Reaction sequences and influence factors during preparation of Ti(C,N) powders

Ultrafine Ti(C,N) powders were prepared by carbothermal reduction-nitridation (CRN) approaches from homogeneous mixtures of nano-TiO2 and nano-carbon black. Phase evolution sequences during reaction and influence of main technological parameters were investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show phase evolution sequences consist of three continuous stages. The first stage ends with the formation of lower oxide Ti2O3 or Ti3O5. Ti2O3 is converted into cubic Ti(C,N,O), or Ti3O5 is converted into cubic Ti(N,O) during the second stage. A single Ti(C,N) phase is formed in the third stage. Ti(C,N) powders with higher carbon content can be synthesized if reaction temperature is elevated or isothermal treatment time is extended; Ti(C,N) powders with higher nitrogen content can be produced while remaining carbon also can be found in the products, if nitrogen pressure increases. Reaction temperature is the most significant factor that determines its grain growth among all the factors.