Description of the thesis topic

Investigation of the evolution of the pore network of preceramic polymer during their thermal conversion into non-oxide ceramics – Application to the development of CMC

Scientific context: To address the current and future energy, environmental, and economic challenges of air transport, significant efforts are being devoted to turbojet engines for future generations of aircraft. These efforts are expected to lead to more efficient, more environmentally friendly, and more economical engines for the decarbonization of air transport by 2050. However, such actions require replacing key materials—generally nickel-based superalloys—making up turbine blades with ceramic matrix composites (CMCs), which combine lightness, thermomechanical strength, and damage tolerance depending on the choice of the various constituents that compose them. Replacing superalloys with CMCs would eliminate the internal cooling currently required to use the former, reduce engine weight, and allow for increased temperatures for internal and external turbojet parts. Furthermore, these CMCs will increase the lifespan of engine parts to increase robustness and facilitate the maintainability of military and civil aircraft.

Description of the subject: This thesis project is based on a collaboration between the Institute for Research for Ceramics (IRCER-UMR 7315 CNRS- Univ. Limoges), the Laboratory of ThermoStructural Composites (LCTS, University of Bordeaux-UMR CNRS 5801) and a partner from the socio-economic world (Safran Ceramics, SCe). It focuses on the development of CMCs whose composition is based on the silicon-carbon-nitrogen (Si-C-N) system offering thermomechanical characteristics and a lifetime compatible with operation at 1450°C (≈2700F) for long periods for internal engine components. The main objective of this thesis project carried out at IRCER is to optimize the PIP (Polymer Impregnation Pyrolysis) process, which is coupled with the CVI (Chemical Vapor Deposition) process for the production of these CMCs. More specifically, it aims to elucidate the effects of a variety of characteristics inherent to the preceramic polymers used as precursors in the PIP process, as well as to the PIP-related process parameters, on the pore network developed during conversion into a ceramic matrix. This work should make it possible to generate ceramic matrices whose pore network is adapted to subsequent CVI infiltration, resulting in dense PIP-CVI matrices and, consequently, CMCs with the expected mechanical performance. This thesis project has a highly exploratory and innovative nature, which will be used to ensure successful communication, dissemination, and promotion of the project's results. It represents the key step in ultimately leading to the technological building blocks essential for the production of robust “2700 F” CMC components suitable for certification, in accordance with the energy, environmental and economic targets of the market.

Work Context

Located in the Nouvelle Aquitaine region, in Limoges, IRCER bridges the gap between tradition and modernity by innovating in the development of high-tech ceramics that meet novel industrial and societal challenges (energy, information and communication technology, health, eco-materials, etc.). IRCER brings together its staff (200 members) and equipment in a unique building spanning 8,500 m², called the "European Ceramics Center." The position is located in a sector covered by the protection of scientific and technical potential (PPST), and therefore, in accordance with regulations, requires that your arrival be authorized by the competent MESR authority.

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.