金属镍结晶生长对Ni/C微颗粒镍镀层均匀性的影响

摘要

采用湿式加压氢还原技术研究不同包覆阶段、不同氢气分压对球形石墨颗粒表面金属镍镀层镀覆均匀性的影响,探讨制备具有致密光滑镀层的Ni/C颗粒的条件及形成机理.结果表明:当气体总压为4 MPa,其中氢气分压为65%时,得到的Ni/C颗粒具有比较致密均匀的镀覆状态;镍镀层的最终形貌由镍晶体形核和生长的动力学过程决定;非均相形核过程有利于形成均匀镀层,均相形核和晶体生长都会使镀层的均匀性降低;通过调节反应速率,可以控制金属镍的结晶过程,实现均匀镀覆.%The effects of different coating stages and partial pressures of hydrogen on the coating uniformity of spherical Ni/C composite particles were studied by pressurized hydrogen reduction.The preparation condition and formation mechanism of Ni/C particles with compact and smooth coatings were investigated.The results show that the ideal coating effect is achieved when the initial pressure of hydrogen occupied 65％ of 4MPa initial total pressure.Final coating morphology of Ni/C particles is decided by dynamics of nucleation and growth processes of nickel crystal.Heterogeneous nucleation process is favorable for producing uniform coating, while the homogeneous nucleation and crystal growth processes make the coating uniformity worse.