The Formation Mechanism of Titanium-Based Transition Metal Nitride Nanoparticles Synthesized by Radio Frequency Induction Thermal Plasma

This study presents the successful synthesis of titanium-based transition metal nitride nanoparticles (Ti-Me-N, Me = Ta, Nb, Zr, Cr) using the radio frequency induction thermal plasma method. The mixture of microsized powders of Ti and Ta, Nb, Cr, or ZrN was vaporized in an Ar-NH₃ plasma environment to form Ti-Me-N nanoparticles. The synthesized nanoparticles were crystallized in a cubic rock salt structure, exhibiting a uniform cubic shape and significant agglomeration. Particle sizes were averaged 8-17 nm across the different systems, with Ti and Me elements distributed evenly. The Ti/Me-N bonds in the XPS results also confirmed the successful synthesis of the Ti-Me-N nanoparticles. The formation mechanisms were proposed as a hypothetical model based on thermodynamic analysis and experimental observations. Nanoparticles form rapidly through nucleation, condensation, and coagulation within a high-temperature field characterized by a steep gradient. Nitridation occurs as metal vapors interact with ammonia decomposition products. Model results suggest a possible trend in nucleation behavior, where Ta, Nb, and Zr may supersaturate before Ti, while Ti may nucleate before Cr. This controlled synthesis approach demonstrates the feasibility of the radio frequency induction thermal plasma method for scalable production of high-melting-point Ti-Me-N nanoparticles.