Synthesis of ZrW ₂ O ₈ –ZrC composite powders by solid‐state exothermic oxidation reaction of ZrC and WO ₃ powders

Abstract In this work, ZrW 2 O 8 ‐coated ZrC composite powders are synthesized by solid‐state reaction method using ZrC and WO 3 powders. Thermodynamic analysis shows that when the molar ratio of ZrC to WO 3 is larger than 5:4, ZrW 2 O 8 cannot be synthesized by solid reaction of ZrC and WO 3 . The favorable molar ratio of ZrC to WO 3 for solid reaction synthesis ZrW 2 O 8 is 1:2. After reacted below 800°C for 8 hours, only ZrC in the ZrC and WO 3 mixture powders partially reacts with oxygen to form ZrO 2 . And there is no detectable reaction between WO 3 and the formed ZrO 2 to produce ZrW 2 O 8 . ZrC and WO 3 can synthesize ZrW 2 O 8 at 900°C. ZrW 2 O 8 ‐coated ZrC composite powders can be synthesized using powder mixtures with molar ratio of ZrC:WO 3 = 1:1.7 and ZrC:WO 3 = 1:1.9 after heat treatment at 1000°C for 4 hours. The synthesized ZrW 2 O 8 ‐coated ZrC particles show cubic shape with obvious particles growth. The exothermic oxidation reaction of ZrC leads to a significant increase in local temperature, which is believed to trigger partial reaction between ZrO 2 and WO 3 to form ZrW 2 O 8 .