Pore Structure, Permeability, and Alkali Attack Resistance of Al^sub 2^O3-C Refractories

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2014-06, Vol.45 (6), p.2885
• Main Authors: Xu, Yibiao, Sang, Shaobai, Li, Yawei, Ren, Bo, Zhao, Lei, Li, Yuanbing, Li, Shujing
• Format: Article
• Language: English
• Subjects: Alkalies; Metallurgy; Permeability
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-014-2217-1

Al^sub 2^O3-C refractories were first fabricated in a coke bed at 1673 K (1400 °C) using tabular corundum, reactive alumina, carbon black, silicon, and microsilica as the starting materials and phenol resin as the binder. Then the alkali attack resistance of those materials was conducted in the powder mixture of carbon black and potassium carbonate (1:1 wt pct) in a graphite crucible at 1273 K (1000 °C) for 10 hours. The correlation between pore size, permeability of Al^sub 2^O3-C refractories, and their alkali (K^sub 2^CO3) attack was investigated by means of mercury intrusion porosimetry, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results showed that the pore structure of Al^sub 2^O3-C refractories was controlled by the addition of silicon, ultrafine reactive alumina, and microsilica to in-situ form SiC whiskers and mullite in the preparation process. The mean pore size of Al^sub 2^O3-C refractories was strongly associated with permeability. With the decrease of the mean pore size, the permeability of the Al^sub 2^O3-C refractories reduced constantly. The alkali attack test also verified that the Al^sub 2^O3-C refractories with lower permeability had better alkali corrosion resistance, because the penetration of K vapor into the materials could be restricted effectively. The corrosion mechanism of Al^sub 2^O3-C refractories supposes that (1) K^sub 2^CO3 was reduced to K vapor and penetrated into the specimen through the open pores and (2) K vapor reacted with SiC, SiO2, and alumina to form KAlSi^sub 2^O^sub 6^ and KAlSiO^sub 4^, which is in agreement with the thermodynamic prediction.[PUBLICATION ABSTRACT]