Oxidation Behavior of Carbon and Ultra-High Temperature Ceramics Using Dynamic Non-Equilibrium Thermal Gravimetrics Analysis
Start Date
29-2-2012 1:55 PM
Description
Advanced thermal protection system (TPS) materials that can withstand extreme extreme aerothermal heating loads are needed for use in next generation aerospace vehicles. However, relevant test methods that simulate the flight environment limit our understanding of current and advanced TPS materials. Therefore, the focus of this talk will be to investigate the effect of high temperature gas mixture surface interactions with the oxidation rates of carbon and ultra-high temperature ceramic materials using high temperature thermal gravimetric analysis (TGA) testing methods. We have developed a testing method called, dynamic non-equilibrium (DNE) TGA that allows for us to measure oxidation rates for carbon materials from 600-1600 °C under different partial pressures of oxygen that allow for true isothermal rate data measurement. Our preliminary results for oxidation behavior of carbon-carbon composite and graphite show that with increasing partial pressure of oxygen the oxidation rates follow the same oxidation rate at 1600 °C. At lower partial pressures we observe a deviation from the oxidation rate which is due to the preferential attack of the carbon filler phase in the carbon-carbon composites rather than the fibers. Highly ordered pyrolytic graphite oxidizes preferentially at the edges of the bulk material and a systematic approach to understand bulk oxidation rates for graphite materials is being developed for future use in predictive oxidation rat models based on both oxidation rates and microstructural differences between carbon material forms. Furthermore, we will compare high temperature TGA-DNE and oxyacetylene torch oxidation behavior between carbon materials and ultra-high temperature ceramics which are ideal candidates for sharp leading edge materials that will have to withstand temperatures greater than 2000 °C.
Oxidation Behavior of Carbon and Ultra-High Temperature Ceramics Using Dynamic Non-Equilibrium Thermal Gravimetrics Analysis
Advanced thermal protection system (TPS) materials that can withstand extreme extreme aerothermal heating loads are needed for use in next generation aerospace vehicles. However, relevant test methods that simulate the flight environment limit our understanding of current and advanced TPS materials. Therefore, the focus of this talk will be to investigate the effect of high temperature gas mixture surface interactions with the oxidation rates of carbon and ultra-high temperature ceramic materials using high temperature thermal gravimetric analysis (TGA) testing methods. We have developed a testing method called, dynamic non-equilibrium (DNE) TGA that allows for us to measure oxidation rates for carbon materials from 600-1600 °C under different partial pressures of oxygen that allow for true isothermal rate data measurement. Our preliminary results for oxidation behavior of carbon-carbon composite and graphite show that with increasing partial pressure of oxygen the oxidation rates follow the same oxidation rate at 1600 °C. At lower partial pressures we observe a deviation from the oxidation rate which is due to the preferential attack of the carbon filler phase in the carbon-carbon composites rather than the fibers. Highly ordered pyrolytic graphite oxidizes preferentially at the edges of the bulk material and a systematic approach to understand bulk oxidation rates for graphite materials is being developed for future use in predictive oxidation rat models based on both oxidation rates and microstructural differences between carbon material forms. Furthermore, we will compare high temperature TGA-DNE and oxyacetylene torch oxidation behavior between carbon materials and ultra-high temperature ceramics which are ideal candidates for sharp leading edge materials that will have to withstand temperatures greater than 2000 °C.