Effect of Si powder-supported catalyst on the microstructure and properties of Si3N4-MgO-C refractories

Si3N4-MgO-C refractories were prepared using fused magnesia, flake graphite, and Si powder-supported Fe(NO3)(3)center dot 9H(2)O as the raw materials and phenolic resin as the binder under the flow of N-2. The effect of different nitriding temperatures on the morphology and production of Si3N4 in the uncatalyzed refractories was investigated. The effect of the morphology of beta-Si3N4 on the properties of the refractories with different catalyst contents was investigated. The oxidation resistance of the refractories was also investigated. The results showed that the increase in the nitriding temperature was beneficial for the formation of beta-Si3N4 in the refractories. However, very high nitriding temperatures generated a large number of pores in the refractories and deteriorated their properties. The refractory with 1 wt% catalyst exhibited good mechanical properties and oxidation resistance. However, the addition of excessive catalyst inhibited the formation of beta-Si3N4 and deteriorated the performance of the refractories. (C) 2019 Elsevier Ltd. All rights reserved.