高能机械化学法制备超微氮化钼粉体

在室温下通过自行设计的高能机械化学球磨机,使钼粉在NH3气氛下经过高能球磨得到超微氮化钼粉体.分别利用X射线衍射仪、扫描电镜和透射电镜对制得的粉体结构和粒度进行分析.结果表明,在球料质量比为8∶1的情况下经过30 h球磨,得到了FCC结构的Mo2N粉体,粉体平均粒度在100 nm以内.机械化学反应过程中,一方面,NH3分子在清洁的钼金属表面的化学吸附起着重要的作用,为球磨过程中由于介质球碰撞所产生的储存于钼粉中的能量(界面能和缺陷能)提供了Mo-N化学吸附向氮化钼转变所需的激活能.另一方面,钼粉晶粒细化改变了Mo原子表面电子的不饱和性,从而促进了Mo与N的键合作用.在Mo与NH3的高能机械化学反应过程中,球磨转速的高低对整个反应的速度起决定性作用.

Preparing ultramicro molybdenum nitride powders by high-energy mechanochemistry method

Using a mechanochemistry ball mill equipment specifically designed by the authors,the ultramicro molybdenum nitride powders were prepared by high-energy ball milling technology in ammonia atmosphere at room temperature.The structure and the particle size of the powders were investigated by X-ray Diffraction,Scanning Electronic Microscope and Transmission Electronic Microscope.The results show that with the grinding media to powder mass ratio being 8:1 and after 30 h of milling,the Mo2N of FCC structure were obtained,and the average particle size of the podwers was within 100 nm.It is found that the chemisorption of ammonia onto the fresh molybdenum surfaces created by milling was the dominated processes govering solid-gas reaction,and the energy inputed from the cumulative energy of grain-boundaries and lattice defects offered the activation energy for the transition from Mo-N chemisorption to molybdenum nitride.In addition,the change of Mo electronic undersaturation accelerated the bonding between Mo and N.During the high-engergy ball milling processing,the rotational speed of milling played a critical role in the reaction speed.