Abstract: The Gibbs energy values of O’-Sialon and X phase were calculated by the thermodynamic quasi-paraboloid
rule, and the process of synthesizing O’-Sialon, β-Sialon and X phase was analyzed thermodynamically. The effects of technological factors (such as amount of reducing agent added, nitriding temperature etc.)
on the synthesis of O’-Sialon based on coal gangue by the reduction-nitridation method were investigated. The results show that the use of metallic Si powder as reducing agent is more effective in prompting
O’-Sialon formation. About 80% O’-Sialon content may be attained, and the increase in nitriding temperature is advantageous to the synthesis of O’-Sialon.

Key words: O' -Sialon, coal gangue, reduction-nitridation, thermodynamic, synthesis