Chemistry of Al metal additions during thermal treatment of calcium aluminate/graphite mixtures

The oxidation resistance of carbon-containing refractories has been known to improve with metal additions. Determination of the fundamental mechanisms by which these metal additives accomplish this goal in magnesia-carbon bricks has been extensively investigated, but very little research has been conducted on metal additions to other carbon-containing refractory systems. This study investigates the reactions of Al and C additions to a mixture of calcium aluminate cements and alumina. Graphite does not seem to influence the formation of CaO 2Al2O3 and CaO 6Al2O3. Al additions to the calcium aluminate/graphite matrix do not seem to influence the formation of CaO 2Al2O3 in argon, but these metal additions appear to raise the temperature of formation of CaO 6Al2O3 from 1400°C to 1500°C. Whiskers formed in the matrix of samples containing Al additions after exposure at 1400°C to argon, and these whiskers may inhibit the formation of CaO 6Al2O3. Different sources of cement, SECAR 71, SECAR 80, and CA-25, do not appear to significantly alter the chemistry of the phases formed from thermal treatment --Abstract, page 1