We are facing an energy crisis because of the limitation of the fossil fuel and the pollution caused by burning it. Clean energy technologies, such as fuel cells and metal-air batteries, are studied extensively because of this high efficiency and less pollution. Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential in the process of energy storage and conversion, and noble metals (e.g. Pt) are needed to catalyze the critical chemical reactions in these devices. Functionalized carbon nanomaterials such as heteroatom-doped and molecule-adsorbed graphene can be used as metal-free catalysts to replace the expensive and scarce platinum-based catalysts for the energy storage and conversion. Traditionally, experimental studies on the catalytic performance of carbon nanomaterials have been conducted extensively, however, there is a lack of computational studies to guide the experiments for rapid search for the best catalysts. In addition, theoretical mechanism and the rational design principle towards ORR and OER also need to be fully understood. In this dissertation, density functional theory calculations are performed to calculate the thermodynamic and electrochemical properties of heteroatom-doped graphene and molecule-adsorbed graphene for ORR and OER. Gibb's free energy, overpotential, charge transfer and edge effect are evaluated. The charge transfer analysis show …

The penchant towards development of high performance materials for light weighting engineering systems through various thermomechanical processing routes has been soaring vigorously. Friction stir processing (FSP) - a relatively new thermomechanical processing route had shown an excellent promise towards microstructural modification in many Al and Mg alloy systems. Nevertheless, the expansion of this process to high temperature materials like titanium alloys and steels is restricted by the limited availability of tool materials. Despite it challenges, the current thesis sets a tone for the usage of FSP to tailor the mechanical properties in titanium alloys and steels. FSP was carried out on three near beta titanium alloys, namely Ti6246, Ti185 and Tiβc with increasing β stability index, using various tool rotation rates and at a constant tool traverse speed. Microstructure and mechanical property relationship was studied using experimental techniques such as SEM, TEM, mini tensile testing and synchrotron x-ray diffraction. Two step aging on Ti6246 had resulted in an UTS of 2.2GPa and a specific strength around 500 MPa m3/mg, which is about 40% greater than any commercially available metallic material. Similarly, FSP on an ultra-high strength steel―Eglin steel had resulted in a strength greater than 2GPa with a ductility close …

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.

Daily newspaper from Denton, Texas that includes local, state, and national news along with advertising.