Engineering Science and Materials Commons^™

Towards An Understanding Of The Thermodynamic Properties Of Crtao4: A Computational Perspective, Tanner B. Gordon

Theses and Dissertations

Materials that can withstand higher temperatures are paramount for next-generation aircraft design. Hypersonic capabilities and jet-turbine engines operate in extreme environments. Choosing materials that have high thermal stability and oxidation resistance for these applications can increase engine efficiency, reduce size, weight and power (SWaP), and increase the maneuverability of the aircraft. The mixed oxide CrTaO₄ has been experimentally observed to significantly contribute to oxidation resistance at high temperatures. However, and despite its significance, its properties remain largely unknown. This work explores the thermal properties of this material from a multi-scale approach, by obtaining an accurate description of the thermodynamics …

Dry Reforming Of Methane Using Microwave Irradiated Metal Oxide/Coal Char Catalysts, Anthony Carter

Graduate Theses, Dissertations, and Problem Reports

This research focuses on the synthesis of both shaped and amorphous powder materials, the combination of these materials with dried Powder River Basin (PRB) coal char, and their reactionary properties with methane and carbon dioxide gasses with conventional and microwave (MW) heating. The first goal of this project was to synthesize shaped micro and nano sized particles with ideal dielectric properties for converting electromagnetic energy into heat and proven capabilities of activating methane. These particles were synthesized via solvothermal, hydrothermal, and co-preceptory treatments alone and onto the surface of dried PRB coal char. PRB is a sub-bituminous, low-ranking coal (LRC) …

Effect Of Steam Environment On Creep Behavior Of Nextel720/Alumina-Mullite Ceramic Matrix Composite At Elevated Temperature, Tolga Kutsal

Theses and Dissertations

The tensile creep behavior of an oxide-oxide ceramic matrix composite (CMC) was investigated at 1000 and 1100° C in laboratory air and steam. The oxide-oxide CMC studied in this research was Nextel™ 720/alumina-mullite (N720/AM). The composite consists of N720/fibers with 0°/90° fiber orientation and a porous alumina-mullite matrix. Tensile-strain behavior was investigated and tensile properties measured at 900, 1000 and 1100° C. The effect of loading rate on tensile properties of N720/AM ceramic matrix composite at 1100° C in steam was also examined. Creep-rupture tests were performed at 1100° C in laboratory air and steam, and at 1000° C only …

High Temperature Oxidation Behavior Of Nb-20mo-15si-5b-20cr Alloy, Julieta Angelica Ventura

Open Access Theses & Dissertations

Materials for high temperature applications, such as jet engines, gas turbines and turbine blades, require a balanced combination of physical and chemical properties to withstand the aggressive environments in which they are utilized. Some of the properties required are high strength, low density, high melting point and good oxidation resistance at elevated temperatures [1-3]. For this reason, the microstructure and oxidation behavior of the Nb-20Mo-15Si-5B-20Cr alloy (at.%) has been studied as a potential candidate to replace Nickel-based alloys currently used in the aerospace industry.

Short term oxidation (STO) and long term oxidation (LTO) studies have been performed in air for …

Effects Of Environment On Creep Behavior Of Two Oxide-Oxide Ceramic Matrix Composites At 1200°C, Pavlos Koutsoukos

Theses and Dissertations

Previous studies by the advisor and graduate students examined creep behavior of the Nextel720/Alumina CMC in air and in 100% steam environments at 1200 and 1330°C. Results showed that while this oxide/oxide system exhibits an exceptionally high fatigue limit at 1200°C it also experiences substantial strain accumulation under sustained loading conditions. Furthermore, these earlier investigations revealed a significant degrading effect of 100% steam environment on material performance under both static and cyclic loadings. The present effort will investigate creep rupture behavior of Nextel720/Alumina composite in the inert gas environment. In addition, creep rupture behavior of Nextel720/Aluminosilicate CMC will be investigated …

Effect Of Environment On Creep Behavior Of An Oxide/Oxide Cfcc With ±45° Fiber Orientation, Gregory T. Siegert

Theses and Dissertations

Aerospace applications require materials capable of maintaining superior mechanical properties while operating at high temperatures and oxidizing environments. Nextel™ 720/A (N720/A), an oxide/oxide ceramic matrix composite (CMC) with a porous alumina matrix was developed specifically to provide improved long-term properties and performance at 1200°C. This research evaluated the creep behavior of N720/A with a ±45° fiber orientation at 1200°C in: laboratory air, steam, and argon environments. Creep-rupture tests at the creep stress levels of: 45, 40, 35, and 15 MPa were conducted in each environment.
The ultimate tensile strength of N720/A with ±45° fiber orientation was 55 MPa, the elastic …