电子束辐照下单壁碳纳米管的结构不稳定性

Structural instabilities of single-walled carbon nanotubes under electron beam irradiation

利用透射电镜(TEM)原位观察了一端固定一端自由和两端固定的单壁碳纳米管(SWNT(s))在电子束辐照下的结构不稳定性。研究发现,一端固定一端自由的SWNT优先轴向和径向收缩后颈缩,最后形成一个个碳笼紧密相连的收缩结构("碳笼-碳笼"结构);两端固定的SWNT仅径向收缩后颈缩,最后形成许多碳笼相连的类似结构。此外,后者在电子束辐照下断开后又会重新粘合起来,表现出很强的表面塑性流变或湿润效应。这些电子束辐照诱导SWNTs非热激活结构不稳定性现象可以用我们最近提出的表面纳米曲率效应和能量束超快诱导软模和点阵失稳进行全新、全面、正确的解释。

Structural instabilities of single - walled carbon nanotubes （SWNTs） of two typical settings, which are respectively fixed at only one end and at both ends, were investigated under electron beam irradiation by our developed in - situ transmission electron microscopy observation technique. It was observed that the tube fixed only at one end preferentially shrunk in axis direction first, then shrunk and necked in diameter, and finally formed a carbon cage -like strand structure at the tube free end whereas the tube fixed at both ends merely shrunk and necked in diameter with the similar formation of carbon cage - like strand structure. It is especially intriguing that the necked carbon cage - like strand structure in the latter case was able to re -fuse after breaking and thus demonstrated a strong wetting ability and an amazing athermal plastic flow on the surface of the SWNT fixed at both ends under the electron beam irradiation at room temperature. The above athermal structural instabilities of SWNTs as induced by electron beam irradiation can be well accounted for by the completely new concepts of the surface nanocurvature and ultrafast energetic beaminduced soft mode and lattice instability as we recently proposed.