Synthesis of hexagonal plate-like Al4Si2C5 and the effect of Al4Si2C5 addition to Al2O3-C refractory

- Al4Si2C5 were synthesized for the first time via a carbothermal reduction process.
- The mechanism responsible for the Al4Si2C5 formation was established.
- Al4Si2C5 started to oxidize from about 750 °C when heated in air.
- Al4Si2C5 was considered a promising additive for Al2O3-C bricks.

Hexagonal plate-like Al4Si2C5 particles were synthesized for the first time via a carbothermal reduction process with controlled heating temperature and raw materials ratio, and their oxidation behavior was investigated. Al4O4C, Al2OC, SiC and Al4SiC4 formed as intermediate products when the batch mixture was heated in argon atmosphere, and Al4Si2C5 then formed at above 1800 °C. Possible reaction mechanisms responsible for the formation of this ternary carbide were discussed based on the reactions at the initial and later stages of the carbothermal reduction process. Al4Si2C5 added to the Al2O3-C refractory initially reacts with CO to form Al2O3, SiO2 and C. After the reaction, Al2O3 react with SiO2 to form mullite on the surfaces of the refractories, which inhibit the oxidation of the refractories.

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