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Full-Text Articles in Engineering Science and Materials
Mechanically Activated Combustion Synthesis Of Molybdenum Borosilicides For Ultrahigh-Temperature Structural Applications, Alan Alberto Esparza Hernandez
Mechanically Activated Combustion Synthesis Of Molybdenum Borosilicides For Ultrahigh-Temperature Structural Applications, Alan Alberto Esparza Hernandez
Open Access Theses & Dissertations
The desire to improve the efficiency of power generation gas-turbines has led to a relentless quest for new, ultrahigh-temperature structural materials to replace the current nickel-based superalloys. These materials have reached the maximum allowable operating temperature determined by the melting temperature of these alloys, which is about 1150 °C. These materials could be replaced by molybdenum silicides and borosilicides based on Mo5SiB 2 (T2) phase due to their high melting point and mechanical properties. A major challenge, however, is to simultaneously achieve high oxidation resistance and acceptable mechanical properties at elevated temperatures. One novel approach to improve these properties is …
Yttria Rich Tbcs As Candidates For Cmas Resistant Top Coats, Juan Jose Gomez
Yttria Rich Tbcs As Candidates For Cmas Resistant Top Coats, Juan Jose Gomez
Open Access Theses & Dissertations
State of the art thermal barrier coatings (TBC) commonly made of 7-8 wt. % yttria stabilized zirconia (7YSZ) are used in modern gas turbines to generate a thermal protection to the underlying super alloy components. TBCs allow higher operating temperatures for hot gas path components, thus, generating higher engine efficiency. The infiltration of molten glassy mineral deposits composed of CaO-MgO-Al2O3-SiO2 (CMAS) represents one of the major threats in reducing performance and service life in aero and land based gas turbine engines. The CMAS deposits are ingested into the engine carried commonly in sand, runways debris, fly ash and volcanic ash. …
Damage Tolerance And Assessment Of Unidirectional Carbon Fiber Composites, Mark David Flores
Damage Tolerance And Assessment Of Unidirectional Carbon Fiber Composites, Mark David Flores
Open Access Theses & Dissertations
Composites are beginning to be used in a variety of different applications throughout industry. However, certification and damage tolerance is a growing concern in many aerospace and marine applications. Although compression-after-impact have been studied thoroughly, determining a damage tolerance methodology that accurately characterizes the failure of composites has not been established. An experimental investigation was performed to study the effect of stacking sequence, low-velocity impact response, and residual strength due to compression and fatigue. Digital Image Correlation (DIC) captured the strains and deformation of the plate due to compression. Computational investigations integrated non-destructive techniques (C-Scan, X-Ray) to determine the extent …
Structural, Dielectric, And Ferroelectric Characterization Of Lead-Free Calcium-Cerium Co-Doped Batio3 Ceramics, Juan Alberto Duran
Structural, Dielectric, And Ferroelectric Characterization Of Lead-Free Calcium-Cerium Co-Doped Batio3 Ceramics, Juan Alberto Duran
Open Access Theses & Dissertations
Structure, morphology, and regulation of the dielectric properties via close-composition intervals is demonstrated for variable-cerium, constant-calcium co-doped barium titanate (Ba0.80Ca0.20CeyTi1-yO3; y=0.0-0.25; referred to BCCT). The effect of variable Ce-content on the structure and dielectric properties of BCCT is investigated. X-ray diffraction spectra confirms the studied samples are mainly in BT tetragonal phase with a small secondary phase detected as CaTiO3 in BCCT for y = 0.20 and 0.25. However, the lattice parameter reduction was evident with increasing Ce-content. Composition-driven dielectric constant leap (4,000-5,500) was observed from intrinsic BCT to BCCT for (y = 0.0-0.04). The temperature dependent dielectric constant showed …