Engineering Commons^™

High-Pressure Studies On The Transition From Red Phosphorus To Black Phosphorus, Heng Xiang

Electronic Thesis and Dissertation Repository

Black phosphorus (BP) is a promising material in many research fields. However, the transition process from amorphous red phosphorus (ARP) is elusive and hence hinders large scale synthesis and applications. This work describes the application of the high-pressure method to study the transition process from ARP to BP.

In this thesis, the following three objectives were achieved: (1) to understand the mechanism of the transition, (2) to facilitate the synthesis of BP by taking the advantage of less pure ARP, (3) to propose new methods of synthesizing BP-based materials, such as the moderately oxidized BP and the black phosphorus/ amorphous …

Characterization And Computational Modelling For The Garnet Oxide Solid State Electrolyte Ta-Llzo, Colin A. Versnick

Electronic Thesis and Dissertation Repository

The all-solid-state-battery (ASSB) serves as a promising candidate for next generation lithium ion batteries for significant improvements in battery safety, capacity, and longevity. Of the material candidates researched to replace the conventionally used liquid electrolyte, the garnet oxide Ta-LLZO (Li_6.4La₃Zr_1.4Ta_0.6O₁₂) has received much attention thanks to its high chemical and electrochemical stability, and ionic conductivity which rivals that of liquid electrolytes. While much investigation has taken place regarding the electrochemical performance of Ta-LLZO, much less is known about the micromechanics, including microstructural characterization, stress and strain development, and material failure …

Micromechanics Of Plasticity Of Zr-2.5%Nb Alloy, Md Imran Khan

Electronic Thesis and Dissertation Repository

Zirconium alloys are used in many thermal neutron fission reactors because of their very low neutron interaction cross-sections along with their excellent mechanical strength and corrosion resistance. Numerous experiments have been conducted on these alloys at the bulk scale to determine their mechanical properties. Recent advancements in micro-mechanical testing make it easier to study site-specific mechanical properties for micron or submicron-sized samples. Understanding the mechanical response of such small volumes of material is extremely important for developing accurate models to predict the ductile fracture toughness of these in-reactor materials. Pressure tubes made of Zr-2.5%Nb alloys are an integral part of …

Synthesis Of Vo2/Poly(Mma-Co-Dmemuabr) Antimicrobial/Thermochromic Dual-Functional Coating And Reactivity Ratios Study, Yixian Liu

Electronic Thesis and Dissertation Repository

Antimicrobial/thermochromic dual-functional coatings were successfully synthesized via UV-curing. The quaternary ammonium compound (QAC) N,N-dimethyl-N-{2-[(2-methylprop-2-enoyl)oxy]ethyl}undecane-1-aminium bromide (dMEMUABr) was synthesized and copolymerized with methyl methacrylate (MMA) for antimicrobial properties. Vanadium oxide (VO₂) nanoparticles were evenly dispersed within the coating, providing thermochromic properties. The dual-functional coating showed high luminous transmittance (T_lum(25°C) =36.1 %) and solar energy modulation ( T_sol=5.8 %). 90.3 % of bacteria reduction was observed against Escherichia coli within 24 h contact. To further understand the sequence distribution of the copolymer poly(MMA-co-dMEMUABr), the reactivity ratios of MMA and dMEMUABr monomer were studied and compared under thermal …

Development Of Novel Solid-State Electrolytes For Sodium Ion Batteries, Fei Sun

Electronic Thesis and Dissertation Repository

Sodium ion battery is considered as a potential candidate to replace lithium ion battery. To eliminate the need for containment of the liquid electrolyte, the solid-state electrolytes attract more attention. However, solid state electrolytes are still restricted to be applied for commercialization because of the inherent low ionic conductivity and the poor mechanical properties. Therefore, my Ph.D. research is focused on developing advanced solid-state electrolytes by improving ionic conductivity and disclosing mechanisms of the electrolytes.

Firstly, a series of La substituted NASICON electrolytes are prepared to achieve high ionic conductivity of mS/cm, and the effects of La substitution concentration are …

Effect Of Ion Implantation On The Mechanical Properties Of The Grain And Grain Boundary Regions Of Inconel X750, Maisaa Nezar Tawfeeq

Electronic Thesis and Dissertation Repository

Annulus gas spacers in CANada Deuterium Uranium (CANDU) nuclear reactors are made from the heat-treated Inconel X750 Nickel-based alloy. This alloy is designed to have high strength and creep resistance at elevated temperature. Unlike other reactor designs, the CANDU reactor has a high thermal neutron fluence, which results in an enhancement of the radiation damage and the internal production of helium and hydrogen. They are thus susceptible to microstructural instability and mechanical property degradation with time. Studies of ex-service spacers have indicated that they display intergranular embrittlement and lower ultimate tensile strength compared to nonirradiated Inconel X750. The primary degradation …

Novel Avenues Toward Controlling The Photophysical Properties Of Ultra-Small Silicon Quantum Dots, Mohammed Abdelhameed

Electronic Thesis and Dissertation Repository

Quantum dots (QDs) have attracted an increasing attention in the last decade over many conventional organic dyes. This is due to their unique optical properties including broad absorption spectra, high photostability, and size-tunable photoluminescence (PL). However, some toxicity concerns associated with traditional quantum dots have hindered their wide applicability. Interestingly, silicon quantum dots (SQDs) have been shown to be more advantageous than most of QDs thanks to their excellent biocompatibility and biodegradability, low cytotoxicity, and versatile surface functionalization capability. Thus, SQDs are promising candidates for various biological and biomedical applications such as bioimaging, biosensing, and photodynamic therapy. Unfortunately, only a …

Design Of Cell-Instructive Biomaterial Scaffolds For Intervertebral Disc Regeneration, Nadia Sharma

Electronic Thesis and Dissertation Repository

Biomaterials-based therapies targeting the nucleus pulposus (NP) have the potential to promote regeneration and restore mechanical function to the intervertebral disc. This study developed composite hydrogels incorporating decellularized NP (DNP) and assessed its effects on viability, retention and differentiation of U-CH1 cells, an NP progenitor-like cell line. A minimal protocol was developed to decellularize bovine NP that reduced nuclear content while preserving key extracellular matrix components predicted to be favourable for bioactivity. The resulting DNP demonstrated cell-instructive effects, supporting U-CH1 viability and retention within the hydrogels, and promoted the differentiation of the progenitor-like cells towards an NP-like phenotype. These studies …

Shape-Controlled Nanoparticles As Effective Catalysts For Proton Exchange Membrane (Pem) Fuel Cells, Ali Feizabadi

Electronic Thesis and Dissertation Repository

Polymer electrolyte membrane fuel cell (PEMFC), is considered a promising candidate for the next generation power sources in transportation, stationary and portable applications. However, oxygen reduction reaction (ORR), one of the key reactions occurring on PEMFC is kinetically slow; this has limited performance and further advancement in this kind of fuel cells. Thus, improving the PEMFC efficiency requires a thorough understanding of the ORR mechanism on the desired catalyst. To address the above-mentioned demands, the scope of this thesis is focused on the fundamental understanding of facet-controlled nanoparticles, metal-support interactions, and bimetallic platinum catalysts, utilizing synchrotron-based X-ray absorption, X-ray photoelectron …

Development Of Cellulose Nanofiber Reinforced Poly(Methyl Methacrylate), Tyler Bennett

Electronic Thesis and Dissertation Repository

Cellulose nanofiber (CNF), derived from renewable resources, is a good candidate to reinforce transparent plastics without sacrificing their transparency, owing to its size on the nano-meter scale, reflective index similar to the plastics’, excellent mechanical property, and low density. This study investigates effects of CNF on optical, viscoelastic, and thermal properties of CNF reinforced poly(methyl methacrylate) (PMMA). CNF/PMMA with different CNF contents and different types of PMMA were prepared through a solvent casting method with a low toxic and inexpensive solvent, acetone, and compression-molded to create nanocomposite films. The films were characterized using a transmission electron microscope, ultraviolet–visible (UV-Vis) spectrophotometry, …

Molecular Weight And Thermal Properties Of Fiber Reinforced Polyamide-Based Composites Throughout The Direct Long-Fiber Reinforced Thermoplastic Process, Mingyu Yang

Electronic Thesis and Dissertation Repository

The D-LFT process is an efficient and cost-effective process and includes two twin-screwextruders, a conveyer, and a compression molding machine. It is imperative to understand how the process sequence affects molecular weight and thermal properties of composite materials during the D-LFT process. The main objective of this study was to characterize variation in molecular weight and thermal properties of two types of polyamide (PA)-based composite materials (glass fiber reinforced PA6 composites and carbon fiber reinforced PA66 composites) through the D-LFT process. Samples were taken from different locations along the D-LFT process and characterized using triple detection gel permeation chromatography (GPC), …

Enhanced Carbon Fiber-Epoxy Composites For Rowing Racing Shells, Rayehe Samimi

Electronic Thesis and Dissertation Repository

This thesis investigates the thermomechanical properties of two commercial composites using carbon fiber reinforcement in epoxy resins for manufacturing marine based rowing racing shells. The main goal of this project was to investigate how to control the resin properties and curing temperatures to improve the final product properties including adhesion, toughness modulus and tensile strength. Moreover, an efficient curing process was required by our supporting company to be used at low temperatures to enhance the curing characteristics and to provide improved mechanical properties. Accordingly, the current research tries to improve the manufacturing curing process and build up high performance structure …

Effect Of The Nonlinear Material Viscosity On The Performance Of Dielectric Elastomer Transducers, Yuanping Li

Electronic Thesis and Dissertation Repository

As a typical type of soft electroactive materials, dielectric elastomers (DEs) are capable of producing large voltage-induced deformation, which makes them desirable materials for a variety of applications in transduction technology, including tunable oscillators, resonators, biomimetics and energy harvesters. The dynamic and energy harvesting performance of such DE-based devices is strongly affected not only by multiple failure modes such as electrical breakdown, electromechanical instability, loss-of-tension and fatigue, but also by their material viscoelasticity. Moreover, as suggested by experiments and theoretical studies, DEs possess nonlinear relaxation processes, which makes modeling of the performance of DE-based devices more challenging.

In this thesis, …

Fabrication And Characterization Of Collagen-Polypyrrole Constructs Using Direct-Ink Write Additive Manufacturing, Rooshan Arshad

Electronic Thesis and Dissertation Repository

Current efforts in the tissue engineering field are being directed towards the creation of platforms which will facilitate in instructing cells towards biologically relevant outcomes such as stem cell differentiation and disease pathophysiology. Traditional fabrication methods serve as a limiting factor for the production of such platforms as they lack feature and geometric complexity. Additive Manufacturing (AM) offers advantage over said methods by affording designers creative freedom and great control over printed constructs. Such constructs can then be used to create appropriate models for study- ing a plethora of tissues and structures. An AM methodology for Direct-Ink Write (DIW) printing …

Additive Manufacturing Of Piezoelectric Photopolymer Ferroelectrets, Rami Abu Shammeh

Electronic Thesis and Dissertation Repository

Electroactive polymers are an emerging branch of smart materials that possess the capability to change shape in the presence of an electric field. Particularly, ferroelectrets are films of electrostatically charged dielectric polymer foam that comprise a growing portion of EAP literature. Ferroelectrets are characterized by a piezoelectric response and a quasi-permanent charge polarization owing to the dipoles created when the air cavities in the polymer matrix undergo dielectric breakdown. However, these cavities are often irregular in shape, size, and distribution when produced with conventional preparation methods. To overcome this, we employ a light-based additive manufacturing technique to create a hybrid …