Additive manufacturing introduces a new design paradigm that allows the fabrication of geometrically complex parts that cannot be produced by traditional manufacturing and assembly methods. Using a cellular heat exchanger as a motivational example, this thesis investigates the creation of a hybrid manufacturing approach that combines selective laser sintering with an electroforming process to produce complex, hollow, metal geometries. The developed process uses electroless nickel plating on laser sintered parts that then undergo a flash burnout procedure to remove the polymer, leaving a complex, hollow, metal part. The resulting geometries cannot be produced directly with other additive manufacturing systems. Copper electroplating and electroless nickel plating are investigated as metal coating methods. Several parametric parts are tested while developing a manufacturing process. Copper electroplating is determined to be too dependent on the geometry of the part, with large changes in plate thickness between the exterior and interior of the tested parts. Even in relatively basic cellular structures, electroplating does not plate the interior of the part. Two phases of electroless nickel plating combined with a flash burnout procedure produce the desired geometry. The tested part has a density of 3.16g/cm3 and withstands pressures up to 25MPa. The cellular part produced has a nickel plate thickness of 800µm and consists of 35% nickel and 65% air (empty space). Detailed procedures are included for the electroplating and electroless plating processes developed. / Master of Science

15-5PH stainless steel is an important alloy in the aerospace, chemical, and nuclear industries for its high strength and corrosion resistance at high temperature. Thus, this material is a good candidate for processing development in the direct metal laser sintering (DMLS) branch of additive manufacturing. The chemistry and microstructure of this alloy processed via DMLS was compared to its conventionally cast counterpart through various heat treatments as part of a characterization effort. The investigation utilized optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-Ray diffractometry (XRD), energy dispersive X-Ray spectroscopy (EDS) and glow discharge atomic emission spectrometry (GDS) techniques. DMLS processed samples contained a layered microstructure in which the prior austenite grain sizes were relatively smaller than the cast and annealed prior austenite grain size. The largest of the quantifiable DMLS prior austenite grains had an ASTM grain size of approximately 11.5-12 (6.7?m to 5.6?m, respectively) and the cast and annealed prior austenite grain size was approximately 7-7.5 (31.8µm to 26.7µm, respectively), giving insight to the elevated mechanical properties of the DMLS processed alloy. During investigation, significant amounts of retained austenite phase were found in the DMLS processed samples and quantified by XRD analysis. Causes of this phase included high nitrogen content, absorbed during nitrogen gas atomization of the DMLS metal powder and from the DMLS build chamber nitrogen atmosphere. Nitrogen content was quantified by GDS for three samples. DMLS powder produced by nitrogen gas atomization had a nitrogen content of 0.11 wt%. A DMLS processed sample contained 0.08 wt% nitrogen, and a conventionally cast and annealed sample contained only 0.019 wt% nitrogen. In iron based alloys, nitrogen is a significant austenite promoter and reduced the martensite start and finish temperatures, rendering the standard heat treatments for the alloy ineffective in producing full transformation to martensite. Process improvements are proposed along with suggested future research.

Published Article / In this paper the time and cost parameters of tooling manufacturing by metal casting in rapid prototyping sand moulds are assessed and comparison is made with alternative tool making processes such as computer numerical control machining and investment casting (Paris Process). To that end two case studies obtained from local companies were carried out. The tool manufacturing was conducted according to a five steps process chain referred to as Rapid Casting for Tooling (RCT). These steps include CAD modelling, casting simulation, rapid prototyping, metal casting and finishing operations. In particular the Rapid Prototyping (RP) step for producing the sand moulds was achieved with the aid of an EOSINT S 550 Laser Sintering machine and a Spectrum 510 Three Dimensional Printer. The results indicate that RP is the rate determining step and cost driver of the proposed tooling manufacturing technique. In addition it was found that this tool making process is faster but more expensive than machining and investment casting.

Published Article / Rapid Manufacturing (RM) has emerged over the past few years as a potential technology to successfully produce patient-specific implants for maxilla/facial and cranial reconstructive surgeries. However, in the area of spinal implants, customization has not yet come to the forefront and with growing capabilities in both software and manufacturing technologies, these opportunities need to be investigated and developed wherever possible. The possibility of using Computed Tomography (CT) and Rapid Manufacturing (RM) technologies to design and manufacture a customized, patient-specific intervertebral implant, is investigated. Customized implants could aid in the efforts to reduce the risk of implant subsidence, which is a concern with existing standard implants. This article investigates how accurately the geometry of a customized artificial intervertebral disc (CAID) can represent the inverse geometry of a patient's vertebral endplates. The results indicate that the endplates of a customized disc implant can be manufactured to a calculated average error of 0.01mm within a confidence interval of 0.022mm, with 95% confidence, when using Direct Metal Laser Sintering.

This research details an investigation into processes employing laser technology to create design-led three-dimensional textiles. An analysis of historical and contemporary methods for making three-dimensional textiles categorises these as processes that construct a three-dimensional textile, processes that apply or remove material from an existing textile to generate three-dimensionality or processes that form an existing textile into a three-dimensional shape. Techniques used in these processes are a combination of joining, cutting, forming or embellishment. Laser processing is embedded in textile manufacturing for cutting and marking. This research develops three novel processes: laser-assisted template pleating which offers full design freedom and may be applied to both textile and non-textile materials. The language of origami is used to describe designs and inspire new design. laser pre-processing of cashmere cloth which facilitates surface patterning through laser interventions in the manufacturing cycle. laser sintering on textile substrates which applies additive manufacturing techniques to textiles for the generation of three-dimensional surface patterning and structures. A method is developed for determining optimum parameters for laser processing materials. It may be used by designers for parameter selection for processing new materials or parameter modification when working across systems.

This research introduces a method to aid the design of products or parts to be made using Additive Manufacturing (AM), particularly the laser sintering (LS) system. The research began with a literature review that encompassed the subjects of design and AM and through this the need for an assistive design approach for AM was identified. Undertaking the literature review also confirmed that little has been done in the area of supporting the design of AM parts or products. Preliminary investigations were conducted to identify the design factors to consider for AM. Two preliminary investigations were conducted, the first investigation was conducted to identify the reasons for designing for AM, the need for a design support tool for AM and current challenges of student industrial designers designing parts or products for AM, and also to identify the type of design support they required. Further investigation were conducted to examine how AM products are developed by professional industrial designers and to understand their design processes and procedures. The study has identified specific AM enabled design features that the designers have been able to create within their case study products. Detailed observation of the case study products and parts reveals a number of features that are only economical or possible to produce with AM. A taxonomy of AM enabled design features was developed as a precursor for the development of a computer based design tool. The AM enabled design features was defined as a features that would be uneconomical or very expensive to be produced with conventional methods. The taxonomy has four top-level taxons based on four main reasons for using AM, namely user fit requirements, improved product functionality requirements, parts consolidation requirements and improvement of aesthetics or form requirements. Each of these requirements was expanded further into thirteen sub categories of applications that contained 106 examples of design features that are only possible to manufacture using AM technology. The collected and grouped design features were presented in a form of a database as a method to aid product design of parts or products for AM. A series of user trials were conducted that showed the database enabled industrial designers to visualise and gather design feature information that could be incorporated into their own design work. Finally, conclusions are drawn and suggestions for future work are listed. In summary, it can be concluded that this research project has been a success, having addressed all of the objectives that were identified at its outset. From the user trial results, it is clear to see that the proposed tool would be an effective tool to support product design for AM, particularly from an educational perspective. The tool was found to be beneficial to student designers to take advantage of the design freedom offered by AM in order to produce improved product design. As AM becomes more widely used, it is anticipated that new design features will emerge that could be included in future versions of the database so that it will remain a rich source of inspirational information for tomorrow s industrial designers.

This thesis is focused on achieving materials with non-equilibrium structures fabricated by high-energy laser sintering. The chosen precursor materials have rigid and inert structures like high-melting point ceramics or metals. It was necessary to use real-time monitoring of temperature and spectrum profiles for selecting the optimal laser parameters for the laser sintering process. This monitoring was done by an off-axial setup that also controls the surface morphologies during the laser irradiation process. The laser focal spot receives very high temperatures and subsequent extreme cooling rates within a short time period. New non-equilibrium structures will emerge ruled by kinetics, huge temperature gradients or stresses and freeze by quenching in solid state. These material structures were found to form at different length scales from nano- to macro-level, frequently by a hierarchical ordering. This opens a method to engineer materials with both hierarchical and non-equilibrium structures by a single operation in both metal and ceramics by laser sintering. In the Co-Cr-Mo alloy system, structures on three levels of lengths were observed, namely i) nano-level structures dominated by the grain boundary segregation; ii) micron-level structures characterized by the interlocked clusters of columns; and iii) macro-level structures defined by the selected laser scan patterns. The non-equilibrium structures of the Co-Cr-Mo alloy are related to mechanical, corrosion and bio-compatibility properties. In ZrO2 ceramics, the final product had a non-equilibrium nano- and micron-sized structure created by uneven absorption of laser energy and rupture. The structure inside the micron-sized grains is formed through ordered coalescence of nano-crystals. Properties of the laser sintered materials were established and related to the observed structures. The materials properties might be tailored by controlling the structures in different levels and potential applications of the new materials will be given. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Accepted. Paper 3: Accepted. Paper 4: Submitted. Paper 5: Manuscript.</p>

Cette étude s'inscrit dans le cadre du développement de nouveaux matériaux pour la fabrication additive. Notre objectif est la fabrication de pièces comprenant un alliage métallique complexe (CMA) à l'aide d'un laser UV de stéréolithographie. L'alliage choisi est un alliage quasicristallin dominé par une phase icosaédrique du système AlCuFeB. Des poudres brutes d'atomisations ont été caractérisées par diffractions des rayons X et analyse thermique différentielle. Nous avons montré une bonne absorbance optique de la poudre dans le domaine UV-visible qui rend possible un début de frittage sous l'effet du laser correspondant à la formation de pontages entre les grains à une température d'environ 820°C. Concernant la fabrication à partir d'une suspension de poudres dans un liant, nous avons étudié les propriétés de mouillage des particules AlCuFeB et optimisé un mélange avec une résine époxy chargée par 20 % vol. de particules CMA. L'absorption optique de la suspension dans le domaine UV est suffisante pour fabriquer une pièce composite par stéréolithographie. La granulométrie utilisée est inférieure à 25 µm. Nous avons ainsi réussi à fabriquer des pièces de 14 mm de hauteur, en additionnant des couches de 50 µm. À partir des pièces réalisées, nous avons caractérisé la dureté et les propriétés tribologiques de ce nouveau matériau composite. La dureté des pièces ainsi fabriquées est supérieure à celle de la résine seule et atteint 88 Shore D. Nous avons également mis en évidence une amélioration de 30 % du coefficient de frottement et une diminution du volume d'usure de 40 % par rapport au matériau de la matrice époxy. Ces propriétés rendent attractif ce nouveau matériau composite pour la fabrication par stéréolithographie / This study aimed at developing new materials for additive manufacturing. We focused on producing parts containing complex metallic alloys (CMA) using a UV laser used for stereolithography. The selected intermetallic is a quasicrystalline alloy dominated by the icosahedral phase in the system AlCuFeB. The raw powders produced by gas atomization were characterized by X-ray diffraction and differential thermal analysis. The powders exhibit good optical absorption properties in the UV-visible range allowing direct laser sintering as evidenced by the formation of bridges between the grains at a temperature of about 820°C. In a second step, we have considered the manufacturing of parts made of a suspension of CMA powders in a binder. We have studied the wetting properties of the particles AlCuFeB and optimized a mixture consisting of an epoxy resin filled with 20 % vol. of CMA particles. The optical absorption of the suspension in the UV range was sufficient to produce composite parts by stereolithography. The particle size used was smaller than 25 micrometers. We have managed to make parts reaching 14 mm in height by adding layers with a thickness of 50 microns. Using test samples, we have characterized the hardness and the tribological properties of this new composite material. The hardness of the parts produced by stereolithography is larger than that of epoxy parts and reaches 88 Shore D. We have also shown a 30 % reduction of the friction coefficient as well as a 40 % reduction of wear losses compared to the epoxy matrix. These properties make attractive this new composite material for stereolithography applications

<p></p><p>Flexible electronics involve electronic circuits fabricated on flexible substrates. They have promising applications in wearable devices and flexible sensors etc. and have thus attracted much research interest in recent years. The working environment of flexible electronic devices may require them to go through repeating deformations, during which cracks may generate and grow in the metallic components of the devices, reducing service life of these devices. To address such challenges, it is desirable to investigate methods to improve the reliability of flexible electronics in these working conditions. </p> <p>This research reported here will focus on topics related to laser-based fabrication of carbon nanotube-metal composites on flexible substrates: </p> <p>Experimental studies were carried out to investigate the structures and properties of carbon nanotube – metal composites produced by a laser-based fabrication process on flexible substrates. Extensive characterizations and testes were carried out, including measurements of electrical resistivity of laser-sintered material, characterizations with SEM, TEM, EDS and XPS, and mechanical performance tests (bending fatigue test, static tensile test and adhesion test). The experimental study suggests that the laser-fabricated metal composites have promising potentials to help enhancing reliability and durability of metal components in flexible electronic devices. </p> <p>A molecular dynamics model was also developed to study the coalescence of metal nanoparticles (gold NPs in this study) around the end of a multi-walled carbon nanotube (MWCNT) and their interaction with the CNT at elevated temperatures. The MD model was first tested by comparing the MD-predicted NP melting points with experiment-deduced results from the literature. Then the coalescence of five 3-nm Au NPs around the end of a MWCNT and their interactions with the CNT were studied with MD simulations. The molecular system was studied under different elevated temperatures and for different carbon nanotube diameters, and the simulation results were analyzed and discussed. </p><br><p></p>

O titânio é amplamente empregado em indústrias químicas, geração de energia, aeroespaciais e biomédicas, pois além de suas boas propriedades mecânicas e resistência à corrosão, apresenta também boa biocompatibilidade. Porém, quando usado, por exemplo, em turbinas a vapor é necessário aumentar ainda mais sua resistência à corrosão em altas temperaturas. Ou quando usado em odontologia a cor acinzentada do metal compromete as reabilitações orais. Sendo assim, torna-se interessante o recobrimento do titânio com uma camada cerâmica, sendo a 3YTZP (zircônia tetragonal policristalina) adequada a tal aplicação, pois além de apresentar resistência mecânica, boa resistência a ciclos térmicos, apresenta boa biocompatibilidade. Neste trabalho foi feito o estudo do recobrimento do titânio com 3YTZP utilizando a técnica da deposição eletroforética além de realizar a irradiação do filme cerâmico utilizando o laser contínuo Nd:YAG com a finalidade de sinterização. O pó de 3YTZP foi obtido pela rota de coprecipitação de óxidos em meio amoniacal e caracterizada por DRX e MEV-FEG. Os resultados de DRX do pó mostraram a presença das fases tetragonal e monoclínica, e pelas micrografias observa-se que as partículas têm estruturas alongadas em formas de bastonetes. Por meio da densificação dos corpos cerâmicos foi possível observar boa sinterabilidade do pó. Como substrato para EPD foram utilizadas chapas de titânio (15 mm x 15 mm) e foram caracterizadas por DRX, que confirmou apenas a presença da fase &alpha; do Ti, indicando assim que são de titânio comercialmente puro. As chapas foram atacadas quimicamente com ácido sulfúrico 50% em volume por 10s. A deposição eletroforética foi realizada com as suspensões de 75%vol.acetona:25%.vol.etanol a 30 V por 20, 45 e 60 segundos; 50%vol.acetona:50%vol.etanol a 20 V por 30, 45 e 60 segundos; 25%vol.acetilacetona:75%vol.etanol a 60 V por 20, 40 e 60 segundos e a 40 V por 20 segundos; e com acetilacetona pura a 60 V por 20, 40 e 60 segundos e a 40 V por 20 e 40 segundos. Por meio das microscopias ópticas dos filmes depositados pode-se observar que a melhor condição de deposição foi utilizando a suspensão de acetilacetona a 40 V por 20 segundos, gerando filmes homogêneos e sem trincas. Foram realizados cinco ensaios de irradiação com lazer a fim de alcançar uma condição ideal de sinterização. As condições fixas para todos os ensaios foram energia de 0,5 J, coeficiente de duração de pulso (Tp) de 10 ms e coeficiente de repetição de pulso de 10 Hz. No decorrer dos ensaios foi variada a fluência do laser e o número de incidência. As amostras irradiadas foram caracterizadas por microscopia óptica e eletrônica, DRX e Scratch, e verificou-se que a melhor condição de irradiação foi utilizando a fluência de 120 J/cm2 para o número de incidência do laser de igual a 27. / Titanium is widely used in chemical, power generatin, aerospace and biomedical industries because of you good mechanical properties, corrosion resistance and good biocompatibility. However, when is used, for example, in steam turbines is necessary increase the corrosion resistance at high temperature. Or when is used in dentistry, when the gray color compromisse the aesthetics rehab. In this case, it becomes interesting to coat the titanium with a ceramic layers, and 3YTZP (Yttria-stabilized tetragonal zirconia) is suitable for this application, because it has good mechanical properties, good resistance to thermal cycles and good biocompatibility. In this work it was studied the coating of titanium with 3YTZP using electrophoretic deposition technique in addition irradiation of films using the Nd:YAG continuous laser. The 3YTZP powder was obtained by hydroxide coprecipitation route in ammoniacal medium and characterized by XDR and SEM. The XDR results shower presence os monoclinic and tetragonal phases, and micrographs it can be observed the the particles agglomerates. These particles have elongated structure. Through the densification of the ceramic bodies it was possible to observe good sinterability of the powder. Was used as the substrate to EPD titanium plates (dimension 15 mm x 15 mm), and was characterized by XRD, that show presence of &alpha;-fase, thus indicating that they are commercially pure titanium. The plates were chemically etched with 50% vol. Sulfuric acid for 10 s. Electrophoretic deposition was performed with suspensions of 75%vol.acetone: 25%.vol.ethanol at 30 V for 20, 45 e 60 seconds; 50%vol.acetone:50%vol.ethanol at 20 V for 30, 45 e 60 seconds; 25%vol.acetylacetone:75%vol.ethanol at 60 V for 20, 40 e 60 seconds and at 40 V for 20 seconds; and with pure acetylacetone at 60 V for 20, 40 e 60 seconds and at 40 V for 20 e 40 seconds. From observation in an optical microscope of the deposited films, we concluded that the best deposition condition was the acetylacetone suspension at 40 V for 20 seconds, being homogeneous films and free of cracks. Five laser irradiation tests were performed in order to achieve an optimum sintering condition. The fixed conditions for all the tests were energy of 0.5 J, pulse duration coefficient (Tp) of 10 ms and pulse repetition coefficient of 10 Hz. In the course of the tests, the laser fluency and the laser incidence number were varied. The irradiated samples were characterized by optical and electron microscopy, XRD and Scratch, and it was found that the best irradiation condition was using fluency of 120 J/cm2 and laser incidence number of 27.