Synthesis of ZrN powders by aluminum-reduction nitridation of ZrO2 powders with CaCO3 additive

Abstract ZrN powders were synthesized from mixtures of ZrO 2 and Al metal powders using CaCaO 3 as an additive. The effects of various heating temperatures, nitrogen pressures and amounts of CaCO 3 additive on the phase assemblage and morphologies of the final products were investigated using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Impurity contents and particle sizes of the final powders were measured by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), oxygen gas analysis, Energy Dispersive Spectroscopy (EDS) and ImageJ software. The results show that without adding CaCO 3 , the products were mostly composed of ZrN and ZrAl 3 O 3 N, and a small amount of other ZrO x N y phases. However, both of the ZrAl 3 O 3 N and ZrO x N y were stable in acid, and it was not possible to separate the ZrN powders. Suitable CaCO 3 concentration, heating temperature and nitrogen gas pressure were employed to avoid the formation of ZrAl 3 O 3 N and ZrO x N y and resulted in powders composed of ZrN, calcium-aluminates and calcium-zirconate phases. The by-products, calcium-aluminates and calcium-zirconate were subsequently dissolved by HCl acid to obtain single phase ZrN. The impurity elements contents are less than 2% and the mean particle size is around 0.96 µm. The optimum parameters for synthesis of ZrN were: CaCO 3 concentration of 26.83 ~29.53 wt%, heating temperature of 1400 °C and nitrogen gas pressure of 0.4 MPa.