Metal Additive Manufacturing (AM) technologies in particular powder bed fusion processes such as Selective Laser Melting (SLM) and Direct Metal Laser Sintering (DMLS) are capable of producing a fully-dense metal components directly from computer-aided design (CAD) model without the need of tooling. This unique capability offered by metal AM has allowed the manufacture of inter-connected lattice structures from metallic materials for different applications including, medical implants and aerospace lightweight components. Despite the many promising design freedoms, metal AM still faces some major technical and design barriers in building complex structures with overhang geometries. Any overhang geometry which exceeds the minimum allowable build angle must be supported. The function of support structure is to prevent the newly melted layer from curling due to thermal stresses by anchoring it in place. External support structures are usually removed from the part after the build; however, internal support structures are difficult or impossible to remove. These limitations are in contrast to what is perceived by designers as metal AM being able to generate all conceivable geometries. Because support structures consume expensive raw materials, use a considerable amount of laser consolidation energy, there is considerable interest in design optimisation of support structure to minimize the build time, energy, and material consumption. Similarly there is growing demand of developing more advanced and lightweight cellular structures which are self-supporting and manufacturable in wider range of cell sizes and volume fractions using metal AM. The main focuses of this research is to tackle the process limitation in metal AM and promote design freedom through advanced self-supporting and low-density Triply Periodic Minimal Surface (TPMS) cellular structures. Low density uniform, and graded, cellular structures have been developed for metal AM processes. This work presents comprehensive experimental test conducted in SLM and DMLS processes using different TPMS cell topologies and materials. This research has contributed to new knowledge in understanding the manufacturability and mechanical behaviour of TPMS cellular structures with varying cell sizes, orientations and volume fractions. The new support structure method will address the saving of material (via low volume cellular structures and easy removal of powder) and saving of energy (via reduced build-time).

No presente trabalho foi desenvolvido um suporte catalítico monolítico para fins aeroespaciais empregando a manufatura aditiva. Para tanto, foi proposta uma geometria que proporcione um escoamento turbulento, permitindo um maior contato entre o reagente e a superfície do catalisador, proporcionando menor perda de carga ao sistema. Esta nova estrutura foi obtida via manufatura aditiva, através da técnica de Sinterização Seletiva a Laser (SLS) indireta. Para utilizar a técnica SLS e material cerâmico, foi necessário desenvolver um revestimento sobre as partículas de alumina para promover a aderência entre as mesmas durante o processo de manufatura aditiva. Em seguida foram definidos, experimentalmente, os parâmetros de aplicação da técnica SLS para o compósito alumina/poliamida. Por fim, foi fabricado, via SLS, o suporte catalítico na forma monolítica. Após a confecção do suporte monolítico, foi desenvolvido um revestimento composto de pseudo-boemita e nitrato de alumínio e aplicado na superfície do monólito, a fim de expandir a área superficial específica do material. Este aumento da área específica favorece a dispersão da fase ativa, composta de óxidos de cobalto e manganês, na superfície do suporte. A caracterização do catalisador monolítico foi realizada a partir das técnicas de Adsorção de Nitrogênio, Análise Termogravimétrica, Microscopia Eletrônica de Varredura e Espectrometria de Emissão Ótica com Fonte de Plasma (ICP-OES). O desempenho do catalisador monolítico na decomposição do H2O2 concentrado foi analisado via teste de gota, monitorado por câmera de alta velocidade. Os bons resultados obtidos nesta reação apontam esta técnica de obtenção de suporte catalítico monolítico através da manufatura aditiva como uma metodologia promissora a ser empregada em sistemas catalíticos com elevada difusão de massa e calor, mas principalmente em sistemas propulsivos a monopropelente. / This work was developed by the additive manufacture monolithic catalytic support to apply aerospace applications. A geometry was proposed to implement a turbulent flow allowing a better contact with catalytic surface and reagent with a low pressure drop in the system. This new structure was obtained by additive manufacture through indirect Selective Laser Sintering (SLS) technique. Firstly, in order to use the SLS for the ceramic material was developed a coating on the alumina particles to promote a melting between them during addictive manufacturing process. Secondly, the printer parameters SLS was configurated into the alumina/polyamide particle. Finally, the monolithic catalytic support was built via SLS. After the monolithic support building, the pseudo-boehmite and aluminum nitrate coating was developed and applied on the monolithic surface to increase the specific superficial area of the material. This increasing of the specific surface area helps the spread of the active phase to made up of cobalt and manganese oxide in the support surface. The characterization of the monolithic catalyst was carried out using the nitrogen adsorption technique, thermogravimetric analysis, scanning electron microscopy and inductive coupled plasma with optical emission spectrometry. The monolithic catalytic performance in the H2O2 concentrated decomposition was analyzed via drop test monitored by the high-speed camera. The good results of this reaction and such a technique of monolithic catalytic support obtainment through the additive manufacture show that a promising methodology can be used in the catalytic system with high diffusion of mass and heat but mainly, in monopropellant propulsive system.

Otto Scheeloch's U.S. Patent No. 134,442 of 1872 describes a unique firearm that uses triangular bullets. The current research effort evaluates the ballistic performance of Otto's disclosure for the very first time. To achieve this goal it was necessary to seek out surviving artifacts and scour the historical record in search of all the parameters needed to meticulously recreate the curious triangular cartridges and the corresponding gun barrel, with its matching twisted triangular bore. Every aspect of the resulting reproduction ammunition was made to be as authentic as possible, including the use of vintage civil war era bullet lead, bullet grease of period recipe, and the correct type of black powder propellant. 3D CAD (SolidWorksTM) was employed in designing the components, while advanced rapid prototyping (FDM & DMLS) techniques and investment casting were used in the physical construction of the ammunition and barrel. The ballistics testing was performed from a shooting rest over a range of 10-feet. Data was obtained for five rounds using a chronograph, paper targets and ballistic gel. The triangular bullets proved to be surprisingly accurate, consistent, and stable in flight. Data was recorded for sectional density, ballistic coefficient, muzzle velocity and energy, group size and penetration.

<p>In powder metallurgy research field, Direct Metal Laser Sintering (DMLS) and Metal Powder Starch Consolidation (MPSC) are relatively new rapid forming techniques to fabricate complex and near net-shaped components. The working principles of DMLS are to melt and fuse metal powder layer by layer in computer controlled systems to pile up components like three dimensional printing. It has been for instance extensively used for mould inserts, die parts, and functional metal prototypes. Another, less explored method, starch consolidation is a pressureless direct casting method which consists principally of mixing powder slurry, casting into moulds, consolidation, drying, and sintering. With a strong focus on both methods, the study here combines several strong material technology sectors; powder, rapid forming, mechanical property testing and surface technology. It covers the processing chain from green body preparation, optimization of</p><p>sintering, nitriding, post sinter heat treatment, to modeling and assessment of material behaviour for end-user applications. An iron based powder and a high vanadium high speed steel powder with low and high carbon contents were used in the DMLS and MPSC processes, respectively. The overall aim of the study is to synthesize near net-shaped powder-based components, to characterize pores and microstructure, and to establish a fundamental understanding of failure mechanisms of powder based materials in bending fatigue, thermal fatigue and wear.</p><p>The study showed the DMLS and MPSC technologies could produce shaped components with a multi-phased structure, controllable nitriding depth and high relative densities in a range of 97 - 99.7 %. Materials' heterogeneity and porosity have detrimental influence on mechanical properties, especially on crack initiation and subsequent propagation.</p>

Electrically conductive polymer composites are suitable for use in the manufacture of antistatic products and components for electronic interconnects, fuel cells and electromagnetic shielding. The most widely used processing techniques for producing electrically conductive polymer composites place an inherent constraint on the geometry and architecture of the part that can be fabricated. Hence, this thesis investigates selective laser sintering (SLS), a rapid prototyping technique, to fabricate and characterize electrically conductive nanocomposites of Nylon-12 filled with 4% by weight of carbon black. The objective of the dissertation was to study the effects of the SLS process on the microstructure and properties of the nanocomposite. The effect of laser power and the scan speed on the flexural modulus and part density of the nanocomposite was studied. The set of parameters that yielded the maximum flexural modulus and part density were used to fabricate specimens to study the tensile, impact, rheological and viscoelastic properties. The electrical conductivity of the nanocomposite was also investigated. The thermo-mechanical properties and electrical conductivity of the nanocomposites produced by SLS were compared with those produced by extrusion-injection molding. The structure and morphology of the SLS-processed and extrusion-injection molded nanocomposites were characterized using gas pycnometry, gel permeation chromatography, differential scanning calorimetry, electron microscopy, polarized light microscopy and x-ray diffraction. Physical models were developed to explain the effects of the processing technique on the structure and properties of the nanocomposites. Finally, a one-dimensional heat transfer model of the SLS process that accounted for sintering-induced densification and thermal degradation of the polymer was implemented in order to study the variation in part density with respect to the energy density of the laser beam. This dissertation demonstrated that SLS can be successfully used to fabricate electrically conductive polymer nanocomposites with a relatively low percolation threshold. This capability combined with the ability of SLS to fabricate complicated three-dimensional objects without part-specific tooling could open up several new opportunities.

In powder metallurgy research field, Direct Metal Laser Sintering (DMLS) and Metal Powder Starch Consolidation (MPSC) are relatively new rapid forming techniques to fabricate complex and near net-shaped components. The working principles of DMLS are to melt and fuse metal powder layer by layer in computer controlled systems to pile up components like three dimensional printing. It has been for instance extensively used for mould inserts, die parts, and functional metal prototypes. Another, less explored method, starch consolidation is a pressureless direct casting method which consists principally of mixing powder slurry, casting into moulds, consolidation, drying, and sintering. With a strong focus on both methods, the study here combines several strong material technology sectors; powder, rapid forming, mechanical property testing and surface technology. It covers the processing chain from green body preparation, optimization of sintering, nitriding, post sinter heat treatment, to modeling and assessment of material behaviour for end-user applications. An iron based powder and a high vanadium high speed steel powder with low and high carbon contents were used in the DMLS and MPSC processes, respectively. The overall aim of the study is to synthesize near net-shaped powder-based components, to characterize pores and microstructure, and to establish a fundamental understanding of failure mechanisms of powder based materials in bending fatigue, thermal fatigue and wear. The study showed the DMLS and MPSC technologies could produce shaped components with a multi-phased structure, controllable nitriding depth and high relative densities in a range of 97 - 99.7 %. Materials' heterogeneity and porosity have detrimental influence on mechanical properties, especially on crack initiation and subsequent propagation.

La conception sur-mesure de matériaux architecturés à l'échelle du milli/centimètre est une stratégie pour développer des matériaux de structure plus performants vis-à-vis de cahiers des charges multifonctionels. Ce travail de thèse s'intéresse en particulier à la conception optimale de panneaux architecturés périodiques, dans le but de combiner des exigences mécaniques de flexion et de cisaillement, ainsi que de conductivité thermique. Le comportement élastique peut être prédit grâce à l'identification sur la cellule périodique des coefficients de la matrice des souplesses équivalente. Ces calculs d'homogénéisation ont été mis en oeuvre par éléments finis pour estimer en particulier les souplesses en flexion et en cisaillement transverse. Après validation expérimentale, cette méthode de calcul constitue un outil d'évaluation des performances mécaniques pour chaque géométrie de cellule périodique (2D ou 3D). À titre d'exemple, et dans un contexte de développement de solutions matériaux architecturés pour l'automobile, la conception de tôles "texturées" est proposée en menant une étude paramétrique à l'aide de cet outil. L'implémentation d'un algorithme d'optimisation topologique couplé à la procédure d'homogénéisation permet d'enrichir les méthodes de conception sur-mesure en élargissant l'espace de recherche des "architectures". Après l'étude modèle du compromis entre flexion et cisaillement, le cas industriel d'un panneau sandwich isolant est traité. Dans ce cas, l'optimisation fournit plusieurs compromis prometteurs entre rigidité en cisaillement et isolation thermique. Ces géométries ont été réalisées et testées, et une nouvelle version améliorée du panneau sandwich a été sélectionnée. / The "material by design" strategy consists in tailoring architectured materials in order to fulfill multi-functional specifications. This PhD study focuses more specifically on designing architectured panels in regards with mechanical compliances (bending and transverse shear), as well as thermal conductivity. Recent advances on periodic homogenization of plates are integrated into a finite elements tool that enables to identify the Reissner-Mindlin effective compliance from the unit cell geometry. The comparison with four-point bending tests illustrates a discussion on the shear loading for homogenization, and its contribution to the global bending stiffness. In a context of architectured steel solutions for automotive, a parametric study is treated on "embossed" steel sheets using this homogenization tool. As a try to enlarge the space of available "architectures", a topological optimization algorithm (using the level-set method) is coupled to the homogenization procedure. The influence of each parameters of the method are studied on the optimization problem of compromising flexural and shear compliances. Finally, the industrial case of an insulation sandwich panel is treated. Few optimized geometries, with a high combination of shear stiffness and thermal insulation, are built, produced and tested. An improved design is highlighted and proposed as next version of this product.

No presente trabalho foi desenvolvido um suporte catalítico monolítico para fins aeroespaciais empregando a manufatura aditiva. Para tanto, foi proposta uma geometria que proporcione um escoamento turbulento, permitindo um maior contato entre o reagente e a superfície do catalisador, proporcionando menor perda de carga ao sistema. Esta nova estrutura foi obtida via manufatura aditiva, através da técnica de Sinterização Seletiva a Laser (SLS) indireta. Para utilizar a técnica SLS e material cerâmico, foi necessário desenvolver um revestimento sobre as partículas de alumina para promover a aderência entre as mesmas durante o processo de manufatura aditiva. Em seguida foram definidos, experimentalmente, os parâmetros de aplicação da técnica SLS para o compósito alumina/poliamida. Por fim, foi fabricado, via SLS, o suporte catalítico na forma monolítica. Após a confecção do suporte monolítico, foi desenvolvido um revestimento composto de pseudo-boemita e nitrato de alumínio e aplicado na superfície do monólito, a fim de expandir a área superficial específica do material. Este aumento da área específica favorece a dispersão da fase ativa, composta de óxidos de cobalto e manganês, na superfície do suporte. A caracterização do catalisador monolítico foi realizada a partir das técnicas de Adsorção de Nitrogênio, Análise Termogravimétrica, Microscopia Eletrônica de Varredura e Espectrometria de Emissão Ótica com Fonte de Plasma (ICP-OES). O desempenho do catalisador monolítico na decomposição do H2O2 concentrado foi analisado via teste de gota, monitorado por câmera de alta velocidade. Os bons resultados obtidos nesta reação apontam esta técnica de obtenção de suporte catalítico monolítico através da manufatura aditiva como uma metodologia promissora a ser empregada em sistemas catalíticos com elevada difusão de massa e calor, mas principalmente em sistemas propulsivos a monopropelente. / This work was developed by the additive manufacture monolithic catalytic support to apply aerospace applications. A geometry was proposed to implement a turbulent flow allowing a better contact with catalytic surface and reagent with a low pressure drop in the system. This new structure was obtained by additive manufacture through indirect Selective Laser Sintering (SLS) technique. Firstly, in order to use the SLS for the ceramic material was developed a coating on the alumina particles to promote a melting between them during addictive manufacturing process. Secondly, the printer parameters SLS was configurated into the alumina/polyamide particle. Finally, the monolithic catalytic support was built via SLS. After the monolithic support building, the pseudo-boehmite and aluminum nitrate coating was developed and applied on the monolithic surface to increase the specific superficial area of the material. This increasing of the specific surface area helps the spread of the active phase to made up of cobalt and manganese oxide in the support surface. The characterization of the monolithic catalyst was carried out using the nitrogen adsorption technique, thermogravimetric analysis, scanning electron microscopy and inductive coupled plasma with optical emission spectrometry. The monolithic catalytic performance in the H2O2 concentrated decomposition was analyzed via drop test monitored by the high-speed camera. The good results of this reaction and such a technique of monolithic catalytic support obtainment through the additive manufacture show that a promising methodology can be used in the catalytic system with high diffusion of mass and heat but mainly, in monopropellant propulsive system.

This thesis aims to investigate the use of additive manufacturing (AM) as a novel manufacturing process for the production of milli-scale chemical reaction systems. Five well developed additive manufacturing techniques; stereolithography (SL), selective laser melting (SLM), fused deposition modelling (FDM), ultrasonic additive manufacture (UAM) and selective laser sintering (SLS) were used to manufacture a number of miniaturised flow devices which were tested using a range of organic and inorganic reactions. SL was used to manufacture a range of functioning milli-scale flow devices from Accura 60 photoresin, with both simple and complex internal channel networks. These devices were used to perform a range of organic and inorganic reactions, including aldehyde and ketone functional group interconversions. Conversion of products within these reactors, were shown to be comparable to commercially available milli-scale coil reactors. More complex designs, which allowed SL parts to be integrated to existing flow and analytical instrumentation, allowed us to develop an automated reaction analysis and optimisation platform. This platform allowed precise control over the reaction conditions, including flow rate, temperature and reagent composition. We also designed a simplex type reaction optimisation software package that could input data in the form of reaction conversions, peak intensities, and thermocouple data, and generate a new set of optimal reaction conditions. SL parts which incorporated embedded analytical components were also manufactured, which allowed us to perform inline reaction analysis as a feedback method for input into the optimisation platform. Stereolithography was shown to be a highly versatile manufacturing method for designing and producing these flow devices, however the process was shown to be still limited by the range of processable materials currently commercially available. SLM was also used to manufacture a number of functioning milli-scale flow devices from stainless steel and titanium, which had simplistic internal channel designs of diameters ranging from 1 to 3 mm. Again, SLM parts were manufactured which incorporated embedded analytical components, which could be integrated into an automated reaction platform. These devices, unlike parts produced via SL, could be attached to heating platforms to allow us to perform high temperature reactions. This control over the reaction temperature formed an essential part of the reaction optimisation platform. These parts were again used to perform a ketone functional group interconversion. Internal structures of these SLM parts were also visualised via micro computed tomography (μCT or microCT) scanning as well as optical microscopy. FDM was used throughout the project as an inexpensive method of prototyping parts which were to be manufactured via more expensive manufacturing processes. This prototyping allowed the optimisation of intricate design features, such as the manufacture of an inline spectroscopic flow cell for integration with a commercially available LC system. FDM was also proposed as a customisable approach to designing and manufacturing flow devices with embedded components, however the current limitations in build resolution and materials choices severely limited the use of FDM for this application. UAM was also proposed as a novel manufacturing process whereby the build process would allow discrete components to be embedded directly into a flow channel. This was demonstrated by embedding a type-k thermocouple across a 2 mm channel. The data from this thermocouple was monitored during a heated reaction, and used as a method of determining the exact reaction conditions the reaction medium was being exposed to. SLS was also proposed as a possible manufacturing method for milli-scale flow devices, however it proved difficult to remove un-sintered powder from parts with internal channel diameters as high as 5 mm. It was shown that this powder was forming a dense semi solid, due to the large degree of shrinkage upon cooling of the SLS parts, which was compressing the powder. More research into optimum processing conditions is required before SLS could be used for the production of intricate channel networks.

Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / In the present work, Dy3+ co-doped SrAl2O4:Eu3+ was produced via proteic sol-gel method, a modified sol-gel route which allows the formation of oxides at lower temperatures than other methods. CO2 laser sintering was used as a method for heat treatment, effective in reducing trivalent europium ions in doped samples. Thermal analysis of the precursors, performed by TG and DTA, revealed that the crystallization of SrAl2O4 phase occurs at approximately 1060 °C. By X-ray diffractometry of the samples characterized before and after sintering was verified monoclinic and hexagonal phases formation. DLS technique revealed the presence of nanosized and micrometric particles, and particle agglomerates, result which was confirmed by SEM images before and after sintering. Micrographs of the fracture surface of a sintered pellet revealed a high degree of densification caused by heat treatment. Photoluminescence measurements showed that the samples after synthesis and before the heat treatment with laser have reddish emission, composed of characteristic narrow emission lines from Eu3+ and more intense emission when the samples are excited at 265 nm. The laser treatment promotes the reduction of Eu3+ to Eu2+ and this effect is confirmed by the presence of a wide emission band in the green region of the spectrum with a maximum emission obtained after excitation at 350 nm. The luminescent decay time of the thermally treated sample was approximately 100 minutes. Via XRF measurements of acquired frits, DTA and TG of the frits, of the pigment and of mixtures of both, and via applications of the mixtures on ceramic plates it was noticed good compatibility in terms of thermal processes, that indicates that the pigment have a potential to be used in ceramic floor tiles. / No presente trabalho, pós cerâmicos de SrAl2O4:Eu3+, Dy3+ foram produzidos pelo método solgel proteico, uma rota de sol-gel modificada, que permite a formação do óxido em temperaturas mais baixas comparativamente a outros métodos. A sinterização a laser de CO2 foi utilizada como método para tratamento térmico, eficiente na redução dos íons trivalentes de európio das amostras dopadas. A análise térmica dos precursores, realizada por meio de DTA e TG, revelou que a cristalização da fase SrAl2O4 acontece em aproximadamente 1060 °C. Por difratometria de raios X verificou-se a formação de fase monoclínica e hexagonal nas amostras caracterizadas antes e após a sinterização. A técnica de EDL revelou a presença de partículas nanométricas, micrométricas e aglomerados de partículas, resultado este que foi confirmado por imagens de MEV de amostras antes e após a sinterização. Micrografias da superfície de fratura de uma pastilha sinterizada a laser revelaram o alto grau de densificação possibilitado pelo tratamento térmico. Medidas de fotoluminescência revelaram que as amostras após a síntese e antes do tratamento térmico a laser apresentam emissão com coloração avermelhada, composta de picos estreitos de emissão característicos do Eu3+ e com emissão mais intensa quando as amostras são excitadas em 265 nm. O tratamento a laser promove a redução do Eu3+ para Eu2+ e este efeito é confirmado pela presença de uma banda larga de emissão na região verde do espectro, com máximo de emissão obtido após excitação em 350 nm. O tempo de decaimento luminescente da amostra tratada termicamente chegou a alcançar aproximadamente 100 minutos. Por meio de medidas de FRX de fritas adquiridas, de DTA e TG de fritas, do pigmento e de misturas entre os dois, e da aplicação das misturas em placas cerâmicas foi possível observar boa compatibilidade em termos dos processos térmicos, o que aponta para um potencial uso do pigmento em placas de revestimento cerâmico.