Influence of Technological Parameters on Carbothermal Reduction and Nitridation of Zircon

摘要

Carbothermal reduction and nitridation (CRN) of zircon may lead to different oxide-nitride composite materials such as ZrO_2-Si_2N_2O, ZrN-Si_3N_4, etc. The effect of technological parameters in terms of reaction temperature, carbon proportion and reaction atmosphere on the reaction rate and product phase composition after CRN of zircon was investigated by TGA and XRD. Reaction temperature has decisive effect on reaction rate and product phase composition. In the case of carbon proportion above 20%, the zircon and m-ZrO_2 contents decrease with increasing temperature, while the Zr_7N_8O_4 content increases firstly and then decreases and the ZrN content increases continually. Carbon proportion affects the yielded reaction products; the higher the carbon proportion, the lower the starting temperature for the CRN to occur. Reaction atmosphere influences also on product phase composition. In nitrogen atmosphere, the main products of sample A30 after reacted at 1500 °C consist of ZrN and Si_2N_2O; in argon atmosphere, the main products include m-ZrO_2, ZrC and SiC, while in carbon embedded atmosphere, the main products are m-ZrO_2 and Si_2N_2O.