Engineering Commons^™

3d Printing Of Lunar Regolith Based Ceramics Via The Dlp Method, Ricardo Vasquez

2022 MME Undergraduate Research Symposium

Ceramic parts generally have poor machinability due to their high hardness and high brittleness. Researchers and industries have overcome the difficulty of machining ceramics and have manufactured parts with intricate geometry by using pre-ceramic polymers in stereolithography (SLA) 3D printing and using slurries based on ceramic powder and photopolymer resin in digital light processing (DLP) 3D printing, among other methods. This presentation will discuss the processes involved in the 3D printing of ceramic and ceramic composite parts via the DLP technique. A vital step in ceramic 3D printing is to optimize the printing parameters for a specific slurry formulation in …

Fracture Strength Of Multi-Component Ultra-High Temperature Carbides, Gia Garino

2022 MME Undergraduate Research Symposium

Ultra-high temperature ceramics (UHTCs) have emerged as a promising material for next generation re-entry hypersonic vehicles due to high melting point (>3000 °C), and high mechanical properties and oxidation resistance. Yet none of the unary UHTCs can satisfy the whole gamut of demanding requirements for aerospace applications. Recently, the single-phase solid-solution formation in a multi-component ultra-high temperature ceramic (MC-UHTC) materials have gained interest due to their superior thermo-mechanical properties compared to conventional UHTCs. Herein, a systematic approach was used to fabricate binary (Ta, Nb)C, ternary (Ta, Nb, Hf)C, and quaternary (Ta, Nb, Hf, Ti)C UHTCs by gradual addition of …

Nanoelectronic Applications Of Magnetoelectric Nanostructures, Ping Wang

FIU Electronic Theses and Dissertations

The greatly increased interest in magnetoelectric materials over the last decade is due to their potential to enable next-generation multifunctional nanostructures required for revolutionizing applications spanning from energy-efficient information processing to medicine. Magnetoelectric nanomaterials offer a unique way to use a voltage to control the electron spin and, reciprocally, to use remotely controlled magnetic fields to access local intrinsic electric fields. The magnetoelectric coefficient is the most critical indicator for the magnetoelectric coupling in these nanostructures. To realize the immense potential of these materials, it is necessary to maximize the coefficient. Therefore, the goal of this PhD thesis study was …

Spark Plasma Sintering Of 2d Nitride And Carbide Based Ceramics, Archana Loganathan

FIU Electronic Theses and Dissertations

Two-dimensional (2D) nanomaterials have stimulated significant interest among materials community due to a wide variety of application ranging from functional to structural properties. Boron nitride nanosheets (BNNS), boron-carbon-nitride (BCN), and MXene (M_n+1X_n, transition metal carbides, nitrides or carbonitrides) belongs to 2D materials family with van der Waals bonding between the layers. The research on synthesis and properties of BNNS, BCN and MXene have been predominantly explored for single- or multi-layered 2D nanosheets. In this study, the focus is to synthesize bulk layered BNNS and BCN using single or multilayered 2D nanomaterials by spark plasma sintering (SPS). …

Electrochemical Behaviors Of The Electrodes For Proton Conducting Intermediate Temperature Solid Oxide Fuel Cells (It-Sofc), Shichen Sun

FIU Electronic Theses and Dissertations

Proton conducting intermediate temperature (600oC-400oC) solid oxide fuel cells (IT-SOFC) have many potential advantages for clean and efficient power generation from readily available hydrocarbon fuels. However, it still has many unsolved problems, especially on the anode where the fuel got oxidized and the cathode where oxygen got reduced. In this study, for the anode, the effects of hydrogen sulfite (H2S) and carbon dioxide (CO2) as fuel contaminants were studied on the nickel (Ni) based cermet anode of proton conducting IT-SOFC using proton conducting electrolyte of BaZr0.1Ce0.7Y0.1Yb0.1O3 (BZCYYb). Both low-ppm level H2S and low-percentage level CO2 caused similar poisoning effects on …

Synthesis & Fundamental Formation Mechanism Study Of High Temperature & Ultrahigh Temperature Ceramics, Paniz Foroughi

FIU Electronic Theses and Dissertations

Borides and carbides of tantalum and hafnium are of great interest due to their ultrahigh temperature applications. Properties of these ceramics including oxidation resistance and mechanical properties might be further improved through solid solution/composite formation. Synthesis of single-phase Ta_xHf_1-xC and Ta_xHf_1-xB₂ solid solution powders including nanopowders via carbothermal reduction (CTR) is complicated due to noticeable difference in reactivity of parent oxides with carbon, and also the low solubility of those oxides in each other. Moreover, for TaC-HfC system the solid solution may go through phase separation due to the presence of …

Synthesis, Processing, And Fundamental Phase Formation Study Of Czts Films For Solar Cell Applications, Osama Awadallah

FIU Electronic Theses and Dissertations

Copper zinc tin sulfide (Cu₂ZnSnS₄ or CZTS) kesterite compound has attracted much attention in the last years as a new abundant, low cost, and environmentally benign material with desirable optoelectronic properties for Photovoltaic (PV) thin film solar cell applications. Among various synthesis routes for CZTS thin films, sol-gel processing is one of the most attractive routes to obtain CZTS films with superior quality and low cost.

In this study, sol-gel sulfurization process parameters for CZTS thin films were systematically investigated to identify the proper process window. In addition, temperature dependent Raman spectroscopy was employed to monitor the …

Thermodynamic Investigation Of La0.8sr0.2mno3±Δ Cathode, Including The Prediction Of Defect Chemistry, Electrical Conductivity And Thermo-Mechanical Properties, Shadi Darvish

FIU Electronic Theses and Dissertations

Fundamental thermodynamic investigations have been carried out regarding the phase equilibria of La_0.8Sr_0.2MnO_3±δ (LSM), a cathode of a solid oxide fuel cell (SOFC), utilizing the CALculation of PHAse Diagram (CALPHAD) approach. The assessed thermodynamic databases developed for LSM perovskite in contact with YSZ fluorite and the other species have been discussed. The application of computational thermodynamics to the cathode is comprehensively explained in detail, including the defect chemistry analysis as well as the quantitative Brouwer diagrams, electronic conductivity, cathode/electrolyte interface stability, thermomechanical properties of the cathode and the impact of gas impurities, such as CO …

Thermodynamic Investigation Of Yttria-Stabilized Zirconia (Ysz) System, Mohammad Asadikiya

FIU Electronic Theses and Dissertations

The yttria-stabilized zirconia (YSZ) system has been extensively studied because of its critical applications, like solid oxide fuel cells (SOFCs), oxygen sensors, and jet engines. However, there are still important questions that need to be answered and significant thermodynamic information that needs to be provided for this system. There is no predictive tool for the ionic conductivity of the cubic-YSZ (c-YSZ), as an electrolyte in SOFCs. In addition, no quantitative diagram is available regarding the oxygen ion mobility in c-YSZ, which is highly effective on its ionic conductivity. Moreover, there is no applicable phase stability diagram for the nano-YSZ, which …

Hybrid Polymer Electrolyte For Lithium-Oxygen Battery Application, Amir Chamaani

FIU Electronic Theses and Dissertations

The transition from fossil fuels to renewable resources has created more demand for energy storage devices. Lithium-oxygen (Li-O₂) batteries have attracted much attention due to their high theoretical energy densities. They, however, are still in their infancy and several fundamental challenges remain to be addressed. Advanced analytical techniques have revealed that all components of a Li-O₂ battery undergo undesirable degradation during discharge/charge cycling, contributing to reduced cyclability. Despite many attempts to minimize the anode and cathode degradation, the electrolyte remains as the leading cause for rapid capacity fading and poor cyclability in Li-O₂ batteries. In this …

High Temperature Oxidation Study Of Tantalum Carbide-Hafnium Carbide Solid Solutions Synthesized By Spark Plasma Sintering, Cheng Zhang

FIU Electronic Theses and Dissertations

Tantalum carbide (TaC) and hafnium carbide (HfC) possess extremely high melting points, around 3900 ^oC, which are the highest among the known materials. TaC and HfC exhibit superior oxidation resistance under oxygen deficient and rich environments, respectively. A versatile material can be expected by forming solid solutions of TaC and HfC. However, the synthesis of fully dense solid solution carbide is a challenge due to their intrinsic covalent bonding which makes sintering challenging.

The aim of the present work is to synthesize full dense TaC-HfC solid solutions by spark plasma sintering with five compositions: pure HfC, HfC-20 vol.% TaC …

Microstructure And Mechanical Properties Of Nanofiller Reinforced Tantalum-Niobium Carbide Formed By Spark Plasma Sintering, Christopher Charles Rudolf

FIU Electronic Theses and Dissertations

Ultra high temperature ceramics (UHTC) are candidate materials for high temperature applications such as leading edges for hypersonic flight vehicles, thermal protection systems for spacecraft, and rocket nozzle throat inserts due to their extremely high melting points. Tantalum and Niobium Carbide (TaC and NbC), with melting points of 3950°C and 3600°C, respectively, have high resistivity to chemical attack, making them ideal candidates for the harsh environments UHTCs are to be used in. The major setbacks to the implementation of UHTC materials for these applications are the difficulty in consolidating to full density as well as their low fracture toughness. In …

Cobalt Ferrite Nanoparticles Fabricated Via Co-Precipitation In Air: Overview Of Size Control And Magnetic Properties, Dennis Toledo

FIU Electronic Theses and Dissertations

Cobalt Ferrite has important, size-dependent magnetic properties. Consequently, an overview of particle size is important. Co-precipitation in air was the fabrication method used because it is comparatively simple and safe. The effects of three different reaction times including 1, 2, 3 hour(s) on particle size were compared. Also, the effectiveness of three different capping agents (Oleic Acid, Polyvinylpyrollidone (PVP), and Trisodium Citrate) in reducing aggregation and correspondingly particle size were examined. Using Welch’s analysis of variance (ANOVA) and the relevant post hoc tests, there was no significant difference (p=0.05) between reaction times of 1 hour and 2 hours, but there …