Abstract:
The fabrication of alumium oxycarbides by the carbothermal reduction at 1300−1500 ℃ was investigated in flowing argon of 0.1 L/min at micro positive pressure (+15 kPa). The results indicated that Al
4O
4C took form at 1400 ℃ when α-alumina and graphite were used as raw materials, and decreased at the temperature up to 1500 ℃ might being attributed its decomposition. When the α-alumina, graphite and aluminum mixtures were used as raw materials, Al
4O
4C took form at 1300 ℃, demonstrating that the addition of aluminum significantly decreased the onset temperature for the formation of Al
4O
4C. After the raw materials of α-alumina, aluminum and graphite with a molar ratio of 4∶4∶3 were heated at 1500 ℃ for 60 min, Al
2O
3 was almost used up, and Al
4O
4C products with a little Al
4C
3 were generated. When the raw materials of α-alumina, aluminum and graphite with a ratio of 1∶4∶3 were heated at 1500 ℃ for 60 min, Al
4C
3 was primary product, and Al
4O
4C was not found. Therefore increasing the proportion of Al and decreasing that of Al
2O
3 in the raw material might result in the increasing of Al
4C
3 in the products. The optimum conditions were as follows: after heating at 1500 ℃ for 60 min, the raw materials of α-alumina, aluminum and graphite with a molar ratio of 4∶4∶3 would completely transform into the Al
4O
4C products with a little Al
4C
3, and after heating at 1500 ℃ for 90 min, the Al
4O
4C products with a little Al
2O
3 were produced and the Al
4C
3 disappeared in the products. Only Al
4O
4C formed in this process, and no trace of Al
2OC could be found at any raw materials ratio.