Carbon bonded alumina and magnesia refractories are widely used in various sectors of steel production. Examples are linings made from Al2O3-C and metal melt filters on the base of MgO-C. Recent investigations have shown that the addition of minor amounts of nanoscale materials can improve the performance of refractories. Especially the thermal shock resistance of Al2O3-C could be increased by a combination of different factors as the mixing technology, the curing temperature, the addition of doped silicon and the addition of nanoparticles. One effect of the nanoparticles is the formation of homogeneously distributed SiC-nano-whiskers. These whiskers could be analyzed by EBSD using fracture surfaces without further preparation. The hexagonal ?-SiC and cubic ?-SiC structures are coexisting. Regarding the MgO-C-system metal melt filter foams were investigated. As could be shown by EBSD secondary MgO had been formed in contact with molten steel in the form of layers and nano-whiskers. As a result the oxygen concentration of the corresponding steel melt had been reduced remarkably. The corresponding reaction mechanisms for the formation of whiskers are discussed.
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