The effects of partial pressure of CO on the phase behaviour of synthesised Ti(C, N) through carbothermal reduction-nitridation at 1,380oC

Abstract

The effects of partial pressure of CO (PCO) on the product phases formed through titanium dioxide (TiO2) carbothermal reduction and nitridation were studied. Electrode graphite and anatase TiO2 were used as the raw materials, while the reaction was carried out under a flowing nitrogen gas atmosphere at 1,380°C. The effects of PCO on the phase compositions, chemical compositions and microstructures of the nitridation products were investigated by adjusting the PCO in the system. The chemical mineral compositions, and microstructures of the products were characterised via scanning electron microscopy, energy-dispersive spectroscopy and x-ray diffraction. The results demonstrate that the product phases are mainly titanium nitride (TiN)0.96 and residual graphite when the PCO is at 0.003 atm. As the value of PCO reached 0.08 atm in the furnace, a phase of Ti(O0.91, C0.53, N0.32) gradually began to form, while when the CO content in the atmosphere was over 0.12 atm, a phase of Ti(C0.2, N0.8) could be observed in the products. With the increase of PCO in the system, the evolution sequence of the reaction products was found to be TiO2→TiN→Ti(O, C, N)→Ti(C, N). By controlling the partial pressure, the synthesised temperature of titanium carbonitride (Ti[C, N]) can be significantly reduced, and the manipulation of the TiN and Ti(C, N) can be effectively realised, which could provide new ideas for experiments closely related to the partial pressure of gases.