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Preventing Solidification Defects In Large Superalloy Castings Used In Advanced Electric Power Systems, Jairo Antonio Valdes Ortiz
Preventing Solidification Defects In Large Superalloy Castings Used In Advanced Electric Power Systems, Jairo Antonio Valdes Ortiz
Graduate Theses, Dissertations, and Problem Reports
The need for clean and affordable power has resulted in great demand for high-efficiency gas turbine power systems. To improve energy generation efficiency, and lower CO2 emissions, the new generation of land based gas turbines needs to be larger and operated at a higher temperature. Consequently, it is required the use of Nb-containing superalloys such as Inconel 718 for the rotor disk, to avoid overaging of the microstructure during the forging process, but its applicability is being limited by difficulties in the reliable production of large Vacuum Arc Remelting (VAR) ingots (33 to ∼35 in. diameter) without macrosegregation defects such …
Critical Buckling Strength Prediction Of Pultruded Gfrp Composite Columns, Mathew Marvin Blandford
Critical Buckling Strength Prediction Of Pultruded Gfrp Composite Columns, Mathew Marvin Blandford
Graduate Theses, Dissertations, and Problem Reports
Fiber-reinforced polymeric (FRP) composites offer a unique addition to common construction materials utilized in Civil Engineering. However, unlike traditional construction materials (steel, timber, concrete, etc) FRP composites lack adequate design standards and or criteria. The need for appropriate design guidelines is subsequently required in order to ease the progression of the use FRP composites in construction. The present research investigates several previously proposed prediction models' ability to calculate failure of GFRP composite columns of varied length and cross section. Material properties were developed through testing specimens of the coupon and 1ft "pure" compression (component) levels. Furthermore, a strain-energy density failure …
Leaching Of Chalcopyrite With Sodium Hypochlorite, Ravinder Kumar Garlapalli
Leaching Of Chalcopyrite With Sodium Hypochlorite, Ravinder Kumar Garlapalli
Graduate Theses, Dissertations, and Problem Reports
Chalcopyrite is the most important copper mineral source and also a refractory mineral for leaching. Several processing routes have been proposed to overcome the environmental problems related to copper extraction from chalcopyrite. In this study, the leaching of chalcopyrite has been investigated with a new reagent sodium hypochlorite (NaOCl). Experiments were carried out in two stages: conversion of chalcopyrite to cupric oxide with NaOCl solution in the first stage, followed by dissolution of the cupric oxide to cupric ion with 1 normal sulfuric acid at room temperature in the second stage. In the first stage leaching, the initial pH varied …
Fatigue Of Polymer Composites: Life Prediction And Environmental Effects, David Brian Dittenber
Fatigue Of Polymer Composites: Life Prediction And Environmental Effects, David Brian Dittenber
Graduate Theses, Dissertations, and Problem Reports
Fiber reinforced polymer composites offer significant advantages over traditional structural materials, but also many challenges, particularly with regard to their long term behavior. The fatigue performance of composites has been explored for the last few decades but it is still difficult to predict the behavior of a particular material under different loading and environmental conditions. Many researchers have worked to develop fatigue life prediction models and others to characterize the effect of environmental changes on static composite material properties, but experimental work in both of these areas can be difficult to perform and thus many observations have not been fully …
Paramagnetic Resonance Studies Of Defects In Titanium Dioxide Crystals, Shan Yang
Paramagnetic Resonance Studies Of Defects In Titanium Dioxide Crystals, Shan Yang
Graduate Theses, Dissertations, and Problem Reports
Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to identify and characterize point defects in TiO2 crystals having the rutile structure. Defect production occurs at low temperature during illumination with 442 nm laser light. Spectra with S = 1/2 and S = 1 are assigned to singly ionized and neutral oxygen vacancies, respectively. These oxygen vacancies have their unpaired spins localized on the two neighboring titanium ions aligned along the [001] axis. A Ti3+ ion next to a substitutional Si4+ ion, a Ti3+ self-trapped electron, and a self-trapped hole on the oxygen sublattice are also observed.;Fluorine ions …
Sulfur Tolerant Solid Oxide Fuel Cell For Coal Syngas Application: Experimental Study On Diverse Impurity Effects And Fundamental Modeling Of Electrode Kinetics, Mingyang Gong
Graduate Theses, Dissertations, and Problem Reports
With demand over green energy economy, fuel cells have been developed as a promising energy conversion technology with higher efficiency and less emission. Solid oxide fuel cells (SOFC) can utilize various fuels in addition to hydrogen including coal derived sygas, and thus are favored for future power generation due to dependence on coal in electrical industry. However impurities such as sulfur and phosphorous present in coal syngas in parts per million (p.p.m.) levels can severely poison SOFC anode typically made of Ni/yttria-stabilized-zirconia (Ni-YSZ) and limit SOFC applicability in economically derivable fuels. The focus of the research is to develop strategy …