The overall goal of this work is to predict the mechanical response of an as-built Ti-6Al-4V directed energy deposition component by a dislocation mechanics-based internal state variable model based on the component's geometry and processing parameters. Previous research has been performed to connect additive manufacturing (AM) process parameters including laser power and scanning strategy to different aspects of part quality, such as porosity, mechanical properties, fatigue life, microstructure, residual stresses, and distortion. The lack of predictive capabilities to fully estimate residual stresses and distortion within parts produced via AM have hindered part qualification; however, modeling the AM process can aide in process and geometry optimization compared to traditional trial-and-error methods. The presence of unwanted thermally induced residual stresses and distortion can lead to tolerancing issues, reduced fatigue life, and decreased mechanical performance compared to similar components fabricated with traditional manufacturing methods such as casting and machining. A three-dimensional thermomechanical finite element model calibrated using dual-wave pyrometer thermal image datasets along with temperature- and strain rate-dependent mechanical data is utilized for this work. The purpose of this work is to understand the relationship between a component's temperature history and its resultant distortion and residual stresses.

Additive manufacturing technologies, including inkjet printing, have significantly transformed both research and industry, offering cost-effective and accessible solutions with innovative equipment capabilities. This study focuses on advancing p-type depletion and enhancement-mode poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) through molecular de-doping and rheological measurements, achieving a printing resolution of 30 μm. The versatility of these inks is demonstrated from three distinct perspectives. Firstly, the electrochemical stability of the enhancement-mode behavior opens new possibilities for low-power consumption, stable and sensitive platforms useful for detection of DopamineC and Ascorbic Acid at various concentrations. Secondly, we exemplify the democratization of in-house fabrication through fully printed, all-PEDOT:PSS, transparent, flexible, and bendable paper-based Organic Electrochemical Transistors (OECTs). This showcases the feasibility of employing inkjet printing to create functional electronic devices with ease. Lastly, we explore optimizations that enable deeper personalization by employing multiple material localizations and adjusting the electrical conductivity of OECTs. This engineering approach has resulted in the design of Organic Electrochemical Complementary Amplifiers (OECAs), we incorporated a second formulated enhancement-mode conducting polymer poly(benzimidazobenzophenanthroline) (BBL) as the n-type material to complement the PEDOT:PSS de-doped ink. These developments aim to foster global innovation, representing a significant leap forward in the field of organic electronics and in-house fabrication by complementing this engineering improvement from both fabrication and electrochemistry approaches.

The ongoing energy and environmental crises have pushed the transportation sector, a major greenhouse gas emitter, to seek sustainable fuel and technology alternatives. Natural gas and bio-methane are potential alternatives with numerous advantages over conventional fuels. Adsorbed natural gas (ANG) technology uses porous adsorbent material to store methane efficiently at lower pressures. An issue limiting this technology is the lack of compact tanks with efficient adsorbent packing that increase storage capacity. This study addresses the need for more compact ANG tanks by creating novel binder-less monolithic activated carbon monolith adsorbents with targeted porosity. A template is produced using 3D printing and a commercially available phenolic resin as a filling material. Upon thermal treatment, the 3D-printed template combusts with molecular oxygen in its structure, and the resin is transformed into activated carbon by pyrolysis. Longer activation times led to higher BET surface areas. However, after activation periods beyond 15 minutes, the surface area increase is obtained at the expense of a higher burn-off, which affects the material density. Adsorption of 0.04g/g of methane was measured at 30 bar and 298 K on the activated carbon monolith with the highest BET surface area (516 m2/g). Results in the same conditions on a super high surface area Maxsorb activated carbon were 0.13g/g. Although the methane capacity obtained is lower than in a commercial sample, it was demonstrated that producing an activated carbon monolith with tailored porosity is possible. New techniques for activation should be studied to enhance their gravimetric capacity to make ANG competitive.

Metal Organic Frameworks (MOFs) are a class of porous materials that are predominantly obtained as powders and have been investigated as a solid sorbent for gas separation or carbon capture applications from combustion exhaust gases. The manufacturing of products with MOFs to use them for real life applications is still a major problem. The most common productization method used is to form pellets of the powder MOFs. This has a limitation on the product shape which makes it difficult for it to be used in gas separation applications. This study focuses on using additive manufacturing technique to give MOFs a lattice (mesh-like) geometry which is useful for gas separation applications as the mixture of gases would be able to pass through the lattice structure and be separated due to the inherent MOF properties and characteristics. Two MOFs based on magnesium and manganese salts have been studied in this project. An extrudable paste developed using alginate gel as a binder with these MOFs. With alterations in paste formulations and 3D printer parameters, lattice structures were printed using the two MOFs. CO2 and N2 gas uptakes were measured showing that the structure adsorbs CO2 gas to a higher extend which results in the separation of N2 gas in both materials. When compared to their pristine powder form, other properties of the MOFs such as crystallinity, microstructure, reusability and surface area remain to be preserved after being 3D printed in both cases.

<p>  </p> <p>Monolithic catalyst beds have been used extensively in other industries and are gaining interest for space propulsion applications. Additive manufacturing of monolithic supports allows for catalyst beds with a wider range of geometries than could be produced using conventional methods, potentially allowing for higher performance monoliths that can compete with conventional packed beds in performance. Achieving these gains requires a consistent, even, and well-adhering washcoating procedure for the additively manufactured supports, one which works well on varied geometry and on support materials that can be readily printed. I conducted an extensive development process on improving methods of surface preparation and coating for high temperature ceramic monoliths that resulted in improvements in the state of the art. The materials and methods used are appropriate for rocket grade hydrogen peroxide, hydrazine, or other monopropellants with similar operating temperatures. Using existing published coating methods resulted in uneven coating distribution and poor adhesion. I demonstrate that this was due to the substrate surface morphology producing a hydrophobic effect. Surface morphology plays a significant role in coating coverage and adhesion and differences in initial support surfaces likely account for much of the variation in results seen across the literature. I present a method of controlled thermochemical surface etching using pure sodium hydroxide at 420°C that can reliably produce a roughened hydrophilic surface from a variety of starting morphologies. I also present several modifications to the primer formulation that improve evenness of coverage, the most significant of which is the inclusion of a surfactant at a concentration of 1 g per 36 g water. The surface treatment and coating formulation improvements combine well and produce an even coating with strong adhesion to the substrate. I also conducted preliminary work on the investigation of novel geometric designs for monolithic catalyst beds, and on the reactivity of different transition metal oxide catalysts for rocket grade hydrogen peroxide decomposition. </p>

Additive manufacturing (AM) of parts using a layer by layer approach has seen a rapid increase in application for production of net shape or near-net shape complex parts, especially in the field of aerospace, automotive, etc. Due to the superiority of manufacturing complex shapes with ease in comparison to the conventional methods, interest in these kinds of processes has increased. Among various methods in AM, laser powder bed fusion (LPBF) is one of the most widely used techniques to produce metallic components. As in all manufacturing processes, residual stress (RS) generation during manufacturing is a relevant issue for the AM process. RS in AM are generated due to a high thermal gradient between subsequent layers. The impact of residual stresses can be significant for the mechanical integrity of the built parts and understanding the generation of RS and the effect of AM process parameters is therefore important for a broader implementation of AM techniques. The work presented in this licentiate thesis aims to investigate the influence of build orientation on the RS distribution in AM parts. For this purpose, L-shaped Inconel 718 parts were printed by LPBF in three different orientations, 0°, 45°, and 90°, respectively. Inconel 718 was selected because it is a superalloy widely used for making gas turbine components. In addition, IN718 has in general good weldability which renders it a good material for additive manufacturing. Residual stress distributions in the parts removed from the build plate were measured using neutron diffraction technique. A simple finite element model was developed to predict the residual stresses and the effect of RS relaxation due to the separation of the parts and build plate. The trend of residual stress distribution predicted was in good agreement with experimental results. In general, compressive RS at the part center and tensile RS near the surface were found. However, while the part printed in 0° orientation had the least amount of RS in all three principal directions of part, the part built in 90° orientation possessed the highest amount of RS in both compression and tension. The study has shown that residual stress distributions in the parts are strongly dependent on the building process. Further, it has shown that the relaxation of RS associated with the removal of the parts from the build plate after printing has a great impact on the final distribution of residual stress in the parts. These results can be used as guidelines for choosing the orientations of the part during printing.

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The use of selective laser melting for AlSi10Mg has been gaining a lot of popularity, but unfortunately, there are a great deal of issues surrounding internal porosity. Hot isostatic pressing (HIP) has been used in many instances alongside a standard T6 treatment to reduce porosity, but that typically involves water quenching. The application for this project is meant for the satellite industry, which has tight dimensional tolerances and as such, water quenching is not adequate. Currently, annealing for a stress relief treatment is the only post- processing measure that does not involve water quenching. This project studied a novel direct HIP approach, whereby an argon quench is used after solution annealing. Three different cooling rates were studied within the DHIP process (DHIP-L=50°C/min, DHIP- M=200°C/min, and DHIP-H=400°C/min) and compared to specimens that were stress relieved (SR). Uniaxial tensile testing revealed that the strength and ductility of DHIP-H outperformed the SR condition. The true stress/strain results showed that all DHIP conditions had a superior true strain and true stress at fracture. All DHIP conditions and SR showed evidence of void growth and coalescence. SR fracture is driven through crack initiation, while the DHIP conditions fracture is driven through localized necking. In-situ tensile tests via scanning electron microscopy coupled with μ-DIC revealed that the DHIP conditions feature damage due to particle fracture, while the SR condition experiences strain localization along the interface of Si particles and the α-Al phase. In-situ tensile testing via XCT studied a comparative analysis between DHIP-M and SR and revealed that DHIP-M experiences more void growth and nucleation than the SR condition. / Thesis / Master of Applied Science (MASc)

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