Analysis of Ferroelectric Ceramic Fabricated by Binder Jetting Technology

The M-Lab system from ExOne was used to fabricate 3D structures of BaTiO3 ceramic with applications that include dielectric capacitors, sensors, and integrated circuits. For this project, layer thicknesses of 15 and 30 μm and various percentages of binder saturation were used to fabricate components from powder. An organic binding agent was utilized during the printing process and later burned out at ~600°C prior to sintering. Multiple building parameters and sintering profiles were analyzed and compared in an attempt to obtain dense parts while examining shrinkage percentage variations.Mechanical Engineerin

Fundamentals of Titanium Interactions with Nitrogen and Oxygen

Titanium is a lightweight and attractive metal for use in aerospace, chemical processing, and biomedical industries due to its high strength-to-weight ratio, good oxidation and corrosion resistance, as well as biocompatibility. One important problem with the use of titanium is the embrittlement that accompanies its incorporation of interstitials, most notably oxygen and nitrogen. Since titanium readily dissolves both nitrogen and oxygen, understanding these reactions is fundamental to develop strategies to minimize contamination or to take advantage of these reactions to form nitrides, oxides, or oxynitrides that may exhibit interesting properties for energy storage, biomedical, coatings, or other applications. This research is motivated by the need for improving the fundamental understanding of titanium interactions with nitrogen and oxygen and the nature of its developed phases.Reaction studies were performed at 800°C (to remain in the hcp α-Ti phase) using argon-based environments with three distinct low partial pressures of nitrogen and oxygen. These experiments were performed in two furnace configurations, one of which allowed monitoring of scale evolution in situ using Raman spectroscopy. Characterization of the developed scales relied on scanning and transmission electron microscopy, energy dispersive spectroscopy, focused ion beam, X-ray diffraction, electron diffraction, and Raman spectroscopy. Across environments used, the microstructures show the formation of layered structures with varying porosity throughout. When fast-cooling specimens in the gettered Ar environment (the lowest partial pressure used), the scale consists of mainly nitride phases. Slow-cooling enables the formation of a N-rich hcp-based phase, an oxynitride (TiNxOy) phase, Ti2O3 in a corundum structure, Magnéli phases, and rutile. Ultra-high purity Ar studies show an additional range of oxygen orderings in the substrate when slow-cooling the specimen after the desired dwell time. Analysis of the specimens exposed to gettered and ultra-high purity Ar also shows the formation of twinned fcc TiN or oxynitride structures and an orientation relationship between the fcc phase and the underlying hcp Ti substrate. Partial dislocations are proposed to play a role in the hcp Ti to fcc TiN/TiNxOy transformation and potentially in the formation of voids at the metal-scale interface. Reacting titanium to a 1%O2-Ar environment hinders the formation of nitride or oxynitride phases and develops multiple layers of rutile. In situ experiments proved rutile formation occurs at the exposure temperature rather than during cooling and shows coloration changes in the surface throughout the reaction. Blisters also appeared in between the outermost rutile scales and developed at temperature rather than from CTE mismatch between the oxide and metal during cooling. This dissertation has contributed to the understanding of titanium reactions with nitrogen and oxygen at high temperatures and low partial pressures. The experimental approaches used can be applied towards studying further complex systems either in Ti-based alloys or in other systems such as complex concentrated alloys (CCAs)

Characterization of Printed Skin Equivalents

Severe burns, ulcerations, and cuts are some of the reasons people need bioengineered skin as a treatment for full-thickness wounds. When patients run out of donor sites in their own body, using the patient’s skin as a graft is no longer an option, and tissue-engineered constructs are the only possible replacement for damaged skin. The goal of this research is to develop a hydrogel-based skin graft that will be able to function as a skin replacement in full-thickness wounds while minimizing the possibility of rejection, being cost-effective, and possessing a longer shelf-life than the grafts currently in the market. Endothelial cells, keratinocytes and fibroblast cells are isolated from rat dermis and purified using magnetic bead separation. Using these cultured cells, two biological inks are prepared to create the gel that will be printed out to make the skin equivalent. The inks contain additional nutrients such as glucose, amino acids, serum free media, biopolymers, and proteins. Printing with the biological ink made of collagen and fibrin gel, we have developed a hydrogel where we can disperse cells with the purpose of obtaining a biodegradable wound dressing material with tunable properties. The printed skin is being tested on mice so the material can be analyzed to see if the material is working, and if not, to make the changes for it to be able to aid in the regeneration of skin