Fabrication and oxidation behavior of Al4SiC4 powders
Al4SiC4 powders with high purity were synthesized by heating the powder mixture of aluminum (Al), silicon (Si), and carbon (C) at 1800°C in argon. The microstructure is characterized as platelike single grain. Both the nonisothermal and isothermal oxidation behavior of Al4SiC4 was investigated at 800°C‐1500°C in air by means of thermogravimetry method. It is demonstrated that Al4SiC4 powder possesses good oxidation resistance up to 1200°C and is almost completely oxidized at 1400°C. At 800°C‐1100°C, the oxide scales consist of an Al2O3 outer layer and a transition layer. Al4SiC4 remains the main phase. At 1200°C, some spallation resulting from the increment of Al2O3 and the mismatch of thermal expansion coefficient between different product layers can be observed. Above 1300°C, the oxide layer is composed of two part, i.e., large‐scale Al2O3 crystals (outer layer) and mullite with less amount of SiO2 (inner layer). The oxidation behavior changes due to the different oxide products. For the reaction kinetics, a new kind of real physical picture model is adopted and obtains a good agreement with the experimental data. The apparent activation energy is calculated to be 176.9 kJ/mol (800°C‐1100°C) and 267.1 kJ/mol (1300°C‐1400°C).
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