We report an atomic structure and property tailoring method that enables precise control of the diameter of individual double-walled carbon nanotubes (DWNTs), as well as the corresponding tuning of their tensile strength and electrical resistance. As demonstrated in a transmission electron microscope (TEM), this facile method involves the electron irradiation of DWNTs, followed by a thermal annealing process. The former process is responsible for the random atom loss and tube size reduction, whereas the latter allows for a complete structural recovery of defective nanotubes. The regarded DWNTs thus experience repeated disorder-order structural transitions, leading to the stepwise shrinkage in tube size, until the desired diameter is reached. Accordingly, these disorder-order transitions allow individual DWNTs to be controllably weakened and then strengthened, accompanied with the reversible changes in their breaking modes, as revealed by direct in-situ tensile tests. Differently, the resistance tuning of DWNTs upon irradiation/annealing does not follow the same trend, but depends significantly on the initial tube electrical characteristics and subsequent chirality transitions. These experimental results, combined with first-principles calculations, suggest that the change of tube chirality involved in the disorder-order transitions profoundly influences DWNT transport properties, but has a little impact on their mechanical strength.

中文翻译：

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透射电子显微镜下双壁碳纳米管的直径、强度和电阻调整

我们报告了一种原子结构和属性定制方法，该方法能够精确控制单个双壁碳纳米管 (DWNT) 的直径，以及相应调整它们的拉伸强度和电阻。正如在透射电子显微镜 (TEM) 中所证明的那样，这种简便的方法涉及对 DWNT 进行电子照射，然后进行热退火过程。前一个过程负责随机原子损失和管尺寸减小，而后者允许有缺陷的纳米管的完全结构恢复。因此，所考虑的 DWNT 经历了重复的无序结构转变，导致管尺寸逐步收缩，直到达到所需的直径。因此，正如直接原位拉伸试验所揭示的那样，这些无序有序转变允许单个 DWNT 可控地减弱然后增强，伴随着其断裂模式的可逆变化。不同的是，辐射/退火后 DWNT 的电阻调整不遵循相同的趋势，但在很大程度上取决于初始管电特性和随后的手性转变。这些实验结果与第一性原理计算相结合，表明无序有序转变中管手性的变化深刻影响了 DWNT 传输特性，但对其机械强度影响不大。DWNTs 在辐照/退火时的电阻调整不遵循相同的趋势，但在很大程度上取决于初始管电特性和随后的手性转变。这些实验结果与第一性原理计算相结合，表明无序有序转变中管手性的变化深刻影响了 DWNT 传输特性，但对其机械强度影响不大。DWNTs 在辐照/退火时的电阻调整不遵循相同的趋势，但在很大程度上取决于初始管电特性和随后的手性转变。这些实验结果与第一性原理计算相结合，表明无序有序转变中管手性的变化深刻影响了 DWNT 传输特性，但对其机械强度影响不大。