Ceramic fiber composites with nitride-bonded silicon nitride matrix based on slurries

• Applicant: Professor Dr.-Ing. Stefan Schafföner
• Subject Area: Glass, Ceramics and Derived Composites
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 555162348

In contrast to monolithic ceramics, ceramic matrix composites exhibit a damage-tolerant fracture behavior. One possibility to achieve this fracture behavior is the weak matrix concept, which forgoes a time-consuming and cost-intensive fiber coating. Cracks occurring in a weak, i.e. porous matrix, are diverted, branched and deflected along the fiber/matrix interface. While this concept is widely used in the field of all-oxide ceramic matrix composites, it has only rarely been used for non-oxide ceramic matrix composites. Thus, the aim of this project is the development of a new type of non-oxide ceramic matrix composite for use in oxygen-free atmospheres up to 1600 °C, whose damage tolerance is achieved by the weak matrix concept. Pitch-based carbon fibers are used as reinforcing fibers, while the slurry-based matrix consists of nitride-bonded silicon nitride. The project includes a holistic view of the manufacturing process, spanning from the reactivity of the powders used in the slurry to the resulting green body density, the reactivity during nitriding, the fiber/matrix bonding and the influence of the fibers on nitriding up to the properties of the ceramic matrix composite. Additionally, this project will investigate the extent to which the mechanisms known from all-oxide ceramic matrix composites based on the weak matrix concept can be transferred to novel non-oxide ceramic matrix composite. Possible applications of the novel, corrosion-resistant ceramic matrix composite are crucibles for silicon crystal growth, for aluminum metallurgy, for phase change materials (e.g. Fe-Si-B melts), or for other high-performance applications such as in novel nuclear reactors.

• DFG Programme: Research Grants