Improvement of oxidation resistance in graphite forMgO-C refractory through surface modification
(1. School of Materials Engineering, Changwon National University, Changwon, Gyeongnam 641-773, Korea;
2. Technical Research Laboratories Pohang Research Laboratory, Steelmaking Research Group,
POSCO, Phohang, Gyeongbuk 790-300, Korea;
3. High Temperature Materials Research Group, Korea Institute of Materials Science,
Changwon, Gyeongnam 641-831, Korea)
2. Technical Research Laboratories Pohang Research Laboratory, Steelmaking Research Group,
POSCO, Phohang, Gyeongbuk 790-300, Korea;
3. High Temperature Materials Research Group, Korea Institute of Materials Science,
Changwon, Gyeongnam 641-831, Korea)
Abstract: Graphite, used as a carbon source in a conventional magnesia-carbon (MgO-C) refractory, was modified with an acid reagent, resulting in a negative charge on the surface of graphite, to enhance the coating efficiency of aluminum (Al) phase, which was compared to the pristine graphite through its dispersibity and oxidation behavior. The graphite particles with and without surface modification were added, respecticely, in an Al(NO3)3 suspension used as a coating reagent, and then filtered at room temperature. The modified graphite shows better disperbility than the pristine graphite, indicating that the coating efficiency of Al precursor is enhanced in the modified graphite. With respect to oxidation behavior, the modified graphite without the coating layer is totally reacted with oxygen at heat treatment of 900 °C in air. However, the Al-coated graphite starts to react with oxygen at heat treatment of 900 °C and fully reacted with oxygen at heat treatment of 1000 °C, showing the gray and white colors, respectively. It is verified that the Al layer is individually and uniformly formed on the surface of graphite and the oxidation resistance of graphite is enhanced owing to the increased coating efficiency of Al precursor.
Key words: refractory; graphite; surface modification; aluminum; coating