The formation of toxic Cr6＋ compounds form chrome compounds are promoted in an oxidation atmosphere below 1273K under the existence in alkaline and/or CaO component, and further even in the case of elevate temperature under the coexistence with Al2O3. In this paper, the precipitation and inhibition of Cr6＋ compound were studied in the CaO-Cr2O3-Al2O3 system. The mass ratio of CaO/Cr2O3/Al2O3 components and CaO/Cr2O3/Al2O3/ Additive components were adjusted to 1/3/0 - 1/3/3 and 1/3/1/1, respectively. V2O3, SiO2, Ca（PO3）2, SnO2 and ZrO2 were selected as additives. Ca4Al6Cr（6＋）O16 identified in all the CaO-Cr2O3-Al2O3 system at 1723K. On the other hand, the precipitation of Cr6+ compounds were inhibited by addition of V2O3, SiO2, Ca（PO3）2 and SnO2.

View full abstract

The mechanical strength of MgO-C brick which incorporated MgO supported carbon nanofibers （CNF-MgO composite） was investigated by the three-point bending test. The results show that the strength of the brick increased with increasing the CNF-MgO composite content. Especially when the CNF-MgO composite content was 6mass%, the strength was high about 2.2 times compared to the material without the CNF-MgO composite. In addition, combinational effects of adding the CNF-MgO composite with aluminum and pitch were also investigated. As a result, the strength was remarkably improved by the addition of the CNF-MgO composite with aluminum and the effect of pitch addition on the lowering the modulus of elasticity was maintained when the CNF-MgO composite added in the MgO-C brick. The SEM image of specimen shows that the CNFs with net-like structure existed in the matrix of the MgO-C brick. The mechanism of strength improvement was suggested that it caused by crack arresting effect of the CNFs in MgO-C bricks.

View full abstract