Engineering Commons^™

Controlled Synthesis Of One Dimensional Nanostructured Materials And Their Applications As Catalyst Supports In Proton Exchange Membrane Fuel Cells, Mohammad Norouzi Banis

Electronic Thesis and Dissertation Repository

Nanomaterials have attracted significant interest in the past decade due to their unique structure and properties compared to their bulk counterparts. Nanomaterials-based solutions can address challenges in various technologies such as proton exchange membrane fuel cells (PEMFCs). PEMFC is an innovative energy conversion technology to directly convert chemical energy to electrical energy by using hydrogen as fuel. However, the current PEMFC system still faces significant technological roadblocks which have to be overcome before the system can become economically viable. A major impediment to the commercialization of PEMFC is the high cost of materials and manufacturing and stability, which is primarily …

Calcium Phosphate-Based Resorbable Biomaterials For Bone Regeneration, Daniel O. Costa

Electronic Thesis and Dissertation Repository

Bone defects are a prevalent problem in orthopedics and dentistry. Calcium phosphate-based coatings and nanocomposites offer unique solutions towards producing scaffolds with suitable physical, mechanical and biological properties for bone regeneration.

We developed a novel method to synthesize hydroxyapatite (HA) particles with high aspect ratio using sol-gel chemistry and hydrothermal treatment. We obtained tunable pure-phase carbonated-HA in the form of micro/nanorods and nanowires (diameters 25-800 nm). To mimic the structure of bone, HA nanowires were homogenously mixed within poly(ε-caprolactone) (PCL) to produce nanocomposites with improved mechanical properties as determined by uniaxial tensile testing.

Surface chemistry and topography of biomaterials play …

Development Of A Novel Handheld Device For Active Compensation Of Physiological Tremor, Abhijit Saxena

Electronic Thesis and Dissertation Repository

In microsurgery, the human hand imposes certain limitations in accurately positioning the tip of a device such as scalpel. Any errors in the motion of the hand make microsurgical procedures difficult and involuntary motions such as hand tremors can make some procedures significantly difficult to perform. This is particularly true in the case of vitreoretinal microsurgery. The most familiar source of involuntary motion is physiological tremor. Real-time compensation of tremor is, therefore, necessary to assist surgeons to precisely position and manipulate the tool-tip to accurately perform a microsurgery. In this thesis, a novel handheld device (AID) is described for compensation …

Hydrogel-Based Nanocomposites And Laser-Assisted Surface Modification For Biomedical Application, Pei Yin

Electronic Thesis and Dissertation Repository

Hydrogels can be used in contact lens, wound dressing, drug delivery and tissue scaffolds due to their good biocompatibility. However, the poor mechanical properties and non-specific protein adsorption of hydrogels limit their applications. The adverse effects of protein adsorption in hydrogels include biofouling, inflammation, or even body rejection. In this project, two different hydrogel materials, co-polymer 2-hydroxyethyl methacrylate with a low amount of 2-aminoethyl methacrylate, p(HEMA-co-AEMA) and silicone hydrogel were fabricated by photo-polymerization; the former has hydrophilic surface and the latter is hydrophobic. The silica (SiO₂) nanoparticle-loaded hydrogels have been developed by using in situ polymerization. The dispersion …

Phase Field Crystal Approach To The Solidification Of Ferromagnetic Materials, Niloufar Faghihi

Electronic Thesis and Dissertation Repository

The dependence of the magnetic hardness on the microstructure of magnetic solids is investigated, using a field theoretical approach, called the Magnetic Phase Field Crystal model. We constructed the free energy by extending the Phase Field Crystal (PFC) formalism and including terms to incorporate the ferromagnetic phase transition and the anisotropic magneto-elastic effects, i.e., the magnetostriction effect. Using this model we performed both analytical calculations and numerical simulations to study the coupling between the magnetic and elastic properties in ferromagnetic solids. By analytically minimizing the free energy, we calculated the equilibrium phases of the system to be liquid, non-magnetic …

Solid-State Nuclear Magnetic Resonance Spectroscopy Of Unreceptive Quadrupolar Nuclei In Inorganic Materials, Andre Sutrisno

Electronic Thesis and Dissertation Repository

Preparation and characterization of inorganic materials is a crucial practice because understanding the relationship between structure and property is important for improving current performance and developing novel materials. Many metal centers in technologically and industrially important materials are unreceptive low-γ quadrupolar nuclei (i.e., possessing low natural abundance, low NMR frequencies and large quadrupole moments) and they usually give rise to very broad NMR resonances and low signal-to-noise ratios, making it difficult to acquire their solid-state NMR spectra. This thesis focuses on the characterization of inorganic materials using solid-state NMR (SSNMR) spectroscopy at very high magnetic field of …

Investigation Of The Use Of Micro-Mechanical Testing To Analyze The Mechanical Anisotropy Of The Zr-2.5%Nb Pressure Tube Alloy, Richard O. Oviasuyi

Electronic Thesis and Dissertation Repository

Maintaining a safe operation of nuclear power plants is the primary requirement of nuclear power generating organizations worldwide. This necessitates the use of highly effective methods for assessing the mechanical properties of reactor materials and components. This is important since all components located in a nuclear reactor core experience high levels of neutron irradiation which cause defects to be formed in the metals’ crystal structure. The density of these crystal defects increases with increasing exposure to neutrons and cause the crystalline metal to become harder and simultaneously more brittle. This change in mechanical properties is potentially detrimental to the safe …

Assessment Of The Kinetics Of Local Plastic Deformation Of Zr-2.5%Nb Candu Pressure Tube Material, Bipasha Bose

Electronic Thesis and Dissertation Repository

Constant-load pyramidal indentation creep tests and high precision micro-indentation strain rate change tests were performed to assess the effect of indentation depth, irradiation damage and temperature on the mechanical anisotropy and local plastic deformation parameters of the Zr-2.5%Nb CANDU pressure tube material. Polished samples aligned normal to the transverse (TN), axial (AN) and radial (RN) directions of the pressure tube were irradiated with 8.5 MeV Zr⁺ ions to simulate the effect of neutron irradiation. Constant-load pyramidal indentation creep tests performed at 25ºC show that the average indentation stress increases with decreasing indentation depth and increasing levels of irradiation. The …