Synthesis and oxidation of Zr3Al3C5 powders
Predominantly single phase Zr 3 Al 3 C 5 powders were synthesized in an Ar atmosphere using Zr-Al intermetallics and graphite as starting materials. The reaction path of Zr 3 Al 3 C 5 synthesis was discussed based on differential scanning calorimetry and X-ray diffraction results. Lattice parameters of Zr 3 Al 3 C 5 determined using the Rietveld method are a = 3.347 A and c = 27.642 A. In addition, the oxidation of Zr 3 Al 3 C 5 powders was tested by using thermogravimetry-differential scanning calorimetry. The starting and complete oxidation temperatures are 400 °C and 1200°C, respectively. These temperatures are much higher than those for ZrC, suggesting that Zr 3 Al 3 C 5 has better oxidation resistance than ZrC. On the other hand, the oxidation degree of Zr 3 Al 3 C 5 , defined for the complete carbide-oxide transformation, overshot 100% during oxidation. This overshooting is attributed to the formation of amorphous carbon. The phase evolution during the oxidation of Zr 3 Al 3 C 5 was also investigated.