纳米镍粉体的晶格膨胀

Lattice expansion of Ni nanopowders

采用阳极弧放电等离子体技术成功制备了各种不同晶粒尺寸的纳米镍粉体材料,并利用X射线衍射(XRD)、透射电子显微镜(TEM)和相应选区电子衍射(SAED)等测试手段对所制备的样品的晶体结构、晶格参数、形貌、粒度进行性能表征.实验结果表明:阳极弧等离子体法制备的镍纳米粉的晶体结构与相应的块物质相同,为fcc结构的晶态.不同晶粒尺寸的纳米镍粉体的晶格常数均大于完整单晶镍的晶格常数,晶格畸变表现为晶格膨胀.晶格常数和晶胞体积随着晶粒尺寸的减小而增大,晶格畸变量与晶粒尺寸的倒数成正比.镍纳米粉体的晶格膨胀主要是由于受到表面能和表面张力的作用而引起的,可以利用纳米晶体的热力学理论作定性解释.

Ni nanopowders with various grain sizes were successfully prepared by anodic arc discharging plasma method. The samples were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM） and the corresponding selected-area electron diffraction （SAED） to determine the crystal structure, lattice parameter, morphology and particle size. The experiment results indicate that the samples have fcc crystal structure as the bulk materials. The lattice parameter of Ni nanopowders is always larger than the equilibrium value of the perfect single crystal lattice, so the lattice expansion has taken place. The lattice parameter and the value of the unit cell volume increase significantly with the decrease of the grain size, and the increase in lattice parameter is inversely proportional to the grain size. The lattice expansion is the result of the interfacial energy and surface tension induced mutual attraction of Ni grains, and this phenomenon can be explained according to the thermodynamic theory.