Abstract The ability to produce homogeneous defect-free carbon nanotubes (CNTs) represents a major challenge in terms of utility and cost. Specifically, the existence of grain boundaries (GBs) are ubiquitous in large diameter CNTs obtained by various large-scale growth methods and their effects on the mechanical properties of CNTs are not fully explored. Understanding the influence of the grain size and the GB orientation upon the mechanical behavior of CNTs is crucial for their functional and structural applications. The significance and novelty of the current work lies in its ability to establish the mechanical properties and the fracture behavior of CNTs containing grain boundaries of varied size, orientation and structure to an applied uniaxial load using comprehensive molecular dynamics simulations. A specially developed program, using Voronoi tessellation method and Delaunay triangulation, was implemented to generate the atomistic descriptions of the considered polycrystalline CNTs with a variety of GB morphology. Our results reveal that the mechanical performance of CNTs is significantly affected by the orientations of the GBs, diameter and temperature. In terms of the fracture strength, the resulting failure patterns indicate that the polycrystalline CNTs fail in a brittle fashion and that pentagon-heptagon defects along the GBs serve as crack nucleation sites.

中文翻译：

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解开晶界对多晶碳纳米管力学性能的影响

摘要 生产均质无缺陷碳纳米管 (CNT) 的能力代表了效用和成本方面的主要挑战。具体而言，晶界（GBs）的存在在通过各种大规模生长方法获得的大直径碳纳米管中无处不在，并且它们对碳纳米管机械性能的影响尚未得到充分探索。了解晶粒尺寸和 GB 取向对 CNT 机械行为的影响对其功能和结构应用至关重要。当前工作的重要性和新颖性在于它能够使用综合分子动力学模拟来确定包含不同尺寸、取向和结构的晶界的碳纳米管在施加的单轴载荷下的机械性能和断裂行为。专门开发的程序，使用 Voronoi 镶嵌方法和 Delaunay 三角剖分，实施以生成具有各种 GB 形态的所考虑多晶 CNT 的原子描述。我们的结果表明，碳纳米管的机械性能受 GB 的取向、直径和温度的显着影响。在断裂强度方面，由此产生的失效模式表明多晶碳纳米管以脆性方式失效，并且沿 GB 的五边形-七边形缺陷作为裂纹成核点。直径和温度。在断裂强度方面，由此产生的失效模式表明多晶碳纳米管以脆性方式失效，并且沿 GB 的五边形-七边形缺陷作为裂纹成核点。直径和温度。在断裂强度方面，由此产生的失效模式表明多晶碳纳米管以脆性方式失效，并且沿 GB 的五边形-七边形缺陷作为裂纹成核点。