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- Genre: Doctoral Dissertation
Description
This dissertation aims at developing novel materials and processing routes using alkali activated aluminosilicate binders for porous (lightweight) geopolymer matrices and 3D-printing concrete applications. The major research objectives are executed in different stages. Stage 1 includes developing synthesis routes, microstructural characterization, and performance characterization of a family of economical, multifunctional porous ceramics developed through geopolymerization of an abundant volcanic tuff (aluminosilicate mineral) as the primary source material. Metakaolin, silica fume, alumina powder, and pure silicon powder are also used as additional ingredients when necessary and activated by potassium-based alkaline agents. In Stage 2, a processing route was developed to synthesize lightweight geopolymer matrices from fly ash through carbonate-based activation. Sodium carbonate (Na2CO3) was used in this study to produce controlled pores through the release of CO2 during the low-temperature decomposition of Na2CO3. Stage 3 focuses on 3D printing of binders using geopolymeric binders along with several OPC-based 3D printable binders. In Stage 4, synthesis and characterization of 3D-printable foamed fly ash-based geopolymer matrices for thermal insulation is the focus. A surfactant-based foaming process, multi-step mixing that ensures foam jamming transition and thus a dry foam, and microstructural packing to ensure adequate skeletal density are implemented to develop foamed suspensions amenable to 3D-printing. The last stage of this research develops 3D-printable alkali-activated ground granulated blast furnace slag mixture. Slag is used as the source of aluminosilicate and shows excellent mechanical properties when activated by highly alkaline activator (NaOH + sodium silicate solution). However, alkali activated slag sets and hardens rapidly which is undesirable for 3D printing. Thus, a novel mixing procedure is developed to significantly extend the setting time of slag activated with an alkaline activator to suit 3D printing applications without the use of any retarding admixtures. This dissertation, thus advances the field of sustainable and 3D-printable matrices and opens up a new avenue for faster and economical construction using specialized materials.
ContributorsAlghamdi, Hussam Suhail G (Author) / Neithalath, Narayanan (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Mobasher, Barzin (Committee member) / Abbaszadegan, Morteza (Committee member) / Bhate, Dhruv (Committee member) / Arizona State University (Publisher)
Created2019
Description
Thermal management in modern devices has become increasingly challenging due to the higher heat output from advanced electronics. Effective cooling solutions are essential to enhance performance, extend operational life, and reduce device failure rates. For every 10℃ increase in ambient temperature, device lifespan decreases by 50%, underscoring the need for innovative cooling methods. Micro/minichannel heat sinks have emerged as a promising solution due to their compact size and low thermal resistance. Various mechanisms have been studied to enhance thermal performance, including novel geometries, tailored fluid properties, and the use of ultrasonic waves.Ultrasonic waves have gained attention for their potential to improve heat transfer by disrupting boundary layers and enhancing fluid mixing. This thesis explores whether ultrasound can enhance thermal system performance and investigates the influence of key fluid properties, material selection, and varying parameters such as flow rate, heat input, and ultrasound power on heat transfer and pressure drop.
Three experiments were conducted to evaluate the effects of ultrasonic vibrations on heat transfer and pressure drop across different systems. In the first experiment, ultrasonic vibrations enhanced heat transfer by 13.5% in a circular minichannel heat sink made of stainless steel, using water as the coolant. In the second experiment, using a rectangular minichannel heat sink with water and propylene glycol-water mixtures, ultrasound improved heat transfer, with the highest enhancement observed in deionized water, while the effectiveness decreased with higher propylene glycol concentrations. The third experiment, conducted in a horizontal copper tube, showed a 13.5% heat transfer improvement for water and 11.3% for an ionic liquid. Across all experiments, the effect of ultrasound diminished as flow rates increased, and higher viscosity fluids reduced its effectiveness. Additionally, ultrasound contributed to an increase in pressure drop in all cases.
Overall, these findings highlight the potential of ultrasonic vibrations as an effective technique for enhancing heat transfer. This thesis could provide a basis for future research into ultrasonic technology as a promising technique.
ContributorsAlenezi, Abdulmajeed (Author) / Phelan, Patrick (Thesis advisor) / Shuaib, Abdelrahman (Committee member) / Bhate, Dhruv (Committee member) / Kwon, Beomjin (Committee member) / Al-Mangour, Bandar (Committee member) / Arizona State University (Publisher)
Created2024
Description
Layer-wise extrusion of cement pastes, mortars, or concrete is the most commonly used technique in three-dimensional (3D) concrete printing. Understanding the behavior of the printed binder after placement is crucial for optimizing the properties of 3D-printed elements. This research, conducted in two stages, fresh and hardened state responses, elucidates the post-extrusion mechanics of cementitious binders to enhance print quality. In Stage-1, a novel technique for characterizing 3D printable mortar binders using the green compression test (GCT) is introduced. Equations based on GCT parameters were established to predict buildability, the maximum height that can be sustained without significant deformation or failure. These equations were able to predict buildability and failure mechanisms over time accurately. Stage-2 investigates the mechanical response of hardened 3D printed binders, focusing on inter-layer and inter-filament interfaces, mixture types, and fiber content. Variation in interface positioning and the addition of fibers (0.28% by volume) improved flexural response while maintaining comparable compression strength. However, it did not eliminate anisotropy in compression, and mechanical properties remained inferior to cast counterparts. Next, a numerical model was developed, using cohesive zone finite elements to represent joints and an orthotropic visco-elastic-visco-plastic material model for the bulk filament. This model effectively predicted the mechanical response of 3D printed elements, accurately capturing anisotropy under uniaxial compression. This highlighted the importance of properly characterizing joints and selecting material models. Finally, ultra-high performance 3D printable mixtures were developed using a low water-to-binder ratio mixture with a higher content of water-reducing agent, achieving compressive strengths exceeding 100 MPa at 28 days. This mixture resulted in reduced anisotropy while providing strengths comparable to mold-cast specimens. Incorporating high fiber volume (1.5% by volume) into this mixture significantly enhanced compression and flexural responses. Composite material sections, created by printing different mixtures in various layers, showed comparable mechanical responses while improving cost and environmental efficiency. The findings of this research contribute to precise failure prediction during printing, propose methods for better mechanical responses in printed products, and offer insights into cost-effective and environmentally efficient section design through composite material printing using 3D concrete printing.
ContributorsTripathi, Avinaya (Author) / Neithalath, Narayanan (Thesis advisor) / Mobasher, Barzin (Committee member) / Hoover, Christian (Committee member) / Bhate, Dhruv (Committee member) / Rajan, Subramaniam (Committee member) / Arizona State University (Publisher)
Created2024
Description
Additive manufacturing (AM) enables design freedom previously not attainable with traditional manufacturing techniques. By developing a method of integrating heat pipe geometry into printed parts as a monolithic structure, designers can potentially increase thermal performance in a wide variety of components such as radiators. Traditional manufacturing of high temperature radiators, for example, involves heat-pipe-to-fin interfaces which introduce contact resistances and thermal stresses arising from coefficient of thermal expansion (CTE) mismatches. A monolithic additively manufactured heat pipe radiator (HPR) could significantly reduce these detrimental effects to performance.The goal of this research is to develop and design AM heat pipes, characterize their performance, and integrate these heat pipes into a functional device, an AM Monolithic Heat Pipe Radiator (MHPR). These MHPR devices could potentially improve thermal management for applications such as nuclear spacecraft propulsion and hypersonics.
This thesis specifically explores AM produced Inconel 718 to produce functional wicking structures. During the study several design approaches for creating heat pipe wicks with AM processes were explored and proposed for the first time in three categories as structured, sintered, and rastered approaches. Several aspects of wick design were studied to understand their influence on fluid wicking performance including porosity, print parameter selection, surface oxidation, print orientation, working fluid interaction, permeability, capillary pressure, pore size, and performance ratio. Manufacturing defect modes for AM wicks were also studied.
This thesis identified the rastered wicking strategy, with high hatch spacings and printed in the vertical print orientation, as the design strategy with the highest overall performance for monolithic HPR applications. The sintered wicking strategy was found to perform well when designs had thin wick regions in the horizontal print orientation and was less prone to manufacturing defects. Oxidation of the Inconel wicks greatly improved the wettability of the wick surface when using water as a working fluid but was less influential with ethanol. This thesis uncovers the important role of both surface assisted wetting and geometry assisted transport channels for superior wick performance. Several monolithic HPR prototypes were produced using AM and successfully tested in space-like conditions.
ContributorsNoe, Cameron Scott (Author) / Bhate, Dhruv (Thesis advisor) / Phelan, Patrick (Committee member) / Kwon, Beomjin (Committee member) / Arizona State University (Publisher)
Created2024
Description
Since their invention in the 19th century, polymers have played an essential role, yet their full potential in biomedicine remains largely untapped. Biocompatible polymers, known for their flexibility, accessibility, and modifiability, hold promise in creating complex biomimetic structures for bioscaffolds and biosensors. 3D printing, an emerging manufacturing technique, enables on-demand production of intricate structures, offering significant potential for personalized medicine and advanced biomedical engineering. This thesis focuses on designing and developing polymer-based bioscaffolds and biosensors using 3D printing. Chapter 1 provides an all-round introduction to common 3D printing techniques and polymeric biomaterials, especially biodegradable polymers. In Chapter 2, a gill-mimicking thermoelectric generator (TEG) was created to harvest body temperature and monitor bio-signals without external power. The out-of-plane geometry is obtained with fused deposition modeling (FDM), which is crucial for effective contact with various curved surfaces. Further improvements in biocompatibility enable the material to be implanted in vivo. Chapter 3 discusses UV-facilitated DIW printing for pelvic organ prolapse (POP) tissue scaffolds, featuring crosslink strategies for native tissue-like mechanical behavior. The double network comprises thiol-ene UV-initiated chemical bonds and alkaline-induced crystal regions as physical crosslink nodes. The crosslink density affects the degradation rate of the scaffold, enabling a slow degradation behavior beneficial to the recovery of the injured tissue. Chapter 4 presents a novel artificial artery design with varying moduli and natural polymers for bypass surgeries. The inner and outer layers of the conduit were stretched successively under different strains, endowing the vessel with varying moduli. Natural polymers were utilized to achieve low cytotoxicity and promote adequate cell adhesion. Additionally, the gelation behavior and the ink composition suitable for extrusion with a DIW platform were thoroughly studied. Image analysis, finite element analysis, and machine learning were employed to substantiate the findings regarding mechanical properties, extrusion quality, and printing fidelity in Chapters 3 and 4. This combination of computer-assisted analysis with experimental results enhances the robustness of the studies. Lastly, Chapter 5 provides an outlook and perspectives on the applications of biocompatible polymeric materials manufactured by 3D printing in the field of health applications.
ContributorsZhu, Yuxiang (Author) / Li, Xiangjia (Thesis advisor) / Vernon, Brent (Committee member) / Bhate, Dhruv (Committee member) / Guo, Shenghan (Committee member) / Song, Kenan (Committee member) / Arizona State University (Publisher)
Created2024
Description
The conversion of H2S enables the recycling of a waste gas into a potential source of hydrogen at a lower thermodynamic energy cost as compared to water splitting. However, studies on the photocatalytic decomposition of H2S focus on traditional deployment of catalyst materials to facilitate this conversion, and operation only when a light source is available. In this study, the efficacy of Direct Ink Written (DIW) luminous structures for H2S conversion has been investigated, with the primary objective of sustaining H2S conversion when a light source has been terminated. Additionally, as a secondary objective, improving light distribution within monoliths for photocatalytic applications is desired. The intrinsic illumination of the 3D printed monoliths developed in this work could serve as an alternative to monolith systems that employ light transmitting fiber optic cables that have been previously proposed to improve light distribution in photocatalytic systems. The results that were obtained demonstrate that H2S favorable adsorbents, a wavelength compatible long afterglow phosphor, and a photocatalyst can form viscoelastic inks that are printable into DIW luminous monolithic contactors. Additionally, rheological, optical and porosity analyses conducted, provide design guidelines for future studies seeking to develop DIW luminous monoliths from compatible catalyst-phosphor pairs. The monoliths that were developed demonstrate not only improved conversion when exposed to light, but more significantly, extended H2S conversion from the afterglow of the monoliths when an external light source was removed. Lastly, considering growing interests in attaining a global circular economy, the techno-economic feasibility of a H2S-CO2 co-utilization plant leveraging hydrogen from H2S photocatalysis as a feed source for a downstream CO2 methanation plant has been assessed. The work provides preliminary information to guide future chemical kinetic design characteristics that are important to strive for if using H2S as a source of hydrogen in a CO2 methanation facility.
ContributorsAbdullahi, Adnan (Author) / Andino, Jean (Thesis advisor) / Phelan, Patrick (Thesis advisor) / Bhate, Dhruv (Committee member) / Wang, Robert (Committee member) / Huang, Huei-Ping (Committee member) / Arizona State University (Publisher)
Created2023
Description
Additive manufacturing, also known as 3D printing, has revolutionized modern manufacturing in several key areas: complex geometry fabrication, rapid prototyping and iteration, customization and personalization, reduced material waste, supply chain flexibility, complex assemblies and consolidated parts, and material innovation. As the technology continues to evolve, its impact on manufacturing is expected to grow, driving further innovation and reshaping traditional production processes. Some innovation examples in this field are inspired by natural or bio-systems, such as honeycomb structures for internal morphological control to increase strength, bio-mimetic composites for scaffold structures, or shape memory materials in 4D printing for targeted drug delivery. However, the technology is limited by its ability to manipulate multiple materials, especially tuning their submicron characteristics when they show non-compatible chemical or physical features. For example, the deposition and patterning of nanoparticles with different dimensions have seen little success, except in highly precise and slow 3D printing processes like aerojet or electrohydrodynamic. Taking inspiration from the layered patterns and structures found in nature, this research aims to demonstrate the development and versatility of a newly developed ink-based composite 3D printing mechanism called multiphase direct ink writing (MDIW). The MDIW is a multi-materials extrusion system, with a unique nozzle design that can accommodate two immiscible and non-compatible polymer or nano-composite solutions as feedstock. The intricate internal structure of the nozzle enables the rearrangement of the feedstock in alternating layers (i.e., ABAB...) and multiplied within each printed line. This research will first highlight the design and development of the MDIW 3D printing mechanism, followed by laminate processing to establish the requirements of layer formation in the XY-axis and the effect of layer formation on its microstructural and mechanical properties. Next, the versatility of the mechanism is also shown through the one-step fabrication of shape memory polymers with dual stimuli responsiveness, highlighting the 4D printing capabilities. Moreover, the MDIW's capability of dual nanoparticle patterning for manufacturing multi-functional carbon-carbon composites will be highlighted. Comprehensive and in-depth studies are conducted to investigate the morphology-structure-property relationships, demonstrating potential applications in structural engineering, smart and intelligent devices, miniature robotics, and high-temperature systems.
ContributorsRavichandran, Dharneedar (Author) / Nian, Qiong (Thesis advisor) / Song, Kenan (Committee member) / Green, Matthew (Committee member) / Jin, Kailong (Committee member) / Bhate, Dhruv (Committee member) / Arizona State University (Publisher)
Created2024
Description
Achieving a viable process for advanced manufacturing of ceramics and metal-ceramic composites is a sought-after goal in a wide range of fields including electronics and sensors for harsh environments, microelectromechanical devices, energy storage materials, and structural materials, among others. In this dissertation, the processing, and manufacturing of ceramics and ceramic composites are addressed, specifically, a process for three-dimensional (3D) printing of polymer-derived ceramics (PDC), and a process for low-cost manufacturing as well as healing of metal-ceramic composites is demonstrated.Three-dimensional printing of ceramics is enabled by dispensing the preceramic polymer at the tip of a moving nozzle into a gel that can reversibly switch between fluid and solid states, and subsequently thermally cross-linking the entire printed part “at once” while still inside the same gel was demonstrated. The solid gel converts to fluid at the tip of the moving nozzle, allowing the polymer solution to be dispensed and quickly returns to a solid state to maintain the geometry of the printed polymer both during printing and the subsequent high-temperature (160 °C) cross-linking. After retrieving the cross-linked part from the gel, the green body is converted to ceramic by high-temperature pyrolysis. This scalable process opens new opportunities for low-cost and high-speed production of complex three-dimensional ceramic parts and will be widely used for high-temperature and corrosive environment applications, including electronics and sensors, microelectromechanical systems, energy, and structural applications.
Metal-ceramic composites are technologically significant as structural and functional materials and are among the most expensive materials to manufacture and repair. Hence, technologies for self-healing metal-ceramic composites are important. Here, a concept to fabricate and heal co-continuous metal-ceramic composites at room temperature were demonstrated. The composites were fabricated by infiltration of metal (here Copper) into a porous alumina preform (fabricated by freeze-casting) through electroplating; a low-temperature and low-cost process for the fabrication of such composites. Additionally, the same electroplating process was demonstrated for healing damages such as grooves and cracks in the original composite, such that the healed composite recovered its strength by more than 80%. Such technology may be expanded toward fully autonomous self-healing structures.
ContributorsMahmoudi, Mohammadreza (Author) / Minary-Jolandan, Majid (Thesis advisor) / Rajagopalan, Jagannathan (Committee member) / Cramer, Corson (Committee member) / Kang, Wonmo (Committee member) / Bhate, Dhruv (Committee member) / Arizona State University (Publisher)
Created2022
Description
Applications such as heat exchangers, surface-based cellular structures, rotating blades, and waveguides rely on thin metal walls as crucial constituent elements of the structure. The design freedom enabled by laser powder bed fusion has led to an interest in exploiting this technology to further the performance of these components, many of which retain their as-built surface morphologies on account of their design complexity. However, there is limited understanding of how and why mechanical properties vary by wall thickness for specimens that are additively manufactured and maintain an as-printed surface finish. Critically, the contributions of microstructure and morphology to the mechanical behavior of thin wall laser powder bed fusion structures have yet to be systematically identified and decoupled. This work focuses on elucidating the room temperature quasi-static tensile and high cycle fatigue properties of as-printed, thin-wall Inconel 718 fabricated using laser powder bed fusion, with the aim of addressing this critical gap in the literature. Wall thicknesses studied range from 0.3 - 2.0 mm, and the effects of Hot Isostatic Pressing are also examined, with sheet metal specimens used as a baseline for comparison. Statistical analyses are conducted to identify the significance of the dependence of properties on wall thickness and Hot Isostatic Pressing, as well as to examine correlations of these properties to section area, porosity, and surface roughness. A thorough microstructural study is complemented with a first-of-its-kind study of surface morphology to decouple their contributions and identify underlying causes for observed changes in mechanical properties. This thesis finds that mechanical properties in the quasi-static and fatigue framework do not see appreciable declines until specimen thickness is under 0.75 mm in thickness. The added Hot Isostatic Pressing heat treatment effectively closed pores, recrystallized the grain structure, and provided a more homogenous microstructure that benefits the modulus, tensile strength, elongation, and fatigue performance at higher stresses. Stress heterogeneities, primarily caused by surface defects, negatively affected the thinner specimens disproportionately. Without the use of the Hot Isostatic Pressing, the grain structure remained much more refined and benefitted the yield strength and fatigue endurance limit.
ContributorsParadise, Paul David (Author) / Bhate, Dhruv (Thesis advisor) / Chawla, Nikhilesh (Committee member) / Azeredo, Bruno (Committee member) / Jiao, Yang (Committee member) / Arizona State University (Publisher)
Created2022
Description
The design of energy absorbing structures is driven by application specific requirements like the amount of energy to be absorbed, maximum transmitted stress that is permissible, stroke length, and available enclosing space. Cellular structures like foams are commonly leveraged in nature for energy absorption and have also found use in engineering applications. With the possibility of manufacturing complex cellular shapes using additive manufacturing technologies, there is an opportunity to explore new topologies that improve energy absorption performance. This thesis aims to systematically understand the relationships between four key elements: (i) unit cell topology, (ii) material composition, (iii) relative density, and (iv) fields; and energy absorption behavior, and then leverage this understanding to develop, implement and validate a methodology to design the ideal cellular structure energy absorber. After a review of the literature in the domain of additively manufactured cellular materials for energy absorption, results from quasi-static compression of six cellular structures (hexagonal honeycomb, auxetic and Voronoi lattice, and diamond, Gyroid, and Schwarz-P) manufactured out of AlSi10Mg and Nylon-12. These cellular structures were compared to each other in the context of four design-relevant metrics to understand the influence of cell design on the deformation and failure behavior. Three new and revised metrics for energy absorption were proposed to enable more meaningful comparisons and subsequent design selection. Triply Periodic Minimal Surface (TPMS) structures were found to have the most promising overall performance and formed the basis for the numerical investigation of the effect of fields on the energy absorption performance of TPMS structures. A continuum shell-based methodology was developed to analyze the large deformation behavior of field-driven variable thickness TPMS structures and validated against experimental data. A range of analytical and stochastic fields were then evaluated that modified the TPMS structure, some of which were found to be effective in enhancing energy absorption behavior in the structures while retaining the same relative density. Combining findings from studies on the role of cell geometry, composition, relative density, and fields, this thesis concludes with the development of a design framework that can enable the formulation of cellular material energy absorbers with idealized behavior.
ContributorsShinde, Mandar (Author) / Bhate, Dhruv (Thesis advisor) / Peralta, Pedro (Committee member) / Liu, Yongming (Committee member) / Jiao, Yang (Committee member) / Kwon, Beomjin (Committee member) / Arizona State University (Publisher)
Created2023