Oxidation Behavior of Carbon and Ultra-High Temperature Ceramics

• Main Author: Miller-Oana, Melia
• Other Authors: Corral, Erica L.
• Language: en_US
• Published: The University of Arizona. 2016
• Subjects: Materials Science & Engineering
• Online Access: http://hdl.handle.net/10150/605121; http://arizona.openrepository.com/arizona/handle/10150/605121

Hypersonic vehicles require material systems that can withstand the extreme environment they experience during flight. Carbon-based materials and ultra-high temperature ceramics are candidates for materials systems that will protect hypersonic vehicles. In order to study the material response, an oxyacetylene torch facility and thermal gravimetric analysis are used to investigate the gas-solid interactions under conditions that simulate aspects of flight. The oxyacetylene torch facility is characterized as a function of position from the tip for heat flux and oxygen content. By understanding the local heat flux and oxygen conditions, experiments are designed so that graphite ablation rates can be measured as a function of heat flux and partial pressure of oxygen. Further investigation shows that composition of the material influences the temperature response where ultra-high temperature ceramics exhibit the lowest surface temperatures. Using thermal gravimetric analysis, the isothermal oxidation behavior of ultra-high temperature ceramics from 1000-1600°C is investigated using a Dynamic Non- Equilibrium method in order to understand the reaction kinetics of ZrB₂-SiC where parabolic rate constants are determined. Isothermal oxidation behavior is compared to non-isothermal mass gain and oxide scale formation where specimens oxidized isothermally gain 3 times more mass and have oxide scales 4 times as thick. Finally, the effect of SiC content in ZrB₂ on temperature during oxyacetylene torch testing is determined. Increasing the amount of SiC results in lower front face temperatures because more heat is absorbed due to the endothermic reactions of evaporation of SiO₂.