In situ study of the oxidation of UHTC materials
| Autor: | Julian-Jankowiak, Aurélie, Guérineau, V., Justin, Jean-Francois, Vilmart, Gautier, Dorval, Nelly |
|---|---|
| Přispěvatelé: | DMAS, ONERA, Université Paris Saclay (COmUE) [Châtillon], ONERA-Université Paris Saclay (COmUE), DPHY, ONERA, Université Paris Saclay (COmUE) [Palaiseau], André, Cécile |
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: | |
| Zdroj: | IUPAC 2019 IUPAC 2019, Jul 2019, PARIS, France |
| Popis: | International audience; The Ultra-High Temperature Ceramics are a class of materials of growing interest. For applications like hypersonic flights, re-entry vehicles or propulsion, these materials are expected to sustain very high temperatures (>2000°C) in very corrosive and oxidizing atmospheres. Since more than a decade, Onera has carried out several activities on ZrB 2 and HfB 2-based UHTC materials from manufacturing to thermomechanical assessments and oxidation resistance understanding [1]. Oxidation behavior of this class of materials have been extensively studied demonstrating the formation of a multi-oxide scale composed of a MeO 2 skeleton and a glassy borosilicate layer at high temperatures [2, 3]. However, most of the studies dealing with UHTC oxidation are post-mortem studies, meaning that characterization of the sample is performed after the oxidation test. Thus, this study focuses on the development of a technique to study the real time oxidation behavior of the glassy layer formed on the surface of the materials. In this perspective, the Laser Induced Fluorescence (LIF) technique is used to probe BO 2 radicals in the gas phase above the heated sample in air atmosphere. ZrB 2-SiC and HfB 2-SiC-based UHTC materials were heated, with a 2 kW CO 2 laser, up to 1650°C in air flow at 1 bar, in a custom-made chamber equipped with fused silica windows for laser diagnostics. By monitoring the BO 2 fluorescence and the laser transmission signals throughout the heating ramp, insights on the thermal stability of the boria glassy phase (when SiC is not oxidized) and then of the borosilicate layer are given. These in situ diagnostics allow us to propose more precise oxidation mechanisms with temperature. Then, the results are compared to thermogravimetric analyses and finally, samples are characterized with SEM/EDS to confirm the oxidation mechanisms. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|