Patent: Amorphous SiBNC Ceramics – A Material That Keeps Its Cool When Hot
A great deal of energy could be saved if turbines and combustion engines operated at higher temperatures than they currently do. Ceramic high-temperature materials make this possible. Martin Jansen, Director at the Max Planck Institute for Solid State Research in Stuttgart, has been conducting research into just such a new material for 20 years. It is now ready for the market: Amorphous SiBNC Ceramics for High-Temperature, High-Durability and Light-Weight Applications
Picture: Stable, even when it gets hot – The ceramic fibers made from silicon, boron, nitrogen and carbon can withstand extremely high temperatures.
Max-Planck-Innovation is seeking companies interested in commercializing a novel class of amourphous ceramics materials suited for applications requiring light weight and extraordinary mechanical and chemical stability at elevated temperatures over long periods of time:
Prof. Jansen and his group have developed extensive expertise about a novel class of amorphous ceramic materials made up of silicon, boron, nitrogen and carbon. The developed know-how comprises the entire production process from molecular precursor, to preceramic polymer and ceramic material. The process can be tailored to yield ceramic fibers, ceramic coatings and ceramic matrix composites.
This novel class of Si-B-N-C ceramics with its combination of mechanical and chemical stability and light weight paves the way towards a new generation of products based on the use of high-temperature ceramic materials that are superior to superalloys and other types of ceramics.
Picture: A path to a stable network: The molecular building blocks (left) initially form a strongly branched polymer (center) in one of the possible synthesis paths. When fired, a high-temperature ceramic is created (right). Silicon, boron, nitrogen, carbon, chlorine and hydrogen atoms are represented by blue, green, red, black, yellow and open circles, respectively.
Various industrial applications are conceivable. Promising prospects range from high performance turbine engines, to brake disks, combustion chamber coatings, furnace chamber coatings, and might even include fireproof or bullet-proof clothing.
Outstanding physical and chemical stability at elevated temperatures at high mechanical load for long periods of time:
- Limit for onset of decomposition pushed up to 2000°C
- Limit for loss of mechanical durability as measured by creep resistance and tensile strength pushed up to 1400°C
- Onset of crystallization and phase separation causing grain boundary sliding and crack propagation pushed up to 1900°C
- Limit of resistance to oxidation in air pushed up to 1500°C
- Specific weight as low as 1,85 g/cm3
Tunability and versatility:
- Use as ceramic fibers
- Use as ceramic coatings
- Use as ceramics matrix composites
Efficient and cheap synthesis process:
- Production from cheap single-source precursor molecular components
- Production via continous or batch-wise processing
- Production scalable to yield large quantities
The development of ceramics with outstanding physical and chemical properties has been accomplished by using chemical synthesis to design new materials at the atomic level.
The design is based on the use of cheap single-source molecular precursors that contain chemical links with the desired properties. These properties can be preserved in the synthesis process by first preparing pre-ceramic polymer intermediates from the precursor molecules. These polymers feature a homogeneous distribution of the molecular components, thereby preventing phase separation and crystallization during pyrolysis.
The ceramic material obtained from the polymer after pyrolysis is made up of a strongly bonded three-dimensional network made up of silicon, boron, nitrogen, and carbon. The randomness of the network, together with its high degree of connectivity and the strength of the involved covalent bonds is the origin of the ceramics’ superior mechanical and thermo-physical stability.
A range of process and material variants have been developed and tested allowing to adapt and optimize the production process and the obtained ceramic according to specific needs.
Comprehensive patent portfolio covering the ceramic materials, their molecular precursors, their polymer intermediates, and their production process.
M. Jansen, B. Jäschke, and T. Jäschke: „Amorphous Multinary Ceramics in the Si-B-N-C System“, Structure and Bonding, High Performance Non-Oxide Ceramics I, Vol. 101, 137-191 (2002).
Photos: Thomas Hartmann Fotodesign, K. Dobberke for Fraunhofer ISC, Max Planck Institute for Solid State Research