Reaction sequences and influence factors during carbothermal synthesis of ultrafine TiN powders

Ultrafine TiN powders were synthesized by Carbothermal Reduction-Nitridation (CRN) method using nano titania and nano carbon black as raw materials. Phase transition sequences during reaction and influence of main technological factors were investigated using X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). The results indicate that phase transition sequences were TiO₂→Ti₁₀O₁₉→Ti₃O₅→TiO_xN_y→TiN. At the same time, CRN reaction consists of three continuous stages. In the first stage, nano TiO₂ powders were reduced to Ti₃O₅. In the second stage, Ti₃O₅ was totally converted into TiO_xN_y. TiN solid solution formed completely by the end of the third stage. The rapidest reaction rate was observed in the second stage and the lowest was in the third stage. Higher reaction temperature, longer isothermal time, or larger nitrogen pressure was in favor of synthesizing TiN powders.