede teoreitiese beginsels versterk dit as voorgestelde korrelasie vir ontwerp.

Thesis (PhD)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: In materials chemistry, surface-initiated reversible deactivation radical polymerisation (SI-RDRP) has emerged as one of the most versatile routes to synthesising inorganic/organic hybrid materials consisting of well-defined polymers. The resultant materials often exhibit a remarkable improvement in bulk material properties even after the addition of very small amounts of inorganic modifiers like clay. A novel cationic reversible addition–fragmentation chain transfer (RAFT) agent with the dual purpose of modifying the surface of Laponite clay and controlling the polymerisation of monomer therefrom, was designed and synthesised. Its efficiency to control the polymerisation of styrene was evaluated and confirmed through investigating the molar mass evolution and chain-end functionality. The surface of Laponite clay was modified with the cationic chain transfer agent (CTA) via ion exchange and polymerisation performed in the presence of a free non-functionalised CTA. The addition of the non-functionalised CTA gave an evenly distributed CTA concentration and allowed the simultaneous growth of surface-attached and free polystyrene (PS). Further analysis of the free and grafted PS using analytical techniques developed and published during the course of this study, indicated that the free and grafted PS chains were undergoing different polymerisation mechanisms. For the second monomer system investigated n-butyl acrylate, it was apparent that the molar mass targeted and the monomer conversions attained had a significant influence on the simultaneous growth of the free and grafted polymer chains. Additional analysis of the grafted polymer chains indicated that secondary reactions dominated in the polymerisation of the surface-attached polymer chains. A new approach to separating the inorganic/organic hybrid materials into their various components using asymmetrical flow field-flow fractionation (AF4) was described. The results obtained not only gave an indication of the success of the in situ polymerisation reaction, but also provided information on the morphology of the material. Thermogravimetric analysis (TGA) was carried out on the polymer-clay nanocomposite samples. The results showed that by adding as little as 3 wt-% of clay to the polymer matrix, there was a remarkable improvement in the thermal stability.
AFRIKAANSE OPSOMMING: Oppervlakgeïnisieerde omkeerbare deaktiveringsradikaalpolimerisasie (SI-RDRP) is een van die veelsydigste roetes om anorganiese/organiese hibriedmateriale (wat bestaan uit goed-gedefinieerde polimere) te sintetiseer. Die produk toon dikwels ʼn merkwaardige verbetering in die makroskopiese eienskappe – selfs na die toevoeging van klein hoeveelhede anorganiese modifiseerders soos klei. ʼn Nuwe kationiese omkeerbare addisie-fragmentasie kettingoordrag (RAFT) middel met die tweeledige doel om die modifisering van die oppervlak van Laponite klei en die beheer van die polimerisasie van die monomeer daarvan, is ontwerp en gesintetiseer. Die klei se doeltreffendheid om die polimerisasie van stireen te beheer is geëvalueer en bevestig deur die molêre massa en die funksionele groepe aan die einde van die ketting te ondersoek. Die oppervlak van Laponite klei is gemodifiseer met die kationiese kettingoordragmiddel (CTA) deur middel van ioonuitruiling en polimerisasie wat uitgevoer word in die teenwoordigheid van ʼn vrye nie-gefunksionaliseerde CTA. Die toevoeging van die nie-gefunksionaliseerde CTA het ʼn eweredig-verspreide konsentrasie CTA teweeggebring en die gelyktydige groei van oppervlak-gebonde en vry polistireen (PS) toegelaat. Verdere ontleding van die vrye- en geënte PS met behulp van analitiese tegnieke wat ontwikkel en gepubliseer is gedurende die verloop van hierdie studie, het aangedui dat die vry- en geënte PS-kettings verskillende polimerisasiemeganismes ondergaan. n-Butielakrilaat is in die tweede monomeer-stelsel ondersoek en dit was duidelik dat die molêre massa wat geteiken is en die geënte polimeerkettings. ʼn Nuwe benadering tot die skeiding van die anorganiese/organiese hibriedmateriale in hulle onderskeie komponente met behulp van asimmetriese vloeiveld-vloei fraksionering (AF4) is beskryf. Die resultate wat verkry is, het nie net 'n aanduiding gegee van die sukses van die in-situ polimerisasiereaksie nie, maar het ook inligting verskaf oor die morfologie van die materiaal. Termogravimetriese analise (TGA) is uitgevoer op die polimeer-klei nanosaamgestelde monsters. Die resultate het getoon dat daar 'n merkwaardige verbetering in die termiese stabiliteit was na die toevoeging van so min as 3 wt% klei by die polimeermatriks.

Master of Science
Food Science Institute
Jayendra Amamcharla
Greek yogurt is one of the largest-growing sectors in the dairy industry accounting for over 25% of yogurt sales in the United States. Greek yogurt is produced by removing a portion of water and water soluble components from yogurt. Consequently, a large quantity of Greek yogurt whey (GYW) is being produced as a co-product. GYW is compositionally different from cheese whey, and thus poses economic and environmental challenges to the dairy industry. The objective of the present study was to evaluate two physical treatments as alternative methods for separating valuable GYW components: magnetic fluid treatment (MFT) and the addition of sepiolite, a clay mineral. A MFT chamber was designed using four pairs of neodymium magnets arranged to produce a magnetic field strength of 0.6 Tesla. Three batches of GYW each from two manufacturers were procured. A 2×3 factorial design was used with MFT or without MFT and the addition of zero, two, or four grams of sepiolite per 100g of GYW. The pH of GYW was adjusted to 7.2 using 5N NaOH solution, and the GYW was pumped at a rate of 7.5 L/min through the MFT system with or without MFT chamber attached. The sample was split into three sub-samples, heated to 80°C, and sepiolite was added as per the experimental design. The samples were centrifuged at 1,000g for five minutes. The top aqueous layer was separated and analyzed for total solids, ash, lactose, protein, calcium, phosphates, and sodium content along with color. MFT did not influence the analyzed whey components (P > 0.05) except for lactose. However, addition of sepiolite influenced protein content and a* and b* color values for the top aqueous layers (P < 0.05). Both levels of sepiolite addition resulted in about a 50% decrease in protein compared to original GYW. Adding two grams of Sepiolite per 100g of GYW from manufacturer 1 resulted in b* decreasing from 25.99 to 8.16 compared to treated GYW with no sepiolite. Sepiolite was found to have possible applications in the removal of proteins and color pigments in GYW.

Filamentous bulking is a problem that has long plagued activated sludge (AS) wastewater treatment plants (WWTPs). Much research has looked at its prevention and control but there is still no solution. The sludge microbiological community is very complex and there are many factors that can affect bulking. Clay addition in scaled-down activated sludge systems was investigated at concentrations of 0.4, 2.0 and 5.0 g/L along with sequencing batch reactor (SBR) parameters when run with a synthetic wastewater (SWW). The 5.0g/L concentration exhibited positive results on settling in the form of modified SVI but appeared to cause no reduction in filament length. These preliminary investigations indicate that clay may help improve sludge settling but make no difference in the abundance of filamentous microorganisms. The SBRs exhibited trends in regards to running systems with a synthetic wastewater. A loss of volatile suspended solids (VSS), coupled with increase in sludge volume index (SVI), suggested a link between lack of non-VSS and settling ability. This has implications in the importance of non-VSS such as grit or clay in research performed using SWWs.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2009.
Synthesis and structural characterization of two novel cationic and three new neutral reversible addition–fragmentation chain transfer (RAFT) agents is described. The cationic RAFT agents bear a quaternary ammonium group: N,N-dimethyl-N-(4- (((phenylcarbonothionyl)thio)methyl)benzyl)ethanammonium bromide (PCDBAB) and N-(4-((((dodecylthio)carbonothioyl)thio)methyl)benzyl)-N,N-dimethylethanammonium bromide (DCTBAB). The three neutral RAFT agents synthesized are 1,4- phenylenebis(methylene)dibenzene carbodithioate (PCDBDCP), didodecyl-1,4- phenylenebis(methyllene)bistrithiocarbonate (DCTBTCD) and 11-(((benzylthio)carbonothioyl) thio)undecanoic acid (BCTUA). The self-assembly behaviour in diluted aqueous solutions of the cationic RAFT agents, PCDBAB and DCTBAB, is described. The self-assembly behaviour was promoted by the presence of the thiocarbonyl- thio group on the RAFT agents, in addition to the overall chemical structure of the surfactant that also influence self-assembly. The RAFT agents were used for the bulk or miniemulsion RAFT-mediated controlled free-radical polymerization in the presence of clay to yield polymer–clay nanocomposites (PCNs). Bulk polymerization resulted in PCNs with better control of molar mass and polydispersity index (PDI) values when compared to PCNs prepared by miniemulsion polymerization. In both bulk and miniemulsion polymerizations the molar masses and PDI values were dependent on the amount of clay and RAFT agent present in the system. Free-radical bulk neutral RAFT agent-mediated polymerization resulted in PCNs with predominantly intercalated morphology. This was attributed to radical–radical coupling of the initiator anchored onto the clay galleries on which polymerization took place. On the other hand, when the cationic RAFT agent anchored onto clay, i.e. RAFT-modified clay was used, bulk polymerization resulted in predominantly exfoliated PCNs. However, miniemulsion polymerization carried out in the presence of the RAFT-modified clays resulted in PCNs with a morphology that ranged from partially exfoliated to intercalated morphology, as the clay loading was increased. The changing morphology for miniemulsion-based PCNs was attributed to the decreasing molar mass as the clay loading was increased. The PCNs obtained had enhanced thermo-mechanical properties as a result of the presence of clay. The thermo-mechanical properties depended on the molar mass, PDI, clay loading, and the morphology of the PCNs.

In Canada, about 60% of contaminated sites involve petroleum hydrocarbon (PHC) contamination and most of these sites have been abandoned due to contamination. Among current technologies used for soil remediation, supercritical fluid extraction (SFE) is a relatively recent and potentially viable method. The main aim of this research was to investigate the application of SFE for removal of PHCs from contaminated soils. In the first phase, the effects of SFE operational parameters including fluid pressure, fluid temperature, time duration and mode of extraction on the removal efficiency of PHCs from a spiked sandy soil (with diesel fuel with a ratio of 5 wt%) were investigated. SFE experiments were performed at different pressures (15, 33 and 50 MPa) and temperatures (30, 75 and 120 °C). The combination of 10 min static mode followed by 10 min dynamic mode, repeated for 3 cycles (60 min in total) led to the highest PHC removal percentage. According to response surface methodology (RSM), the optimum pressure and temperature were found to be 50 MPa and 69.3 °C, respectively. According to experimental results, the optimum combination of pressure and temperature determined to be 33 MPa and 75 °C; which resulted in the extraction percentages of 99.2%, 91.7% and 86.1% for PHC F2, F3 and F4 fractions, respectively. In the second phase, the influence of several parameters including soil water content, soil pH and addition of modifier on PHCs removals from a field-contaminated sandy soil using SFE were experimentally investigated. SFE experiments were performed at 33 MPa pressure and temperatures of 45 and 75 °C. Three water content levels of 8%, 14% and 20% at two levels of pH 6.5 and 7.5 were investigated. The extraction of total petroleum hydrocarbon fractions (TPHF), the sum of F2, F3, and F4 fractions, decreased due to the increase in the water content from 8% to 20% at both pH 6.5 and 7.5. The difference of extractions of all PHC fractions at pH values of 6.5 and 7.5 were not statistically significant (at p < 0.05 confidence level) at all three water content levels and pH did not have a significant influence on the PHC removal efficiency. Addition of acetone as a modifier (33.7% TPHF removal) was more effective than hexanes (24.3% TPHF removal) to decrease the concentrations of PHCs for the field contaminated soil. In the third phase, the influence of soil texture and grain size on the extraction of PHC fractions was investigated. SFE experiments were performed at 33 MPa pressure and 75 °C temperature. Three types of soils (soil A, B and C) were spiked with diesel fuel with a ratio of 5 wt%. Soil A, B and C had different particle sizes and were categorized as sand, silt loam and clay, respectively. Soil A (sand) which had the largest particle size resulted in the highest TPHF removal percentage while soil C (clay) with the smallest particle size led to the lowest TPHF removal percentage. A higher clay content in soil C resulted in a lower extraction of PHCs. In the fourth phase, the effects of pressure and temperature on the extraction of PHC fractions from a clay soil spiked with diesel fuel with a ratio of 5 wt% were investigated. SFE experiments were performed at three pressures (15, 33 and 50 MPa) and temperatures (30, 75 and 120 °C). According to the statistical analysis including factorial design and RSM, the optimized combination of pressure and temperature was selected at 42.8 MPa and 120 °C; which resulted in the removal percentages of 74.9% and 65.6% for PHC F2 and F3 fractions, respectively. The optimum combination of pressure and temperature based on the experimental results was selected at 33 MPa and 120 °C that led to 70.3%, 58.4% and 32.6% removal of PHC F2, F3 and F4 fractions, respectively.

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The rolled compacted concrete (RCC) is a still relatively new technique, but with growing volume of use, a fact generated by its technical and economical advantages, requiring more studies in order to use with greater efficiency, safety and economy. This work deals with the RCC with high levels of replacement and addition of part of the Portland cement by calcined clay pozzolan, aiming to analyze and quantify the improvements of the concrete properties and reach a satisfactory level of use, which allows for improvement or maintenance of the properties with a lower consumption of cement per cubic meter. So its impacts on the properties of RCC for this type of mineral addition were studied for the substitution levels adopted, checking the influence on the properties of the fresh concrete in the consistency and the density. For the hardened concrete some mechanical properties and durability were evaluated by compressive and tensile strength, capillarity and immersion by water absorption, test of permeability by water and ultrasound test. The use of calcined clay come together with the needs of the cement production for the construction of dams in the north of the country, as the case of Santo Antônio / RO, because its place is far removed from major industries and cement production slag, fly ash and silica fume, requiring the study of materials to enhance the production of cement. As an important result obtained with this research, it was found that substitution ranging from 27% to 50% achieved the best results, regarding the applicability of this material on the surveyed properties.
O Concreto Compactado com Rolo (CCR) é uma técnica ainda relativamente nova, porém com volume de utilização crescente, fato gerado pelas suas vantagens econômicas e técnicas, requerendo assim mais estudos para embasar o seu uso com maior eficiência, segurança e economia. O presente trabalho trata do CCR com elevados teores de substituição e de adição de parte do volume de cimento Portland por pozolana de argila calcinada, objetivando analisar e quantificar as melhorias das suas propriedades e chegar a um teor satisfatório de utilização, o qual possibilite melhoria ou manutenção das propriedades avaliadas com um menor consumo de cimento por metro cúbico. Desta forma foram avaliados os impactos nas propriedades do CCR para este tipo de adição mineral, nos teores adotados, aferindo a influencia nas propriedades do concreto no estado fresco quanto à consistência e massa específica. No estado endurecido algumas propriedades mecânicas e de durabilidade foram analisadas através da resistência à compressão e à tração por compressão diametral, a absorção de água por capilaridade e por imersão, a permeabilidade à água e ensaio de ultrassom. O uso da argila calcinada vem ao encontro das necessidades da produção de cimento para as usinas em construção na Região Norte do país, como é o caso de Santo Antônio / RO, pois se trata de uma obra muito distante das grandes indústrias cimenteiras e da produção de escória, cinza volante e sílica ativa, o que requer a investigação de materiais para aperfeiçoar a produção de cimento. Como resultado importante obtido na pesquisa em questão, verificou-se que a substituição oscilando entre 27% a 50% atingiu os melhores resultados quanto à aplicabilidade desse material nas propriedades pesquisadas.

L’obiettivo di questa tesi di laurea sarà quella di analizzare e studiare i limiti di una tecnologia innovativa di stampa FDM di paste a freddo, costituite da una miscela di argilla e prodotti di scarto (PA12) derivanti dal processo di tecnologia additiva Multi Jet Fusion, realizzata da HP. Particolare attenzione è stata rivolta allo studio delle tracce di estrusione, all’analisi dell’ accuratezza dimensionale dei provini estrusi e all’incidenza della quantità di polvere di PA12 sulle caratteristiche meccaniche dei provini nelle prove ad impatto, al fine di valutare criticità e punti di forza di questo nuovo processo.

The diploma thesis is focused on the issue of sedimentation stability of magnetorheological fluids, whis represents one of the most important characteristics determining the reliability of these fluids. Higher sedimentation stability can by achieved in several ways. Methods that are further examined in the thesis include particle polymerization and the addition of clay mineral additives. Both achieve positive results by schowing increased sedimentation stability. However, in the case of additives, the effect is much higher. In particular, the CLAYTONE 40 additive achieves a lower particle sedimentation rate while maintaining the same viscosity as the commercial LORD-122ED. The results provide significant knowledge in the field and can bring magnetorheological fluids closer to wider commercial use.

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

Depuis 1984, les matériaux à gradients de fonction (FGM) permettent de former une barrière thermique et réduire les fortes discontinuités des propriétés entre deux matériaux de nature différente. Ces multi-matériaux, qui consistent en une variation intentionnelle de la composition chimique entrainant par conséquent une modification des propriétés microstructurales, chimiques, mécaniques et thermiques, permettent de lisser la distribution des contraintes thermiques. L’élaboration in situ de ces alliages sur mesure est rendu possible grâce à l’utilisation de procédés de fabrication additive tel que le procédé par dépôt de poudres DED-CLAD®. Ces procédés connaissent un essor considérable depuis les années 1980 et sont idéaux dans la fabrication de FGM. Dans le cadre de cette thèse CIFRE, des développements techniques ont été effectués pour adapter le procédé DED-CLAD® et permettre la réalisation de FGM. Grâce à plusieurs collaborations industrielles, une étude complète a été réalisée sur les alliages titane-molybdène et titane-niobium. Ces alliages permettent dans le premier cas de réaliser des pièces résistantes à de fortes sollicitations thermiques (secteur spatial), et dans le second cas d’associer les propriétés mécaniques et la biocompatibilité (secteur biomédical). L’originalité de cette thèse repose sur l’étude d’un gradient complet, c’est-à-dire que l’ajout en élément d’alliage varie de 0% à 100%. En effet, les études reportées dans la littérature ne font pas mentions des alliages titane-matériaux réfractaire pour des taux élevés en élément réfractaire. Les analyses microstructurale (DRX, structure cristallographique par EBSD, microstructure), chimique (EDS) et mécanique (microdureté, tests de traction et essais d’indentation instrumentée) ont mis en évidence une évolution des propriétés le long du gradients de composition. La caractérisation mécanique des échantillons par indentation instrumentée s’est par ailleurs révélée particulièrement pertinente dans les cas de ces multi-matériaux
Since 1984, the Functionally Graded Material (FGM) allow to create a thermal barrier and to reduce the strong discontinuities of properties between two materials of different composition. These multimaterials,whose consist of an intentional variation in the chemical composition and, consequently, modify the microstructural, chemical, mechanical and thermal properties, lead to a smooth distribution of the thermal stress. The in-situ development of these custom-made alloys is made possible by the use of additive manufacturing processes such as the DED-CLAD® powder deposition process. These processes have grown substantially since the 1980s and are optimal for the manufacture of FGM. During this industrial thesis, technical developments have been carried out to adapt the DED-CLAD® process and to allow the manufacturing of FGM. Thanks to two industrial collaborations, a full study was carried out on titanium-molybdenum and titanium-niobium alloys. These alloys make it possible, in the first case, to produce parts resistant to strong thermal stress (space sector), and in the second case to combine mechanical properties and biocompatibility (biomedical sector). The originality of this thesis rests on the study of a complete gradient, that is the addition in alloy element varied from 0% to 100%. In fact, studies reported in the literature do not mention titanium-refractory material for high levels of refractory element. Microstructural (XRD, crystallographic analysis by EBSD technique), chemical (EDS) and mechanical (microhardness, tensile test and instrumented indentation) analyses revealed an evolution of the properties along the chemical gradient. The mechanical characterization of the sample by instrumented indentation has also proved particularly relevant in the case of these multi-materials

The sol-gel process has been employed to generate hybrid inorganic-organic network materials. Unique ceramers were prepared based on an alkoxysilane functionalized soft organic oligomer, poly(propylene oxide) (PPO), and tetramethoxysilane (TMOS). Despite the formation of covalent bonds between the inorganic and organic constituents, the resulting network materials were phase separated, composed of a silicate rich phase embedded in a matrix of the organic oligomer chains. The behavior of such materials was similar to elastomers containing a reinforcing filler. The study focused on the influence of initial oligomer molecular weight, functionality, and tetramethoxysilane, water, and acid catalyst content on the final structure, mechanical and thermal properties. The sol-gel approach has also been exploited to generate thin, transparent, abrasion resistant coatings for metal substrates. These systems were based on alkoxysilane functionazized diethylenetriamine (DETA) with TMOS, which generated hybrid networks with very high crosslink densities. These materials were applied with great success as abrasion resistant coatings to aluminum, copper, brass, and stainless steel. In another study, intercalated polymer-clay nanocomposites were prepared based on various epoxy networks montmorillonite clay. This work explored the influence of incorporated clay on the adhesive properties of the epoxies. The lap shear strength decreased with increasing clay content. This was due to a reduction in the toughness of the epoxy. Also, the delaminated (or exfoliated) nanocomposite structure could not be generated. Instead, all nanocomposite systems possessed an intercalated structure. The final project involved the characterization of a series of metallocene catalyzed linear polyethylenes, produced at Phillips Petroleum. Polyolefins synthesized with such new catalyst systems are becoming widely available. The influence of molecular weight and thermal treatment on the mechanical, rheological, and thermal behavior was probed. Although the behavior of this series of metallocene polyethylenes was not unlike that of traditionally catalyzed materials, this work is one of the first comprehensive studies of these new linear polyethylenes. The main distinction between the metallocene and traditional Ziegler-Natta catalyzed polyethylenes is the narrow molecular weight distributions produced by the former (for this series of materials, 2.3< Mw  Mn <3.6).
Ph. D.

Etude de l'influence de densite, teneur en eau, temperature, et aussi des caracteristiques mineralogiques et des conditions physiques externes (accroissement de temperature, contrainte mecanique). Amelioration de la conductivite par additifs (graphite, quartz). Utilisation de modeles pour relier la conductivite a celles de chaque phase; bons resultats obtenus avec le modele geometrique (empirique) et le modele de porosite ellipsoidale

Robotics and digital design are associated with the creation of free forms. The thesis deals with the potential of new building technologies in the sense of an opportunity to build on the foregoing regional architecture, disconnected by an industrial mass production. A creation that can reinterpret the charm and diversity of Moravian houses, preserving the continuity between old morphology and today’s housing requirements.

Seal of sand or gravel by chemical injection is known and used for a long time. Chemical grouting are however expensive and sometimes the use of cement does not lead to desire effects. So it is trying to find new materials and methodologies injection arrangement works. To achieve savings of chemical products are added to a mixture clay and cement. Clay-cement grouting mix are used not only in order that they are better quality, but also because in this way proposed mixtures have a tendency to penetrate better into incoherent sediments that need additional sealant of chemical injection. For further possible reductions of economic terms the mixture is trying to replace the classic clay. As a suitable substitute for classic clay is to a certain extent the use of secondary raw materials. Above all it is fly ash. As a part of my thesis I deal with the appropriateness use of these materials and examining their properties in the mixture. It was found that by using fly ash were improving consistency of the fresh mixture, reducing the amount of water-cement ratio and reduce shrinkage of the mixture. On the other hand, by using fly ash has been increasing decantation, permeability atc. In the next stage of my work was examined the influence of the quality of cement, lime and liquefaction in the mixture. The aim of thesis is to propose the optimal injection mixture for additional sealing earth dams.

Les effluents industriels issus des activités de textile présentent souvent une importante charge polluante colorante difficilement biodégradable. Des travaux antérieurs ont montré le potentiel des argiles naturelles non traitées à dépolluer ces effluents teinturiers alors qu’ils sont généralement composés de colorants anioniques difficilement adsorbables sur ces supports. Or, les effluents contiennent également d’autres composés chimiques utilisés dans les différentes étapes du procédé de teinture, et qui sont de natures variées (sels, acides, bases, détergents, dérivés enzymatiques, etc…). Il semblerait que ces produits auxiliaires jouent un rôle dans l'adsorption de colorants anioniques sur l'argile non traitée. Cependant, aucune étude connue à ce jour, n'a porté sur l'effet des additifs de teinture dans le processus de décoloration par des absorbants en général, et par les argiles en particulier. Cette étude est la première à s’intéresser au système colorant-additif-argile. Des tests d’adsorption / désorption en batch ont été menés en considérant différents systèmes colorant-additif-argile. Les résultats des tests montrent que les additifs de type enzymatique favorisent l’adsorption de colorant anionique sur l’argile en neutralisant les charges négatives et en renforçant les liaisons argile-colorant. D’autres additifs ont un effet contraire mais n’annulent pas l’effet positif des additifs enzymatiques lorsqu’ils sont mélangés dans l’effluent. Des hypothèses d’interactions mises en jeu lors de l’adsorption de colorant ont été faites en s’aidant des résultats de la spectrométrie infra-rouge et de masse, de la zétamétrie et de la modélisation des isothermes d’adsorption
Industrial effluents from textile activities often have a high pollution load readily biodegradable. Previous work has shown the potential of natural untreated clays to clean up these dyers effluents although anionic dyes are not easily absorbable on these media. The effluents also contain other chemical compounds used in the different stages of the dyeing process, and which are of various natures (salts, acids, bases, detergents, enzyme derivatives, etc ...). It appears that these auxiliary products play a role in the adsorption of anionic dyes on untreated clay. However, no currently known study has examined the effect of the additives from the dyeing process on the adsorption of dye onto clay. This is the first study to focus on the dye-clay-additive system. Adsorption / desorption batch tests were conducted considering different dye additive-clay systems. The tests’ results show that the enzyme like additives enhance the adsorption of anionic dye on the clay by neutralizing the negative charges and reinforcing clay-dye links. Other additives have the opposite effect, but do not offset the positive effect of enzyme like additives when mixed in the effluent. Assumptions of interactions involved in dye adsorption were made with the help of the results of infrared and mass spectrometry, zetametry and the modeling of adsorption isotherms

Globally, most agricultural systems have lost 40 to 70% of their natural soil organic carbon (OC) through removal of harvest product and past management practice. It is critical to identify and implement practices that minimise or reverse the decline in soil carbon while balancing economic sustainability and global food needs. Increasing OC storage in agricultural soils provides an opportunity to offset greenhouse gas emissions, improve soil health, fertility, structure, water-holding capacity and plant productivity. The amount of stored OC varies among soil types and is strongly influenced by clay concentration. Sandy soils often have low OC content because of low input from limited plant growth and rapid decomposition due to low clay concentration. Sandy soils cover a large proportion of Australia’s agricultural region and are common worldwide. Thus, increasing OC in sandy soils is a good opportunity for increased OC storage. In natural soils, there is a positive correlation between clay and OC concentration because binding of OC to clay reduces decomposition by soil microbes. Therefore, the addition of clay to sandy soil has the potential to increase OC storage. Subsoil clay addition to sandy soils is a practice used in South Australia, Victoria and Western Australia to overcome water repellence and increase water retention, fertility and plant productivity. The addition of subsoil clay to sand creates clods of different sizes, from a few mm to more than 200 mm in diameter distributed in the soil profile. The method chosen for subsoil clay addition can influence clod size and distribution in the soil profile. Little is known about the potential of clay-amended soils to increase OC content and whether clay addition methods can be optimised to increase the OC storage capacity. The aim of the thesis was to determine the effect of subsoil clay addition to sand on clay distribution and OC content. A series of field studies and two incubation experiments were carried out to determine the effect of subsoil clay addition to sand on OC and clay distribution and content. Procedures were validated to ensure sampling captured the variability of OC and bulk density in clay-amended soil. The distribution of clay and OC in the soil profile was quantified for clay-amendment methods. In addition, the effects of clod size, clod chemical properties and amount of added subsoil clay on OC concentrations were evaluated. In the first study the number of soil samples required within a 25-m grid for accurate OC and bulk density measurement in clay-amended soils was determined. Further, OC concentration, bulk density and OC stocks in sandy soil without and with clay addition were measured. The study was carried out on two agricultural properties in South Australia (one in the South East, the other on Eyre Peninsula), where sandy soils without clay addition (1–3% clay) were compared with three methods of kaolinitic subsoil clay addition to sand (clay spread, delved or spaded). Within a 25 m x 25 m sampling area, twenty randomly allocated soil cores to 50 cm depth were collected after harvest. The results showed that 10 randomly allocated cores within a 25 m x 25 m sampling area was sufficient to represent the variability of OC concentration in sandy soil without and with clay addition. Two to three samples were required within the sampling area for accurate representation of bulk density. Stratified sampling is recommended for delved sites with sample allocation based on the proportion of area represented by delve lines and that between delve lines. Subsoil clay addition to sand increased OC stock in 0-30 cm depth by up to 14 t ha ⁻¹ in the South East and 22 t ha⁻¹ on the Eyre Peninsula. OC stock increase was site specific. OC stock was influenced by the clay addition method and dependent on the amount of clay added and depth of incorporation. Clay spreading increased clay and OC close to the soil surface, delving increased them at depth and spading distributed OC and clay evenly within the mixed depth. The second study assessed i) size, number and vertical distribution of clods and OC at two field sites with clay addition and ii) the effect of clod size and properties on OC in incubation experiments. Two field sites, Eyre Peninsula (EP) and South East (SE) with different clay addition method, spaded or delved, were studied. Soil was excavated from a 30 cm quadrat in 10 cm increments from 0 to 40 cm, sieved into various clod sizes in which soil mass, clod number and OC concentration were determined. Subsoil clay properties from 40-60 cm depth including clay concentration, pH, exchangeable cations, iron and clay mineralogy from both sites were analysed. Delving elevated clay and created few, mainly large clods, which were poorly distributed in the sandy soil. Spading mixed clay from 20-30 cm below the soil surface and created many, smaller clods, which were more evenly distributed within 0-30 cm than with delving. OC concentration was highest in the smallest clods, particularly those from close to the soil surface. Clod number per unit of soil mass was more important for OC stock than OC concentration of the clods. Clods collected from the two field sites were further used in incubation experiments to determine the effect of clod size and properties (clay and iron concentration) on potential accumulation and protection of OC. In the accumulation experiment, subsoil clay was collected at depth greater than 40 cm from EP and SE crushed and sieved to clods of 2-6 and 6-20 mm size. The clods were added to sand at 80 mg clay g ⁻¹ sand and incubated with monthly wheat residue addition for 300 days at a water content optimal for microbial activity. In the protection experiment, 2-6 mm and 6-20 mm clods collected from 0-10 cm depth at the SE site were added to sand at 80 mg clay g ⁻¹ sand and incubated for 420 days at a water content optimal for microbial activity. Smaller clods (2-6 mm) accumulated OC at a higher rate and offered greater protection to decomposition by microbes than larger clods (6-20 mm). Clod properties, clay concentration and sesquioxide content influenced OC concentration of 6-20 mm clods but not the 2-6 mm clods. This suggested that the large surface area of the 2-6 mm clods minimised the effect of clod properties. Furthermore, clod number was a critical factor in increasing OC stock. Due to different clay concentration in the EP (58%) and SE (39%) subsoil, to achieve the same target clay addition rate more clods were added per pot for SE compared to EP. OC concentration of the 2-6 mm clods did not differ between EP and SE, thus the higher OC stock in the clods from the SE site was driven by clod number (mass). The higher clod number increased the total surface area and thus the chance that added wheat residue would come in contact with the clod surface. We conclude that in clay-amended soils the addition of many, smaller clods distributed throughout the depth of modification can maximise OC content. The third study aimed to i) compare OC stock in a range of clay-amended and unamended sandy soils under cereal cropping in South Australia and ii) identify factors that influence OC stock to develop best practices to increase OC storage in clay-amended sandy soils. The study was carried out on four agricultural properties in South Australia. Soil OC content, clay content and selected physical and chemical properties of clay-amended treatments and unamended sands were measured. Clay amendment treatments differed in the method of clay addition (clay spread or delved), depth of incorporation (shallow and deep) and amount of subsoil clay added to the surface 30 cm. Soil cores to 50 cm depth were collected within a 25 m x 25 m sampling area. There was a positive correlation between OC and clay stock, but it only explained 46% of the variation in OC stock. This indicated that other factors influenced OC stock in clay-amended treatments. Even vertical distribution of clay within the surface 30 cm was a key factor in increasing OC storage in clay-amended soils. Subsoil clay properties and amount added to the surface 30 cm, as well as depth to undisturbed subsoil also influenced OC stock.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2018

Sandy soils have low water and nutrient holding capacity which limit crop growth. In the short-term, these constraints can be overcome by increased fertiliser application or irrigation. However, long-term solutions are needed to improve farm productivity and sustainability. Clay added to sandy soils may be such a solution. Compared to sandy soils, clay soils have smaller pores and higher cation exchange capacity and therefore greater water and nutrient holding capacity. Clay can also bind organic matter via cation bridges and thereby reduce its accessibility to decomposing microbes. In sandy soils with clay subsoil, the clay can be mixed into the sandy top soil by delving or spading. However, the clay subsoil is not uniformly distributed in the sandy top soil. It forms clay peds of varying size which creates a highly non-uniform soil environment with patches of sandy soil with clay peds next to sandy soil with little or no clay. The clay-rich patches can hold more water and nutrients compared to the surrounding sandy soil that could influence nutrient availability and organic C binding. Little is known about the influence of ped size and rate of clay added to sandy soil on nutrient availability and organic C binding after residue addition. The aims of the study were i) to determine the effect of clay addition rate and ped size in residue amended sandy soil on soil respiration, nutrient availability and organic C retention ii) to assess the effect of clay soil particle size and clay soil properties on nutrient availability and organic C binding after addition of residues with low or high C/N ratio iii) to determine the effect of clay addition rate and ped size on nutrient leaching after mineral fertilizer addition. A series of incubation experiments were carried out to assess the effect of clay addition rate and ped size on nutrient availability and organic C retention on < 53 μm fraction after mixing with low and high C/N ratio residue. In the first study, clay peds of 1, 2 or 3 mm size derived from a clay-rich Vertosol (73% clay) were added to a sandy soil (3% clay) at clay addition rates of 10% and 20% w/w. After addition of ground mature faba bean residue (C/N 37) at 10 g kg-1, the soils were incubated for 45 days at 80% of water holding capacity. Clay addition to sandy soil influenced nutrient availability after plant residue addition, particularly when small peds are added at higher rates. Sandy soil with clay peds had a greater maximum NH4 and P sorption capacity than sandy soil alone, sorption capacity was higher at 20% compared to 10% clay addition and greater with 1 mm than 3 mm peds. Retrieval of clay peds at the end of the experiment showed ped breakdown during the experiment but also formation of larger peds. Compared to the < 53 μm fraction added at the start of the experiment, total organic carbon (TOC) content of the < 53 μm fraction was up to two-fold higher, particularly in the smaller peds (1 and 2 mm). The study confirmed that claying can increase organic C sequestration, but also showed that organic C sequestration is likely to be greatest when the added clay peds are small. The capacity to bind organic C and nutrients may depend on clay soil properties such as mineralogy, clay concentration and exchangeable Fe and Al. A 45-day experiment was carried out to investigate the effect of clay type on nutrient availability and organic carbon retention with residues differing in C/N ratio (20 or 47). Two clay soils with smectite as a dominant mineral were used. They differed in smectite percentage [high (40%) or low (5-10%)], clay content (73 or 42%) and exchangeable Fe and Al concentration (low or high). The clay soils were added to sandy soil at rate of 20% w/w either finely ground or as 2 mm peds. Over 45 days, available N and P, microbial biomass N and P concentrations and cumulative respiration were greater with low C/N than high C/N residue. With low C/N residue, compared to sandy soil alone clay addition increased available N concentration and initial microbial biomass C and N, but decreased cumulative respiration and P availability. This study showed that addition of clay soil to sandy soil influences nutrient availability, but there were no clear differences between clay soils or sizes. The lack of differences between high and low smectite clay soil suggests that a high concentration of Fe and Al oxides can compensate for a lower clay concentration and proportion of smectite with respect to binding of organic matter and nutrients. In the previous studies, we found that clay addition had no consistent effect on cumulative respiration and ped size effect was variable. Secondly, low C/N ratio residue had stronger effect on nutrient availability due to its high decomposition rate and nutrient release compared to high C/N ratio residue. The third experiment was conducted to investigate that if clay addition has a different effect on respiration and nutrient availability when added as peds with a greater range of sizes (1, 3 and 5 mm) in presence of plant residue with lower C/N ratio. The aims of this experiment were to (i) determine the effect of clay addition rate and ped size in residue amended sandy soil on nutrient availability, and (ii) assess breakdown of peds during the experiment and organic C retention by the < 53 μm fraction of the peds. Clay soil addition to sandy soil amended with plant residue reduced respiration rate and available P concentration. Ped size had little effect on respiration and nutrient availability. Clay soil addition increased soil organic carbon retention compared to sandy soil alone. With respect to ped size, the experiment showed substantial ped breakdown and but also formation of larger peds over 45 days. The first three experiments were conducted over 45 days. But longer term studies are needed to better evaluate the effect of claying in the field. To investigate the effect of repeated addition of residue (finely ground wheat mature shoots added every 2 months) in clay amended sandy soil, a longer term (8 months) study was conducted with clay soil added as finely ground soil, 1 and 3 mm peds. The organic C content of the whole soil increased during the experiment with a greater increase in clay amended soils. The organic C content of the > 53 μm fraction was very low and changed little over time. With finely ground clay soil and 1 mm peds, the organic C content of the < 53 μm fraction increased mainly in the first 2 months while in 3 mm peds it increased over 6 months to reach similar concentrations as with finely ground clay soil and 1 mm peds. Excessive use of fertilizer in sandy soils can cause leaching of nutrient elements N and P into water ways and cause eutrophication. In the fifth experiment, clay soil was added in sandy soil at 10% or 20% clay soil w/w finely ground or as 2 and 5 mm peds with and without N and P fertiliser (27 mg N kg-1 and 7 mg P kg-1). The clay sand mixture (30 g) was placed in cores with nylon mesh at the bottom. The soils were incubated at 80% water holding capacity and leachate was collected weekly for 50 days. Clay addition significantly reduced leaching of N and P as compared to sandy soil alone. In sandy soil alone, the highest N (68%) leaching occurred after the first week whereas the highest amount (41%) of P was leached after two weeks. It can be concluded that clay addition to sandy soil can reduce the risk of nutrient leaching and enhance carbon sequestration in sandy soils by decreasing C loss via respiration and leaching. This effect will be greatest with finely ground clay soil or small peds.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food & Wine, 2017

No
Municipalities and recycling and environmental authorities are concerned about the growing amount of carpet waste produced by household, commercial and industrial sectors. It is reported that 500,000 tonnes of carpet waste fibre are plunged into landfills annually in the UK. In the United States of America, around 10 million tonnes of textile waste was generated in 2003. In geotechnical engineering, expansive clay soils are categorised as problematic soils due to their swelling behaviour upon increase in the moisture content. The problematic nature of such soils is intensified with the increase in the plasticity index. This paper presents results of a comprehensive investigation into utilisation of carpet waste fibres in order to improve the swelling characteristics of compacted cohesive soils. Therefore, two different clay soils with markedly different plasticity indices (i.e. 17.0 and 31.5 %) were treated with two different types of carpet waste fibre. Waste fibres were added to prepare specimens with fibre content of 1, 3 and 5 % by dry weight of soil. Soil specimens with different dry unit weights and moisture contents were prepared so as to the swelling behaviour of fibre reinforced compacted clays is completely attained under various scenarios. The results indicated that the behaviour of the fibre reinforced soils seems highly dependent on the initial compaction state and secondary on the moisture content. It was found that the swelling pressure drops rapidly as the percentage of fibre increases in samples prepared at the maximum dry unit weight and optimum moisture content. Reducing the dry unit weight, while maintaining constant moisture content or increasing the moisture content at constant dry unit weight was found to reduce the swelling pressure.

Acid sulfate soils (ASS) are soils or sediments that contain sulfuric, hypersulfidic or hyposulfidic materials or are affected by transformation of sulfidic minerals (e.g., pyritic, FeS2). ASS are widely distributed globally and typical in environments such as coastal and inland wetlands. The main biogeochemical processes influencing the pH in ASS are sulfate reduction and pyrite oxidation. Under flooded conditions (low redox potential), sulfate reducing bacteria (SRB) using easily decomposable organic matter (OM) as their energy source, produce sulfide, which reacts with iron in sediments to form pyrite or mono-sulfides, which are stable under flooded conditions. Sulfate reduction consumes protons and therefore, results in a pH increase. When sulfidic sediments dry, pyrite can oxidise and generates acidity. In soils with low pH buffer capacity (pHBC), this can result in severe acidification and metal solubilisation. Often sulfate reduction does not occur even after pro-longed flooding which may be due to lack of organic carbon (C) availability. Management strategies aiming to ameliorate ASS include liming or inundation. However, they may be uneconomical, unsustainable or can be ineffective. Therefore, alternative strategies are required to manage ASS. OM addition could be an effective strategy to ameliorate ASS due to its role during sulfate reduction. It may also maintain higher level of pH even during dry periods by buffering the acid generated and stimulating microbial activity and thus oxygen consumption through. Readily degradable C of OM and duration, in which OM remain available to sulfate reducing bacteria, may be important in maintaining wetland ASS. Management of wetlands often involves introduction of wet and dry periods to restore ecosystem health. OM addition could be included to improve the effectiveness of this strategy. In this thesis, soils from Banrock station wetland were used in a series of incubation experiments. The wetland has extensive ASS and acidification was observed in many areas in a survey conducted in 2009. Since then, wetland managers have introduced wet-dry cycles to improve wetland health. The aim of this thesis was to determine the effect of type of organic C or sulfidic clay soils added on pH and redox potential (Eh) in ASS during wet and dry periods. The hypotheses to be tested were: (¡) Addition of easily decomposable OM will have a greater effect on pH and redox potential than poorly decomposable OM (¡¡) Acidification during the dry period will be smaller at high compared to low water content because high water content limits diffusion of oxygen (¡¡¡) Mixing sulfidic clay soils into ASS will minimise pH changes during wet and dry periods, particularly clay soils with high pH buffer capacity. In the first experiment, the effect of type of organic amendment was investigated. Three wetland ASS (sulfuric, hypersulfidic and hyposulfidic) collected from different depths were used. The soils, unamended or amended with 10 g C kg-1 as glucose, wheat straw, pea straw or Phragmites litter, were incubated for 18 weeks under flooded conditions (“wet period”) followed by 10 weeks during which the soils were maintained at 100% of maximum water-holding capacity (WHC) (“dry period”). During the wet period, the pH decreased in the control and with glucose to pH 3-4, but increased or was maintained in residueamended soils (pH at the end of the wet period about 7). In the dry period, the pH of the control and glucose amended soils remained low, whereas the pH in residue amended soils decreased. However, at end of the dry period, the pH was higher in residue amended soils than in the control or glucose amended soils, particularly with pea straw (carbon: nitrogen 50, C/N 50). It can be concluded that amendment of ASS with plant residues (particularly those with low to moderate C/N ratio) can stimulate pH increase during flooding and reduce acidification under oxidizing conditions. The second experiment was carried out to assess the effect of OM addition on pH in a wet-dry cycle followed by a second wet period. A further aim was to investigate the influence of water content during the dry period on acidification. Three ASS (sulfuric, hypersulfidic and hyposulfidic) were collected from one profile and unamended or amended with 10 g C kg-1 as finely ground wheat straw. The soils were exposed to a submerged (wet) period, a dry period, followed by another wet period. In the first wet period (10 weeks), the pH increased only in the amended soils, which was accompanied by a strong decrease in Eh. To investigate the effect of water content during the dry period on pH, the soils were rapidly dried to 40, 60, 80 or 100% of WHC at the start of the dry period. This water content was maintained during the dry period. The pH decrease during the 10-week dry period was greater in amended than in unamended soils and greater at 60, 80 or 100% than at 40% of WHC. At the end of the dry period, the pH was higher in amended than in unamended soils and higher at 40% of WHC than at the higher water contents. In the second wet period (16 weeks), the pH increased only in the amended soils. The pH increase was accompanied by a decrease in Eh in the amended soils. The water content in the previous dry period did not influence pH in the second wet period in the unamended soils, but in the amended soils, the pH was higher in soils previously maintained at 40% of WHC than that maintained at higher water contents. At the end of the second wet period, the pH was higher in amended than in unamended soils. This study shows the ameliorative effect of OM addition in ASS. OM addition can improve energy supply for sulfate reducers which results in an increase in pH during the wet period and lead to a higher pH in the oxidation period. The smaller pH increase and Eh decrease in amended soils in the second compared to the first wet period suggests that OM decomposition was lower in the second wet period likely because rapidly decomposable compounds had been utilised in the previous wet and dry periods and only recalcitrant OM remained. Therefore OM may have to be added repeatedly for sustained amelioration of ASS. The aim of the third experiment was to investigate the effect of addition of hyposulfidic clay soils to a sufuric sandy soil on pH changes in reduced and oxidised conditions. A sulfuric sandy soil (pH 4.1) was mixed with three hyposulfidic clay soils (with clay contents ranging between 38 and 72%) to give clay soil proportions of 0, 25, 50, 75 and 100 (% dry soil). According to their net negative acidity, the three clay soils are referred to as: NA-334, NA-54 and NA-8 (values in moles H+ tonne-). The soils were amended with wheat straw at 10 g of C kg -1 and then incubated for 14 weeks under reducing conditions (wet period) followed by 11 weeks incubation under oxidising conditions (dry period) during which they were maintained at 100% of maximum WHC. The pH of the sulfuric soil alone increased during the wet period by about two pH units (to pH 6) and decreased by more than two pH units (to pH <4) during the dry period. In the clay soils alone and treatments with sulfuric soil, the pH during the wet period decreased by 0.5 to 1 unit with NA-334 and NA-54 and increased by one unit with NA-8. The pH was >6 in all clay treatments at the end of the wet period. During the dry period, the pH remained above pH 7 with NA-334 and decreased by about one unit (to pH 5.5) with NA-8. In treatments with NA-54, the pH decrease during the dry period depended on the proportion of clay soil, ranging from 0.5 pH unit with 75% clay soil to two pH units with 25% clay soil. The capacity of the clay soil treatments to maintain stable pH during wet and dry periods depended mainly on the negative net acidity of the added clay soils, but was not related to their concentration of reduced inorganic sulfur or clay content. It can be concluded that addition of clay soils with high negative net acidity could be used to ameliorate acidity in ASS. The fourth experiment was conducted to determine the effect of OM addition over two successive wet-dry cycles in four ASS. Four soils differing in clay content (10, 15, 23, 38% referred to as C10, C15, C23 and C38) were unamended or amended with 10 g C kg-1 finely ground wheat straw and incubated over 24 weeks with each wet and each dry period lasting 6 weeks. Soil pH increased in both wet periods, particularly in amended soils with low clay content (C10 and C15). The Eh decreased more strongly in amended soils than in unamended soils and became negative from week 2 onwards whereas the Eh stayed positive in unamended soils except C38. In the dry periods, the pH decreased more strongly in amended soils than in unamended soils, particularly in C10 and C15. Changes in pH during wet and dry periods were greater in soils with low clay content (C10, C15) than those with high clay content (C23, C38). The effect of wheat straw addition on pH at the end of wet and dry periods did not differ between the two wet-dry periods, with a higher pH in amended than unamended soils. This study showed that wheat straw addition maintains its ameliorative effect on soil pH for at least two wet-dry cycles, but the pH effect depends on clay content, being greater in soils with low clay content. The effectiveness of this method would have to be tested under field conditions, particularly where wet and dry periods continue for longer periods.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Agriculture, Food and Wine, 2016.

碩士
嘉南藥理科技大學
環境工程與科學系
101
Particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs) emissions of burning incense have been investigated on the quality of surrounding air. However, the reduction of PM and PAHs from burning incense has received little attention. In the present study, two types of incense were made in the laboratory. Five to thirty percent of Oyster (OS) and Asiatic Clam Shells (ACS) was added to Sin-shan, Lao-shan, Liao and Chen wood flours, which are popular incense materials. Experimental results indicate that the reduction of emissions of PM and PAHs from burning incense increased with increasing amount of OS and ACS additive. Mean PM reductions for 30.0% of OS and ACS were 35% and 34%, respectively. Mean PAH reductions were 21% and 20% for particle-phase PAHs, respectively, and 37% and 21% for benzo[a]pyrene equivalent concentration, respectively. These results may be attributed to OS and ACS acted as filler in the burning incense. OS and ACS was substituted for organic material in the incense reducing PM and PAHs emissions from the smolder. The findings of this study may serve as a guide to producing safer and less-polluting incense.

Indiana University-Purdue University Indianapolis (IUPUI)
Bronze is a popular metal for many important uses. Currently, there are no economical 3D printers that can print Bronze powders. A recent product, Bronze Metal Clay (BMC) has arrived. Additionally, commercial metal 3D printers require laser or electron beam sources, which are expensive and not easily accessible. The objective of this research is to develop a new two-step processing technique to produce 3D printed metallic component. The processing step includes room temperature 3D printing followed by high-temperature sintering. Since no material data exists for this clay, the tensile strength and hardness properties of BMC are compared to wrought counterpart. In this research tests are completed to determine the mechanical properties of Cu89Sn11 Bronze Metal Clay. The author of this thesis compares the physical properties of the same material in two different formats: 3D printed clay and molded clay. Using measured stress-strain curves and derived mechanical properties, including Young's modulus, yield strength, and ultimate tensile strength, the two formats demonstrate inherit differences. The Ultimate tensile strength for molded BMC and 3D-printed specimens sintered at 960 C was 161.94 MPa and 157 MPa, respectively. A 3D printed specimen which was red at 843 C had 104.32 MPa tensile strength. Factory acquired C90700 specimen had an ultimate stress of 209.29 MPa. The Young's modulus for molded BMC and 3D-printed specimens sintered at 960 C was 36.41 GPa and 37.05 GPa, respectively. The 843 C 3D-printed specimen had a modulus of 22.12 GPa. C90700 had the highest modulus of 76.81 GPa. The Yield stress values for molded BMC and 3D-printed specimens sintered at 960 C was 77.81 MPa and 72.82 MPa, respectively. The 3D-printed specimen had 46.44 MPa. C90700 specimen had 115.21 MPa. Hand molded specimens had a Rockwell hardness HRB85, while printed samples had a mean of HRB69. Also, molded samples recorded a higher Young's Modulus of 43 GPa vs. 33 GPa for the printed specimens. Both samples were weaker than the wrought Cu88:8Sn11P0:2 which had a 72 GPa. Cu88:8Sn11P0:2 also was a harder material with an HRC45. The property di erence between 3D printed, molded, and wrought samples was explained by examining their micro structures. It shows that 3D printed sample had more pores than the molded one due to printing process. This study demonstrates the flexibility and feasibility of using 3D printing to produce metallic components, without laser or electron beam source.

碩士
國立臺灣科技大學
化學工程系
95
In this work, the effects of nano-scale and submicron-scale acrylic type of core-shell rubbers (CSR) and silane-treated montmorillonite (MMT) clay as additives for UP resins, on the mechanical properties of the styrene(St)/Unsaturated Polyester(UP)/additives ternary systems after the cure have been investigated. For St/UP/ silane-treated MMT ternary systems,the scattering intensity of unsaturated polyester (UP) with different structure in dilute styrene solution was measured by the method of small angle X-ray scattering (SAXS), and the radius of gyration of the UP molecule can then be calculated by using the Guinier law. Hence, the ease at which the UP molecule can diffuse into the gallery spacing of the MMT clay can be evaluated. The change of inter-gallery spacing of MMT and inter structure of the material for the St/UP/ silane-treated MMT systems before and after the cure has also been studied by using the SAXS and wide angle X-ray scattering (WAXS).

Dissertação de mestrado em Construção e Tecnologia
Considerando uma abordagem transformadora na indústria, as técnicas de fabrico aditivo (FA) transformaram várias áreas ao longo das últimas décadas, como a arquitetura e a engenharia, no que toca à produção de sistemas e revestimentos mais complexos. Estes fatores foram executáveis devido à constante evolução tecnológica, conseguida através da alteração do paradigma do pensamento analógico-digital. O ‘fabrico aditivo’ é um processo de transformação que advém de um desenho digital e rematasse num modelo físico, culminando a capacidade de criação de um modelo tridimensional por meio da adição do próprio material - Aditivo. Denominar este processo de ‘impressão 3D’ ou ‘prototipagem rápida’ é incorreto, uma vez que estes dois termos na realidade são duas vertentes que surgiram do FA. Cada objeto produzido para prototipagem é digitalmente definido pela utilização de softwares Computer Aided Design (CAD), onde, através da geração de um código é possível “fatiar” o objeto para a sua produção. Embora as técnicas de FA possam suscitar surpresas para alguns utilizadores, a sua existência remota à várias décadas, sofrendo assim constantes evoluções transversalmente ao desenvolvimento tecnológico. Quando aplicadas em determinados contextos oferecem elevadas vantagens, maiormente na obtenção de modelos com um elevado rigor e detalhe. A pesquisa de ‘novos’ materiais é possível, se se constatar que ao longo desta investigação, é pretendido aumentar o conhecimento, adquirido até à data, para possíveis misturas compósitas oportunas para utilização em arquitetura. Graças às tecnologias de fabrico aditivo e à integração de processos de modelação tridimensional, a celulose, efetivamente pode ser considerada uma nova possibilidade para a produção de elementos arquitetónicos quando adicionada estrategicamente com determinados materiais. O desenvolvimento de variadas misturas poderá beneficiar o campo tecnológico, mais concretamente a impressão 3D e prototipagem rápida, através da laboração de uma pasta possível de utilizar para a personalização de componentes arquitetónicos, com baixos custos de produção. O principal caso de estudo desta investigação centra-se no desenvolvimento de uma parede modular, que utiliza como base blocos hexagonais regulares. Será desenvolvida com o intuito de compilar todos os resultados obtidos com o estudo da celulose e a possibilidade de união a outros materiais. Toda a parede será engendrada através de razões paramétricas, recorrendo a programas computacionais, fazendo-se variar a geometria de cada bloco segundo parâmetros definidos.
Considering a transformative approach in the industry, additive manufacturing (AM) techniques have been transforming several areas in the past decades, such as architecture and engineering, regarding systems productions and complex coatings. These factors were executable due to the constant technological evolution, achieved through the alteration of the paradigm of analogical-digital thinking. The ‘additive manufacturing’ is a process of transformation that accrues from a digital design and comes into a physical model, culminating the ability to create a three - dimensional model through the addition of the material itself - Additive. To name this process of ‘3D printing’ or ‘rapid prototyping’ is incorrect, since these two terms are actually two strands that arose from the AM. Each object produced for prototyping is digitally defined by the use of Computer Aided Design (CAD) software, where, through the generation of a code, it is possible to “slice” the object for its production. Although the AM techniques can cause surprises for some users, their existence is remote for several decades, thus suffering constant changes across technology development. When applied in certain contexts they might offer high advantages, mainly by obtaining models with high rigor and detail. The research of ‘new’ materials is possible, has it has been verified throughout this investigation, it is intended to increase the knowledge, acquired so far, for possible composite mixtures suitable for architecture use. Thanks to the technologies of additive manufacturing and the integration of three-dimensional modeling processes, cellulose can effectively be considered as a new possibility at the production of architectural elements when added strategically with certain materials. The development of various mixes could benefit the technological field, namely 3D printing and rapid prototyping, by working with a paste that can be used for personal customization in architectural components, regarding low cost production. The main case on this research focuses on the development of a modular wall, which uses regular hexagonal blocks as base. It will be developed with the purpose of compiling all the results obtained with the study of cellulose and the possibility of union with other materials. The entire wall will be generated through parametric reasons, using computational programs, by making the geometry of each block vary according to defined parameters.

碩士
國立臺灣科技大學
化學工程系
95
The effects of nano-scale core-shell rubber type of low profile additive and Silane treated montmorillonite clay on the cure kinetics and glass transition temperature of styrene/unsaturated polyester/additive ternary system have been investigated. The reaction kinetics of styrene/unsaturated polyester/additive ternary system during the cure at 1100C was investigated by Differential Scanning Calorimetry (DSC) and Fourier Transform Infra-Red Spectoscopy (FTIR). Adding nano-scale core-shell rubber type of low profile additive and silane treated montmorillonite clay into the system has increased the unsaturated C=C bonds conversion, which was related to the formation of microgel particles during the polymerization. Based on the Takayanagi mechanical models, the effect of additive nano-scale core-shell rubber type of low profile additive on the glass transition temperature of ternary cured sample was studied. The glass transition temperature of the ternary cured sample was measured by Dynamic Mechanical Analysis (DMA) and Thermal Stimulated Current (TSC).

碩士
國立臺灣科技大學
化學工程系
96
The effects of reactive microgel (RM) and nano-scale and sub-micron scale core shell rubbers (CSR) as low-profile additives (LPA), and silane treated montmorillonite clay (MMT) on the cure kinetics and glass transition temperatures for styrene/unsaturated polyester/additive ternary systems have been investigated. The reaction kinetics for the ST/UP/additive ternary system during the cure was measured by differential scanning calorimetry (DSC) and Fourier transform infrared spectrometry (FTIR). Finally, based on the Takayanagi mechanical models, the glass transition temperature in each region of the cured samples for ST/UP/additive ternary systems has been measured by the dynamic mechanical analysis (DMA).

碩士
國立臺灣科技大學
化學工程系
95
The effects of two additives, including (1) nano- scale and submicron-scale core-shell rubber additive, and (2) montmorillonite clay, on the cured sample morphology, volume shrinkage characteristics and internal pigmentability for the styrene(St)/ unsaturated polyester(UP) /additive ternary systems after the cure were investigated. The experimental results have been explained by integrated measurements combining phase characteristic of the St/UP/additive ternary system before the cure, XRD analysis , cured sample morphology, final cure conversion, and volume fraction of microvoid generated during the cure by using DSC , SAXS , WAXS , SEM , TEM , OM and image analysis. (keywords: core-shell rubber(CSR); montmorillonite (MMT); volume shrinkage;internal pigmentability;unsaturated polyester(UP); curing)

碩士
國立臺灣科技大學
化學工程系
92
The effects of three series of additives, including(1)poly(vinyl acetate)(PVAc) low-profile additives(LPA), (2)core-shell rubber toughener, (3)montmorillonite clay, on the microvoid formation, morphology, volume shrinkage characteristics, internal pigmentability and mechanical properties for the styrene/unsaturated polyester/additive ternary systems after the cure were investigated. The experimental results have been explained by phase characteristic of the styrene/unsaturated polyester/additive ternary system before the cure, cured sample morphology and volume fraction of microvoid generated during the cure.

碩士
國立臺灣科技大學
化學工程系
94
The effects of reactive microgel (RM) particle type of low-profile additives (LPA), nano-scale core-shell rubber (CSR) tougheners, and montmorillonite clay (MMT) on the cure kinetics and glass transition temperatures for styrene/unsaturated polyester/additive ternary systems have been investigated. The scattering intensity of unsaturated polyester (UP) in dilute styrene solution was measured by the method of small angle X-ray scattering (SAXS), and the radius of gyration of the UP molecule can then be calculated by using the Guinier law. Hence, the ease at which the UP molecule can diffuse into the gallery spacing of the MMT clay can be evaluated. The reaction kinetics for the ST/UP/additive ternary system during the cure was measured by differential scanning calorimetry (DSC)and Fourier transform infrared spectrometry (FTIR). Finally, based on the Takayanagi mechanical models, the glass transition temperature in each region of the cured samples for ST/UP/additive ternary systems has been measured by the method of thermally stimulated currents (TSC) and the method of dynamic mechanical analysis (DMA).

碩士
國立臺灣科技大學
化學工程系
94
The effect of three series of additives, including(1) reactive microgel particle, (2) nano- scale core-shell rubber toughener, and (3) montmori- llonite clay, on the morphology, volume shrinkage characteristics, and internal pigmentability for the styrene(ST)/ unsaturated polyester(UP) /additive ternary systems after the cure were investigated. The experi- mental results have been explained by integrated measurements com- bining phase characteristic of the ST/UP/additive ternary system before the cure, cured sample morphology, final cure conversion, and volume fraction of microvoid generated during the cure.

碩士
國立臺灣科技大學
化學工程系
93
The effect of four series of additives, including(1)poly(vinyl acetate) (PVAc), (2)polycaprolactone(PCL) low-profile additives, (3)reactive microgel particle, (4) montmorillonite clay, on the microvoid formation, morphology, volume shrinkage characteristics,internal pigmentability and mechanical properties for the styrene/unsaturated polyester/additive ternary systems after the cure were investigated. The experimental results have been explained by phase characteristic of the styrene/ unsaturated poly- ester /additive ternary system before tht cure, cured sample morph- ology and volume fraction of microvoid generated during the cure.

碩士
國立臺灣科技大學
化學工程系
96
The effects of two additives, including (1) nano- scale and submicron-scale core-shell rubber additive, and (2) montmorillonite clay, on the cured sample morphology, volume shrinkage characteristics and internal pigmentability, mechanical properties of the styrene(St)/Unsaturated Polyester(UP)/additives ternary systems after the cure have been investigated. The experimental results have been explained by integrated measurements combining phase characteristic of the St/UP/additive ternary system before the cure, XRD analysis , cured sample morphology, final cure conversion, and volume fraction of microvoid generated during the cure by using DSC , SAXS , WAXS , SEM , TEM , OM and image analysis. Then the scattering intensity of unsaturated polyester (UP) with different structure in dilute styrene solution was measured by the method of small angle X-ray scattering (SAXS), and the radius of gyration of the UP molecule can then be calculated by using the Guinier law. For St/UP/ silane-treated MMT ternary systems, I try to calculate the gallery spacing change of MMT clay by intensity of different concentration cured samples.

碩士
國立臺灣科技大學
化學工程系
93
The effects of reactive microgel particle type of low-profile additives, the effects of core structure and addition of nano-scale core-shell rubber tougheners, and the effects of addition of montmorillonite clay on the cure kinetics and glass transition temperatures for styrene/unsaturated polyester/additive ternary systems. In addition, The effects of the miscibility of styrene/unsaturated polyester/additive ternary systems on DSC reaction rate profile and the cured sample morphology also were investigated.Finally, base on the Takayanagi mechanical models, the glass transition temperature in each phase region of cured saples has been identified by the method of thermally stimulated currents analyser.

Dissertação de mestrado em Engenharia do Produto
A fabricação aditiva (FA) é uma designação frequente dos processos de impressão 3D de um modelo físico, por camadas, a partir de um modelo digital tridimensional com geometria precisa e usando a quantidade exata de material – sem desperdício e sem a necessidade de utilização de outros instrumentos ou ferramentas. A presente dissertação restringe-se à exploração da FA por extrusão de pastas cerâmicas. As especificidades da criação dos produtos com este tipo de processo, exige o profundo conhecimento dos materiais cerâmicos, prevendo e controlando o seu comportamento em todas as fases, nomeadamente durante a secagem e cozedura. A utilização de diferentes pastas cerâmicas implicou a necessidade de explorar soluções adequadas à criação de produtos arquitetónicos, analisando diferentes parâmetros e variáveis do processo de FA. Este estudo dá particular ênfase à otimização das pastas cerâmicas para processos de extrusão por FA. Recorre-se ao método de Pfefferkorn para caracterizar o índice de plasticidade das pastas. Os protótipos desenvolvidos e os estudos efetuados serviram de base para a análise da retração das várias pastas cerâmicas considerando diferentes curvas de cozedura. A correlação entre a retração e o comportamento mecânico das diversas pastas usadas nesta investigação constitui um contributo relevante que permitirá a FA de elementos e estruturas cerâmicas com consumos elétricos controlados.
Additive manufacturing (AM) is a common designation for the definition of three-dimensional printing processes of a physical model, in layers, from a three-dimensional digital model, resulting in a faithful physical representation that uses the exact amount of material during production - without waste and without the need to use other instruments or tools. This dissertation is restricted to the exploration of AM by extrusion of ceramic pastes. The specificities of creating products by this process requires a thorough knowledge of ceramic materials, predicting and controlling their behaviour at all stages, namely during drying and firing. The use of different ceramic pastes implied the need to explore appropriate solutions for the creation of architectural products, analysing different parameters and variables of the AM process. This study places particular emphasis on the optimization of ceramic pastes for AM extrusion processes, using the Pfefferkorn method to characterize the optimal plasticity index of each of the tested pastes. The prototypes developed and the studies carried out served as a basis for analysing the shrinkage of the various ceramic pastes considering different firing curves. The correlation between the shrinkage and the mechanical behaviour of the different pastes used in this investigation constitutes a relevant contribution that will allow the AF of elements and ceramic structures informed and adapted to a specific context.