Mechanical Behavior of Carbon Nanotube Forests Grown With Plasma Enhanced Chemical Vapor Deposition: Pristine and Conformally Coated
Mechanical Behavior of Carbon Nanotube Forests Grown With Plasma Enhanced Chemical Vapor Deposition: Pristine and Conformally Coated
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DOI：
10.1115/1.4035622
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发表时间：
2017-07-01
影响因子：
1.2
通讯作者：
Cola, Baratunde A.
中科院分区：
文献类型：
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作者：
Abadi, Parisa Pour Shahid Saeed;Maschmann, Matthew R.;Cola, Baratunde A.
等离子体增强化学气相沉积 (PECVD) 是一种众所周知的合成碳纳米管 (CNT) 森林的方法，等离子体鞘中的电场负责 CNT 的垂直取向。在这里，我们研究了原始和保形涂层 PECVD CNT 森林在压缩载荷下的变形机制和机械性能。我们的原位压痕实验表明，局部弯曲沿着原始碳纳米管的高度形成，从尖端的起点向下延伸。对于使用原子层沉积 (ALD) 从根部到顶部涂有氧化铝的 CNT 森林，变形机制很大程度上取决于涂层厚度。当涂层厚度为 5 nm 时，屈曲行为不会发生显着变化。然而，对于 10 纳米厚的涂层，纳米管会在 CNT 核心和氧化铝涂层处断裂。使用平冲头进行的异位压痕实验表明，5 纳米和 10 纳米涂层的刚度分别增加了 8 倍和 22 倍。将 PECVD 森林与热化学气相沉积 (CVD) 生长的 CNT 的行为进行比较表明，PECVD CNT 的机械行为取决于其由包括等离子体在内的生长参数引起的特征形态。我们的研究结果可以作为针对各种应用定制碳纳米管结构特性的指南，在这些应用中碳纳米管顺应性或变形起着关键作用。
Plasma-enhanced chemical vapor deposition (PECVD) is a wellknown method for the synthesis of carbon nanotube (CNT) forests with the electric field in the plasma sheath being responsible for the vertical orientation of CNTs. Here, we investigate the deformation mechanism and mechanical properties of pristine and conformally coated PECVD CNT forests under compressive loading. Our in situ indentation experiments reveal that local buckles form along the height of pristine CNTs progressing downward from the starting point at the tips. For CNT forests coated from their roots to top with alumina using atomic layer deposition (ALD), the deformation mechanism depends strongly on the coating thickness. The buckling behavior does not change significantly when the coating is 5-nm thick. However, with a 10-nm-thick coating, the nanotubes fracture-that is, at both the CNT core and alumina coating. Ex situ indentation experiments with a flat punch reveal 8- and 22-fold increase in stiffness with the 5- and 10-nm coating, respectively. Comparing the behavior of the PECVD forests with CNTs grown with thermal chemical vapor deposition (CVD) shows that the mechanical behavior of PECVD CNTs depends on their characteristic morphology caused by the growth parameters including plasma. Our findings could serve as guidelines for tailoring the properties of CNT structures for various applications in which CNT compliance or deformation plays a critical role.