反应球磨钛与尿素制备氮化钛的反应机理研究

将Ti粉与尿素在室温下进行反应球磨制备了TiN粉末，对球磨不同时间后的粉末进行XRD分析，采用TG-FTIR技术分析了尿素的分解温度与产物，利用TEM及EELS观察和分析了球磨70h粉末的微观形貌、结构及成分. 结果发现，球磨70h合成了纳米TiN粉末，晶粒度为6~7nm，Ti/N原子比约为1.0∶0.6. 经800℃，5h真空退火处理后粉末的XRD谱图表明粉末组成为单相TiN. 在反应球磨过程中，Ti与尿素的分解产物NH₃与HNCO发生反应形成TiN，随球磨时间延长，Ti的缺陷能增大、活性增加，N在Ti中的扩散激活能减小，在球磨作用下N的扩散距离变短，TiN的含量逐渐增加形成晶核并逐渐长大形成纳米晶.

Study on Reaction Mechanism of Reactive Ball Milling of Ti with Urea to Prepare TiN Powder

Titanium nitride (TiN) powders were synthesized by reactive ball milling titanium (Ti) and urea at room temperature. The structure of the as-synthesized powders were analyzed by XRD, the urea decomposed temperature and the decomposed products were characterized by TG-FTIR, the morphology and the microstructure were observed by TEM and the component of the powders were analyzed by EELS. The powders milled for 70h were annealed at 800℃ in vacuum for 5h. The results show that TiN powders with grain size of 6-7nm can be synthesized by reactive ball milling Ti and urea for 70h. The XRD patterns of the annealed powders prove that the powders are single phase of TiN. In the milling progress, titanium reacts with the decomposed products of urea, ammonia gas (NH₃) and cyanic acid (HNCO) to form TiN. With the milling time increasing, the activity and the defect energy of titanium increase, so the diffusion activation energy for nitrogen diffusing in titanium decreases. The diffusion distance also decreases because the new TiN layer between Ti and nitrogen can be brought by milling. With the content of TiN increasing, the nucleus of TiN are formed which grow to nano-crystalline.