纳米金刚石表面向洋葱碳转变的原位电镜研究

In-situ electron microscopic study of the surface transition from nanodiamond to onion like carbon

纳米金刚石向一种洋葱状石墨碳结构的转变对其性能改变显著,然而人们在研究这种始于表面的碳结构转变时却往往忽略了纳米金刚石表面不可避免会存在的非晶碳层的影响。本文借助原位环境球差电镜技术,利用电子束辐照和原位热氧化,获得了表面没有非晶碳层的纯净纳米金刚石颗粒,并证实了同样条件下表面含有非晶碳层的纳米金刚石更容易转变为洋葱碳,而表面结晶性好、不含非晶碳的纳米金刚石则更难转变为洋葱碳;此外,当电子束辐照耦合高温加热可以在更低的温度和更短的时间内将纳米金刚石全部转变为洋葱碳。本文的研究结果对抑制纳米金刚石表面石墨化转变提升其稳定性或促进纳米金刚石向洋葱碳转变并提升转变效率均具有一定的指导意义。

The surface structural transformation to onion-like graphite carbon has significantly affected the performance of nanodiamond.However,the inevitable amorphous carbon layer on the surface of nanodiamond is usually ignored.In this work,pure nanodiamond particles without surface amorphous carbon layer were obtained by electron beam irradiation and in situ thermal oxidation based on in situ ambient spherical aberration electron microscopy.The result showed that onion like carbon was easier to be formed when there existed amorphous carbon layer on the surface of nanodiamond.In contrast,onion like carbon was relatively difficult to be formed from the nanodiamond with good surface crystallinity and no amorphous carbon layer.In addition,nanodiamonds were completely transformed into the onion carbon structure at a lower temperature and in a shorter time by the synergetic effect of electron beam irradiation and high temperature heating.The result here provide a deep understanding of the inhibition of the surface graphitization transformation of nanodiamond,and also provide a method for the transformation from nanodiamond to onion like carbon structure.