Hydrolysis of zirconium nitrides and carbides

The hydrolytic reactions of zirconium mononitride and monocarbide by superheated steam have been studied. In the case of ZrN the products were found to be H2, N2 and NH3, with a small amount of NO. The amount of NH3 reached a maximum at 700°C in isothermal reactions and at higher temperatures NH3 was gradually replaced by N2. Compared with the hydrolysis of TiN, it is characterized by the formation of a larger amount of NH3, probably due to the lower reaction temperature for ZrN. The reaction mechanism of ZrN can be represented by an equation similar to that of TiN.By the hydrolysis of ZrC, CO2, CO, H2 and a small amount of CH4 were produced. The amount of CO2 Was maximum at 700°C and more CO was evolved with increasing temperature. X-ray analysis revealed that the hydrolyzed product consisted of metastable tetragonal ZrO2 at temperatures lower than 700°C and monoclinic ZrO2 at temperatures higher than 800°C. The reaction equation for the hydrolysis of ZrC was also estimated. CO2 was found to be produced accompanying equal moles of H2 at the later stage of the hydrolysis of ZrC as in the case of TiC. The supposition made for the case of TiC that the formation of CO2 and H2 in nearly equal moles could be attributed to the steam gas reaction involving CO in the solid residue was confirmed by the measurement of weight loss after re-hydrolysis and by X-ray diffraction technique. The amount of CO contained in the solid residue was larger than that for TiC.