The Relevance of Carbon in Ceramics

Reference Presenter Authors
14-034 Markus Braun Braun, M.(RÜTGERS Germany GmbH); Boenigk, W.(RÜTGERS Germany GmbH); Carbon is the fourth most abundant chemical element in our solar system, most of it inaccessible in the sun. Diamond, graphite and fullerene are best known allotropes of carbon and address the users’ interest due to unique properties. They are generated under drastic conditions do not melt and thus cannot glue particles to form a ceramic structure. Therefore industrial processes make use of precursor molecules like thermoset resins creating 3D-structures or polycyclic aromatic hydrocarbons ending in 2D-graphitic layers for creating carbon bonded refractories or carbon ceramics. Graphitic carbon (natural or synthetic graphite or carbon black) protects after liquid coating and subsequent carbonisation of the glue the ceramic matrix from slag penetration. The different modes of action are presented pointing out differences. Development trends focus on reducing the use of hazardous materials maintaining the technical performance or even allowing new property combinations. High-tech applications require unusual or even conflicting characteristics. The versatility of the carbon world allows addressing niche markets with specific requirements. Protecting microgranular graphite from electrolyte erosion in Li-Ion batteries is one example. The accessible graphite surface is reduced by carbon coating followed by high-temperature ceramic conversion. This measure increases the lifetime of Li-batteries. An initial niche market can grow with e-mobility getting popular. Functional ceramic carbon can go beyond the additive status in refractories. Sinteractive carbon can be converted to isotropic high-strength carbon/graphite ceramics. The electrical conductivity is used for furnace heating elements. Carbon crucibles can be used for inductive melting of metals. Carbon pistons are successfully tested in combustion engines. In some cases the handicap “price” is delaying introduction. Carbon in ceramics will stay a continuous challenge for process designers.
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